Compositions and methods for universal pseudoretroviruses

Abstract

Provided herein are retroviral vector systems for the production of universal pseudotype retroviruses for cell therapy and gene therapy. The vector system comprises an envelope plasmid and a packaging plasmid, wherein at least one of these plasmids encodes a binding moiety that binds directly to a target cell via a cell binding domain or indirectly to a target cell via an antibody binding domain. Also provided are related retrovirus packaging cells, retroviruses, virus-like particles, and methods for their preparation and use in the prevention or treatment of diseases.

Description

Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 405,720, filed on September 12, 2022, the entire disclosure of which is hereby incorporated by reference in its entirety for all purposes. Background of the Invention The modern development of cell therapy and gene therapy represents a revolutionary approach to treating diseases. Gene therapy can be used to correct genetic diseases by editing the genome (e.g., by using clustered regularly interspaced short palindromic repeats (CRISPR) gene editing sequences). Gene therapy can also address genetic diseases by introducing new corrective genetic information (e.g., by using clinical - grade viruses). Cell therapy can be applied to reprogram cells, redirecting the natural, complex functions of the human body to new targets. This opens up vast possibilities for treatment modalities that were not previously achievable using old paradigms. Both cell therapy and gene therapy rely on the successful delivery of therapeutic gene payloads to precisely targeted cells or tissues. Many of these therapies also require the direct integration of the delivered genetic information into the genome, enabling long - term, heritable, and stable expression of the gene. Retroviruses similar to the human immunodeficiency virus (HIV) have been adapted to achieve the delivery and integration of gene payloads related to cell therapy and gene therapy. Cancer cell lines can be used as hosts, and these retroviruses are prepared by transfecting these host cell lines with multiple plasmids or vectors. The transfer vector encodes the genome of the retrovirus produced by the host cell. Thus, the transfer vector includes gene payloads, such as therapeutic genes and gene circuits, which are integrated into the genome of the cells targeted by the retrovirus. The packaging plasmid encodes the viral Gag - Pol protein, which both generates the retrovirus within the host cell and integrates the gene payload into the host cell genome. The envelope plasmid encodes the binding protein that enables the retrovirus to target the host cell and initiate the virus entry process. Once the cell line produces these retroviruses, the virus can be used to introduce new genetic material into cells. The envelope protein directs the virus to surface receptors on the host cell, binding the two together and initiating the virus entry process. Once bound, the proteins encoded on the transfer plasmid fuse the cell and the virus together, releasing the contents of the virus into the cytoplasm of the cell. In a series of complex steps, the viral genome is reverse - transcribed from RNA to DNA and brought into the nucleus, where the viral integrase semi - randomly integrates the viral DNA into the genome. Then, the introduced payload can separate from the cell and undergo all other genomic processes, resulting in long - term changes capable of enabling cell and gene therapy. However, these applications of retroviruses pose significant challenges, greatly reducing their use in more advanced cell and gene therapies. These therapies increasingly require selective transduction only to the desired cell types, and achieving such selectivity remains extremely difficult for a variety of reasons. First, viral envelope proteins generally do not target specified target cells. The most prevalent envelope protein used with retroviruses is VSV-G, which binds to the LDL-receptor protein. However, this family of surface proteins is absent or not adequately expressed on many therapeutically important cell types. For example, natural killer (NK) cells are an immune cell with extremely exciting potential for treating cancer, autoimmune diseases, and aging diseases. Unfortunately, natural killer cells do not express LDL and are thus difficult to adapt for engineered cell therapies. Using other envelope proteins, such as RD114 (which binds to the RDR surface protein) or BaEV (which binds to the ASCT surface protein), can overcome this problem to some extent, but usually at the cost of low virus production efficiency or more limited knowledge of the envelope protein binding partners. Second, viral envelope proteins lack selectivity. The binding partners of these proteins are not restricted to being expressed by a specific cell type. Thus, retroviruses expressing a specific envelope protein generally cannot target specified tissues when delivered in situ. When the virus is administered ex vivo, retroviruses also generally cannot target specified cell types in a mixture. As an example, currently available techniques do not allow for the engineering of only T cells in a peripheral blood mononuclear cell (PBMC) culture by using retroviruses as an engineering tool. In view of these observations and results, there is a need in the art, particularly in the fields of gene and cell therapy, for new systems and techniques to improve the usefulness of retroviruses. In particular, new developments are needed to expand the repertoire of cell types that can be engineered by retroviruses while also making the virus highly selective for the cells or tissues of interest. The disclosure herein provides a series of solutions to these challenges and offers related and additional advantages. SUMMARY OF THE INVENTION Generally speaking, the present disclosure provides systems, materials, and methods related to retroviruses that are modified to be decorated with binding moieties that allow the virus to directly or indirectly bind to target cells of interest. By leveraging certain types of binding moieties and their binding partners (such as antibodies, antibody fragments, and endogenous or engineered ligands), the methods and compositions provided enable the design and use of retroviruses with higher specificity and flexibility than previously possible. Thus, the synthetic materials and related methods disclosed herein provide useful tools for a wide range of applications, including the fields of gene therapy and cell engineering. In one aspect, the present disclosure provides a retroviral vector system comprising an envelope plasmid, a packaging plasmid, and a transfer plasmid. The envelope plasmid encodes the viral membrane fusion protein of a retrovirus. The packaging plasmid encodes the Gag-Pol protein of a retrovirus. The transfer plasmid comprises one or more genes of interest transferred from a retrovirus to a target cell. One or both of the envelope plasmid and the packaging plasmid further encode a binding moiety. The binding moiety directly or indirectly binds to a surface feature of a target cell. In another aspect, the present disclosure provides a retroviral packaging cell. The retroviral packaging cell comprises any retroviral packaging system disclosed herein. In another aspect, the present disclosure provides a retrovirus comprising a viral membrane fusion protein, a viral genome, and a binding moiety. The viral genome comprises one or more genes of interest transferred from a retrovirus to a target cell. The binding moiety binds to a ligand, which comprises an antibody, an antibody mimetic, a single-chain variable fragment (scFv), or a derivative or fragment thereof. The ligand binds to a surface feature of a target cell. In another aspect, the present disclosure provides virus-like particles comprising a binding moiety. The binding moiety binds to a ligand, which comprises an antibody, an antibody mimetic, a single-chain variable fragment (scFv), or a derivative or fragment thereof. The ligand binds to a surface feature of a target cell. In another aspect, the present disclosure provides a method for producing a retrovirus. The method comprises transfecting a host cell with any retroviral vector system disclosed herein. In another aspect, the present disclosure provides a method for preventing or treating a disease in a subject. The method comprises administering to the subject any retroviral vector system, retroviral packaging cell, retrovirus, or virus-like particle disclosed herein. Brief Description of the Drawings Figure 1 is a diagrammatic illustration of a retroviral vector system, a retroviral packaging cell, and a retrovirus according to the provided embodiments. Figure 2 is a schematic illustration of an envelope plasmid encoding a binding moiety according to the provided embodiments.

[0001] Figure 3 shows results demonstrating an example of lymphocyte transduction by the provided retrovirus having a CD7-targeting nanobody as a binding moiety. Figure 4 is a graph depicting transduction of natural killer (NK) cells by the provided retrovirus or by a comparative lentivirus. Figure 5 is a diagrammatic illustration of a universal pseudotyped retrovirus according to the provided embodiments. Figure 6It is a graph showing the transduction of Jurkat cells with retroviruses provided at different concentrations that have monomeric streptavidin (mSA) as a binding moiety and a CD71 antibody conjugated with biotin. Figure 7 It is a graph showing the transduction of Jurkat cells with retroviruses provided at different concentrations that have an anti - fluorescein isothiocyanate (αFITC) binding moiety and a CD71 antibody conjugated with FITC. Figure 8 It is a graph showing Figure 6 the intensity of mCherry expression delivered by retroviruses in Jurkat cells. Figure 9 It is a graph showing Figure 7 the intensity of mCherry expression delivered by retroviruses in Jurkat cells.

[0002] Figure 10 It is a graph showing the transduction of Jurkat cells with a provided retrovirus that has a FITC single - chain variable fragment (scFv) binding moiety, where the Jurkat cells have been engineered with an antibody against a lymphocyte marker (CD7) or a T - cell marker (CD3). Figure 11 It is a graph showing the transduction of Raji cells with a provided retrovirus that has a FITC single - chain variable fragment (scFv) binding moiety, where the Raji cells have been engineered with an antibody against a B - cell marker CD19 or a B - cell marker CD20. Figure 12 It is a graph showing the transduction of primary T cells with a provided retrovirus that has a FITC single - chain variable fragment (scFv) binding moiety, where the T cells have been engineered with an antibody against a subtype marker CD4 or a subtype marker CD8. Figure 13 It is a graph showing the specific transduction of CD4 + T cells but not CD8 + T cells by a provided retrovirus that has a FITC binding moiety conjugated with a CD4 antibody. Figure 14 It is a graph showing the specific transduction of CD8 + T cells but not CD4 + T cells by a provided retrovirus that has a FITC binding moiety conjugated with a CD8 antibody. DETAILED DESCRIPTION OF THE INVENTION 1. Overview The present disclosure generally provides materials and methods related to retroviruses and virus-like particles that are engineered to have modular binding moieties on their surfaces. The specific binding moieties described herein modify the retroviruses and virus-like particles and allow them to directly bind to cells of interest, or to bind to antibodies, antibody fragments, or other ligands that bind to cells. This moiety can advantageously bind to readily available off-the-shelf antibodies, antibodies that are easily customized, or surface features that are already present on the targeted cells. The modular plug-and-play manner in which the binding moieties can be designed or selected provides several significant advantages over existing retroviral methods. For example, the transduction space available for retroviruses and virus-like particles can be increased to include other cell types that cannot be transduced by traditional lentiviral methods. Importantly, these other cell types include many cells, such as natural killer (NK) cells, which are major candidate cells targeted in the development of cell therapies and gene therapies. The binding moiety can also enable universal pseudotyping of retroviruses or virus-like particles, such that a single retrovirus or virus-like particle design can be conjugated to any antibody to target any cell. Thus, although the range of cells that can be targeted for transduction with the provided tools and techniques is broad, the targeting is also advantageously more specific compared to using other retroviral methods. By customizing the binding moiety to recognize a specific binding partner, off-target transduction can be minimized or substantially eliminated. This reduction in unwanted non-specific targeting can provide important benefits in, for example, therapeutic applications, where non-specific targeting can lead to harmful side effects. This important cell specificity of the provided retroviruses and virus-like particles can be easily switched from one target to another due to the modular nature of the binding moiety and its activity. The binding moieties of the provided retroviruses and virus-like particles are encoded on the packaging and / or envelope plasmids of the virus or particle. Thus, the gene encoding the binding moiety advantageously does not integrate into the host cells that produce the virus or particle or that are targeted for transduction. Additionally, the system for producing the provided retroviruses and virus-like particles can include a minimal number of plasmids, simplifying the process and increasing efficiency. For example, the plasmid system for producing the provided retroviruses can include as few as three plasmids: a packaging plasmid, an envelope plasmid, and a transfer plasmid, where at least one of the packaging plasmid and the envelope plasmid encodes the binding moiety and the transfer plasmid carries the genetic material to be transferred to the target cells. The production of the provided retroviruses and virus-like particles is also advantageously facile and can be readily incorporated into standard virus production procedures. For example, virus-producing cells, such as HEK293T cells, can be transfected with a transfer plasmid encoding the viral genome, an envelope plasmid encoding the viral envelope, and one or more packaging plasmids encoding the viral Gag-Pol protein. The envelope and / or packaging plasmids in such systems can contain a binding moiety. Virus-producing cells containing these plasmids then produce functional viruses that have the binding moiety present on their surface. In some cases, an antibody can be incubated with purified retroviruses to conjugate the antibody to the virus. The antibody can then direct the retrovirus to target cells. Figure 1 Several exemplary aspects of the provided retroviral vector systems, retroviral packaging cells, and methods of targeting cells are shown. A general retrovirus can be produced by engineering a packaging plasmid or an envelope plasmid as shown in panel (A) of the figure with a binding moiety. Thus, the binding moiety can include a binding domain fused directly to a transmembrane domain. The binding moiety can be encoded either directly upstream or downstream of the envelope protein or the Gag-Pol protein and can be separated from the translated protein by a 2A tag. Also as shown, a homologous envelope protein, such as VSV-G, can be further mutated to no longer bind to its homologous ligand. Figure 1 Panel (B) of the figure shows transfection of virus packaging cells with an engineered envelope plasmid as well as a transfer plasmid and a packaging plasmid. These transfected cells then produce retroviruses modified with the binding moiety as shown in panel (C). The binding moiety can contain a cell-binding domain (CBD, top) or an antibody / antibody-fragment / ligand-binding domain (ABD, bottom). In the case where the binding moiety contains a CBD, the binding moiety directs the virus to a specified surface protein of the target cell such that the virus can transduce this particular cell type. In the case where the binding moiety contains an ABD, the binding moiety binds a secondary conjugate such as an antibody, and the combined virus and antibody together transduce the specified target cell type. II. Definitions Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the relevant art. As used herein, the term "retrovirus" refers to a member of the retroviridae family of viruses. Retroviruses have a single-stranded, diploid, positive-sense RNA genome that is reverse transcribed into a DNA intermediate that can subsequently be incorporated into the host cell genome. Viruses derived from the retroviridae family are typically enveloped particles with a diameter of 80 nm to 120 nm. A retroviral vector or plasmid can be a replication-defective viral particle derived from a virus of the retroviridae family. The plasmid can contain group-specific antigen (Gag) and Pol proteins, a single-stranded RNA genome, and an envelope protein. A retroviral plasmid can also include the psi element and long terminal repeats (LTRs) required for efficient packaging and DNA reverse transcription. Retroviruses include alpha-retroviruses, gamma-retroviruses, and lentiviruses. Representative lentiviral species include human immunodeficiency virus (HIV). Representative gamma-retroviral species include murine leukemia virus and feline leukemia virus. Integrase-deficient retroviruses and retroviral vectors are unable to integrate the retroviral vector genome into the host cell genome. An integrase-deficient retroviral vector or plasmid can be derived from a conventional retroviral vector and lacks a retroviral integrase or contains a mutant form of the retroviral integrase. After entering the host cell, the retroviral vector genome of the integrase-deficient retrovirus is reverse transcribed in the cytoplasm and delivered to the nucleus, but cannot be stably integrated into the host cell genome. As used herein, the term "transduction" refers to the process by which a virus enters a host cell, delivers an RNA genome, and the delivered gene of interest is expressed by the host cell. As used herein, the terms "virus-like particle" and "VLP" refer to particles that are similar to viruses but are not infectious or transducing because they do not contain viral genetic material encoding the proteins of the virus-like particle. Expression of viral structural proteins (e.g., envelope proteins or capsid proteins) can result in the assembly of virus-like particles. Virus-like particles can be used to deliver proteins and / or nucleic acids to the cytoplasm of target cells. As used herein, the term "plasmid" refers to a circular double-stranded DNA that contains one or more sequences of interest (e.g., sequences encoding one or more specific proteins). In some embodiments, the plasmid can further include regulatory sequences or other genetic elements operably linked to the sequence encoding the specific protein. As used herein, the terms "viral membrane fusion protein", "membrane fusion protein", "fusion protein", and "fusogen" refer to polypeptides that cause or enhance the fusion of biological membranes (e.g., viral envelope and cell wall). A viral membrane fusion protein can be a transmembrane protein or a functional fragment or derivative thereof. As used herein, the term "cell" generally refers to a biological cell. A cell can be the basic structural, functional, and / or biological unit of a living organism. A cell can be derived from any organism having one or more cells. Some non-limiting examples include: prokaryotic cells, eukaryotic cells, bacterial cells, archaeal cells, cells of unicellular eukaryotes, protozoan cells, cells from plants (e.g., cells from plant crops, fruits, vegetables, grains, soybeans, corn, maize, wheat, seeds, tomatoes, rice, cassava, sugarcane, pumpkins, hay, potatoes, cotton, hemp, tobacco, flowering plants, conifers, gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses), algal cells (e.g., Botryococcus braunii, Chlamydomonas reinhardtii, Nannochloropsis gaditana, Chlorella pyrenoidosa, Sargassum patens, etc.), seaweed cells (e.g., kelp), fungal cells (e.g., yeast cells, cells from mushrooms), cells from invertebrates (e.g., Drosophila, cnidarians, echinoderms, nematodes, mollusks, etc.), cells from vertebrates (e.g., fish, amphibians, reptiles, birds, mammals), cells from mammals (e.g., pigs, cows, goats, sheep, rodents, rats, mice, non-human primates, humans, etc.), etc. Sometimes cells are not derived from natural organisms (e.g., cells can be synthetically prepared, sometimes referred to as artificial cells). As used herein, the term "variant" when used in the context of the polypeptides described herein, refers to polypeptides that have a high degree of structural similarity to each other, the structural differences being due to different polynucleotides encoding the polypeptide variants. Polypeptide variants can have amino acid sequences that are at least 80% similar to each other (% identity), e.g., at least 81%, at least 82%, at least 83%, at least 84%, 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%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% similar to each other. Polypeptide variants can have the same biological function as each other. For example, when the polypeptide variants are enzymes, the polypeptide variants can each catalyze the same reaction. Alternatively, variants of the original polypeptide can be specifically configured or selected to lack the biological activity or function of the original polypeptide. As used herein, the term "antibody" refers to a polypeptide of the immunoglobulin family or a polypeptide comprising an immunoglobulin fragment capable of binding to a corresponding antigenic epitope in a non-covalent, reversible, and specific manner. The term includes, but is not limited to, polyclonal or monoclonal antibodies of the isotype classes IgA, IgD, IgE, IgG, and IgM derived from human or other mammalian cells, including native or genetically modified forms such as humanized, human, single-chain, chimeric, synthetic, recombinant, hybrid, mutant, grafted, and in vitro-generated antibodies. The term includes conjugates, including but not limited to proteins comprising an immunoglobulin portion (e.g., chimeric or bispecific antibodies or single-chain Fv's (scFv's)) and fragments such as Fab, F(ab')2, Fv, scFv, Fd, dAb, and other compositions. As used herein, the terms "single-chain variable fragment", "single-chain Fv", and "scFv" refer to an antibody in which the variable regions of the heavy and light chains of a conventional two-chain antibody have been joined to form a single chain. Typically, a linker peptide is inserted between the two chains to allow proper folding and the generation of an active binding site. As used herein, the term "nanobody" or "single-domain antibody" refers to an antibody fragment comprising a single monomeric variable antibody domain, having a molecular weight of less than 20 kDa, and capable of selectively binding to a designated antigen. As used herein, the term "epitope" refers to the localization site on an antigen that is recognized and bound by an antibody. A protein epitope can include several amino acids or portions of several amino acids, such as 5 or 6 or more, or 20 or more amino acids or portions of these amino acids. An epitope can also include non-protein components, such as nucleic acids (e.g., RNA or DNA), carbohydrates, lipids, or combinations thereof. An epitope can be a three-dimensional moiety. Thus, for example, when the target is a protein target, the epitope can include contiguous amino acids, or amino acids from different portions of the protein that are brought into proximity by protein folding (e.g., a discontinuous epitope). The same is true for other types of target molecules that form three-dimensional structures (e.g., DNA and chromatin). As used herein, the term "specifically (or selectively) binds" or, when referring to an antibody interaction, "specifically (or selectively) immunoreacts with" refers to a binding reaction between two molecules under physiological conditions that is at least twice the background and more typically exceeds background molecular binding by 10 to 100-fold. When using one or more detectable protein conjugates, specific binding determines the presence of that protein in a heterogeneous population of proteins and other biological agents. Thus, under specified immunoassay conditions, a designated antibody binds to a specific protein sequence, thereby identifying its presence. Under such conditions, specific binding to an antibody requires selection of an antibody that is specific for a particular protein. For example, antibodies can be selected that are directed against a particular protein, polymorphic variant, allele, ortholog, and conservatively modified variant, or splice variant, or a portion thereof, to obtain those polyclonal antibodies that specifically immunoreact with only the protein of interest and not other proteins. This selection can be achieved by subtracting antibodies that cross-react with other molecules. A variety of immunoassay formats can be used to select antibodies that specifically immunoreact with a particular protein. For example, solid-phase ELISA immunoassays are commonly used to select antibodies that specifically immunoreact with a protein (see, e.g., Harlow & Lane, Antibodies, A Laboratory Manual (1988), which describes immunoassay formats and conditions that can be used to determine specific immunoreactivity). Methods for determining whether two molecules specifically interact are disclosed herein, and methods for determining binding affinity and specificity are well known in the art (see, e.g., Harlow and Lane, Antibodies: A laboratory manual (Cold Spring Harbor Laboratory Press, 1988); Friefelder, "Physical Biochemistry: Applications to biochemistry and molecular biology" (W.H. Freeman and Co. 1976)). As used herein, the terms "switch receptor" and "chimeric switch receptor" refer to molecules designed to convert a negative signal transduction signal into a positive signal. A switch receptor can be a chimeric protein that comprises a first protein or fragment thereof associated with a negative signal, and a second protein or fragment thereof associated with a positive signal. Examples of proteins associated with a negative signal include, but are not limited to, CTLA-4, PD-1, BTLA, TIM-3, etc. Examples of proteins associated with a positive signal include, but are not limited to, CD28, ICOS, 4-1BB, TGFβR, etc. As used herein, the term "selection marker" refers to a gene encoding a protein that permits identification and / or isolation of cells expressing the gene from other cells in a population. Selection markers include, but are not limited to, genes encoding drug resistance, fluorescence, and essential genes for growth under restrictive conditions. As used herein, the term "subject" refers to a vertebrate, and preferably a mammal. Mammalian subjects to which the provided compositions are applicable include, but are not limited to, mice, rats, apes, humans, farm animals, sport animals, and pets. In some embodiments, the subject is a human. In some embodiments, the subject is male. In some embodiments, the subject is female. In some embodiments, the subject is an adult. In some embodiments, the subject is an adolescent. In some embodiments, the subject is a child. In some embodiments, the subject is over 10 years of age, such as over 20 years of age, over 30 years of age, over 40 years of age, over 50 years of age, over 60 years of age, over 70 years of age, or over 80 years of age. In some embodiments, the subject is under 80 years of age, such as under 70 years of age, under 60 years of age, under 50 years of age, under 40 years of age, under 30 years of age, under 20 years of age, or under 10 years of age. As used herein, the term "administer" refers to oral administration to a subject, administration as a suppository, topical contact, parenteral, intravenous, intraperitoneal, intramuscular, intralesional, intranasal, or subcutaneous administration, intrathecal administration, or implantation of a sustained release device (e.g., a micro-osmotic pump). As used herein, the term "treat / treatment" refers to any procedure that successfully eliminates or ameliorates signs of an injury, condition, disorder, or symptom (e.g., pain), including any objective or subjective parameter, such as elimination; alleviation; reduction of symptoms or making symptoms, injury, condition, or disorder more tolerable to the patient; decreasing the frequency or duration of the symptoms or disorder; or, in some instances, preventing the onset of the symptoms. Treatment or amelioration of a symptom can be based on any objective or subjective parameter; including, for example, the results of a physical examination. As used herein, the terms "pharmaceutically acceptable excipient" and "pharmaceutically acceptable carrier" refer to substances that aid in the administration of an active agent to a subject and are absorbed by the subject, and can be included in the compositions of the present disclosure without causing a significant adverse toxicological effect to the subject. Non-limiting examples of pharmaceutically acceptable excipients and carriers include water, NaCl, saline solution, common sucrose, common glucose, binders, fillers, disintegrants, lubricants, coatings, and the like. Those skilled in the art will recognize that other pharmaceutically acceptable excipients and carriers can be used in the present disclosure. As used herein, the term "therapeutically effective amount" refers to the amount or dose of a compound, composition, or formulation that, when administered, produces a therapeutic effect. The exact amount or dose depends on the purpose of the treatment and is determined by those skilled in the art using known techniques (see, e.g., Lieberman, Pharmaceutical Dosage Forms (vols. 1-3, 1992); Lloyd, The Art, Science and Technology of Pharmaceutical Compounding (1999); Pickar, Dosage Calculations (1999); and Remington: The Science and Practice of Pharmacy, 20th Edition, 2003, Gennaro, Ed., Lippincott, Williams & Wilkins). As used herein, the term "vaccine" refers to a composition that contains at least one antigen or immunogen in a pharmaceutically acceptable carrier, or a composition that contains a nucleic acid molecule encoding at least one antigen or immunogen, which can be used to induce an immune response against the antigen or immunogen in a subject to enhance the subject's immunity to a disease and / or infection. As used herein, the singular form "a / an" includes plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a polymer" optionally includes combinations of two or more polymers, etc. As used herein, the term "and / or" refers to and includes any and all possible combinations of one or more of the associated listed items, as well as no combinations when stated in the alternative ("or"). As used herein, the terms "comprising", "including", "having", "containing", and variations thereof are inclusive and open-ended and do not exclude additional unstated elements or method steps other than those expressly recited. As used herein, the phrase "consisting of" is closed and excludes any element, step, or ingredient not expressly specified. As used herein, the phrase "consisting essentially of" limits the scope of the described features to the specified materials or steps and those materials or steps that do not materially affect the basic and novel features of the disclosed features. III. Retroviral Vector Systems In one aspect of the present disclosure, a retroviral vector system is provided. The vector system includes a plasmid that can be used to transform retroviral packaging cells, enabling the cells to produce retroviruses according to the contents of the vector system. Thus, the disclosed retroviral vector system can provide many unexpected advantages discussed herein, particularly when used in therapeutic applications such as gene therapy or cell therapy. For example, the retroviral vector system can be used as a tool for producing retroviruses that are engineered to specifically and / or selectively transduce one or more specific cell types or populations. In some aspects, the engineered retroviruses produced using the retroviral vector system can also advantageously have easily switchable cell specificities. Such switchable specificities can be achieved, for example, by using a simple procedure to change the binding moiety of the retrovirus or to change a second conjugate (e.g., an antibody) conjugated to the retroviral binding moiety. The provided retroviral vector system includes one or more envelope plasmids, one or more packaging plasmids, and one or more transfer plasmids. An advantage of the vector system provided by the present invention is that a small number of plasmids can effectively transfect viral packaging cells to enable the cells to produce functional retroviruses having the binding moieties disclosed herein. In some embodiments, the retroviral vector system includes only one envelope plasmid. In some embodiments, the retroviral vector system includes only one packaging plasmid. In some embodiments, the retroviral vector system includes only one transfer plasmid. In some embodiments, the retroviral vector system includes only one envelope plasmid and one packaging plasmid. In some embodiments, the retroviral packaging system includes only one envelope plasmid and one transfer plasmid. In some embodiments, the retroviral vector system includes only one packaging plasmid and one transfer plasmid. In some embodiments, the retroviral vector system includes only one envelope plasmid, one packaging plasmid, and one transfer plasmid. The envelope plasmid of the provided retroviral vector system generally encodes the viral membrane fusion protein of the retrovirus produced by the viral packaging cells transfected with the vector system. The packaging plasmid of the retroviral vector system generally encodes the Gag-Pol protein of the retrovirus. The transfer plasmid of the retroviral vector system generally encodes one or more genes of interest transferred from the retrovirus to the target cells. At least one plasmid of the provided retroviral vector system encodes a binding moiety that binds directly or indirectly to a target cell surface feature. Encoding the binding moiety in one of the plasmids of the vector system advantageously ensures that all retroviruses produced using the system include the binding moiety. In some embodiments, only one plasmid in the retroviral vector system encodes the binding moiety. In some embodiments, two or more different plasmids in the retroviral vector system encode the binding moiety. In some embodiments, each different plasmid in the retroviral vector system encodes the binding moiety. For certain applications, it is desirable to encode the binding moiety using only one or both of the envelope plasmid and the packaging plasmid and not the transfer plasmid. In this way, the binding moiety will not integrate into the host cell genome targeted by the retroviruses produced using the vector system. In some embodiments, only one or more envelope plasmids encode the binding moiety. In some embodiments, only one or more packaging plasmids encode the binding moiety. In some embodiments, the envelope plasmid and the packaging plasmid each encode the binding moiety, and the transfer plasmid does not encode the binding moiety. The binding moiety of the provided retroviral vector system generally includes an extracellular domain, wherein the extracellular domain is a binding domain that recognizes a target cell surface feature or recognizes a second binding partner that recognizes the target cell surface feature. In some embodiments, the binding moiety includes a transmembrane domain that localizes the binding moiety in the envelope of the retrovirus. In some embodiments, the extracellular domain of the binding moiety is fused to the transmembrane domain of another viral envelope protein. The binding moiety can be encoded directly upstream of the envelope protein of the envelope plasmid of the provided retroviral vector system. The binding moiety can be encoded directly downstream of the envelope protein of the envelope plasmid ( Figure 2 ). The binding moiety can be encoded directly upstream of the Gag-Pol protein of the packaging plasmid of the retroviral vector system. The binding moiety can be encoded directly downstream of the Gag-Pol protein of the packaging plasmid. In some embodiments, the binding moiety is separated from the adjacent protein of the plasmid post-translationally, for example using a 2A tag. In some embodiments, the binding moiety of the provided retroviral vector system is designed or selected to bind to a ligand, wherein the ligand is designed or selected to bind to a target cell, such as to a surface feature of the target cell ( Figure 1 ). In some embodiments, the ligand bound by the binding moiety includes an antibody, an antibody mimetic, a single-chain variable fragment (scFv), or a derivative or fragment thereof. In such embodiments, the binding moiety can be described as including an antibody binding domain (ABD). In some embodiments, the ligand is a conjugated derivative of an antibody, an antibody mimetic, or an scFv, wherein the ligand is conjugated to a small molecule recognized by the binding moietyFigure 5 )。Using this method, a retroviral vector system can be engineered to be used for generating universal pseudotyped retroviruses. Each of these universal pseudotyped retroviruses includes a binding moiety that binds to a specific small molecule, and any conjugate between the ligand and the small molecule can be readily generated, such that the ligand is compatible with the binding moiety having an affinity for the specific small molecule of the conjugate. In this way, if a ligand-small molecule conjugate specific for a cell type is applied, a single universal design of the provided retroviruses (e.g., retroviruses generated using the provided retroviral vector system) can specifically bind to a specific cell type. In some embodiments, the binding moiety includes a fluorescein isothiocyanate (FITC) binding domain, and the ligand is FITC-conjugated. For example, the binding moiety can include an anti-fluorescein scFv or a fluorescein-binding anticalin. The ligand recognized by this binding moiety can be, for example, a FITC-conjugated antibody. Due to the availability of FITC-conjugated antibodies specific for a variety of different cell-specific antigens, a single design of a universal pseudotyped retrovirus having a FITC binding moiety can specifically transduce a variety of cell types. In some embodiments, the binding moiety includes a biotin binding domain, and the ligand is biotin-conjugated. For example, the binding moiety can include an anti-biotin scFv, a biotin-binding anticalin, or an avidin family protein, such as avidin or streptavidin. The ligand recognized by this binding moiety can be, for example, a biotin-conjugated antibody. Due to the availability of biotin-conjugated antibodies specific for a variety of different cell-specific antigens, a single design of a universal pseudotyped retrovirus having a biotin binding moiety can specifically transduce a variety of cell types. The ligand recognized by the antibody binding domain of the provided binding moiety itself can bind to various surface features of the target cell. Many off-the-shelf antibodies applicable to the provided materials and methods are available, and the available antibodies have different specificities and selectivities for various antigens and epitopes. Other antibodies and antibody conjugates can also be developed for binding other target cell surface features. For example but not limited to, the ligand can be used to indirectly bind the provided binding moiety to one or more of CD3, CD4, CD7, CD8, CD19, CD20, CD56, CD71, or CTLA4. In some embodiments, the binding moiety of the provided retroviral vector system is designed or selected to directly bind to the target cell, e.g., to a surface feature of the target cell ( Figure 1)。In such embodiments, the binding moiety can be described as including a cell-binding domain (CBD). In some embodiments, the cell-binding domain includes an antibody, antibody mimetic, scFv, nanobody, another ligand, or a derivative or fragment thereof. Similar to the binding moiety including an antibody-binding domain, the binding moiety including a cell-binding domain can also bind to various surface features of target cells. For example, but not limited to, the cell-binding domain can be designed or selected such that the provided binding moiety binds to one or more of CD3, CD4, CD7, CD8, CD19, CD20, CD56, CD71, or CTLA4. The provided retroviral vector system can target a variety of cell types. In some embodiments, the target cells are immune cells, including any cells involved in the immune response. For example, targeting of immune cells (such as optionally allogeneic natural NK cells, iPSC-derived NK cells, and / or macrophages) can greatly facilitate the treatment of solid tumors while avoiding side effects. In this way, the provided retroviral vector system can mediate precise activation of immunity at a precise location (e.g., the presence of local tumor signals) and at a specified time point. In some embodiments, the target cells include granulocytes, such as basophils, eosinophils, and neutrophils; mast cells; monocytes, which can develop into macrophages; antigen-presenting cells, such as dendritic cells; and lymphocytes, such as natural killer cells (NK cells), B cells, and T cells. In some embodiments, the target cells are immune effector cells. Immune effector cells are immune cells that can perform specific functions in response to stimulation. In some embodiments, the target cells are immune effector cells that can be induced to undergo cell death. In some embodiments, the target cells are lymphocytes. In some embodiments, the lymphocytes are NK cells. In some embodiments, the lymphocytes are T cells. In some embodiments, the T cells are activated T cells. T cells include naive cells and memory cells (such as central memory or T CM 、effector memory or T EM and effector memory RA or T EMRA ), effector cells (such as cytotoxic T cells or CTL or Tc cells), helper cells (such as Th1, Th2, Th3, Th9, Th7, TFH), regulatory cells (such as Treg and Trl cells), natural killer T cells (NKT cells), tumor-infiltrating lymphocytes (TIL), lymphocyte-activated killer cells (LAK), αβΤ cells, γδΤ cells, and distinct classes of similar T cell lineages. T cells can be divided into two major categories based on the proteins present on their cell surface: CD8+ T cells and CD4+ T cells. T cells can perform a variety of functions, including killing infected cells and activating or recruiting other immune cells. CD8+ T cells are called cytotoxic T cells or cytotoxic T lymphocytes (CTLs). CD4+ T cells can be subdivided into four subsets: Th1, Th2, Th17, and Treg, where "Th" refers to "helper T cell", although there may be other subsets. Th1 cells can coordinate the immune response against intracellular microorganisms, especially bacteria. They can produce and secrete molecules that alert and activate other immune cells, such as bacterium-phagocytosing macrophages. Th2 cells are involved in coordinating the immune response against extracellular pathogens, such as intestinal worms (parasites), by alerting B cells, granulocytes, and mast cells. Th17 cells can produce interleukin 17 (IL-17), which is a signaling molecule that activates immune and non-immune cells. Th17 cells are important for recruiting neutrophils. Retroviral vector systems can be engineered to target cell types that mediate cell differentiation and programming. This can allow for site-specific differentiation of cells and tissues to repair or renew damaged or aging bodies. In some embodiments, the target cells are stem cells. The target cells can be, for example, induced pluripotent stem cells (iPSCs), embryonic stem cells (ESCs), adult stem cells, or mesenchymal stem cells (MSCs). In some embodiments, the target cells are progenitor cells. The target cells can be, for example, neural progenitor cells, skeletal progenitor cells, muscle progenitor cells, adipose progenitor cells, cardiac progenitor cells, chondrocytes, or pancreatic progenitor cells. In some embodiments, the provided retroviral vector system is designed to produce retroviruses that target cells of one or more specified tissues. These embodiments are particularly useful when the retroviral vector system is used to produce retroviruses for in situ engineering or treatment of these specified tissues. In some embodiments, the target cells include muscle cells. In some embodiments, the target cells include nerve cells. In some embodiments, the target cells include pancreatic cells, such as islets of Langerhans. In some embodiments, the provided retroviral vector system is designed to produce retroviruses that target two or more different cell types, where different payloads are delivered to each of the different cell types. For example, the retroviral vector system can include a FITC-binding domain that recognizes a FITC-conjugated antibody, where the FITC-conjugated antibody targets a first antigen for delivery of a first payload. The same retroviral vector system can further include a biotin-binding domain that recognizes a biotin-conjugated antibody, where the biotin-conjugated antibody targets a second antigen for delivery of a second payload. The provided retroviral vector systems can be used to deliver any genetically encoded material. The systems and the retroviruses they generate can be used to deliver, for example, human genes, chimeric genes and engineered genes, gene editors, and genes from other species. In some embodiments, the vector systems transfer plasmid genes encoding receptors, including but not limited to chimeric antigen receptors (CARs) (including first-generation, second-generation, third-generation, or fourth-generation receptors), switch receptors, MIMIC receptors, or modified forms thereof. In some embodiments, the transferred vector genes include one or more nucleases, such as CRISPR-associated (Cas) proteins or Cas nucleases, including type I CRISPR-associated (Cas) polypeptides, type II CRISPR-associated (Cas) polypeptides, type III CRISPR-associated (Cas) polypeptides, type IV CRISPR-associated (Cas) polypeptides, type V CRISPR-associated (Cas) polypeptides, and type VI CRISPR-associated (Cas) polypeptides; zinc finger nucleases (ZFNs); transcription activator-like effector nucleases (TALENs); meganucleases; RNA-binding proteins (RBPs); CRISPR-associated RNA-binding proteins; recombinases; flippases; transposases; Argonaute (Ago) proteins (e.g., prokaryotic Argonaute (pAgo), archaeal Argonaute (aAgo), eukaryotic Argonaute (eAgo), and Natronobacterium gregoryi Argonaute (NgAgo)); adenosine deaminases acting on RNA (ADARs); CIRT, PUF, homing endonucleases, or any functional fragment, derivative, or variant thereof. In some embodiments, the transferred vector genes include one or more reporter genes or selectable markers, such as fluorescent proteins, antibiotic resistance genes, or derivatives or fragments thereof. In some embodiments, the provided transfer plasmids contain more than one gene in one or more polycistronic elements. In some embodiments, the retroviral vector systems can be used to generate retroviruses that transduce host cells to express more than one gene of the polycistronic element using, for example, an IRES or a 2A tag. In some embodiments, the transfer plasmids include one or more regulatory elements that can regulate the expression of the transduced genes, such as promoters, introns, enhancers, post-transcriptional elements, or post-translational elements. In some embodiments, the viral membrane fusion protein of the provided retroviral vector system envelope plasmid is the vesicular stomatitis virus G (VSV-G) protein or an engineered variant thereof. In some embodiments, the viral membrane fusion protein is the membrane fusion protein from feline endogenous virus RD114 or an engineered variant thereof. In some embodiments, the viral membrane fusion protein is the membrane fusion protein from baboon endogenous virus BaEV or an engineered variant thereof. In some embodiments, the viral membrane fusion protein is an engineered variant that does not bind to the cognate binding partner of the corresponding wild-type viral membrane fusion protein. This is particularly advantageous for applications where it is important to ensure that retroviruses produced using a retroviral vector system are dependent on the binding moiety of the vector system for host cell targeting and transduction. In some embodiments, the engineered variant comprises one or more, such as two or more, point mutations in the wild-type viral membrane fusion protein sequence such that the protein loses its cognate binding ability. In some embodiments, the engineered variant is a truncated mutant of the wild-type viral membrane fusion protein such that the protein loses its cognate binding ability. In some embodiments, the integrase of the provided retroviral vector system is mutated such that the vector system can be used to produce integrase-deficient retroviruses. This is particularly advantageous for applications that aim to deliver genetic information to target cells without causing stable integration of that information into the target cell genome. IV. Retroviral packaging cells In another aspect of the present disclosure, retroviral packaging cells are provided. A retroviral packaging cell is a cell that has been transformed with any of the provided retroviral vector systems, such as any of those described in Part III. Thus, retroviral packaging cells can offer many of the unexpected advantages discussed herein, particularly when used in therapeutic applications such as gene therapy or cell therapy. For example, retroviral packaging cells can be used as a tool for producing retroviruses that are engineered to specifically and / or selectively transduce one or more specific cell types or populations. In certain aspects, the engineered retroviruses produced using retroviral packaging cells can also advantageously have easily switchable target cell specificities. Such switchable specificities can be achieved, for example, by using a simple procedure to change the binding moiety of the retrovirus or to change a second conjugate (e.g., an antibody) conjugated to the retroviral binding moiety. In another aspect, a retroviral packaging cell population is provided. In some embodiments, each host cell of the population independently comprises a retroviral vector system as disclosed herein. Also provided is a cell culture comprising the cell population as described herein. Methods for culturing and producing many cells are available in the art, including cells of bacterial (e.g., E. coli and other bacterial strains), animal (particularly mammalian), and archaeal origin. See, for example, Sambrook, supra; Ausubel, ed. (1995) Current Protocols in Molecular Biology, John Wiley & Sons, as well as Freshney (1994) Culture of Animal Cells, a Manual of Basic Technique, 3 rd Ed., Wiley-Liss, New York and references cited therein; Doyle and Griffiths (1997) Mammalian Cell Culture: Essential Techniques John Wiley and Sons, NY; Humason (1979) Animal Tissue Techniques, 4 th Ed. W.H. Freeman and Company; and Ricciardelli, et al., (1989) In vitro Cell Dev. Biol. 25:1016-1024. V. Retroviruses In another aspect of the present disclosure, retroviruses are provided. In some embodiments, any provided retroviral vector system and / or retroviral packaging system can be used to produce retroviruses. Thus, retroviruses can provide the unexpected advantages discussed herein, including broad applicability, high specificity and selectivity, switchable targeting, and universal pseudotyping. The provided retroviruses include viral membrane fusion proteins. The viral membrane fusion proteins can be any of those disclosed herein with respect to retroviral vector systems. The provided retroviruses further include a viral genome, which includes one or more genes of interest transferred from the retrovirus to a target cell. The gene of interest and the target cell can be achieved by any of those disclosed herein with respect to retroviral vector systems. The provided retroviruses further include a binding moiety, which can be any of those disclosed herein with respect to retroviral vector systems. In some embodiments, the binding moiety includes any type of antibody binding domain (ABD) disclosed herein. For example, the binding moiety of the provided retrovirus can include a ligand that is an antibody, antibody mimetic, single-chain variable fragment (scFv), or a derivative or fragment thereof, wherein the ligand binds to a surface feature of the target cell. VI. Virus-like particles In another aspect of the present disclosure, virus-like particles are provided. The virus-like particles include many of the same advantages of the provided retroviruses, including broad applicability, high specificity and high selectivity, switchable targeting, and universal pseudotyping. Different from the provided retroviruses, the virus-like particles do not include a viral genome and thus cannot be used to integrate the delivered genetic material into the genome of the target cell. Thus, the virus-like particles provide an attractive alternative to retroviruses in cases where integration is not required. The provided virus-like particles include a binding moiety, which can be any of those disclosed herein with respect to retroviral vector systems. In some embodiments, the binding moiety includes any type of antibody binding domain (ABD) disclosed herein. For example, the binding moiety of the provided retrovirus can include a ligand that is an antibody, antibody mimetic, single-chain variable fragment (scFv), or a derivative or fragment thereof, wherein the ligand binds to a surface feature of the target cell. VII. Methods for preventing or treating diseases In another aspect of the present disclosure, a method for preventing or treating a disease is provided. The method includes administering to a subject any of the retroviral vector systems, retroviral packaging cells, retroviruses, or virus-like particles disclosed herein, such as in Sections III, IV, V, and VI. A pharmaceutical composition (e.g., as described in Section IX) comprising the retroviral vector system, retroviral packaging cell, retrovirus, or virus-like particle described herein can be administered for prophylactic and / or therapeutic treatment. In a therapeutic application, these compositions can be administered to a subject already suffering from a disease or disorder in an amount sufficient to cure or at least partially arrest the symptoms of the disease or disorder, or to cure, alleviate, ameliorate, or improve the disorder. The effective amount for this use can vary depending on the severity and course of the disease or disorder, previous treatment, the health status, body weight, and response of the subject to the drug, and the judgment of the treating physician. The retroviral vector system, retroviral packaging cell, retrovirus, or virus-like particle described herein can be administered before, during, or after the occurrence of a disease or disorder, and the time of administration of the composition can vary. For example, the pharmaceutical composition can be used as a prophylactic agent and can be administered continuously to a subject having a disorder or a predisposition to a disease to prevent the occurrence of the disease or disorder. The pharmaceutical composition can be administered to the subject during the onset of symptoms or as soon as possible after the onset of symptoms. The administration can be initiated within 48 hours, within 24 hours, within 6 hours, or within 3 hours of the onset of symptoms. The initial administration can be carried out by any feasible route, such as by any of the routes described herein using any of the formulations described herein. The composition can be administered as soon as a disease or disorder is detected or suspected to have occurred and can be administered for a period of time required to treat the disease, such as from about 1 month to about 3 months. The length of treatment can vary for each subject. A variety of diseases can be prevented or treated using the provided method. The method is suitable for a wide range of cell or gene therapy applications to treat, for example, blood cancers or solid cancers, viral infections, bacterial infections, genetic diseases, wound healing, autoimmunity, regenerative medicine, CNS diseases, and anti-aging. In some embodiments, the disease to be prevented or treated is a genetic disease. Conditions suitable for treatment with the provided methods include, but are not limited to, X-linked severe combined immunodeficiency, sickle cell anemia, thalassemia, hemophilia, neoplasia, cancer, age-related macular degeneration, schizophrenia, trinucleotide repeat diseases, fragile X syndrome, prion-related diseases, amyotrophic lateral sclerosis, drug addiction, autism, Alzheimer's disease, Parkinson's disease, cystic fibrosis, blood and blood clotting diseases or disorders, inflammation, facioscapulohumeral muscular dystrophy, retinitis pigmentosa, Leber congenital amaurosis, glaucoma, immune-related diseases or disorders, metabolic diseases and disorders, liver diseases and disorders, kidney diseases and disorders, muscle / skeletal diseases and disorders, nerve and neuronal diseases and disorders, cardiovascular diseases and disorders, pulmonary diseases and disorders, and eye diseases and disorders. In some embodiments, the disease to be prevented or treated is cancer. Non-limiting examples of cancers that can be treated with the provided retroviral vector system, retroviral packaging cells, retroviruses, or virus-like particles include acanthoma, acinar cell carcinoma, acoustic neuroma, acral lentiginous melanoma, acrospiroma, acute eosinophilic leukemia, acute lymphoblastic leukemia, acute megakaryocytic leukemia, acute monocytic leukemia, acute myeloblastic leukemia, acute myeloid dendritic cell leukemia, acute myeloid leukemia, acute promyelocytic leukemia, adamantinoma, adenocarcinoma, adenoid cystic carcinoma, adenoma, adenomatoid odontogenic tumor, adrenocortical carcinoma, adult T-cell leukemia, aggressive NK-cell leukemia, AIDS-related cancers, AIDS-related lymphomas, alveolar soft part sarcoma, ameloblastic fibroma, anal cancer, anaplastic large cell lymphoma, anaplastic thyroid cancer, angioimmunoblastic T-cell lymphoma, angiomyolipoma, angiosarcoma, appendiceal cancer, astrocytoma, atypical teratoid rhabdoid tumor, basal cell carcinoma, basaloid carcinoma, B-cell leukemia, B-cell lymphoma, Bellini duct carcinoma, bile duct cancer, bladder cancer, blastoma, bone cancer, bone tumor, brainstem glioma, brain tumor, breast cancer, Brenner tumor, bronchial tumor, bronchioloalveolar carcinoma, brown tumor, Burkitt's lymphoma, carcinoma of unknown primary site, carcinoid tumor, carcinoma, carcinoma in situ, carcinoma of the penis, carcinoma of unknown primary site, carcinosarcoma, Castleman's disease, central nervous system embryonal tumor, cerebellar astrocytoma, cerebral astrocytoma, cervical cancer, cholangiocarcinoma, chondroma, chondrosarcoma, chordoma, choriocarcinoma, choroid plexus papilloma, chronic lymphocytic leukemia, chronic monocytic leukemia, chronic myeloid leukemia, chronic myeloproliferative disorders, chronic neutrophilic leukemia, clear cell tumor, colon cancer, colorectal cancer, craniopharyngioma, cutaneous T-cell lymphoma, Degos disease, dermatofibrosarcoma protuberans, dermoid cyst, desmoplastic small round cell tumor, diffuse large B-cell lymphoma, dysembryoplastic neuroepithelial tumor, embryonal carcinoma, endodermal sinus tumor, endometrial cancer, endometrial carcinoma of the uterus, endometrioid tumor, enteropathy-associated T-cell lymphoma, ependymoblastoma, ependymoma, epithelioid sarcoma, erythroleukemia, esophageal cancer, olfactory neuroblastoma, Ewing family tumors, Ewing family sarcoma, Ewing sarcoma, extracranial germ cell tumor, extragonadal germ cell tumor, extrahepatic bile duct cancer, extramammary Paget's disease, fallopian tube cancer, fetus in fetu, fibroma, fibrosarcoma, follicular lymphoma, follicular thyroid cancer, gallbladder cancer, gallbladder carcinoma, ganglioglioma, ganglioneuroma, gastric cancer, gastric lymphoma, gastrointestinal cancer, gastrointestinal carcinoid, gastrointestinal stromal tumor, gastrointestinal stromal tumor, germ cell tumor, germinoma, gestational choriocarcinoma, gestational trophoblastic tumor, giant cell tumor of bone,Glioblastoma multiforme, glioma, gliomatosis cerebri, glomus tumor, glucagonoma, gonadoblastoma, granulosa cell tumor, hairy cell leukemia, hairy cell leukemia, head and neck cancer, head and neck cancer, cardiac cancer, hemangioblastoma, hemangiopericytoma, angiosarcoma, hematological malignancies, hepatocellular carcinoma, hepatosplenic T-cell lymphoma, hereditary breast-ovarian cancer syndrome, Hodgkin lymphoma, Hodgkin lymphoma, hypopharyngeal cancer, hypothalamic glioma, inflammatory breast cancer, intraocular melanoma, islet cell carcinoma, islet cell tumor, juvenile myelomonocytic leukemia, Kaposi sarcoma, Kaposi sarcoma, renal cancer, Klatskin tumor, Krukenberg tumor, laryngeal cancer, laryngeal cancer, lentigo maligna melanoma, leukemia, leukemia, lip and oral cavity cancer, liposarcoma, lung cancer, luteoma, lymphangioma, lymphangiosarcoma, lymphoepithelioma, lymphoid leukemia, lymphoma, macroglobulinemia, malignant fibrous histiocytoma, malignant fibrous histiocytoma, malignant fibrous histiocytoma of bone, malignant glioma, malignant mesothelioma, malignant peripheral nerve sheath tumor, malignant rhabdoid tumor, malignant triton tumor, mucosa-associated lymphoid tissue (MALT) lymphoma, mantle cell lymphoma, mast cell leukemia, mediastinal germ cell tumor, mediastinal tumor, medullary thyroid cancer, medulloblastoma, medulloblastoma, medulloepithelioma, melanoma, melanoma, meningioma, Merkel cell carcinoma, mesothelioma, mesothelioma, metastatic squamous cell carcinoma of the neck of unknown primary, metastatic urothelial carcinoma, Mullerian mixed tumor, monocytic leukemia, oral cancer, mucinous tumor, multiple endocrine neoplasia syndrome, multiple myeloma, multiple myeloma, mycosis fungoides, mycosis fungoides, myelodysplastic disorders, myelodysplastic syndrome, myeloid leukemia, myeloid sarcoma, myeloproliferative disorders, myxoma, nasal cavity cancer, nasopharyngeal cancer, nasopharyngeal cancer, tumor, schwannoma, neuroblastoma, neuroblastoma, neurofibroma, neuroma, nodular melanoma, non-Hodgkin lymphoma, non-Hodgkin lymphoma, non-melanoma skin cancer, non-small cell lung cancer, ocular oncology, oligoastrocytoma, oligodendroglioma, oxyphil cell tumor, optic nerve sheath meningioma, oral cancer, oral cancer, oropharyngeal cancer, osteosarcoma, osteosarcoma, ovarian cancer, ovarian cancer, ovarian epithelial cancer, ovarian germ cell tumor, ovarian tumor of low malignant potential, Paget disease of the breast, Pancoast tumor, pancreatic cancer, pancreatic cancer, papillary thyroid cancer, papillomatosis, paraganglioma, sinus cancer, parathyroid carcinoma, penile cancer, perivascular epithelioid cell tumor, pharyngeal cancer, pheochromocytoma, moderately differentiated pineal parenchymal tumor, pineoblastoma, pituitary cell tumor, pituitary adenoma, pituitary tumor, plasma cell tumor, thoracopulmonary blastoma, polyembryoma, precursor T-lymphoblastic lymphoma, primary central nervous system lymphoma, primary effusion lymphoma, primary hepatocellular carcinomaPrimary liver cancer, primary peritoneal cancer, primitive neuroectodermal tumor, prostate cancer, pseudomyxoma peritonei, rectal cancer, renal cell carcinoma, respiratory tract cancer involving the NUT gene on chromosome 15, retinoblastoma, rhabdomyoma, rhabdomyosarcoma, Richter's transformation, sacrococcygeal teratoma, salivary gland cancer, sarcoma, schwannomatosis, sebaceous gland carcinoma, secondary tumor, seminoma, serous tumor, Sertoli-Leydig cell tumor, sex cord-stromal tumor, Sezary syndrome, signet ring cell carcinoma, skin cancer, small round blue cell tumor, small cell carcinoma, small cell lung cancer, small cell lymphoma, small intestine cancer, soft tissue sarcoma, somatostatinoma, seborrheic wart, spinal cord tumor, spinal column tumor, splenic marginal zone lymphoma, squamous cell carcinoma, stomach cancer, superficial spreading melanoma, supratentorial primitive neuroectodermal tumor, surface epithelial-stromal tumor, synovial sarcoma, T-cell acute lymphoblastic leukemia, T-cell large granular lymphocyte leukemia, T-cell leukemia, T-cell lymphoma, T-prolymphocytic leukemia, teratoma, terminal stage lymphoma, testicular cancer, thecoma, laryngeal cancer, thymic carcinoma, thymoma, thyroid cancer, transitional cell carcinoma of the renal pelvis and ureter, transitional cell carcinoma, urachal carcinoma, urethral cancer, urogenital system tumor, uterine sarcoma, uveal melanoma, vaginal cancer, Verner-Morrison syndrome, verrucous carcinoma, visual pathway glioma, vulvar cancer, Waldenstrom's macroglobulinemia, Warthin's tumor, Wilms' tumor, and combinations thereof. In some embodiments, the disease to be prevented or treated is a cancerous tumor. The cancerous tumor can be a solid cancerous tumor or a liquid cancerous tumor. The liquid cancerous tumor can be, for example, lymphoma or leukemia. The tumors treated with the methods disclosed herein can result in stable tumor growth (e.g., one or more tumors increase in size by no more than 1%, 5%, 10%, 15%, or 20%, and / or do not metastasize). In some embodiments, the tumor is stable for at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 weeks or more. In some embodiments, the tumor is stable for at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 months or longer. In some embodiments, the tumor is stable for at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 years or more. In some embodiments, the size of the tumor or the number of tumor cells is reduced by at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or more. In some embodiments, the tumor is completely eliminated or reduced below the level of detection. In some embodiments, the subject remains tumor-free (e.g., in remission) for at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 weeks or more after treatment. In some embodiments, the subject remains tumor-free for at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 months or more after treatment. In some embodiments, the subject remains tumor-free for at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 years or more after treatment. Those skilled in the art will also understand that the provided systems and compositions can be co-administered with other therapeutic agents for the treatment of cancer. Suitable anti-cancer agents for combination therapy include, but are not limited to, cytotoxic agents such as antimetabolites, alkylating agents, anthracyclines, antibiotics, anti-mitotic agents, procarbazine, hydroxyurea, asparaginase, corticosteroids, interferons, radiopharmaceuticals, peptides having anti-tumor activity (such as TNF-α), reagents of their pharmaceutically acceptable salts; derivatives thereof, prodrugs thereof, and combinations thereof. For example, a pharmaceutical composition comprising the provided retroviral vector system, retroviral packaging cells, retroviruses, and / or virus-like particles can be administered to a patient before, during, or after the administration of an anti-cancer agent or combination of anti-cancer agents or before, during, or after chemotherapy. In some embodiments, treatment with the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles results in stable disease, partial remission, or complete remission in a subject (e.g., the methods described herein include administering to a subject a dose of the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles that kills or otherwise slows the growth or progression of cancer cells and results in stable disease or partial or complete remission of cancer in the subject). In some embodiments, treatment with the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles results in a reduction in cancer metastasis in a subject (e.g., the methods described herein include administering to a subject a dose of the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles that reduces cancer metastasis in the subject). In some embodiments, treatment with the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles results in a reduction in the volume, size, or growth of a tumor in a subject (e.g., the methods described herein include administering to a subject a dose of the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles that reduces the volume, size, or growth of a tumor in the subject). In some embodiments, treatment with the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles results in an increased responsiveness of cancer to a subsequently administered anti-cancer agent (e.g., the methods described herein include administering to a subject a dose of the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles that increases the responsiveness of cancer to a subsequently administered anti-cancer agent). In some embodiments, the disease to be prevented or treated is an infectious disease. The infectious disease can be, for example, a viral infectious disease. The infectious disease can be, for example, a bacterial infectious disease. In the case of a bacterial infection, the innate immune system must recognize specific markers of the microbe to clear the pathogen. These pathogen-associated molecular patterns are recognized by various receptors, most notably TLRs that are common to all immune cells, and activate immune pathways that turn on their bactericidal capabilities. In the case of macrophages, recognition of microbial pathogens by TLRs activates their unique ability to autophagocytose bacteria and destroy the pathogen through acidification. However, bacteria have mechanisms to escape macrophages by hiding the molecules that cause such activation. For example, during the implantation of biomedical devices such as catheters and pacemakers, bacteria form dense biofilms around themselves to avoid recognition, leading to a large number of infection problems that have hindered the entry of life-saving technologies into the clinic. The provided retroviral vector system, retroviral packaging cells, retrovirus, or virus-like particles can "reconnect" these TLRs to recognize components of the biofilm itself rather than the bacteria, thereby activating macrophages through the escape mechanism, destroying the infection, and allowing these devices to be implanted more safely. In some embodiments, the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles are administered to a subject one, two, three, four, or five times during a course of treatment. Subsequent administrations of the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles can be made at regular time intervals, at intervals of days, weeks, or months. In some cases, if the tumor or cancer cells reappear, continue to grow, or are not adequately treated after the first administration of the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles, the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles are administered at a subsequent time. In some cases, if the subject does not respond fully, experiences a partial response, a stable response, or disease progression to the first treatment, the provided retroviral vector system, retroviral packaging cells, retrovirus, and / or virus-like particles are administered again at a subsequent time. In some embodiments, the provided method further comprises obtaining a test sample from the subject. The test sample can include, for example, a blood sample, a tissue sample, a urine sample, a saliva sample, a cerebrospinal fluid sample, or a combination thereof. In some embodiments, the provided method further comprises determining the level of one or more biomarkers in the obtained test sample. As a non-limiting example, determining the presence or level of a biomarker can be used to determine the response to treatment or to select a suitable composition for preventing or treating a disease. In some embodiments, the provided method further includes comparing the determined levels of one or more biomarkers in the obtained test sample with the levels of one or more biomarkers in a reference sample. The reference sample can be obtained, for example, from a subject, where the reference sample is obtained prior to obtaining the test sample, such as prior to administering a therapeutically effective amount of the provided material to the subject. In this way, the reference sample can provide information about the baseline levels of biomarkers in the sample prior to treatment, and the test sample can provide information about the levels of biomarkers after treatment. Alternatively, the reference sample can be obtained, for example, from a different subject, such as a subject who has not been treated according to the provided method. In this way, the reference sample can provide information about the baseline levels of biomarkers without treatment, and the test sample can provide information about the levels of biomarkers with treatment. The reference sample can also be obtained, for example, from a group of subjects, such as subjects who have not been treated according to the provided method. In this way, the reference sample can provide population-average information about the baseline levels of biomarkers without treatment, and the test sample can provide information about the levels of biomarkers with treatment. The reference sample can also be obtained from an individual or a group of individuals after treatment according to the provided method and can be used, for example, as a positive control sample. In some embodiments, the reference sample is obtained from normal tissue. In some embodiments, the reference sample is obtained from abnormal tissue. An increase or decrease in a biomarker relative to a normal control or reference sample can indicate the presence of a disease, or a response to disease treatment. In some embodiments, when the biomarker level in a test sample is at least 1.1-fold higher, such as at least 1.2-fold, at least 1.3-fold, at least 1.4-fold, at least 1.5-fold, at least 1.6-fold, at least 1.7-fold, at least 1.8-fold, at least 1.9-fold, at least 2-fold, at least 3-fold, at least 4-fold, at least 5-fold, at least 6-fold, at least 7-fold, at least 8-fold, at least 9-fold, at least 10-fold, at least 11-fold, at least 12-fold, at least 13-fold, at least 14-fold, at least 15-fold, at least 16-fold, at least 17-fold, at least 18-fold, at least 19-fold, or at least 20-fold higher than that of a negative control, an increase in the biomarker level in the test sample is determined, and thus the presence of a disease (e.g., an infectious disease or cancer), an increased risk of a disease, or a response to treatment is determined. In other embodiments, when the biomarker level in a test sample is at least 1.1-fold lower, such as at least 1.2-fold, at least 1.3-fold, at least 1.4-fold, at least 1.5-fold, at least 1.6-fold, at least 1.7-fold, at least 1.8-fold, at least 1.9-fold, at least 2-fold, at least 3-fold, at least 4-fold, at least 5-fold, at least 6-fold, at least 7-fold, at least 8-fold, at least 9-fold, at least 10-fold, at least 11-fold, at least 12-fold, at least 13-fold, at least 14-fold, at least 15-fold, at least 16-fold, at least 17-fold, at least 18-fold, at least 19-fold, or at least 20-fold lower than that of a negative control, a decrease in the biomarker level in the test sample is determined, and thus the presence of a disease, an increased risk of a disease, or a response to treatment is determined. The biomarker level can be detected using any method known in the art, including using biomarker-specific antibodies. Exemplary methods include, but are not limited to, polymerase chain reaction (PCR), Western blotting, dot blotting, ELISA, radioimmunoassay (RIA), immunoprecipitation, immunofluorescence, FACS analysis, electrochemiluminescence, and multiplex bead assays (e.g., using Luminex or fluorescent beads). In some cases, nucleic acid sequencing is employed. In certain embodiments, in an immunoassay or a PCR reaction (e.g., quantitative PCR), a decrease or increase in the level of one or more biomarkers is indicated by a detectable signal (e.g., a blot, fluorescence, chemiluminescence, color, or radioactivity). The detectable signal can be compared to a signal from a reference sample or a threshold.

[0003] In some embodiments, the results of the biomarker level determination are recorded on a tangible medium. For example, the results of a diagnostic assay, such as observing the presence or decrease or increase of one or more biomarkers, and diagnosing whether there is an increased risk or presence of a disease (such as an infectious disease or cancer), or whether a subject responds to a treatment, can be recorded on, for example, paper or an electronic medium, such as an audio tape, computer disk, CD-ROM, or flash drive. In some embodiments, the provided methods further include the step of providing the subject with the diagnostic and / or treatment results. VIII. Methods for Inducing an Immune Response In another aspect, the present disclosure provides various methods for inducing an immune response in a subject. The methods generally include administering to the subject any of the retroviral vector systems, retroviral packaging cells, retroviruses, or virus-like particles disclosed herein (such as in Sections III, IV, V, and VI). For example, an immunogenic composition can be formed that includes any of the provided retroviral vector systems, retroviral packaging cells, retroviruses, or virus-like particles. The immunogenic composition can be a vaccine, and the administration of the immunogenic composition can include vaccinating the subject with the vaccine. The disclosed immunogenic compositions can be administered using the provided methods, either as a single dose or multiple doses, for example, administering two doses at intervals of about 1 week, 2 weeks, 3 weeks, 1 month, about 2 months, about 3 months, about 6 months, or about 12 months. Other suitable dosing regimens can be determined by a medical practitioner. In some embodiments, additional compounds or drugs can be co-administered to the subject. Such compounds or drugs can be co-administered, for example, to alleviate the signs or symptoms of the disease being treated, or to reduce the side effects caused by the induction of the immune response. IX. Pharmaceutical Compositions In another aspect, pharmaceutical compositions are provided. The provided pharmaceutical compositions include one or more, such as two or more, of any of the retroviral vector systems, retroviral packaging cells, retroviruses, or virus-like particles disclosed herein (such as in Sections III, IV, V, and VI). The provided pharmaceutical compositions can, for example, better allow the retroviruses or virus-like particles disclosed herein to deliver the gene payload in situ to a subject in need. In some embodiments, the pharmaceutical composition comprises a therapeutically effective amount of a pharmaceutically acceptable excipient. In some embodiments, the pharmaceutical composition comprises one or more of a diluent, an adjuvant, or a carrier suitable for administration (e.g., administration to a mammal). Suitable diluents, adjuvants, or carriers can include, for example, lipids, such as liposomes, such as liposome dendrimers; liquids, such as water and oils, including those of petroleum, animal, vegetable, or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil, etc.; gum arabic; gelatin; starch paste; talc; keratin; colloidal silica; urea; and the like. Other examples of suitable diluents include distilled water, buffered water, normal saline, PBS, Ringer’s solution, glucose solution, and Hank’s solution. The pharmaceutical composition can also include other substances approximating physiological conditions, such as pH regulators and buffers, toxicity regulators, wetting agents, and detergents. In addition, adjuvants, thickeners, lubricants, and coloring agents can be selected or additionally used. The pharmaceutical composition can be formulated into preparations in solid, semi-solid, liquid, or gaseous forms, such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants, gels, microspheres, and aerosols. The provided pharmaceutical composition can also include any of a variety of stabilizers, such as antioxidants. When the pharmaceutical composition comprises a polypeptide, the polypeptide can be complexed with various well-known compounds that enhance the in vivo stability of the polypeptide or otherwise enhance its pharmacological properties (e.g., increase the half-life of the polypeptide, reduce its toxicity, and / or enhance solubility or uptake). Examples of such modifiers or complexing agents include sulfates, gluconates, citrates, and phosphates. The nucleic acid or polypeptide of the composition can also be complexed with molecules that enhance its in vivo properties. Such molecules include, for example, carbohydrates, polyamines, amino acids, other peptides, ions (e.g., sodium, potassium, calcium, magnesium, manganese), and lipids. X. Exemplary Embodiments Consider the following embodiments. Consider all combinations of features and embodiments. Embodiment 1: A retroviral vector system comprising: an envelope plasmid encoding a viral membrane fusion protein of a retrovirus; a packaging plasmid encoding the Gag-Pol protein of the retrovirus; and a transfer plasmid comprising one or more genes of interest to be transferred from the retrovirus to a target cell; wherein one or both of the envelope plasmid and the packaging plasmid further encode a binding moiety that directly or indirectly binds to a surface feature of the target cell. Embodiment 2: The embodiment according to Embodiment 1, wherein the viral membrane fusion protein is an engineered variant of a wild-type viral membrane fusion protein. Embodiment 3: The embodiment according to Embodiment 2, wherein the engineered variant does not bind to a cognate binding partner of the wild-type viral membrane fusion protein. Embodiment 4: The embodiment according to Embodiment 2 or 3, wherein the engineered variant is a truncated mutant of the wild-type viral membrane fusion protein. Embodiment 5: The embodiment according to any one of Embodiments 1 to 4, wherein the binding moiety comprises an extracellular domain and a transmembrane domain. Embodiment 6: The embodiment according to any one of Embodiments 1 to 5, wherein the envelope plasmid encodes the binding moiety. Embodiment 7: The embodiment according to any one of Embodiments 1 to 5, wherein the packaging plasmid encodes the binding moiety.

[0004] Embodiment 8: The embodiment according to any one of Embodiments 1 to 7, wherein the binding moiety binds to a ligand, the ligand comprises an antibody, an antibody mimetic, a single-chain variable fragment (scFv) or a derivative or fragment thereof, and wherein the ligand binds to a surface feature of the target cell. Embodiment 9: The embodiment according to Embodiment 8, wherein the binding moiety comprises a fluorescein isothiocyanate (FITC) binding domain, and wherein the ligand is FITC-conjugated. Embodiment 10: The embodiment according to Embodiment 9, wherein the binding moiety comprises an anti-fluorescein scFv or a fluorescein-binding anticalin. Embodiment 11: The embodiment according to Embodiment 9 or 10, wherein the ligand is a FITC-conjugated antibody. Embodiment 12: The embodiment according to Embodiment 8, wherein the binding moiety comprises a biotin-binding domain, and wherein the ligand is biotinylated. Embodiment 13: The embodiment according to Embodiment 12, wherein the binding moiety comprises an anti-biotin scFv, a polyclonal anti-biotin antibody, a monoclonal anti-biotin antibody, a biotin-binding anticalin or an avidin family protein. Embodiment 14: The embodiment according to Embodiment 12 or 13, wherein the ligand is a biotinylated antibody. Embodiment 15: The embodiment according to any one of Embodiments 8 to 14, wherein the surface feature of the target cell comprises CD3, CD4, CD7, CD8, CD19, CD20, CD56, CD71 or CTLA4. Embodiment 16: The embodiment according to any one of Embodiments 1 to 7, wherein the binding moiety directly binds to a surface feature of the target cell. Embodiment 17: The embodiment according to Embodiment 16, wherein the binding moiety comprises an scFv or a nanobody. Embodiment 18: The embodiment according to Embodiment 16 or 17, wherein the surface feature of the target cell comprises CD19 or CD7. Embodiment 19: An embodiment as described in any one of Embodiments 1 to 18, wherein the target cell is a T cell, B cell, natural killer (NK) cell, astrocyte, dendritic cell (DC), or monocyte. Embodiment 20: An embodiment as described in any one of Embodiments 1 to 19, wherein the retrovirus is an alpha-retrovirus, gamma-retrovirus, or lentivirus. Embodiment 21: An embodiment as described in any one of Embodiments 1 to 20, wherein the viral membrane fusion protein is vesicular stomatitis virus G (VSV-G) protein, from feline endogenous virus RD114, or from baboon endogenous virus BaEV. Embodiment 22: An embodiment as described in any one of Embodiments 1 to 21, wherein the retrovirus is an integrase-deficient retrovirus. Embodiment 23: An embodiment as described in any one of Embodiments 1 to 22, wherein one or more genes of interest encode a chimeric antigen receptor (CAR), switch receptor, or a derivative or fragment thereof. Embodiment 24: An embodiment as described in any one of Embodiments 1 to 23, wherein one or more genes of interest encode a CRISPR-associated (Cas) protein, zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), meganuclease, RNA-binding protein (RBP), recombinase, flippase, base editor, prime editor, nuclease-impaired Cas, nuclease-inactivated Cas, epigenome editor, transcriptional modifier (CRISPRa / i), transposase, Argonaute (Ago) protein, adenosine deaminase acting on RNA (ADAR), Pumilio RNA-binding family (PUF) protein, homing endonuclease, or a derivative or fragment thereof. Embodiment 25: An embodiment as described in any one of Embodiments 1 to 24, wherein one or more genes of interest encode a fluorescent protein, antibiotic resistance gene, or a derivative or fragment thereof. Embodiment 26: A retroviral packaging virus comprising a retroviral vector system as described in any one of Embodiments 1 to 25. Embodiment 27: A retrovirus comprising: a viral membrane fusion protein; a viral genome comprising one or more genes of interest for transfer from the retrovirus to a target cell; and a binding moiety that binds a ligand, the ligand including an antibody, antibody mimetic, single-chain variable fragment (scFv), or a derivative or fragment thereof, wherein the ligand binds to a surface feature of the target cell. Embodiment 28: An embodiment as described in Embodiment 27, wherein the viral membrane fusion protein is an engineered variant of a wild-type viral membrane fusion protein. Embodiment 29: The embodiment according to embodiment 28, wherein the engineered variant does not bind to the cognate binding partner of the wild-type viral membrane fusion protein. Embodiment 30: The embodiment according to embodiment 28 or 29, wherein the engineered variant is a truncated mutant of the wild-type viral membrane fusion protein. Embodiment 31: The embodiment according to any one of embodiments 27 to 30, wherein the binding moiety comprises an extracellular domain and a transmembrane domain. Embodiment 32: The embodiment according to embodiment 29 or 30, wherein the engineered variant of the wild-type viral membrane fusion protein comprises a binding moiety. Embodiment 33: The embodiment according to any one of embodiments 27 to 32, wherein the binding moiety comprises a fluorescein isothiocyanate (FITC) binding domain, and wherein the ligand is FITC-conjugated. Embodiment 34: The embodiment according to embodiment 33, wherein the binding moiety comprises an anti-fluorescein scFv or a fluorescein-binding anticalin. Embodiment 35: The embodiment according to embodiment 33 or 34, wherein the ligand is a FITC-conjugated antibody. Embodiment 36: The embodiment according to any one of embodiments 27 to 32, wherein the binding moiety comprises a biotin-binding domain, and wherein the ligand is biotinylated. Embodiment 37: The embodiment according to embodiment 36, wherein the binding moiety comprises an anti-biotin scFv, a biotin-binding anticalin or an avidin family protein. Embodiment 38: The embodiment according to embodiment 36 or 37, wherein the ligand is a biotinylated antibody. Embodiment 39: The embodiment according to any one of embodiments 27 to 38, wherein the surface features of the target cells include CD3, CD4, CD7, CD8, CD19, CD20, CD56, CD71 or CTLA4. Embodiment 40: The embodiment according to any one of embodiments 27 to 39, wherein the retrovirus is an alpha-retrovirus, a gamma-retrovirus or a lentivirus. Embodiment 41: The embodiment according to any one of embodiments 27 to 40, wherein the viral membrane fusion protein is the vesicular stomatitis virus G (VSV-G) protein, from feline endogenous virus RD114, or from baboon endogenous virus BaEV. Embodiment 42: The embodiment according to any one of embodiments 27 to 41, wherein the retrovirus is an integrase-deficient retrovirus. Embodiment 43: An embodiment according to any one of Embodiments 27 to 42, wherein one or more target genes encode a chimeric antigen receptor (CAR), a switch receptor, or a derivative or fragment thereof. Embodiment 44: An embodiment according to any one of Embodiments 27 to 43, wherein one or more target genes encode a CRISPR-associated (Cas) protein, a zinc finger nuclease (ZFN), a transcription activator-like effector nuclease (TALEN), a meganuclease, an RNA-binding protein (RBP), a recombinase, a flippase, a base editor, a prime editor, nuclease-impaired Cas, nuclease-inactivated Cas, an epigenome editor, a transcriptional modifier (CRISPRa / i), a transposase, an Argonaute (Ago) protein, an adenosine deaminase acting on RNA (ADAR), a Pumilio RNA-binding family (PUF) protein, a homing endonuclease, or a derivative or fragment thereof. Embodiment 45: A virus-like particle comprising a binding moiety that binds a ligand, the ligand comprising an antibody, an antibody mimetic, a single-chain variable fragment (scFv), or a ligand that is a derivative or fragment thereof, wherein the ligand binds to a surface feature of a target cell. Embodiment 46: An embodiment according to Embodiment 45, wherein the binding moiety comprises a fluorescein isothiocyanate (FITC) binding domain, and wherein the ligand is FITC-conjugated. Embodiment 47: An embodiment according to Embodiment 46, wherein the binding moiety comprises an anti-fluorescein scFv or a fluorescein-binding anticalin. Embodiment 48: An embodiment according to Embodiment 46 or 47, wherein the ligand is a FITC-conjugated antibody. Embodiment 49: An embodiment according to Embodiment 45, wherein the binding moiety comprises a biotin-binding domain, and wherein the ligand is biotinylated. Embodiment 50: An embodiment according to Embodiment 49, wherein the binding moiety comprises an anti-biotin scFv, a biotin-binding anticalin, or an avidin family protein. Embodiment 51: An embodiment according to Embodiment 49 or 50, wherein the ligand is a biotinylated antibody. Embodiment 52: An embodiment according to any one of Embodiments 45 to 51, wherein the surface feature of the target cell comprises CD3, CD4, CD7, CD8, CD19, CD20, CD56, CD71, or CTLA4. Embodiment 53: An embodiment according to any one of embodiments 45 to 52, comprising a CRISPR-associated (Cas) protein, zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), meganuclease, RNA-binding protein (RBP), recombinase, flippase, base editor, prime editor, Cas with impaired nuclease function, nuclease-inactivated Cas, epigenome editor, transcriptional modifier (CRISPRa / i), transposase, Argonaute (Ago) protein, adenosine deaminase acting on RNA (ADAR), Pumilio RNA-binding family (PUF) protein, homing endonuclease, or a derivative or fragment thereof. Embodiment 54: A method for generating a retroviral vector system according to any one of embodiments 1 to 25, the method comprising transfecting a host cell with the retroviral vector system according to any one of embodiments 1 to 25. Embodiment 55: A method for preventing or treating a disease in a subject, the method comprising administering to the subject the retroviral vector system of any one of embodiments 1 to 25, the retroviral packaging cell of embodiment 26, the retrovirus of any one of embodiments 27 to 44, or the virus-like particle of any one of embodiments 45 to 53. Embodiment 56: An embodiment according to embodiment 55, wherein the disease comprises a genetic disease. Embodiment 57: An embodiment according to embodiment 56, wherein the disease comprises cancer. Embodiment 58: An embodiment according to embodiment 57, wherein the cancer comprises a solid tumor. Embodiment 59: An embodiment according to embodiment 55, wherein the disease comprises an infection. Embodiment 60: An embodiment according to embodiment 59, wherein the infection is associated with a biomedical device implant in the subject. Embodiment 61: A method for repairing or regenerating damaged or aged tissue in a subject, the method comprising administering to the subject the retroviral vector system of any one of embodiments 1 to 25, the retroviral packaging cell of embodiment 26, the retrovirus of any one of embodiments 27 to 44, or the virus-like particle of any one of embodiments 45 to 53, wherein the target cells comprise induced pluripotent stem cells, embryonic stem cells, adult stem cells, mesenchymal stem cells or progenitor cells. Embodiment 62: An embodiment according to embodiment 61, wherein the damaged or aged tissue comprises muscle cells, nerve cells or pancreatic cells. Example The present disclosure will be better understood in view of the following non-limiting examples.The following examples are intended for illustrative purposes only and are not intended to limit the scope of the present invention in any way. Example 1. Transduction of lymphocytes by retroviruses with cell-binding domains According to the provided embodiments, retroviruses with CD7-targeted nanobodies as cell binding domains were generated. Wild-type Jurkat cells ( Figure 3 , top row). Cells transduced with conventional lentivirus showed GFP activity ( Figure 3 , second row). The VSV-G of the lentivirus was then mutated to eliminate its natural binding ability. The mutated lentivirus could not effectively transduce Jurkat cells ( Figure 3 , third row). Feline endogenous virus pseudotyped retrovirus (RD114) also failed to transduce cells ( Figure 3 , fourth row). However, the provided retrovirus with the CD7 cell-binding domain produced transduction results similar to those observed with conventional lentiviruses ( Figure 3 , bottom row). These results demonstrate efficient transduction using the retroviral materials and methods disclosed herein. Example 2. Transduction of NK cells by retroviruses with cell-binding domains Natural killer (NK) cells from two donors were engineered ex vivo with a chimeric receptor protein based on Toll-like receptor 5 using two different retroviruses. The first retrovirus, a conventional lentivirus with VSV-G envelope protein, showed less than 10% transduction efficiency in each of the two NK cell donor populations ( Figure 4 The second retrovirus, a retrovirus having a CD7 binding cell binding domain according to the provided embodiment, exhibited a transduction efficiency 2- to 8-fold higher than that observed with conventional lentiviruses ( Figure 4 ). These results demonstrate the ability of the retroviral materials and methods disclosed herein to effectively transduce therapeutically important cell types that are not easily transduced using previous retroviral methods. Example 3. Transduction by retroviruses with antibody-binding domains Universal pseudotyped retroviruses according to the provided embodiments are generated by exchanging the binding moiety with a monomeric streptavidin (mSA) biotin binding domain or a FITC binding antibody domain (αFITC). The retroviruses each carry an mCherry expression cassette. Jurkat cells are then exposed to different concentrations of retroviruses, where the retroviruses are bound to different concentrations of CD71 antibody (αCD71). The results show that FITC binding to retrovirus ( Figure 6 ) and biotin-conjugated retrovirus ( Figure 7)Transduce Jurkat cells when bound to an antibody. Additionally, the provided retroviruses can transduce Jurkat cells multiple times, which is characteristic of lentiviruses. Additional experiments demonstrated that optimizing the amount of virus and the concentration of antibody increased the expression of the delivered gene payload, likely through multiple integration events( Figure 8 and Figure 9 ). Example 4. Targeting different cell markers and epitopes with a universal pseudotyped retrovirus A universal pseudotyped retrovirus was generated according to the provided embodiments, where the retrovirus includes a FITC-binding scFv and an mCherry expression cassette. The retrovirus was used to transduce Jurkat cells engineered with antibodies against lymphocyte marker (CD7) and T cell marker (CD3)( Figure 10 ), Raji cells engineered with antibodies against B cell markers (CD19 and CD20)( Figure 11 ), and primary human T cells engineered with antibodies against subtype markers (CD4 and CD8)( Figure 12 ). Each antibody was tested at 3 concentrations, and multiple antibody clones were tested for each marker( Figures 10 to 12 ). The results showed that the universal pseudotyped retrovirus was effective against multiple targets and multiple epitopes on those targets. Example 5. Selective targeting of cells with a universal pseudotyped retrovirus A universal pseudotyped retrovirus was generated according to the provided embodiments, where the retrovirus includes a FITC-binding scFv and an mCherry expression cassette. A portion of the retrovirus was conjugated to a CD4( Figure 13 ) or CD8( Figure 14 ) antibody and delivered to primary human T cells containing T cells with only CD4 and T cells with only CD8. In each of the three donor populations tested, the retrovirus only effectively transduced its intended target, with little off-target cell engineering observed( Figure 13 and Figure 14 ). These results indicate that the universal pseudotyped retroviruses disclosed herein can selectively engineer specified cell populations in a mixture. Example 6. Delivery of a protein with in vivo activity to a mouse model Targeted pseudotyped lentiviruses according to the provided embodiments are generated using standard methods. Briefly, a transfer plasmid containing a gene of interest payload, a packaging plasmid, and a modified envelope plasmid as described in Part III are transfected into HEK293T cells. The modified envelope plasmid is mutated to eliminate the binding properties of VSV-G and engineered to encode a binding moiety. The binding moiety can be configured or selected to directly bind to a cell marker or can be configured or selected to bind to a moiety contained on a second binder such as a biotin-conjugated antibody or a FITC-conjugated antibody. The virus is isolated and purified. If a second binder, i.e., a ligand, is used, the purified virus and the second binder are incubated together for a suitable period of time prior to administration. In a particular example, the gene of interest payload is GFP and the binding moiety is a CD7 nanobody (nbCD7) or monomeric streptavidin (mSA). In the case of mSA, the virus is incubated with a biotin-conjugated CD7 antibody for 30 minutes. In both cases, the virus is injected intravenously into mice. Approximately one week later, the spleens and peripheral blood of the mice are taken and processed to isolate immune cells (splenocytes or peripheral blood mononuclear cells, respectively). The cells are stained for CD7 and the extent of GFP in the CD7+ fraction is quantified to confirm the targeting efficiency, while the GFP in the CD7- fraction is quantified to show off-target effects. Although the foregoing disclosure has been described in detail for purposes of clarity of understanding by way of illustration and example, those skilled in the art will understand that certain changes and modifications may be practiced within the spirit and scope of the present disclosure, such as within the scope of the appended claims. It should also be understood that aspects of the present disclosure and parts of the various recited embodiments and features may be combined or interchanged in whole or in part. In the foregoing description of the various embodiments, as will be understood by those skilled in the art, those embodiments that refer to another embodiment may be appropriately combined with other embodiments. Additionally, those of ordinary skill in the art will understand that the foregoing description is merely exemplary and is not intended to limit the present disclosure. Further, each reference provided herein is incorporated herein by reference in its entirety for all purposes to the extent as if each reference were individually incorporated herein by reference.

Claims

1. A retroviral vector system, comprising: An envelope plasmid encoding a viral membrane fusion protein of a retrovirus; A packaging plasmid encoding the Gag-Pol protein of the retrovirus; and A transfer plasmid containing one or more genes of interest transferred from the retrovirus to a target cell; Wherein one or both of the envelope plasmid and the packaging plasmid further encode a binding moiety that directly or indirectly binds to a surface feature of the target cell.

2. The retroviral vector system according to claim 1, wherein the viral membrane fusion protein is an engineered variant of a wild-type viral membrane fusion protein.

3. The retroviral vector system according to claim 2, wherein the engineered variant does not bind to a cognate binding partner of the wild-type viral membrane fusion protein.

4. The retroviral vector system according to claim 2 or 3, wherein the engineered variant is a truncated mutant of the wild-type viral membrane fusion protein.

5. The retroviral vector system according to any one of claims 1 to 4, wherein the binding moiety comprises an extracellular domain and a transmembrane domain.

6. The retroviral vector system according to any one of claims 1 to 5, wherein the envelope plasmid encodes the binding moiety.

7. The retroviral vector system according to any one of claims 1 to 5, wherein the packaging plasmid encodes the binding moiety.

8. The retroviral vector system according to any one of claims 1 to 7, wherein the binding moiety binds to a ligand, the ligand comprising an antibody, an antibody mimetic, a single-chain variable fragment (scFv), or a derivative or fragment thereof, and wherein the ligand binds to a surface feature of the target cell.

9. The retroviral vector system according to claim 8, wherein the binding moiety comprises a fluorescein isothiocyanate (FITC) binding domain, and wherein the ligand is FITC-conjugated.

10. The retroviral vector system according to claim 9, wherein the binding moiety comprises an anti-fluorescein scFv or a fluorescein-binding anticalin.

11. The retroviral vector system according to claim 9 or 10, wherein the ligand is a FITC-conjugated antibody.

12. The retroviral vector system according to claim 8, wherein the binding moiety comprises a biotin-binding domain, and wherein the ligand is biotinylated.

13. The retroviral vector system according to claim 12, wherein the binding moiety comprises an anti-biotin scFv, a polyclonal anti-biotin antibody, a monoclonal anti-biotin antibody, a biotin-binding anticalin, or an avidin family protein.

14. The retroviral vector system according to claim 12 or 13, wherein the ligand is a biotinylated antibody.

15. The retroviral vector system according to any one of claims 8 to 14, wherein the surface feature of the target cell comprises CD3, CD4, CD7, CD8, CD19, CD20, CD56, CD71, or CTLA4.

16. The retroviral vector system according to any one of claims 1 to 7, wherein the binding moiety directly binds to a surface feature of the target cell.

17. The retroviral vector system according to claim 16, wherein the binding moiety comprises a scFv or a nanobody.

18. The retroviral vector system according to claim 16 or 17, wherein the surface feature of the target cell comprises CD19 or CD7.

19. The retroviral vector system according to any one of claims 1 to 18, wherein the target cell is a T cell, a B cell, a natural killer (NK) cell, an astrocyte, a dendritic cell (DC), or a monocyte.

20. The retroviral vector system according to any one of claims 1 to 19, wherein the retrovirus is an alpha retrovirus, a gamma retrovirus, or a lentivirus.

21. The retroviral vector system according to any one of claims 1 to 20, wherein the viral membrane fusion protein is vesicular stomatitis virus G (VSV-G) protein, from feline endogenous virus RD114, or from baboon endogenous virus BaEV.

22. The retroviral vector system according to any one of claims 1 to 21, wherein the retrovirus is an integrase-deficient retrovirus.

23. The retroviral vector system according to any one of claims 1 to 22, wherein the one or more genes of interest encode a chimeric antigen receptor (CAR), a switch receptor, or a derivative or fragment thereof.

24. The retroviral vector system according to any one of claims 1 to 23, wherein the one or more genes of interest encode a CRISPR-associated (Cas) protein, a zinc finger nuclease (ZFN), a transcription activator-like effector nuclease (TALEN), a meganuclease, an RNA-binding protein (RBP), a recombinase, a flippase, a base editor, a prime editor, a nuclease-impaired Cas, a nuclease-inactivated Cas, an epigenome editor, a transcriptional modifier (CRISPRa / i), a transposase, an Argonaute (Ago) protein, an adenosine deaminase acting on RNA (ADAR), a Pumilio RNA-binding family (PUF) protein, a homing endonuclease, or a derivative or fragment thereof.

25. The retroviral vector system according to any one of claims 1 to 24, wherein the one or more genes of interest encode a fluorescent protein, an antibiotic resistance gene, or a derivative or fragment thereof.

26. A retroviral packaging virus comprising the retroviral vector system according to any one of claims 1 to 25.

27. A retrovirus comprising: a viral membrane fusion protein; a viral genome comprising one or more genes of interest transferred from the retrovirus to a target cell; and a binding moiety that binds a ligand, the ligand comprising an antibody, an antibody mimetic, a single-chain variable fragment (scFv), or a derivative or fragment thereof, wherein the ligand binds to a surface feature of the target cell.

28. The retrovirus according to claim 27, wherein the viral membrane fusion protein is an engineered variant of a wild-type viral membrane fusion protein.

29. The retrovirus according to claim 28, wherein the engineered variant does not bind to the cognate binding partner of the wild-type viral membrane fusion protein.

30. The retrovirus according to claim 28 or 29, wherein the engineered variant is a truncated mutant of the wild-type viral membrane fusion protein.

31. The retrovirus according to any one of claims 27 to 30, wherein the binding moiety comprises an extracellular domain and a transmembrane domain.

32. The retrovirus according to claim 29 or 30, wherein the engineered variant of the wild-type viral membrane fusion protein comprises a binding moiety.

33. The retrovirus according to any one of claims 27 to 32, wherein the binding moiety comprises a fluorescein isothiocyanate (FITC) binding domain, and wherein the ligand is FITC-conjugated.

34. The retrovirus according to claim 33, wherein the binding moiety comprises an anti-fluorescein scFv or a fluorescein-binding anticalin.

35. The retrovirus according to claim 33 or 34, wherein the ligand is a FITC-conjugated antibody.

36. The retrovirus according to any one of claims 27 to 32, wherein the binding moiety comprises a biotin-binding domain, and wherein the ligand is biotinylated.

37. The retrovirus according to claim 36, wherein the binding moiety comprises an anti-biotin scFv, a biotin-binding anticalin, or an avidin family protein.

38. The retrovirus according to claim 36 or 37, wherein the ligand is a biotinylated antibody.

39. The retrovirus according to any one of claims 27 to 38, wherein the surface features of the target cell include CD3, CD4, CD7, CD8, CD19, CD20, CD56, CD71, or CTLA4.

40. The retrovirus according to any one of claims 27 to 39, wherein the retrovirus is an alpha-retrovirus, a gamma-retrovirus, or a lentivirus.

41. The retrovirus according to any one of claims 27 to 40, wherein the viral membrane fusion protein is the vesicular stomatitis virus G (VSV-G) protein, from feline endogenous virus RD114, or from baboon endogenous virus BaEV.

42. The retrovirus according to any one of claims 27 to 41, wherein the retrovirus is an integrase-deficient retrovirus.

43. The retrovirus according to any one of claims 27 to 42, wherein the one or more genes of interest encode a chimeric antigen receptor (CAR), a switch receptor, or a derivative or fragment thereof.

44. A retrovirus according to any one of claims 27 to 43, wherein the one or more genes of interest encode a CRISPR-associated (Cas) protein, zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), meganuclease, RNA-binding protein (RBP), recombinase, flippase, base editor, prime editor, nuclease-impaired Cas, nuclease-inactivated Cas, epigenome editor, transcriptional modifier (CRISPRa / i), transposase, Argonaute (Ago) protein, adenosine deaminase acting on RNA (ADAR), Pumilio RNA-binding family (PUF) protein, homing endonuclease, or a derivative or fragment thereof.

45. A virus-like particle comprising a binding moiety that binds a ligand, the ligand comprising an antibody, antibody mimetic, single-chain variable fragment (scFv), or a derivative or fragment thereof, wherein the ligand binds to a surface feature of a target cell.

46. The virus-like particle according to claim 45, wherein the binding moiety comprises a fluorescein isothiocyanate (FITC) binding domain, and wherein the ligand is FITC-conjugated.

47. The virus-like particle according to claim 46, wherein the binding moiety comprises an anti-fluorescein scFv or a fluorescein-binding anticalin.

48. The virus-like particle according to claim 46 or 47, wherein the ligand is a FITC-conjugated antibody.

49. The virus-like particle according to claim 45, wherein the binding moiety comprises a biotin-binding domain, and wherein the ligand is biotinylated.

50. The virus-like particle according to claim 49, wherein the binding moiety comprises an anti-biotin scFv, a biotin-binding anticalin, or an avidin family protein.

51. The virus-like particle according to claim 49 or 50, wherein the ligand is a biotinylated antibody.

52. The virus-like particle according to any one of claims 45 to 51, wherein the surface feature of the target cell comprises CD3, CD4, CD7, CD8, CD19, CD20, CD56, CD71, or CTLA4.

53. The virus-like particle according to any one of claims 45 to 52, which comprises a CRISPR-associated (Cas) protein, zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), meganuclease, RNA-binding protein (RBP), recombinase, flippase, base editor, prime editor, nuclease-impaired Cas, nuclease-inactivated Cas, epigenome editor, transcriptional modifier (CRISPRa / i), transposase, Argonaute (Ago) protein, adenosine deaminase acting on RNA (ADAR), Pumilio RNA-binding family (PUF) protein, homing endonuclease, or a derivative or fragment thereof.

54. A method for generating a retroviral vector system as described in any one of claims 1 to 25, the method comprising transfecting a host cell with the retroviral vector system as described in any one of claims 1 to 25.

55. A method for preventing or treating a disease in a subject, the method comprising administering to the subject the retroviral vector system as described in any one of claims 1 to 25, the retroviral packaging cell as described in claim 26, the retrovirus as described in any one of claims 27 to 44, or the virus-like particle as described in any one of claims 45 to 53.

56. The method as described in claim 55, wherein the disease comprises a genetic disease.

57. The method as described in claim 55, wherein the disease comprises cancer.

58. The method as described in claim 57, wherein the cancer comprises a solid tumor.

59. The method as described in claim 55, wherein the disease comprises an infection.

60. The method as described in claim 59, wherein the infection is associated with a biomedical device implant of the subject.

61. A method for repairing or regenerating damaged or aged tissue in a subject, the method comprising administering to the subject the retroviral vector system as described in any one of claims 1 to 25, the retroviral packaging cell as described in claim 26, the retrovirus as described in any one of claims 27 to 44, or the virus-like particle as described in any one of claims 45 to 53, wherein the target cells comprise induced pluripotent stem cells, embryonic stem cells, adult stem cells, mesenchymal stem cells or progenitor cells.

62. The method as described in claim 61, wherein the damaged or aged tissue comprises muscle cells, nerve cells or pancreatic cells.

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