Tandem fusogens and related lipid particles

Abstract

Provided herein are lipid particles containing at least two attachment proteins derived from a paramyxovirus envelope attachment protein and at least one paramyxovirus fusion (F) protein. Also provided are lipid particles are viral vectors, such as lentiviral vectors or lentiviral-like particles. Also provided are producer cells and compositions containing such lipid particles and methods of making and using the lipid particles.

Description

186152009440 TANDEM FUSOGENS AND RELATED LIPID PARTICLES Cross-reference to related applications

[0001] This application claims priority to U.S. Provisional Patent Application No.63 / 468,525 filed on May 23, 2023, entitled “Tandem Fusogens and Related Lipid Particles”, U.S. Provisional Patent Application No.63 / 522,722 filed on June 22, 2023, entitled “Tandem Fusogens and Related Lipid Particles”, U.S. Provisional Patent Application No. 63 / 539,547 filed on September 20, 2023, entitled “Tandem Fusogens and Related Lipid Particles”, U.S. Provisional Patent Application No.63 / 592,151 filed on October 20, 2023, entitled “Tandem Fusogens and Related Lipid Particles”, each of which are hereby incorporated by reference in its entirety. Reference to an electronic sequence listing

[0002] The present application is being filed along with a Sequence Listing in electronic format. The Sequence Listing is provided as a file entitled 18615_2009440.XML created May 22, 2024, 2024 which is 1,090,341 bytes in size. The information in the electronic format of the Sequence Listing is incorporated by reference in its entirety. Field

[0003] The present disclosure relates to lipid particles containing at least one attachment protein derived from a paramyxovirus envelope attachment protein and at least one paramyxovirus fusion (F) protein. In some embodiments, the attachment protein is retargeted, such as with two or more targeting moieties. In some embodiments, the lipid particles are viral vectors, such as lentiviral vectors or lentiviral-like particles. Also provided are producer cells and compositions containing such lipid particles and methods of making and using the lipid particles. Background

[0004] Lipid particles, including viral-based particles like virus-like particles and viral vectors such as lentiviral particles, are commonly used for delivery of exogenous agents to cells. For various particles, such as lentiviral vector particles, the host range can be altered by pseudotyping with at least one retargeted attachment protein that is or comprises two or more targeting moieties. The efficient preparation and production of particles with certain retargeted pseudotyped envelope proteins to produce 1 sf-5966708186152009440 a higher titer and with efficient transduction efficiency of target cells are needed. The provided disclosure addresses this need. Summary

[0005] Provided herein is a lipid particle, comprising: (a) a retargeted attachment protein comprising a paramyxovirus envelope attachment protein linked to (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell; and (b) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), and (b) are exposed on the outside of the lipid bilayer.

[0006] In some of any of the provided embodiments, the paramyxovirus attachment protein is a variant paramyxovirus envelope attachment protein comprising one or more mutations to reduce native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations. In some of any of the provided embodiments, the paramyxovirus envelope attachment protein is a first paramyxovirus envelope attachment protein and the lipid particle further comprises a second paramyxovirus envelope attachment protein, wherein the second paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein comprising one or more mutations to reduce native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations, wherein the second paramyxovirus envelope attachment protein is exposed on the outside of the lipid bilayer. In some of any of the provided embodiments, the targeting one or both of the first target molecule and the second target molecule does not activate or inhibit, induce a phenotype change (for example maturation and / or differentiation), induce proliferation, and / or induce apoptosis of said target cell.

[0007] Provided herein is a lipid particle, comprising: (a) a retargeted attachment protein comprising a first paramyxovirus envelope attachment protein operably linked to (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell, (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more mutations to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations; and (c) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer. Provided herein is a lipid particle, comprising: (a) a retargeted attachment protein comprising a first paramyxovirus envelope attachment protein operably linked to (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell, (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one 2 sf-5966708186152009440 or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations; and (c) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer.

[0008] In some of any of the provided embodiments, the first paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein. In some of any of the provided embodiments, the variant paramyxovirus envelope attachment protein comprises one or more mutations that reduces native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations. In some of any of the provided embodiments, the first and second paramyxovirus envelope attachment protein are the same. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein is not linked or fused to a non-viral heterologous moiety that is a cell-specific targeting domain or functional domain. In some of any of the provided embodiments, the first and second targeting moiety are each not selected from the group consisting of a cytokine, growth factor, hormone, neurotransmitter, apoptosis ligand and their combinations.

[0009] In some of any of the provided embodiments, targeting one or both of the first target molecule and the second target molecule does not modulate or induce a signal in the target cell. In some of any of the provided embodiments, the first and second targeting moieties each bind to a cell surface molecule present on a target cell. In some of any of the provided embodiments, the first targeting moiety binds to a cell surface molecule present on a first target cell, and the second targeting moiety binds a surface molecule present on a second target cell. In some of any of the provided embodiments, the first and second target molecule are different target molecules. In some of any of the provided embodiments, the first and second target molecule are the same target molecule. In some of any of the provided embodiments, the first and second targeting moiety bind distinct epitopes of the same target molecule.

[0010] In some of any of the provided embodiments, the cell surface molecule is a protein, glycan, or lipid. In some of any of the provided embodiments, the target cell is selected from the group consisting of tumor-infiltrating lymphocytes, T cells, neoplastic or tumor cells, virus-infected cells, stem cells, central nervous system (CNS) cells, hematopoietic stem cells (HSCs), and liver cells. In some of any of the provided embodiments, the target cells is selected from the group consisting of a CD3+ T cell, a CD4+ T cell, a CD8+ T cell, a hepatocyte, a hematopoietic stem cell, a CD34+ hematopoietic stem cell, a CD105+ hematopoietic stem cell, a CD117+ hematopoietic stem cell, a CD105+ endothelial cell, a B cell, a CD20+ B cell, a CD19+ B cell, a cancer cell, a CD133+ cancer cell, an EpCAM+ cancer cell, a CD19+ cancer cell, a Her2 / Neu+ cancer cell, a GluA2+ neuron, a GluA4+ neuron, a NKG2D+ natural killer cell, a SLC1A3+ astrocyte, a SLC7A10+ adipocyte, or a CD30+ lung epithelial cell. In some of any of the provided embodiments, the target cell is a hepatocyte. In some of any of the provided embodiments, the cell surface molecule is selected from the group consisting of CD34, CD117, and 3 sf-5966708186152009440 CD133. In some of any of the provided embodiments, the target cell is a T cell. In some of any of the provided embodiments, the cell surface molecule is selected from the group consisting of CD3, CD4, CD7 CD8, ASCT2, CD105, CD110, CD117, CD133, CD146, CD164, CD34, CD46, CD49f, CD90, EPCR, and ITGA3.

[0011] In some of any of the provided embodiments. the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1.

[0012] Provided herein is a lipid particle, comprising: (a) a first retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first targeting moiety directed to CD133; and a second targeting moiety directed to CD133; and (b) at least one paramyxovirus fusion (F) protein; and the protein in (a), and (b) are exposed on the outside of the lipid bilayer.

[0013] In some of any of the provided embodiments, (i) the first targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 516, 525, 534, 543, and 552, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (ii) the second targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 516, 525, 534, 543, and 552, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

[0014] In some of any of the provided embodiments, (i) the first targeting moiety comprises: (a) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 536, 537, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 545, 546, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 518, 519, and 520, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 527, 528, and 529, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; or (e) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 554, 555, and 556, respectively, and a CDR-L1, a CDR-L2, and a 4 sf-5966708186152009440 CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively; and / or (ii) the second targeting moiety comprises: (a) a CD133 binding agent comprising a CDR- H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 536, 537, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 545, 546, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 518, 519, and 520, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 527, 528, and 529, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; or (e) a CD133 binding agent comprising a CDR- H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 554, 555, and 556, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively.

[0015] In some of any of the provided embodiments, (i) the first targeting moiety comprises: (a) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 289, 565, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 566, 567, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 568, 569, and 520, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 570, 571, and 529, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; or (e) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 572, 573, and 556, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively; and / or (ii) the second targeting moiety comprises: (a) a CD133 binding agent comprising a CDR- H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 289, 565, and 5 sf-5966708186152009440 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 566, 567, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 568, 569, and 520, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 570, 571, and 529, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; or (e) a CD133 binding agent comprising a CDR- H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 572, 573, and 556, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively.

[0016] In some of any of the provided embodiments, (i) the first targeting moiety comprises: (a) a CD133 binding agent comprising a heavy chain variable (VH) region comprising the amino acid sequence of SEQ ID NO: 535, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a light chain variable (VL) region comprising the amino acid sequence of SEQ ID NO: 539, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (b) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 544, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 548, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (c) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 517, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 521, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (d) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 526, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 530, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; or (e) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 553, or an amino acid sequence having at least 6 sf-5966708186152009440 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 557, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (ii) the second targeting moiety comprises: (a) a CD133 binding agent comprising a heavy chain variable (VH) region comprising the amino acid sequence of SEQ ID NO: 535, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a light chain variable (VL) region comprising the amino acid sequence of SEQ ID NO: 539, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (b) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 544, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 548, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (c) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 517, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 521, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (d) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 526, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 530, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; or (e) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 553, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 557, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

[0017] In some of any of the provided embodiments, (a) the first targeting moiety comprises a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 517, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and (b) the second targeting moiety comprises a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 526, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto. In some of any of the provided embodiments, (a) the first targeting moiety comprises a CD133 binding agent comprising a VH region comprising the amino acid sequence of 7 sf-5966708186152009440 SEQ ID NO: 526, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and (b) the second targeting moiety comprises a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 517, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto. In some of any of the provided embodiments, wherein the first and second targeting moiety bind to distinct epitopes on CD133.

[0018] In some of any of the provided embodiments, the lipid particle further comprises a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1.

[0019] Provided herein is a lipid particle, comprising: (a) a first retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first targeting moiety directed to CD117; and a second targeting moiety directed to CD117; and (b) at least one paramyxovirus fusion (F) protein; and the protein in (a), (b) are exposed on the outside of the lipid bilayer.

[0020] In some of any of the provided embodiments, (a) the first targeting moiety comprises a CD117 binding agent comprising a VHH single domain antibody comprising a CDR-H1, a CDR- H2, and a CDR-H3 contained within an amino acid sequence selected from the group consisting of SEQ ID NOs: 512-515; and / or wherein (b) the second targeting moiety comprises a CD117 binding agent comprising a VHH single domain antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 contained within an amino acid sequence selected from the group consisting of SEQ ID NOs: 512- 515. In some of any of the provided embodiments, (a) the first targeting moiety comprising a VHH single domain antibody comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 512-515, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (b) ) the second targeting moiety comprising a VHH single domain antibody comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 512-515, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto. In some of any of the provided embodiments, (a) the first targeting moiety comprises a VHH comprising the amino acid sequence set forth in any one of SEQ ID NOS: 512-515; and / or (b) the second targeting moiety comprises a VHH comprising the amino acid sequence set forth in any one of SEQ ID NOS: 512- 8 sf-5966708186152009440 515. In some of any of the provided embodiments, the first and second targeting moiety bind to distinct epitopes on CD117.

[0021] In some of any of the provided embodiments, the lipid particle further comprises a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1.

[0022] Provided herein is a lipid particle, comprising: (a) a first retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first targeting moiety directed to CD8; and a second targeting moiety directed to CD8; and (b) at least one paramyxovirus fusion (F) protein; and the protein in (a), and (b) are exposed on the outside of the lipid bilayer.

[0023] In some of any of the provided embodiments, (i) the first targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 489, 496, 501, or 508 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (ii) the second targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 489, 496, 501, or 508, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto. In some of any of the provided embodiments, (a) the first targeting moiety comprises a CD8 binding agent comprising a VHH single domain antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 contained within an amino acid sequence of SEQ ID NO: 377; and / or wherein (b) the second targeting moiety comprises a CD8 binding agent comprising a VHH single domain antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 contained within an amino acid sequence of SEQ ID NO: 377. In some of any of the provided embodiments, (a) the first targeting moiety comprises a VHH comprising the amino acid sequence set forth in SEQ ID NOS: 377; and / or (b) the second targeting moiety comprises a VHH comprising the amino acid sequence set forth in SEQ ID NO: 377. In some of any of the provided embodiments, the first targeting moiety comprises a VHH comprising the amino acid sequence set forth in SEQ ID NO: 377 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or the second targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NO: 501 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence 9 sf-5966708186152009440 identity thereto. In some of any of the provided embodiments, the first targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NO: 501 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and the second targeting moiety comprises a VHH comprising the amino acid sequence set forth in SEQ ID NO: 377 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

[0024] In some of any of the provided embodiments, the first and second targeting moiety bind to distinct epitopes on CD8.

[0025] In some of any of the provided embodiments, the lipid particle further comprising a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more mutations that reduces the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations. In some of any of the provided embodiments, the distinct epitopes are non-overlapping. In some of any of the provided embodiments, the first and second targeting moiety bind to the distinct epitopes in a non-competitive manner.

[0026] In some of any of the provided embodiments, each of the first targeting moiety and the second targeting moiety are independently selected from the group consisting of an antibody or antigen- binding fragment, a DARPin, an Aptamer, an Affimer, an Affibody, a Knottin, an Avimer, a Monobody, an Anticalin, a Fynomer, and a targeting peptide. In some of any of the provided embodiments, the first targeting moiety and the second targeting moiety are independently selected from the group consisting of a single domain antibody or a single chain variable fragment (scFv).

[0027] Provided herein is a lipid particle comprising a) a retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first and second targeting moiety directed to CD133, (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more mutations that reduces the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations; and (c) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer.

[0028] Provided herein is a lipid particle comprising (a) a retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first and second targeting moiety directed to CD117, (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more mutations that reduces the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations; and (c) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer. 10 sf-5966708186152009440

[0029] Provided herein is a lipid particle comprising (a) a retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first and second targeting moiety directed to CD8, (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more mutations that reduces the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations; and (c) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer.

[0030] In some of any of the provided embodiments, the first paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein. In some of any of the provided embodiments, the variant paramyxovirus envelope attachment protein comprises one or more mutations that reduces native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein. In some of any of the provided embodiments, the variant paramyxovirus envelope attachment protein comprises one or more mutations that reduces native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations. In some of any of the provided embodiments, the first targeting moiety is selected from the group consisting of a single domain antibody or a single chain variable fragment (scFv). In some of any of the provided embodiments, the second targeting moiety is selected from the group consisting of a single domain antibody or a single chain variable fragment (scFv). In some of any of the provided embodiments, the single domain antibody is a VHH.

[0031] In some of any of the provided embodiments, the first variant paramyxovirus envelope attachment protein and the second variant paramyxovirus envelope attachment protein are the same. In some of any of the provided embodiments, the first paramyxovirus envelope attachment protein and the second paramyxovirus envelope attachment protein are different. In some of any of the provided embodiments, the first paramyxovirus envelope attachment protein is an envelope attachment protein from a Nipah virus, Hendra virus, or Measles virus, or is a variant or biologically active portion thereof of any of the foregoing. In some of any of the provided embodiments, the first paramyxovirus envelope attachment protein is a wild-type paramyxovirus G protein, H protein or HN protein or is a variant or biologically active portion of any of the foregoing. In some of any of the provided embodiments, the first paramyxovirus envelope attachment protein is a wild-type Nipah virus G (NiV-G) protein or is a variant or biologically active portion of a NiV-G.

[0032] In some of any of the provided embodiments, the first paramyxovirus envelope attachment protein is a variant NiV-G that is a variant or a biologically active portion of a wild-type NiV-G. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein is an 11 sf-5966708186152009440 envelope attachment protein from a Nipah virus, Hendra virus, or Measles virus, or is a variant or biologically active portion of any of the foregoing. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein is a wild-type paramyxovirus G protein, H protein or HN protein or is a variant or biologically active portion of any of the foregoing. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein is a wild-type Nipah virus G (NiV-G) protein or is a variant or a biologically active portion of a NiV-G. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein is a variant NiV-G that is a variant or a biologically active portion of a wild-type NiV-G. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein is a variant paramyxovirus envelope glycoprotein from a Nipah virus, Hendra virus, or Measles virus or a biologically active portion thereof. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein is a variant of a wild-type paramyxovirus G protein, H protein or HN protein or a biologically active portion thereof.

[0033] In some of any of the provided embodiments, the variant is a variant NiV-G that is a variant of a wild-type Nipah virus G (NiV-G) protein or a biologically active portion thereof. In some of any of the provided embodiments, the variant NiV-G is truncated by up to 40 contiguous amino acids at or near the N-terminus of the wild-type NiV-G set forth in SEQ ID NO:1. In some of any of the provided embodiments, the variant NiV-G has a truncation of amino acids 2-34 of the wild-type NiV-G set forth in SEQ ID NO:1. In some of any of the provided embodiments, the variant NiV-G exhibits reduced binding to Ephrin B2 or Ephrin B3. In some of any of the provided embodiments, the variant NiV-G comprises: one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1. In some of any of the provided embodiments, the variant NiV-G comprises amino acid substitutions E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1. In some of any of the provided embodiments, the variant NiV-G has the amino acid sequence set forth in SEQ ID NO: 228 or an amino acid sequence having at or about 80%, at least at or about 81 %, at least at or about 82%, at least at or about 83%, at or about 84%, at least at or about 85%, at least at or about 86%, or at least at or about 87%, at least at or about 88%, or at least at or about 89%, at least at or about 90%, at least at or about 91 %, at least at or about 92%, at least at or about 93%, at least at or about 94%, at least at or about 95%, at or about 96%, at least at or about 97%, at least at or about 98%, or at least at or about 99% sequence identity to SEQ ID NO:228. In some of any of the provided embodiments, the variant NiV-G has the amino acid sequence set forth in SEQ ID NO:228. In some of any of the provided embodiments, the at least one paramyxovirus fusion (F) protein is an F protein from a henipavirus or is a biologically active portion thereof or variant thereof. 12 sf-5966708186152009440

[0034] In some of any of the provided embodiments, the henipavirus is a Hendra virus. In some of any of the provided embodiments, the henipavirus is a Nipah virus. In some of any of the provided embodiments, the paramyxovirus F protein is a wild-type NiV-F protein or a variant or a biologically active portion thereof. In some of any of the provided embodiments, the paramyxovirus F protein is a variant NiV-F that is a variant or a biologically active portion of a wild-type NiV-F protein. In some of any of the provided embodiments, the variant NiV-F is truncated by up to22 contiguous amino acids the at the C-terminus of the wild-type NiV-F set forth in SEQ ID NO:235, optionally not include the initial methionine. In some of any of the provided embodiments, the variant NiV-F protein is a truncated NiV-F that lacks amino acids 525-546 of SEQ ID NO:235. In some of any of the provided embodiments, the variant NiV-F has the amino acid sequence set forth in SEQ ID NO: 227 or an amino acid sequence having at or about 80%, at least at or about 81%, at least at or about 82%, at least at or about 83%, at or about 84%, at least at or about 85%, at least at or about 86%, or at least at or about 87%, at least at or about 88%, or at least at or about 89%, at least at or about 90%, at least at or about 91%, at least at or about 92%, at least at or about 93%, at least at or about 94%, at least at or about 95%, at or about 96%, at least at or about 97%, at least at or about 98%, or at least at or about 99% sequence identity to SEQ ID NO:227. In some of any of the provided embodiments, the variant NiV-F has the amino acid sequence set forth in SEQ ID NO:227.

[0035] In some of any of the provided embodiments, the paramyxovirus F protein is an F0 precursor or is a proteolytically cleaved form thereof comprising F1 and F2 subunits. In some of any of the provided embodiments, the proteolytically cleaved form is a cathepsin L cleavage product. In some of any of the provided embodiments, the paramyxovirus envelope attachment protein and the first targeting moiety and second targeting moiety are linked via one or more linkers.

[0036] In some of any of the provided embodiments, the one or more linkers are one or more peptide linker. In some of any of the provided embodiments, the retargeted attachment protein comprises in order: Paramyxovirus attachment protein – first linker – first targeting moiety – second linker – second targeting moiety.

[0037] In some of any of the provided embodiments, the first linker and second linker is independently a peptide linker. In some of any of the provided embodiments, the first linker and second linker are the same. In some of any of the provided embodiments, the first linker and second linker are different. In some of any of the provided embodiments, the peptide linker is 2 to 65 amino acids in length. In some of any of the provided embodiments, the peptide linker is a flexible linker that comprises GS, GGS, GGGGS, GGGGGS or combinations thereof. In some of any of the provided embodiments, the peptide linker is selected from: (GGS)n, wherein n is 1 to 10; (GGGGS)n, wherein n is 1 to 10; or (GGGGGS)n, wherein n is 1 to 6. In some of any of the provided embodiments, the peptide linker is selected from SEQ ID NOs: 589-592. 13 sf-5966708186152009440

[0038] In some of any of the provided embodiments, the lipid particle further comprises one or more additional paramyxovirus envelope attachment glycoproteins embedded in the lipid bilayer. In some of any of the provided embodiments, the one or more additional paramyxovirus envelope attachment glycoproteins is a retargeted attachment protein comprising a paramyxovirus envelope attachment protein and a further targeting moiety. In some of any of the provided embodiments, the at least one paramyxovirus fusion (F) protein exhibits fusogenic activity with a target cell upon binding of at least one paramyxovirus envelope attachment protein to the target molecule on the target cell.

[0039] In some of any of the provided embodiments, the lipid particle comprises a viral nucleic acid. In some of any of the provided embodiments, the viral nucleic acid comprises one or more of (e.g., all of) the following nucleic acid sequences: 5’ LTR (e.g., comprising U5 and lacking a functional U3 domain), Psi packaging element (Psi), Central polypurine tract (cPPT) / central termination sequence (CTS) (e.g. DNA flap), Poly A tail sequence, a posttranscriptional regulatory element (e.g. WPRE), a Rev response element (RRE), and 3’ LTR (e.g., comprising U5 and lacking a functional U3).

[0040] In some of any of the provided embodiments, the lipid particle is a viral vector. In some of any of the provided embodiments, that is a retroviral vector. In some of any of the provided embodiments, that is a lentiviral vector. In some of any of the provided embodiments, the lipid particle is devoid of viral genomic DNA. In some of any of the provided embodiments, the lipid particle is a viral like particle. In some of any of the provided embodiments, the lipid particle is a retroviral-like particle. In some of any of the provided embodiments, the lipid particle is a viral like particle. In some of any of the provided embodiments, the lipid particle is a lentiviral-like particle.

[0041] In some of any of the provided embodiments, the lipid particle is produced as a preparation with increased titer compared to a reference lipid particle preparation that is similarly produced but with only the first retargeted attachment protein. In some of any of the provided embodiments, the lipid particle is produced as a preparation with increased titer compared to a reference lipid particle preparation that is similarly produced but without the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more substitutions. In some of any of the provided embodiments, the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1. In some of any of the provided embodiments, the lipid particle is produced in suspension culture as a preparation with increased titer compared to a reference lipid particle preparation that is similarly produced but with only the first retargeted attachment protein. 14 sf-5966708186152009440

[0042] In some of any of the provided embodiments, the titer is increased by at or greater than 1.2- fold, 1.3-fold, 1.4-fold, 1.5-fold, 1.6-fold, 1.7-fold, 1.8-fold, 2-fold, 2.5-fold, 3-fold, 4-fold, 5-fold, 6- fold, 7-fold, 8-fold, 9-fold, 10-fold, or more.

[0043] In some of any of the provided embodiments, the lipid particle further comprises an exogenous agent for delivery to a target cell. In some of any of the provided embodiments, the exogenous agent is present in the lumen. In some of any of the provided embodiments, the exogenous agent is a protein or a nucleic acid, optionally wherein the nucleic acid is a DNA or RNA. In some of any of the provided embodiments, the exogenous agent is a nucleic acid encoding a cargo for delivery to the target cell. In some of any of the provided embodiments, the exogenous agent is or encodes a therapeutic agent, a diagnostic agent or a genome-modifying enzyme. In some of any of the provided embodiments, the exogenous agent encodes a membrane protein, optionally wherein the membrane protein is an antigen receptor for targeting cells expressed by or associated with a disease or condition. In some of any of the provided embodiments, the membrane protein is a chimeric antigen receptor (CAR). In some of any of the provided embodiments, the exogenous agent is a nucleic acid comprising a payload gene for correcting a genetic deficiency, optionally a genetic deficiency in the target cell, optionally wherein the genetic deficiency is associated with a liver cell or a hepatocyte.

[0044] In some of any of the provided embodiments, binding of the paramyxovirus envelope attachment protein or biologically active portion thereof to a target molecule expressed on the surface of a target cell mediates fusion of the particle with the target cell and delivery of the exogenous agent to the target cell. In some of any of the provided embodiments, at or greater than 10%, 20%, 30%, 40%, 50%, 60% of the target cells are delivered the exogenous agent. In some of any of the provided embodiments, delivery of the exogenous cell to the target cell is increased compared to a reference particle preparation that is similarly produced but with only a first retargeted attachment protein. In some of any of the provided embodiments, the delivery to the target cell is increased by at or greater than 1.2-fold, 1.3-fold, 1.4-fold, 1.5-fold, 1.6-fold, 1.7-fold, 1.8-fold, 2-fold, 2.5-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8- fold, 9-fold, 10-fold, or more.

[0045] Provided herein is a producer cell comprising (a) a nucleic acid encoding a retargeted attachment protein comprising a paramyxovirus envelope attachment protein linked to (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell; and (b) a nucleic acid encoding at least one paramyxovirus fusion (F) protein.

[0046] In some of any of the provided embodiments, the producer cell further comprises a nucleic acid encoding a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native 15 sf-5966708186152009440 tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions.

[0047] In some of any of the provided embodiments, the cell further comprises a viral nucleic acid(s). In some of any of the provided embodiments, the viral nucleic acid(s) are lentiviral nucleic acids. In some of any of the provided embodiments, the cell is a mammalian cell. In some of any of the provided embodiments, the producer cell is selected from the group consisting of CHO cells, BHK cells, MDCK cells, C3H 10T1 / 2 cells, FLY cells, Psi-2 cells, BOSC 23 cells, PA317 cells, WEHI cells, COS cells, BSC 1 cells, BSC 40 cells, BMT 10 cells, VERO cells, W138 cells, MRC5 cells, A549 cells, HT1080 cells, 293 cells, 293T cells, B-50 cells, 3T3 cells, NIH3T3 cells, HepG2 cells, Saos-2 cells, Huh7 cells, HeLa cells, W163 cells, 211 cells, and 211A cells. In some of any of the provided embodiments, the producer cell comprises 293T cells. In some of any of the provided embodiments, the viral nucleic acid(s) lacks one or more genes involved in viral replication. In some of any of the provided embodiments, the viral nucleic acid comprises a nucleic acid encoding a viral packaging protein selected from one or more of Gag, Pol, Rev and Tat. In some of any of the provided embodiments, the viral nucleic acid comprises: one or more of (e.g., all of) the following nucleic acid sequences: 5’ LTR (e.g., comprising U5 and lacking a functional U3 domain), Psi packaging element (Psi), Central polypurine tract (cPPT) / central termination sequence (CTS) (e.g. DNA flap), Poly A tail sequence, a posttranscriptional regulatory element (e.g. WPRE), a Rev response element (RRE), and 3’ LTR (e.g., comprising U5 and lacking a functional U3).

[0048] Provided herein is a method of making a lipid particle, comprising: a) providing a producer cell such as any of the provided producer cells; b) culturing the cell under conditions that allow for production of the lipid particle, and c) separating, enriching, or purifying the lipid particle from the cell, thereby making the lipid particle. In some of any of the provided embodiments, the lipid particle is a pseudotyped lentiviral vector.

[0049] Provided herein is a lipid particle produced by any of the provided methods. Also provided herein is a composition comprising any of the provided lipid particles and / or a plurality of any of the provided lipid particles. Provided herein is a method transducing a cell comprising contacting a cell with any of the provided lipid particles and / or compositions. Provided herein is a method of delivering an exogenous agent into a target cell comprising contacting a cell with any of the provided lipid particles and / or compositions with a target cell.

[0050] In some of any of the provided embodiments, the contacting is in vitro or ex vivo. In some of any of the provided embodiments, the contacting is in vivo in a subject.

[0051] Provided herein is a method of delivering an exogenous agent to a cell in a subject, the method comprising administering to the subject any of the provided lipid particles and / or compositions. 16 sf-5966708186152009440 In some of any of the provided embodiments, the exogenous agent is or encodes a therapeutic agent for treating a disease or condition in the subject.

[0052] Provided herein is a method of treatment, the method comprising administering to a subject any of the provided lipid particles and / or compositions. In some of any of the provided embodiments, the exogenous agent is or encodes a membrane protein, optionally a chimeric antigen receptor, for targeting an antigen associated with a disease or condition in the subject. In some of any of the provided embodiments, the exogenous agent is for use in gene therapy to correct a genetic deficiency or replaces a deficient or missing gene in the subject. In some of any of the provided embodiments, the subject is a human subject.

[0053] In some of any of the provided embodiments, the methods delivery a particle (e.g. a lentiviral particle), including a particle containing an exogenous agent, to a hematopoietic stem cell (HSC). In some of any such provided embodiments, the method further comprises administering to the subject one or more agents that stimulate mobilization of bone marrow cells from the bone marrow to the peripheral blood. In some of any of the provided embodiments, the subject has previously been administered one or more agents that stimulate mobilization of bone marrow cells from the bone marrow to the peripheral blood. In some of any of the provided embodiments, the one or more agents that stimulate mobilization are selected from the group consisting of stem cell factor (SCF), small molecule VLA-4 inhibitor BI05192, BOP (N-(benzenesulfonyl)-L-prolyl-L-0-(1-pyrrolidinylcarbonyl)tyrosine), heparin, granulocyte colony-stimulating factor (G-CSF), MGTA-145, and plerixafor (AMD3100). In some of any of the provided embodiments, the one or more agents that stimulate mobilization comprise G-CSF. In some of any of the provided embodiments, the one or more agents that stimulate mobilization comprise plerixafor. Brief Description of the Drawings

[0054] FIG.1A depicts viral vector titer for exemplary tandem CD117 VHH binders and single CD117 VHH binders. Viral titer for vector pseudotyped with a re-targeted tandem fusogen targeting CD117 and a NiV-F protein with and without an additional blinded fusogen (±Gm) are shown for both CD117-overexpressing cells (FIG.1B) and CD34+ cells (FIG.1C). FIG.1D shows primary cell transduction for exemplary tandem binders.

[0055] FIG.2 depicts transduction of CD34+ primary cells via two exemplary CD133 tandem binders.

[0056] FIGS.3A and 3B show transduction for the indicated fusogens. FIG.3A depicts transduction of SupT1 T cells via two exemplary CD8 tandem binders. FIG.3B depicts transduction of Pan-T cells comparing a single binder to a tandem binder. 17 sf-5966708186152009440

[0057] FIG.4A shows an exemplary protocol for assessing transduction efficiency in long-term humanized mice. FIG.4B shows percent transduction in bone marrow compartments using tandem fusogens.

[0058] A model study design for non-human primates is shown in FIG.5. Detailed Description

[0059] Provided herein is a lipid particle that contains a fusogen protein on the outer surface of the lipid particle that contains two or more targeting moieties (also termed “tandem fusogen”). In some embodiments, the fusogen is embedded in the lipid bilayer of the lipid particle. In some embodiments, the fusogen contains a viral envelope attachment protein that is linked to the two or more targeting moieties. In some embodiments, the at least two targeting moieties are directed against a target molecule or target molecules on the surface of a cell to thereby retarget the attachment protein to the target molecule or target molecules. In some embodiments, the viral envelope attachment protein contains a first targeting moiety directed to a first target molecule and a second targeting moiety directed to a second target molecule. In some embodiments the first and second target molecule are the same. In some embodiments, the first and second target molecule are different. In some embodiments, the attachment protein is fused to the two or more targeting moieties in which one or more peptide linkers connect the attachment protein and the two or more targeting moieties. In some embodiments, the fusogen facilitates the fusion of the lipid particle to a plasma cell membrane of one or more target cell.

[0060] In some embodiments, provided herein is a lipid particle in which a retargeted attachment protein includes at least two targeting moieties directed to a target molecule or target molecules on the surface of the cells and the lipid particle also contains a second attachment protein that is a fusion protein (F protein). In some embodiments, the fusogen is composed of a viral attachment protein comprising the two or more targeting moieties and a fusion protein (F protein) that together are a fusogen. In some embodiments, the fusogen may be derived from a paramyxovirus. In some embodiments, the viral attachment protein is a paramyxovirus envelope attachment protein, such as a G, H or HN protein, and the F protein is at least one paramyxovirus fusion (F) protein. In some embodiments, the attachment protein is a variant attachment protein containing one or more mutations (e.g. amino acid substitutions) to reduce or ablate the native tropism relative to the wild-type virus envelope attachment protein (e.g., paramyxovirus envelope attachment protein) not comprising the one or more mutations.

[0061] In some aspects, the lipid particle provided herein includes (a) a retargeted attachment protein with (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell. In some embodiments, the lipid particles, such as viral vectors or viral-like particles, contain one or more attachment proteins (e.g., fusogens). In some embodiments, the lipid 18 sf-5966708186152009440 particle, e.g. viral vector or viral-like particle, contains an exogenous or overexpressed attachment protein (e.g., fusogen). In some embodiments, the attachment protein is disposed in the lipid bilayer. In some embodiments, the attachment protein (e.g., fusogen) facilitates the fusion of the lipid particle to a membrane. In some embodiments, the membrane is a plasma cell membrane of a target cell. In some embodiments, the lipid particle, such as a viral or non-viral vector, comprising the attachment protein (e.g., fusogen) integrates into the membrane into a lipid bilayer of a target cell. In some embodiments, the attachment protein (e.g., fusogen) results in mixing between lipids in the lipid particle and lipids in the target cell. In some embodiments, the attachment protein (e.g., fusogen) results in formation of one or more pores between the interior of the non-cell particle and the cytosol of the target cell. In some embodiments, the attachment protein (e.g., fusogen) may include a non-mammalian protein, e.g., a viral protein. In some embodiments, a viral fusogen is a Class I viral membrane fusion protein, a Class II viral membrane protein, a Class III viral membrane fusion protein, a viral membrane glycoprotein, or other viral fusion proteins, or a homologue thereof, a fragment thereof, a variant thereof, or a protein fusion comprising one or more proteins or fragments thereof.

[0062] In some aspects, the lipid particle provided herein includes (a) a retargeted attachment protein comprising a paramyxovirus envelope attachment protein operably fused in tandem with (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell; and (b) a paramyxovirus fusion protein. In some embodiments, the retargeted attachment protein comprises a variant paramyxovirus envelope attachment protein comprising one or more mutations to reduce native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations.

[0063] In some of any of the embodiments, the lipid particle further contains a second viral envelope attachment protein embedded in the lipid bilayer of the lipid particle that is not attached to a targeting moiety. In some embodiments, the second viral envelope attachment protein is a paramyxovirus envelope attachment protein, such as a G, H or HN protein. In some embodiments, the first viral envelope attachment protein and the second viral envelope attachment protein are the same. In particular embodiments, the second viral envelope attachment protein is a variant paramyxovirus envelope attachment protein comprising one or more mutations to reduce native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations. a second envelope attachment protein. In such embodiments, the second viral envelope attachment protein is not linked or fused to a non-viral heterologous moiety, such as a targeting moiety.

[0064] In some aspects, the lipid particle provided herein includes (a) a retargeted attachment protein comprising a first paramyxovirus envelope attachment protein operably fused in tandem with (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a 19 sf-5966708186152009440 second targeting moiety directed to a second target molecule expressed on the surface of a target cell; (b) a second paramyxovirus envelope attachment protein; and (b) a paramyxovirus fusion protein. In some embodiments, the first and second paramyxovirus envelope attachment proteins are the same. In some embodiments, each of the first and second paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein comprising one or more mutations to reduce native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations. In such embodiments, the second paramyxovirus envelope attachment protein is not linked or fused to a non-viral heterologous moiety, such as a targeting moiety.

[0065] In some embodiments, the at least two targeting moieties, e.g., a first targeting moiety and second targeting moiety, bind a target molecule on the same target cell. In some embodiments, the at least two targeting moieties, e.g., a first targeting moiety and a second targeting moiety, are the same. In some embodiments, the at least two targeting moieties, e.g., a first targeting moiety and a second targeting moiety, are different. In some embodiments, the at least two targeting moieties, e.g., a first targeting moiety and a second targeting moiety, bind to different epitopes of the same target molecule.

[0066] In some embodiments, the at least two targeting moieties, e.g., a first targeting moiety and a second targeting moiety, bind to target molecules on the surface of different target cells.

[0067] Exemplary target cells include cells present in a blood sample from a subject. In some embodiments, the cells include a leukocyte component. In some embodiments, the target cells include polymorphonuclear cells (also known as PMN, PML, PMNL, or granulocytes), In some embodiments, the target cells include lymphocytes, monocytes, macrophages, dendritic cells, natural killer cells, T cells (e.g. CD4 or CD8 T cells including cytotoxic T lymphocytes) or B cells. In some embodiments, the target cells include hematopoietic stem cells (HSCs).

[0068] In some embodiments, the retargeted attachment protein comprises a paramyxovirus envelope attachment protein and (i) a first targeting moiety directed to a first target molecule expressed on the surface of a T cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a T cell. In some embodiments, the target molecule on a T cell is CD3, CD4 or CD8. In some embodiments, the first and second target molecule are the same. In some embodiments, the first and second target molecule is CD3. In some embodiments, the first and second target molecule is CD4. In some embodiments, the first and second target molecule is CD8. In some embodiments, the first targeting moiety and second targeting moiety are the same. In some embodiments, the first targeting moiety and second targeting moiety are different. In some embodiments, the first and second targeting moiety bind to different epitopes of the same target molecule.

[0069] In some embodiments, the retargeted attachment protein comprises a paramyxovirus envelope attachment protein and (i) a first targeting moiety directed to a first target molecule expressed on the surface of a T cell, and (ii) a second targeting moiety directed to a second target molecule 20 sf-5966708186152009440 expressed on the surface of a hematopoietic stem cell (HSC). In some embodiments, the target molecule on an HSC is CD117 or CD133. In some embodiments, the first and second target molecule are the same. In some embodiments, the first and second target molecule is CD117. In some embodiments, the first and second target molecule is CD133. In some embodiments, the first targeting moiety and second targeting moiety are the same. In some embodiments, the first targeting moiety and second targeting moiety are different. In some embodiments, the first and second targeting moiety bind to different epitopes of the same target molecule.

[0070] In some embodiments, the targeting moiety, such as each of the first targeting moiety and the second targeting moiety, are independently selected from the group consisting of an antibody or antigen- binding fragment, an engineered binding domain, a nanobody, a DARPin, an Aptamer, an Affimer, an Affibody, a Knottin, an Avimer, a Monobody, an Anticalin, a Fynomer, and a targeting peptide.

[0071] In some embodiments, any of the provided lipid particles also contains at least one paramyxovirus fusion (F) protein or a biologically active portion thereof embedded in the lipid bilayer. In some embodiments, the F protein is from a Paramyxovirus, a Henipavirus (e.g., Hendra (HeV), Nipah (NiV) virus, Cedar henipavirus (CedV), Kumasi virus (KV), Mòjiāng virus (MojV), or Langya virus), or is a biologically active portion thereof or is a variant or mutant thereof. In particular embodiments, the F protein is from a Nipah (NiV) virus.

[0072] In naturally occurring paramyxoviruses, the fusion (F) and attachment (G, H, or HN) glycoproteins mediate cellular entry of paramyxovirus, such as Nipah virus. In some embodiments, the combination of an F protein, such as a NiV-F protein, and variant NiV-G protein as provided herein is able to mediate cellular entry of a provided lipid particle (e.g. lentiviral vector).

[0073] The F protein, such as Nipah Virus F protein, also known as NiV-F, is a class I fusion protein that has structural and functional features in common with fusion proteins of many families (e.g., HIV-1 gp41 or influenza virus hemagglutinin [HA]), such as an ectodomain with a hydrophobic fusion peptide and two heptad repeat regions (White JM et al.2008. Crit Rev Biochem Mol Biol 43:189–219). F proteins are synthesized as inactive precursors F0and are activated by proteolytic cleavage into the two disulfide-linked subunits F1and F2(Moll M. et al.2004. J. Virol.78(18): 9705-9712).

[0074] In some embodiments, the lipid particle comprises a retargeted paramyxovirus envelope attachment protein comprising a G protein. G proteins are attachment proteins of henipavirus (e.g. Nipah virus or Hendra virus) that are type II transmembrane glycoproteins containing an N-terminal cytoplasmic tail, a transmembrane domain, an extracellular stalk, and a globular head (Liu, Q. et al.2015. Journal of Virology, 89(3):1838-1850). The Nipah virus attachment protein, NiV-G, recognizes the receptors EphrinB2 and EphrinB3. Binding of the receptor to NiV-G triggers a series of conformational changes that eventually lead to the triggering of NiV-F, which exposes the fusion peptide of NiV-F, allowing another series of conformational changes that lead to virus-cell membrane fusion (Stone J.A. et 21 sf-5966708186152009440 al.2016. J Virol.90(23): 10762-10773). EphrinB2 was previously identified as the primary NiV receptor (Negrete et al., 2005), as well as ephrinB3 as an alternate receptor (Negrete et al., 2006). In fact, wild- type NiV-G has a high affinity for ephrinB2 and B3, with affinity binding constants (Kd) in the picomolar range (Negrete et al., 2006) (Kd=0.06 nM and 0.58 nM for cell surface expressed ephrinB2 and B3, respectively). In some embodiments, the G protein is from a Paramyxovirus, a Henipavirus (e.g., Hendra (HeV), Nipah (NiV) virus, Cedar henipavirus (CedV), Kumasi virus (KV), Mòjiāng virus (MojV), or Langya virus), or is a biologically active portion thereof or is a variant or mutant thereof. In particular embodiments, the G protein is from a Nipah (NiV) virus.

[0075] In some embodiments, the lipid particles can be a virus-like particle, a virus, or a viral vector, such as a lentiviral vector.

[0076] In some embodiments, the retargeted paramyxovirus envelope attachment protein comprising a G protein may be further linked to at least two targeting moieties as a retargeted attachment protein to facilitate specific targeting of the lipid particle to a target molecule or target molecules for fusion with a desired target cell or desired target cells. Thus, the provided embodiments, the envelope attachment protein comprising G proteins may be re-targeted as a retargeted attachment protein to any desired cell type for specific targeting of a lipid particle (e.g. lentiviral vector) and, in some cases, specific delivery to a target cell of a transgene or heterologous protein contained therein.

[0077] Thus, also provided herein are lipid particles containing a lipid bilayer enclosing a lumen or cavity and a paramyxovirus envelope attachment protein that is retargeted with two or more targeting moieties containing an antigen binding domain or a biologically active portion thereof, such as a single domain antibody (sdAb) variable domain, in which the retargeted G glycoprotein (e.g., tandem G protein) is embedded in the lipid bilayer of the lipid particles. In particular embodiments, the binding domain is an antibody with the ability to bind, such as specifically bind, to a desired target molecule. Exemplary binding domains are described in Section II.

[0078] The efficiency of transduction of lipid particles can be improved by engineering mutations in one or both of NiV-F and NiV-G. Several such mutations have been previously described (see, e.g., Lee at al., 2011, Trends in Microbiology). This is useful, for example, for maintaining the specificity and picomolar affinity of NiV-G for ephrinB2 and / or B3. Additionally, mutations in NiV-G that completely abrogate ephrinB2 and B3 binding, but that do not impact the association of this NiV-G with NiV-F, have been identified (Aguilar, et al. J Biol Chem.2009;284(3):1628-1635.; Weise et al. J Virol. 2010;84(15):7634-764; Negrete et al.. J Virol.2007;81(19):10804-10814; Negrete et al. PLoS Pathog. 2006; Guillaume et al., J. Virol 2006, 80 (15) 7546-7554 In some cases, methods to improve targeting of lipid particles can be achieved by fusion of a binding molecule with a G protein (e.g. NiV-G, including a NiV-G with mutations to abrogate Ephrin B2 and Ephrin B3 binding). This does allow for altered G protein tropism allowing for targeting of other desired cell types that are not ephrinB2+ through the 22 sf-5966708186152009440 addition of the binding molecule directed against a different cell surface molecule. Thus, in provided aspects, a paramyxovirus envelope attachment protein is a variant NiV-G protein that may further contain a mutation to reduce or abrogate binding to Ephrin B2 and / B3. In some embodiments, the mutations can include one or more of mutations E501A, W504A, Q530A and E533A, with reference to numbering of wild-type NiV-G set forth in SEQ ID NO:1.

[0079] In some embodiments, the lipid particle (e.g. viral vector) is pseudotyped with a retargeted attachment protein which comprises a retargeted paramyxovirus attachment protein as described herein, such as a tandem NiV-G protein.

[0080] It has been reported that the henipavirus F proteins from various species exhibit compatibility with G proteins from other species to trigger fusion (Brandel-Tretheway et al. Journal of Virology.2019.93(13):e00577-19). In some aspects of the provided lipid particles (e.g. lentiviral vector), the F protein is heterologous to the G protein, i.e. the F and G protein or biologically active portions are from different henipavirus species. For example, the G protein is from Hendra virus and the F protein is a NiV-F as described. In other aspects, the F and / or G protein can be retargeted F and / or G protein containing regions of F and / or G proteins from different species of Henipavirus. In some embodiments, switching a region of amino acid residues of the F protein from one species of Henipavirus to another can result in fusion to the G protein of the species comprising the amino acid insertion. (Brandel-Tretheway et al.2019). In some cases, the chimeric F and / or G protein contains an extracellular domain from one henipavirus species and a transmembrane and / or cytoplasmic domain from a different henipavirus species. For example, the F protein contains an extracellular domain of Hendra virus and a transmembrane / cytoplasmic domain of Nipah virus.

[0081] The provided lipid particles, such as lentiviral vectors, exhibit advantages over available envelope-pseudotyped particles. For instance, VSV-G is the most common envelope glycoprotein used for pseudotyping but its broad tropism is often not ideal or desirable for specific target cell delivery, such as is desired for gene therapy or exogenous protein delivery. Further, although alternative envelope proteins may exhibit reduced tropism or may be amenable to linkage to a binding domain for redirected targeting to a desired target cell, the titer of a preparation of lentiviral vectors containing such envelope proteins may be too low to allow for efficient transduction. Thus, alternative approaches are needed. It is found herein that certain duplicate proteins when pseudotyped on a lentiviral vector exhibit high titers.

[0082] Also provided are lipid particles, such as targeted lipid particles, additionally containing one or more exogenous agents, such as for delivery of a diagnostic or therapeutic agent to cells, including following in vivo administration to a subject. Also provided herein are methods and uses of the lipid particles, such in diagnostic and therapeutic methods. Also provided are polynucleotides, methods for engineering, preparing, and producing the lipid non-cell particles, compositions containing the particles, and kits and devices containing and for using, producing and administering the particles. 23 sf-5966708186152009440

[0083] All publications, including patent documents, scientific articles and databases, referred to in this application are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication were individually incorporated by reference. If a definition set forth herein is contrary to or otherwise inconsistent with a definition set forth in the patents, applications, published applications and other publications that are herein incorporated by reference, the definition set forth herein prevails over the definition that is incorporated herein by reference.

[0084] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. DEFINITIONS

[0085] Unless defined otherwise, all terms of art, notations and other technical and scientific terms or terminology used herein are intended to have the same meaning as is commonly understood by one of ordinary skill in the art to which the claimed subject matter pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and / or for ready reference, and the inclusion of such definitions herein should not necessarily be construed to represent a substantial difference over what is generally understood in the art. Unless indicated otherwise, abbreviations and symbols for chemical and biochemical names is per IUPAC-IUB nomenclature. Unless indicated otherwise, all numerical ranges are inclusive of the values defining the range as well as all integer values in-between.

[0086] As used herein, the articles “a” and “an” refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.

[0087] As used herein, the term “about” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. As used herein, “about” when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ±20% or ±10%, more preferably ±5%, even more preferably ±1%, and still more preferably ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods.

[0088] As used herein, “lipid particle” refers to any biological or synthetic particle that contains a bilayer of amphipathic lipids enclosing a lumen or cavity. Typically a lipid particle does not contain a nucleus. Such lipid particles include, but are not limited to, viral particles (e.g. lentiviral particles), virus- like particles, viral vectors (e.g., lentiviral vectors) exosomes, enucleated cells, various vesicles, such as a microvesicle, a membrane vesicle, an extracellular membrane vesicle, a plasma membrane vesicle, a giant plasma membrane vesicle, an apoptotic body, a mitoparticle, a pyrenocyte, or a lysosome. In some embodiments, a lipid particle can be a fusosome. In some embodiments, the lipid particle is not a platelet. In some embodiments, the fusosome is derived from a source cell. A lipid particle also may 24 sf-5966708186152009440 include an exogenous agent or a nucleic acid encoding an exogenous agent, which may be present in the lumen of the lipid particle.

[0089] The terms “viral vector particle” and “viral vector” are used interchangeably herein and refer to a vector for transfer of an exogenous agent (e.g. non-viral or exogenous nucleic acid) into a recipient or target cell and that contains one or more viral structural proteins in addition to at least one non- structural viral genomic component or functional fragment thereof (i.e., a polymerase, an integrase, a protease or other non-structural component). The viral vector thus contains the exogenous agent, such as heterologous nucleic acid that includes non-viral coding sequences, to be transferred into a cell. Examples of viral vectors are retroviral vectors, such as lentiviral vectors.

[0090] The term “retroviral vector” refers to a viral vector that contains retroviral nucleic acid or is derived from a retrovirus. A retroviral vector particle includes the following components: a vector genome (retrovirus nucleic acid), a nucleocapsid encapsidating the nucleic acid, and a membrane envelope surrounding the nucleocapsid. Typically, a retroviral vector contains sufficient retroviral genetic information to allow packaging of an RNA genome, in the presence of packaging components, into a viral particle capable of infecting a target cell. Infection of the target cell may include reverse transcription and integration into the target cell genome. A retroviral vector may be a recombinant retroviral vector that is replication defective and lacks genes essential for replication, such as a functional gag-pol and / or env gene and / or other genes essential for replication. A retroviral vector also may be a self-inactivating (SIN) vector.

[0091] As used herein, a “lentiviral vector” or LV refers to a viral vector that contains lentiviral nucleic acid or is derived from a lentivirus. A lentiviral vector particle includes the following components: a vector genome (lentivirus nucleic acid), a nucleocapsid encapsidating the nucleic acid, and a membrane surrounding the nucleocapsid. Typically, a lentiviral vector contains sufficient lentiviral genetic information to allow packaging of an RNA genome, in the presence of packaging components, into a viral particle capable of infecting a target cell. Infection of the target cell may include reverse transcription and integration into the target cell genome. A lentiviral vector may be a recombinant lentiviral vector that is replication defective and lacks genes essential for replication, such as a functional gag-pol and / or env gene and / or other genes essential for replication. A lentiviral vector also may be a self-inactivating (SIN) vector.

[0092] As used herein, a “retroviral nucleic acid,” refers to a nucleic acid containing at least the minimal sequence requirements for packaging into a retroviral vector, alone or in combination with a helper cell, helper virus, or helper plasmid. In the case of “lentiviral nucleic acid” the nucleic acid refers to at least the minimal sequence requirements for packaging into a lentiviral vector, alone or in combination with a helper cell, helper virus, or helper plasmid. In some embodiments, the viral nucleic acid comprises one or more of (e.g., all of) a 5’ LTR (e.g., to promote integration), U3 (e.g., to activate 25 sf-5966708186152009440 viral genomic RNA transcription), R (e.g., a Tat-binding region), U5, a 3’ LTR (e.g., to promote integration), a packaging site (e.g., psi (Ψ)), RRE (e.g., to bind to Rev and promote nuclear export). The viral nucleic acid can comprise RNA (e.g., when part of a virion) or DNA (e.g., when being introduced into a source cell or after reverse transcription in a recipient cell). In some embodiments, the viral nucleic acid is packaged using a helper cell, helper virus, or helper plasmid which comprises one or more of (e.g., all of) gag, pol, and env.

[0093] As used herein, “fusosome” refers to a lipid particle containing a bilayer of amphipathic lipids enclosing a lumen or cavity and a fusogen that interacts with the amphipathic lipid bilayer. In some embodiments, the fusosome is a membrane enclosed preparation. In some embodiments, the fusosome is derived from a source cell. A fusosome also may include an exogenous agent or a nucleic acid encoding an exogenous agent, which may be present in the lumen of the fusosome.

[0094] As used herein, “fusosome composition” refers to a composition comprising one or more fusosomes.

[0095] As used herein, “fusogen” refers to an agent or molecule that creates an interaction between two membrane enclosed lumens. In embodiments, the fusogen facilitates fusion of the membranes. In other embodiments, the fusogen creates a connection, e.g., a pore, between two lumens (e.g., a lumen of a retroviral vector and a cytoplasm of a target cell). In some embodiments, the fusogen comprises a complex of two or more proteins, e.g., wherein neither protein has fusogenic activity alone. In some embodiments, the fusogen comprises a targeting domain. Examples of fusogens include paramyxovirus F and G proteins such as those from Nipah Virus (NiV) and biologically active portions or variants thereof including any as described.

[0096] As used herein, a “re-targeted fusogen,” such as a re-targeted G protein, refers to a fusogen that comprises a targeting moiety having a sequence that is not part of the naturally-occurring form of the fusogen in which the targeting moiety targets or binds a molecule on a desired cell type. In embodiments, the fusogen comprises a different targeting moiety relative to the targeting moiety in the naturally-occurring form of the fusogen. In embodiments, the naturally-occurring form of the fusogen lacks a targeting domain, and the re-targeted fusogen comprises a targeting moiety that is absent from the naturally-occurring form of the fusogen. In embodiments, the fusogen is modified to comprise a targeting moiety. In some such embodiments, the attachment of the targeting moiety to a fusogen (e.g. G protein) may be directly or indirectly via a linker, such as a peptide linker. In embodiments, the fusogen comprises one or more sequence alterations outside of the targeting moiety relative to the naturally- occurring form of the fusogen, e.g., in a transmembrane domain, fusogenically active domain, or cytoplasmic domain.

[0097] As used herein, a “target cell” refers to a cell of a type to which it is desired that a lipid particle, such as a targeted lipid particle, delivers an exogenous agent. In embodiments, a target cell is a 26 sf-5966708186152009440 cell of a specific tissue type or class, e.g., an immune effector cell, e.g., a T cell. In some embodiments, a target cell is a diseased cell, e.g., a cancer cell. In some embodiments, the fusogen, e.g., re-targeted fusogen leads to preferential delivery of the exogenous agent to a target cell compared to a non-target cell.

[0098] As used herein a “non-target cell” refers to a cell of a type to which it is not desired that a lipid particle delivers an exogenous agent. In some embodiments, a non-target cell is a cell of a specific tissue type or class. In some embodiments, a non-target cell is a non-diseased cell, e.g., a non-cancerous cell. In some embodiments, the fusogen, e.g., re-targeted fusogen leads to lower delivery of the exogenous agent to a non-target cell compared to a target cell.

[0099] As used herein a “biologically active portion,” such as with reference to a protein such as a G protein or an F protein, refers to a portion of the protein that exhibits or retains an activity or property of the full-length of the protein. For example, a biologically active portion of an F protein retains fusogenic activity in conjunction with the G protein when each are embedded in a lipid bilayer. A biologically active portion of the G protein retains fusogenic activity in conjunction with an F protein when each is embedded in a lipid bilayer. The retained activity can include 10%-150% or more of the activity of a full-length or wild-type F protein or G protein. Examples of biologically active portions of F and G proteins include proteins with truncations of the cytoplasmic domain, such as any of the described variant NiV-F with a truncated cytoplasmic tail.

[0100] As used herein, “percent (%) amino acid sequence identity” and “homology” with respect to a peptide, polypeptide or antibody sequence are defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the specific peptide or polypeptide sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN or MEGALIGN (DNASTAR) software. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared.

[0101] An amino acid substitution may include but are not limited to the replacement of one amino acid in a polypeptide with another amino acid. Exemplary substitutions are shown in Table 1. Amino acid substitutions may be introduced into an antibody of interest and the products screened for a desired activity, for example, retained / improved binding. 27 sf-5966708186152009440 Table 1: Exemplary substitutions Original Residue Exemplary Substitutions Ala (A) Val; Leu; Ile Arg (R) Lys; Gln; Asn Asn (N) Gln; His; Asp, Lys; Arg Asp (D) Glu; Asn Cys (C) Ser; Ala Gln (Q) Asn; Glu Glu (E) Asp; Gln Gly (G) Ala His (H) Asn; Gln; Lys; Arg Ile (I) Leu; Val; Met; Ala; Phe; Norleucine Leu (L) Norleucine; Ile; Val; Met; Ala; Phe Lys (K) Arg; Gln; Asn Met (M) Leu; Phe; Ile Phe (F) Trp; Leu; Val; Ile; Ala; Tyr Pro (P) Ala Ser (S) Thr Thr (T) Val; Ser Trp (W) Tyr; Phe Tyr (Y) Trp; Phe; Thr; Ser Val (V) Ile; Leu; Met; Phe; Ala; Norleucine

[0102] Amino acids may be grouped according to common side-chain properties: (1) hydrophobic: Norleucine, Met, Ala, Val, Leu, Ile; (2) neutral hydrophilic: Cys, Ser, Thr, Asn, Gln; (3) acidic: Asp, Glu; (4) basic: His, Lys, Arg; (5) residues that influence chain orientation: Gly, Pro; (6) aromatic: Trp, Tyr, Phe.

[0103] Non-conservative substitutions will entail exchanging a member of one of these classes for another class.

[0104] The term, “corresponding to” with reference to positions of a protein, such as recitation that nucleotides or amino acid positions “correspond to” nucleotides or amino acid positions in a disclosed sequence, such as set forth in the Sequence listing, refers to nucleotides or amino acid positions identified upon alignment with the disclosed sequence based on structural sequence alignment or using a standard alignment algorithm, such as the GAP algorithm. For example, corresponding residues of a similar sequence (e.g. fragment or species variant) can be determined by alignment to a reference sequence by structural alignment methods. By aligning the sequences, one skilled in the art can identify corresponding residues, for example, using conserved and identical amino acid residues as guides. 28 sf-5966708186152009440

[0105] The term “isolated” as used herein refers to a molecule that has been separated from at least some of the components with which it is typically found in nature or produced. For example, a polypeptide is referred to as “isolated” when it is separated from at least some of the components of the cell in which it was produced. Where a polypeptide is secreted by a cell after expression, physically separating the supernatant containing the polypeptide from the cell that produced it is considered to be “isolating” the polypeptide. Similarly, a polynucleotide is referred to as “isolated” when it is not part of the larger polynucleotide (such as, for example, genomic DNA or mitochondrial DNA, in the case of a DNA polynucleotide) in which it is typically found in nature, or is separated from at least some of the components of the cell in which it was produced, for example, in the case of an RNA polynucleotide. Thus, a DNA polynucleotide that is contained in a vector inside a host cell may be referred to as “isolated”.

[0106] The term “effective amount” as used herein means an amount of a pharmaceutical composition which is sufficient to significantly and positively modify the symptoms and / or conditions to be treated (e.g., provide a positive clinical response). The effective amount of an active ingredient for use in a pharmaceutical composition will vary with the particular condition being treated, the severity of the condition, the duration of treatment, the nature of concurrent therapy, the particular active ingredient(s) being employed, the particular pharmaceutically-acceptable excipient(s) and / or carrier(s) utilized, and like factors with the knowledge and expertise of the attending physician.

[0107] An “exogenous agent” as used herein with reference to a lipid particle, such as a viral vector, refers to an agent that is neither comprised by nor encoded in the corresponding wild-type virus or fusosome made from a corresponding wild-type source cell. In some embodiments, the exogenous agent does not naturally exist, such as a protein or nucleic acid that has a sequence that is altered (e.g., by insertion, deletion, or substitution) relative to a naturally occurring protein. In some embodiments, the exogenous agent does not naturally exist in the source cell. In some embodiments, the exogenous agent exists naturally in the source cell but is exogenous to the virus. In some embodiments, the exogenous agent does not naturally exist in the recipient cell. In some embodiments, the exogenous agent exists naturally in the recipient cell, but is not present at a desired level or at a desired time. In some embodiments, the exogenous agent comprises RNA or protein.

[0108] As used herein, a “promoter” refers to a cis- regulatory DNA sequence that, when operably linked to a gene coding sequence, drives transcription of the gene. The promoter may comprise a transcription factor binding sites. In some embodiments, a promoter works in concert with one or more enhancers which are distal to the gene.

[0109] As used herein, a composition refers to any mixture of two or more products, substances, or compounds, including cells. It may be a solution, a suspension, liquid, powder, a paste, aqueous, non- aqueous or any combination thereof. 29 sf-5966708186152009440

[0110] As used herein, the term “pharmaceutically acceptable” refers to a material, such as a carrier or diluent, which does not abrogate the biological activity or properties of the compound, and is relatively nontoxic, i.e., the material may be administered to an individual without causing undesirable biological effects or interacting in a deleterious manner with any of the components of the composition in which it is contained.

[0111] As used herein, the term “pharmaceutical composition” refers to a mixture of at least one compound of the invention with other chemical components, such as carriers, stabilizers, diluents, dispersing agents, suspending agents, thickening agents, and / or excipients. The pharmaceutical composition facilitates administration of the compound to an organism. Multiple techniques of administering a compound exist in the art including, but not limited to, intravenous, oral, aerosol, parenteral, ophthalmic, pulmonary and topical administration.

[0112] A “disease” or “disorder” as used herein refers to a condition where treatment is needed and / or desired.

[0113] As used herein, the terms “treat,” “treating,” or “treatment” refer to ameliorating a disease or disorder, e.g., slowing or arresting or reducing the development of the disease or disorder or reducing at least one of the clinical symptoms thereof. For purposes of this disclosure, ameliorating a disease or disorder can include obtaining a beneficial or desired clinical result that includes, but is not limited to, any one or more of: alleviation of one or more symptoms, diminishment of extent of disease, preventing or delaying spread (for example, metastasis, for example metastasis to the lung or to the lymph node) of disease, preventing or delaying recurrence of disease, delay or slowing of disease progression, amelioration of the disease state, inhibiting the disease or progression of the disease, inhibiting or slowing the disease or its progression, arresting its development, and remission (whether partial or total).

[0114] The terms “individual” and “subject” are used interchangeably herein to refer to an animal; for example a mammal. The term patient includes human and veterinary subjects. In some embodiments, methods of treating mammals, including, but not limited to, humans, rodents, simians, felines, canines, equines, bovines, porcines, ovines, caprines, mammalian laboratory animals, mammalian farm animals, mammalian sport animals, and mammalian pets, are provided. The subject can be male or female and can be any suitable age, including infant, juvenile, adolescent, adult, and geriatric subjects. In some examples, an “individual” or “subject” refers to an individual or subject in need of treatment for a disease or disorder. In some embodiments, the subject to receive the treatment can be a patient, designating the fact that the subject has been identified as having a disorder of relevance to the treatment, or being at adequate risk of contracting the disorder. In particular embodiments, the subject is a human, such as a human patient.

[0115] As used herein, the terms “nuclear export sequence” (NES) or “nuclear export signal” (NES) refer to a nuclear export signal or other sequence or domain that is present in a protein and capable of 30 sf-5966708186152009440 targeting the protein for export from the cell nucleus to the cytoplasm through the nuclear pore complex using nuclear transport. A nuclear export domain can be fused (e.g., fused in-frame) with a polypeptide.

[0116] As used herein, the terms “nuclear localization sequence” (NLS) or “nuclear localization sequence” (NLS) refer to a nuclear localization signal or other sequence or domain that is present in a protein and capable of targeting the protein for import from the cytoplasm to the cell nucleus through the nuclear pore complex using nuclear transport. A nuclear localization can be fused (e.g., fused in-frame) with a polypeptide. I. LIPID PARTICLES COMPRISING TANDEM FUSOGENS

[0117] In some embodiments, the lipid particles, such as viral vectors or viral-like particles, contain one or more attachment proteins (e.g., fusogens). In some embodiments, the lipid particle, e.g. viral vector or viral-like particle, contains an exogenous or overexpressed attachment protein (e.g., fusogen). In some embodiments, the fusogen is disposed in the lipid bilayer. In some embodiments, the fusogen facilitates the fusion of the lipid particle to a membrane.

[0118] In some embodiments, the lipid particle comprises an attachment protein that is retargeted, such as an attachment protein that is linked to at least two targeting moieties, such as a first and second targeting moiety.

[0119] In some embodiments, the attachment protein (e.g., fusogen) may include a non-mammalian protein, e.g., a viral protein. In some embodiments, a viral fusogen is a Class I viral membrane fusion protein, a Class II viral membrane protein, a Class III viral membrane fusion protein, a viral membrane glycoprotein, or other viral fusion proteins, or a homologue thereof, a fragment thereof, a variant thereof, or a protein fusion comprising one or more proteins or fragments thereof.

[0120] In some embodiments, Class I viral membrane fusion proteins include, but are not limited to, Baculovirus F protein, e.g., F proteins of the nucleopolyhedrovirus (NPV) genera, e.g., Spodoptera exigua MNPV (SeMNPV) F protein and Lymantria dispar MNPV (LdMNPV), and paramyxovirus F proteins.

[0121] In some embodiments, Class II viral membrane proteins include, but are not limited to, tick bone encephalitis E (TBEV E), Semliki Forest Virus E1 / E2.

[0122] In some embodiments, Class III viral membrane fusion proteins include, but are not limited to, rhabdovirus G (e.g., fusogenic protein G of the Vesicular Stomatitis Virus (VSV-G)), herpesvirus glycoprotein B (e.g., Herpes Simplex virus 1 (HSV-1) gB)), Epstein Barr Virus glycoprotein B (EBV gB), thogotovirus G, baculovirus gp64 (e.g., Autographa California multiple NPV (AcMNPV) gp64), Baboon endogenous retrovirus envelope glycoprotein (BaEV), and Borna disease virus (BDV) glycoprotein (BDV G).

[0123] Examples of other viral attachment proteins e.g., fusogens that are membrane glycoproteins and viral fusion proteins, include, but are not limited to: viral syncytia proteins such as influenza 31 sf-5966708186152009440 hemagglutinin (HA) or mutants, or fusion proteins thereof; human immunodeficiency virus type 1 envelope protein (HIV-1 ENV), gp120 from HIV binding LFA-1 to form lymphocyte syncytium, HIV gp41, HIV gp160, or HIV Trans-Activator of Transcription (TAT); viral glycoprotein VSV-G, viral glycoprotein from vesicular stomatitis virus of the Rhabdoviridae family; glycoproteins gB and gH-gL of the varicella-zoster virus (VZV); murine leukemia virus (MLV)-10A1; Gibbon Ape Leukemia Virus glycoprotein (GaLV); type G glycoproteins in Rabies, Mokola, vesicular stomatitis virus and Togaviruses; murine hepatitis virus JHM surface projection protein; porcine respiratory coronavirus spike- and membrane glycoproteins; avian infectious bronchitis spike glycoprotein and its precursor; bovine enteric coronavirus spike protein; the F and H, HN or G genes of Measles virus; canine distemper virus, Newcastle disease virus, human parainfluenza virus 3, simian virus 41, Sendai virus and human respiratory syncytial virus; gH of human herpesvirus 1 and simian varicella virus, with the chaperone protein gL; human, bovine and cercopithicine herpesvirus gB; envelope glycoproteins of Friend murine leukemia virus and Mason Pfizer monkey virus; mumps virus hemagglutinin neuraminidase, and glycoproteins F1 and F2; membrane glycoproteins from Venezuelan equine encephalomyelitis; paramyxovirus F protein; SIV gp160 protein; Ebola virus G protein; or Sendai virus fusion protein, or a homologue thereof, a fragment thereof, a variant thereof, and a protein fusion comprising one or more proteins or fragments thereof.

[0124] Non-mammalian attachment proteins (e.g., fusogens) include viral fusogens, homologues thereof, fragments thereof, and fusion proteins comprising one or more proteins or fragments thereof. Viral fusogens include class I fusogens, class II fusogens, class III fusogens, and class IV fusogens. In embodiments, class I fusogens such as human immunodeficiency virus (HIV) gp41, have a characteristic post fusion conformation with a signature trimer of α-helical hairpins with a central coiled-coil structure. Class I viral fusion proteins include proteins having a central post fusion six-helix bundle. Class I viral fusion proteins include influenza HA, parainfluenza F, HIV Env, Ebola GP, hemagglutinins from orthomyxoviruses, F proteins from paramyxoviruses (e.g. Measles, (Katoh et al. BMC Biotechnology 2010, 10:37)), ENV proteins from retroviruses, and fusogens of filoviruses and coronaviruses. In embodiments, class II viral fusogens such as dengue E glycoprotein, have a structural signature of β- sheets forming an elongated ectodomain that refolds to result in a trimer of hairpins. In embodiments, the class II viral fusogen lacks the central coiled coil. Class II viral fusogen can be found in alphaviruses (e.g., E1 protein) and flaviviruses (e.g., E glycoproteins). Class II viral fusogens include fusogens from Semliki Forest virus, Sinbis, rubella virus, and dengue virus. In embodiments, class III viral fusogens such as the vesicular stomatitis virus G glycoprotein, combine structural signatures found in classes I and II. In embodiments, a class III viral fusogen comprises α helices (e.g., forming a six-helix bundle to fold back the protein as with class I viral fusogens), and β sheets with an amphiphilic fusion peptide at its end, reminiscent of class II viral fusogens. Class III viral fusogens can be found in rhabdoviruses and 32 sf-5966708186152009440 herpesviruses. In embodiments, class IV viral fusogens are fusion-associated small transmembrane (FAST) proteins (doi:10.1038 / sj.emboj.7600767, Nesbitt, Rae L., "Targeted Intracellular Therapeutic Delivery Using Liposomes Formulated with Multifunctional FAST proteins" (2012). Electronic Thesis and Dissertation Repository. Paper 388), which are encoded by nonenveloped reoviruses. In embodiments, the class IV viral fusogens are sufficiently small that they do not form hairpins (doi: 10.1146 / annurev-cellbio-101512-122422, doi:10.1016 / j.devcel.2007.12.008).

[0125] Additional exemplary attachment proteins e.g., fusogens are disclosed in US 9,695,446, US 2004 / 0028687, US 6,416,997, US 7,329,807, US 2017 / 0112773, US 2009 / 0202622, WO 2006 / 027202, and US 2004 / 0009604, the entire contents of all of which are hereby incorporated by reference.

[0126] In some embodiments, the attachment protein (e.g., fusogen) is any of the fusogenic moieties described in WO2017 / 182585; WO2022 / 164935; WO2021 / 076788; Hamilton et al. bioRxiv 2022.08.24.505004; Nikolic et al. Nat Commun 9, 1029 (2018); Dobson et al. Nat. Methods.19, 449–460 (2022); and Yu et al. bioRxiv 2021.12.13.472464, for instance any of the VSV or variant VSV glycoproteins described therein, such as VSV glycoproteins that have reduced binding to native receptors.

[0127] In some embodiments, the attachment protein (e.g., fusogen) is a poxviridae fusogen.

[0128] In some embodiments, the lipid particle comprises an attachment protein that is a first paramyxovirus attachment protein that is retargeted, such as a paramyxovirus envelope attachment protein that is linked to at least two targeting moieties, such as a first and second targeting moiety. In some embodiments, the lipid particle further comprises at least one paramyxovirus fusion protein.

[0129] In some embodiments, the paramyxovirus envelope attachment proteins and / or retargeted attachment proteins provided herein exhibit fusogenic activity to a target cell, such as to deliver an exogenous agent or nucleic acid exogenous agent to the target cell.

[0130] In some embodiments, the paramyxovirus attachment protein is or comprises a hemagglutinin-neuraminidase (HN) from a respiratory paramyxovirus. In some embodiments, the respiratory paramyxovirus is a Sendai virus. The HN glycoproteins of Sendai viruses function to attach to sialic acids via the HN protein, and to mediate cell fusion for entry to cells via the F (fusion) protein. In some embodiments, the paramyxovirus attachment protein is or comprises a HN protein from the murine parainfluenza virus type 1 (See e.g., US Patent No.10704061).

[0131] In some embodiments, the paramyxovirus attachment protein is or comprises a Nipah virus protein G, a measles protein H, a tupaia paramyxovirus H protein, a paramyxovirus G protein, a paramyxovirus H protein, a paramyxovirus HN protein, a Morbillivirus H protein, a respirovirus HN protein, a Sendai HN protein, a rubulavirus HN protein, an avulavirus HN protein, or a derivative thereof. In some embodiments, the paramyxovirus attachment protein is or comprises a sequence chosen from Nipah virus G proteins, measles virus H proteins, tupaia paramyxovirus H proteins, paramyxovirus G 33 sf-5966708186152009440 proteins and H proteins and HN proteins, Hendra virus G proteins, Henipavirus G proteins, Morbillivirus H proteins, respirovirus HN protein, a Sendai virus HN protein, rubulavirus HN proteins, or avulavirus HN proteins, or a derivative thereof, or any combination thereof. A. Paramyxovirus Attachment Proteins

[0132] In some embodiments, the lipid particles provided herein comprise a paramyxovirus envelope attachment protein, a first paramyxovirus envelope attachment protein, and / or a second paramyxovirus envelope attachment protein. In some embodiments, the paramyxovirus attachment protein is retargeted. In some embodiments, the paramyxovirus envelope attachment protein may be an envelope glycoprotein G, H and / or HN of the Paramyxoviridae family.

[0133] In some embodiments, the lipid particles provided herein comprise a first paramyxovirus envelope attachment protein, a second paramyxovirus envelope attachment protein, and a third paramyxovirus envelope attachment protein. In some embodiments, each of the first, second, and third paramyxovirus envelope attachment protein may independently be an envelope glycoprotein G, H and / or HN of the Paramyxoviridae family.

[0134] In some embodiments, the lipid particles provided herein comprise a first paramyxovirus envelope attachment protein, a second paramyxovirus envelope attachment protein, a third paramyxovirus envelope attachment protein, and one or more additional paramyxovirus envelope attachment proteins, such as a fourth paramyxovirus envelope attachment protein, or a fourth and fifth paramyxovirus envelope attachment protein, or a fourth, fifth, and sixth paramyxovirus envelope attachment protein, or beyond. In some embodiments, each of the paramyxovirus envelope attachment proteins may independently be an envelope glycoprotein G, H and / or HN of the Paramyxoviridae family. 1. G Proteins

[0135] In some embodiments, the paramyxovirus envelope attachment protein, first paramyxovirus envelope attachment protein, and / or second paramyxovirus envelope attachment protein and / or the third paramyxovirus envelope attachment protein and / or the fourth paramyxovirus envelope attachment protein and / or the fifth paramyxovirus envelope attachment protein and / or the sixth paramyxovirus envelope attachment protein, and / or any additional paramyxovirus envelope attachment protein is an attachment glycoprotein G (G protein) or biologically active portion thereof. In some embodiment, the retargeted attachment protein comprises a first paramyxovirus envelope attachment protein G.

[0136] In some embodiments, the lipid particle comprises a retargeted attachment protein, a first retargeted attachment protein, and / or second retargeted attachment protein exposed on the surface of the targeted lipid particle. In some embodiments, the lipid particle further comprises a third retargeted attachment protein exposed on the surface of the targeted lipid particle. In some embodiments, the lipid particle further comprises a third retargeted attachment protein and a fourth retargeted attachment protein 34 sf-5966708186152009440 exposed on the surface of the targeted lipid particle. In some embodiments, the lipid particle further comprises a third retargeted attachment protein, a fourth retargeted attachment protein, and a fifth retargeted attachment protein exposed on the surface of the targeted lipid particle. In some embodiments, the lipid particle further comprises a third retargeted attachment protein, a fourth retargeted attachment protein, a fifth retargeted attachment protein, and one or more additional retargeted attachment proteins, exposed on the surface of the targeted lipid particle. In some embodiments, the retargeted attachment protein is or comprises a paramyxovirus attachment protein, wherein the paramyxovirus attachment protein is an attachment glycoprotein G (G protein) or biologically active portion thereof. In some embodiments, the retargeted attachment protein is or comprises a paramyxovirus attachment protein, wherein the paramyxovirus attachment protein is an attachment glycoprotein G (G protein) or biologically active portion thereof, and comprises a targeting moiety directed to a target molecule, e.g., a binding domain or a binding agent, expressed on the surface of a target cell.

[0137] The envelope attachment G proteins are type II transmembrane glycoproteins containing an N-terminal cytoplasmic tail (e.g. corresponding to amino acids 1-49 of SEQ ID NO:1), a transmembrane domain (e.g. corresponding to amino acids 50-70 of SEQ ID NO:1), and an extracellular domain containing an extracellular stalk (e.g. corresponding to amino acids 71-187 of SEQ ID NO:1), and a globular head (corresponding to amino acids 188-602 of SEQ ID NO:1). The N-terminal cytoplasmic domain is within the inner lumen of the lipid bilayer and the C-terminal portion is the extracellular domain that is exposed on the outside of the lipid bilayer. Regions of the stalk in the C-terminal region (e.g. corresponding to amino acids 71-187 of SEQ ID NO: 1) have been shown to be involved in interactions with F protein and triggering of F protein fusion (Liu et al.2015 J of Virology 89:1838). In wild-type G protein, the globular head mediates receptor binding to henipavirus entry receptors Ephrin B2 and Ephrin B3, but is dispensable for membrane fusion (Brandel-Tretheway et al. Journal of Virology.2019.93(13)e00577-19).

[0138] In some embodiments herein, tropism of the G protein is altered by linkage of the G protein or biologically active fragment thereof (e.g. cytoplasmic truncation) to a sdAb variable domain. Binding of the G protein to a binding partner can trigger fusion mediated by a compatible paramyxovirus fusion protein (e.g., F protein) or biologically active portion thereof (such as any of the F proteins described in II.B below). G protein sequences disclosed herein are predominantly disclosed as expressed sequences including an N-terminal methionine required for start of translation. As such N-terminal methionines are commonly cleaved co- or post-translationally, the mature protein sequences for all G protein sequences disclosed herein are also contemplated as lacking the N-terminal methionine.

[0139] G glycoproteins are highly conserved between henipavirus species. For example, the G protein of NiV and HeV viruses share 79% amino acids identity. Studies have shown a high degree of compatibility among G proteins with F proteins of different species as demonstrated by heterotypic 35 sf-5966708186152009440 fusion activation (Brandel-Tretheway et al. Journal of Virology.2019). As described, a lipid particle can contain at least two envelope attachment proteins (e.g., co-fusogens). In particular embodiments, the F protein or the functionally active variant or biologically active portion thereof retains fusogenic activity in conjunction with the at least two envelope attachment proteins (e.g., co-fusogens that are paramyxovirus attachment protein Gs) as provided, such as any set forth below. Fusogenic activity includes the activity of the paramyxovirus fusion protein (e.g., F protein) in conjunction with a G protein to promote or facilitate fusion of two membrane lumens, such as the lumen of the lipid particle provided herein (e.g. having embedded in its lipid bilayer, such as exposed on its surface, at least two G proteins and a F protein), and a cytoplasm of a target cell, e.g. a cell that contains a surface receptor or molecule that is recognized or bound by the G protein.

[0140] Exemplary Henipavirus protein G sequences are provided in Table 2 Table 2. Henipavirus protein G sequence clusters. Column 1, Genbank ID includes the Genbank ID of the whole genome sequence of the virus that is the centroid sequence of the cluster. Column 2, nucleotides of CDS provides the nucleotides corresponding to the CDS of the gene in the whole genome. Column 3, Full Gene Name, provides the full name of the gene including Genbank ID, virus species, strain, and protein name. Column 4, Sequence, provides the amino acid sequence of the gene. Column 5, #Sequences / Cluster, provides the number of sequences that cluster with this centroid sequence. Column 6 provides the SEQ ID numbers for the described sequences. Table 2: Exemplary Henipavirus protein G sequences Gen Nucleo Full sequence Sequence SEQ ban tides ID ID k ID of NO CDS AF0 8913- gb:AF017149|O MMADSKLVSLNNNLSGKIKDQGKVIKNYYGT 561 1714 10727 rganism:Hendra MDIKKINDGLLDSKILGAFNTVIALLGSIIIIVM 9 virus|Strain NIMIIQNYTRTTDNQALIKESLQSVQQQIKALT Name:UNKNO DKIGTEIGPKVSLIDTSSTITIPANIGLLGSKISQS WN- TSSINENVNDKCKFTLPPLKIHECNISCPNPLPF AF017149|Prot REYRPISQGVSDLVGLPNQICLQKTTSTILKPR ein LISYTLPINTREGVCITDPLLAVDNGFFAYSHL Name:glycoprot EKIGSCTRGIAKQRIIGVGEVLDRGDKVPSMF ein|Gene MTNVWTPPNPSTIHHCSSTYHEDFYYTLCAVS Symbol:G HVGDPILNSTSWTESLSLIRLAVRPKSDSGDYN QKYIAITKVERGKYDKVMPYGPSGIKQGDTLY FPAVGFLPRTEFQYNDSNCPIIHCKYSKAENCR LSMGVNSKSHYILRSGLLKYNLSLGGDIILQFI EIADNRLTIGSPSKIYNSLGQPVFYQASYSWDT MIKLGDVDTVDPLRVQWRNNSVISRPGQSQC PRFNVCPEVCWEGTYNDAFLIDRLNWVSAGV YLNSNQTAENPVFAVFKDNEILYQVPLAEDDT NAQKTITDCFLLENVIWCISLVEIYDTGDSVIRP KLFAVKIPAQCSES 36 sf-5966708186152009440 AF2 8943- gb:AF212302|O MPAENKKVRFENTTSDKGKIPSKVIKSYYGTM 1 1230 10751 rganism:Nipah DIKKINEGLLDSKILSAFNTVIALLGSIVIIVMNI 2 virus|Strain MIIQNYTRSTDNQAVIKDALQGIQQQIKGLAD Name:UNKNO KIGTEIGPKVSLIDTSSTITIPANIGLLGSKISQST WN- ASINENVNEKCKFTLPPLKIHECNISCPNPLPFR AF212302|Prot EYRPQTEGVSNLVGLPNNICLQKTSNQILKPKL ein ISYTLPVVGQSGTCITDPLLAMDEGYFAYSHL Name:attachme ERIGSCSRGVSKQRIIGVGEVLDRGDEVPSLFM nt TNVWTPPNPNTVYHCSAVYNNEFYYVLCAVS glycoprotein|Ge TVGDPILNSTYWSGSLMMTRLAVKPKSNGGG ne Symbol:G YNQHQLALRSIEKGRYDKVMPYGPSGIKQGD TLYFPAVGFLVRTEFKYNDSNCPITKCQYSKP ENCRLSMGIRPNSHYILRSGLLKYNLSDGENP KVVFIEISDQRLSIGSPSKIYDSLGQPVFYQASF SWDTMIKFGDVLTVNPLVVNWRNNTVISRPG QSQCPRFNTCPEICWEGVYNDAFLIDRINWISA GVFLDSNQTAENPVFTVFKDNEILYRAQLASE DTNAQKTITNCFLLKNKIWCISLVEIYDTGDN VIRPKLFAVKIPEQCT JQ00 8170- gb:JQ001776:8 MLSQLQKNYLDNSNQQGDKMNNPDKKLSVN 562 1776 10275 170- FNPLELDKGQKDLNKSYYVKNKNYNVSNLLN 10275|Organis ESLHDIKFCIYCIFSLLIIITIINIITISIVITRLKVHE m:Cedar ENNGMESPNLQSIQDSLSSLTNMINTEITPRIGI virus|Strain LVTATSVTLSSSINYVGTKTNQLVNELKDYIT Name:CG1a|Pr KSCGFKVPELKLHECNISCADPKISKSAMYST otein NAYAELAGPPKIFCKSVSKDPDFRLKQIDYVIP Name:attachme VQQDRSICMNNPLLDISDGFFTYIHYEGINSCK nt KSDSFKVLLSHGEIVDRGDYRPSLYLLSSHYH glycoprotein|Ge PYSMQVINCVPVTCNQSSFVFCHISNNTKTLD ne Symbol:G NSDYSSDEYYITYFNGIDRPKTKKIPINNMTAD NRYIHFTFSGGGGVCLGEEFIIPVTTVINTDVFT HDYCESFNCSVQTGKSLKEICSESLRSPTNSSR YNLNGIMIISQNNMTDFKIQLNGITYNKLSFGS PGRLSKTLGQVLYYQSSMSWDTYLKAGFVEK WKPFTPNWMNNTVISRPNQGNCPRYHKCPEI CYGGTYNDIAPLDLGKDMYVSVILDSDQLAE NPEITVFNSTTILYKERVSKDELNTRSTTTSCFL FLDEPWCISVLETNRFNGKSIRPEIYSYKIPKYC NC_ 9117- gb:NC_025256: MPQKTVEFINMNSPLERGVSTLSDKKTLNQSK 563 0252 11015 9117- ITKQGYFGLGSHSERNWKKQKNQNDHYMTV 56 11015|Organis STMILEILVVLGIMFNLIVLTMVYYQNDNINQR m:Bat MAELTSNITVLNLNLNQLTNKIQREIIPRITLID Paramyxovirus TATTITIPSAITYILATLTTRISELLPSINQKCEFK Eid_hel / GH- TPTLVLNDCRINCTPPLNPSDGVKMSSLATNL M74a / GHA / 20 VAHGPSPCRNFSSVPTIYYYRIPGLYNRTALDE 09|Strain RCILNPRLTISSTKFAYVHSEYDKNCTRGFKYY Name:BatPV / Ei ELMTFGEILEGPEKEPRMFSRSFYSPTNAVNY d_hel / GH- HSCTPIVTVNEGYFLCLECTSSDPLYKANLSNS M74a / GHA / 20 TFHLVILRHNKDEKIVSMPSFNLSTDQEYVQII 09|Protein PAEGGGTAESGNLYFPCIGRLLHKRVTHPLCK Name:glycoprot KSNCSRTDDESCLKSYYNQGSPQHQVVNCLIR ein|Gene IRNAQRDNPTWDVITVDLTNTYPGSRSRIFGSF Symbol:G SKPMLYQSSVSWHTLLQVAEITDLDKYQLDW 37 sf-5966708186152009440 LDTPYISRPGGSECPFGNYCPTVCWEGTYNDV YSLTPNNDLFVTVYLKSEQVAENPYFAIFSRD QILKEFPLDAWISSARTTTISCFMFNNEIWCIAA LEITRLNDDIIRPIYYSFWLPTDCRTPYPHTGK MTRVPLRSTYNY NC_ 8716- gb:NC_025352: MATNRDNTITSAEVSQEDKVKKYYGVETAEK 564 0253 11257 8716- VADSISGNKVFILMNTLLILTGAIITITLNITNLT 52 11257|Organis AAKSQQNMLKIIQDDVNAKLEMFVNLDQLVK m:Mojiang GEIKPKVSLINTAVSVSIPGQISNLQTKFLQKY virus|Strain VYLEESITKQCTCNPLSGIFPTSGPTYPPTDKPD Name:Tonggua DDTTDDDKVDTTIKPIEYPKPDGCNRTGDHFT n1|Protein MEPGANFYTVPNLGPASSNSDECYTNPSFSIGS Name:attachme SIYMFSQEIRKTDCTAGEILSIQIVLGRIVDKGQ nt QGPQASPLLVWAVPNPKIINSCAVAAGDEMG glycoprotein|Ge WVLCSVTLTAASGEPIPHMFDGFWLYKLEPDT ne Symbol:G EVVSYRITGYAYLLDKQYDSVFIGKGGGIQKG NDLYFQMYGLSRNRQSFKALCEHGSCLGTGG GGYQVLCDRAVMSFGSEESLITNAYLKVNDL ASGKPVIIGQTFPPSDSYKGSNGRMYTIGDKY GLYLAPSSWNRYLRFGITPDISVRSTTWLKSQ DPIMKILSTCTNTDRDMCPEICNTRGYQDIFPL SEDSEYYTYIGITPNNGGTKNFVAVRDSDGHI ASIDILQNYYSITSATISCFMYKDEIWCIAITEG KKQKDNPQRIYAHSYKIRQMCYNMKSATVTV GNAKNITIRRY

[0141] In some embodiments, at least one G protein has a sequence set forth in any of SEQ ID NOS: 1, 561, 562, 563, or 564 or is a functionally active variant or biologically active portion thereof that has a sequence that is at least at or about 80%, at least at or about 81%, at least at or about 82%, at least at or about 83%, at least at or about 84%, at least at or about 85%, at least at or about 86%, at least at or about 87%, at least at or about 88%, at least at or about 89%, at least at or about 90%, at least at or about 91%, at least at or about 92%, at least at or about 93%, at least at or about 94%, at least at or about 95%, at least at or about 96%, at least at or about 97%, at least at or about 98%, or at least at or about 99% identical to any one of SEQ ID NOS: 1, 561, 562, 563, or 564.

[0142] In particular embodiments, the paramyxovirus envelope attachment protein (e.g., G protein) or functionally active variant or biologically active portion is a protein that retains fusogenic activity in conjunction with a paramyxovirus fusion protein (e.g., F protein), such as a NiV-F protein described herein. Fusogenic activity includes the activity of the paramyxovirus envelope attachment protein (e.g., G protein) in conjunction with a paramyxovirus fusion protein (e.g., F protein) to promote or facilitate fusion of two membrane lumens, such as the lumen of the targeted lipid particle having embedded in its lipid bilayer a paramyxovirus fusion protein (e.g., F protein) and paramyxovirus envelope attachment protein (e.g., G protein), and a cytoplasm of a target cell, e.g. a cell that contains a surface receptor or molecule that is recognized or bound by the targeted envelope protein. In some embodiments, the paramyxovirus fusion protein (e.g., F protein) 38 sf-5966708186152009440 and the paramyxovirus envelope attachment protein (e.g., G protein) are from the same paramyxovirus species (e.g. the same Henipavirus species such as NiV-G and NiV-F).

[0143] In some embodiments, at least one G protein or the functionally active variant or biologically active portion thereof binds to Ephrin B2 or Ephrin B3. In some embodiments, the G protein is a variant G protein, such as a truncated G protein as described and retains binding to Ephrin B2 or B3. Reference to retaining binding to Ephrin B2 or B3 includes binding that is similar to the level or degree of binding of the corresponding wild-type G protein, such as set forth in SEQ ID NO: 1, 561, 562, 563, or 564, such as at least 50%, at least 60%, at least 70%, at least 80% or at least 90% of the binding of the wild-type G protein.

[0144] In some embodiments, the paramyxovirus envelope attachment protein, the first paramyxovirus envelope attachment protein, and / or the second paramyxovirus envelope attachment protein is a variant G protein that exhibits reduced binding for the native binding partner of a wild- type G protein. In some embodiments, the first paramyxovirus envelope attachment protein, and / or the second paramyxovirus envelope attachment protein and / or the third paramyxovirus envelope attachment protein is a variant G protein that exhibits reduced binding for the native binding partner of a wild-type G protein. In some embodiments, the first paramyxovirus envelope attachment protein, and / or the second paramyxovirus envelope attachment protein and / or the third paramyxovirus envelope attachment protein and / or the fourth paramyxovirus envelope attachment protein is a variant G protein that exhibits reduced binding for the native binding partner of a wild- type G protein. In some embodiments, the first paramyxovirus envelope attachment protein, and / or the second paramyxovirus envelope attachment protein and / or the third paramyxovirus envelope attachment protein and / or the fourth paramyxovirus envelope attachment protein and / or the fifth paramyxovirus envelope attachment protein, and / or one or more additional paramyxovirus envelope attachment proteins is a variant G protein that exhibits reduced binding for the native binding partner of a wild-type G protein. In some embodiments, the variant G protein or the biologically active portion thereof is a variant of wild-type NiV-G and exhibits reduced binding to one or both of the native binding partners Ephrin B2 or Ephrin B3. In some embodiments, the variant G-protein or the biologically active portion, such as a variant NiV-G protein, exhibits reduced binding to the native binding partner. In some embodiments, the reduced binding to Ephrin B2 or Ephrin B3 is reduced by greater than at or about 5%, at or about 10%, at or about 15%, at or about 20%, at or about 25%, at or about 30%, at or about 40%, at or about 50%, at or about 60%, at or about 70%, at or about 80%, at or about 90%, or at or about 100%.

[0145] In some embodiments, the mutations (e.g., amino acid substitutions) can improve transduction efficiency. In some embodiments, the mutations allow for specific targeting of other desired cell types that are not Ephrin B2 or Ephrin B3. In some embodiments, the mutations result in 39 sf-5966708186152009440 at least the partial inability to bind at least one natural receptor, such has reduce the binding to at least one of Ephrin B2 or Ephrin B3. In some embodiments, the mutations described herein interfere with natural receptor recognition.

[0146] In some embodiments, at least one G protein contains one or more amino acid substitutions in a residue that is involved in the interaction with one or both of Ephrin B2 and Ephrin B3. In some embodiments, the amino acid substitutions correspond to mutations E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1. In some embodiments, at least one G protein is a variant G protein containing one or more amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1. In some embodiments, at least one G protein is a variant G protein that contains one or more amino acid substitutions elected from the group consisting of E501A, W504A, Q530A and E533A with reference to SEQ ID NO:1 and is a biologically active portion thereof containing an N-terminal truncation.

[0147] In some embodiments, described herein is a lipid particle comprising a paramyxovirus envelope attachment protein that is not retargeted and comprises one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions. In one embodiment, a paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions. In one embodiment, a paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:1.

[0148] In some embodiments, the NiV-G is a variant NiV-G proteins that contain an altered cytoplasmic tail compared to native NiV-G (e.g. SEQ ID NO:5) that are or can be incorporated into a lipid particle, such as a viral particle, including a lentiviral particle or lentiviral-like particle. The cytoplasmic tail of NiV-G corresponds to amino acids 1-45 of SEQ ID NO:5. In some cases, it is understood that the N-terminal methionine of NiV-G, or a variant NiV-G, as described herein can be cleaved and the cytoplasmic tail lacks an initial N-terminal methionine. For instance, in some embodiments, the cytoplasmic tail of wild-type NiV-G may correspond to amino acids 2-45 of SEQ ID NO:5, and the variant NiV-G protein contains a cytoplasmic tail that is altered compared to amino acids 2-45 of SEQ ID NO:5. In some embodiments, the variant NiV-G contains a modified cytoplasmic tail in which the native cytoplasmic tail is truncated or is replaced by a heterologous cytoplasmic tail. 40 sf-5966708186152009440

[0149] Non-limiting examples of variant NiV-G proteins, including truncated NiV-G or NiV-G with a altered or modified cytoplasmic tail, are described in WO2013148327, WO2017182585, or PCT / US2022 / 081872. Further exemplary variant NiV-G proteins are described in Bender et al.2016 PLoS Pathol 12(6):e1005641

[0150] In some embodiments, at least one G protein is a variant G protein that is a functionally active variant or biologically active portion containing one or more amino acid mutations, such as one or more amino acid insertions, deletions, substitutions or truncations. In some embodiments, the mutations described herein relate to amino acid insertions, deletions, substitutions or truncations of amino acids compared to a reference G protein sequence. In some embodiments, the reference G protein sequence is the wild-type sequence of a G protein or a biologically active portion thereof. In some embodiments, at least one functionally active variant or the biologically active portion thereof is a variant of a wild-type Hendra (HeV) virus G protein, a wild-type Nipah (NiV) virus G-protein (NiV- G), a wild-type Cedar (CedPV) virus G-protein, a wild-type Mojiang virus G-protein, a wild-type bat Paramyxovirus G-protein or biologically active portion thereof. In some embodiments, the wild-type G protein has the sequence set forth in any one of SEQ ID NOS: 1, 561, 562, 563, or 564.

[0151] In some embodiments, at least one G protein is a variant G protein that is a biologically active portion that is an N-terminally and / or C-terminally truncated fragment of a wild-type Hendra (HeV) virus G protein, a wild-type Nipah (NiV) virus G-protein (NiV-G), a wild-type Cedar (CedPV) virus G-protein, a wild-type Mojiang virus G-protein, a wild-type bat Paramyxovirus G-protein. In particular embodiments, the truncation is an N-terminal truncation of all or a portion of the cytoplasmic domain. In some embodiments, at least one variant G protein is a biologically active portion that is truncated and lacks up to 49 contiguous amino acid residues at or near the N-terminus of the wild-type G protein, such as a wild-type G protein set forth in any one of SEQ ID NOS: 1, 561, 562, 563, or 564. In some embodiments, at least one variant G protein is truncated and lacks up to 49 contiguous amino acids, such as up to 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 30, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1 contiguous amino acids at the N-terminus of the wild-type G protein.

[0152] In some embodiments, at least one G protein is a wild-type Nipah virus G (NiV-G) protein or a Hendra virus G protein, or is a functionally active variant or biologically active portion thereof. In some embodiments, at least one G protein is a NiV-G protein that has the sequence set forth in SEQ ID NO:1, or is a functional variant or a biologically active portion thereof that has an amino acid sequence having at least at or about 80%, at least at or about 81%, at least at or about 82%, at least at or about 83%, at least at or about 84%, at least at or about 85%, at least at or about 86%, at least at or about 87%, at least at or about 88%, at least at or about 89%, at least at or about 90%, at least at or about 91%, at least at or about 92%, at least at or about 93%, at least at or about 94%, at least at or about 41 sf-5966708186152009440 95%, at or about 96%, at least at or about 97%, at least at or about 98%, at least at or about 99% sequence identity to SEQ ID NO:1.

[0153] In some embodiments, the variant NiV-G comprises a modified cytoplasmic tail which comprises a truncated cytoplasmic tail from a glycoprotein from the same Nipah virus. In some embodiments, the variant NiV-G contains a modified cytoplasmic tail in which at least a part of the native cytoplasmic tail (e.g. corresponding to amino acids 1-45 of SEQ ID NO:5) is a truncated portion thereof from a glycoprotein from Nipah Virus. In some embodiments, the cytoplasmic tail is a truncated portion thereof that is at least 5 amino acids in length. from or from about 5-44, from or from about 5-40, from or from about 5-30, from or from about 5-20, from or from about 5-10, from or from about 10-44, from or from about 10-40, from or from about 10-30, from or from about 10-20, from or from about 20- 44, from or from about 20-40, from or from about 20-30, from or from about 30-44, from or from about 30-40, from or from about 40-44amino acids in length. In some embodiments, the truncated portion thereof is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43 or 44 amino acids in length. In some embodiments, the variant NiV-G has a cytoplasmic tail that is a truncated NiV-G cytoplasmic tail.

[0154] In some embodiments, the truncated NiV-G cytoplasmic tail has a deletion of up to 40, up to 35, up to 30, up to 29, up to 28, up to 27, up to 26, up to 25, up to 24, up to 23, up to 22, up to 21, up to 20, up to 19, up to 18, up to 17, up to 16, up to 15, or up to 14 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G cytoplasmic tail set forth in SEQ ID NO: 28. In some embodiments, the truncated NiV-G cytoplasmic tail has a deletion of up to 40, up to 35, up to 30, up to 29, up to 28, up to 27, up to 26, up to 25, up to 24, up to 23, up to 22, up to 21, up to 20, up to 19, up to 18, up to 17, up to 16, up to 15, or up to 14 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G cytoplasmic tail set forth in SEQ ID NO: 4.

[0155] In some embodiments, the cytoplasmic tail of NiV-G is set forth in SEQ ID NO:4. In some embodiments, the variant NiV-G has a deletion of between 5 and 41 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G protein cytoplasmic tail set forth in SEQ ID NO: 4. In some embodiments, the variant NiV-G has a deletion of between 26 and 40 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G protein cytoplasmic tail set forth in SEQ ID NO: 4.

[0156] In some embodiments, at least one G protein is a variant NiV-G protein that is a biologically active portion of a wild-type NiV-G. In some embodiments, the biologically active portion is an N-terminally truncated fragment. In some embodiments, the variant NiV-G protein is truncated and lacks up to 5 contiguous amino acid residues at or near the N-terminus of the wild- type NiV-G protein, such as compared to wild-type NiV-G set forth in SEQ ID NO: 1. In some embodiments, the variant NiV-G protein is truncated and lacks up to 10 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G protein, such as compared to wild-type 42 sf-5966708186152009440 NiV-G set forth in SEQ ID NO: 1. In some embodiments, the variant NiV-G protein is truncated and lacks up to 15 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G protein, such as compared to wild-type NiV-G set forth in SEQ ID NO: 1. n some embodiments, the variant NiV-G protein is truncated and lacks up to 20 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G protein, such as compared to wild-type NiV-G set forth in SEQ ID NO: 1. In some embodiments, the variant NiV-G protein is truncated and lacks up to 25 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G protein, such as compared to wild-type NiV-G set forth in SEQ ID NO: 1. In some embodiments, the variant NiV-G protein is truncated and lacks up to 30 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G protein, such as compared to wild-type NiV-G set forth in SEQ ID NO: 1. In some embodiments, the variant NiV-G protein is truncated and lacks up to 35 contiguous amino acid residues at or near the N-terminus of the wild-type NiV-G protein, such as compared to wild-type NiV-G set forth in SEQ ID NO: 1. In some embodiments, the variant NiV-G protein (also called variant NiV-G) contains an N-terminal methionine.

[0157] In some embodiments, the variant NiV-G has a cytoplasmic tail deletion of amino acid residues 2-41, 2-40, 2-39, 2-38, 2-37, 2-36, 2-35, 2-34, 2-33, 2-32, 2-31, 2-30, 2-29, 2-28, 2-27, 2-26, 2- 25, 2-22, 2-21, 2-16, 2-11, or 2-5 of SEQ ID NO:4. In some embodiments, the cytoplasmic tail is a truncated portion of the Nipah virus cytoplasmic tail set forth in any one of SEQ ID NOS: 6-28. In some embodiments, the cytoplasmic tail is a truncated portion of the Nipah virus cytoplasmic tail set forth in any one of SEQ ID NOS: 6-28 that lacks the N-terminal methionine. In some embodiments, the variant NiV-G has a sequence in which the cytoplasmic tail, such as set forth in any one of SEQ ID NOS: 6-28, is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 2. In some embodiments, the variant NiV-G has a sequence in which the cytoplasmic tail set forth in any one of SEQ ID NOS: 6- 28 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 3. In some embodiments, the cytoplasmic tail is set forth in SEQ ID NO: 7, 13, or 19.

[0158] In some embodiments, the variant NiV-G comprises the sequence of amino acids set forth in SEQ ID NO: 211, 220 or 221, or a sequence of amino acids that exhibits at least 85% sequence identity, at least 86% sequence identity, at least 87% sequence identity, at least 88% sequence identity, at least 89% sequence identity, at least 90% sequence identity, at least 91% sequence identity, at least 92% sequence identity, at least 93% sequence identity, at least 94% sequence identity, at least 95% sequence identity, at least 96% sequence identity, at least 97% sequence identity, at least 98% sequence identity, or at least 99% sequence identity to any one of SEQ ID NOs: 211, 220 or 221. In some embodiments, the truncated NiV-G cytoplasmic tail is the sequence of amino acids set forth in SEQ ID NO: 211, 220 or 221. 43 sf-5966708186152009440

[0159] In some embodiments, the variant NiV-G comprises a modified cytoplasmic tail which comprises a heterologous cytoplasmic tail or a truncated portion thereof from a glycoprotein from another virus. In some embodiments, the other virus is a member of the Kingdom Orthornavirae. In some embodiments, the other virus is a member of the family Paramyxoviridae, Rhabdoviridae, Arenaviridae, or Retroviridae. In some embodiments, the other virus is a member of the family Paramyxoviridae.

[0160] In some embodiments, the variant NiV-G contains a modified cytoplasmic tail in which at least a part of the native cytoplasmic tail (e.g. corresponding to amino acids 1-45 of SEQ ID NO:5) is replaced by a heterologous cytoplasmic tail or a truncated portion thereof from a glycoprotein from another virus from another virus or viral-associated protein. In some embodiments, the replaced cytoplasmic tail is a heterologous cytoplasmic tail or a truncated portion thereof that is at least 5 amino acids in length. In some embodiments, the replaced heterologous cytoplasmic tail or a truncated portion thereof is from or from about 5-180 amino acids in length, such as from or from about 5-150, from or from about 5-100, from or from about 5-75, from or from about 5-50, from or from about 5-40, from or from about 5-30, from or from about 5-20, from or from about 5-10, from or from about 10-150, from or from about 10-100, from or from about 10-75, from or from about 10-50, from or from about 10-40, from or from about 10-30, from or from about 10-20, from or from about 20-150, from or from about 20-100, from or from about 20-75, from or from about 20-50, from or from about 20-40, from or from about 20- 30, from or from about 30-150, from or from about 30-100, from or from about 30-75, from or from about 30-50, from or from about 30-40, from or from about 40-150, from or from about 40-100, from or from about 40-75, from or from about 40-50, from or from about 50-150, from or from about 50-100, from or from about 50-75, from or from about 75-150, from or from about 75-100 or from or from about 100-150 amino acids in length. In some embodiments, the replaced heterologous cytoplasmic tail or a truncated portion thereof is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40 amino acids in length. In some embodiments, the heterologous cytoplasmic tail or the truncated portion thereof is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 2.

[0161] In some embodiments, the heterologous cytoplasmic tail is a cytoplasmic tail or a truncated portion thereof from a glycoprotein from another virus, such as a paramyxovirus, a retrovirus, a filovirus, a rhabdovirus or an arenavirus. In some embodiments, the virus is a paramyxovirus other than a Nipah virus. For instance, the virus is a measles virus, Bat paramyxovirus, Cedar Virus, Canine Distemper Virus, Sendai virus, Hendra virus, Human Parainfluenza virus, or Newcastle Disease virus. In some embodiments, the replaced heterologous cytoplasmic tail is the native cytoplasmic tail or a truncated portion of the native cytoplasmic tail of another virus, such as a truncated portion of the cytoplasmic tail set forth in any one of SEQ ID NOS: 40-166. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in any one of SEQ ID 44 sf-5966708186152009440 NOS: 40-166 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 2. In some embodiments, the variant NiV-G contains mutations in the extracellular domain that reduce or abrogate binding to an Ephrin B2 or B3 corresponding to one or more of E501A, W504A, Q530A and E533A, with numbering of residues as set forth SEQ ID NO:1. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in any one of SEQ ID NOS: 40-166 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 3. In some embodiments, it is understood that the heterologous cytoplasmic tail or the truncated portion thereof may include any sequence set forth in any one of SEQ ID NOS: 40-166 that lacks the N-terminal methionine.

[0162] In some embodiments, the virus is a retrovirus. For instance, the virus may be a baboon endogenous virus (BaEV), Gibbon Ape Leukemia virus (GaLV), murine leukemia virus, or human immunodeficiency virus 1 (HIV-1). In some embodiments, the replaced heterologous cytoplasmic tail is the native cytoplasmic tail or a truncated portion of the native cytoplasmic tail of another virus, such as set forth in any one of SEQ ID NOS: 167-168, 174-177, 179-182, or 185-199. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in any one of SEQ ID NOS: 167-168, 174-177, 179-182, or 185-199 is directly linked to the N- terminus of the sequence set forth in SEQ ID NO: 2. In some embodiments, the variant NiV-G contains mutations in the extracellular domain that reduce or abrogate binding to an Ephrin B2 or B3 corresponding to one or more of E501A, W504A, Q530A and E533A, with numbering of residues as set forth SEQ ID NO:1. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in any one of SEQ ID NOS: 167-168, 174-177, 179-182, or 185-199 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 3. In some embodiments, it is understood that the heterologous cytoplasmic tail or the truncated portion thereof may include any sequence set forth in any one of SEQ ID NOS: 167-168, 174-177, 179-182, or 185-199 that lacks the N-terminal methionine.

[0163] In some embodiments, the virus is a filovirus. For instance, the virus may be an Ebola virus (EboV). In some embodiments, the replaced heterologous cytoplasmic tail is the native cytoplasmic tail or a truncated portion of the native cytoplasmic tail of another virus, such as set forth in any one of SEQ ID NOS: 172 or 173. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in any one of SEQ ID NOS: 172 or 173 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 2. In some embodiments, the variant NiV-G contains mutations in the extracellular domain that reduce or abrogate binding to an Ephrin B2 or B3 corresponding to one or more of E501A, W504A, Q530A and E533A, with numbering of residues as set forth SEQ ID NO:1. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in any one of SEQ ID NOS: 45 sf-5966708186152009440 172 or 173 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 3. In some embodiments, it is understood that the heterologous cytoplasmic tail or the truncated portion thereof may include any sequence set forth in any one of SEQ ID NOS: 172 or 173 that lacks the N-terminal methionine.

[0164] In some embodiments, the virus is a rhabdovirus. For instance, the virus may be Cocal vesiculovirus (Cocal) or vesicular stomatitis virus (VSV). In some embodiments, the replaced heterologous cytoplasmic tail is the native cytoplasmic tail or a truncated portion of the native cytoplasmic tail of another virus, such as set forth in any one of SEQ ID NOS: 170, 171, 183, or 184. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in any one of SEQ ID NOS: 70, 171, 183, or 184 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 2. In some embodiments, the variant NiV-G contains mutations in the extracellular domain that reduce or abrogate binding to an Ephrin B2 or B3 corresponding to one or more of E501A, W504A, Q530A and E533A, with numbering of residues as set forth SEQ ID NO:1. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in any one of SEQ ID NOS: 70, 171, 183, or 184 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 3. In some embodiments, it is understood that the heterologous cytoplasmic tail or the truncated portion thereof may include any sequence set forth in any one of SEQ ID NOS: 70, 171, 183 or 184 that lacks the N-terminal methionine.

[0165] In some embodiments, the virus is an arenavirus. For instance, the virus may be Lymphocytic choriomeningitis virus (LCMV). In some embodiments, the replaced heterologous cytoplasmic tail is the native cytoplasmic tail or a truncated portion of the native cytoplasmic tail of another virus, such as set forth in SEQ ID NOS: 178. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in SEQ ID NOS: 178 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 2. In some embodiments, the variant NiV-G contains mutations in the extracellular domain that reduce or abrogate binding to an Ephrin B2 or B3 corresponding to one or more of E501A, W504A, Q530A and E533A, with numbering of residues as set forth SEQ ID NO:1. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail or the truncated portion thereof set forth in SEQ ID NOS: 178 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 3. In some embodiments, it is understood that the heterologous cytoplasmic tail or the truncated portion thereof may include any sequence set forth in any one of SEQ ID NOS: 178 that lacks the N-terminal methionine.

[0166] In some embodiments, at least one variant NiV-G protein is truncated and lacks up to amino acid 34 at or near the N-terminus of the wild-type NiV-G protein, such as compared to wild- type NiV-G set forth in SEQ ID NO: 1. In some embodiments, the variant NiV-G protein (also 46 sf-5966708186152009440 called variant NiV-G) contains an N-terminal methionine. In some embodiments, the variant NiV-G protein lacks amino acids 2-34 as compared to wild-type NiV-G set forth in SEQ ID NO:1. In some embodiments, the NiV-G is set forth in SEQ ID NO:228.

[0167] In particular embodiments, at least one G protein has the sequence of amino acids set forth in SEQ ID NO: 228, or is a functionally active variant thereof or a biologically active portion thereof that retains binding and / or fusogenic activity. In some embodiments, the functionally active variant comprises an amino acid sequence having at least at or about 80%, at least at or about 85%, at least at or about 90%, at least at or about 91%, at least at or about 92%, at least at or about 93%, at least at or about 94%, at least at or about 95%, at or about 96%, at least at or about 97%, at least at or about 98%, or at least at or about 99% sequence identity to SEQ ID NO: 228 and retains fusogenic activity in conjunction with a variant NiV-F protein as described. In some embodiments, at least one G protein is a variant G protein that comprises the amino acid sequence of SEQ ID NO: 228.

[0168] In some embodiments, the variant NiV-G contains a heterologous cytoplasmic tail that is a cytoplasmic tail or a truncated portion thereof from a glycoprotein from CD63. In some embodiments, the heterologous cytoplasmic tail replaces at least a part of the native cytoplasmic tail of NiV-G (e.g. corresponding to amino acids 1-45 of SEQ ID NO:5). In some embodiments, the heterologous tail is a contiguous sequence of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 N- terminal amino acids of the native cytoplasmic tail of CD63. In some embodiments, the native cytoplasmic tail of CD63 is set forth in SEQ ID NOs: 200, 201, or 202. In some embodiments, the heterologous cytoplasmic tail is a truncated portion of the CD63 cytoplasmic tail set forth in any one of SEQ ID NOS: 200-205. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail set forth in any one of SEQ ID NOS: 200-205 is directly linked to the N- terminus of the sequence set forth in SEQ ID NO: 2. In some embodiments, the variant NiV-G has a sequence in which the heterologous cytoplasmic tail set forth in any one of SEQ ID NOS: 200-205 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 3.

[0169] In some embodiments, the variant NiV-G comprises a modified cytoplasmic tail which comprises a mutated cytoplasmic tail from a glycoprotein from the same Nipah virus. In some embodiments, the variant NiV-G contains a modified cytoplasmic tail in which at least a part of the native cytoplasmic tail (e.g. corresponding to amino acids 1-45 of SEQ ID NO:5) is a mutated portion thereof from a glycoprotein from Nipah Virus. In some embodiments, the cytoplasmic tail is a mutated portion of the Nipah virus cytoplasmic tail set forth in any one of SEQ ID NOS: 29-38. In some embodiments, it is understood that the truncated NiV-G cytoplasmic tail may include the sequence set forth in any one of SEQ ID NOS: 29-38 that lacks the N-terminal methionine. In some embodiments, the variant NiV-G has a sequence in which the cytoplasmic tail set forth in any one of SEQ ID NOS: 29-38 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 2. In some embodiments, the 47 sf-5966708186152009440 variant NiV-G has a sequence in which the cytoplasmic tail set forth in any one of SEQ ID NOS: 29-38 is directly linked to the N-terminus of the sequence set forth in SEQ ID NO: 3.

[0170] In some embodiments, any of the provided lipid particles (lentiviral vectors) may also contain an F protein, such as a NiV-F protein, such as a full-length NiV-F protein or a biologically active portion thereof or a variant thereof. For instance, also provided herein are viral particles or viral-like particles, such as lentiviral particles or lentiviral-like particles, that are pseudotyped with any of the provided variant NiV-G proteins and a NiV-F protein, such as a full-length NiV-F protein or a biologically active portion or a variant thereof. Exemplary NiV-F proteins are further described in Section II.B.

[0171] In particular embodiments, the paramyxovirus envelope attachment protein, first paramyxovirus envelope attachment protein and / or second paramyxovirus envelope attachment protein, such as at least one G protein or functionally active variant or biologically active portion thereof, is a protein that retains fusogenic activity in conjunction with other retargeted attachment proteins, such as more than one G protein expressed as a multimer on the lipid bi-layer. In particular embodiments, the first paramyxovirus envelope attachment protein and / or the second paramyxovirus envelope attachment protein and / or the third paramyxovirus envelope attachment protein, such as at least one G protein or functionally active variant or biologically active portion thereof, is a protein that retains fusogenic activity in conjunction with other retargeted attachment proteins, such as more than one G protein expressed as a multimer on the lipid bi-layer. In particular embodiments, the first paramyxovirus envelope attachment protein and / or the second paramyxovirus envelope attachment protein and / or the third paramyxovirus envelope attachment protein and / or the fourth paramyxovirus envelope attachment protein, such as at least one G protein or functionally active variant or biologically active portion thereof, is a protein that retains fusogenic activity in conjunction with other retargeted attachment proteins, such as more than one G protein expressed as a multimer on the lipid bi-layer. In particular embodiments, the first paramyxovirus envelope attachment protein and / or the second paramyxovirus envelope attachment protein and / or the third paramyxovirus envelope attachment protein and / or the fourth paramyxovirus envelope attachment protein and / or one or more additional paramyxovirus envelope attachment proteins, such as at least one G protein or functionally active variant or biologically active portion thereof, is a protein that retains fusogenic activity in conjunction with other retargeted attachment proteins, such as more than one G protein expressed as a multimer on the lipid bi-layer. Fusogenic activity includes the activity of the paramyxovirus envelope attachment protein in conjunction with a protein that is a paramyxovirus fusion protein (e.g., an F protein) to promote or facilitate fusion of two membrane lumens, such as the lumen of the targeted lipid particle having embedded in its lipid bilayer at least two paramyxovirus envelope attachment protein and paramyxovirus fusion protein 48 sf-5966708186152009440 (e.g., F and G proteins), and a cytoplasm of a target cell, e.g. a cell that contains a surface receptor or molecule that is recognized or bound by the targeted envelope protein.

[0172] Reference to retaining fusogenic activity includes activity of a lipid particle (e.g. lentiviral vector) containing at least two paramyxovirus envelope attachment protein and paramyxovirus fusion protein (e.g., F and G proteins) that is between at or about 10% and at or about 150% or more of the level or degree of binding of a reference lipid particle (e.g. lentiviral vector) that is similar, such as contains the same variant NiV-F, but that contains the corresponding wild-type G protein, such as set forth in SEQ ID NO: 1. For instance, a lipid particle (e.g. lentiviral vector) that retains fusogenic activity has at least or at least about 10% of the level or degree of fusogenic activity of the reference lipid particle that is similar (such as contains the same variant NiV-F) but that contains the corresponding wild-type G protein, such as at least or at least about 15% of the level or degree of fusogenic activity, at least or at least about 20% of the level or degree of fusogenic activity, at least or at least about 25% of the level or degree of fusogenic activity, at least or at least about 30% of the level or degree of fusogenic activity, at least or at least about 35% of the level or degree of fusogenic activity, at least or at least about 40% of the level or degree of fusogenic activity, at least or at least about 45% of the level or degree of fusogenic activity, at least or at least about 50% of the level or degree of fusogenic activity, at least or at least about 55% of the level or degree of fusogenic activity, at least or at least about 60% of the level or degree of fusogenic activity, at least or at least about 65% of the level or degree of fusogenic activity, at least or at least about 70% of the level or degree of fusogenic activity, at least or at least about 75% of the level or degree of fusogenic activity, at least or at least about 80% of the level or degree of fusogenic activity, at least or at least about 85% of the level or degree of fusogenic activity, at least or at least about 90% of the level or degree of fusogenic activity, at least or at least about 95% of the level or degree of fusogenic activity, at least or at least about 100% of the level or degree of fusogenic activity, or at least or at least about 120% of the level or degree of fusogenic activity.

[0173] Reference to retaining fusogenic activity includes activity of a lipid particle (e.g. lentiviral vector) containing at least two paramyxovirus envelope attachment protein and paramyxovirus fusion protein (e.g., F and G proteins) that is between at or about 10% and at or about 150% or more of the level or degree of binding of a reference lipid particle (e.g. lentiviral vector) that is similar, such as contains the same variant NiV-F, but that contains only one of the provided paramyxovirus envelope attachment proteins (e.g., G proteins). For instance, a lipid particle (e.g. lentiviral vector) that retains fusogenic activity has at least or at least about 10% of the level or degree of fusogenic activity of the reference lipid particle that is similar (such as contains the same variant NiV-F) but that contains only one of the provided paramyxovirus envelope attachment proteins, such as at least or at least about 15% of the level or degree of fusogenic activity, at least or at least about 20% of the level or degree of fusogenic activity, at least or at least about 25% of the level or degree of fusogenic activity, at least or at least about 49 sf-5966708186152009440 30% of the level or degree of fusogenic activity, at least or at least about 35% of the level or degree of fusogenic activity, at least or at least about 40% of the level or degree of fusogenic activity, at least or at least about 45% of the level or degree of fusogenic activity, at least or at least about 50% of the level or degree of fusogenic activity, at least or at least about 55% of the level or degree of fusogenic activity, at least or at least about 60% of the level or degree of fusogenic activity, at least or at least about 65% of the level or degree of fusogenic activity, at least or at least about 70% of the level or degree of fusogenic activity, at least or at least about 75% of the level or degree of fusogenic activity, at least or at least about 80% of the level or degree of fusogenic activity, at least or at least about 85% of the level or degree of fusogenic activity, at least or at least about 90% of the level or degree of fusogenic activity, at least or at least about 95% of the level or degree of fusogenic activity, at least or at least about 100% of the level or degree of fusogenic activity, or at least or at least about 120% of the level or degree of fusogenic activity. a. Mutated Paramyxovirus G proteins

[0174] In some embodiment, the G protein is a Paramyxovirus G glycoprotein (e.g., variant Paramyxovirus G glycoproteins) comprising one or more amino acid mutations that result in decreased glycosylation of the protein. The one or more amino acid mutations, also called deglycosylation mutations, can be one or more amino acid substitutions (also referred to as mutations).

[0175] In some embodiments, the mutant Paramyxovirus G glycoprotein comprises an amino acid substitution at one or more amino acid positions that reduce glycosylation of the G glycoprotein. In some embodiments, the one or more amino acid substitutions disrupts an N-linked glycosylation site. In some embodiments, the one or more amino acid substitutions disrupts an O-linked glycosylation site.

[0176] In some embodiments, the mutant Paramyxovirus G glycoprotein is derived from Morbillivirus (e.g., measles virus (MeV), canine distemper virus, Cetacean morbillivirus, Peste-des- petits-ruminants virus, Phocine distemper virus, Rinderpest virus), Henipavirus (e.g., Hendra (HeV) virus, Nipah (NiV) virus, a Cedar (CedPV) virus, Mòjiāng virus, a Langya virus or bat Paramyxovirus). In some embodiments, the mutant Paramyxovirus G glycoprotein is a mutant of a Paramyxovirus G glycoprotein derived from Nipah virus or Measles virus. In some embodiments, the mutant Paramyxovirus G protein is a mutant of a paramyxovirus G protein selected from the group consisting of SEQ ID NOs: 1, 561-564 or a modified Paramyxovirus G glycoprotein derived from any one of 1, 5, 561-564 containing an altered cytoplasmic tail . In some embodiments, the mutant Paramyxovirus G protein has a sequence of amino acids that has at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94% or at least 95% to any one of SEQ ID NOs: 1, 5, 561-564 and contains the acid substitution at one or more amino acid positions that reduce glycosylation of the G glycoprotein as provided herein. In some embodiments, the mutant Paramyxovirus G protein that has one or more amino acid mutations that result in decreased glycosylation is a mutant of the truncated NiV-G set forth in SEQ ID NO:228. 50 sf-5966708186152009440

[0177] The location of precited glycosylation sites can be determined using the sequence of a protein. For example, N-glycosylation often occurs at sites with the sequence N-X-S / T in which “X” is any amino acid except P. Various algorithms and tools are available for prediction of both N- and O- linked glycosylation, including SprintGly (http: / / sparks-lab.org / server / sprint-gly / ), NetNGlyc (https: / / services.healthtech.dtu.dk / service.php?NetNGlyc-1.0), NetOGlyc (https: / / services.healthtech.dtu.dk / service.php?NetOGlyc-4.0), and GlycoMinestruct(http: / / glycomine.erc.monash.edu / Lab / GlycoMine_Struct / ), and methods described in Pitti et al., Sci. Reports, 9:15975 (2019) and Pakhrin et al., Molecules 26:7314 (2021). Any predicted glycosylation site may be substituted as described herein.

[0178] In some embodiments, the Paramyxovirus G glycoprotein to which the deglycosylation mutation is made is a NiV-G set forth in SEQ ID NO: 1 or a modified Nipah G glycoprotein (NiV-G) that has an altered cytoplasmic tail compared to native NiV-G (e.g., SEQ ID NO: 1). In some embodiments, the variant Paramyxovirus G protein has a sequence of amino acids that has at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94% or at least 95% to SEQ ID NO: 1 and contains the acid substitution at one or more amino acid positions that reduce glycosylation of the G glycoprotein as provided herein. In some embodiments, the Paramyxovirus G glycoprotein to which the deglycosylation mutation is made is a NiV-G set forth in SEQ ID NO: 5 or a modified Nipah G glycoprotein (NiV-G) that has an altered cytoplasmic tail compared to native NiV-G (e.g., SEQ ID NO: 1). In some embodiments, the variant Paramyxovirus G protein has a sequence of amino acids that has at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94% or at least 95% to SEQ ID NO: 5 and contains the acid substitution at one or more amino acid positions that reduce glycosylation of the G glycoprotein as provided herein.

[0179] Exemplary modified NiV-G proteins with altered cytoplasmic tails to which the one or more amino acid substitutions for reducing glycosylation can be incorporated are described in Section II.A.1.

[0180] Amino acid positions for substitutions are described herein with positions “corresponding to” positions of a reference sequence. It is understood that the amino acid substitutions are not limited to being made in only the reference sequence but also can be made in similar sequences by identification of residues that align or correspond with the reference positions. For instance, positions “corresponding to” to positions of a protein in a reference sequence can be identified upon alignment of a similar sequence with the referenced sequence based on structural sequence alignment or using a standard alignment algorithm, such as the GAP algorithm. By aligning the sequences, one skilled in the art can identify corresponding residues, for example, using conserved and identical amino acid residues as guides. For instance, amino acid positions for mutations are described herein with reference to the exemplary truncated NiV-G sequence set forth in SEQ ID NO:5; however, similar amino acid positions for 51 sf-5966708186152009440 mutations as described can be made in other modified NiV-G sequences, such as any as described in Section II.A.1, by sequence alignment and identification of the corresponding residues.

[0181] In some embodiments, the one or more amino acid mutations are at positions corresponding to positions 39, 126, 128, 273, 345, 384, 448, and 496 of SEQ ID NO:5. In some embodiments, the variant Paramyxovirus G glycoprotein comprises an amino acid mutation at any one of positions 39, 126, 128, 273, 345, 384, 448, and 496 of SEQ ID NO:5. In some embodiments, the variant Paramyxovirus G glycoprotein comprises two or more amino acid mutations at any of positions corresponding to positions 39, 126, 128, 273, 345, 384, 448, and 496 of SEQ ID NO:5., such as mutations at 2, 3, 4, 5, 7, or 8 of the positions.

[0182] In some embodiments, the one or more amino acid mutations is at a position corresponding to position 39 of SEQ ID NO:5. In some embodiments, the one or more amino acid mutations is at a position corresponding to position 126 of SEQ ID NO:5. In some embodiments, the one or more amino acid mutations is at a position corresponding to position 128 of SEQ ID NO:5. In some embodiments, the one or more amino acid mutations is at a position corresponding to position 273 of SEQ ID NO:5. In some embodiments, the one or more amino acid mutations is at a position corresponding to position 345 of SEQ ID NO:5. In some embodiments, the one or more amino acid mutations is at a position corresponding to position 384 of SEQ ID NO:5. In some embodiments, the one or more amino acid mutations is at a position corresponding to position 448 of SEQ ID NO:5. In some embodiments, the one or more amino acid mutations is at a position corresponding to position 496 of SEQ ID NO:5.

[0183] In some embodiments, the native amino acid at the position comprising the amino acid mutation is asparagine or serine. In some embodiments, the amino acid mutation is an amino acid substitution. In some embodiments, the mutation is an asparagine to glutamine substitution. In some embodiments, the mutation is a serine to alanine substitution.

[0184] In some embodiments, the mutation is an asparagine to glutamine substitution at a position corresponding to position 39 (N39Q) of SEQ ID NO:5. In some embodiments, the mutation is an asparagine to glutamine substitution at a position corresponding to position 126 (N126Q) of SEQ ID NO: 5. In some embodiments, the mutation is an asparagine to glutamine substitution at a position corresponding to position 273 (N273Q) of SEQ ID NO: 5. In some embodiments, the mutation is an asparagine to glutamine substitution at a position corresponding to position 345 (N345Q) of SEQ ID NO: 5. In some embodiments, the mutation is an asparagine to glutamine substitution at a position corresponding to position 384 (N384Q) of SEQ ID NO: 5. In some embodiments, the mutation is an asparagine to glutamine substitution at a position corresponding to position 448 (N448Q) of SEQ ID NO: 5. In some embodiments, the mutation is an asparagine to glutamine substitution at a position corresponding to position 496 (N496Q) of SEQ ID NO: 5. 52 sf-5966708186152009440

[0185] In some embodiments, the mutation is a serine to alanine substitution at a position corresponding to position 128 (S128A) of SEQ ID NO: 5.

[0186] In some embodiments, the G glycoprotein is derived from Nipah virus G protein and the one or more amino acid substitutions are at positions corresponding to positions selected from the group consisting of 39, 126, 128, 273, 345, 384, 448, and 496 of SEQ ID NO: 5. In some embodiments, the one or more amino acid substitutions are selected from N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q or any combination thereof. In some embodiments, the G glycoprotein is a mutant NiV- G containing one amino acid substitution from any one of N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q. In some embodiments, the G glycoprotein is a mutant NiV-G containing two amino acid substitutions from any two of N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q. In some embodiments, the G glycoprotein is a mutant NiV-G containing three amino acid substitutions from any three of N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q. In some embodiments, the G glycoprotein is a mutant NiV-G containing four amino acid substitutions from any one of N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q. In some embodiments, the G glycoprotein is a mutant NiV-G containing five amino acid substitutions from any one of N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q. In some embodiments, the G glycoprotein is a mutant NiV-G containing six amino acid substitutions from any one of N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q. In some embodiments, the G glycoprotein is a mutant NiV-G containing seven amino acid substitutions from any one of N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q. In some embodiments, the G glycoprotein is a mutant NiV-G containing eight amino acid substitutions from any one of N39Q, N126Q, S128A, N273Q, N345Q, N384Q, N448Q, N496Q. In some embodiments, the one or more amino acid substitutions are in the SEQ ID NO:5 or a or a modified Nipah G glycoprotein (NiV-G) that has an altered cytoplasmic tail compared to native NiV-G (e.g., SEQ ID NO:5). In some embodiments, the amino acid substitutions are in a modified NiV-G protein described in Section II.A. In some embodiments, the amino acid substitutions are in the NiV-G set forth in SEQ ID NO:5.

[0187] In some embodiments, the variant Nipah-G protein comprises at least three amino acid substitutions. In some embodiments, the amino acid substitutions are at positions 273, 384, and 496 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 273, 345, and 496 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, 126, and 128 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, 273, and 345 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, 384, and 448 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, 448, and 496 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, 128, and 273 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, 345, and 384 of 53 sf-5966708186152009440 SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, 384, and 448 of SEQ ID NO:5.

[0188] In some embodiments, the variant Nipah-G protein comprises at least two amino acid substitutions. In some embodiments, the amino acid substitutions are at positions 273, and 496 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 345, and 496 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39 and 128 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, and 345 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39, and 448 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39 and 496 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39 and 273 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 39 and 384 of SEQ ID NO:5. In some embodiments, the amino acid substitutions are at positions 384 and 448 of SEQ ID NO:5.

[0189] In some embodiments, the amino acid substitution is at position 39 of SEQ ID NO:5. In some embodiments, the amino acid substitution is at position 126 of SEQ ID NO:5. In some embodiments, the amino acid substitution is at position 128 of SEQ ID NO:5. In some embodiments, the amino acid substitution is at position 273 of SEQ ID NO:5. In some embodiments, the amino acid substitution is at position 345 of SEQ ID NO:5. In some embodiments, the amino acid substitution is at position 384 of SEQ ID NO:5. In some embodiments, the amino acid substitution is at position 448 of SEQ ID NO:5. In some embodiments, the amino acid substitution is at position 496 of SEQ ID NO:5.

[0190] In some embodiments, the mutant Nipah-G protein comprises an asparagine to glutamine substitution at position 39 of SEQ ID NO:5. In some embodiments, the mutant Nipah-G protein comprises an asparagine to glutamine substitution at position 126 of SEQ ID NO:5. In some embodiments, the mutant Nipah-G protein comprises an asparagine to glutamine substitution at position 273 of SEQ ID NO:5. In some embodiments, the mutant Nipah-G protein comprises an asparagine to glutamine substitution at position 345 of SEQ ID NO:5. In some embodiments, the mutant Nipah-G protein comprises an asparagine to glutamine substitution at position 384 of SEQ ID NO:5. In some embodiments, the mutant Nipah-G protein comprises an asparagine to glutamine substitution at position 448 of SEQ ID NO:5. In some embodiments, the mutant Nipah-G protein comprises an asparagine to glutamine substitution at position 496 of SEQ ID NO:5. In some embodiments, the mutant Nipah-G protein comprises a serine to alanine substitution at position 128 of SEQ ID NO:5.

[0191] In some embodiments, the mutant Nipah-G protein comprises the sequence selected from the group consisting of any one of SEQ ID NOs: 640-766, such as any exemplary mutant Nipah-G proteins set forth in Table 2A below. In some embodiments, the mutant Nipah-G protein comprises the sequence of SEQ ID NO: 660. In some embodiments, the variant Nipah-G protein comprises the sequence of SEQ 54 sf-5966708186152009440 ID NO: 663. In some embodiments, the variant Nipah-G protein comprises the sequence of SEQ ID NO: 667. Table 2A: Exemplary Mutated Paramyxovirus Nipah G Proteins NiV-G SEQ Position Position Position Position Position Position Position (Mutated) ID 39 126 273 345 384 448 496 NO NivG 5 N N N N N N N NivG.690640Q N N N N N N NivG.691641N Q N N N N N NivG.693642N N Q N N N N NivG.694643N N N Q N N N NivG.695644N N N N Q N N NivG.696645N N N N N Q N NivG.697646N N N N N N Q NivG.699647N N N Q Q Q N NivG.700648N N N Q N Q N NivG.701649N N N Q N N Q NivG.702650Q Q Q Q Q Q Q NivG.740651N N N N N Q Q NivG.742652N N N N Q N Q NivG.743653N N N N Q Q N NivG.744654N N N N Q Q Q NivG.748655N N N Q N Q Q NivG.749656N N N Q Q N N NivG.750657N N N Q Q N Q NivG.752658N N N Q Q Q Q NivG.753659N N Q N N N Q NivG.754660N N Q N N Q N NivG.755661N N Q N N Q Q NivG.756662N N Q N Q N N NivG.757663N N Q N Q N Q NivG.758664N N Q N Q Q N NivG.759665N N Q N Q Q Q NivG.760666N N Q Q N N N NivG.761667N N Q Q N N Q NivG.762668N N Q Q N Q N NivG.763669N N Q Q N Q Q NivG.764670N N Q Q Q N N NivG.765671N N Q Q Q N Q NivG.766672N N Q Q Q Q N NivG.767673N N Q Q Q Q Q NivG.768674N Q N N N N Q NivG.769675N Q N N N Q N NivG.770676N Q N N N Q Q NivG.771677N Q N N Q N N 55 sf-5966708186152009440 NivG.772678N Q N N Q N Q NivG.773679N Q N N Q Q N NivG.774680N Q N N Q Q Q NivG.775681N Q N Q N N N NivG.776682N Q N Q N N Q NivG.777683N Q N Q N Q N NivG.778684N Q N Q N Q Q NivG.779685N Q N Q Q N N NivG.780686N Q N Q Q N Q NivG.781687N Q N Q Q Q N NivG.782688N Q N Q Q Q Q NivG.783689N Q Q N N N N NivG.784690N Q Q N N N Q NivG.785691N Q Q N N Q N NivG.786692N Q Q N N Q Q NivG.787693N Q Q N Q N N NivG.788694N Q Q N Q N Q NivG.789695N Q Q N Q Q N NivG.790696N Q Q N Q Q Q NivG.791697N Q Q Q N N N NivG.792698N Q Q Q N N Q NivG.793699N Q Q Q N Q N NivG.794700N Q Q Q N Q Q NivG.795701N Q Q Q Q N N NivG.796702N Q Q Q Q N Q NivG.797703N Q Q Q Q Q N NivG.798704N Q Q Q Q Q Q NivG.799705Q N N N N N Q NivG.800706Q N N N N Q N NivG.801707Q N N N N Q Q NivG.802708Q N N N Q N N NivG.803709Q N N N Q N Q NivG.804710Q N N N Q Q N NivG.805711Q N N N Q Q Q NivG.806712Q N N Q N N N NivG.807713Q N N Q N N Q NivG.808714Q N N Q N Q N NivG.809715Q N N Q N Q Q NivG.810716Q N N Q Q N N NivG.811717Q N N Q Q N Q NivG.812718Q N N Q Q Q N NivG.813719Q N N Q Q Q Q NivG.814720Q N Q N N N N NivG.815721Q N Q N N N Q NivG.816722Q N Q N N Q N 56 sf-5966708186152009440 NivG.817723Q N Q N N Q Q NivG.818724Q N Q N Q N N NivG.819725Q N Q N Q N Q NivG.820726Q N Q N Q Q N NivG.821727Q N Q N Q Q Q NivG.822728Q N Q Q N N N NivG.823729Q N Q Q N N Q NivG.824730Q N Q Q N Q N NivG.825731Q N Q Q N Q Q NivG.826732Q N Q Q Q N N NivG.827733Q N Q Q Q N Q NivG.828734Q N Q Q Q Q N NivG.829735Q N Q Q Q Q Q NivG.830736Q Q N N N N N NivG.831737Q Q N N N N Q NivG.832738Q Q N N N Q N NivG.833739Q Q N N N Q Q NivG.834740Q Q N N Q N N NivG.835741Q Q N N Q N Q NivG.836742Q Q N N Q Q N NivG.837743Q Q N N Q Q Q NivG.838744Q Q N Q N N N NivG.839745Q Q N Q N N Q NivG.840746Q Q N Q N Q N NivG.841747Q Q N Q N Q Q NivG.842748Q Q N Q Q N N NivG.843749Q Q N Q Q N Q NivG.844750Q Q N Q Q Q N NivG.845751Q Q N Q Q Q Q NivG.846752Q Q Q N N N N NivG.847753Q Q Q N N N Q NivG.848754Q Q Q N N Q N NivG.849755Q Q Q N N Q Q NivG.850756Q Q Q N Q N N NivG.851757Q Q Q N Q N Q NivG.852758Q Q Q N Q Q N NivG.853759Q Q Q N Q Q Q NivG.854760Q Q Q Q N N N NivG.855761Q Q Q Q N N Q NivG.856762Q Q Q Q N Q N NivG.857763Q Q Q Q N Q Q NivG.858764Q Q Q Q Q N N NivG.859765Q Q Q Q Q N Q NivG.860766Q Q Q Q Q Q N 57 sf-5966708186152009440

[0192] In some embodiments, the Paramyxovirus G glycoprotein to which the deglycosylation mutations is made is a Measles virus H (Mev-H) protein or a modified MeV-H protein that has an altered cytoplasmic tail compared to native MeV-H (e.g., SEQ ID NO:769). In some embodiments, the mutant Paramyxovirus G protein has a sequence of amino acids that has at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94% or at least 95% to SEQ ID NO: 769 and contains the acid substitution at one or more amino acid positions that reduce glycosylation of the G glycoprotein as provided herein.

[0193] In some embodiments, the G glycoprotein is derived from Measles virus H (Mev-H) protein and the one or more amino acid substitutions are at positions corresponding to positions selected from the group consisting of 168, 187, 200, 215, 238 of SEQ ID NO: 769. In some embodiments, the mutant Mev- H protein comprises at least two amino acid substitutions, such as 2, 3, 4, or 5 substitutions at positions 168, 187, 200, 215, 238 of SEQ ID NO: 769.

[0194] In some embodiments, the Paramyxovirus G glycoprotein to which the deglycosylation mutations is made is a Canine distemper virus H (CDV-H) protein or a modified CDV-H protein that has an altered cytoplasmic tail compared to native CDV-H (e.g., SEQ ID NO: 770). In some embodiments, the mutant Paramyxovirus G protein has a sequence of amino acids that has at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94% or at least 95% to SEQ ID NO: 770 and contains the acid substitution at one or more amino acid positions that reduce glycosylation of the G glycoprotein as provided herein.

[0195] In some embodiments, the G glycoprotein is derived from Canine distemper virus H (CDV- H) protein and the one or more amino acid substitutions are at positions corresponding to positions selected from the group consisting of 19, 149, 422 of SEQ ID NO: 770. In some embodiments, the variant CDV-H protein comprises at least two amino acid substitutions, such as 2 or 3 substitutions at positions 19, 149, 422 of SEQ ID NO: 770. 2. Retargeted Attachment Proteins

[0196] In some embodiments, a paramyxovirus envelope attachment protein, such as a G protein (e.g., NiV-G), is further attached or linked in tandem with at least two binding domains that bind to a first and second target molecule respectively to comprise a retargeted attachment protein. For instance, provided in some aspects is a lipid particle that includes a targeted paramyxovirus envelope attachment proteins (e.g., a chimeric attachment G protein) containing any of the provided G proteins described above that is attached (e.g., operably fused in tandem) to a first and second binding domain, in which the retargeted attachment protein (e.g., re-targeted G protein) is exposed on the surface of the targeted lipid particle (e.g. lentiviral vector). In some of any of the provided embodiments, the lipid particle comprises a retargeted attachment protein comprising (i) a paramyxovirus envelope attachment protein; and (ii) a 58 sf-5966708186152009440 first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (iii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell.

[0197] In some embodiments, each of the one or more of the paramyxovirus envelope attachment proteins, such as a G protein (e.g., NiV-G), is further attached or linked in tandem to a first and a second targeting moiety, e.g., a first and second binding domain or a binding agent, directed to a first and second target molecule expressed on the surface of a target cell. The binding domains or binding agents can be individually selected from any binding domain or binding agent described herein, e.g., in Section II. Accordingly, in some embodiments, the lipid particle comprises one or more retargeted attachment proteins, wherein each of the one or more retargeted attachment proteins independently comprise: (i) a paramyxovirus envelope attachment protein; and (ii) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (iii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell. The targeting moieties can be a binding domain or binding agent, such as any binding domain or any binding agent described herein, e.g., in Section II.

[0198] In some embodiments, the envelope attachment protein is a retargeted attachment protein containing a henipavirus G protein or a biologically active portion thereof. In some embodiments, the envelope attachment proteins (e.g., G protein) may be retargeted by tandem linkage to a targeting moiety, such as a binding molecule (e.g. antibody or antigen-binding fragment, e.g. sdAb or scFv) that binds to a target cell, such as a retargeted attachment protein. In some embodiments, the retargeted attachment protein and paramyxovirus fusion protein (e.g., G protein and a NiV-F protein provided herein) together exhibit fusogenic activity to a target cell, such as to deliver an exogenous agent or nucleic acid exogenous agent to the target cell.

[0199] In some embodiments, the lipid particle comprises at least two retargeted attachment proteins comprising paramyxovirus envelope attachment proteins (e.g., G proteins), wherein at least one is retargeted by tandem linkage (e.g., operable fusion in tandem) to a first and a second targeting moiety, such as a binding molecule (e.g. antibody or antigen-binding fragment, e.g. sdAb or scFv) that binds to a target cell.

[0200] In some embodiments, the retargeted attachment protein is retargeted by tandem linkage to a first and second targeting moiety, wherein the targeting moieties are directed to a target molecule expressed on the surface of a target cell. In some embodiments, the retargeted attachment protein is retargeted by tandem linkage to a first and second targeting moiety, wherein the first and second targeting moiety are directed to the same target molecule expressed on the surface of a target cell. In some embodiments, the retargeted attachment protein is retargeted by tandem linkage to a first and second targeting moiety, wherein the first and second targeting moiety are directed to a first and second target molecule expressed on the surface of a target cell that are different. In some embodiments, the targeting one or both of the first target molecule and the second target molecule does not activate or 59 sf-5966708186152009440 inhibit, induce a phenotype change (for example maturation and / or differentiation), induce proliferation, and / or induce apoptosis of said target cell.

[0201] In some embodiments, the lipid particle comprises at least three retargeted attachment proteins comprising paramyxovirus envelope attachment proteins (e.g., G proteins), wherein at least one is retargeted by tandem linkage to a first and second targeting moiety, such as a binding molecule (e.g. antibody or antigen-binding fragment, e.g. sdAb or scFv) that binds to a target cell. In some embodiments, the lipid particle comprises at least three retargeted attachment proteins comprising envelope attachment proteins (e.g., G proteins), wherein at least two are retargeted by tandem linkage to a first and second targeting moiety, such as a binding molecule (e.g. antibody or antigen-binding fragment, e.g. sdAb or scFv) that binds to a target cell. In some embodiments, the lipid particle comprises at least three retargeted attachment proteins comprising envelope attachment proteins (e.g., G proteins), wherein at least three are retargeted by tandem linkage to a first and second targeting moiety, such as a binding molecule (e.g. antibody or antigen-binding fragment, e.g. sdAb or scFv) that binds to a target cell.

[0202] In some embodiments, the first, second, and third retargeted attachment proteins are retargeted by tandem linkage to a first and second targeting moiety, wherein the targeting moieties are independently directed to a first and second target molecule expressed on the surface of a target cell. In some embodiments, the first, second, and third retargeted attachment proteins are retargeted by tandem linkage to a first, second, and third targeting moiety, wherein the first and second targeting moiety, or the second and third targeting moiety, or the first and third targeting moiety, or the first, second, and third target moiety, are directed to the same target molecule expressed on the surface of a target cell. In some embodiments, the first, second, and third retargeted attachment proteins are retargeted by tandem linkage to a first, second, and third targeting moiety, wherein the first, second, and third targeting moiety are directed to a first, second, and third target molecule expressed on the surface of a target cell that are different. In some embodiments, the targeting of one, two, or three of the first target molecule, the second target molecule, and the third target molecule does not activate or inhibit, induce a phenotype change (for example maturation and / or differentiation), induce proliferation, and / or induce apoptosis of said target cell.

[0203] In some embodiments, the lipid particle comprises at least four or at least five retargeted attachment proteins comprising paramyxovirus envelope attachment proteins (e.g., G proteins), wherein at least one, at least two, at least three, or at least four is retargeted by tandem linkage to a first and second targeting moiety, such as a binding molecule (e.g. antibody or antigen-binding fragment, e.g. sdAb or scFv) that binds to a target cell. In some embodiments, the lipid particle comprises at least four or at least five retargeted attachment proteins comprising envelope attachment proteins (e.g., G proteins), wherein at least two or at least three are retargeted by tandem linkage to a first and second targeting 60 sf-5966708186152009440 moiety, such as a binding molecule (e.g. antibody or antigen-binding fragment, e.g. sdAb or scFv) that binds to a target cell. In some embodiments, the lipid particle comprises at least four or at least five retargeted attachment proteins comprising envelope attachment proteins (e.g., G proteins), wherein at least four or at least five are retargeted by tandem linkage to a targeting moiety, such as a binding molecule (e.g. antibody or antigen-binding fragment, e.g. sdAb or scFv) that binds to a target cell.

[0204] In some embodiments, the paramyxovirus retargeted attachment protein is a targeted envelope protein containing a G protein provided herein. In some embodiments the paramyxovirus retargeted attachment protein comprises at least one envelope attachment proteins (e.g., G protein) that is any of those provided in Section II.A, including NiV-G proteins with cytoplasmic domain modifications, truncated NiV-G cytoplasmic tails, or modified NiV-G cytoplasmic tails.

[0205] In some of any embodiments, the retargeted attachment protein comprises (a) a retargeted attachment protein comprising a first paramyxovirus envelope attachment protein operably fused in tandem with (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell. In some embodiments, the targeting moiety is a binding domain, such as any of the binding domains or binding agents described herein in Section II.A.2, e.g., a T cell binding domain or an HSC binding domain. In some embodiments, the binding domain can be any agent that binds to a cell surface molecule on a target cells. In some embodiments, the binding domain can be an antibody or an antibody portion or fragment. In some embodiments, the binding domain is a single domain antibody (sdAb). In some embodiments, the binding domain is a single chain variable fragment (scFv). The binding domain can be linked directly or indirectly to the G protein. In particular embodiments, the binding domain is linked to the C-terminus (C-terminal amino acid) of the G protein or the biologically active portion thereof. The linkage can be via a peptide linker, such as a flexible peptide linker.

[0206] The retargeted attachment protein comprising a first paramyxovirus envelope attachment protein operably fused in tandem with (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety may be modulated to have different binding strengths. For example, scFvs and antibodies with various binding strengths may be used to alter the fusion activity of the retargeted attachment proteins towards cells that display high or low amounts of the target antigen. For example DARPins with different affinities may be used to alter the fusion activity towards cells that display high or low amounts of the target antigen. Binding domains may also be modulated to target different regions on the target ligand, which will affect the fusion rate with cells displaying the target.

[0207] The binding domain may comprise a humanized antibody molecule, intact IgA, IgG, IgE or IgM antibody; bi- or multi- specific antibody (e.g., Zybodies®, etc.); antibody fragments such as Fab fragments, Fab’ fragments, F(ab’)2 fragments, Fd’ fragments, Fd fragments, and isolated CDRs 61 sf-5966708186152009440 or sets thereof; single chain Fvs; polypeptide-Fc fusions; single domain antibodies (e.g., shark single domain antibodies such as IgNAR or fragments thereof); cameloid antibodies; masked antibodies (e.g., Probodies®); Small Modular ImmunoPharmaceuticals (“SMIPsTM”); single chain or Tandem diabodies (TandAb®); VHHs; Anticalins®; Nanobodies®; minibodies; BiTE®s; ankyrin repeat proteins or DARPINs®; Avimers®; DARTs; TCR-like antibodies;, Adnectins®; Affilins®; Trans- bodies®; Affibodies®; TrimerX®; MicroProteins; Fynomers®, Centyrins®; and KALBITOR®s. A targeting moiety can also include an antibody or an antigen-binding fragment thereof (e.g., Fab, Fab', F(ab')2, Fv fragments, scFv antibody fragments, disulfide-linked Fvs (sdFv), a Fd fragment consisting of the VH and CH1 domains, linear antibodies, single domain antibodies such as sdAb (either VL or VH), nanobodies, or camelid VHH domains), an antigen-binding fibronectin type III (Fn3) scaffold such as a fibronectin polypeptide minibody, a ligand, a cytokine, a chemokine, or a T cell receptor (TCRs).

[0208] The binding domain may comprise a humanized antibody molecule, intact IgA, IgG, IgE or IgM antibody; bi- or multi- specific antibody (e.g., Zybodies®, etc.); antibody fragments such as Fab fragments, Fab’ fragments, F(ab’)2 fragments, Fd’ fragments, Fd fragments, and isolated CDRs or sets thereof; single chain Fvs; polypeptide-Fc fusions; single domain antibodies (e.g., shark single domain antibodies such as IgNAR or fragments thereof); cameloid antibodies; masked antibodies (e.g., Probodies®); Small Modular ImmunoPharmaceuticals (“SMIPsTM”); single chain or Tandem diabodies (TandAb®); VHHs; Anticalins®; Nanobodies®; minibodies; BiTE®s; ankyrin repeat proteins or DARPINs®; Avimers®; DARTs; TCR-like antibodies;, Adnectins®; Affilins®; Trans- bodies®; Affibodies®; TrimerX®; MicroProteins; Fynomers®, Centyrins®; and KALBITOR®s. A targeting moiety can also include an antibody or an antigen-binding fragment thereof (e.g., Fab, Fab', F(ab')2, Fv fragments, scFv antibody fragments, disulfide-linked Fvs (sdFv), a Fd fragment consisting of the VH and CH1 domains, linear antibodies, single domain antibodies such as sdAb (either VL or VH), nanobodies, or camelid VHH domains), an antigen-binding fibronectin type III (Fn3) scaffold such as a fibronectin polypeptide minibody or a T cell receptor (TCRs). In some embodiments, the binding domain does not comprise a ligand, a cytokine, or a chemokine,

[0209] In some embodiments, the binding domain is a single chain molecule. In some embodiments, the binding domain is a single domain antibody. In some embodiments, the binding domain is a single chain variable fragment. In particular embodiments, the binding domain contains an antibody variable sequence (s) that is human or humanized.

[0210] In some embodiments, the binding domain is a single domain antibody. In some embodiments, the single domain antibody can be human or humanized. In some embodiments, the single domain antibody or portion thereof is naturally occurring. In some embodiments, the single domain antibody or portion thereof is synthetic. 62 sf-5966708186152009440

[0211] In some embodiments, the single domain antibodies are antibodies whose complementary determining regions are part of a single domain polypeptide. In some embodiments, the single domain antibody is a heavy chain only antibody variable domain. In some embodiments, the single domain antibody does not include light chains.

[0212] In some embodiments, the heavy chain antibody devoid of light chains is referred to as VHH. In some embodiments, the single domain antibody antibodies have a molecular weight of 12-15 kDa. In some embodiments, the single domain antibody antibodies include camelid antibodies or shark antibodies. In some embodiments, the single domain antibody molecule is derived from antibodies raised in Camelidae species, for example in camel, llama, dromedary, alpaca, vicuna and guanaco. In some embodiments, the single domain antibody is referred to as immunoglobulin new antigen receptors (IgNARs) and is derived from cartilaginous fishes. In some embodiments, the single domain antibody is generated by splitting dimeric variable domains of human or mouse IgG into monomers and camelizing critical residues.

[0213] In some embodiments, the single domain antibody can be generated from display libraries, e.g., phage display libraries. In some embodiments, the display libraries are generated from a VHH repertoire of camelids immunized with various antigens, as described in Arbabi et al., FEBS Letters, 414, 521-526 (1997); Lauwereys et al., EMBO J., 17, 3512-3520 (1998); Decanniere et al., Structure, 7, 361- 370 (1999). In some embodiments, the display library is generated comprising antibody fragments of a non-immunized camelid. In some embodiments, single domain antibodies a library of human single domain antibodies is synthetically generated by introducing diversity into one or more scaffolds.

[0214] In some embodiments, the binding domain is a single domain antibody (sdAb). In some embodiments, the binding domain is a single chain variable fragment (scFv). The binding domain can be linked directly or indirectly to the paramyxovirus envelope attachment protein, first paramyxovirus envelope attachment protein, and / or second paramyxovirus envelope attachment protein (e.g., G protein, and / or retargeted attachment protein). In particular embodiments, the binding domain is linked to the C- terminus (C-terminal amino acid) of the G protein or the biologically active portion thereof. The linkage can be via a peptide linker, such as a flexible peptide linker. In particular embodiments, the first and / or second targeting moiety is operably fused in tandem with the paramyxovirus envelope attachment protein.

[0215] In some embodiments, the C-terminus of the binding domain is attached to the C-terminus of the G protein or biologically active portion thereof. In some embodiments, the N-terminus of the binding domain is exposed on the exterior surface of the lipid bilayer. In some embodiments, the N-terminus of the binding domain binds to a cell surface molecule of a target cell. In some embodiments, the binding domain specifically binds to a cell surface molecule present on a target cell. In some embodiments, the 63 sf-5966708186152009440 cell surface molecule is a protein, glycan, lipid or low molecular weight molecule. In some embodiments, the binding domain is one of any binding domains as described above.

[0216] In some embodiments, a binding domain (e.g. sdAb or one of any binding domains as described herein) binds to a cell surface antigen of a cell. In some embodiments, a cell surface antigen is characteristic of one type of cell. In some embodiments, a cell surface antigen is characteristic of more than one type of cell.

[0217] In some embodiments, the cell surface molecule of a target cell is an antigen or portion thereof. In some embodiments, the single domain antibody or portion thereof is an antibody having a single monomeric domain antigen binding / recognition domain that is able to bind selectively to a specific antigen. In some embodiments, the single domain antibody binds an antigen present on a target cell.

[0218] Exemplary cells include polymorphonuclear cells (also known as PMN, PML, PMNL, or granulocytes), stem cells, embryonic stem cells, neural stem cells, mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), human myogenic stem cells, muscle-derived stem cells (MuStem), embryonic stem cells (ES or ESCs), limbal epithelial stem cells, cardio-myogenic stem cells, cardiomyocytes, progenitor cells, immune effector cells, lymphocytes, macrophages, dendritic cells, natural killer cells, T cells, cytotoxic T lymphocytes, allogenic cells, resident cardiac cells, induced pluripotent stem cells (iPS), adipose-derived or phenotypic modified stem or progenitor cells, CD133+ cells, aldehyde dehydrogenase-positive cells (ALDH+), umbilical cord blood (UCB) cells, peripheral blood stem cells (PBSCs), neurons, neural progenitor cells, pancreatic beta cells, glial cells, or hepatocytes.

[0219] In some embodiments, the target cell is a cell of a target tissue. The target tissue can include liver, lungs, heart, spleen, pancreas, gastrointestinal tract, kidney, testes, ovaries, brain, reproductive organs, central nervous system, peripheral nervous system, skeletal muscle, endothelium, inner ear, or eye.

[0220] In some embodiments, the target cell is a muscle cell (e.g., skeletal muscle cell), kidney cell, liver cell (e.g. hepatocyte), or a cardiac cell (e.g. cardiomyocyte). In some embodiments, the target cell is a cardiac cell, e.g., a cardiomyocyte (e.g., a quiescent cardiomyocyte), a hepatoblast (e.g., a bile duct hepatoblast), an epithelial cell, a T cell (e.g. a naive T cell), a macrophage (e.g., a tumor infiltrating macrophage), or a fibroblast (e.g., a cardiac fibroblast).

[0221] In some embodiments, the target cell is a tumor-infiltrating lymphocyte, a T cell, a neoplastic or tumor cell, a virus-infected cell, a stem cell, a central nervous system (CNS) cell, a hematopoietic stem cell (HSC), a liver cell or a fully differentiated cell. In some embodiments, the target cell is a CD3+ T cell, a CD4+ T cell, a CD8+ T cell, a hepatocyte, a hematopoietic stem cell, a CD34+ hematopoietic stem cell, a CD105+ hematopoietic stem cell, a CD117+ hematopoietic stem cell, a CD105+ endothelial cell, a B cell, a CD20+ B cell, a CD19+ B cell, a cancer cell, a 64 sf-5966708186152009440 CD133+ cancer cell, an EpCAM+ cancer cell, a CD19+ cancer cell, a Her2 / Neu+ cancer cell, a GluA2+ neuron, a GluA4+ neuron, a NKG2D+ natural killer cell, a SLC1A3+ astrocyte, a SLC7A10+ adipocyte, or a CD30+ lung epithelial cell.

[0222] In some embodiments, the target cell is an antigen presenting cell, an MHC class II+ cell, a professional antigen presenting cell, an atypical antigen presenting cell, a macrophage, a dendritic cell, a myeloid dendritic cell, a plasmacyteoid dendritic cell, a CD11c+ cell, a CD11b+ cell, a splenocyte, a B cell, a hepatocyte, a endothelial cell, or a non-cancerous cell). In some embodiments, the first and second target molecules are present on the same target cell. In some embodiments, the first and second target molecules are present on different cells.

[0223] In some embodiments, the binding domain (e.g. sdAb) variable domain binds a cell surface molecule or antigen. In some embodiments, the cell surface molecule is ASGR1, ASGR2, TM4SF5, CD8, CD4, or low density lipoprotein receptor (LDL-R). In some embodiments, the cell surface molecule is ASGR1. In some embodiments, the cell surface molecule is ASGR2. In some embodiments, the cell surface molecule is TM4SF5. In some embodiments, the cell surface molecule is CD8. In some embodiments, the cell surface molecule is CD4. In some embodiments, the cell surface molecule is LDL- R.

[0224] In some embodiments, the target cell is a hematopoietic lineage cell. Reference to a "hematopoietic cell" includes blood cells, both from the myeloid and the lymphoid lineage. In particular, the term "hematopoietic cell" includes both undifferentiated or poorly differentiated cells, such as hematopoietic stem cells and progenitor cells, and differentiated cells such as T lymphocytes, B lymphocytes, or dendritic cells. In some embodiments, the hematopoietic cells are hematopoietic stem cells (HSCs), CD34+ progenitor cells, in particular peripheral blood CD34+ cells, very early progenitor CD34+ cells, B-cell CD19+ progenitors, myeloid progenitor CD13+ cells, T lymphocytes, B lymphocytes, monocytes, dendritic cells, cancer B cells in particular B-cell chronic lymphocytic leukemia (BCLL) cells and marginal zone lymphoma (MZL) B cells, or thymocytes.

[0225] As known from the skilled person, many hematopoietic cells are produced from bone marrow hematopoietic stem cells.

[0226] In some embodiments, a hematopoietic cell is a hematopoietic stem cell (HSC), which are cells able to replenish all blood cell types and to self-renew. Hematopoietic stem cells may be in particular defined as cells that keep the levels of myeloid, T cells, and B cells at robustly detectable levels (typically more than 1 % of peripheral blood cells) for 16 weeks when injected into the circulation of a recipient mouse with a depleted hematopoietic system (Schroeder (2010) Cell Stem Cell 6:203-207).

[0227] In some embodiments, the hematopoietic cell is a "CD34+ progenitor cell,” which is a heterogeneous cell population that includes a subpopulation of HSCs, pluripotent stem cells and cells in the early stages of lineage commitment. CD34+ progenitor cells continuously migrate to and from the 65 sf-5966708186152009440 bone marrow in normal adult animals. They can differentiate to produce all hematopoietic cell lineages found in the circulation. In some embodiments, the hematopoietic cell is a very early progenitor CD34+ cell which is a subgroup of CD34+ progenitor cells enriched from HSCs.

[0228] In some embodiments, the hematopoietic cell is a "peripheral blood CD34+ cell”, which is a CD34+ cell present in the blood.

[0229] In some embodiments, the hematopoietic cell is a B cell CD19+ progenitor, which is a population of B-lineage cells that express cell surface CD10, CD34, and CD19.

[0230] In some embodiments, the hematopoietic cell is a myeloid progenitor CD13+ cells, which is a population of myeloid lineage cells that express cell surface CD34 and CD13, and in some cases, also CD33.

[0231] In some embodiments, the target cell is selected from the group consisting of myeloid- lymphoid balanced hematopoietic lineage cells, myeloid-biased hematopoietic lineage cells, lymphoid- biased hematopoietic lineage cells, a platelet-biased hematopoietic lineage cells, a platelet-myeloid- biased hematopoietic lineage cells, a long-term repopulating hematopoietic lineage cells, an intermediate- term repopulating hematopoietic lineage cells, or a short-term repopulating hematopoietic lineage cells. In some embodiments, the target cell is selected from monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, megakaryocytes and platelets. In some embodiments, the target cell is selected from T cells, B cells, natural killer (NK) cells and innate lymphoid cells.

[0232] In some embodiments the target cell is an effector cell, e.g., a cell of the immune system that expresses one or more Fc receptors and mediates one or more effector functions. In some embodiments, a target cell may include one or more of a monocyte, macrophage, neutrophil, dendritic cell, eosinophil, mast cell, platelet, large granular lymphocyte, Langerhans' cell, natural killer (NK) cell, T lymphocyte (e.g., T cell), a Gamma delta T cell, B lymphocyte (e.g., B cell) and may be from any organism including humans, mice, rats, rabbits, and monkeys.

[0233] In some embodiment, the hematopoietic cell is a T cell. In some embodiments, the T cell is a naïve T cell. In some embodiments, the T cell is a memory T cell.

[0234] In some embodiments, the hematopoietic cell is a B cell. In some embodiments, the target cell is a resting B cell, such as a naive or a memory B cell. In some embodiments, the target cell is a cancer B cell, such as a B-cell chronic lymphocytic leukemia (BCLL) cell or a marginal zone lymphoma (MZL) B cell.

[0235] In some embodiments, the target cell is a thymocyte. In some embodiments, the target cell is a natural killer (NK) cell. In some embodiments, the thymocyte expresses CD4 or CD8. In some embodiments, the thymocyte does not express CD4 or CD8. In some embodiments, the natural killer (NK) cell is a cell that expresses CD56.

[0236] In some embodiments, the target cell is a CD3+ T cell, a CD4+ T cell, or a CD8+ T cell. 66 sf-5966708186152009440

[0237] In some embodiments, the target cell is an antigen presenting cell, an MHC class II+ cell, a professional antigen presenting cell, an atypical antigen presenting cell, a macrophage, a dendritic cell, a myeloid dendritic cell, a plasmacyteoid dendritic cell, a CD11c+ cell, a CD11b+ cell, or a B cell.

[0238] In some embodiments, the binding domain (e.g. sdAb) variable domain binds a cell surface molecule or antigen. In some embodiments, the cell surface molecule is ASGR1, ASGR2, TM4SF5, CD3, CD8, CD4, CD7, or low density lipoprotein receptor (LDL-R). In some embodiments, the cell surface molecule is ASGR1. In some embodiments, the cell surface molecule is ASGR2. In some embodiments, the cell surface molecule is TM4SF5. In some embodiments, the cell surface molecule is CD3. In some embodiments, the cell surface molecule is CD8. In some embodiments, the cell surface molecule is CD4. In some embodiments, the cell surface molecule is LDL-R. In some embodiments, the cell surface molecule is ASCT2, CD105, CD110, CD117, CD133, CD146, CD164, CD34, CD46, CD49f, CD90, EPCR, or ITGA3.

[0239] In some embodiments, the retargeted attachment protein comprises the paramyxovirus envelope attachment protein (e.g., G protein or functionally active variant or biologically active portion thereof) linked directly to the binding domain and / or variable domain thereof. In some embodiments, the targeted envelope protein is a fusion protein that has the following structure: (N’-single domain antibody- C’)-(C’-G protein-N’).

[0240] In some embodiments, the retargeted attachment protein comprises the paramyxovirus envelope attachment protein (e.g., G protein or functionally active variant or biologically active portion thereof) linked indirectly via a linker to the binding domain and / or variable domain thereof. In some embodiments, the linker is a peptide linker. In some embodiments, the linker is a chemical linker.

[0241] In some embodiments, the linker is a peptide linker and the targeted envelope protein is a fusion protein containing the paramyxovirus envelope attachment protein (e.g., G protein or functionally active variant or biologically active portion thereof) linked via a peptide linker to the sdAb variable domain. In some embodiments, the targeted envelope protein is a fusion protein that has the following structure: (N’-single domain antibody-C’)-Linker-(C’-G protein-N’).

[0242] In some embodiments, the linker is a polypeptide linker. The polypeptide linker can be a flexible linker or a rigid linker or a combination of both. In some aspects, the linker is a short, medium or long linker. In some embodiments, the peptide linker is up to 65 amino acids in length. In some embodiments, the peptide linker comprises from or from about 2 to 65 amino acids, 2 to 60 amino acids, 2 to 56 amino acids, 2 to 52 amino acids, 2 to 48 amino acids, 2 to 44 amino acids, 2 to 40 amino acids, 2 to 36 amino acids, 2 to 32 amino acids, 2 to 28 amino acids, 2 to 24 amino acids, 2 to 20 amino acids, 2 to 18 amino acids, 2 to 14 amino acids, 2 to 12 amino acids, 2 to 10 amino acids, 2 to 8 amino acids, 2 to 6 amino acids, 6 to 65 amino acids, 6 to 60 amino acids, 6 to 56 amino acids, 6 to 52 amino acids, 6 to 67 sf-5966708186152009440 48 amino acids, 6 to 44 amino acids, 6 to 40 amino acids, 6 to 36 amino acids, 6 to 32 amino acids, 6 to 28 amino acids, 6 to 24 amino acids, 6 to 20 amino acids, 6 to 18 amino acids, 6 to 14 amino acids, 6 to 12 amino acids, 6 to 10 amino acids, 6 to 8 amino acids, 8 to 65 amino acids, 8 to 60 amino acids, 8 to 56 amino acids, 8 to 52 amino acids, 8 to 48 amino acids, 8 to 44 amino acids, 8 to 40 amino acids, 8 to 36 amino acids, 8 to 32 amino acids, 8 to 28 amino acids, 8 to 24 amino acids, 8 to 20 amino acids, 8 to 18 amino acids, 8 to 14 amino acids, 8 to 12 amino acids, 8 to 10 amino acids, 10 to 65 amino acids, 10 to 60 amino acids, 10 to 56 amino acids, 10 to 52 amino acids, 10 to 48 amino acids, 10 to 44 amino acids, 10 to 40 amino acids, 10 to 36 amino acids, 10 to 32 amino acids, 10 to 28 amino acids, 10 to 24 amino acids, 10 to 20 amino acids, 10 to 18 amino acids, 10 to 14 amino acids, 10 to 12 amino acids, 12 to 65 amino acids, 12 to 60 amino acids, 12 to 56 amino acids, 12 to 52 amino acids, 12 to 48 amino acids, 12 to 44 amino acids, 12 to 40 amino acids, 12 to 36 amino acids, 12 to 32 amino acids, 12 to 28 amino acids, 12 to 24 amino acids, 12 to 20 amino acids, 12 to 18 amino acids, 12 to 14 amino acids, 14 to 65 amino acids, 14 to 60 amino acids, 14 to 56 amino acids, 14 to 52 amino acids, 14 to 48 amino acids, 14 to 44 amino acids, 14 to 40 amino acids, 14 to 36 amino acids, 14 to 32 amino acids, 14 to 28 amino acids, 14 to 24 amino acids, 14 to 20 amino acids, 14 to 18 amino acids, 18 to 65 amino acids, 18 to 60 amino acids, 18 to 56 amino acids, 18 to 52 amino acids, 18 to 48 amino acids, 18 to 44 amino acids, 18 to 40 amino acids, 18 to 36 amino acids, 18 to 32 amino acids, 18 to 28 amino acids, 18 to 24 amino acids, 18 to 20 amino acids, 20 to 65 amino acids, 20 to 60 amino acids, 20 to 56 amino acids, 20 to 52 amino acids, 20 to 48 amino acids, 20 to 44 amino acids, 20 to 40 amino acids, 20 to 36 amino acids, 20 to 32 amino acids, 20 to 28 amino acids, 20 to 26 amino acids, 20 to 24 amino acids, 24 to 65 amino acids, 24 to 60 amino acids, 24 to 56 amino acids, 24 to 52 amino acids, 24 to 48 amino acids, 24 to 44 amino acids, 24 to 40 amino acids, 24 to 36 amino acids, 24 to 32 amino acids, 24 to 30 amino acids, 24 to 28 amino acids, 28 to 65 amino acids, 28 to 60 amino acids, 28 to 56 amino acids, 28 to 52 amino acids, 28 to 48 amino acids, 28 to 44 amino acids, 28 to 40 amino acids, 28 to 36 amino acids, 28 to 34 amino acids, 28 to 32 amino acids, 32 to 65 amino acids, 32 to 60 amino acids, 32 to 56 amino acids, 32 to 52 amino acids, 32 to 48 amino acids, 32 to 44 amino acids, 32 to 40 amino acids, 32 to 38 amino acids, 32 to 36 amino acids, 36 to 65 amino acids, 36 to 60 amino acids, 36 to 56 amino acids, 36 to 52 amino acids, 36 to 48 amino acids, 36 to 44 amino acids, 36 to 40 amino acids, 40 to 65 amino acids, 40 to 60 amino acids, 40 to 56 amino acids, 40 to 52 amino acids, 40 to 48 amino acids, 40 to 44 amino acids, 44 to 65 amino acids, 44 to 60 amino acids, 44 to 56 amino acids, 44 to 52 amino acids, 44 to 48 amino acids, 48 to 65 amino acids, 48 to 60 amino acids, 48 to 56 amino acids, 48 to 52 amino acids, 50 to 65 amino acids, 50 to 60 amino acids, 50 to 56 amino acids, 50 to 52 amino acids, 54 to 65 amino acids, 54 to 60 amino acids, 54 to 56 amino acids, 58 to 65 amino acids, 58 to 60 amino acids, or 60 to 65 amino acids. In some embodiments, the peptide linker is a polypeptide that is 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 68 sf-5966708186152009440 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, or 65 amino acids in length.

[0243] The linkers can be naturally-occurring, synthetic or a combination of both. Natural linkers can be either flexible or constrained (e.g., structured) and can be very diverse in amino acid sequence and composition. Their degree of resistance to proteolysis depends on which proteins they originate from and which biological environment these proteins are facing in nature (extracellular, intracellular, prokaryotic, eukaryotic, etc.). In some embodiments, the linker is a linker based on peptides found in human proteins. Examples of natural linkers are: (i) KES GSVS SEQL AQFRSLD (see Bird et al. (1988) Science, 242, 423-426), (ii) sequences corresponding to the hinge domain of immunoglobulins devoid of light chains (see Hamers-Casterman et al. (1993) Nature, 363, 446-448 and PCT International Publication No: WO 096 / 34103). Examples of linkers for use with anti-albumin domain antibodies (e.g., human, humanized, camelized human or Camelid VHH domain antibodies) are EPKIPQPQPKPQPQPQPQPKPQPKPEPECTCPKCP and TNEVCKCPKCP. Other linkers derived from human and camelid hinges are disclosed in EPO656946, incorporated herein by reference. The hinge derived linkers can have variable lengths, for example from 0 to about 50 amino acids, including 1, 2, 3, 4, 5, 6, 7, 8, 9, 1011, 12 ,13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48 or 49 amino acids..

[0244] Particularly suitable linker polypeptides predominantly include amino acid residues selected from Glycine (Gly), Serine (Ser), Alanine (Ala), and Threonine (Thr). For example, the linker may contain at least 75% (calculated on the basis of the total number of residues present in the peptide linker), such as at least 80%, at least 85%, or at least 90% of amino acid residues selected from Gly, Ser, Ala, and Thr. The linker may also consist of Gly, Ser, Ala and / or Thr residues only. In some embodiments, the linker contains 1-25 glycine residues, 5-20 glycine residues, 5-15 glycine residues, or 8-12 glycine residues. In some aspects, suitable peptide linkers typically contain at least 50% glycine residues, such as at least 75% glycine residues. In some embodiments, a peptide linker comprises glycine residues only. In some embodiments, a peptide linker comprises glycine and serine residues only.

[0245] In particular embodiments, the linker is a flexible peptide linker. Flexible linkers are designed to adopt no stable secondary structure when connecting two polypeptide moieties, thus allowing a range of conformations in the fusion protein. These linkers are preferably hydrophilic in nature to prevent these from interacting with one or both fused polypeptides. Usually small polar residues such as glycine and serine are prevalent in those linkers in order to increase the flexible and hydrophilic characteristics of the peptide backbone, respectively. The length of these linkers is variable and best determined either empirically or with the aid of 3D computing approaches. In general, a preferred linker length will be the smallest compatible with good expression, good solubility and. full recovery of the native functions and structures of interest. Because of their flexible characteristics, flexible linkers may 69 sf-5966708186152009440 constitute good substrates for endogenous proteases. In general, unless it is a desirable feature flexible linkers are devoid of amino acids such as charged amino acids or large hydrophobic / aromatic which are readily recognized by endogenous proteases with broad substrate specificity.

[0246] In some embodiments, these linkers are composed predominately of the amino acids Glycine and Serine, denoted as GS-linkers herein. In some such embodiments, the linker is 1-20 amino acids, such as 1-20 amino acids predominantly composed of glycine. In some embodiments, the linker is 1-20 amino acids, such as 1-20 amino acids predominantly composed of glycine and serine. In some embodiments, the linker is a flexible peptide linker containing amino acids Glycine and Serine, referred to as GS-linkers. In some embodiments, the peptide linker includes the sequences GS, GGS, GGGGS, GGGGGS or combinations thereof. In some embodiments, the polypeptide linker has the sequence (GGS)n, wherein n is 1 to 10. In some embodiments, the polypeptide linker has the sequence (GGGGS)n, wherein n is 1 to 10. In some embodiments, the polypeptide linker has the sequence (GGGGGS)n, wherein n is 1 to 6. In some embodiments, the polypeptide linker has or comprises the amino acid sequence of SEQ ID NO: 405 (GGGGSGGGGSGGGGS).

[0247] In some cases, it may be desirable to provide some rigidity into the peptide linker. This may be accomplished by including proline residues in the amino acid sequence of the peptide linker. Thus, in some embodiments, a linker comprises at least one proline residue in the amino acid sequence of the peptide linker. For example, a peptide linker can have an amino acid sequence wherein at least 25% (e.g., at least 50% or at least 75%) of the amino acid residues are proline residues. In one particular embodiment, the peptide linker comprises proline residues only.

[0248] In some aspects, a peptide linker comprises at least one cysteine residue, such as one cysteine residue. For example, in some embodiments, a linker comprises at least one cysteine residue and amino acid residues selected from the group consisting of Gly, Ser, Ala, and Thr. In some such embodiments, a linker comprises glycine residues and cysteine residues, such as glycine residues and cysteine residues only. Typically, only one cysteine residue will be included per peptide linker. One example of a specific linker comprising a cysteine residue includes a peptide linker having the amino acid sequence Glym-Cys- Glyn, wherein n and m are each integers from 1-12, e.g., from 3-9, from 4-8, or from 4-7.

[0249] In some embodiments, the linker of the fusion protein is a structured linker. Constrained and / or structured linkers are designed to adopt a stable secondary structure when connecting two polypeptide moieties, thus restricting the range of conformations in the fusion protein. Such linkers usually adopt a helical structure spanning several turns. Again the length of these linkers is variable and best determined either empirically or with the aid of computing approaches. In some embodiments, constrained and / or structured linkers maintain the longest distance between each polypeptide of the fusion. This is particularly relevant when both polypeptides have a tendency to form hetero-aggregates. By virtue of their structure, constrained linkers can also be more resistant to proteolytic degradation, 70 sf-5966708186152009440 thereby offering an advantage when injected in vivo. Examples of constrained linkers are cited in PCT International Publications No: WO 00 / 24884 (e.g.. SSSASASSA, GSPGSPG, or ATTTGSSPGPT), US 6,132,992 (e.g.. helical peptide linkers).

[0250] In particular embodiments, the structured linker contains the sequence (AP)n or (EAAAK)n, wherein n is 2 to 20, preferably 4 to 10, including but not limited to, AS-(AP)n-GT or AS-(EAAAK)n- GT, wherein n is 2 to 20, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15. In other embodiments, the linker comprises the sequences (GGGGA)n, (PGGGS)n, (AGGGS)n or GGS-(EGKSSGSGSESKST)n- GGS, wherein n is 2 to 20, (ADAAP)n (wherein n is 2 to 20), (ADAAP)n-G (wherein n is 2 to 20), (GEPQG)n (wherein n is 2 to 20), (GEPQG)n-G (wherein n is 2 to 20), (AGGEP)n (wherein n is 2 to 20), (AGGEP)n-G (wherein n is 2 to 20), (AGSEP)n (wherein n is 2 to 20), (AGSEP)n-G (wherein n is 2 to 20), (GGGEQ)n (wherein n is 2 to 20), (GGGEQ)n-G (wherein n is 2 to 20). In some embodiments, the linker is SSSASASSA, GSPGSPG, ATTTGSSPGPT, ADAAPADAAPG, GEPQGGEPQGG, AGGEPAGGEPG, AGSEPAGSEPG, or GGGEQGGGEQG.

[0251] In some embodiments, the polypeptide linker has or comprises the amino acid sequence of SEQ ID NO: 589 (AHHSED). In some embodiments, the polypeptide linker has or comprises the amino acid sequence of SEQ ID NO: 590 (EPKTPKPQPQPQPQPQPNPTTE).

[0252] In some embodiments, the retargeted attachment protein comprising a binding domain, a first binding domain, and / or a second binding domain linked to at least one paramyxovirus envelope attachment may comprise an engineered binding domain, such as an artificially generated binding domain. The binding domain may comprise a nanobody, a DARPin, an Aptamer, an Affimer, an Affibody, a Knottin, an Avimer, a Monobody, an Anticalin, a Fynomer. Any engineered binding domain known in art and suitable for the present invention can be used, for example any such binding domain described in Olaleye et al. Biomolecules.2021 Dec; 11(12): 1791. a. T Cell Binding Domains

[0253] In some embodiments, the lipid particles disclosed herein comprise one or more retargeted attachment proteins, each independently comprising (i) a paramyxovirus envelope attachment protein; and (ii) a targeting moiety directed to a target molecule expressed on the surface of a target cell. In some embodiments, the targeting moiety is a T cell binding domain, e.g., a T cell binding agent, such as any of those disclosed herein.

[0254] The lipid particles disclosed herein include, in some embodiments, one or more T cell binding domains (e.g., a T cell binding agent) that target the viral vector to a T cell. In some embodiments, the T cell binding agent binds to a molecule expressed on the surface of the T cell. The cell surface molecule may be a receptor, coreceptor, or a GPI-anchored protein. In some embodiments, the T cell binding agent binds CD3, CD4 or CD8. 71 sf-5966708186152009440

[0255] In some embodiments, a T cell binding agent may be fused to or incorporated in a protein fusogen or lipid particle envelope attachment protein (e.g., a retargeted attachment protein). In some embodiments, a T cell binding agent may be incorporated into the viral envelope via fusion with a transmembrane domain. In some embodiments, the T cell binding agent targets the lipid particle to a T cell.

[0256] In particular embodiments, a T cell binding agent may be fused to or incorporated in a protein fusogen or attachment protein, thereby retargeting the lipid particle to a T cell. In some embodiments, for re-targeting the T cell binding agent is fused to a protein fusogen or envelope attachment protein that is mutated to reduce binding for the native binding partner of the fusogen or viral envelope protein. In some embodiments, the fusogen is or contains a mutant G protein or a biologically active portion thereof that is a mutant of wild-type NiV-G and exhibits reduced binding to one or both of the native binding partners Ephrin B2 or Ephrin B3, including any as described above. Thus, in some aspects, a fusogen can be retargeted to display altered tropism. In some embodiments, the binding confers re-targeted binding compared to the binding of a wild-type surface glycoprotein protein in which a new or different binding activity is conferred. In particular embodiments, the binding confers re-targeted binding compared to the binding of a wild-type G protein in which a new or different binding activity is conferred. In some embodiments the fusogen is randomly mutated. In some embodiments the fusogen is rationally mutated. In some embodiments the fusogen is subjected to directed evolution. In some embodiments the fusogen is truncated and only a subset of the peptide is used in the viral vector. In some embodiments, amino acid residues in the measles hemagglutinin protein may be mutated to alter the binding properties of the protein, redirecting fusion (doi:10.1038 / nbt942, Molecular Therapy vol.16 no. 8, 1427–1436 Aug.2008, doi:10.1038 / nbt1060, DOI: 10.1128 / JVI.76.7.3558–3563.2002, DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi: 10.1073pnas.0604993103).

[0257] In some embodiments, protein fusogens may be re-targeted by covalently conjugating a T cell binding agent to the attachment protein. In some embodiments, the fusogen and T cell binding agent are covalently conjugated by expression of a chimeric protein comprising the fusogen linked to the T cell binding agent (e.g., retargeted attachment protein). The T cell binding agent can include any targeting protein able to confer specific binding to a target molecule expressed on the surface of a T cell. In some embodiments, a targeting protein can also include an antibody or an antigen-binding fragment thereof (e.g., Fab, Fab', F(ab')2, Fv fragments, scFv antibody fragments, disulfide-linked Fvs (sdFv), a Fd fragment consisting of the VH and CH1 domains, linear antibodies, single domain antibodies such as sdAb (either VL or VH), nanobodies, or camelid VHH domains), an antigen-binding fibronectin type III (Fn3) scaffold such as a fibronectin polypeptide minibody, a ligand, a cytokine, a chemokine, or a T cell receptor (TCRs). In some embodiments, the T cell binding agent is an antibody or antigen binding fragment thereof. In some embodiments, the fusion protein can be engineered to bind the Fc region of an 72 sf-5966708186152009440 antibody that targets an antigen on a target cell, redirecting the fusion activity towards cells that display the antibody’s target (DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi:10.1038 / nm1192). In some embodiments, altered and non-altered fusogens may be displayed on the same retroviral vector or VLP (doi: 10.1016 / j.biomaterials.2014.01.051).

[0258] In some embodiments, a single-chain variable fragment (scFv) can be conjugated to fusogens to redirect fusion activity towards T cells that display the scFv binding target (doi:10.1038 / nbt1060, DOI 10.1182 / blood-2012-11-468579, doi:10.1038 / nmeth.1514, doi:10.1006 / mthe.2002.0550, HUMAN GENE THERAPY 11:817– 826, doi:10.1038 / nbt942, doi:10.1371 / journal.pone.0026381, DOI 10.1186 / s12896-015-0142-z). In some embodiments, designed ankyrin repeat proteins (DARPin) can be conjugated to fusogens to redirect fusion activity towards T cells that display the DARPin binding target (doi:10.1038 / mt.2013.16, doi:10.1038 / mt.2010.298, doi: 10.4049 / jimmunol.1500956), as well as combinations of different DARPins (doi:10.1038 / mto.2016.3). In some embodiments, a single domain antibody (e.g., a VHH) can be conjugated to fusogens to redirect fusion activity towards T cells that display the sdAb binding target. In some embodiments, receptor ligands and antigens can be conjugated to fusogens to redirect fusion activity towards T cells that display the target receptor (DOI: 10.1089 / hgtb.2012.054, DOI: 10.1128 / JVI.76.7.3558–3563.2002). i. CD3 Binding Agents

[0259] In some embodiments, the lipid particles disclosed herein comprise one or more retargeted attachment proteins, each independently comprising (i) a paramyxovirus envelope attachment protein; and (ii) a targeting moiety directed to a target molecule expressed on the surface of a target cell, wherein the target molecule is CD3. In some embodiments, the targeting moiety is a CD3 binding domain, e.g., a CD3 binding agent, such as any of those disclosed herein.

[0260] The lipid particles disclosed herein include, in some embodiments, one or more CD3 binding agents. For example, a CD3 binding agent may be fused to or incorporated in a retargeted attachment protein. In another embodiment, a CD3 binding agent may be incorporated into the lipid particle envelope via fusion with a transmembrane domain.

[0261] Exemplary CD3 binding agents include antibodies and fragments thereof (e.g., scFv, VHH) that bind to CD3. Such antibodies may be derived from any species, and may be for example, mouse, rabbit, human, humanized, or camelid antibodies.

[0262] Exemplary antibodies include OKT3, CRIS-7, I2C, blinatumomab, catumaxomab, muromonab-CD3, A-319, AFM11, AMG 199, AMG 211, AMG 424, AMG 427, AMG 562, AMG 564, APVO436, CC-93269, ERY974, GBR1302, GEM333, GEM2PSCA, GNC-035, HPN424, IGM-2323, JNJ-63709178, JNJ-63898081, JNJ-75348780, JNJ-78306358, M701, M802, MGD007, MOR209 / ES414, PF-06671008, REGN5459, RO7283420, SAR442257, SAR443216, TNB-383B, TNB- 486, TNB-585, Y150, acapatamab, cevostamab, cibisatamab, duvortuxizumab, eluvixtamab, 73 sf-5966708186152009440 emerfetamab, etevritamab, glofitamab, gresonitamab, obrindatamab, pavurutamab, plamotamab, solitomab, tarlatamab, tepoditamab, tidutamab, vibecotamab, vixtimotamab, alnuctamab, dafsolimab setaritox, pacanalotamab, pasotuxizumab, runimotamab, nivatrotamab, elranatamab, ertumaxomab, flotetuzumab, odronextamab, talquetamab, teclistamab, visilizumab, epcoritamab, otelixizumab, 3F8BiAb, CCW702, DKTK CC-1, EMB-06, GEN1044, GEN1047, GTB-3550, HPN217, IMC-C103C, NVG-111, REGN4018, REGN4336, REGN5458, A-2019, A-337, ABP-100, AFM15, AFM21, AMG 701, APVO425, CLN-049, Dow2, EM801, Ektomab, FBTA05, GBR1342, GBR1372, GSK3537142, HBM7020, HLX31, IGM-2644, MG1122, MGD015, ND003, ND007, PF-07062119, RO7293583, STA551, TT19, ZW38; and anti-CD3 antibodies disclosed in US Patent Nos.4361549, 7728114, 9657102, 9587021, and 11007267; US Patent Application Nos. US20120269826, US20180057597, and US20180112000; and PCT Application Nos. WO2005118635, WO2011050106, WO2012162067, WO2014047231, WO2016116626, WO2016180721, and WO2016204966. Other exemplary binding agents include designed ankyrin repeat proteins (DARPins) and binding agents based on fibronectin type III (Fn3) scaffolds.

[0263] In some embodiments, the CD3 binding agent comprises a heavy chain variable (VH) region comprising a CDR-H1, a CDRH-2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO:474, 475, and 476 respectively; and a light chain variable region comprising a CDR-L1, a CDR- L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO:477, 478, and 479, respectively. In some embodiments, the CD3 binding agent comprises a VH region comprising an amino acid sequence having at least about 90% sequence identity to the amino acid sequence set forth in SEQ ID NO:480, and a VL region comprising an amino acid sequence having at least about 90% sequence identity to the amino acid sequence set forth in SEQ ID NO:481. In some embodiments, the CD3 binding agent comprises a VH region comprising the amino acid sequence set forth in SEQ ID NO:480, and a VL region comprising the amino acid sequence set forth in SEQ ID NO:481. In some embodiments, the CD3 binding agent is an scFv. In some embodiments, the CD3 binding agent comprises the amino acid sequence set forth in SEQ ID NO:482. In some embodiments, the CD3 binding agent is OKT3.

[0264] In some embodiments, the CD3 binding agent is activating (e.g., the CD3 binding agent activates T cells). In some embodiments, the CD3 binding agent is non-activating (e.g., it does not activate T cells).

[0265] In some embodiments, a CD3 binding agent comprises a humanized antibody molecule, intact IgA, IgG, IgE or IgM antibody; bi- or multi- specific antibody (e.g., Zybodies®, etc.); antibody fragments such as Fab fragments, Fab’ fragments, F(ab’)2fragments, Fd’ fragments, Fd fragments, and isolated CDRs or sets thereof; single chain Fvs; polypeptide-Fc fusions; single domain antibodies (e.g., shark single domain antibodies such as IgNAR or fragments thereof); camelid antibodies; masked antibodies (e.g., Probodies®); Small Modular ImmunoPharmaceuticals (“SMIPsTM”); single chain or 74 sf-5966708186152009440 Tandem diabodies (TandAb®); VHHs; Anticalins®; Nanobodies®; minibodies; BiTE®s; ankyrin repeat proteins or DARPINs®; Avimers®; DARTs; TCR-like antibodies;, Adnectins®; Affilins®; Trans- bodies®; Affibodies®; TrimerX®; MicroProteins; Fynomers®, Centyrins®; and KALBITOR®s.

[0266] In some embodiments, the CD3 binding agent is a peptide. In some embodiments, the CD3 binding agent is an antibody, such as a single-chain variable fragment (scFv). In some embodiments, the CD3 binding agent is an antibody, such as a single domain antibody. In some embodiments, the antibody can be human or humanized. In some embodiments, the CD3 binding agent is a VHH. In some embodiments, the antibody or portion thereof is naturally occurring. In some embodiments, the antibody or portion thereof is synthetic.

[0267] In some embodiments, the antibody can be generated from phage display libraries to have specificity for a desired target ligand. In some embodiments, the phage display libraries are generated from a VHH repertoire of camelids immunized with various antigens, as described in Arbabi et al., FEBS Letters, 414, 521-526 (1997); Lauwereys et al., EMBO J., 17, 3512-3520 (1998); Decanniere et al., Structure, 7, 361-370 (1999). In some embodiments, the phage display library is generated comprising antibody fragments of a non-immunized camelid. In some embodiments, a library of human single domain antibodies is synthetically generated by introducing diversity into one or more scaffolds.

[0268] In some embodiments, the C-terminus of the CD3 binding agent is attached to the C- terminus of the G protein (e.g., fusogen) or biologically active portion thereof. In some embodiments, the N-terminus of the CD3 binding agent is exposed on the exterior surface of the lipid bilayer.

[0269] In some embodiments, the CD3 binding agent is the only surface displayed non-viral sequence of the viral vector. In some embodiments, the CD3 binding agent is the only membrane bound non-viral sequence of the viral vector. In some embodiments, the viral vector does not contain a molecule that engages or stimulates T cells other than the CD3 binding agent. In some embodiments, the viral vector contains a non-activating CD3 binding agent.

[0270] In some embodiments, viral vectors may display CD3 binding agents that are not conjugated to protein fusogens in order to redirect the fusion activity towards a cell that is bound by the targeting moiety, or to affect homing. ii. CD4 Binding Agents

[0271] In some embodiments, the lipid particles disclosed herein comprise one or more retargeted attachment proteins, each independently comprising (i) a paramyxovirus envelope attachment protein; and (ii) a targeting moiety directed to a target molecule expressed on the surface of a target cell, wherein the target molecule is CD4. In some embodiments, the targeting moiety is a CD4 binding domain, e.g., a CD4 binding agent, such as any of those disclosed herein.

[0272] The lipid particles disclosed herein include, in some embodiments, one or more CD4 binding agents. For example, a CD4 binding agent may be fused to or incorporated in a protein fusogen or 75 sf-5966708186152009440 attachment protein. In another embodiment, a CD4 binding agent may be incorporated into the lipid particle envelope via fusion with a transmembrane domain.

[0273] In some of any of the provided embodiments, the CD4 binding agent is exposed on the surface of the lipid particle. In some embodiments, the CD4 binding agent is fused to a transmembrane domain incorporated in the lipid particle envelope.

[0274] Exemplary CD4 binding agents include antibodies and fragments thereof (e.g., scFv, VHH) that bind to CD4. Such antibodies may be derived from any species, and may be for example, mouse, rabbit, human, humanized, or camelid antibodies. Exemplary antibodies include ibalizumab, zanolimumab, tregalizumab, priliximab, cedelizumab, clenoliximab, keliximab, and anti-CD4 antibodies disclosed in WO2002102853, WO2004083247, WO2004067554, WO2007109052, WO2008134046, WO2010074266, WO2012113348, WO2013188870, WO2017104735, WO2018035001, WO2018170096, WO2019203497, WO2019236684, WO2020228824, US 5,871,732, US 7,338,658, US 7,722,873, US 8,399,621, US 8,911,728, US 9,005,963,US 9,587,022, US 9,745,552, US provisional application no.63 / 326,269, US provisional application no.63 / 341,681; as well as antibodies B486A1, RPA-T4, CE9.1 (Novus Biologicals); GK1.5, RM4-5, RPA-T4 , OKT4, 4SM95, S3.5, N1UG0 (ThermoFisher); GTX50984, ST0488, 10B5, EP204 (GeneTex); GK1.3, 5A8, 10C12, W3 / 25, 8A5, 13B8.2, 6G5 (Absolute Antibody); VIT4, M-T466, M-T321, REA623, (Miltenyi); MEM115, MT310 (Enzo Life Sciences); H129.19, 5B4, 6A17, 18-46, A-1, C-1, OX68 (Santa Cruz); EP204, D2E6M (Cell Signaling Technology). Other exemplary binding agents include designed ankyrin repeat proteins (DARPins) (e.g., the anti-CD4 DARPin disclosed in WO2017182585) and binding agents based on fibronectin type III (Fn3) scaffolds. Each of US 9,005,963, US provisional application no.63 / 326,269, and US provisional application no.63 / 341,681 is incorporated by reference herein in its entirety.

[0275] In some embodiments, protein fusogens or attachment proteins may be re-targeted by mutating amino acid residues in a fusion protein or a targeting protein (e.g. the hemagglutinin (H) protein or G protein). In particular embodiments, the fusogen (e.g. G protein) is mutated to reduce binding for the native binding partner of the fusogen. In some embodiments, the fusogen is or contains a mutant G protein or a biologically active portion thereof that is a mutant of wild-type NiV-G and exhibits reduced binding to one or both of the native binding partners Ephrin B2 or Ephrin B3, including any as described above. Thus, in some aspects, a fusogen can be retargeted to display altered tropism. In some embodiments, the binding confers re-targeted binding compared to the binding of a wild-type surface glycoprotein protein in which a new or different binding activity is conferred. In particular embodiments, the binding confers re-targeted binding compared to the binding of a wild-type G protein in which a new or different binding activity is conferred. In some embodiments the fusogen is randomly mutated. In some embodiments the fusogen is rationally mutated. In some embodiments the fusogen is subjected to directed evolution. In some embodiments the fusogen is truncated and only a subset of the peptide is used 76 sf-5966708186152009440 in the viral vector. In some embodiments, amino acid residues in the measles hemagglutinin protein may be mutated to alter the binding properties of the protein, redirecting fusion (doi:10.1038 / nbt942, Molecular Therapy vol.16 no.8, 1427–1436 Aug.2008, doi:10.1038 / nbt1060, DOI: 10.1128 / JVI.76.7.3558–3563.2002, DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi: 10.1073pnas.0604993103).

[0276] In some embodiments, protein fusogens may be re-targeted by covalently conjugating a CD4 binding agent to the fusion protein or attachment protein (e.g. retargeted attachment protein). In some embodiments, the fusogen and CD4 binding agent are covalently conjugated by expression of a chimeric protein comprising the fusogen linked to the CD4 binding agent (e.g. retargeted attachment protein). In some embodiments, a single-chain variable fragment (scFv) can be conjugated to fusogens to redirect fusion activity towards cells that display the scFv binding target (doi:10.1038 / nbt1060, DOI 10.1182 / blood-2012-11-468579, doi:10.1038 / nmeth.1514, doi:10.1006 / mthe.2002.0550, HUMAN GENE THERAPY 11:817– 826, doi:10.1038 / nbt942, doi:10.1371 / journal.pone.0026381, DOI 10.1186 / s12896-015-0142-z). In some embodiments, designed ankyrin repeat proteins (DARPin) can be conjugated to fusogens to redirect fusion activity towards cells that display the DARPin binding target (doi:10.1038 / mt.2013.16, doi:10.1038 / mt.2010.298, doi: 10.4049 / jimmunol.1500956), as well as combinations of different DARPins (doi:10.1038 / mto.2016.3). In some embodiments, receptor ligands and antigens can be conjugated to fusogens to redirect fusion activity towards cells that display the target receptor (DOI: 10.1089 / hgtb.2012.054, DOI: 10.1128 / JVI.76.7.3558–3563.2002). In some embodiments, a targeting protein can also include an antibody or an antigen-binding fragment thereof (e.g., Fab, Fab', F(ab')2, Fv fragments, scFv antibody fragments, disulfide-linked Fvs (sdFv), a Fd fragment consisting of the VH and CH1 domains, linear antibodies, single domain antibodies such as sdAb (either VL or VH), nanobodies, or camelid VHH domains), an antigen-binding fibronectin type III (Fn3) scaffold such as a fibronectin polypeptide minibody, a ligand, a cytokine, a chemokine, or a T cell receptor (TCRs). In some embodiments, protein fusogens may be re-targeted by non-covalently conjugating a CD4 binding agent to the fusion protein or targeting protein (e.g. retargeted attachment protein)). In some embodiments, the fusion protein can be engineered to bind the Fc region of an antibody that targets an antigen on a target cell, redirecting the fusion activity towards cells that display the antibody’s target (DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi:10.1038 / nm1192). In some embodiments, altered and non-altered fusogens may be displayed on the same retroviral vector or VLP (doi: 10.1016 / j.biomaterials.2014.01.051).

[0277] In some embodiments, a CD4 binding agent comprises a humanized antibody molecule, intact IgA, IgG, IgE or IgM antibody; bi- or multi- specific antibody (e.g., Zybodies®, etc.); antibody fragments such as Fab fragments, Fab’ fragments, F(ab’)2fragments, Fd’ fragments, Fd fragments, and isolated CDRs or sets thereof; single chain Fvs; polypeptide-Fc fusions; single domain antibodies (e.g., 77 sf-5966708186152009440 shark single domain antibodies such as IgNAR or fragments thereof); camelid antibodies; masked antibodies (e.g., Probodies®); Small Modular ImmunoPharmaceuticals (“SMIPsTM”); single chain or Tandem diabodies (TandAb®); VHHs; Anticalins®; Nanobodies®; minibodies; BiTE®s; ankyrin repeat proteins or DARPINs®; Avimers®; DARTs; TCR-like antibodies;, Adnectins®; Affilins®; Trans- bodies®; Affibodies®; TrimerX®; MicroProteins; Fynomers®, Centyrins®; and KALBITOR®s.

[0278] In some embodiments, the CD4 binding agent is a peptide. In some embodiments, the CD4 binding agent is an antibody, such as a single-chain variable fragment (scFv). In some embodiments, the CD4 binding agent is an antibody, such as a single domain antibody. In some embodiments, the antibody can be human or humanized. In some embodiments, the CD4 binding agent is a VHH. In some embodiments, the antibody or portion thereof is naturally occurring. In some embodiments, the antibody or portion thereof is synthetic.

[0279] In some embodiments, the antibody can be generated from phage display libraries to have specificity for a desired target ligand. In some embodiments, the phage display libraries are generated from a VHH repertoire of camelids immunized with various antigens, as described in Arbabi et al., FEBS Letters, 414, 521-526 (1997); Lauwereys et al., EMBO J., 17, 3512-3520 (1998); Decanniere et al., Structure, 7, 361-370 (1999). In some embodiments, the phage display library is generated comprising antibody fragments of a non-immunized camelid. In some embodiments, a library of human single domain antibodies is synthetically generated by introducing diversity into one or more scaffolds.

[0280] In some embodiments, the C-terminus of the CD4 binding agent is attached to the C- terminus of the G protein (e.g., fusogen) or biologically active portion thereof. In some embodiments, the N-terminus of the CD4 binding agent is exposed on the exterior surface of the lipid bilayer.

[0281] In some embodiments, the CD4 binding agent is the only surface displayed non-viral sequence of the lipid particle. In some embodiments, the CD4 binding agent is the only membrane bound non-viral sequence of the lipid particle. In some embodiments, the lipid particle does not contain a molecule that engages or stimulates T cells other than the CD4 binding agent.

[0282] In some embodiments, lipid particles may display CD4 binding agents that are not conjugated to protein fusogens in order to redirect the fusion activity towards a cell that is bound by the targeting moiety, or to affect homing.

[0283] In some embodiments, a protein fusogen derived from a virus or organism that do not infect humans does not have a natural fusion targets in patients, and thus has high specificity.

[0284] In some of any of the provided embodiments, the CD4 binding agent is an anti-CD4 antibody or an antigen-binding fragment. In some of any of the provided embodiments, the anti-CD4 antibody or antigen-binding fragment is mouse, rabbit, human, or humanized. In some embodiments, the antigen- binding fragment is a single chain variable fragment (scFv). In some embodiments, the antigen-binding fragment is an anti-CD4 scFv. 78 sf-5966708186152009440

[0285] In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 260, 261, and 262, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 263, 264, and 265, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 260, 261, and 262, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 263, 264, and 265, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 266, 267, and 268, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 269, 270, and 265, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 266, 267, and 268, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 269, 270, and 265, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 271, 272, and 268, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 269, 270, and 265, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 271, 272, and 268, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 269, 270, and 265, respectively. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:273. In some embodiments, the anti-CD4 scFv comprises a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:274. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:273; and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:274. In some embodiments, the VH and VL are joined by a linker. In some embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO:275. In some embodiments, the anti- CD4 scFv comprises the amino acid sequence set forth in SEQ ID NO:276.

[0286] In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 277, 278, and 279, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 280, 281, and 282, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 277, 278, and 279, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 79 sf-5966708186152009440 comprising the amino acid sequence set forth in SEQ ID NO: 280, 281, and 282, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 283, 284, and 285, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 286, 287, and 288, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 283, 284, and 285, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 286, 287, and 288, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 289, 290, and 285, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 286, 287, and 282, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 289, 290, and 285, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 286, 287, and 282, respectively. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:291. In some embodiments, the anti-CD4 scFv comprises a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:292. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:291; and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:292. In some embodiments, the VH and VL are joined by a linker. In some embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO:275. In some embodiments, the anti- CD4 scFv comprises the amino acid sequence set forth in SEQ ID NO:293.

[0287] In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 294, 295, and 296, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 297, 298, and 299, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 294, 295, and 296, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 297, 298, and 299, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 300, 301, 302, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 303, 304, and 299, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ 80 sf-5966708186152009440 ID NO: 300, 301, 302, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 303, 304, and 299, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 305, 306, 306, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 303, 304, and 299, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 305, 306, 302, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 224, 225, and 172, respectively. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:307. In some embodiments, the anti-CD4 scFv comprises a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:308. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:307; and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:308. In some embodiments, the VH and VL are joined by a linker. In some embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO:275. In some embodiments, the anti-CD4 scFv comprises the amino acid sequence set forth in SEQ ID NO:309.

[0288] In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 310, 311, and 312, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 313, 314, and 315, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 310, 311, and 312, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 313, 314, and 315, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 316, 317, 318, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 319, 320, and 315, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 316, 317, 318, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 319, 320, and 315, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 321, 322, 318, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 319, 321, and 315, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, 81 sf-5966708186152009440 and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 321, 322, 318, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 319, 320, and 323, respectively. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:323. In some embodiments, the anti-CD4 scFv comprises a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:324. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:323; and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:324. In some embodiments, the VH and VL are joined by a linker. In some embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO:275. In some embodiments, the anti-CD4 scFv comprises the amino acid sequence set forth in SEQ ID NO:325.

[0289] In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 326, 327, and 328, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 329, 330, and 331, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 326, 327, and 328, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 329, 330, and 331, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 332, 333, and 334, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 335, 336, and 331, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 332, 333, and 334, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 335, 336, and 331, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 337, 338, and 334, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 335, 336, and 331, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 337, 338, and 334, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 335, 336, and 331, respectively. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:339. In some embodiments, the anti-CD4 scFv comprises a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:340. In some embodiments, the anti-CD4 82 sf-5966708186152009440 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:339; and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:340. In some embodiments, the VH and VL are joined by a linker. In some embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO:275. In some embodiments, the anti- CD4 scFv comprises the amino acid sequence set forth in SEQ ID NO:341.

[0290] In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 342, 343, and 344, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 345, 346, and 347, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 342, 343, and 344, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 345, 346, and 347, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 348, 349, and 350, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 351, 352, and 347, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 242, 243, and 244, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 245, 246, and 198, respectively. In some embodiments, the anti- CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 353, 354, and 350, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 351, 353, and 347, respectively. In some embodiments, the anti-CD4 scFv comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 353, 354, and 350, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 351, 352, and 347, respectively. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:355. In some embodiments, the anti-CD4 scFv comprises a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:356. In some embodiments, the anti-CD4 scFv comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:355; and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:356. In some embodiments, the VH and VL are joined by a linker. In some embodiments, the linker comprises the amino acid sequence set forth in SEQ ID NO:275. In some embodiments, the anti- CD4 scFv comprises the amino acid sequence set forth in SEQ ID NO:357. 83 sf-5966708186152009440

[0291] In some embodiments, the anti-CD4 antibody or antigen-binding fragment is a single domain antibody. In some embodiments, the anti-CD4 antibody or antigen-binding fragment is a camelid (e.g. llama, alpaca, camel) anti-CD4 antibody or antigen-binding fragment (e.g. VHH). In some embodiments, the anti-CD4 antibody or antigen-binding fragment is an anti-CD4 VHH. In some embodiments, the anti- CD4 VHH comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 358, 359, and 360, respectively. In some embodiments, the anti-CD4 VHH comprises a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 361, 362, and 363, respectively. In some embodiments, the anti-CD4 VHH comprises a CDR- H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequence set forth in SEQ ID NO: 364, 365, and 363, respectively. In some embodiments, the anti-CD4 VHH comprises the amino acid sequence set forth in SEQ ID NO:366. iii. CD7 Binding Agents

[0292] In some embodiments, the lipid particles disclosed herein comprise one or more retargeted attachment proteins, each independently comprising (i) a paramyxovirus envelope attachment protein; and (ii) a targeting moiety directed to a target molecule expressed on the surface of a target cell, wherein the target molecule is CD7. In some embodiments, the targeting moiety is a CD7 binding domain, e.g., a CD7 binding agent, such as any of those disclosed herein.

[0293] The lipid particles disclosed herein include, in some embodiments, one or more CD7 binding agents. For example, a CD7 binding agent may be fused to or incorporated in a protein fusogen or attachment protein. In another embodiment, a CD7 binding agent may be incorporated into the lipid particle envelope via fusion with a transmembrane domain.

[0294] Exemplary CD7 binding agents include antibodies and fragments thereof (e.g., scFv, VHH) that bind to CD7. Such antibodies may be derived from any species, and may be for example, mouse, rabbit, human, humanized, or camelid antibodies. Exemplary antibodies include grsinilimab, SPV-T3a and those disclosed in WO2015 / 184941; US10106609; WO2017 / 213979; WO2018 / 098306; WO2019086534; US11447548; WO2019 / 102234; WO2022 / 136887; WO2022 / 136888; WO2020 / 212710; WO2021 / 160267; WO2022 / 095803; WO2022 / 151851. Further exemplary anti-CD7 binding agents and G proteins are described in U.S. provisional application No.63 / 172,518, which is incorporated by reference herein. Other exemplary binding agents include designed ankyrin repeat proteins (DARPins) and binding agents based on fibronectin type III (Fn3) scaffolds.

[0295] In some embodiments, protein fusogens or attachment proteins may be re-targeted by mutating amino acid residues in a fusion protein or a targeting protein (e.g. retargeted attachment protein). In particular embodiments, the fusogen (e.g. G protein) is mutated to reduce binding for the native binding partner of the fusogen. In some embodiments, the fusogen is or contains a mutant G protein or a biologically active portion thereof that is a mutant of wild-type NiV-G and exhibits reduced 84 sf-5966708186152009440 binding to one or both of the native binding partners Ephrin B2 or Ephrin B3, including any as described above. Thus, in some aspects, a fusogen can be retargeted to display altered tropism. In some embodiments, the binding confers re-targeted binding compared to the binding of a wild-type surface glycoprotein protein in which a new or different binding activity is conferred. In particular embodiments, the binding confers re-targeted binding compared to the binding of a wild-type G protein in which a new or different binding activity is conferred. In some embodiments the fusogen is randomly mutated. In some embodiments the fusogen is rationally mutated. In some embodiments the fusogen is subjected to directed evolution. In some embodiments the fusogen is truncated and only a subset of the peptide is used in the viral vector. In some embodiments, amino acid residues in the measles hemagglutinin protein may be mutated to alter the binding properties of the protein, redirecting fusion (doi:10.1038 / nbt942, Molecular Therapy vol.16 no.8, 1427–1436 Aug.2008, doi:10.1038 / nbt1060, DOI: 10.1128 / JVI.76.7.3558–3563.2002, DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi: 10.1073pnas.0604993103).

[0296] In some embodiments, protein fusogens (e.g., attachment proteins) may be re-targeted by covalently conjugating a CD7 binding agent to the fusion protein or attachment protein (e.g. retargeted attachment protein). In some embodiments, the fusogen and CD7 binding agent are covalently conjugated by expression of a chimeric protein comprising the fusogen linked to the CD8 binding agent. In some embodiments, a single-chain variable fragment (scFv) can be conjugated to fusogens to redirect fusion activity towards cells that display the scFv binding target (doi:10.1038 / nbt1060, DOI 10.1182 / blood-2012-11-468579, doi:10.1038 / nmeth.1514, doi:10.1006 / mthe.2002.0550, HUMAN GENE THERAPY 11:817– 826, doi:10.1038 / nbt942, doi:10.1371 / journal.pone.0026381, DOI 10.1186 / s12896-015-0142-z). In some embodiments, designed ankyrin repeat proteins (DARPin) can be conjugated to fusogens to redirect fusion activity towards cells that display the DARPin binding target (doi:10.1038 / mt.2013.16, doi:10.1038 / mt.2010.298, doi: 10.4049 / jimmunol.1500956), as well as combinations of different DARPins (doi:10.1038 / mto.2016.3). In some embodiments, receptor ligands and antigens can be conjugated to fusogens to redirect fusion activity towards cells that display the target receptor (DOI: 10.1089 / hgtb.2012.054, DOI: 10.1128 / JVI.76.7.3558–3563.2002). In some embodiments, a targeting protein can also include an antibody or an antigen-binding fragment thereof (e.g., Fab, Fab', F(ab')2, Fv fragments, scFv antibody fragments, disulfide-linked Fvs (sdFv), a Fd fragment consisting of the VH and CH1 domains, linear antibodies, single domain antibodies such as sdAb (either VL or VH), nanobodies, or camelid VHH domains), an antigen-binding fibronectin type III (Fn3) scaffold such as a fibronectin polypeptide minibody, a ligand, a cytokine, a chemokine, or a T cell receptor (TCRs). In some embodiments, protein fusogens may be re-targeted by non-covalently conjugating a CD7 binding agent to the fusion protein or targeting protein (e.g. the hemagglutinin protein). In some embodiments, the fusion protein can be engineered to bind the Fc region of an antibody that targets an antigen on a 85 sf-5966708186152009440 target cell, redirecting the fusion activity towards cells that display the antibody’s target (DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi:10.1038 / nm1192). In some embodiments, altered and non- altered fusogens may be displayed on the same retroviral vector or VLP (doi: 10.1016 / j.biomaterials.2014.01.051).

[0297] In some embodiments, a CD7 binding agent comprises a humanized antibody molecule, intact IgA, IgG, IgE or IgM antibody; bi- or multi- specific antibody (e.g., Zybodies®, etc.); antibody fragments such as Fab fragments, Fab’ fragments, F(ab’)2fragments, Fd’ fragments, Fd fragments, and isolated CDRs or sets thereof; single chain Fvs; polypeptide-Fc fusions; single domain antibodies (e.g., shark single domain antibodies such as IgNAR or fragments thereof); cameloid antibodies; masked antibodies (e.g., Probodies®); Small Modular ImmunoPharmaceuticals (“SMIPsTM”); single chain or Tandem diabodies (TandAb®); VHHs; Anticalins®; Nanobodies®; minibodies; BiTE®s; ankyrin repeat proteins or DARPINs®; Avimers®; DARTs; TCR-like antibodies;, Adnectins®; Affilins®; Trans- bodies®; Affibodies®; TrimerX®; MicroProteins; Fynomers®, Centyrins®; and KALBITOR®s.

[0298] In some embodiments, the CD7 binding agent is a peptide. In some embodiments, the CD7 binding agent is an antibody, such as a single-chain variable fragment (scFv). In some embodiments, the CD7 binding agent is an antibody, such as a single domain antibody. In some embodiments, the CD7 binding agent is a VHH. In some embodiments, the antibody can be human or humanized. In some embodiments, the antibody or portion thereof is naturally occurring. In some embodiments, the antibody or portion thereof is synthetic.

[0299] In some embodiments, the antibody can be generated from phage display libraries to have specificity for a desired target ligand. In some embodiments, the phage display libraries are generated from a VHH repertoire of camelids immunized with various antigens, as described in Arbabi et al., FEBS Letters, 414, 521-526 (1997); Lauwereys et al., EMBO J., 17, 3512-3520 (1998); Decanniere et al., Structure, 7, 361-370 (1999). In some embodiments, the phage display library is generated comprising antibody fragments of a non-immunized camelid. In some embodiments, a library of human single domain antibodies is synthetically generated by introducing diversity into one or more scaffolds.

[0300] In some embodiments, the C-terminus of the CD7 binding agent is attached to the C- terminus of the G protein (e.g., fusogen) or biologically active portion thereof. In some embodiments, the N-terminus of the CD7 binding agent is exposed on the exterior surface of the lipid bilayer.

[0301] In some embodiments, the CD7 binding agent is the only surface displayed non-viral sequence of the viral vector. In some embodiments, the CD7 binding agent is the only membrane bound non-viral sequence of the viral vector. In some embodiments, the viral vector does not contain a molecule that engages or stimulates T cells other than the CD7 binding agent. 86 sf-5966708186152009440

[0302] In some embodiments, viral vectors may display CD7 binding agents that are not conjugated to protein fusogens in order to redirect the fusion activity towards a cell that is bound by the targeting moiety, or to affect homing. iv. CD8 Binding Agents

[0303] In some embodiments, the lipid particles disclosed herein comprise one or more retargeted attachment proteins, each independently comprising (i) a paramyxovirus envelope attachment protein; and (ii) a targeting moiety directed to a target molecule expressed on the surface of a target cell, wherein the target molecule is CD8. In some embodiments, the targeting moiety is a CD8 binding domain, e.g., a CD8 binding agent, such as any of those disclosed herein.

[0304] The lipid particles disclosed herein include, in some embodiments, one or more CD8 binding agents. For example, a CD8 binding agent may be fused to or incorporated in a protein fusogen or attachment protein. In another embodiment, a CD8 binding agent may be incorporated into the lipid particle envelope via fusion with a transmembrane domain.

[0305] Exemplary CD8 binding agents include antibodies and fragments thereof (e.g., scFv, VHH) that bind to one or more of CD8 alpha and CD8 beta. Such antibodies may be derived from any species, and may be for example, mouse, rabbit, human, humanized, or camelid antibodies. Exemplary antibodies include those disclosed in WO2014025828, WO2014164553, WO2020069433, WO2015184203, US20160176969, WO2017134306, WO2019032661, WO2020257412, WO2018170096, WO2020060924, US10730944, US20200172620, and the non-human antibodies OKT8; RPA-T8, 12.C7 (Novus); 17D8, 3B5, LT8, RIV11, SP16, YTC182.20, MEM-31, MEM-87, RAVB3, C8 / 144B (Thermo Fisher); 2ST8.5H7, Bu88, 3C39, Hit8a, SPM548, CA-8, SK1, RPA-T8 (GeneTex); UCHT4 (Absolute Antibody); BW135 / 80 (Miltenyi); G42-8 (BD Biosciences); C8 / 1779R, mAB 104 (Enzo Life Sciences); B-Z31 (Sapphire North America); 32-M4, 5F10, MCD8, UCH-T4, 5F2 (Santa Cruz); D8A8Y, RPA-T8 (Cell Signaling Technology). Further exemplary anti-CD8 binding agents and G proteins are described in U.S. provisional application No.63 / 172,518, which is incorporated by reference herein. Other exemplary binding agents include designed ankyrin repeat proteins (DARPins) and binding agents based on fibronectin type III (Fn3) scaffolds.

[0306] In some embodiments, the CD8 binding agent comprises a CDR-H1, a CDR-H2, and a CDR- H3 comprising the amino acid sequence set forth in SEQ ID NO: 483, 484, and 485, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 486, 487, and 488, respectively. In some embodiments, the CD8 binding agent comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:369, and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:370. In some embodiments, the CD8 binding agent comprises the sequence set forth in SEQ ID NO:489. 87 sf-5966708186152009440

[0307] In some embodiments, the CD8 binding agent comprises a CDR-H1, a CDR-H2, and a CDR- H3 comprising the amino acid sequence set forth in SEQ ID NO: 490, 491, and 492, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 493, 494, and 495, respectively. In some embodiments, the CD8 binding agent comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:371 and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:372. In some embodiments, the CD8 binding agent comprises the sequence set forth in SEQ ID NO:496.

[0308] In some embodiments, the CD8 binding agent comprises a CDR-H1, a CDR-H2, and a CDR- H3 comprising the amino acid sequence set forth in SEQ ID NO: 497, 498, and 499, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 486, 487, and 500, respectively. In some embodiments, the CD8 binding agent comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:373, and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:374. In some embodiments, the CD8 binding agent comprises the sequence set forth in SEQ ID NO:501.

[0309] In some embodiments, the CD8 binding agent comprises a CDR-H1, a CDR-H2, and a CDR- H3 comprising the amino acid sequence set forth in SEQ ID NO: 502, 503, and 504, respectively; and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequence set forth in SEQ ID NO: 505, 506, and 507, respectively. In some embodiments, the CD8 binding agent comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:375, and a light chain variable region (VL) comprising the amino acid sequence set forth in SEQ ID NO:376. In some embodiments, the CD8 binding agent comprises the sequence set forth in SEQ ID NO:508.

[0310] In some embodiments, the CD8 binding agent comprises a CDR-H1, a CDR-H2, and a CDR- H3 comprising the amino acid sequence set forth in SEQ ID NO: 509, 510, and 511, respectively. In some embodiments, the CD8 binding agent comprises a heavy chain variable region (VH) comprising the amino acid sequence set forth in SEQ ID NO:377. In some embodiments, the CD8 binding agent comprises the sequence set forth in SEQ ID NO:377.

[0311] In some embodiments, the CD8 binding agent comprises any CD8 binding agent as described in US 2019 / 0144885, incorporated by reference herein in its entirety.

[0312] In some embodiments, the CD8 binding agent is an scFv that contains a VH and VL set forth from any as below, in which the VH and VL are separated by linker. In some embodiments, the CD8 binding agent is a VHH having the sequence set forth below. In some embodiments, the CD8 binding agent is linked to the C-terminus of a truncated NiV-G set forth in SEQ ID NO: 19 to provide a re- targeted NiV-G. In some embodiments, the retargeted NiV-G is pseudotyped on a lentiviral vector with the a NiV-F (e.g. set forth in SEQ ID NO:227). In some embodiments, the lentiviral vector further contains a payload gene encoding an anti-CD19 CAR. In some embodiments, the anti-CD19 CAR 88 sf-5966708186152009440 contains an anti-CD19 FMC63 scFv binding domain set forth in SEQ ID NO:239, a CD8 hinge set forth in SEQ ID NO:367, a CD8 transmembrane domain set forth in SEQ ID NO: 368, a 4-1bb signaling domain set forth in SEQ ID NO:248. a CD3zeta signaling domain set forth in SEQ ID NO: 249.

[0313] CD8_1 VH (SEQ ID NO.: 369): QVQLVQSGAEVKKPGASVKVSCKASGGTFSSYAISWVRQAPGQGLEWMGIIDPSDGNTNYAQN FQGRVTMTRDTSTSTVYMELSSLRSEDTAVYYCAKERAAAGYYYYMDVWGQGTTVTVSS VL (SEQ ID NO.: 370): DIQMTQSPSSLSASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYAASSLQSGVPSRFSGSG SGTDFTLTISSLQPEDFATYYCQQSYSTPLTFGGGTKVEIKR

[0314] CD8_2 VH (SEQ ID NO.:371): QVQLVQSGAEVKKPGASVKVSCKASGYTFTDYYIQWVRQAPGQGLEWMGWINPNSGGTSYAQ KFQGRVTMTRDTSTSTVYMELSSLRSEDTAVYYCAKEGDYYYGMDAWGQGTMVTVSS VL (SEQ ID NO.:372): DIVMTQSPLSLPVTPGEPASISCRSSQSLLHSNGYNYLDWYLQKPGQSPQLLIYLGSNRASGVPD RFSGSGSGTDFTLKISRVEAEDVGVYYCMQGLQTPHTFGQGTKVEIKR

[0315] CD8_3 VH (SEQ ID NO.:373): QVQLVQSGAEVKKPGASVKVSCKASGYTFTSYYMHWVRQAPGQGLEWMGGFDPEDGETIYA QKFQGRVTMTRDTSTSTVYMELSSLRSEDTAVYYCARDQGWGMDVWGQGTTVTVSS VL(SEQ ID NO.:374): DIQMTQSPSSLSASVGDRVTITCRASQSISSYLNWYQQKPGKAPKLLIYAASSLQSGVPSRFSGSG SGTDFTLTISSLQPEDFATYYCQQTYSTPYTFGQGTKLEIKR

[0316] CD8_4 VH (SEQ ID NO.:375): QVQLVQSGAEVKKPGASVKVSCKASGYTFTNHYMHWVRQAPGQGLEWMGWMNPNSGNTGY AQKFQGRVTMTRDTSTSTVYMELSSLRSEDTAVYYCASSESGSDLDYWGQGTLVTVSS VL (SEQ ID NO.:376): DIQMTQSPSSLSASVGDRVTITCRASQTIGNYVNWYQQKPGKAPKLLIYGASNLHTGVPSRFSGS GSGTDFTLTISSLQPEDFATYYCQQTYSAPLTFGGGTKVEIKR

[0317] In some embodiments, the CD8 binding agent is VHH set forth as: VHH (SEQ ID NO.:377): QVQLVESGGGLVQAGGSLRLSCAASGRTFSGYVMGWFRQAPGKQRKFVAAISRGGLSTSYADS VKGRFTISRDNAKNTVFLQMNTLKPEDTAVYYCAADRSDLYEITAASNIDSWGQGTLVTVSS 89 sf-5966708186152009440

[0318] In some embodiments, protein fusogens or attachment proteins may be re-targeted by mutating amino acid residues in a fusion protein or a targeting protein (e.g. retargeted attachment protein). In particular embodiments, the fusogen (e.g. G protein) is mutated to reduce binding for the native binding partner of the fusogen. In some embodiments, the fusogen is or contains a mutant G protein or a biologically active portion thereof that is a mutant of wild-type NiV-G and exhibits reduced binding to one or both of the native binding partners Ephrin B2 or Ephrin B3, including any as described above. Thus, in some aspects, a fusogen can be retargeted to display altered tropism. In some embodiments, the binding confers re-targeted binding compared to the binding of a wild-type surface glycoprotein protein in which a new or different binding activity is conferred. In particular embodiments, the binding confers re-targeted binding compared to the binding of a wild-type G protein in which a new or different binding activity is conferred. In some embodiments the fusogen is randomly mutated. In some embodiments the fusogen is rationally mutated. In some embodiments the fusogen is subjected to directed evolution. In some embodiments the fusogen is truncated and only a subset of the peptide is used in the viral vector. In some embodiments, amino acid residues in the measles hemagglutinin protein may be mutated to alter the binding properties of the protein, redirecting fusion (doi:10.1038 / nbt942, Molecular Therapy vol.16 no.8, 1427–1436 Aug.2008, doi:10.1038 / nbt1060, DOI: 10.1128 / JVI.76.7.3558–3563.2002, DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi: 10.1073pnas.0604993103).

[0319] In some embodiments, protein fusogens (e.g., attachment proteins) may be re-targeted by covalently conjugating a CD8 binding agent to the fusion protein or attachment protein (e.g. retargeted attachment protein). In some embodiments, the fusogen and CD8 binding agent are covalently conjugated by expression of a chimeric protein comprising the fusogen linked to the CD8 binding agent. In some embodiments, a single-chain variable fragment (scFv) can be conjugated to fusogens to redirect fusion activity towards cells that display the scFv binding target (doi:10.1038 / nbt1060, DOI 10.1182 / blood-2012-11-468579, doi:10.1038 / nmeth.1514, doi:10.1006 / mthe.2002.0550, HUMAN GENE THERAPY 11:817– 826, doi:10.1038 / nbt942, doi:10.1371 / journal.pone.0026381, DOI 10.1186 / s12896-015-0142-z). In some embodiments, designed ankyrin repeat proteins (DARPin) can be conjugated to fusogens to redirect fusion activity towards cells that display the DARPin binding target (doi:10.1038 / mt.2013.16, doi:10.1038 / mt.2010.298, doi: 10.4049 / jimmunol.1500956), as well as combinations of different DARPins (doi:10.1038 / mto.2016.3). In some embodiments, receptor ligands and antigens can be conjugated to fusogens to redirect fusion activity towards cells that display the target receptor (DOI: 10.1089 / hgtb.2012.054, DOI: 10.1128 / JVI.76.7.3558–3563.2002). In some embodiments, a targeting protein can also include an antibody or an antigen-binding fragment thereof (e.g., Fab, Fab', F(ab')2, Fv fragments, scFv antibody fragments, disulfide-linked Fvs (sdFv), a Fd fragment consisting of the VH and CH1 domains, linear antibodies, single domain antibodies such as sdAb (either VL or VH), 90 sf-5966708186152009440 nanobodies, or camelid VHH domains), an antigen-binding fibronectin type III (Fn3) scaffold such as a fibronectin polypeptide minibody, a ligand, a cytokine, a chemokine, or a T cell receptor (TCRs). In some embodiments, protein fusogens may be re-targeted by non-covalently conjugating a CD8 binding agent to the fusion protein or targeting protein (e.g. the hemagglutinin protein). In some embodiments, the fusion protein can be engineered to bind the Fc region of an antibody that targets an antigen on a target cell, redirecting the fusion activity towards cells that display the antibody’s target (DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi:10.1038 / nm1192). In some embodiments, altered and non- altered fusogens may be displayed on the same retroviral vector or VLP (doi: 10.1016 / j.biomaterials.2014.01.051).

[0320] In some embodiments, a CD8 binding agent comprises a humanized antibody molecule, intact IgA, IgG, IgE or IgM antibody; bi- or multi- specific antibody (e.g., Zybodies®, etc.); antibody fragments such as Fab fragments, Fab’ fragments, F(ab’)2 fragments, Fd’ fragments, Fd fragments, and isolated CDRs or sets thereof; single chain Fvs; polypeptide-Fc fusions; single domain antibodies (e.g., shark single domain antibodies such as IgNAR or fragments thereof); cameloid antibodies; masked antibodies (e.g., Probodies®); Small Modular ImmunoPharmaceuticals (“SMIPsTM”); single chain or Tandem diabodies (TandAb®); VHHs; Anticalins®; Nanobodies®; minibodies; BiTE®s; ankyrin repeat proteins or DARPINs®; Avimers®; DARTs; TCR-like antibodies;, Adnectins®; Affilins®; Trans- bodies®; Affibodies®; TrimerX®; MicroProteins; Fynomers®, Centyrins®; and KALBITOR®s.

[0321] In some embodiments, the CD8 binding agent is a peptide. In some embodiments, the CD8 binding agent is an antibody, such as a single-chain variable fragment (scFv). In some embodiments, the CD8 binding agent is an antibody, such as a single domain antibody. In some embodiments, the CD8 binding agent is a VHH. In some embodiments, the antibody can be human or humanized. In some embodiments, the antibody or portion thereof is naturally occurring. In some embodiments, the antibody or portion thereof is synthetic.

[0322] In some embodiments, the antibody can be generated from phage display libraries to have specificity for a desired target ligand. In some embodiments, the phage display libraries are generated from a VHH repertoire of camelids immunized with various antigens, as described in Arbabi et al., FEBS Letters, 414, 521-526 (1997); Lauwereys et al., EMBO J., 17, 3512-3520 (1998); Decanniere et al., Structure, 7, 361-370 (1999). In some embodiments, the phage display library is generated comprising antibody fragments of a non-immunized camelid. In some embodiments, a library of human single domain antibodies is synthetically generated by introducing diversity into one or more scaffolds.

[0323] In some embodiments, the C-terminus of the CD8 binding agent is attached to the C- terminus of the G protein (e.g., fusogen) or biologically active portion thereof. In some embodiments, the N-terminus of the CD8 binding agent is exposed on the exterior surface of the lipid bilayer. 91 sf-5966708186152009440

[0324] In some embodiments, the CD8 binding agent is the only surface displayed non-viral sequence of the viral vector. In some embodiments, the CD8 binding agent is the only membrane bound non-viral sequence of the viral vector. In some embodiments, the viral vector does not contain a molecule that engages or stimulates T cells other than the CD8 binding agent.

[0325] In some embodiments, viral vectors may display CD8 binding agents that are not conjugated to protein fusogens in order to redirect the fusion activity towards a cell that is bound by the targeting moiety, or to affect homing.

[0326] Non-limiting examples of re-targeted fusogens comprising a CD8 binding agent are as described in US 11,535,869, the entire contents of which is incorporated by reference herein. b. HSC Binding Domains

[0327] In some embodiments, the lipid particles disclosed herein comprise one or more retargeted attachment proteins, each independently comprising (i) a paramyxovirus envelope attachment protein; and (ii) a targeting moiety directed to a target molecule expressed on the surface of a target cell. In some embodiments, the targeting moiety is an HSC binding domain, e.g., an HSC binding agent, such as any of those disclosed herein.

[0328] The lipid particles disclosed herein include, in some embodiments, one or more HSC binding domains (e.g., HSC binding agent) that target the viral vector to a cell that is an HSC. In some embodiments, the HSC binding agent binds to a molecule expressed on the surface of the HSC. The cell surface molecule may be a receptor, coreceptor, or a GPI-anchored protein. In some embodiments, the HSC binding agent binds ASCT2, CD105, CD110, CD117, CD133, CD146, CD164, CD34, CD46, CD49f, CD90, EPCR,or ITGA3. In some embodiments, a HSC binding agent may be fused to or incorporated in a protein fusogen or lipid particle envelope attachment protein (e.g., a retargeted attachment protein). In some embodiments, a HSC binding agent may be incorporated into the viral envelope via fusion with a transmembrane domain. In some embodiments, the HSC binding agent targets the lipid particle to a HSC.

[0329] In particular embodiments, a HSC binding agent may be fused to or incorporated in a protein fusogen or attachment protein, thereby retargeting the lipid particle to a HSC. In some embodiments, for re-targeting the HSC binding agent is fused to a protein fusogen or envelope attachment protein that is mutated to reduce binding for the native binding partner of the fusogen or viral envelope protein. In some embodiments, the fusogen is or contains a mutant G protein or a biologically active portion thereof that is a mutant of wild-type NiV-G and exhibits reduced binding to one or both of the native binding partners Ephrin B2 or Ephrin B3, including any as described above. Thus, in some aspects, a fusogen can be retargeted to display altered tropism. In some embodiments, the binding confers re-targeted binding compared to the binding of a wild-type surface glycoprotein protein in which a new or different binding 92 sf-5966708186152009440 activity is conferred. In particular embodiments, the binding confers re-targeted binding compared to the binding of a wild-type G protein in which a new or different binding activity is conferred. In some embodiments the fusogen is randomly mutated. In some embodiments the fusogen is rationally mutated. In some embodiments the fusogen is subjected to directed evolution. In some embodiments the fusogen is truncated and only a subset of the peptide is used in the viral vector. In some embodiments, amino acid residues in the measles hemagglutinin protein may be mutated to alter the binding properties of the protein, redirecting fusion (doi:10.1038 / nbt942, Molecular Therapy vol.16 no.8, 1427–1436 Aug.2008, doi:10.1038 / nbt1060, DOI: 10.1128 / JVI.76.7.3558–3563.2002, DOI: 10.1128 / JVI.75.17.8016– 8020.2001, doi: 10.1073pnas.0604993103).

[0330] In some embodiments, protein fusogens may be re-targeted by covalently conjugating a HSC binding agent to the attachment protein. In some embodiments, the fusogen and HSC binding agent are covalently conjugated by expression of a chimeric protein comprising the fusogen linked to the HSC binding agent (e.g., retargeted attachment protein). The HSC binding agent can include any targeting protein able to confer specific binding to a target molecule expressed on the surface of a HSC. In some embodiments, a targeting protein can also include an antibody or an antigen-binding fragment thereof (e.g., Fab, Fab', F(ab')2, Fv fragments, scFv antibody fragments, disulfide-linked Fvs (sdFv), a Fd fragment consisting of the VH and CH1 domains, linear antibodies, single domain antibodies such as sdAb (either VL or VH), nanobodies, or camelid VHH domains), an antigen-binding fibronectin type III (Fn3) scaffold such as a fibronectin polypeptide minibody, a ligand, a cytokine, a chemokine, or a T cell receptor (TCRs). In some embodiments, the HSC binding agent is an antibody or antigen binding fragment thereof. In some embodiments, the fusion protein can be engineered to bind the Fc region of an antibody that targets an antigen on a target cell, redirecting the fusion activity towards cells that display the antibody’s target (DOI: 10.1128 / JVI.75.17.8016–8020.2001, doi:10.1038 / nm1192). In some embodiments, altered and non-altered fusogens may be displayed on the same retroviral vector or VLP (doi: 10.1016 / j.biomaterials.2014.01.051).

[0331] In some embodiments, a single-chain variable fragment (scFv) can be conjugated to fusogens to redirect fusion activity towards HSCs that display the scFv binding target (doi:10.1038 / nbt1060, DOI 10.1182 / blood-2012-11-468579, doi:10.1038 / nmeth.1514, doi:10.1006 / mthe.2002.0550, HUMAN GENE THERAPY 11:817– 826, doi:10.1038 / nbt942, doi:10.1371 / journal.pone.0026381, DOI 10.1186 / s12896-015-0142-z). In some embodiments, designed ankyrin repeat proteins (DARPin) can be conjugated to fusogens to redirect fusion activity towards HSCs that display the DARPin binding target (doi:10.1038 / mt.2013.16, doi:10.1038 / mt.2010.298, doi: 10.4049 / jimmunol.1500956), as well as combinations of different DARPins (doi:10.1038 / mto.2016.3). In some embodiments, a single domain antibody (e.g., a VHH) can be conjugated to fusogens to redirect fusion activity towards HSCs that display the sdAb binding target. In some embodiments, receptor ligands and antigens can be conjugated 93 sf-5966708186152009440 to fusogens to redirect fusion activity towards HSCs that display the target receptor (DOI: 10.1089 / hgtb.2012.054, DOI: 10.1128 / JVI.76.7.3558–3563.2002).

[0332] In some embodiments, the target cell is a CD34+ progenitor cells. In some embodiments, the target cell molecule is expressed on at least a subset of CD34+ progenitor cells.

[0333] In some embodiments, the cell surface molecule is expressed on HSCs. In some embodiments, the cell surface molecule is expressed on MPPs. In some embodiments, the cell surface molecule is expressed on MLPs. In some embodiments, the cell surface molecule is expressed on ETPs. In some embodiments, the cell surface molecule is expressed on MEPs. In some embodiments, the cell surface molecule is expressed on CMPs. In some embodiments, the cell surface molecule is expressed on GMPs. In some embodiments, the cell surface molecule is expressed on any combination of the foregoing CD34+ progenitor subpopulations. In some embodiments, the cell surface molecule is expressed on HSCs and MPPs. In some embodiments, the cell surface molecule is expressed on myeloid progenitors. In some embodiments, the cell surface molecule is expressed on lymphoid progenitors. In some embodiments, the cell surface molecule is expressed on myeloid progenitors. In some embodiments, the cell surface molecule is expressed on HSCs, MPPs, MEPs, CMPs, and GMPs.

[0334] In some embodiments, the cell surface molecule is ASCT2. In some embodiments, the target cell is ASCT2+.

[0335] In some embodiments, the cell surface molecule is CD105. In some embodiments, the target cell is CD105+.

[0336] In some embodiments, the cell surface molecule is CD110. In some embodiments, the target cell is CD110+.

[0337] In some embodiments, the cell surface molecule is CD117. In some embodiments, the target cell is CD117+.

[0338] In some embodiments, the cell surface molecule is CD133. In some embodiments, the target cell is CD133+.

[0339] In some embodiments, the cell surface molecule is CD146. In some embodiments, the target cell is CD146+.

[0340] In some embodiments, the cell surface molecule is CD164. In some embodiments, the target cell is CD164+.

[0341] In some embodiments, the cell surface molecule is CD34. In some embodiments, the target cell is CD34+.

[0342] In some embodiments, the cell surface molecule is CD46. In some embodiments, the target cell is CD46+.

[0343] In some embodiments, the cell surface molecule is CD49f. In some embodiments, the target cell is CD49f+. 94 sf-5966708186152009440

[0344] In some embodiments, the ta cell surface molecule is CD90. In some embodiments, the target cell is CD90+.

[0345] In some embodiments, the cell surface molecule is EPCR. In some embodiments, the target cell is EPCR+.

[0346] In some embodiments, the cell surface molecule is ITGA3. In some embodiments, the target cell is ITGA3+.

[0347] In some embodiments, the target molecule is CD133. In some embodiments, the target cell is CD133+. In some embodiments, the targeting agent is an anti-CD133 antibody. Exemplary anti-CD133 antibodies include CART133, AC133, 293C3-SDIE, CMab-43, RW03, 293C3H9 (293C3), and W6B3H10 (W6B3); and anti-CD133 antibodies disclosed in US Patent Nos. US8722858, US9249225, US9624303, US10106623, US10711068, US11098109, US11214628, US11352435, and US11220551; US Patent Application Nos. US20130224202; PCT Application Nos. WO200901840, WO2011089211, WO2011149493, WO2014128185, WO2015121383, WO2016154623, WO2018045880, WO2018072025, and WO2022022718; and Canadian Patent Application No. CA2962157.

[0348] In some embodiments, the lipid particles disclosed herein comprise one or more retargeted attachment proteins, each independently comprising (i) a paramyxovirus envelope attachment protein; and (ii) a targeting moiety directed to a target molecule expressed on the surface of a target cell, wherein the target molecule is CD133. In some embodiments, the targeting moiety is a CD133 binding domain, e.g., a CD133 binding agent, such as any of those disclosed herein.

[0349] In some embodiments, the lipid particles comprise one or more HSC binding domains that is a CD133 binding agent that targets the viral vector to a cell that is an HSC. In some embodiments, the lipid particles comprise two or more HSC binding domains that are each a CD133 binding agent that targets the viral vector to a cell that is an HSC. In some embodiments, each of the two or more HSC binding domains that are each a CD133 binding agent bind distinct epitopes of the same target molecule (CD133). In some embodiments, the lipid particle comprises two or more, e.g., two, three, four, or five or more, CD133 binding agents.

[0350] In some embodiments, the lipid particle comprises one or more targeting moieties, e.g., HSC binding domains, selected from: (a) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 536, 537, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 545, 546, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 518, 519, and 520, respectively, and a CDR-L1, a CDR-L2, 95 sf-5966708186152009440 and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) and a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 527, 528, and 529, respectively, and a CDR-L1, a CDR-L2, and a CDR- L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; and (e) and a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 554, 555, and 556, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively.

[0351] In some embodiments, the lipid particle comprises one or more targeting moieties, e.g., HSC binding domains, selected from: (a) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 289, 565, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 566, 567, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 568, 569, and 520, respectively, and a CDR-L1, a ...

Claims

186152009440 WHAT IS CLAIMED:

1. A lipid particle, comprising: (a) a retargeted attachment protein comprising a paramyxovirus envelope attachment protein linked to (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell; and (b) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), and (b) are exposed on the outside of the lipid bilayer.

2. The lipid particle of claim 1, wherein the paramyxovirus attachment protein is a variant paramyxovirus envelope attachment protein comprising one or more mutations to reduce native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations.

3. The lipid particle of claim 1 or 2, wherein the paramyxovirus envelope attachment protein is a first paramyxovirus envelope attachment protein and the lipid particle further comprises a second paramyxovirus envelope attachment protein, wherein the second paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein comprising one or more mutations to reduce native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more mutations, wherein the second paramyxovirus envelope attachment protein is exposed on the outside of the lipid bilayer.

4. The lipid particle of any one of claims 1-3, wherein the targeting one or both of the first target molecule and the second target molecule does not activate or inhibit, induce a phenotype change (for example maturation and / or differentiation), induce proliferation, and / or induce apoptosis of said target cell.

5. A lipid particle, comprising: (a) a retargeted attachment protein comprising a first paramyxovirus envelope attachment protein operably linked to (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell, 349 sf-5966708186152009440 (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions; and (c) at least one paramyxovirus fusion (F) protein; wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer.

6. The lipid particle of any of claims 1-5, wherein the first paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein.

7. The lipid particle of claim 6, wherein the variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions that reduces native tropism relative to the wild- type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions.

8. The lipid particle of any of claims 1-7, wherein the first and second paramyxovirus envelope attachment protein are the same.

9. The lipid particle of any of claims 1-8, wherein the second paramyxovirus envelope attachment protein is not linked or fused to a non-viral heterologous moiety that is a cell-specific targeting domain or functional domain, optionally wherein the second paramyxovirus envelope attachment protein is not linked or fused to a cell-specific targeting domain that is a targeting moiety directed to a target molecule expressed on the surface of a target cell.

10. The lipid particle of claims 1-9, wherein the first and second targeting moiety are each not selected from the group consisting of a cytokine, growth factor, hormone, neurotransmitter, apoptosis ligand and their combinations.

11. The lipid particle of any of claims 1-10, wherein targeting one or both of the first target molecule and the second target molecule does not modulate or induce a signal in the target cell.

12. The lipid particle of any of claims 1-11, wherein the first and second targeting moieties each bind to a cell surface molecule present on a target cell. 350 sf-5966708186152009440 13. The lipid particle of any of claims 1-12, wherein the first targeting moiety binds to a cell surface molecule present on a first target cell, and the second targeting moiety binds a surface molecule present on a second target cell.

14. The lipid particle of any of claims 1-13, wherein the first and second target molecule are different target molecules.

15. The lipid particle of any of claims 1-13, wherein the first and second target molecule are the same target molecule.

16. The lipid particle of claim 15, wherein the first and second targeting moiety bind distinct epitopes of the same target molecule.

17. The lipid particle of any of claims 1-16, wherein the cell surface molecule is a protein, glycan, or lipid.

18. The lipid particle of any of claims 1-17, wherein the target cell is selected from the group consisting of tumor-infiltrating lymphocytes, T cells, neoplastic or tumor cells, virus-infected cells, stem cells, central nervous system (CNS) cells, hematopoietic stem cells (HSCs), and liver cells.

19. The lipid particle of any of claims 1-18, wherein the target cell is selected from the group consisting of a CD3+ T cell, a CD4+ T cell, a CD8+ T cell, a hepatocyte, a hematopoietic stem cell, a CD34+ hematopoietic stem cell, a CD105+ hematopoietic stem cell, a CD117+ hematopoietic stem cell, a CD105+ endothelial cell, a B cell, a CD20+ B cell, a CD19+ B cell, a cancer cell, a CD133+ cancer cell, an EpCAM+ cancer cell, a CD19+ cancer cell, a Her2 / Neu+ cancer cell, a GluA2+ neuron, a GluA4+ neuron, a NKG2D+ natural killer cell, a SLC1A3+ astrocyte, a SLC7A10+ adipocyte, or a CD30+ lung epithelial cell.

20. The lipid particle of any of claims 1-19, wherein the target cell is a hepatocyte.

21. The lipid particle of claim 20, wherein the cell surface molecule is selected from the group consisting of CD34, CD117, and CD133.

22. The lipid particle of any of claims 1-19, wherein the target cell is a T cell. 351 sf-5966708186152009440 23. The lipid particle of claim 22, wherein the cell surface molecule is selected from the group consisting of CD3, CD4, CD7 CD8, ASCT2, CD105, CD110, CD117, CD133, CD146, CD164, CD34, CD46, CD49f, CD90, EPCR, and ITGA3.

24. The lipid particle of any of claims 5-23, wherein the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:

1.

25. A lipid particle, comprising: (a) a first retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first targeting moiety directed to CD133; and a second targeting moiety directed to CD133; and (b) at least one paramyxovirus fusion (F) protein; and the protein in (a), and (b) are exposed on the outside of the lipid bilayer.

26. The lipid particle of any of claims 1-25, wherein: (i) the first targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 516, 525, 534, 543, and 552, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (ii) the second targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 516, 525, 534, 543, and 552, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

27. The lipid particle of any of claims 1-25, wherein: (i) the first targeting moiety comprises: (a) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 536, 537, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 545, 546, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 518, 519, and 520, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 527, 528, and 529, respectively, and a CDR-L1, a CDR-L2, 352 sf-5966708186152009440 and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; or (e) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 554, 555, and 556, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively; and / or (ii) the second targeting moiety comprises: (a) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 536, 537, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 545, 546, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 518, 519, and 520, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 527, 528, and 529, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; or (e) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 554, 555, and 556, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively.

28. The lipid particle of any of claims 1-25, wherein: (i) the first targeting moiety comprises: (a) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 289, 565, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 566, 567, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 568, 569, and 520, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 570, 571, and 529, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; or (e) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 572, 573, and 556, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively; and / or 353 sf-5966708186152009440 (ii) the second targeting moiety comprises: (a) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 289, 565, and 538, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 540, 541, and 542, respectively; (b) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 566, 567, and 547, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 549, 550, and 551, respectively; (c) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 568, 569, and 520, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 522, 523, and 524, respectively; (d) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 570, 571, and 529, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 531, 532, and 533, respectively; or (e) a CD133 binding agent comprising a CDR-H1, a CDR-H2, and a CDR-H3 comprising the amino acid sequences of SEQ ID NOs: 572, 573, and 556, respectively, and a CDR-L1, a CDR-L2, and a CDR-L3 comprising the amino acid sequences of SEQ ID NOs: 558, 559, and 560, respectively.

29. The lipid particle of any of claims 1-25, wherein: (i) the first targeting moiety comprises: (a) a CD133 binding agent comprising a heavy chain variable (VH) region comprising the amino acid sequence of SEQ ID NO: 535, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a light chain variable (VL) region comprising the amino acid sequence of SEQ ID NO: 539, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (b) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 544, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 548, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (c) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 517, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 521, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (d) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 526, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 530, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; or (e) a CD133 binding agent comprising a VH region comprising the amino 354 sf-5966708186152009440 acid sequence of SEQ ID NO: 553, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 557, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (ii) the second targeting moiety comprises: (a) a CD133 binding agent comprising a heavy chain variable (VH) region comprising the amino acid sequence of SEQ ID NO: 535, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a light chain variable (VL) region comprising the amino acid sequence of SEQ ID NO: 539, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (b) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 544, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 548, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (c) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 517, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 521, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; (d) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 526, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 530, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; or (e) a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 553, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and a VL region comprising the amino acid sequence of SEQ ID NO: 557, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

30. The lipid particle of any of claims 1-29, wherein (a) the first targeting moiety comprises a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 517, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and (b) the second targeting moiety comprises a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 526, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto. 355 sf-5966708186152009440 31. The lipid particle of any of claims 1-29, wherein: (a) the first targeting moiety comprises a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 526, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and (b) the second targeting moiety comprises a CD133 binding agent comprising a VH region comprising the amino acid sequence of SEQ ID NO: 517, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

32. The lipid particle of any of claims 1-31, wherein the first and second targeting moiety bind to distinct epitopes on CD133.

33. The lipid particle of any of claims 25-32, further comprising a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions.

34. The lipid particle of claim 33, wherein the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:

1.

35. A lipid particle, comprising: (a) a first retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first targeting moiety directed to CD117; and a second targeting moiety directed to CD117; and (b) at least one paramyxovirus fusion (F) protein; and the protein in (a), (b) are exposed on the outside of the lipid bilayer.

36. The lipid particle of claims 1-25 and 35, wherein (a) the first targeting moiety comprises a CD117 binding agent comprising a VHH single domain antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 contained within an amino acid sequence selected from the group consisting of SEQ ID NOs: 512-515; and / or wherein (b) the second targeting moiety comprises a CD117 binding agent comprising a VHH single domain antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 contained within an amino acid sequence selected from the group consisting of SEQ ID NOs: 512-515. 356 sf-5966708186152009440 37. The lipid particle of any of claims 1-25, and 35-36, wherein (a) the first targeting moiety comprising a VHH single domain antibody comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 512-515, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (b) ) the second targeting moiety comprising a VHH single domain antibody comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 512-515, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

38. The lipid particle of claim 36 or claim 37, wherein (a) the first targeting moiety comprises a VHH comprising the amino acid sequence set forth in any one of SEQ ID NOS: 512-515; and / or (b) the second targeting moiety comprises a VHH comprising the amino acid sequence set forth in any one of SEQ ID NOS: 512-515.

39. The lipid particle of any of claims 1-25, and 35-38, wherein the first and second targeting moiety bind to distinct epitopes on CD117.

40. The lipid particle of any of claims 35-39, further comprising a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions.

41. The lipid particle of claim 40, wherein the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:

1.

42. A lipid particle, comprising: (a) a first retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first targeting moiety directed to CD8; and a second targeting moiety directed to CD8; and (b) at least one paramyxovirus fusion (F) protein; and the protein in (a), and (b) are exposed on the outside of the lipid bilayer.

43. The lipid particle of claim 42, wherein 357 sf-5966708186152009440 (i) the first targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 489, 496, 501, or 508 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (ii) the second targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 489, 496, 501, or 508, or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

44. The lipid particle of claims 1-25 and 42, wherein (a) the first targeting moiety comprises a CD8 binding agent comprising a VHH single domain antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 contained within an amino acid sequence of SEQ ID NO: 377; and / or wherein (b) the second targeting moiety comprises a CD8 binding agent comprising a VHH single domain antibody comprising a CDR-H1, a CDR-H2, and a CDR-H3 contained within an amino acid sequence of SEQ ID NO:

377.

45. The lipid particle of claim 42 or 44, wherein (a) the first targeting moiety comprises a VHH comprising the amino acid sequence set forth in SEQ ID NOS: 377; and / or (b) the second targeting moiety comprises a VHH comprising the amino acid sequence set forth in SEQ ID NO:

377.

46. The lipid particle of any of claims 42-45, wherein (a) the first targeting moiety comprises a VHH comprising the amino acid sequence set forth in SEQ ID NO: 377 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and / or (b) the second targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NO: 501 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto.

47. The lipid particle of any of claims 42-45, wherein (a) the first targeting moiety is an scFv and comprises an amino acid sequence selected from the group consisting of SEQ ID NO: 501 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto; and (b) the second targeting moiety comprises a VHH comprising the amino acid sequence set forth in SEQ ID NO: 377 or an amino acid sequence having at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity thereto. 358 sf-5966708186152009440 48. The lipid particle of any of claims 1-24, and 42-47, wherein the first and second targeting moiety bind to distinct epitopes on CD8.

49. The lipid particle of any of claims 16-48, wherein the distinct epitopes are non- overlapping.

50. The lipid particle of any of claims 16-49, wherein the first and second targeting moiety bind to the distinct epitopes in a non-competitive manner.

51. The lipid particle of claim 1-50, wherein each of the first targeting moiety and the second targeting moiety are independently selected from the group consisting of an antibody or antigen-binding fragment, a DARPin, an Aptamer, an Affimer, an Affibody, a Knottin, an Avimer, a Monobody, an Anticalin, a Fynomer, and a targeting peptide.

52. The lipid particle of any of claims 1-51, wherein the first targeting moiety and the second targeting moiety are independently selected from the group consisting of a single domain antibody or a single chain variable fragment (scFv).

53. The lipid particle of any of claims 42-52, further comprising a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions.

54. The lipid particle of claim 49, wherein the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:

1.

55. A lipid particle, comprising: (a) a retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first and second targeting moiety directed to CD133, (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions that reduces the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions; and 359 sf-5966708186152009440 (c) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer.

56. A lipid particle, comprising: (a) a retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first and second targeting moiety directed to CD117, (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions that reduces the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions; and (c) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer.

57. A lipid particle, comprising: (a) a retargeted attachment protein comprising (i) a first paramyxovirus envelope attachment protein; and (ii) a first and second targeting moiety directed to CD8, (b) a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions that reduces the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions; and (c) at least one paramyxovirus fusion (F) protein; and wherein the protein in (a), (b) and (c) are exposed on the outside of the lipid bilayer.

58. The lipid particle of claims 24-57, wherein the first paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein.

59. The lipid particle of claim 58, wherein the variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions that reduces native tropism relative to the wild- type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions.

60. The lipid particle of any of claims 25-59, wherein the second paramyxovirus envelope attachment protein is a variant paramyxovirus envelope attachment protein.

61. The lipid particle of claim 60, wherein the variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions that reduces native tropism relative to the wild- 360 sf-5966708186152009440 type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions.

62. The lipid particle of any of claims 1-61, wherein the first targeting moiety is selected from the group consisting of a single domain antibody or a single chain variable fragment (scFv).

63. The lipid particle of any of claims 1-62, wherein the second targeting moiety is selected from the group consisting of a single domain antibody or a single chain variable fragment (scFv).

64. The lipid particle of claims 54 and claim 62, or 63, wherein the single domain antibody is a VHH.

65. The lipid particle of any of claims 1-64, wherein the first variant paramyxovirus envelope attachment protein and the second variant paramyxovirus envelope attachment protein are the same.

66. The lipid particle of any of claims 1-65, wherein the first paramyxovirus envelope attachment protein and the second paramyxovirus envelope attachment protein are different.

67. The lipid particle of any of claims 1-66, wherein the first paramyxovirus envelope attachment protein is an envelope attachment protein from a Nipah virus, Hendra virus, or Measles virus, or is a variant or biologically active portion thereof of any of the foregoing.

68. The lipid particle of any of claims 1-67, wherein the first paramyxovirus envelope attachment protein is a wild-type paramyxovirus G protein, H protein or HN protein or is a variant or biologically active portion of any of the foregoing.

69. The lipid particle of claim 67 or claim 68, wherein the first paramyxovirus envelope attachment protein is a wild-type Nipah virus G (NiV-G) protein or is a variant or biologically active portion of a NiV-G.

70. The lipid particle of any of claims 67-69, wherein the first paramyxovirus envelope attachment protein is a variant NiV-G that is a variant or a biologically active portion of a wild-type NiV- G. 361 sf-5966708186152009440 71. The lipid particle of any of claims 1-70, wherein the second paramyxovirus envelope attachment protein is an envelope attachment protein from a Nipah virus, Hendra virus, or Measles virus, or is a variant or biologically active portion of any of the foregoing.

72. The lipid particle of any of claims 1-71, wherein the second paramyxovirus envelope attachment protein is a wild-type paramyxovirus G protein, H protein or HN protein or is a variant or biologically active portion of any of the foregoing.

73. The lipid particle of claim 71 or claim 72, wherein the second paramyxovirus envelope attachment protein is a wild-type Nipah virus G (NiV-G) protein or is a variant or a biologically active portion of a NiV-G.

74. The lipid particle of any of claims 1-73, wherein the second paramyxovirus envelope attachment protein is a variant NiV-G that is a variant or a biologically active portion of a wild-type NiV- G.

75. The lipid particle of any of claims 3-70, wherein the second paramyxovirus envelope attachment protein is a variant paramyxovirus envelope glycoprotein from a Nipah virus, Hendra virus, or Measles virus or a biologically active portion thereof.

76. The lipid particle of any of claims 3-70 and 75, wherein the second paramyxovirus envelope attachment protein is a variant of a wild-type paramyxovirus G protein, H protein or HN protein or a biologically active portion thereof.

77. The lipid particle of claim 73 or 74, wherein the variant is a variant NiV-G that is a variant of a wild-type Nipah virus G (NiV-G) protein or a biologically active portion thereof.

78. The lipid particle of claim 70, claim 74, or claim 77, wherein the variant NiV-G is truncated by up to 40 contiguous amino acids at or near the N-terminus of the wild-type NiV-G set forth in SEQ ID NO:

1.

79. The lipid particle of any of claims 70, 74, 77 and 78, wherein the variant NiV-G has a truncation of amino acids 2-34 of the wild-type NiV-G set forth in SEQ ID NO:

1.

80. The lipid particle of any of claims 70, 73 and 77-79, wherein the variant NiV-G exhibits reduced binding to Ephrin B2 or Ephrin B3. 362 sf-5966708186152009440 81. The lipid particle of claim 80, wherein the variant NiV-G comprises: one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:

1.

82. The lipid particle of claim 80 or claim 81, wherein the variant NiV-G comprises amino acid substitutions E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:

1.

83. The lipid particle of any of claims 70, 74 and 77-79, wherein the variant NiV-G has an amino acid sequence having at or about 80%, at least at or about 81 %, at least at or about 82%, at least at or about 83%, at or about 84%, at least at or about 85%, at least at or about 86%, or at least at or about 87%, at least at or about 88%, or at least at or about 89%, at least at or about 90%, at least at or about 91 %, at least at or about 92%, at least at or about 93%, at least at or about 94%, at least at or about 95%, at or about 96%, at least at or about 97%, at least at or about 98%, or at least at or about 99% sequence identity to SEQ ID NO:

228.

84. The lipid particle of any of claims 70, 74 and 77-79, wherein the variant NiV-G has the amino acid sequence set forth in SEQ ID NO:

228.

85. The lipid particle of any of claims 1-84, wherein the at least one paramyxovirus fusion (F) protein is an F protein from a henipavirus or is a biologically active portion thereof or variant thereof.

86. The lipid particle of claim 85, wherein the henipavirus is a Hendra virus.

87. The lipid particle of claim 85, wherein the henipavirus is a Nipah virus.

88. The lipid particle of any of claims 1-87, wherein the paramyxovirus F protein is a wild- type NiV-F protein or a variant or a biologically active portion thereof.

89. The lipid particle of any of claims 1-88, wherein the paramyxovirus F protein is a variant NiV-F that is a variant or a biologically active portion of a wild-type NiV-F protein.

90. The lipid particle of claim 89, wherein the variant NiV-F is truncated by up to22 contiguous amino acids the at the C-terminus of the wild-type NiV-F set forth in SEQ ID NO:235, optionally not include the initial methionine. 363 sf-5966708186152009440 91. The lipid particle of claim 89 or claim 90, wherein the variant NiV-F protein is a truncated NiV-F that lacks amino acids 525-546 of SEQ ID NO:

235.

92. The lipid particle of any of claims 89-91, wherein the variant NiV-F has the amino acid sequence set forth in SEQ ID NO: 227 or an amino acid sequence having at or about 80%, at least at or about 81%, at least at or about 82%, at least at or about 83%, at or about 84%, at least at or about 85%, at least at or about 86%, or at least at or about 87%, at least at or about 88%, or at least at or about 89%, at least at or about 90%, at least at or about 91%, at least at or about 92%, at least at or about 93%, at least at or about 94%, at least at or about 95%, at or about 96%, at least at or about 97%, at least at or about 98%, or at least at or about 99% sequence identity to SEQ ID NO:

227.

93. The lipid particle of any of claims 89-92, wherein the variant NiV-F has the amino acid sequence set forth in SEQ ID NO:

227.

94. The lipid particle of any of claims 1-93, wherein the paramyxovirus F protein is an F0 precursor or is a proteolytically cleaved form thereof comprising F1 and F2 subunits.

95. The lipid particle of claim 94, wherein the proteolytically cleaved form is a cathepsin L cleavage product.

96. The lipid particle of any of claims 1-95, wherein the paramyxovirus envelope attachment protein and the first targeting moiety and second targeting moiety are linked via one or more linkers.

97. The lipid particle of claim 96, wherein the one or more linkers are one or more peptide linker.

98. The lipid particle of any of claims 1-97, wherein the retargeted attachment protein comprises in order: paramyxovirus attachment protein – first linker – first targeting moiety – second linker – second targeting moiety.

99. The lipid particle of claim 98, wherein the first linker and / or second linker is independently a peptide linker.

100. The lipid particle of claim 99, wherein the first linker and second linker are the same. 364 sf-5966708186152009440 101. The lipid particle of claim 99, wherein the first linker and second linker are different.

102. The lipid particle of claim 97 or claim 99, wherein the peptide linker is 2 to 65 amino acids in length.

103. The lipid particle of any of claims 99-102, wherein the peptide linker is a flexible linker that comprises GS, GGS, GGGGS, GGGGGS or combinations thereof.

104. The lipid particle of any of claims 99-103, wherein the peptide linker is selected from: (GGS)n, wherein n is 1 to 10; (GGGGS)n, wherein n is 1 to 10; or (GGGGGS)n, wherein n is 1 to 6.

105. The lipid particle of any of claims 1-104, wherein the peptide linker is selected from SEQ ID NOs: 589-592.

106. The lipid particle of any of claims 1-105, wherein the lipid particle further comprises one or more additional paramyxovirus envelope attachment glycoproteins embedded in the lipid bilayer.

107. The lipid particle of claim 106, wherein the one or more additional paramyxovirus envelope attachment glycoproteins is a retargeted attachment protein comprising a paramyxovirus envelope attachment protein and a further targeting moiety.

108. The lipid particle of any of claims 1-107, wherein the at least one paramyxovirus fusion (F) protein exhibits fusogenic activity with a target cell upon binding of at least one paramyxovirus envelope attachment protein to the target molecule on the target cell.

109. The lipid particle of any of claims 1-108, wherein the lipid particle comprises a viral nucleic acid.

110. The lipid particle of claim 109, wherein the viral nucleic acid comprises one or more of (e.g., all of) the following nucleic acid sequences: 5’ LTR (e.g., comprising U5 and lacking a functional U3 domain), Psi packaging element (Psi), Central polypurine tract (cPPT) / central termination sequence (CTS) (e.g. DNA flap), Poly A tail sequence, a posttranscriptional regulatory element (e.g. WPRE), a Rev response element (RRE), and 3’ LTR (e.g., comprising U5 and lacking a functional U3).

111. The lipid particle of any of claims 1-110, wherein the lipid particle is a viral vector. 365 sf-5966708186152009440 112. The lipid particle of any of claims 1-111, that is a retroviral vector.

113. The lipid particle of any of claims 1-111, that is a lentiviral vector.

114. The lipid particle of any of claims 1-108 and 111-113, wherein the lipid particle is devoid of viral genomic nucleic acid.

115. The lipid particle of any of claims 1-108 and 111-113, wherein the lipid particle is devoid of viral genomic DNA.

116. The lipid particle of any of claims 1-110 and 115, that is a viral-like particle.

117. The lipid particle of any of claims 1-110, 115 and 116 that is a retroviral-like particle.

118. The lipid particle of any of claims 1-110, 115 and 116 that is a lentiviral-like particle.

119. The lipid particle of any of claims 1-118, wherein the lipid particle is produced as a preparation with increased titer compared to a reference lipid particle preparation that is similarly produced but with only the first retargeted attachment protein.

120. The lipid particle of any of claims 5-119, wherein the lipid particle is produced as a preparation with increased titer compared to a reference lipid particle preparation that is similarly produced but without the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more substitutions.

121. The lipid particle of claim 120, wherein the second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprises one or more amino acid substitutions corresponding to amino acid substitutions selected from the group consisting of E501A, W504A, Q530A and E533A with reference to numbering set forth in SEQ ID NO:

1.

122. The lipid particle of any of claims 1-119, wherein the lipid particle is produced in suspension culture as a preparation with increased titer compared to a reference lipid particle preparation that is similarly produced but with only the first retargeted attachment protein. 366 sf-5966708186152009440 123. The lipid particle of any of claims 120-122, wherein the titer is increased by at or greater than 1.2-fold, 1.3-fold, 1.4-fold, 1.5-fold, 1.6-fold, 1.7-fold, 1.8-fold, 2-fold, 2.5-fold, 3-fold, 4-fold, 5- fold, 6-fold, 7-fold, 8-fold, 9-fold, 10-fold, or more.

124. The lipid particle of any of claims 1-123, further comprising an exogenous agent for delivery to a target cell.

125. The lipid particle of claim 124, wherein the exogenous agent is present in the lumen.

126. The lipid particle of claim 124 or 125, wherein the exogenous agent is a protein or a nucleic acid, optionally wherein the nucleic acid is a DNA or RNA.

127. The lipid particle of any of claims 124-126, wherein the exogenous agent is a nucleic acid encoding a cargo for delivery to the target cell.

128. The lipid particle of any of claims 124-127, wherein the exogenous agent is or encodes a therapeutic agent, a diagnostic agent, or a genome-modifying enzyme.

129. The lipid particle of any of claims 124-128, wherein the exogenous agent encodes a membrane protein, optionally wherein the membrane protein is an antigen receptor for targeting cells expressed by or associated with a disease or condition.

130. The lipid particle of claim 129, wherein the membrane protein is a chimeric antigen receptor (CAR).

131. The lipid particle of any of claims 124-128, wherein the exogenous agent is a nucleic acid comprising a payload gene for correcting a genetic deficiency, optionally a genetic deficiency in the target cell, optionally wherein the genetic deficiency is associated with a liver cell or a hepatocyte.

132. The lipid particle of any of claims 124-131, wherein binding of the paramyxovirus envelope attachment protein or biologically active portion thereof to a target molecule expressed on the surface of a target cell mediates fusion of the particle with the target cell and delivery of the exogenous agent to the target cell.

133. The lipid particle of any of claims 124-132, wherein at or greater than 10%, 20%, 30%, 40%, 50%, 60% of the target cells are delivered the exogenous agent. 367 sf-5966708186152009440 134. The lipid particle of any of claims 124-133, wherein delivery of the exogenous cell to the target cell is increased compared to a reference particle preparation that is similarly produced but with only a first retargeted attachment protein.

135. The lipid particle of claim 134, wherein the delivery to the target cell is increased by at or greater than 1.2-fold, 1.3-fold, 1.4-fold, 1.5-fold, 1.6-fold, 1.7-fold, 1.8-fold, 2-fold, 2.5-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold, 10-fold, or more.

136. A producer cell comprising (a) a nucleic acid encoding a retargeted attachment protein comprising a paramyxovirus envelope attachment protein linked to (i) a first targeting moiety directed to a first target molecule expressed on the surface of a target cell, and (ii) a second targeting moiety directed to a second target molecule expressed on the surface of a target cell; and (b) a nucleic acid encoding at least one paramyxovirus fusion (F) protein 137. The producer cell of claim 136, further comprising a nucleic acid encoding a second paramyxovirus envelope attachment protein that is a variant paramyxovirus envelope attachment protein comprising one or more amino acid substitutions to reduce the native tropism relative to the wild-type paramyxovirus envelope attachment protein not comprising the one or more amino acid substitutions.

138. The producer cell of claim 136 or 137, wherein the cell further comprises a viral nucleic acid(s).

139. The producer cell of any of claim 138, wherein the viral nucleic acid(s) are lentiviral nucleic acids.

140. The producer cell of any of claims 136-139, wherein the cell is a mammalian cell.

141. The producer cell of any of claims 136-140, wherein the producer cell is selected from the group consisting of CHO cells, BHK cells, MDCK cells, C3H 10T1 / 2 cells, FLY cells, Psi-2 cells, BOSC 23 cells, PA317 cells, WEHI cells, COS cells, BSC 1 cells, BSC 40 cells, BMT 10 cells, VERO cells, W138 cells, MRC5 cells, A549 cells, HT1080 cells, 293 cells, 293T cells, B-50 cells, 3T3 cells, NIH3T3 cells, HepG2 cells, Saos-2 cells, Huh7 cells, HeLa cells, W163 cells, 211 cells, and 211A cells.

142. The producer cell of any of claims 136-141, wherein the producer cell comprises 293T cells. 368 sf-5966708186152009440 143. The producer cell of any of claims 137-142, wherein the viral nucleic acid(s) lacks one or more genes involved in viral replication.

144. The producer cell of any of claims 137-143, wherein the viral nucleic acid comprises a nucleic acid encoding a viral packaging protein selected from one or more of Gag, Pol, Rev and Tat.

145. The producer cell of any of claims 138-144, wherein the viral nucleic acid comprises: one or more of (e.g., all of) the following nucleic acid sequences: 5’ LTR (e.g., comprising U5 and lacking a functional U3 domain), Psi packaging element (Psi), Central polypurine tract (cPPT) / central termination sequence (CTS) (e.g. DNA flap), Poly A tail sequence, a posttranscriptional regulatory element (e.g. WPRE), a Rev response element (RRE), and 3’ LTR (e.g., comprising U5 and lacking a functional U3).

146. A method of making a lipid particle, comprising: a) providing a producer cell of any of claims 136-145; b) culturing the cell under conditions that allow for production of the lipid particle, and c) separating, enriching, or purifying the lipid particle from the cell, thereby making the lipid particle.

147. The method of claim 146, wherein the lipid particle is a pseudotyped lentiviral vector.

148. A lipid particle produced by the method of claim 146 or claim 147.

149. A composition comprising a plurality of lipid particles of any of claims 1-135 and 148.

150. The composition of claim 149, further comprising a pharmaceutically acceptable carrier.

151. A method of transducing a cell comprising contacting a cell with a lipid particle of any of claims 1-135 and 148 or a composition of claim 149 or claim 150.

152. A method of delivering an exogenous agent into a target cell, the method comprising contacting a lipid particle of any of claims 124-135 and 148 or a composition of claim 149 or claim 150 with a target cell.

153. The method of claim 151 or claim 152, wherein the contacting is in vitro or ex vivo. 369 sf-5966708186152009440 154. The method of claim 151 or claim 152, wherein the contacting is in vivo in a subject.

155. A method of delivering an exogenous agent to a cell in a subject, the method comprising administering to the subject a lipid particle of any of claims 124-135 and 148 or a composition of claim 149 or claim 150.

156. The method of claim 155, wherein the exogenous agent is or encodes a therapeutic agent for treating a disease or condition in the subject.

157. A method of treatment, the method comprising administering to a subject a lipid particle of any of claims 124-135 and 148 or a composition of claim 149 or claim 150.

158. The method of any of claims 152-157, wherein the exogenous agent is or encodes a membrane protein, optionally a chimeric antigen receptor, for targeting an antigen associated with a disease or condition in the subject.

159. The method of any of claims 152-157, wherein the exogenous agent is for use in gene therapy to correct a genetic deficiency or replaces a deficient or missing gene in the subject.

160. The method of any of claims 155-159, wherein the subject is a human subject.

161. The method of any of claims 151-160, wherein the method further comprises administering to the subject one or more agents that stimulate mobilization of bone marrow cells from the bone marrow to the peripheral blood.

162. The method of any of claims 151-161, wherein the subject has previously been administered one or more agents that stimulate mobilization of bone marrow cells from the bone marrow to the peripheral blood.

163. The method of claim 161 or 162, wherein the one or more agents that stimulate mobilization are selected from the group consisting of stem cell factor (SCF), small molecule VLA-4 inhibitor BI05192, BOP (N-(benzenesulfonyl)-L-prolyl-L-0-(1-pyrrolidinylcarbonyl)tyrosine), heparin, granulocyte colony-stimulating factor (G-CSF), MGTA-145, and plerixafor (AMD3100). 370 sf-5966708186152009440 164. The method of any of claims 161-163, wherein the one or more agents that stimulate mobilization comprise G-CSF.

165. The method of any of claims 161-164, wherein the one or more agents that stimulate mobilization comprise plerixafor. 371 sf-5966708

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