Antibodies binding to vista at acidic ph

Abstract

The present application relates to antibodies specifically binding to the V-domain immunoglobulin-containing suppressor of T-cell activation (VISTA) at acidic pH and their use in cancer treatment. In some embodiments, the antibodies bind specifically to human VISTA at acidic pH, but do not significantly bind to human VISTA at neutral or physiological pH.

Description

[0001] ANTIBODIES BINDING TO VISTA AT ACIDIC pH

[0002] FIELD

[0003] The present application relates to antibodies specifically binding to the V-domain immunoglobulin-containing suppressor of T-cell activation (VISTA) at acidic pH and their use in cancer treatment.

[0004] BACKGROUND AND SUMMARY OF THE DISCLOSURE

[0005] The V-domain Ig-containing suppressor of T-cell activation, or VISTA, is a co- inhibitory member of the B7 family of immunoreceptors expressed by myelomonocytic cells and other leukocytes. However, the mechanism by which VISTA suppresses immune responses is poorly understood.

[0006] The inventors have found that unlike other known immunoreceptors, VISTA engages its counter-receptors and functions selectively at acidic pH, with little activity at

[0007] physiological pH (e.g., 7.3 - 7.4). VISTA may thus suppress immune responses in acidic microenvironments, such as tumor beds or sites of inflammation, without perturbing cells circulating in blood or residing in non-inflamed, non-acidic tissues. Additionally, the inventors have found that anti-VISTA antibodies can be engineered to selectively bind to VISTA at acidic pH, with little or no binding at physiological pH, mirroring VISTA' s own acidic pH selectivity. These acidic pH selective antibodies may offer desirable properties for treating diseases, such as cancer, relative to antibodies that bind VISTA at physiological pH.

[0008] The present disclosure concerns antibodies that specifically bind to the extracellular domain (ECD) of VISTA, such as human VISTA ("hVISTA" or "hu VISTA") at acidic pH (e.g., in acidic conditions). The present disclosure also concerns antibodies that specifically bind to the extracellular domain (ECD) of VISTA, such as hVISTA, at acidic pH, with little or no binding at neutral or physiological pH. The inventors have noted herein that the hVISTA-ECD amino acid sequence includes a number of conserved as well as nonconserved histidine residues, and that the frequency of histidine residues in VISTA' s ECD is exceptionally high relative to other B7 family members and other Immunoglobulin

[0009] Superfamily members. (See Figs. 1 A and IB.) In solution, the amino acid histidine has a pKaof about 6.5, meaning that at or below pH 6.5, histidine residues within proteins are often protonated and thus, positively charged, while at pH higher than pH 6.5 they are increasingly unprotonated and neutral in charge. Tumor microenvironments and inflamed tissues are often acidic, and thus, VISTA proteins found in these microenvironments may be at least partially protonated at their histidine residues. The inventors, as discussed herein, have hypothesized that histidine protonation may affect the conformation, surface structure, and / or charge density of VISTA, which, in turn, may create pH-specific or pH-selective epitopes for both receptor-ligand interaction(s) and antibody binding. Targeting VISTA with antibodies that bind at acidic pH but not neutral or physiological pH may prevent target- mediated drug disposition via circulating and lymphoid organ-resident myelomonocytic cells, improving antibody PK, receptor occupancy, and activity in tumor microenvironments.

[0010] Acidic pH-selective antibodies may also improve the specificity of VISTA antibodies for intratumoral, rather than circulating, target cells in the cases of therapeutic modalities such as antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), complement-dependent cytotoxicity (CDC), and delivery of payloads (antibody-drug conjugates).

[0011] BRIEF DESCRIPTION OF THE FIGURES

[0012] A color version of several of the figures is provided in priority US provisional application No. 62 / 636,746, filed Febuary 28, 2018. Should that priority application file become available through publication of the present application, it is presumed that copies of the color drawings will be provided by the US Patent and Trademark Office upon request and payment of the necessary fee.

[0013] Figs. 1A-C show that VISTA' s extracellular domain contains an exceptionally high frequency of histidine residues, that many of these histidine residues are conserved, and that at least some of these histidine residues may participate in receptor-ligand binding. Fig. 1A shows a graph of immunoglobulin domain-containing proteins, with the number of extracellular domain amino acid residues for each protein plotted on the x-axis, and the frequency of histidine residues within the extracellular domain for each protein plotted on the y-axis. The size of each data point corresponds to the total number of histidine residues in each protein's extracellular domain. Fig. IB shows the aligned amino acid sequences of the extracellular domains of human, cynomolgus macaque, and mouse VISTA. Signal peptide (Sig) and transmembrane domain (TMD) sequence locations are marked. Histidine residues conserved across all three species are shown in bold and underlined; histidine residues conserved across human and cynolmogus macaque are shown in bold only. Fig. 1C shows a model of the human VISTA immunoglobulindomain's three-dimensional structure. Histidine residues are depicted as ball and stick traces.

[0014] Figs. 2A-B show a model in which the histidine residues in VISTA' s extracellular domain confer counter-receptor selectivity for acidic pH rather than physiological pH. Fig. 2A shows the equilibrium between the lack of, and the presence of, protonation of the pyrrole ammonium group ( H) in a histidine residue. The pKa of histidine in solution is 6.5, indicating that histidine residues are more likely to be protonated at pH 6.5 and lower, and thus, positively charged, than at higher pH. Fig. 2B shows shows a model in which VISTA engages P-selectin glycoprotein ligand 1 (PSGL-1) or other counter-receptors and ligands ("VISTA-R") selectively at acidic pH. Accordingly, antibody binding to VISTA' s extracellular domainat at acidic pH rather at physiological pH may be critical to inhibiting or modulating VISTA activity.

[0015] Fig. 3 shows the level of VISTA surface expression (mean fluorescence intensity (MFI) of anti-VISTA antibody staining) on tumor-infiltrating macrophages, dendritic cells, neutrophils, CD4+ effector T cells, CD4+ regulatory T cells, CD8+ T cells, natural killer (NK) cells, and B cells. VISTA is expressed on many tumor-infiltrating leukocytes, particularly myeloid cells. Tumor microenvironments are often acidic, enabling VISTA to engage counter-receptors and ligands.

[0016] Figs. 4A-E show that VISTA selectively binds to leukocytes and to PSGL-1 at acidic pH, with little or no binding at neutral pH, and that this binding can be blocked by an anti- VISTA antibody. Fig. 4A on the left shows representative histograms of fluorescently- conjugated recombinant VISTA multimer binding to activated human CD4+ T cells. From darker gray to lighter, the filled histograms depict binding at pH 7.0, 6.5, 6.4, 6.3, 6.1, and 6.0. Some histograms are labeled with their corresponding pH. Non- VISTA control multimer binding at pH 6.0 is shown as the unfilled histogram. On the right, the mean MFI of VISTA (circles) and control (triangles) multimer binding to activated human CD4+ T cells from two donors at different pH is graphed. Fig. 4B shows representative histograms of recombinant VISTA multimer binding to peripheral blood mononuclear cells (PBMC) at pH 6.0 and pH 7.4. From darker gray to lighter, the filled histograms depict binding at pH 6.0 to CD19+ B cells, CD4+ T cells, CD8+ T cells, CD56+ NK cells, and CD14+ monocytes. The unfilled, solid border and dotted border histograms depict binding at pH 7.4 to total PBMC lymphocytes and monocytes respectively. Fig. 4C shows representative recombinant VISTA multimer binding to activated human CD4+ T cells in the presence of an anti-VISTA blocking antibody (squares) or a non-VISTA-specific isotype-matched control antibody (circles). Antibody concentrations are plotted on log scale. Non-linear regressions are also shown. The triangle depicts the background signal from activated human CD4+ T cells that were not stained with recombinant VISTA multimers. Fig. 4D shows representative two- dimensional flow cytometry plots of recombinant VISTA multimer binding at pH 6.0 to heparan sulfate-deficient Chinese Hamster Ovary (CHO) cells (line pGSD-677, American Type Culture Collection) that were transfected to express human PSGL- 1. Multimer binding was performed in the presence and absence of the anti-VISTA blocking antibody shown in Fig. 4C. Cells left unstained by recombinant VISTA multimers are shown as a control.

[0017] PSGL-1 antibody staining is plotted on the y-axis, and VISTA multimer staining is plotted on the x-axis. Fig. 4E shows representative histograms of recombinant mouse VISTA-Fc fusion protein binding to mouse splenocytes at pH 6.0 and pH 7.4. From darker gray to lighter, the filled histograms depict binding at pH 6.0 to CD8+ T cells, CD1 lb+ myeloid cells, and CD4+ T cells. The unfilled histogram depicts binding at pH 7.4 to total splenocytes.

[0018] Figs. 5A-D show that VISTA mediates T cell suppression and cell : cell adhesion preferentially at acidic pH, and that both effects can be reversed with an anti-VISTA blocking antibody. Fig. 5A shows representative cell : cell conjugate formation at pH 6.0 and 7.0 between 293T cells expressing hVISTA or vector control (plotted on the y-axes) and CHO cells endogenously expressing cell surface heparan sulfate on the x-axes. Fig. 5B is a graph of the frequency of cell conjugates formed at pH 6.0 between the same cells in the presence of an anti-VISTA blocking antibody, an anti-VISTA non-blocking antibody, or isotype-matched non-VISTA-specific control antibodies. Fig. 5C shows representative plots of the luciferase activity generated by Jurkat (human T cell line) cells expressing an FkB luciferase reporter after co-culture at various pH with 293T cells expressing h VISTA and a single-chain variable fragment of the anti-human T cell receptor agonist antibody OKT3 ("artificial antigen-presenting cells"). An anti-VISTA blocking antibody (squares) or an isotype-matched non-VISTA-specific control antibody (circles) were added to the co- cultured cells. In Fig. 5D, the data shown in Fig. 5A are plotted as fold-increase of the luciferase signal with anti-VISTA antibody treatment relative to control ("effect size").

[0019] Figs. 6A-G show that VISTA can be found in intracellular endosomes, particularly Rabl 1+ recycling endosomes, and can recycle to and from the cell surface via endosomal trafficking. Fig. 6A shows co-localization of VISTA, Rab5 (early endosome marker), Rab7 (late endosome marker), and Rabl 1 (recycling endosome marker) within 293T cells expressing human VISTA. Fig. 6B shows co-localization of VISTA and Rabl 1 within human monocytes. Intracellular VISTA is co-localized with Rabl 1+ recycling endosomes. A non-VISTA-binding control antibody of the same isotype as the VISTA antibody ("cAb") does not detectably bind the monocytes. Fig. 6C shows the binding of three anti-VISTA antibodies to recombinant VISTA at pH 7.4 (black), 6.7 (darker gray), and 6. (lighter gray). Fig. 6D shows the susceptibility of a VISTA expressing acute myeloid leukemia (AML) cell line to killing by the same anti-VISTA antibodies 1 (inverted triangles), 2 (circles), 3 (squares), or a non-VISTA-specific control antibody (triangles) bearing cathepsin B-sensitive linkers and cytotoxic payloads. Cell viability (CellTiter-Glo LU) is plotted on the y-axis and antibody concentrations are plotted on the x-axis. Fig. 6E compares hVISTA binding of anti- VISTA antibody 3 to that of an engineered variant ("VISTA mAb 3c") that does not exhibit impaired binding at acidic pH. Fig. 6F shows an antibody drug-conjugate assay comparing the potency of anti-VISTA antibody 3 (squares) and 3c (diamonds). Fig. 6G shows a schematic of endosome trafficking, with VISTA recycling to and from and cell surface via early endosomes and recycling endosomes.

[0020] Figs. 7A-F show how anti-VISTA antibody variant libraries were designed and screened in order to obtain acidic pH-selective antibodies. Fig. 7A shows amino acid substitutions that were made in VH CDR 3 of the anti-human VISTA antibody clone Pl- 061029 (abbreviated Ό29) for creating an Ό29 library for screening. To potentially improve binding to VISTA' s histidine-rich region at acidic pH, the libraries allowed substitutions for the negatively charged amino acids aspartate and glutamate as well as pH-responsive histidine. X=H, D or E. Bracketed sequences were removed from synthesis to avoid introducing liabilities. A total of 647 unique sequences of Pl-061029 HCDR3 with 1-2 mutations were synthesized. Fig. 7B shows the procedure by which the '029 library is iteratively screened and selected for acidic pH-selective antibody variants. R denotes selection round. Fig. 7C shows representative two-dimensional flow cytometry plots data showing the variant pool after 9 rounds of selection. VISTA binding is plotted on the y-axis, and variant antibody expression is plotted on the x-axis. Binding data at various antibody concentrations and pH are shown. Fig. 7D shows a diagram of Pl-061029 and its progeny clones binding to human VISTA at pH 6.0 and 7.4. Fig. 7E shows a diagram of the off-rates of Pl-061029 and its progeny clones to human VISTA at pH 6.0. Fig. 7F shows SPR binding data of the antibodies Pl-068761, Pl-068767 and Pl-061029 to human VISTA at pH 6.0 and pH 7.4.

[0021] Figs. 8A-F show acidic pH-selective cell binding, blocking, and effector activity of the VISTA antibodies Pl-068761 and Pl-068767. Fig. 8A and Fig. 8B show the mean fluorescence intensity of the acidic pH-selective antibodies Pl-068761 (Fig. 8A) and Pl- 068767 (Fig. 8B) binding to Raji cells ectopically expressing human VISTA. The cells were stained at approximately pH 6.0 (circles; highest curve in Fig. 8A), 6.1 (squares; third highest curve), 6.2 (triangles; second highest curve), 6.4 (inverted triangles; fourth highest curve close to the pH 6.1 curve), 6.6 (diamonds; fourth curve from bottom), 7.0 (circles; third curve from bottom), 7.2 (squares; second curve from bottom), and 8.1 (unfilled triangles; bottom curve in Fig. 8A). Binding was detected with a fluorescently conjugated anti-human IgG secondary antibody. Fig. 8C shows Pl-068767 (circles) and an isotype-matched non- specific control antibody (triangles) binding to Raji cells ectopically expressing human VISTA at 3125 ng / mL at various pH. The "pHso", the pH at which 50% of Pl-068767 binding is lost, is approximately 6.6. Fig. 8D shows the mean fluorescence intensities (MFI) of an isotype-matched non-specific control antibody (filled and unfilled circles for pH 7.0 and 6.0 respectively), anti-VISTA mAb 2 ("control", see Fig. 6C, filled and unfilled squares at pH 7.0 and 6.0 respectively), Pl-068761 (filled and unfilled triangles for pH 7.0 and 6.0 respectively), and Pl-068767 (filled and unfilled inverted triangles for pH 7.0 and 6.0 respectively) binding to human monocytes. Binding was detected by a fluorescently conjugated anti-human IgG secondary antibody. Fig. 8E shows the comparable blocking of recombinant VISTA multimer binding to activated human CD4+ T cells at pH 6.0 by Pl- 061029 (squares), PI -068761 (triangles), and Pl-068767 (inverted triangles), while a non- VISTA-specific control antibody (circles) did not block VISTA binding. Fig. 8F shows the reduced potency of PI -068761 (triangles) and Pl-068767 (inverted triangles) in mediating antibody-dependent cell cytotoxicity (ADCC) at physiological pH. PI -061029 (squares), a non-VISTA-specific positive control antibody (circles), and a non-VISTA-specific negative control antibody (diamonds) are also shown. NK cell specific lysis of target cells as a percentage of total target cells is plotted on the y-axis and antibody concentrations are plotted on the x-axis. Non-linear regressions are also shown.

[0022] Fig. 9 shows enhanced pharmacokinetics (PK) of acidic pH-selective anti-VISTA antibodies in cynomolgus macaques. The figure shows serum antibody concentrations over time in cynomolgus macaques treated VISTA antibody 2 ("control", circles, see Fig. 6C), VISTA antibody 3 ("acidic pH sensitive", squares, see Fig. 6C), or Pl-068767 (triangles).

[0023] Figs. 10A and 10B show the binding effects of mutations in the acidic pH-selective anti-VISTA antibodies '761 and '767. Fig. 10A shows kinetic binding data of PI -068761 reversion mutants at pH 7.4, pH 6.7 and pH 6.0 and the location of their reversion mutations relative to Pl-068761. Fig. 10B shows kinetic binding data of Pl-068767 reversion mutants at pH 7.4, pH 6.7 and pH 6.0 and the location of their reversion mutations relative to Pl- 068767.

[0024] Figs. 11A-C show epitope binning and mapping of various anti-VISTA antibodies. Fig. 11A shows the VISTA epitope competition for Pl-068761 and Pl-068767 compared to PI -061029 and VISTA antibody controls. Fig. 11B and Fig. 11C show representations of the epitopes of all the residues for blocking hVISTA antibody (Fig. 1 IB) as listed in Table 14 compared to a non-blocking hVISTA antibody (mAbl; Fig. 11C). Amino acid residues 66(H) and 162(A) are indicated to denote the orientation of the molecule. Histidine residues are in grey, and epitope residues are in black. Figs. 12A-C show imaged capillary isoelectric focusing (icIEF) data for the following: Fig. 12A: Pl-061029, Fig. 12B: Pl-068761, and Fig. 12C: Pl-068767. The isoelectric point of the main species (pi main) as well as pi markers are indicated.

[0025] Fig. 13A and B show alignments of variable regions for '029 and '015 progeny clones. Fig. 13A shows the alignment of the amino acid sequences of the variable regions of '029 and its progeny clones. Fig. 13B shows the alighment of the amino acid sequences of the variable regions of '015 and its progeny clones.

[0026] DETAILED DESCRIPTION

[0027] Definitions

[0028] In this application, the use of "or" means "and / or" unless stated otherwise. In the context of a multiple dependent claim, the use of "or" refers back to more than one preceding independent or dependent claim in the alternative only. The terms "comprising,"

[0029] "including," and "having" can be used interchangeably herein. According to the present invention, an "isolated" molecule is a molecule that has been removed from its natural milieu. As such, the term "isolated" does not necessarily reflect the extent to which the molecule has been purified.

[0030] The term "polypeptide" refers to a polymer of amino acid residues, and is not limited to a minimum length. A "protein" may comprise one or more polypeptides. Such polymers of amino acid residues may contain natural or non-natural amino acid residues, and include, but are not limited to, peptides, oligopeptides, dimers, trimers, and multimers of amino acid residues. Both full-length proteins and fragments thereof are encompassed by the definition. The terms also include post-expression modifications of the polypeptide, for example, glycosylation, sialylation, acetylation, phosphorylation, and the like. Furthermore, for purposes of the present invention, a "polypeptide" or "protein" refers to a polypeptide or protein, respectively, which includes modifications, such as deletions, additions, and substitutions (generally conservative in nature), to the native sequence, as long as the protein maintains the desired activity. These modifications may be deliberate, as through site- directed mutagenesis, or may be accidental, such as through mutations of hosts that produce the proteins or errors due to PCR amplification. A protein may comprise two or more polypeptides.

[0031] "VISTA" is an abbreviation for the V-domain immunoglobulin-containing suppressor of T-cell activation protein, which is a member of the B7 family of immune checkpoint regulators. VISTA is also known as the PD-1 homolog (PD1H), B7-H5, C10orf54, differentiation of ESC- 1 (Dies-1), platelet receptor Gi24 precursor, and death domain la (DDI ). The term "hVISTA" or "hu VISTA" herein refers to the human VISTA protein. The amino acid sequence of hVISTA, including its signal peptide is provided in SEQ ID NO: 1, while the sequence without the signal peptide is provided in SEQ ID NO:2. (See the Sequence Table below.) The extracellular domain or "ECD" of VISTA or the "VISTA- ECD" refers to the portion of the VISTA protein that is located in the extracellular space, which, in the case of hVISTA, comprises the amino acids 1-162 of SEQ ID NO:2. (See also Fig. IB.) The "IgV domain" portion of hVISTA comprises residues 5-135 of SEQ ID NO:2.

[0032] The term "leader peptide" or "leader sequence" refers to a sequence of amino acid residues located at the N terminus of a polypeptide that facilitates secretion of a polypeptide from a mammalian cell. A leader sequence may be cleaved upon export of the polypeptide from the mammalian cell, forming a mature protein. Leader sequences may be natural or synthetic, and they may be heterologous or homologous to the protein to which they are attached.

[0033] The term "antibody" or "Ab" herein is used in the broadest sense and encompasses various antibody structures, including but not limited to monoclonal antibodies, polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies), and antibody fragments so long as they exhibit the desired antigen-binding activity. As used herein, the term refers to a molecule comprising at least complementarity-determining region (CDR) 1, CDR2, and CDR3 of a heavy chain and at least CDR1, CDR2, and CDR3 of a light chain, wherein the molecule is capable of binding to antigen. The term antibody includes, but is not limited to, fragments that are capable of binding antigen, such as Fv, single-chain Fv (scFv), Fab, Fab', and (Fab')2. The term antibody also includes, but is not limited to, chimeric antibodies, humanized antibodies, human antibodies, and antibodies of various species such as mouse, cynomolgus monkey, etc. The term "heavy chain" or "HC" refers to a polypeptide comprising at least a heavy chain variable region, with or without a leader sequence. In some embodiments, a heavy chain comprises at least a portion of a heavy chain constant region. The term "full-length heavy chain" refers to a polypeptide comprising a heavy chain variable region and a heavy chain constant region, with or without a leader sequence, and with or without a C-terminal lysine (K).

[0034] The term "heavy chain variable region" or "VH" refers to a region comprising a heavy chain complementary determining region (CDR) 1, framework region (FR) 2, CDR2, FR3, and CDR3 of the heavy chain. In some embodiments, a heavy chain variable region also comprises at least a portion of an FR1 and / or at least a portion of an FR4. As specified below, in some embodiments, a heavy chain CDRl comprises residues 26-35 of a VH SEQ ID NO herein; a heavy chain CDR2 comprises residues 50-66 of a VH SEQ ID NO herein, and a heavy chain CDR3 comprises residues 99-110 of a VH SEQ ID NO herein. In other embodiments, if specified, a heavy chain CDRl corresponds to Kabat residues 31 to 35; a heavy chain CDR2 corresponds to Kabat residues 50 to 65; and a heavy chain CDR3 corresponds to Kabat residues 95 to 102. See, e.g., Kabat Sequences of Proteins of

[0035] Immunological Interest (1987 and 1991, NIH, Bethesda, Md.). In some embodiments the heavy chain CDRs are as specified herein, such as in the sequence table below or in Table 2.

[0036] The term "light chain" or "LC" refers to a polypeptide comprising at least a light chain variable region, with or without a leader sequence. In some embodiments, a light chain comprises at least a portion of a light chain constant region. The term "full-length light chain" refers to a polypeptide comprising a light chain variable region and a light chain constant region, with or without a leader sequence.

[0037] The term "light chain variable region" or "VL" refers to a region comprising a light chain CDRl, FR2, HVR2, FR3, and HVR3. In some embodiments, a light chain variable region also comprises an FR1 and / or an FR4. As specified below, in some embodiments, a light chain CDRl comprises residues 24-35 of a VL SEQ ID NO herein; a light chain CDR2 comprises residues 51-57 of a VL SEQ ID NO herein, and a light chain CDR3 comprises residues 90-98 of a VL SEQ ID NO herein. In other embodiments, if specified, a light chain CDRl corresponds to Kabat residues 24 to 34; a light chain CDR2 corresponds to Kabat residues 50 to 56; and a light chain CDR3 corresponds to Kabat residues 89 to 97. See, e.g., Kabat Sequences of Proteins of Immunological Interest (1987 and 1991, NIH, Bethesda, Md.). In some embodiments, the light chain CDRs are as specified herein such as in the sequence table.

[0038] A "chimeric antibody" refers to an antibody in which a portion of the heavy and / or light chain is derived from a particular source or species, while the remainder of the heavy and / or light chain is derived from a different source or species. In some embodiments, a chimeric antibody refers to an antibody comprising at least one variable region from a first species (such as mouse, rat, cynomolgus monkey, etc.) and at least one constant region from a second species (such as human, cynomolgus monkey, etc.). In some embodiments, a chimeric antibody comprises at least one mouse variable region and at least one human constant region. In some embodiments, a chimeric antibody comprises at least one cynomolgus variable region and at least one human constant region. In some embodiments, all of the variable regions of a chimeric antibody are from a first species and all of the constant regions of the chimeric antibody are from a second species.

[0039] A "humanized antibody" refers to an antibody in which at least one amino acid in a framework region of a non-human variable region has been replaced with the corresponding amino acid from a human variable region. In some embodiments, a humanized antibody comprises at least one human constant region or fragment thereof. In some embodiments, a humanized antibody is an Fab, an scFv, a (Fab')2, etc.

[0040] A "human antibody" as used herein refers to antibodies produced in humans, antibodies produced in non-human animals that comprise human immunoglobulin genes, such as XenoMouse®, and antibodies selected using in vitro methods, such as phage display, wherein the antibody repertoire is based on a human immunoglobulin sequences.

[0041] A "VISTA antibody" or "anti-VISTA antibody" as used herein refers to an antibody that specifically binds to VISTA under at least some conditions such as acidic pH. In some embodiments, the antibody may be a "hu VISTA antibody" or an "anti-hu VISTA antibody" indicting that it specifically binds to the human VISTA protein under at least some conditions such as at acidic pH. A VISTA antibody that specifically binds to the extracellular domain (ECD) of VISTA, for example, may be termed a " VISTA-ECD antibody." In some embodiments, an antibody may bind with higher affinity to VISTA at acidic pH than at neutral and / or physiological pH. In some embodiments, the antibody may bind with higher affinity to VISTA at acidic pH and may only bind negligibly or nonspecifically at neutral and / or physiological pH.

[0042] A "KD" or "dissociation constant" for binding of an antibody to a protein, e.g., a

[0043] VISTA-ECD protein is a measure of the affinity or specific binding of the antibody to the protein, e.g., VISTA-ECD protein. A lower KD indicates improved binding or affinity over a higher KD. A KD is composed of a ratio between an "off-rate" or k0ff or kd and an "on-rate" or kon or kafor the antibody and polypeptide. The off-rate and on-rate are the rates at which the two binding partners associate and dissociate in the system. Thus, a slower off-rate, where the on-rate remains roughly constant, leads to higher overall affinity and thus a lower KD. AS used herein, a k0ff of a particular value "or less" indicates that the k0ff or "off-rate" is as specified or is slower than the rate specified.

[0044] The terms "specific binding" or "specifically binds" or like terms signify that the KD for the binding of two polypeptides, such as an antibody and its polypeptide target, is less than would be the case between two random polypeptides existing under the same conditions. In other words, the KD is less than that due to nonspecific aggregation of polypeptides in the system.

[0045] In some embodiments, the antibodies specifically bind to a VISTA-ECD protein at a particular pH or pH range. An "acidic" pH herein generally refers to a pH less than 7.0, a "basic" pH generally refers to a pH higher than 7.0 and a "neutral" pH generally refers to a pH of about 7.0. A "physiological pH" herein refers to a pH in normal (i.e., non-cancerous) physiological conditions, e.g., from 7.35 to 7.45, or from 7.3 to 7.4, such as of about 7.4. Phrases such as "binding in acidic conditions" or "binding in physiological conditions" and the like herein, used in the context of binding of two molecules such as VISTA and a VISTA binding partner or VISTA and a T cell, refer to binding in acidic pH and binding in physiological pH, respectively.

[0046] When referring to an antibody that "blocks binding of or "inhibits binding of a ligand (or receptor) or a competing antibody to a receptor (or ligand) alone or on a cell, binding is blocked if there is an overall decrease that is statistically significant compared to a control, e.g., an overall decrease of 50% or greater, e.g., an overall decrease of 75%, 80%, 85%), 90%), 95%o, or greater. An "anti-VISTA blocking antibody," for example, is one that can block binding of VISTA to PSGL-1 or another VISTA ligand or receptor or heparan sulfate proteoglycans under at least some conditions such as at acidic pH.

[0047] A "tumor model," as used herein, refers to an in vivo preclinical assay, which may be used for studying the biological activity of a VISTA-ECD antibody, and includes xenograft or native mouse tumor assay systems. In some cases, a tumor model may allow for tracking of tumor size or growth upon treatment with the antibody, and / or tracking of the presence of immune cells in the tumor, such as specific types of T-cells or NK cells, in order to determine whether an antibody has triggered or enhanced an immune response.

[0048] The term "immune stimulating agent" as used herein refers to a molecule that stimulates the immune system by either acting as an agonist of an immune-stimulatory molecule, including a co-stimulatory molecule, or acting as an antagonist of an immune inhibitory molecule, including a co-inhibitory molecule. The immune-stimulatory molecule or immune inhibitory molecule may be an immune checkpoint regulator such as VISTA or another B7 family member or another molecule as described further below. An immune stimulating agent may be a biologic, such as an antibody or antibody fragment, other protein, or vaccine, or may be a small molecule drug. An "immune stimulatory molecule" includes a receptor or ligand that acts to enhance, stimulate, induce, or otherwise "turn-on" an immune response. Immune stimulatory molecules as defined herein include co-stimulatory molecules. An "immune inhibitory molecule" includes a receptor or ligand that acts to reduce, inhibit, suppress, or otherwise "turn-off an immune response. Immune inhibitory molecules as defined herein include co-inhibitory molecules. Such immune stimulatory and immune inhibitory molecules may be, for example, receptors or ligands found on immune cells such as a T cells, or found on cells involved in innate immunity such as NK cells.

[0049] "Percent (%) amino acid sequence identity" and "homology" with respect to a peptide, polypeptide or antibody sequence are defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the specific peptide or polypeptide sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN or MEGALIGNTM (DNASTAR) software. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared.

[0050] The terms "trigger" or "enhance" refer to an initiation or increase of any event (such as protein ligand binding) or to an initiation or increase of any biological activity (such as an immune response) or phenotypic characteristic or to the initiation or increase in the incidence, degree, or likelihood of that activity or characteristic. To "trigger" or "enhance" is to begin or increase an activity, function, and / or amount as compared to a reference. It is not necessary that the triggering or enhancement be complete. For example, in certain embodiments, by "enhance" is meant the ability to cause an overall increase of 20% or greater. In another embodiment, by "enhance" is meant the ability to cause an overall increase of 50% or greater. In yet another embodiment, by "enhance" is meant the ability to cause an overall increase of 75%, 85%, 90%, 95%, or greater.

[0051] The terms "inhibition" or "inhibit" more generally refer to a decrease or cessation of any event (such as protein ligand binding) or to a decrease or cessation of any phenotypic characteristic or to the decrease or cessation in the incidence, degree, or likelihood of that characteristic. To "reduce" or "inhibit" is to decrease, reduce or arrest an activity, function, and / or amount as compared to a reference. It is not necessary that the inhibition or reduction be complete. For example, in certain embodiments, by "reduce" or "inhibit" is meant the ability to cause an overall decrease of 20% or greater. In another embodiment, by "reduce" or "inhibit" is meant the ability to cause an overall decrease of 50% or greater. In yet another embodiment, by "reduce" or "inhibit" is meant the ability to cause an overall decrease of 75%, 85%, 90%, 95%, or greater.

[0052] "Treatment" as used herein, covers any administration or application of a therapeutic for disease in a human, and includes inhibiting the disease or progression of the disease or one or more disease symptoms, inhibiting or slowing the disease or its progression or one or more of its symptoms, arresting its development, partially or fully relieving the disease or one or more of its symptoms, or preventing a recurrence of one or more symptoms of the disease.

[0053] The terms "subject" and "patient" are used interchangeably herein to refer to a human.

[0054] The term "effective amount" or "therapeutically effective amount" refers to an amount of a drug effective for treatment of a disease or disorder in a subject, such as to partially or fully relieve one or more symptoms. In some embodiments, an effective amount refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired therapeutic or prophylactic result.

[0055] The term "cancer" is used herein to refer to a group of cells that exhibit abnormally high levels of proliferation and growth. A cancer may be benign (also referred to as a benign tumor), pre-malignant, or malignant. Cancer cells may be solid cancer cells or leukemic cancer cells. The term "tumor growth" is used herein to refer to proliferation or growth by a cell or cells that comprise a cancer that leads to a corresponding increase in the size or extent of the cancer.

[0056] Examples of cancers applicable to methods of treatment herein include but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia. More particular nonlimiting examples of such cancers include squamous cell cancer, small-cell lung cancer, pituitary cancer, esophageal cancer, astrocytoma, soft tissue sarcoma, non-small cell lung cancer (including squamous cell non-small cell lung cancer), adenocarcinoma of the lung, squamous carcinoma of the lung, cancer of the peritoneum, hepatocellular cancer, gastrointestinal cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer, colon cancer, colorectal cancer, endometrial or uterine carcinoma, salivary gland carcinoma, kidney cancer, renal cell carcinoma, liver cancer, prostate cancer, vulval cancer, thyroid cancer, hepatic carcinoma, brain cancer, endometrial cancer, testis cancer, cholangiocarcinoma, gallbladder carcinoma, gastric cancer, melanoma, and various types of head and neck cancer (including squamous cell carcinoma of the head and neck).

[0057] Administration "in combination with" one or more further therapeutic agents includes simultaneous (concurrent) and consecutive (sequential) administration in any order. A "pharmaceutically acceptable carrier" refers to a non-toxic solid, semisolid, or liquid filler, diluent, encapsulating material, formulation auxiliary, or carrier conventional in the art for use with a therapeutic agent that together comprise a "pharmaceutical

[0058] composition" for administration to a subject. A pharmaceutically acceptable carrier is non- toxic to recipients at the dosages and concentrations employed and is compatible with other ingredients of the formulation. The pharmaceutically acceptable carrier is appropriate for the formulation employed. For example, if the therapeutic agent is to be administered orally, the carrier may be a gel capsule. If the therapeutic agent is to be administered subcutaneously, the carrier ideally is not irritable to the skin and does not cause injection site reaction.

[0059] A "chemotherapeutic agent" is a chemical compound useful in the treatment of cancer. Examples of chemotherapeutic agents that can be administered in methods herein include, but are not limited to, alkylating agents such as thiotepa and Cytoxan®

[0060] cyclosphosphamide; alkyl sulfonates such as busulfan, improsulfan and piposulfan; aziridines such as benzodopa, carboquone, meturedopa, and uredopa; ethylenimines and

[0061] methylamelamines including altretamine, triethylenemelamine, trietylenephosphoramide, triethiylenethiophosphoramide and trimethylolomelamine; acetogenins (especially bullatacin and bullatacinone); a camptothecin (including the synthetic analogue topotecan); bryostatin; callystatin; CC-1065 (including its adozelesin, carzelesin and bizelesin synthetic analogues); cryptophycins (particularly cryptophycin 1 and cryptophycin 8); dolastatin; duocarmycin (including the synthetic analogues, KW-2189 and CB 1-TM1); eleutherobin; pancrati statin; a sarcodictyin; spongistatin; nitrogen mustards such as chlorambucil, chlornaphazine, cholophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard; nitrosureas such as carmustine, chlorozotocin, fotemustine, lomustine, nimustine, and ranimnustine; antibiotics such as the enediyne antibiotics (e.g., calicheamicin, especially calicheamicin gammall and calicheamicin omegall (see, e.g., Agnew, Chem Intl. Ed. Engl., 33 : 183-186 (1994)); dynemicin, including dynemicin A; bisphosphonates, such as clodronate; an esperamicin; as well as neocarzinostatin chromophore and related

[0062] chromoprotein enediyne antiobiotic chromophores), aclacinomysins, actinomycin, authramycin, azaserine, bleomycins, cactinomycin, carabicin, carminomycin, carzinophilin, chromomycinis, dactinomycin, daunorubicin, detorubicin, 6-diazo-5-oxo-L-norleucine, Adriamycin®doxorubicin (including morpholino-doxorubicin, cyanomorpholino- doxorubicin, 2-pyrrolino-doxorubicin and deoxydoxorubicin), epirubicin, esorubicin, idarubicin, marcellomycin, mitomycins such as mitomycin C, mycophenolic acid, nogalamycin, olivomycins, peplomycin, potfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; anti-metabolites such as methotrexate and 5-fluorouracil (5-FU); folic acid analogues such as denopterin, methotrexate, pteropterin, trimetrexate; purine analogs such as fludarabine, 6- mercaptopurine, thiamiprine, thioguanine; pyrimidine analogs such as ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine; androgens such as calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone; anti-adrenals such as aminoglutethimide, mitotane, trilostane; folic acid replenisher such as frolinic acid; aceglatone; aldophosphamide glycoside; aminolevulinic acid; eniluracil; amsacrine; bestrabucil; bisantrene; edatraxate; defofamine; demecolcine; diaziquone; elfornithine; elliptinium acetate; an epothilone; etoglucid; gallium nitrate;

[0063] hydroxyurea; lentinan; lonidainine; maytansinoids such as maytansine and ansamitocins; mitoguazone; mitoxantrone; mopidanmol; nitraerine; pentostatin; phenamet; pirarubicin; losoxantrone; podophyllinic acid; 2- ethylhydrazide; procarbazine; PSK®polysaccharide complex (JHS Natural Products, Eugene, OR); razoxane; rhizoxin; sizofiran;

[0064] spirogermanium; tenuazonic acid; triaziquone; 2,2',2"-trichlorotriethylamine; tnchothecenes (especially T-2 toxin, verracurin A, roridin A and anguidine); urethan; vindesine;

[0065] dacarbazine; mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine; arabinoside ("Ara-C"); cyclophosphamide; thiotepa; taxoids, e.g., Taxol®paclitaxel (Bristol- Myers Squibb Oncology, Princeton, N.J.), Abraxane®Cremophor-free, albumin-engineered nanoparticle formulation of paclitaxel (American Pharmaceutical Partners, Schaumberg, Illinois), and Taxotere®doxetaxel (Rhone- Poulenc Rorer, Antony, France); chloranbucil; Gemzar®gemcitabine; 6-thioguanine; mercaptopurine; methotrexate; platinum analogs such as cisplatin, oxaliplatin and carboplatin; vinblastine; platinum; etoposide (VP-16);

[0066] ifosfamide; mitoxantrone; vincristine; Navelbine®vinorelbine; novantrone; teniposide;

[0067] edatrexate; daunomycin; aminopterin; xeloda; ibandronate; irinotecan (Camptosar, CPT-11) (including the treatment regimen of irinotecan with 5-FU and leucovorin); topoisomerase inhibitor RFS 2000; difluorometlhylornithine (DMFO); retinoids such as retinoic acid;

[0068] capecitabine; combretastatin; leucovorin (LV); oxaliplatin, including the oxaliplatin treatment regimen (FOLFOX); inhibitors of PKC-alpha, Raf, H-Ras, EGFR (e.g., erlotinib (Tarceva®)) and VEGF-A that reduce cell proliferation and pharmaceutically acceptable salts, acids or derivatives of any of the above.

[0069] Further nonlimiting exemplary chemotherapeutic agents that can be administered in methods herein include anti-hormonal agents that act to regulate or inhibit hormone action on cancers such as anti-estrogens and selective estrogen receptor modulators (SERMs), including, for example, tamoxifen (including Nolvadex® tamoxifen), raloxifene, droloxifene, 4-hydroxytamoxifen, trioxifene, keoxifene, LY1 17018, onapristone, and Fareston® toremifene; aromatase inhibitors that inhibit the enzyme aromatase, which regulates estrogen production in the adrenal glands, such as, for example, 4(5)-imidazoles, aminoglutethimide, Megase® megestrol acetate, Aromasin® exemestane, formestanie, fadrozole, Rivisor® vorozole, Femara® letrozole, and Arimidex® anastrozole; and anti-androgens such as flutamide, nilutamide, bicalutamide, leuprolide, and goserelin; as well as troxacitabine (a 1,3- dioxolane nucleoside cytosine analog); antisense oligonucleotides, particularly those which inhibit expression of genes in signaling pathways implicated in abherant cell proliferation, such as, for example, PKC-alpha, Ralf and H-Ras; ribozymes such as a VEGF expression inhibitor (e.g., Angiozyme® ribozyme) and a HER2 expression inhibitor; vaccines such as gene therapy vaccines, for example, Allovectin® vaccine, Leuvectin® vaccine, and Vaxid® vaccine; Proleukin® rIL-2; Lurtotecan® topoisomerase 1 inhibitor; Abarelix® rmRH; and pharmaceutically acceptable salts, acids or derivatives of any of the above.

[0070] An "anti-angiogenesis agent" or "angiogenesis inhibitor" refers to a small molecular weight substance, a polynucleotide (including, e.g., an inhibitory RNA (RNAi or siRNA)), a polypeptide, an isolated protein, a recombinant protein, an antibody, or conjugates or fusion proteins thereof, that inhibits angiogenesis, vasculogenesis, or undesirable vascular permeability, either directly or indirectly. It should be understood that the anti-angiogenesis agent includes those agents that bind and block the angiogenic activity of the angiogenic factor or its receptor. For example, an anti-angiogenesis agent that can be administered in methods herein can include an antibody or other antagonist to an angiogenic agent, e.g., antibodies to VEGF -A (e.g., bevacizumab (Avastin®)) or to the VEGF -A receptor (e.g., KDR receptor or Flt-1 receptor), anti-PDGFR inhibitors such as Gleevec®(Imatinib

[0071] Mesylate), small molecules that block VEGF receptor signaling (e.g., PTK787 / ZK2284, SU6668, Sutent® / SUl 1248 (sunitinib malate), AMG706, or those described in, e.g., international patent application WO 2004 / 113304). Anti-angiogensis agents also include native angiogenesis inhibitors , e.g., angiostatin, endostatin, etc. See, e.g., Klagsbrun and D'Amore (\99\) Annu. Rev. Physiol. 53 :217-39; Streit and Detmar (2003) Oncogene 22:3172-3179 (e.g., Table 3 listing anti-angiogenic therapy in malignant melanoma); Ferrara & Alitalo (1999) Nature Medicine 5(12): 1359-1364; Tonini et al. (2003) Oncogene 22:6549- 6556 (e.g., Table 2 listing known anti-angiogenic factors); and, Sato (2003) Int. J. Clin. Oncol. 8:200-206 (e.g., Table 1 listing anti-angiogenic agents used in clinical trials).

[0072] A "growth inhibitory agent" as used herein refers to a compound or composition that inhibits growth of a cell (such as a cell expressing VEGF) either in vitro or in vivo. Thus, the growth inhibitory agent that can be administered in methods herein may be one that significantly reduces the percentage of cells (such as a cell expressing VEGF) in S phase. Examples of growth inhibitory agents include, but are not limited to, agents that block cell cycle progression (at a place other than S phase), such as agents that induce Gl arrest and M- phase arrest. Classical M-phase blockers include the vincas (vincristine and vinblastine), taxanes, and topoisomerase II inhibitors such as doxorubicin, epirubicin, daunorubicin, etoposide, and bleomycin. Those agents that arrest Gl also spill over into S-phase arrest, for example, DNA alkylating agents such as tamoxifen, prednisone, dacarbazine,

[0073] mechlorethamine, cisplatin, methotrexate, 5-fluorouracil, and ara-C. Further information can be found in Mendelsohn and Israel, eds., The Molecular Basis of Cancer, Chapter 1, entitled "Cell cycle regulation, oncogenes, and antineoplastic drugs" by Murakami et al. (W.B.

[0074] Saunders, Philadelphia, 1995), e.g., p. 13. The taxanes (paclitaxel and docetaxel) are anticancer drugs both derived from the yew tree. Docetaxel (Taxotere®, Rhone-Poulenc Rorer), derived from the European yew, is a semisynthetic analogue of paclitaxel (Taxol®, Bristol-Myers Squibb). Paclitaxel and docetaxel promote the assembly of microtubules from tubulin dimers and stabilize microtubules by preventing depolymerization, which results in the inhibition of mitosis in cells.

[0075] The term "anti-neoplastic composition" refers to a composition useful in treating cancer comprising at least one active therapeutic agent. Examples of therapeutic agents include, but are not limited to, e.g., chemotherapeutic agents, growth inhibitory agents, cytotoxic agents, agents used in radiation therapy, anti-angiogenesis agents, cancer immunotherapeutic agents, apoptotic agents, anti-tubulin agents, and other-agents to treat cancer, such as anti-HER-2 antibodies, anti-CD20 antibodies, an epidermal growth factor receptor (EGFR) antagonist (e.g., a tyrosine kinase inhibitor), HERl / EGFR inhibitor (e.g., erlotinib (Tarceva®), platelet derived growth factor inhibitors (e.g., Gleevec®(Imatinib Mesylate)), a COX-2 inhibitor (e.g., celecoxib), interferons, CTLA4 inhibitors (e.g., anti- CTLA antibody ipilimumab (YERVOY®)), PD-1 ore PD-L1 inhibitors (e.g., OPDIVO®, KEYTRUDA®, TECENTRIQ®, BAVENCIO®, FMFINZI®), TEVI3 inhibitors (e.g., anti- TEVI3 antibodies), cytokines, antagonists (e.g., neutralizing antibodies) that bind to one or more of the following targets ErbB2, ErbB3, ErbB4, PDGFR-beta, BlyS, APRIL, BCMA, CTLA4, TIM3, or VEGF receptor(s), TRAIL / Apo2, and other bioactive and organic chemical agents, etc. Combinations thereof are also included in this disclosure.

[0076] Antibodies Specifically Binding to VISTA-ECD at Acidic pH

[0077] Because VISTA has a large number of histidine residues in its ECD, its folding and overall structure, as well as the surface available for the binding of ligands such as antibodies, may differ at acidic pH compared to neutral pH, in particular, near pH 6.5, which is the pKafor histidine. Since tumor microenvironments are generally acidic, for binding to VISTA in those microenvironments, an antibody may need to bind with specificity to VISTA at acidic pH where at least some of the surface histidine residues are more likely to be protonated.

[0078] The Sequence Table below provides the amino acid sequence of human VISTA (h VIST A) with or without signal peptide (SEQ ID NO: 1 and SEQ ID NO: 2 (mature hVISTA)), respectively. The signal peptide constitutes amino acid residues 1-32 of SEQ ID NO: 1. The extracellular domain (ECD) consists of amino acid residues 1-162 of SEQ ID NO: 2). The IgV domain constitutes amino acids residues 37-167 of SEQ ID NO: 1 and amino acid residues 5- 135 of SEQ ID NO: 2. The stalk region is at amino acid residues 172- 194 of SEQ ID NO: 1 and amino acid residues 136-162 of SEQ ID NO: 2; the

[0079] transmembrane domain is at amino acid residues 195-216 of SEQ ID NO: 1 and amino acid residues 163-184 of SEQ ID NO: 2. Amino acid residue 187 of SEQ ID NO: 1 and 155 of SEQ ID NO: 2 (bold and underlined) can be either D or E, which represents a polymorphism in hVISTA. That residue is shown in bold, underlining. Accordingly, SEQ ID NO: 1 and SEQ ID NO:2 encompass both of the human polymorphisms at that residue. The histidine residues in the ECD of VISTA are grey-shaded.

[0080] Anti-VISTA antibodies (Abs) may specifically bind to the VISTA-ECD or fragments thereof, e.g., comprising the IgV domain of VISTA or a region from hVISTA comprising, e.g., amino acids 20-95, 20-70 35-70, 35-95, 35-127 or 37-125 of SEQ ID NO: 2 at acidic pH. In certain embodiments, an Ab specifically binds to the VISTA-ECD protein at a pH that is less than pH 7.0. In certain embodiments, an Ab specifically binds to the VISTA- ECD protein at a pH that is less than pH 6.8. In certain embodiments, an Ab specifically binds to the VISTA-ECD protein at a pH that is less than pH 6.5. In certain embodiments, an Ab specifically binds to the VISTA-ECD protein at a pH that is less than pH 6.3. In certain embodiments, an Ab specifically binds to the VISTA-ECD protein at a pH that is less than pH 6.0. In certain embodiments, an Ab specifically binds to the VISTA-ECD protein at a pH that is less than pH 5.8. In certain embodiments, an Ab specifically binds to the VISTA- ECD protein at a pH that is less than pH 5.5. In certain embodiments, an Ab specifically binds to the VISTA-ECD protein at a pH that is less than pH 5.3. In certain embodiments, an Ab specifically binds to the VISTA-ECD protein at a pH that is less than pH 5.0.

[0081] Certain Abs specifically bind to a VISTA-ECD protein at a pH within a range of pH 5.0-pH 7.0. Certain Abs specifically bind to the VISTA-ECD protein at a pH within a range of pH 5.0- pH 6.5. Certain Abs specifically bind to the VISTA-ECD protein at a pH within a range of pH 5.0-pH 6.0. Certain Abs specifically bind to the VISTA-ECD protein at a pH within a range of pH 5.5- pH 7.0. Certain Abs specifically bind to the VISTA-ECD protein at a pH within a range of pH 5.5-pH 6.5. Certain Abs specifically bind to the VISTA-ECD protein at a pH within a range of pH 6.0-6.5. Provided herein are also Abs that bind to a VISTA-ECD protein, such as hVISTA- ECD or fragments thereof comprising the IgV domain of VISTA or a region from hVISTA comprising, e.g., amino acids 20-95, 20-70 35-70, 35-95, 35-127 or 37-125 of SEQ ID NO:2 at a pH of 6.5 or less, with a KD of 10"6M or less. In some embodiments, the Abs bind with a KD of 10"7M or less. In some embodiments, the Abs bind with a KD of 10"8M or less. In some embodiments, the Abs bind with a KD of 10"9M. In some embodiments, the Abs bind with a KD of 10"10M or less. For example, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"8M or less.

[0082] Provided herein are also Abs that bind to the VISTA-ECD protein within a pH range of 6.0-6.5 with a KD of 10"6M or less. In some embodiments, the Abs bind with a KD of 10"7M or less. In some embodiments, the Abs bind with a KD of 10"8M or less. In some embodiments, the Abs bind with a KD of 10"9M. In some embodiments, the Abs bind with a KD of 10"10M or less. For example, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less, e.g., within a pH range of 6.0-6.5, with a KD of 10"7M or less. Further, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less, e.g., within a pH range of 6.0-6.5, with a KD of 10"8M or less. An Ab may bind to hVISTA-ECD at a pH of 6.5 or less, e.g., within a pH range of 6.0-6.5, with a KD of 10"9M or less.

[0083] Provided herein are also Abs that specifically bind to a VISTA-ECD protein, such as hVISTA-ECD or fragments thereof comprising the IgV domain of VISTA or a region from hVISTA comprising, e.g., amino acids 20-95, 20-70 35-70, 35-95, 35-127 or 37-125 of SEQ ID NO:2, e.g., at a pH of 6.5 or less, with a k0ff of 10-5s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 10"4s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 2 10"4s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 5 10"4s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 7 10"4s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 10"3s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 2 10"3s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 5 10"3s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 7 10"3s"1or less at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 10"2s"1at either 25°C or at 37°C. In some embodiments, the Abs have a k0ff of 10"1s"1or less at either 25°C or at 37°C. For example, an Ab may specifically bind to the VISTA-ECD protein at a pH of 6.5 or less with a k0ff of 10"3s"1or less at either 25°C or at 37°C. An Ab may specifically bind to hVISTA-ECD at a pH of 6.5 or less with a k0ff of 10"3s"1or less at either 25°C or at 37°C. Further, an Ab may

[0084] specifically bind to the VISTA-ECD protein at a pH of 6.5 or less with a k0ff of 10"2s"1or less at either 25°C or at 37°C.

[0085] Provided herein are Abs that bind to a VISTA-ECD protein, such as hVISTA-ECD or fragments thereof comprising the IgV domain of VISTA or a region from hVISTA comprising, e.g., amino acids 20-95, 20-70 35-70, or 35-95, 35-95, 35-127 or 37-125 of SEQ ID NO:2, e.g., at a pH of 6.5 or less, with (i) a KD of 10"6M or less, 10"7M or less, 10"8M or less, 10"9M or less or 10"10M or less and (ii) a k0ff rate of 10"5s"1or less, 10"4(or 2, 5 or 7 10"4) s"1or less, 10"3(or 2, 5 or 7 10"4) s"1or less, 10"2s"1or less, or 10"1s"1or less, as measured, e.g., at 25°C or at 37°C. For example, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"7M or less and a k0ff rate of 10"3s"1or less, as measured, e.g., at 25°C or at 37°C. An Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"8M or less and a k0ff rate of 10"3s"1or less, as measured, e.g., at 25°C or at 37°C. An Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"8M or less and a k0ff rate of 10"2s"1or less, as measured, e.g., at 25°C or at 37°C. For example, an Ab may bind to hVISTA-ECD at a pH of 6.5 or less with a KD of 10"7M or less and a k0ff rate of 10"3s_1or less, as measured, e.g., at 25°C or at 37°C. An Ab may bind to hVISTA-ECD at a pH of 6.5 or less with a KD of 10"9M or less and a k0ff rate of 10"3s"1or less, as measured, e.g., at 25°C or at 37°C. An Ab may bind to hVISTA-ECD at a pH of 6.5 or less with a KD of 10"9M or less and a k0ff rate of 10"2s"1or less, as measured, e.g., at 25°C or at 37°C. An Ab may bind to hVISTA-ECD at a pH of 6.5 or less with a KD of 10"8M or less and a k0ff rate of 10"4(or 2, 5 or 7 10"4) s"1or less, as measured, e.g., at 25°C or at 37°C. An Ab may bind to hVISTA-ECD at a pH of 6.5 or less with a KD of 10"8M or less and a k0ff rate of 10"5(or 2, 5 or 7 10"5) s_1or less, as measured, e.g., at 25°C or at 37°C. An Ab may bind to hVISTA-ECD at a pH of 6.5 or less with a KD of 10"9M or less and a k0ff rate of 10"4(or 2, 5 or 7 10"4) s"1or less, as measured, e.g., at 25°C or at 37°C. An Ab may bind to hVISTA-ECD at a pH of 6.5 or less with a KD of 10"9M or less and a k0ff rate of 10"5(or 2, 5 or 7 10"5) s"1or less, as measured, e.g., at 25°C or at 37°C.

[0086] Provided herein are Abs that specifically bind to the VISTA-ECD protein, e.g., at a pH of 6.5 or less, with a k0n of 104M_1s"1or higher at 25°C or at 37°C. In some such embodiments, the Abs may bind with a k0n of 105M_1s"1or higher. In some such

[0087] embodiments, the Abs may bind with a k0n of 106M_1s_1or higher. In some such

[0088] embodiments, the Abs may bind with a k0n of 107M_1s_1or higher. For example, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a k0n of 106M_1s"1or higher, as measured, e.g., at 25°C or at 37°C. For example, an Ab may bind to the ECD of hVISTA at a pH of 6.5 or less with a k0n of 106M_1s_1or higher, as measured, e.g., at 25°C or at 37°C.

[0089] Provided herein are Abs that bind to the VISTA-ECD protein, e.g., at a pH of 6.5 or less, with (i) a KD of 10"6M or less, 10"7M or less, 10"8M or less, 10"9M or less or 10"10M or less and (ii) a k0n of 104M_1s_1or higher, 105M"1s"1or higher, 106M_1s_1or higher, 107M"1s"1or higher, as measured, e.g., at 25°C or at 37°C. For example, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"7M or less and a k0n rate of 106M"1s"1or higher, as measured, e.g., at 25°C or at 37°C. For example, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"8M or less and a k0n rate of 106M"1s"1or higher, as measured, e.g., at 25°C or at 37°C. For example, an Ab may bind to hVISTA-ECD at a pH of 6.5 or less with a KD of 10"7M or less and a k0n rate of 106M"1s"1or higher, as measured, e.g., at 25°C or at 37°C. For example, an Ab may bind to hVISTA- ECD at a pH of 6.5 or less with a KD of 10"8M or less and a k0n rate of 106M_1s"1or higher, as measured, e.g., at 25°C or at 37°C.

[0090] In some embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"7M or less as well as with a k0ff of 10"5s"1or less, 2 10"5s"1or less, 5 10"5s"1or less, 7 10"5s"1or less, 10"4s"1or less, 2 10"4s"1or less, 5 10"4s"1or less, 7 10"4s"1or less, 10"3s"1or less, 2 10"3s"1or less, 5 10"3s"1or less, 7 10"3s"1or less, 10"2s"1or less, or 10"1s"1or less, as measured, e.g., at 25°C or at 37°C. In some embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"9M or less as well as with a k0ff of 10"5s"1or less, 10"4s"1or less, 10"3s"1or less, 10"2s"1or less, or 10"1s"1or less, as measured, e.g., at 25°C or at 37°C. In some such embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"10M or less as well as with a k0ff of 10"5s"1or less, 10"4s"1or less, 10"3s"1or less, 10"2s"1or less, or 10"1s"1or less, as measured, e.g., at 25°C or at 37°C.

[0091] In some embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"7M or less as well as with a k0n of 104M_1s_1or higher, 105M_1s"1or higher, 106M_1s_1or higher, 107M_1s_1or higher, as measured, e.g., at 25°C or at 37°C. In some embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"8M or less as well as with a k0n of 104M"1s"1or higher, 105M"1s"1or higher, 106M"1s"1or higher, 107M_1s"1or higher, as measured, e.g., at 25°C or at 37°C. In some embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"9M or less as well as with a k0n of 104M"1s_1or higher, 105M"1s_1or higher, 106M"1s_1or higher, 107M_1s"1or higher, as measured, e.g., at 25°C or at 37°C. In some such embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"10M or less as well as with a k0n of 104M"1s_1or higher, 105M"1s_1or higher, 106M"1s_1or higher, 107M_1s_1or higher, as measured, e.g., at 25°C or at 37°C.

[0092] In some embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"7M or less as well as with a k0ff of 10"5s"1or less, 10"4s"1or less, 10"3s"1or less, 10"2s"1or less, or 10"1s"1or less, as measured, e.g., at 25°C or at 37°C, and a k0n of 104M_1s"1or higher, 105M_1s_1or higher, 106M_1s_1or higher, 107M_1s_1or higher, as measured, e.g., at 25°C or at 37°C. In some embodiments, an Ab may bind to the VISTA- ECD protein at a pH of 6.5 or less with a KD of 10"8M or less as well as with a k0ff of 10"5s"1or less, 10"4s"1or less, 10"3s"1or less, 10"2s"1or less, or 10"1s"1or less, as measured, e.g., at 25°C or at 37°C, and a k0n of 104M"1s"1or higher, 105M"1s"1or higher, lO6]^"1s"1or higher, 107M"1s"1or higher, as measured, e.g., at 25°C or at 37°C. In some embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"9M or less as well as with a k0ff of 10"5s"1or less, 10"4s"1or less, 10"3s"1or less, 10"2s"1or less, or 10"1s"1or less, as measured, e.g., at 25°C or at 37°C, and a k0n of 104M_1s_1or higher, 105M_1s_1or higher, 106M_1s_1or higher, 107M_1s_1or higher, as measured, e.g., at 25°C or at 37°C. In some such embodiments, an Ab may bind to the VISTA-ECD protein at a pH of 6.5 or less with a KD of 10"10M or less as well as with a k0ff of 10"5s"1or less, 10"4s"1or less, 10"3s"1or less, 10"2s"1or less, or 10"1s"1or less, as measured, e.g., at 25°C or at 37°C, and a k0n of 104M_1s"1or higher, 105M_1s_1or higher, 106M_1s_1or higher, 107M_1s_1or higher, as measured, e.g., at 25°C or at 37°C.

[0093] As noted also above, in some of the above embodiments, the VISTA-ECD protein is hVISTA-ECD or is a portion of hVISTA-ECD such as, for example, the IgV domain. In some of the above embodiments, the Ab may bind specifically to an epitope comprising amino acids 20-95 of SEQ ID NO:2. In some of the above embodiments, the Ab may bind specifically to an epitope comprising amino acids 20-70 of SEQ ID NO:2. In some of the above embodiments, the Ab may bind specifically to an epitope comprising amino acids 35- 95 of SEQ ID NO:2. In some of the above embodiments, the Ab may bind specifically to an epitope comprising amino acids 35-70 of SEQ ID NO:2. In some embodiments above, the epitope is a three-dimensional epitope that comprises not only one of the above portions of SEQ ID NO:2 from residues 20-95, 20-70, 35-95, or 35-70, but also another portion of SEQ ID NO:2, such as residues 95-105 of SEQ ID NO:2. In certain embodiments, an Ab binds to the epitope of hVISTA to which an Ab described in WO2015 / 097536 binds. For example, an Ab may compete or cross-compete for binding to hVISTA with an Ab disclosed in WO2015 / 097536. In certain embodiments, an Ab binds to a conformational epitope of human VISTA. In certain embodiments, an Ab binds to a conformational epitope that comprises, or is present within, residues 103-111 of SEQ ID NO: 2 and 136-146 of SEQ ID NO:2 for human VISTA. In certain embodiments, an Ab binds to a conformational epitope that comprises, or is present within, residues 24-36, 54-65, and 100-102 of SEQ ID NO:2 for human VISTA. In certain embodiments, an Ab binds to a conformational epitope that comprises amino acid residues in the FG loop of human VISTA. In some embodiments, an Ab binds to a polypeptide comprising amino acid residues 35 to 127 and / or 37-125 of SEQ ID NO: 2. In some embodiments, an Ab binds to a VISTA ECD polypeptide or portion thereof comprising amino acid residues 350-127 of SEQ ID NO: 2, but the antibody does not bind or binds with reduced affinity to the VISTA ECD polyptide or portion thereof comprising an amino acid substitution, wherein the substitution (1) is substitution of one of the following amino acid residues: T35, Y37, K38, T39, Y41, R54, T61, F62, Q63, L65, H66, L67, H68, H69, F97, LI 15, VI 17, 1119, H121, H122, S124, E125, R127 and SEQ ID NO: 2 or (2) is a substitution of one of the following amino acid residues: Y37, T39, R54, F62, Q63, H66, LI 15, VI 17, 1119, S124, or E125. In some embodiments, an anti-VISTA antibody has the same binding characteristics (or significantly the same binding

[0094] characteristics) as an antibody described herein, e.g., as set forth in the Examples.

[0095] Some of the above antibodies may show differential binding affinity for VISTA-ECD proteins depending upon pH. Certain Abs specifically binding to a VISTA-ECD protein in acidic conditions, e.g., at pH 6.5 or less, also specifically bind the VISTA-ECD protein at neutral and / or alkaline pH with similar affinity (i.e. they are "pan binders"). For example, some such Abs may bind to the VISTA-ECD protein with a KD of 10"7M or less at both pH 6.5 and at pH 7.0 (at a constant temperature, e.g., of 25°C or at 37°C) such that the KD at pH 6.5 is within 1.5-fold of the KD at pH 7.0. Some such Abs may bind to the VISTA-ECD protein with a KD of 10"8M or less at both pH 6.5 and at pH 7.0 (at a constant temperature, e.g., of 25°C or at 37°C) such that the KD at pH 6.5 is within 1.5-fold of the KD at pH 7.0. Some such Abs may bind to hVISTA-ECD with a KD of 10"8M or less at both pH 6.5 and at pH 7.0 (at a constant temperature, e.g., of 25°C or at 37°C) such that the KD at pH 6.5 is within 1.5-fold of the KD at pH 7.0.

[0096] Certain Abs specifically binding to a VISTA-ECD protein in acidic conditions, e.g., at pH 6.5 or less, may bind the VISTA-ECD protein at neutral, physiological, and / or alkaline conditions with lower affinity ("pH sensitive binders" or "pH sensitive Abs"). Certain Abs specifically binding to a VISTA-ECD protein in acidic conditions, e.g., at pH 6.5 or less, may have non significant, e.g., nearly undetectable, binding to the VISTA-ECD protein in neutral, physiological and / or alkaline conditions. For example, in some embodiments, Abs may bind to the VISTA-ECD protein with a KD of 10"8M or less at pH 6.5 and with a KD of more than 10"8M at pH 7.0 and / or pH 7.4. In some such embodiments, Abs may bind to the VISTA-ECD protein with a KD of 10-8M or less at pH 6.5 and with a KD at pH 7.0 and / or pH 7.4 that is more than 1.5-fold higher than that at pH 6.5. In certain embodiments, a pH sensitive Ab is provided that specifically binds to the VISTA-ECD protein with a Ko that is at least 1.5 fold, 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold, 300 fold, 500 fold, 1000 fold, or 5000 fold lower at pH 6.5 than at pH 7.0 (at a constant temperature, e.g., of 25°C or at 37°C). For example, in some cases an Ab binds to the VISTA-ECD protein with a KD that is at least 1.5 fold, 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold, 300 fold, 500 fold, 1000 fold, or 5000 fold less at pH 6.0, relative to pH 7.0 and / or pH 7.4 or higher (at a constant temperature, e.g., of 25°C or at 37°C).

[0097] In certain embodiments, an Ab specifically binds to a VISTA-ECD protein with a k0ff that is lower in acidic conditions relative to that in neutral, physiological, or alkaline conditions. In certain embodiments, an Ab is provided that binds to the VISTA-ECD protein in acidic conditions with a k0ff that is at least 1.5 fold, 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold, or 1000 fold lower at pH 6.5 than the k0ff at pH 7.0 and / or pH 7.4, as measured, e.g., at 25°C or at 37°C. In other words, the off-rate is slower at acidic pH than at neutral pH. For example, in some embodiments, an Ab specifically binds to a VISTA-ECD protein with a koff rate that is at least 1.5 fold, 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold or 1000 fold lower at pH 6.0, relative to pH 7.0 and / or pH 7.4, as measured, e.g., at 25°C or at 37°C. In certain embodiments, an Ab is provided that binds to the VISTA-ECD protein with a koff that is at least 1.5 fold, 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold or 1000 fold lower at pH 6.5 than the K0ff at pH 7.4, as measured, e.g., at 25°C or at 37°C. In some embodiments, an Ab specifically binds to a VISTA-ECD protein with a k0ff rate that is at least 1.5 fold, 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold or 1000 fold lower at pH 6.0, relative to pH 7.4, as measured, e.g., at 25°C or at 37°C. In certain embodiments, an Ab is provided that binds to the VISTA-ECD protein with a k0ff that is at least 1.5 fold, 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold or 1000 fold lower at pH 6.0-6.5 than the k0ff at pH 7.0-7.4, as measured, e.g., at 25°C or at 37°C.

[0098] In certain embodiments, an Ab that specifically binds to a VISTA-ECD protein with a kon that is higher in acidic conditions relative to neutral, physiological, or alkaline conditions. In certain embodiments, an Ab is provided that binds to a VISTA-ECD protein in acidic conditions with a that is at least 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold, or 1000 fold higher at pH 6.5 than the k0n at pH 7.0 and / or pH 7.4, as measured, e.g., at 25°C or at 37°C. For example, in some embodiments, an Ab specifically binds to aVISTA-ECD protein with a kon that is at least 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold or 1000 fold higher at pH 6.0 than at pH 7.0 and / or pH 7.4, as measured, e.g., at 25°C or at 37°C. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein at a pH at which at least one histidine residue, e.g., His 98 in SEQ ID NO: 1, is protonated. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein at a pH at which most histidine residues in the ECD are protonated, which is expected to be pH 6.5 or less, e.g., between pH 6.0 and pH 6.5.

[0099] Also encompassed herein are Abs that specifically bind to a VISTA-ECD protein with an affinity that is higher at neutral, physiological, or alkaline pH relative to acidic pH, provided that the affinity of binding at acidic pH remains high. For example, Abs may bind to the VISTA-ECD protein with a KD of 10_8M or less at both pH 6.5 and pH 7.0 even though the Abs bind with a KD that is at least 1.5 fold, 2 fold, 5 fold, 10 fold, 20 fold, 50 fold, 100 fold, 300 fold, 500 fold, 1000 fold lower at pH 7.0 than at pH 6.5.

[0100] Also encompassed herein are Abs that share one or more of the above properties of this section. The above properties, such as particular KD' S, koff S, kon s, specific epitopes are not to be treated in isolation. Thus, an Ab may bind to an epitope comprising one of the regions of SEQ ID NO:2 described above, and also may have pan binding or pH sensitive or pH selective binding properties as described above, as shown by one or more of the behaviors of its KD, Koff, Or Kon at different pH's.

[0101] In any of the above embodiments, the Ab may be, for example, a full length antibody (i.e., comprising a full length heavy chain (with or without C-terminal lysine) and a full length light chain), or an antigen binding fragment such as a Fab fragment, a Fab' fragment, (Fab')2fragment, an scFv fragment, an Fv fragment, or the Ab may be a chimeric, humanized, or human antibody, or the Ab may be a bispecific or multispecific antibody.

[0102] Determining how well an Ab binds to a VISTA-ECD protein at a given pH can be conducted using several different methods. For example, by surface plasmon resonance (SPR), such as by BIACORE® assays. An exemplary SPR assay comprises capturing one or several antibodies on a CM4 sensor chip with immobilized capture reagent (e .g., using Biacore® anti-human Fc capture kit, GE Healthcare catalog # BR- 1008-39, or Biacore® anti-mouse capture kit, GE Healthcare catalog #BR- 1008-39), and flowing VISTA antigen as analyte in a concentration series to determine binding kinetics and affinities in a running buffer with desired pH. In one embodiment, VISTA is injected at two to five concentrations in the range of 0.1 nM to 500 nM (e.g., 0.1 nM, 1 nM, 10 nM, 100 nM, 500 nM) with a flow rate of 30 uL / min, up to four minutes association time and up to ten minutes dissociation time. Between binding cycles, the capture surface is regenerated following the

[0103] manufacturer's instructions for the respective capture kit. All data is double-referenced using a reference flow cell and a blank injection. Data with simple 1 : 1 kinetics are fitted to a Langmuir binding model with mass transfer using the Biacore® T200 evaluation software. The SPR methods described in the Examples may also be used.

[0104] The affinity of an Ab for a VISTA ECD polypeptide may be determined using cells expressing a VISTA ECD polypeptide, PSGL-1 or heparan sulfate on their surface, which method comprises flow cytometry, and wherein binding of an Ab to cell bound VISTA-ECD is determined at a given pH, e.g., pH 6.5 or less. An exemplary flow cytometry assay comprises the following: 293T cells or other cells ectopically expressing hVISTA ECD are re-suspended in a buffer consisting of HBSS + 1% BSA adjusted to the desirable pH, e.g., pH 6.0 with MES or pH 7.4 with HEPES. Abs (e.g., human IgG) against hVISTA are serially diluted from approximately 20 μg / mLand incubated with the re-suspended cells for 30 minutes at 4 °C. Cells are then washed twice with the same buffers, maintaining the desired pH, e.g., pH at 6.0 or 7.4, and incubated with a fluorophore-conjugated secondary antibody that recognizes the primary antibody (e.g., human IgG) and is stable at reduced pH. Cells are then washed as before and acquired immediately, without fixation, on a BD Fortessa or other flow cytometer. The affinity of an Ab for a VISTA ECD polypeptide may be determined as described in the Examples.

[0105] In certain embodiments, Abs that bind to hVISTA ECD block binding of hVISTA to its binding partner (e.g., a VISTA receptor), e.g., on cells. Inhibition or blocking may be 100% or at least 99%, 95%, 90%, 85%, 80%, 75%, or 50%. In certain embodiments, an Ab binds to a VISTA-ECD protein at acidic pH, e.g., pH 6.5 or less, and inhibits binding of

[0106] VISTA to its binding partner by at least 50%, such as by at least 75%, 80%, 85%, 90%, 95%, or 100%). In certain embodiments, an Ab specifically binds to the VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 7.0. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 6.8. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 6.5. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 6.3. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 6.0. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 5.8. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 5.5. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 5.3. In certain embodiments, an Ab specifically binds to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH that is less than pH 5.0.

[0107] Certain Abs specifically bind to a VISTA-ECD protein and inhibits binding of

[0108] VISTA to its binding partner by at least 50% at a pH within a range of pH 5.0-pH 7.0. Certain Abs specifically bind to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH within a range of pH 5.0- pH 6.5. Certain Abs specifically bind to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH within a range of pH 5.0-pH 6.0. Certain Abs specifically bind to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH within a range of pH 5.5- pH 7.0. Certain Abs specifically bind to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH within a range of pH 5.5-pH 6.5. Certain Abs specifically bind to a VISTA-ECD protein and inhibits binding of VISTA to its binding partner by at least 50% at a pH within a range of pH 6.0-6.5. Inhibition of binding can be determined as described in the Examples.

[0109] A VISTA binding partner may be PSGL-1, such as human PSGL-1. Sequences of human PSGL-1 isoforms are provided as SEQ ID NOs: 3-10 herein. It may also be heparan sulfate proteoglycans, e.g., present on certain cells. Inhibition of binding to a VISTA binding partner can be determined by measuring the inhibition of binding of VISTA (or VISTA ECD or VISTA IgV domain or VISTA positive cells), to cells to which VISTA binds, e.g., T cells (e.g., CD4+T cells, CD8+ T cells, either activated or not), NK cells, or other cells to which VISTA binds, in the presence and absence of the antibody. An exemplary experiment that can be used to determine if an antibody inhibits the binding of VISTA to its binding partner or T cells expressing a binding partner is a flow cytometry assay, e.g., an assay that comprises the following: human peripheral blood mononuclear cells from donor blood, buffy coat, or leukopak are re-suspended in a buffer consisting of HBSS + 1% BSA adjusted to the desirable pH, e.g., pH 6.0 with MES or pH 7.4 with HEPES. The cells are then incubated for 30 minutes at 4 °C with 20 μg / mL recombinant chimeric protein consisting of hVISTA ECD fused to human IgGl Fc (VISTA-Fc) and with varying concentrations of candidate VISTA blocking antibodies or control antibodies. Cells are then washed twice in the same buffers, maintaining the desired pH, e.g., pH at 6.0 or 7.4, and incubated for another 30 minutes at 4 °C with a fluorophore-conjugated secondary antibody that recognizes VISTA-Fc, but not the candidate blocking antibodies or control antibodies, and is stable at reduced pH. Cells are then washed as before and acquired immediately, without fixation, on a BD Fortessa or other flow cytometer. Inhibition of binding can be determined, e.g., as described in the Examples.

[0110] In specific embodiments, the Abs described herein may trigger or enhance an immune response, such as an antigen-specific immune response. In certain embodiments, the Abs stimulate T cell activity, particularly at acidic pH such as is found in tumor

[0111] microenvironments. Stimulation of T cell activity can be measured, e.g., in a mixed lymphocyte reaction (MLR) or in an in vitro assay with an antigen presenting cell (natural or artificial) and T cells. Stimulation of T cell activity can also be measured using, e.g., the Jurkat assay described in the Examples.

[0112] In specific embodiments, the Abs described herein inhbit cell adhesion, which can be measured as described in the Examples.

[0113] Activity of anti-VISTA Abs can also be shown in monocyte assays, ADCC assays, and ADCP assays, particularly at acidic pH such as is found in tumor microenvironments. In certain embodiments, anti-VISTA Abs inhibit tumor growth in a tumor model, e.g., a human VISTA knock-in tumor model.

[0114] As shown in the Examples herein, recycling of an anti-VISTA Ab in the endosome such as to enhance the pharmacokinetic (PK) properties, i.e., half-life, of the antibody, requires the anti-VISTA antibody to bind to VISTA in acidic conditions. Thus, anti-VISTA Abs that bind at low pH to VISTA, e.g., a pH of 6.5 or lower, as further described herein, are also expected to have a longer acceptable half-life relative to a VISTA antibody that does not bind to VISTA at acidic pH Exemplary h VISTA-ECD binding Abs

[0115] Provided herein are Abs that bind preferentially to hVISTA (ECD) at acidic pH (e.g., in acidic conditions) relative to physiological pH or neutral pH.

[0116] In certain embodiments, an anti-hVISTA Ab comprises a heavy chain variable region ("VH") comprising VH CDRl, CDR2 and / or CDR3 of any of the anti-hVISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a VH comprising the VH CDRl, CDR2 and CDR3 of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a VH comprising VH CDRl, CDR2 and / or CDR3 of Pl-061029 or Pl-061015 or progeny thereof, such as Pl-061029, Pl-068757, Pl- 068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl- 068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl- 069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl-068736, Pl- 068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, PI -068761 E56N, Pl- 068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF. The VH CDRl, CDR2, and CDR3 of each of these species comprise amino acid positions 26-35 (VH CDRl), 50-66 (VH CDR2), and 99-110 (VH CDR3), of the VH sequences for each of the above antibody species provided in the sequence table below. The CDRs are also underlined and in bold on each of the VH sequences for the above antibody species provided in the Sequence Table below.

[0117] In certain embodiments, an anti-h VISTA Ab comprises a VH comprising VH CDRl, CDR2 and CDR3 of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a VH comprising VH CDRl, CDR2 and CDR3 of one of Pl- 061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl- 068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl- 069065, Pl-069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl- 061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, Pl- 068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fE, Pl-068761_E55A_E100fE, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761_E32Y, Pl-

[0118] 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl-

[0119] 068767_D52N_E100fE, Pl-068767_E100fF, or Pl-068767_E30D_E100fF. The VL CDRl, CDR2, and CDR3 of each of these species comprise amino acid positions 24-35 (VL CDRl), 51-57 (VL CDR2), and 90-98 (VL CDR3), of the VL sequences for each of the above antibody species provided in the Sequence Table below. The CDRs are also underlined and in bold on each of those sequences. In certain embodiments, an anti-h VISTA Ab comprises a VH comprising VH CDRl, CDR2 and / or CDR3 of any of the anti-h VISTA Abs provided herein and a VL comprising CDRl, CDR2 and / or CDR3 of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a VH comprising VH CDRl, CDR2 and CDR3 of any of the anti-h VISTA Abs provided herein and a VLcomprising CDRl, CDR2 and CDR3 of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti- hVISTA Ab comprises a VH comprising VH CDRl, CDR2 and / or CDR3 of Pl-061029 or Pl-061015 or progeny thereof, such as Pl-061029, Pl-068757, Pl-068759, Pl-068761, Pl- 068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl-068773, Pl-068775, Pl- 069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl-069069, Pl-069071, Pl-

[0120] 069073, Pl-069075, Pl-069077, Pl-061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761_E55A, P1-068761 H100G, P1-068761 E56N, P1-068761 E55A E56N, P1-068761 E30D, Pl- 068761 E30D E55A, PI -068761 E56N H100G, P1-068761 E30D H100G, Pl- 068761_E30D_E56N, PI -06876 l ElOOfF, Pl-068761_E55A_E100fE, Pl-

[0121] 068761_H100G_E100fE, Pl-068761_E30D_E100fE, Pl-068761_E56N_E100fF, Pl- 068761_E32Y, P1-068761_E32Y_E55A, PI -068761_E32Y_E56N, Pl- 068761 E30D E32Y, PI -068761 E32Y H100G, Pl-068761_E32Y_E100fF, Pl- 068767_D52N_D102V, P1-068767_D52N, P1-068767_D52N_E55A, Pl- 068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767 E30D D102V, P1-068767 E30D, P1-068767 E30D E55A, Pl- 068767_E100fE_D102V, Pl-068767_E55A_E100fE, Pl-068767_D52N_E100fE, Pl- 068767_E100fF, or Pl-068767_E30D_E100fF and a VL comprising VL CDRl, CDR2 and CDR3 of Pl-061029 or Pl-061015 or progeny thereof, such as Pl-061029, Pl-068757, Pl- 068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl- 068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl- 069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl-068736, Pl- 068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, PI -068761 E56N, Pl- 068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl-

[0122] 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF.

[0123] In some embodiments, an anti-h VISTA Ab may comprise:

[0124] (a) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 061029 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -061029;

[0125] (b) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 061015 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-061015;

[0126] (c) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0127] 068757 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068757;

[0128] (d) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068759 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068759;

[0129] (e) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068761 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068761;

[0130] (f) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068763 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068763;

[0131] (g) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068765 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068765;

[0132] (h) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0133] 068767 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068767;

[0134] (i) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0135] 068769 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068769;

[0136] (j) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068771 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068771; (k) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0137] 068773 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068773;

[0138] (1) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0139] 068775 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068775;

[0140] (m)a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0141] 069059 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -069059;

[0142] (n) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0143] 069061 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-069061;

[0144] [o) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0145] 069063 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -069063;

[0146] 'p) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0147] 069065 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-069065;

[0148] Iq) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0149] 069067 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -069067;

[0150] j) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0151] 069069 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -069069;

[0152] 's) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0153] 069071 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -069071;

[0154] ;t) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0155] 069073 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -069073;

[0156] u) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0157] 069075 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-069075;

[0158] V) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0159] 069077 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-069077;

[0160] V) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of

[0161] Pl-068736 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068736; x) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0162] 068738 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068738;

[0163] y) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-

[0164] 068740 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068740; (z) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068742 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068742;

[0165] (aa) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0166] CDR3 of Pl-068744 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068744;

[0167] (bb) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0168] CDR3 of Pl-068746 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068746;

[0169] (cc) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0170] CDR3 of PI -068748 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-

[0171] 068748;

[0172] (dd) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0173] CDR3 of Pl-068750 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068750;

[0174] (ee) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0175] CDR3 of PI -068752 and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068752;

[0176] (ff) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068754 and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068754;

[0177] (gg) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0178] CDR3 of P1-068761 E55A and a VL comprising the VL CDRl, CDR2 and CDR3 of P1-068761_E55A;

[0179] (hh) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0180] CDR3 of P1-068761 H100G and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068761_H100G;

[0181] (ii) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of PI -068761 E56N and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068761_E56N; (jj) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068761 E55A E56N and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068761_E55A_E56N;

[0182] (kk) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0183] CDR3 of P1-068761 E30D and a VL comprising the VL CDRl, CDR2 and CDR3 of

[0184] P1-068761 E30D;

[0185] (11) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068761 E30D E55A and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068761_E30D_E55A;

[0186] (mm) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0187] CDR3 of PI -068761 E56N H100G and a VL comprising the VL CDRl, CDR2 and CDR3 of PI -068761 E56N H100G;

[0188] (nn) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0189] CDR3 of P1-068761 E30D H100G and a VL comprising the VL CDRl, CDR2 and CDR3 of P1-068761 E30D H100G;

[0190] (oo) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0191] CDR3 of P1-068761 E30D E56N and a VL comprising the VL CDRl, CDR2 and CDR3 of P1-068761 E30D E56N;

[0192] (pp) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0193] CDR3 of PI -06876 l ElOOfF and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068761_E100ff;

[0194] (qq) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0195] CDR3 of Pl-068761_E55A_E100fF and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068761_E55A_E100fF;

[0196] (rr) a VH comprising the amino acid sequence of the VH CDRl , CDR2 and CDR3 of P 1 -

[0197] 068761_H100G_E100fE and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068761_H100G_E100fF;

[0198] (ss)a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068761_E30D_E100fF and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068761_E30D_E100fE; (tt) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 06876 l_E56N_E100fF and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068761_E56N_E100fF;

[0199] (uu) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0200] CDR3 of PI -068761 E32Y and a VL comprising the VL CDRl, CDR2 and CDR3 of

[0201] PI -068761_E32Y;

[0202] (vv) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0203] CDR3 of P1-068761 E32Y E55A and a VL comprising the VL CDRl, CDR2 and

[0204] CDR3 of P1-068761 E32Y E55A;

[0205] (ww) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0206] CDR3 of P1-068761 E32Y E56N and a VL comprising the VL CDRl, CDR2 and

[0207] CDR3 of PI -068761_E32Y_E56N;

[0208] (xx) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0209] CDR3 of P1-068761 E30D E32Y and a VL comprising the VL CDRl, CDR2 and CDR3 of P1-068761 E30D E32Y;

[0210] (yy) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0211] CDR3 of PI -068761 E32Y H100G and a VL comprising the VL CDRl, CDR2 and

[0212] CDR3 of PI -068761 E32Y H100G;

[0213] (zz) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0214] CDR3 of PI -06876 l_E32Y_E100fF and a VL comprising the VL CDRl, CDR2 and

[0215] CDR3 of Pl-068761_E32Y_E100fE;

[0216] (aaa) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0217] CDR3 of P1-068767 D52N D102V and a VL comprising the VL CDRl, CDR2 and

[0218] CDR3 of P1-068767_D52N_D102V;

[0219] (bbb) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0220] CDR3 of P1-068767 D52N and a VL comprising the VL CDRl, CDR2 and CDR3 of

[0221] P1-068767_D52N;

[0222] (ccc) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0223] CDR3 of P1-068767 D52N E55A and a VL comprising the VL CDRl, CDR2 and CDR3 of P1-068767_D52N_E55A; (ddd) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0224] CDR3 of P1-068767 E55A D102V and a VL comprising the VL CDRl, CDR2 and

[0225] CDR3 of P1-068767_E55A_D102V;

[0226] (eee) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0227] CDR3 of P1-068767 D102V and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068767_D102V;

[0228] (fff) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0229] CDR3 of P1-068767 E55A and a VL comprising the VL CDRl, CDR2 and CDR3 of

[0230] P1-068767_E55A;

[0231] (ggg) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0232] CDR3 of P1-068767 E30D D52N and a VL comprising the VL CDRl, CDR2 and CDR3 of P1-068767_E30D_D52N;

[0233] (hhh) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0234] CDR3 of P1-068767 E30D D102V and a VL comprising the VL CDRl, CDR2 and CDR3 of P1-068767 E30D D102V;

[0235] (iii)a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068767 E30D and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl- 068767_E30D;

[0236] (jjj)a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl- 068767 E30D E55A and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-

[0237] 068767_E30D_E55A;

[0238] (kkk) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0239] CDR3 of Pl-068767_E100fF_D102V and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068767_E100fF_D102V;

[0240] (111) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of

[0241] Pl-068767_E55A_E100fE and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068767_E55A_E100fE;

[0242] (mmm) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0243] CDR3 of Pl-068767_D52N_E100fE and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068767_D52N_E100fF; (nnn) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and CDR3 of Pl-068767_E100fF and a VL comprising the VL CDRl, CDR2 and CDR3 of Pl-068767_E100ff;

[0244] (ooo) a VH comprising the amino acid sequence of the VH CDRl, CDR2 and

[0245] CDR3 of Pl-068767_E30D_E100fF and a VL comprising the VL CDRl, CDR2 and

[0246] CDR3 of Pl-068767_E30D_E100fF.

[0247] Again, the Sequence Table below provides the heavy and light chain variable region sequences and full length heavy and light chain sequences of the antibodies listed above with an IgGl .3 heavy chain constant region (unless a different HC constant region is noted in the table) and notes the locations of their VH CDRl, CDR2, and CDR3 and VL CDRl, CDR2, and CDR3 by amino acid residue and with holding and underlining of the CDRs in each VH and VL sequence. Thus, for example, VH CDRl of PI -061029 comprises amino acids 26-35 of SEQ ID NO: 67, while VH CDR2 comprises amino acids 50-66 of SEQ ID NO: 67, and VH CDR3 comprises amino acids 99-110 of SEQ ID NO: 67, and so forth, as noted by the bolded and underlined amino acids of SEQ ID NO: 67 shown in the Sequence Table.

[0248] In certain embodiments, an anti-h VISTA Ab comprises a VH comprising the amino acid sequence of the VH of any of the anti-h VISTA Abs provided herein. The individual VH sequences for particular antibody species provided herein are listed in the Sequence Table. In certain embodiments, an anti-h VISTA Ab comprises a VH comprising the amino acid sequence of the VH of PI -061029 or Pl-061015 or progeny thereof, such as PI -061029, Pl- 068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl- 068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl- 069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl- 068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761_E55A, PI -068761 H100G, P1-068761_E56N, Pl- 068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fE, Pl-068761_E55A_E100fE, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF. In certain embodiments, an anti-h VISTA Ab comprises a VH CDRl, CDR2, and CDR3 comprising the amino acid sequences of the VH CDRs of any of the anti-h VISTA Abs provided herein and comprises a VH that is 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% identical to the VH of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a VH comprising an amino acid sequence that is 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% identical to the amino acid sequence of the VH of PI -061029, PI -068757, Pl- 068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl- 068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl- 069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl-068736, Pl- 068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, PI -068761 E56N, Pl- 068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl-

[0249] 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl-

[0250] 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF. In certain embodiments, an anti-h VISTA Ab comprises a VH consisting of the amino acid sequence of the VH of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti- hVISTA Ab comprises a VH that consists of the amino acid sequence of the VH of Pl- 061029 or Pl-061015 or progeny thereof, such as Pl-061029, Pl-068757, Pl-068759, Pl- 068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl-068773, Pl- 068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl-069069, Pl- 069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl-068736, Pl-068738, Pl- 068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761_E55A, PI -068761 H100G, PI -068761_E56N, P1-068761_E55A_E56N, Pl- 068761 E30D, P1-068761 E30D E55A, PI -068761 E56N H100G, Pl- 068761 E30D H100G, P1-068761 E30D E56N, Pl-068761_E100fE, Pl-

[0251] 068761_E55A_E100fF, Pl-068761_H100G_E100fE, Pl-068761_E30D_E100fF, Pl- 06876 l_E56N_E100fF, P1-068761_E32Y, P1-068761_E32Y_E55A, Pl- 068761 E32Y E56N, P1-068761 E30D E32Y, PI -068761 E32Y H100G, Pl- 06876 l_E32Y_E100fF, P1-068767_D52N_D102V, P1-068767_D52N, Pl- 068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, Pl- 068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fE, Pl-068767_E100fF, or Pl-068767_E30D_E100fF.

[0252] In certain embodiments, an anti-h VISTA Ab comprises a VL comprising the amino acid sequence of the VL of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a VL comprising the amino acid sequence of the VL of PI -061029 or Pl-061015 or progeny thereof, such as PI -061029, Pl-068757, Pl- 068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl- 068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl- 069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl-068736, Pl- 068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, PI -068761 E56N, Pl- 068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fE, Pl-068761_E55A_E100fE, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF. In certain embodiments, an anti-h VISTA Ab comprises a VL CDRl, CDR2, and CDR3 comprising the amino acid sequences of the VL CDRs of any of the anti-h VISTA Abs provided herein and comprises a VL that is 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% identical to the VL of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a VL comprising an amino acid sequence that is 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% identical to the amino acid sequence of the VL of Pl-061029, Pl-068757, Pl- 068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl- 068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl- 069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl-068736, Pl- 068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761_E55A, PI -068761 H100G, PI -068761_E56N, Pl- 068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl-

[0253] 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF. In certain embodiments, an anti-h VISTA Ab comprises a VL consisting of the amino acid sequence of the VL of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti- hVISTA Ab comprises a VL that consists of the amino acid sequence of the VL of Pl- 061029 or Pl-061015 or progeny thereof, such as Pl-061029, Pl-068757, Pl-068759, Pl- 068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl-068773, Pl- 068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl-069069, Pl- 069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl-068736, Pl-068738, Pl- 068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761_E55A, PI -068761 H100G, PI -068761_E56N, P1-068761_E55A_E56N, Pl- 068761 E30D, P1-068761 E30D E55A, PI -068761 E56N H100G, Pl- 068761 E30D H100G, P1-068761 E30D E56N, Pl-068761_E100fE, Pl- 068761_E55A_E100fF, Pl-068761_H100G_E100fE, Pl-068761_E30D_E100fF, Pl- 06876 l_E56N_E100fF, P1-068761_E32Y, P1-068761_E32Y_E55A, Pl- 068761 E32Y E56N, P1-068761 E30D E32Y, PI -068761 E32Y H100G, Pl- 06876 l_E32Y_E100fF, P1-068767_D52N_D102V, P1-068767_D52N, Pl-

[0254] 068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, Pl- 068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fE, Pl-068767_E100fF, or Pl-068767_E30D_E100fF.

[0255] In certain embodiments, an anti-h VISTA Ab comprises a VH comprising the amino acid sequence of the VH of any of the anti-h VISTA Abs provided herein and comprises a VL comprising the amino acid sequence of the VL of any of the anti-h VISTA Abs provided herein. In certain of these embodiments, an anti-h VISTA Ab comprises a VH comprising the amino acid sequence of the VH of PI -061029 or Pl-061015 or progeny thereof, such as Pl- 061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl- 068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl- 069065, Pl-069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl- 061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, Pl- 068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl-

[0256] 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF; and a VL comprising the amino acid sequence of the VL of PI -061029 or Pl-061015. In certain embodiments, an anti-h VISTA Ab comprises a VH and a VL comprising the amino acid sequences of the VH and VL of PI -061029 or Pl-061015 or progeny thereof, such as Pl- 061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl- 068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl- 069065, Pl-069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl- 061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, Pl- 068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fE, Pl-068761_E55A_E100fE, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fE_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fE, Pl-068767_E100fF, or Pl-068767_E30D_E100fF.

[0257] In certain embodiments, an anti-hVISTA Ab comprises a VH CDR1, CDR2, and CDR3 comprising the amino acid sequences of the VH CDRs of any of the anti-h VISTA Abs provided herein as well as a VL CDR1, CDR2, and CDR3 comprising the amino acid sequences of the VL CDRs of any of the anti-h VISTA Abs provided herein, and also comprises a VH and a VL that are each 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% identical to the corresponding VH and VL of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises all 6 CDRs of an anti-h VISTA Ab provided herein and also comprises VH and VL amino acid sequences that are each 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% identical to the corresponding VH and VL of the anti-h VIST A Ab, such as the VH and VL of PI -061029 or P 1-061015 or progeny thereof, such as PI -061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl- 068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl- 069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl-061015, Pl- 068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761_E55A, PI -068761 H100G, P1-068761_E56N, Pl- 068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl-

[0258] 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl-

[0259] 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF. In certain embodiments, an anti-h VISTA Ab comprises a VH and a VL consisting of the amino acid sequence of the VH and VL of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a VH and a VL that each consist of the amino acid sequences of the VH and VL of PI -061029 or Pl-061015 or progeny thereof, such as Pl-061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl- 068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl- 069065, Pl-069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl- 061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, Pl- 068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF.

[0260] An anti-h VISTA Ab may comprise:

[0261] (a) a VH comprising the amino acid sequence of the VH of PI -061029 and a VL

[0262] comprising the amino acid sequence of the VL of PI -061029;

[0263] (b) a VH comprising the amino acid sequence of the VH of Pl-061015 and a VL

[0264] comprising the amino acid sequence of the VL of Pl-061015;

[0265] (c) a VH comprising the amino acid sequence of the VH of PI -068757 and a VL

[0266] comprising the amino acid sequence of the VL of PI -068757;

[0267] (d) a VH comprising the amino acid sequence of the VH of PI -068759 and a VL

[0268] comprising the amino acid sequence of the VL of PI -068759;

[0269] (e) a VH comprising the amino acid sequence of the VH of Pl-068761 and a VL

[0270] comprising the amino acid sequence of the VL of Pl-068761;

[0271] (f) a VH comprising the amino acid sequence of the VH of PI -068763 and a VL

[0272] comprising the amino acid sequence of the VL of PI -068763;

[0273] (g) a VH comprising the amino acid sequence of the VH of PI -068765 and a VL

[0274] comprising the amino acid sequence of the VL of Pl-068765;

[0275] (h) a VH comprising the amino acid sequence of the VH of Pl-068767 and a VL

[0276] comprising the amino acid sequence of the VL of Pl-068767; (i) a VH comprising the amino acid sequence of the VH of PI -068769 and a VL comprising the amino acid sequence of the VL of PI -068769;

[0277] (j) a VH comprising the amino acid sequence of the VH of Pl-068771 and a VL comprising the amino acid sequence of the VL of Pl-068771;

[0278] (k) a VH comprising the amino acid sequence of the VH of PI -068773 and a VL comprising the amino acid sequence of the VL of -068773;

[0279] (1) a VH comprising the amino acid sequence of the VH of PI -068775 and a VL comprising the amino acid sequence of the VL of Pl-068775;

[0280] (m)a VH comprising the amino acid sequence of the VH of Pl-069059 and a VL comprising the amino acid sequence of the VL of Pl-069059;

[0281] (n) a VH comprising the amino acid sequence of the VH of PI -069061 and a VL comprising the amino acid sequence of the VL of PI -069061;

[0282] (o) a VH comprising the amino acid sequence of the VH of PI -069063 and a VL comprising the amino acid sequence of the VL of PI -069063;

[0283] (p) a VH comprising the amino acid sequence of the VH of PI -069065 and a VL comprising the amino acid sequence of the VL of Pl-069065;

[0284] (q) a VH comprising the amino acid sequence of the VH of PI -069067 and a VL comprising the amino acid sequence of the VL of PI -069067;

[0285] (r) a VH comprising the amino acid sequence of the VH of PI -069069 and a VL comprising the amino acid sequence of the VL of PI -069069;

[0286] (s) a VH comprising the amino acid sequence of the VH of PI -069071 and a VL comprising the amino acid sequence of the VL of PI -069071;

[0287] (t) a VH comprising the amino acid sequence of the VH of PI -069073 and a VL comprising the amino acid sequence of the VL of PI -069073;

[0288] (u) a VH comprising the amino acid sequence of the VH of PI -069075 and a VL comprising the amino acid sequence of the VL of Pl-069075;

[0289] (v) a VH comprising the amino acid sequence of the VH of PI -069077 and a VL comprising the amino acid sequence of the VL of PI -069077;

[0290] (w) a VH comprising the amino acid sequence of the VH of PI -068736 and a VL comprising the amino acid sequence of the VL of Pl-068736; (x) a VH comprising the amino acid sequence of the VH of PI -068738 and a VL comprising the amino acid sequence of the VL of PI -068738;

[0291] (y) a VH comprising the amino acid sequence of the VH of PI -068740 and a VL

[0292] comprising the amino acid sequence of the VL of PI -068740;

[0293] (z) a VH comprising the amino acid sequence of the VH of PI -068742 and a VL

[0294] comprising the amino acid sequence of the VL of PI -068742;

[0295] (aa) a VH comprising the amino acid sequence of the VH of PI -068744 and a VL comprising the amino acid sequence of the VL of PI -068744;

[0296] (bb) a VH comprising the amino acid sequence of the VH f PI -068746 and a VL comprising the amino acid sequence of the VL of PI -068746;

[0297] (cc) a VH comprising the amino acid sequence of the VH of PI -068748 and a VL comprising the amino acid sequence of the VL of PI -068748;

[0298] (dd) a VH comprising the amino acid sequence of the VH of PI -068750 and a VL comprising the amino acid sequence of the VL of PI -068750;

[0299] (ee) a VH comprising the amino acid sequence of the VH of PI -068752 and a VL comprising the amino acid sequence of the VL of PI -068752;

[0300] (ff) a VH comprising the amino acid sequence of the VH of PI -068754 and a VL

[0301] comprising the amino acid sequence of the VL of PI -068754;

[0302] (gg) a VH comprising the amino acid sequence of the VH of P1-068761 E55A and a VL comprising the amino acid sequence of the VL of P1-068761 E55A;

[0303] (hh) a VH comprising the amino acid sequence of the VH of PI -068761 H100G and a VL comprising the amino acid sequence of the VL of P1-068761 H100G; (ii) a VH comprising the amino acid sequence of the VH of P1-068761 E56N and a VL comprising the amino acid sequence of the VL of P1-068761 E56N;

[0304] (jj) a VH comprising the amino acid sequence of the VH of P1-068761 E55A E56N and a VL comprising the amino acid sequence of the VL of P1-068761 E55A E56N; (kk) a VH comprising the amino acid sequence of the VH of P1-068761 E30D and a VL comprising the amino acid sequence of the VL of P1-068761 E30D;

[0305] (11) a VH comprising the amino acid sequence of the VH of P1-068761 E30D E55A and a VL comprising the amino acid sequence of the VL of P1-068761 E30D E55A; (mm) a VH comprising the amino acid sequence of the VH of Pl-

[0306] 068761 E56N H100G and a VL comprising the amino acid sequence of the VL of

[0307] PI -068761 E56N H100G;

[0308] (nn) a VH comprising the amino acid sequence of the VH of Pl- 068761 E30D H100G and a VL comprising the amino acid sequence of the VL of

[0309] P1-068761 E30D H100G;

[0310] (oo) a VH comprising the amino acid sequence of the VH of Pl-

[0311] 068761 E30D E56N and a VL comprising the amino acid sequence of the VL of Pl-

[0312] 068761_E30D_E56N;

[0313] (pp) a VH comprising the amino acid sequence of the VH of PI -06876 l ElOOfF and a VL comprising the amino acid sequence of the VL of Pl-068761_E100fF; (qq) a VH comprising the amino acid sequence of the VH of Pl-

[0314] 068761_E55A_E100fF and a VL comprising the amino acid sequence of the VL of Pl-068761_E55A_E100fF;

[0315] (rr) a VH comprising the amino acid sequence of the VH of Pl-068761_H100G_E100fF and a VL comprising the amino acid sequence of the VL of Pl- 068761_H100G_E100fE;

[0316] (ss)a VH comprising the amino acid sequence of the VH of Pl-068761_E30D_E100fF and a VL comprising the amino acid sequence of the VL of Pl- 068761_E30D_E100fE;

[0317] (tt) a VH comprising the amino acid sequence of the VH of PI -06876 l_E56N_E100fF and a VL comprising the amino acid sequence of the VL of Pl- 068761_E56N_E100fE;

[0318] (uu) a VH comprising the amino acid sequence of the VH of PI -068761 E32Y and a VL comprising the amino acid sequence of the VL of PI -068761 E32Y;

[0319] (vv) a VH comprising the amino acid sequence of the VH of Pl-

[0320] 068761 E32Y E55A and a VL comprising the amino acid sequence of the VL of Pl- 068761_E32Y_E55A; (ww) a VH comprising the amino acid sequence of the VH of Pl-

[0321] 068761 E32Y E56N and a VL comprising the amino acid sequence of the VL of Pl-

[0322] 068761_E32Y_E56N;

[0323] (xx) a VH comprising the amino acid sequence of the VH of Pl- 068761 E30D E32Y and a VL comprising the amino acid sequence of the VL of Pl-

[0324] 068761_E30D_E32Y;

[0325] (yy) a VH comprising the amino acid sequence of the VH of Pl-

[0326] 068761 E32Y H100G and a VL comprising the amino acid sequence of the VL of

[0327] PI -068761 E32Y H100G;

[0328] (zz) a VH comprising the amino acid sequence of the VH of Pl-

[0329] 06876 l_E32Y_E100fF and a VL comprising the amino acid sequence of the VL of

[0330] Pl-068761_E32Y_E100fE;

[0331] (aaa) a VH comprising the amino acid sequence of the VH of Pl-

[0332] 068767 D52N D102V and a VL comprising the amino acid sequence of the VL of P1-068767_D52N_D102V;

[0333] (bbb) a VH comprising the amino acid sequence of the VH of P1-068767 D52N and a VL comprising the amino acid sequence of the VL of P1-068767 D52N;

[0334] (ccc) a VH comprising the amino acid sequence of the VH of Pl-

[0335] 068767 D52N E55A and a VL comprising the amino acid sequence of the VL of Pl- 068767_D52N_E55A;

[0336] (ddd) a VH comprising the amino acid sequence of the VH of Pl-

[0337] 068767 E55A D102V and a VL comprising the amino acid sequence of the VL of

[0338] P 1 -068767_E55 A_D 102 V;

[0339] (eee) a VH comprising the amino acid sequence of the VH of P1-068767 D102V and a VL comprising the amino acid sequence of the VL of P1-068767 D102V;

[0340] (fff) a VH comprising the amino acid sequence of the VH of P1-068767 E55A and a VL comprising the amino acid sequence of the VL of P1-068767 E55A;

[0341] (ggg) a VH comprising the amino acid sequence of the VH of Pl-

[0342] 068767 E30D D52N and a VL comprising the amino acid sequence of the VL of Pl- 068767_E30D_D52N; (hhh) a VH comprising the amino acid sequence of the VH of Pl-

[0343] 068767 E30D D102V and a VL comprising the amino acid sequence of the VL of

[0344] P 1 -068767_E30D_D 102 V;

[0345] (iii) a VH comprising the amino acid sequence of the VH of P1-068767 E30D and a VL comprising the amino acid sequence of the VL of P1-068767 E30D;

[0346] (jjj)a VH comprising the amino acid sequence of the VH of P1-068767 E30D E55A and a VL comprising the amino acid sequence of the VL of P1-068767 E30D E55A; (kkk) a VH comprising the amino acid sequence of the VH of Pl-

[0347] 068767_E100fF_D102V and a VL comprising the amino acid sequence of the VL of Pl-068767_E100fF_D102V;

[0348] (111) a VH comprising the amino acid sequence of the VH of Pl-068767_E55A_E100fF and a VL comprising the amino acid sequence of the VL of Pl-

[0349] 068767_E55A_E100fF;

[0350] (mmm) a VH comprising the amino acid sequence of the VH of Pl- 068767_D52N_E100fF and a VL comprising the amino acid sequence of the VL of

[0351] Pl-068767_D52N_E100fF;

[0352] (nnn) a VH comprising the amino acid sequence of the VH of Pl-068767_E100fF and a VL comprising the amino acid sequence of the VL of Pl-068767_E100fF; or (ooo) a VH comprising the amino acid sequence of the VH of Pl- 068767_E30D_E100fF and a VL comprising the amino acid sequence of the VL of

[0353] Pl-068767_E30D_E100fF.

[0354] An anti-h VISTA Ab may comprise:

[0355] (a) a VH comprising the VH CDRs of the VH of PI -061029 and a VL comprising the VL CDRs of PI -061029 and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -061029;

[0356] (b) a VH comprising the VH CDRs of the VH of Pl-061015 and a VL comprising the VL CDRs of Pl-061015 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-061015;

[0357] (c) a VH comprising the VH CDRs of the VH of Pl-068757 and a VL comprising the VL CDRs of Pl-068757 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068757;

[0358] (d) a VH comprising the VH CDRs of the VH of Pl-068759 and a VL comprising the VL CDRs of Pl-068759 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068759;

[0359] (e) a VH comprising the VH CDRs of the VH of Pl-068761 and a VL comprising the VL CDRs of Pl-068761 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068761;

[0360] (f) a VH comprising the VH CDRs of the VH of Pl-068763 and a VL comprising the VL CDRs of Pl-068763 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068763;

[0361] (g) a VH comprising the VH CDRs of the VH of Pl-068765 and a VL comprising the VL CDRs of Pl-068765 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068765;

[0362] (h) a VH comprising the VH CDRs of the VH of Pl-068767 and a VL comprising the VL CDRs of Pl-068767 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068767;

[0363] (i) a VH comprising the VH CDRs of the VH of Pl-068769 and a VL comprising the VL CDRs of Pl-068769 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068769; (j) a VH comprising the VH CDRs of the VH of Pl-068771 and a VL comprising the VL CDRs of Pl-068771 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068771;

[0364] (k) a VH comprising the VH CDRs of the VH of Pl-068773 and a VL comprising the VL CDRs of Pl-068773 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068773;

[0365] (1) a VH comprising the VH CDRs of the VH of Pl-068775 and a VL comprising the VL CDRs of Pl-068775 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068775;

[0366] (m)a VH comprising the VH CDRs of the VH of Pl-069059 and a VL comprising the VL CDRs of Pl-069059 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-069059;

[0367] (n) a VH comprising the VH CDRs of the VH of PI -069061 and a VL comprising the VL CDRs of PI -069061 and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -069061;

[0368] (o) a VH comprising the VH CDRs of the VH of PI -069063 and a VL comprising the VL CDRs of PI -069063 and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -069063;

[0369] (p) a VH comprising the VH CDRs of the VH of Pl-069065 and a VL comprising the VL CDRs of Pl-069065 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-069065;

[0370] (q) a VH comprising the VH CDRs of the VH of PI -069067 and a VL comprising the VL CDRs of PI -069067 and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -069067;

[0371] (r) a VH comprising the VH CDRs of the VH of PI -069069 and a VL comprising the VL CDRs of PI -069069 and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -069069;

[0372] (s) a VH comprising the VH CDRs of the VH of PI -069071 and a VL comprising the VL CDRs of PI -069071 and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -069071;

[0373] (t) a VH comprising the VH CDRs of the VH of PI -069073 and a VL comprising the VL CDRs of PI -069073 and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -069073;

[0374] (u) a VH comprising the VH CDRs of the VH of Pl-069075 and a VL comprising the VL CDRs of Pl-069075 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-069075;

[0375] (v) a VH comprising the VH CDRs of the VH of PI -069077 and a VL comprising the VL CDRs of PI -069077 and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -069077;

[0376] (w) a VH comprising the VH CDRs of the VH of Pl-068736 and a VL comprising the VL CDRs of Pl-068736 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068736;

[0377] (x) a VH comprising the VH CDRs of the VH of Pl-068738 and a VL comprising the VL CDRs of Pl-068738 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068738; (y) a VH comprising the VH CDRs of the VH of Pl-068740 and a VL comprising the VL CDRs of Pl-068740 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068740;

[0378] (z) a VH comprising the VH CDRs of the VH of Pl-068742 and a VL comprising the VL

[0379] CDRs of Pl-068742 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068742;

[0380] (aa) a VH comprising the VH CDRs of the VH of Pl-068744 and a VL comprising the VL CDRs of Pl-068744 and VH and VL amino acid sequences that are at least

[0381] 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% identical to the VH and VL of Pl-068744; (bb) a VH comprising the VH CDRs of the VH of Pl-068746 and a VL comprising the VL CDRs of Pl-068746 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068746; (cc) a VH comprising the VH CDRs of the VH of Pl-068748 and a VL comprising the VL CDRs of Pl-068748 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068748;

[0382] (dd) a VH comprising the VH CDRs of the VH of Pl-068750 and a VL comprising the VL CDRs of Pl-068750 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068750; (ee) a VH comprising the VH CDRs of the VH of Pl-068752 and a VL comprising the VL CDRs of Pl-068752 and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068752; (ff) a VH comprising the VH CDRs of the VH of Pl-068754 and a VL comprising the VL CDRs of Pl-068754 and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least

[0383] 97%, at least 98%, or at least 99% identical to the VH and VL of PI -068754;

[0384] (gg) a VH comprising the VH CDRs of the VH of P1-068761 E55A and a VL comprising the VL CDRs of P1-068761 E55A and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least

[0385] 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the VH and

[0386] VL of P1-068761_E55A;

[0387] (hh) a VH comprising the VH CDRs of the VH of PI -068761 H100G and a VL comprising the VL CDRs of PI -068761 H100G and VH and VL amino acid sequences that are 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% identical to the

[0388] VH and VL of P1-068761 H100G;

[0389] (ii) a VH comprising the VH CDRs of the VH of P1-068761 E56N and a VL comprising the VL CDRs of P1-068761 E56N and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least

[0390] 96%, at least 97%, at least 98%, or at least 99% identical to the VH and VL of Pl-

[0391] 068761_E56N;

[0392] (jj) a VH comprising the VH CDRs of the VH of P1-068761 E55A E56N and a VL comprising the VL CDRs of P1-068761 E55A E56N and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068761_E55A_E56N;

[0393] (kk) a VH comprising the VH CDRs of the VH of P1-068761 E30D and a VL comprising the VL CDRs of P1-068761 E30D and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least

[0394] 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the VH and VL of P1-068761 E30D;

[0395] (11) a VH comprising the VH CDRs of the VH of P1-068761 E30D E55A and a VL comprising the VL CDRs of P1-068761 E30D E55A and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068761_E30D_E55A;

[0396] (mm) a VH comprising the VH CDRs of the VH of P1-068761 E56N H100G and a VL comprising the VL CDRs of P1-068761 E56N H100G and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068761 E56N H100G;

[0397] (nn) a VH comprising the VH CDRs of the VH of PI -068761 E30D H100G and a

[0398] VL comprising the VL CDRs of P1-068761 E30D H100G and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068761 E30D H100G;

[0399] (oo) a VH comprising the VH CDRs of the VH of P1-068761 E30D E56N and a

[0400] VL comprising the VL CDRs of P1-068761 E30D E56N and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068761 E30D E56N;

[0401] (pp) a VH comprising the VH CDRs of the VH of PI -06876 l_E100fF and a VL comprising the VL CDRs of PI -06876 l_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068761_E100fF;

[0402] (qq) a VH comprising the VH CDRs of the VH of Pl-068761_E55A_E100fF and a

[0403] VL comprising the VL CDRs of Pl-068761_E55A_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068761_E55A_E100fF;

[0404] (rr) a VH comprising the VH CDRs of the VH of PI -06876 l HlOOG ElOOfF and a VL comprising the VL CDRs of Pl-068761_H100G_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068761_H100G_E100ff ;

[0405] (ss)a VH comprising the VH CDRs of the VH of Pl-068761_E30D_E100fF and a VL comprising the VL CDRs of Pl-068761_E30D_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068761_E30D_E100fF;

[0406] (tt) a VH comprising the VH CDRs of the VH of Pl-068761_E56N_E100fF and a VL comprising the VL CDRs of Pl-068761_E56N_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068761_E56N_E100fF;

[0407] (uu) a VH comprising the VH CDRs of the VH of PI -068761 E32Y and a VL comprising the VL CDRs of PI -068761 E32Y and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least

[0408] 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the VH and VL of PI -068761 E32Y;

[0409] (vv) a VH comprising the VH CDRs of the VH of P1-068761 E32Y E55A and a

[0410] VL comprising the VL CDRs of P1-068761 E32Y E55A and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least

[0411] 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the VH and VL of P1-068761 E32Y E55A;

[0412] (ww) a VH comprising the VH CDRs of the VH of P1-068761 E32Y E56N and a VL comprising the VL CDRs of P1-068761 E32Y E56N and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least

[0413] 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the VH and VL of P1-068761 E32Y E56N;

[0414] (xx) a VH comprising the VH CDRs of the VH of PI -068761 E30D E32Y and a

[0415] VL comprising the VL CDRs of P1-068761 E30D E32Y and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068761 E30D E32Y;

[0416] (yy) a VH comprising the VH CDRs of the VH of P1-068761 E32Y H100G and a

[0417] VL comprising the VL CDRs of PI -068761 E32Y H100G and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068761 E32Y H100G;

[0418] (zz) a VH comprising the VH CDRs of the VH of PI -06876 l_E32Y_E100fF and a

[0419] VL comprising the VL CDRs of Pl-068761_E32Y_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068761_E32Y_E100fF;

[0420] (aaa) a VH comprising the VH CDRs of the VH of P1-068767 D52N D102V and a VL comprising the VL CDRs of P1-068767 D52N D102V and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068767_D52N_D102V;

[0421] (bbb) a VH comprising the VH CDRs of the VH of P1-068767 D52N and a VL comprising the VL CDRs of P1-068767 D52N and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068767_D52N;

[0422] (ccc) a VH comprising the VH CDRs of the VH of P1-068767 D52N E55A and a VL comprising the VL CDRs of P1-068767 D52N E55A and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068767_D52N_E55A;

[0423] (ddd) a VH comprising the VH CDRs of the VH of P1-068767 E55A D102V and a VL comprising the VL CDRs of P1-068767 E55A D102V and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068767 E55A D102V;

[0424] (eee) a VH comprising the VH CDRs of the VH of P1-068767 D102V and a VL comprising the VL CDRs of P1-068767 D102V and VH and VL amino acid sequences that are 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% identical to the

[0425] VH and VL of P1-068767 D102V;

[0426] (fff) a VH comprising the VH CDRs of the VH of P1-068767 E55A and a VL comprising the VL CDRs of P1-068767 E55A and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least

[0427] 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the VH and

[0428] VL of P1-068767_E55A;

[0429] (ggg) a VH comprising the VH CDRs of the VH of P1-068767 E30D D52N and a

[0430] VL comprising the VL CDRs of P1-068767 E30D D52N and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least

[0431] 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the VH and VL of P1-068767 E30D D52N;

[0432] (hhh) a VH comprising the VH CDRs of the VH of P1-068767 E30D D102V and a

[0433] VL comprising the VL CDRs of P1-068767 E30D D102V and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least

[0434] 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to the VH and VL of P1-068767 E30D D102V;

[0435] (iii)a VH comprising the VH CDRs of the VH of P1-068767 E30D and a VL comprising the VL CDRs of P1-068767 E30D and VH and VL amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least

[0436] 96%, at least 97%, at least 98%, or at least 99% identical to the VH and VL of Pl-

[0437] 068767_E30D;

[0438] (jjj)a VH comprising the VH CDRs of the VH of P1-068767 E30D E55A and a VL comprising the VL CDRs of P1-068767 E30D E55A and VH and VL amino acid sequences that are 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% identical to the VH and VL of P1-068767 E30D E55A;

[0439] (kkk) a VH comprising the VH CDRs of the VH of Pl-068767_E100fE_D102V and a VL comprising the VL CDRs of Pl-068767_E100fF_D102V and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068767_E100fF_D102V;

[0440] (lll)a VH comprising the VH CDRs of the VH of Pl-068767_E55A_E100fF and a VL comprising the VL CDRs of Pl-068767_E55A_E100fE and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068767_E55A_E100fF;

[0441] (mmm) a VH comprising the VH CDRs of the VH of Pl-068767_D52N_E100fF and a VL comprising the VL CDRs of Pl-068767_D52N_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068767_D52N_E100fE;

[0442] (nnn) a VH comprising the VH CDRs of the VH of Pl-068767_E100fF and a VL comprising the VL CDRs of Pl-068767_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of Pl-068767_E100fE; or

[0443] (ooo) a VH comprising the VH CDRs of the VH of Pl-068767_E30D_E100fF and a VL comprising the VL CDRs of Pl-068767_E30D_E100fF and VH and VL amino acid sequences that are 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% identical to the VH and VL of PI -068767 E30D ElOOfF.

[0444] An anti-h VISTA Ab may comprise: (a) a VH consisting of the amino acid sequence of the VH of PI -061029 and a VL consisting of the VL of PI -061029;

[0445] (b) a VH consisting of the amino acid sequence of the VH of Pl-061015 and a VL consisting of the VL of Pl-061015;

[0446] (c) a VH consisting of the amino acid sequence of the VH of PI -068757 and a VL consisting of the VL of Pl-068757;

[0447] (d) a VH consisting of the amino acid sequence of the VH of PI -068759 and a VL consisting of the VL of PI -068759;

[0448] (e) a VH consisting of the amino acid sequence of the VH of Pl-068761 and a VL consisting of the VL of PI -068761;

[0449] (f) a VH consisting of the amino acid sequence of the VH of PI -068763 and a VL consisting of the VL of PI -068763;

[0450] (g) a VH consisting of the amino acid sequence of the VH of PI -068765 and a VL consisting of the VL of PI -068765;

[0451] (h) a VH consisting of the amino acid sequence of the VH of PI -068767 and a VL consisting of the VL of PI -068767;

[0452] (i) a VH consisting of the amino acid sequence of the VH of PI -068769 and a VL consisting of the VL of PI -068769;

[0453] (j) a VH consisting of the amino acid sequence of the VH of Pl-068771 and a VL consisting of the VL of PI -068771;

[0454] (k) a VH consisting of the amino acid sequence of the VH of PI -068773 and a VL consisting of the VL of PI -068773;

[0455] (1) a VH consisting of the amino acid sequence of the VH of PI -068775 and a VL consisting of the VL of Pl-068775;

[0456] (m)a VH consisting of the amino acid sequence of the VH of Pl-069059 and a VL consisting of the VL of Pl-069059;

[0457] (n) a VH consisting of the amino acid sequence of the VH of PI -069061 and a VL consisting of the VL of PI -069061;

[0458] (o) a VH consisting of the amino acid sequence of the VH of PI -069063 and a VL consisting of the VL of PI -069063; (p) a VH consisting of the amino acid sequence of the VH of PI -069065 and a VL consisting of the VL of Pl-069065;

[0459] (q) a VH consisting of the amino acid sequence of the VH of PI -069067 and a VL

[0460] consisting of the VL of PI -069067;

[0461] (r) a VH consisting of the amino acid sequence of the VH of PI -069069 and a VL

[0462] consisting of the VL of PI -069069;

[0463] (s) a VH consisting of the amino acid sequence of the VH of Pl-069071 and a VL

[0464] consisting of the VL of Pl-069071;

[0465] (t) a VH consisting of the amino acid sequence of the VH of PI -069073 and a VL

[0466] consisting of the VL of PI -069073;

[0467] (u) a VH consisting of the amino acid sequence of the VH of PI -069075 and a VL

[0468] consisting of the VL of Pl-069075;

[0469] (v) a VH consisting of the amino acid sequence of the VH of PI -069077 and a VL

[0470] consisting of the VL of PI -069077;

[0471] (w) a VH consisting of the amino acid sequence of the VH of PI -068736 and a VL consisting of the VL of Pl-068736;

[0472] (x) a VH consisting of the amino acid sequence of the VH of Pl-068738 and a VL

[0473] consisting of the VL of Pl-068738;

[0474] (y) a VH consisting of the amino acid sequence of the VH of PI -068740 and a VL

[0475] consisting of the VL of PI -068740;

[0476] (z) a VH consisting of the amino acid sequence of the VH of PI -068742 and a VL

[0477] consisting of the VL of PI -068742;

[0478] (aa) a VH consisting of the amino acid sequence of the VH of PI -068744 and a VL consisting of the VL of Pl-068744;

[0479] (bb) a VH consisting of the amino acid sequence of the VH f PI -068746 and a VL consisting of the VL of PI -068746;

[0480] (cc) a VH consisting of the amino acid sequence of the VH of PI -068748 and a

[0481] VL consisting of the VL of Pl-068748;

[0482] (dd) a VH consisting of the amino acid sequence of the VH of PI -068750 and a VL consisting of the VL of Pl-068750; (ee) a VH consisting of the amino acid sequence of the VH of PI -068752 and a

[0483] VL consisting of the VL of Pl-068752;

[0484] (ff) a VH consisting of the amino acid sequence of the VH of PI -068754 and a VL

[0485] consisting of the VL of PI -068754;

[0486] (gg) a VH consisting of the amino acid sequence of the VH of P1-068761 E55A and a VL consisting of the amino acid sequence of the VL of P1-068761 E55A; (hh) a VH consisting of the amino acid sequence of the VH of P1-068761 H100G and a VL consisting of the amino acid sequence of the VL of PI -068761 H100G; (ii) a VH consisting of the amino acid sequence of the VH of P1-068761 E56N and a VL consisting of the amino acid sequence of the VL of P1-068761 E56N;

[0487] (jj) a VH consisting of the amino acid sequence of the VH of P1-068761 E55A E56N and a VL consisting of the amino acid sequence of the VL of Pl-

[0488] 068761_E55A_E56N;

[0489] (kk) a VH consisting of the amino acid sequence of the VH of P1-068761 E30D and a VL consisting of the amino acid sequence of the VL of P1-068761 E30D;

[0490] (11) a VH consisting of the amino acid sequence of the VH of P1-068761 E30D E55A and a VL consisting of the amino acid sequence of the VL of Pl-

[0491] 068761_E30D_E55A;

[0492] (mm) a VH consisting of the amino acid sequence of the VH of Pl- 068761 E56N H100G and a VL consisting of the amino acid sequence of the VL of

[0493] PI -068761 E56N H100G;

[0494] (nn) a VH consisting of the amino acid sequence of the VH of Pl-

[0495] 068761 E30D H100G and a VL consisting of the amino acid sequence of the VL of

[0496] P1-068761 E30D H100G;

[0497] (oo) a VH consisting of the amino acid sequence of the VH of Pl-

[0498] 068761 E30D E56N and a VL consisting of the amino acid sequence of the VL of

[0499] P1-068761_E30D_E56N;

[0500] (pp) a VH consisting of the amino acid sequence of the VH of Pl-068761_E100fF and a VL consisting of the amino acid sequence of the VL of PI -06876 l ElOOfF; (qq) a VH consisting of the amino acid sequence of the VH of Pl-

[0501] 068761_E55A_E100fF and a VL consisting of the amino acid sequence of the VL of

[0502] Pl-068761_E55A_E100fE;

[0503] (rr) a VH consisting of the amino acid sequence of the VH of Pl-068761_H100G_E100fF and a VL consisting of the amino acid sequence of the VL of Pl-

[0504] 068761_H100G_E100fE;

[0505] (ss)a VH consisting of the amino acid sequence of the VH of Pl-068761_E30D_E100fF and a VL consisting of the amino acid sequence of the VL of Pl-

[0506] 068761_E30D_E100fE;

[0507] (tt) a VH consisting of the amino acid sequence of the VH of Pl-068761_E56N_E100fF and a VL consisting of the amino acid sequence of the VL of Pl-

[0508] 068761_E56N_E100fF;

[0509] (uu) a VH consisting of the amino acid sequence of the VH of P1-068761 E32Y and a VL consisting of the amino acid sequence of the VL of PI -068761 E32Y; (vv) a VH consisting of the amino acid sequence of the VH of Pl-

[0510] 068761 E32Y E55A and a VL consisting of the amino acid sequence of the VL of

[0511] P1-068761_E32Y_E55A;

[0512] (ww) a VH consisting of the amino acid sequence of the VH of Pl-

[0513] 068761 E32Y E56N and a VL consisting of the amino acid sequence of the VL of PI -068761_E32Y_E56N;

[0514] (xx) a VH consisting of the amino acid sequence of the VH of Pl-

[0515] 068761 E30D E32Y and a VL consisting of the amino acid sequence of the VL of

[0516] P1-068761 E30D E32Y;

[0517] (yy) a VH consisting of the amino acid sequence of the VH of Pl- 068761 E32Y H100G and a VL consisting of the amino acid sequence of the VL of

[0518] PI -068761 E32Y H100G;

[0519] (zz) a VH consisting of the amino acid sequence of the VH of Pl-

[0520] 06876 l_E32Y_E100fF and a VL consisting of the amino acid sequence of the VL of

[0521] Pl-068761_E32Y_E100fE; (aaa) a VH consisting of the amino acid sequence of the VH of Pl-

[0522] 068767 D52N D102V and a VL consisting of the amino acid sequence of the VL of

[0523] P 1 -068767_D52N_D 102 V;

[0524] (bbb) a VH consisting of the amino acid sequence of the VH of P1-068767 D52N and a VL consisting of the amino acid sequence of the VL of P1-068767 D52N;

[0525] (ccc) a VH consisting of the amino acid sequence of the VH of Pl-

[0526] 068767 D52N E55A and a VL consisting of the amino acid sequence of the VL of

[0527] P 1 -068767_D52N_E55 A;

[0528] (ddd) a VH consisting of the amino acid sequence of the VH of Pl- 068767 E55A D102V and a VL consisting of the amino acid sequence of the VL of

[0529] P 1 -068767_E55 A_D 102 V;

[0530] (eee) a VH consisting of the amino acid sequence of the VH of P1-068767 D102V and a VL consisting of the amino acid sequence of the VL of P1-068767 D102V; (fff) a VH consisting of the amino acid sequence of the VH of P1-068767 E55A and a VL consisting of the amino acid sequence of the VL of P1-068767 E55A;

[0531] (ggg) a VH consisting of the amino acid sequence of the VH of Pl-

[0532] 068767 E30D D52N and a VL consisting of the amino acid sequence of the VL of

[0533] P 1 -068767_E30D_D52N;

[0534] (hhh) a VH consisting of the amino acid sequence of the VH of Pl- 068767 E30D D102V and a VL consisting of the amino acid sequence of the VL of

[0535] P 1 -068767_E30D_D 102 V;

[0536] (iii) a VH consisting of the amino acid sequence of the VH of P1-068767 E30D and a

[0537] VL consisting of the amino acid sequence of the VL of P1-068767 E30D;

[0538] (jjj)a VH consisting of the amino acid sequence of the VH of P1-068767 E30D E55A and a VL consisting of the amino acid sequence of the VL of Pl-

[0539] 068767_E30D_E55A;

[0540] (kkk) a VH consisting of the amino acid sequence of the VH of Pl-

[0541] 068767_E100fF_D102V and a VL consisting of the amino acid sequence of the VL of P 1 -068767 E1 OOfF D 102 V; (111) a VH consisting of the amino acid sequence of the VH of Pl-068767_E55A_E100fF and a VL consisting of the amino acid sequence of the VL of Pl-

[0542] 068767_E55A_E100ff;

[0543] (mmm) a VH consisting of the amino acid sequence of the VH of Pl- 068767_D52N_E100fF and a VL consisting of the amino acid sequence of the VL of

[0544] Pl-068767_D52N_E100fF;

[0545] (nnn) a VH consisting of the amino acid sequence of the VH of Pl-068767_E100fF and a VL consisting of the amino acid sequence of the VL of Pl-068767_E100fF; or (ooo) a VH consisting of the amino acid sequence of the VH of Pl- 068767_E30D_E100fF and a VL consisting of the amino acid sequence of the VL of

[0546] Pl-068767_E30D_E100fF.

[0547] In certain embodiments, an anti-VISTA Ab comprises any of the variable regions and / or variable region CDRs 1-3 of the antibodies described above and elsewhere herein, such as:

[0548] (1) one or more of VH CDRl, CDR2 and CDR3 of:

[0549] (2) the VH CDRl, CDR2 and CDR3 of:

[0550] (3) the VH of:

[0551] (4) one or more of VH CDRl, CDR2 and CDR3 and one or more of VL CDRl, CDR2 and CDR3 of:

[0552] (5) the VH CDRl, CDR2 and CDR3 and VL CDRl, CDR2 and CDR3 of:

[0553] or

[0554] (6) the VH and the VLs of:

[0555] Pl-061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl- 068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl- 069065, Pl-069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl- 061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761 E55A, PI -068761 H100G, Pl- 068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100ff , Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF; and the anti- VISTA Ab

[0556] is also an IgG antibody, such as IgGl, IgG2, IgG3 or IgG4 antibody or a modified form thereof as described in the section below. In some embodiments, the constant region has effector function, and in some embodiments, the constant region is effectorless. In certain embodiments, the constant region is that of IgGl .3. In certain embodiments, an anti-VISTA Ab comprises any of the variable regions and / or variable region CDRs 1-3 of the antibodies described above and elsewhere herein, such as:

[0557] (1) one or more of VH CDRl, CDR2 and CDR3 of:

[0558] (2) the VH CDRl, CDR2 and CDR3 of:

[0559] (3) the VH of:

[0560] (4) one or more of VH CDRl, CDR2 and CDR3 and one or more of VL CDRl, CDR2 and CDR3 of:

[0561] (5) the VH CDRl, CDR2 and CDR3 and VL CDRl, CDR2 and CDR3 of:

[0562] or

[0563] (6) the VH and the VLs of:

[0564] Pl-061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl- 068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl- 069065, Pl-069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077, Pl- 061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068766, Pl-068748, Pl-068750, Pl-068752 Pl-068754, P1-068761_E55A, PI -068761 H100G, Pl- 068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761 E56N H100G, P1-068761 E30D H100G, P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl-

[0565] 068761 E32Y H100G, PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, Pl- 068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, or Pl-068767_E30D_E100fF,

[0566] and further comprises one or more of the following characteristics:

[0567] specifically binding to hVISTA, e.g., histidine rich region of the ECD or a polypeptide comprising amino acid residues 35-127 of SEQ ID NO: 2, at acidic pH, e.g., pH 6.0 or pH 6.5;

[0568] - lacking of significant binding to hVISTA, e.g., histidine rich region of the ECD or a polypeptide comprising amino acid residues 35-127 of SEQ ID NO: 2, at

[0569] physiological pH or neutral pH, e.g., pH 7.4 or pH 7.0;

[0570] specifically binding to cyno VISTA, e.g., histidine rich region of the ECD, at acidic pH, e.g., pH 6.0 or pH 6.5;

[0571] - lacking of significant binding to cyno VISTA, e.g., histidine rich region of the ECD, at physiological pH or neutral pH, e.g., pH 7.4 or pH 7.0;

[0572] having reduced binding to hVISTA-ECD having a substitution at one or more of the following amino acids: T35, Y37, K38, T39, Y41, R54, T61, F62, Q63, L65, H66, L67, H68, H69, F97, LI 15, VI 17, 1119, H121, H122, S124, E125, R127 relative to hVISTA ECD having SEQ ID NO: 2;

[0573] - cross-competiting for binding to hVISTA with PI -061029, Pl-068761, Pl-068767 and / or Pl-061015;

[0574] inhibiting binding of hVISTA to human T cells at acidic pH e.g., pH 6.0 or pH 6.5; inhibiting binding of hVISTA to PSGL-1 at acidic pH e.g., pH 6.0 or pH 6.5;

[0575] - a mean residence time of at least 350 hours in cynomolgus monkeys; stimulating T cell activation;

[0576] inhibiting VISTA mediated cell: cell adhesion; and

[0577] specifically binding to hVISTA in samples of human tumor cells or samples of inflamed human tissue.

[0578] In certain embodiments, an anti-hVISTA Ab comprises a heavy chain (HC) comprising the amino acid sequence of the heavy chain of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti-h VISTA Ab comprises a heavy chain comprising the amino acid sequence of the heavy chain of Pl-061029 or Pl-061015 or progeny thereof, as shown below in the Sequence Table, comprising an IgG1.3 heavy chain constant region, such as Pl-061029.IgG1.3 (SEQ ID NO: 69), Pl-068757.IgG1.3, Pl- 068759.IgG1.3, Pl-068761.IgG1.3, Pl-068763.IgG1.3, Pl-068765.IgG1.3, Pl- 068767.IgG1.3, Pl-068769.IgG1.3, Pl-068771.IgG1.3, Pl-068773.IgG1.3, Pl- 068775.IgG1.3, Pl-069059.IgG1.3, Pl-069061.IgG1.3, Pl-069063.IgG1.3, Pl- 069065.IgG1.3, Pl-069067.IgG1.3, Pl-069069.IgG1.3, Pl-069071.IgG1.3, Pl- 069073. IgGl .3, Pl-069075.IgG1.3, Pl-069077.IgG1.3, Pl-061015.IgG1.3, Pl- 068736.IgG1.3, Pl-068738.IgG1.3, Pl-068740.IgG1.3, Pl-068742.IgG1.3, Pl- 068744.IgG1.3, Pl-068766.IgG1.3, Pl-068748.IgG1.3, Pl-068750.IgG1.3, Pl- 068752.IgG1.3, Pl-068754.IgG1.3, Pl-068761_E55A.IgG1.3, Pl-068761_H100G.IgG1.3, Pl-068761_E56N.IgG1.3, Pl-068761_E55A_E56N.IgG1.3, Pl-068761_E30D.IgG1.3, Pl- 068761_E30D_E55A.IgG1.3, Pl-068761_E56N_H100G.IgG1.3, Pl- 068761_E30D_H100G.IgG1.3, Pl-068761_E30D_E56N.IgG1.3, Pl- 068761_E100fE.IgG1.3, Pl-068761_E55A_E100fF.IgG1.3, Pl- 068761_H100G_E100fE.IgG1.3, Pl-068761_E30D_E100fF.IgG1.3, Pl- 068761_E56N_E100fF.IgG1.3, Pl-068761_E32Y.IgG1.3, Pl-068761_E32Y_E55A.IgG1.3, Pl-068761_E32Y_E56N.IgG1.3, Pl-068761_E30D_E32Y.IgG1.3, Pl- 068761_E32Y_H100G.IgG1.3, Pl-068761_E32Y_E100fF.IgG1.3, Pl- 068767_D52N_D102V.IgG1.3, Pl-068767_D52N.IgG1.3, Pl-068767_D52N_E55A.IgG1.3, Pl-068767_E55A_D102V.IgG1.3, Pl-068767_D102V.IgG1.3, Pl-068767_E55A.IgG1.3, Pl-068767_E30D_D52N.IgG1.3, Pl-068767_E30D_D102V.IgG1.3, Pl- 068767_E30D.IgG1.3, Pl-068767_E30D_E55A.IgG1.3, Pl- 068767_E100fF_D102V.IgG1.3, Pl-068767_E55A_E100fF.IgG1.3, Pl- 068767_D52N_E100fF.IgG1.3, Pl-068767_E100fF.IgG1.3, or Pl- 068767_E30D_E100fF.IgG1.3.

[0579] In certain embodiments, an anti-hVISTA Ab comprises a heavy chain comprising the amino acid sequence of the heavy chain of any of the anti-h VISTA Abs provided herein, which comprise an IgG1.3 heavy chain constant region, and the amino acid sequence of the light chain of any of the anti-h VISTA Abs provided herein. In certain embodiments, an anti- hVISTA Ab comprises a heavy chain comprising the amino acid sequence of the VH of Pl- 061029 or Pl-061015 or progeny thereof, which comprise an IgG1.3 HC constant region, such as Pl-061029.IgG1.3 (SEQ ID NO: 69), Pl-068757.IgG1.3, Pl-068759.IgG1.3, Pl- 068761. IgGl .3, Pl-068763.IgG1.3, Pl-068765.IgG1.3, Pl-068767.IgG1.3, Pl- 068769.IgG1.3, Pl-068771.IgG1.3, Pl-068773.IgG1.3, Pl-068775.IgG1.3, Pl- 069059.IgG1.3, Pl-069061.IgG1.3, Pl-069063.IgG1.3, Pl-069065.IgG1.3, Pl- 069067.IgG1.3, Pl-069069.IgG1.3, Pl-069071.IgG1.3, Pl-069073.IgG1.3, Pl- 069075.IgG1.3, Pl-069077.IgG1.3, Pl-061015.IgG1.3, Pl-068736.IgG1.3, Pl- 068738.IgG1.3, Pl-068740.IgG1.3, Pl-068742.IgG1.3, Pl-068744.IgG1.3, Pl- 068766.IgG1.3, Pl-068748.IgG1.3, Pl-068750.IgG1.3, Pl-068752.IgG1.3, Pl- 068754.IgG1.3, Pl-068761_E55A.IgG1.3, Pl-068761_H100G.IgG1.3, Pl- 068761_E56N.IgG1.3, Pl-068761_E55A_E56N.IgG1.3, Pl-068761_E30D.IgG1.3, Pl- 068761_E30D_E55A.IgG1.3, Pl-068761_E56N_H100G.IgG1.3, Pl- 068761_E30D_H100G.IgG1.3, Pl-068761_E30D_E56N.IgG1.3, Pl- 068761_E100fE.IgG1.3, Pl-068761_E55A_E100fF.IgG1.3, Pl- 068761_H100G_E100fE.IgG1.3, Pl-068761_E30D_E100fF.IgG1.3, Pl- 068761_E56N_E100fF.IgG1.3, Pl-068761_E32Y.IgG1.3, Pl-068761_E32Y_E55A.IgG1.3, Pl-068761_E32Y_E56N.IgG1.3, Pl-068761_E30D_E32Y.IgG1.3, Pl- 068761_E32Y_H100G.IgG1.3, Pl-068761_E32Y_E100fF.IgG1.3, Pl- 068767_D52N_D102V.IgG1.3, Pl-068767_D52N.IgG1.3, Pl-068767_D52N_E55A.IgG1.3, Pl-068767_E55A_D102V.IgG1.3, Pl-068767_D102V.IgG1.3, Pl-068767_E55A.IgG1.3, Pl-068767_E30D_D52N.IgG1.3, Pl-068767_E30D_D102V.IgG1.3, Pl- 068767_E30D.IgG1.3, Pl-068767_E30D_E55A.IgG1.3, Pl- 068767_E100fF_D102V.IgG1.3, Pl-068767_E55A_E100fF.IgG1.3, Pl- 068767_D52N_E100fF.IgG1.3, Pl-068767_E100fF.IgG1.3, or Pl-

[0580] 068767_E30D_E100fF.IgG1.3; and a light chain comprising the amino acid sequence of the light chain of P 1 -061029 or P 1 -061015.

[0581] An anti-h VISTA Ab may comprise:

[0582] (a) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 061029. IgGl .3 (SEQ ID NO: 69) and a light chain comprising the light chain amino acid sequence of PI -061029 (SEQ ID NO: 70);

[0583] (b) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 061015. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-061015;

[0584] (c) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068757. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068757;

[0585] (d) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068759. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068759;

[0586] (e) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068761. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068761;

[0587] (f) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068763. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068763;

[0588] (g) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068765. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068765;

[0589] (h) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068767. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068767; (i) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0590] 068769. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068769;

[0591] (j) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068771. IgGl .3 and a light chain comprising the light chain amino acid sequence of

[0592] Pl-068771;

[0593] (k) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0594] 068773. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068773;

[0595] (1) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0596] 068775. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068775;

[0597] (m)a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0598] 069059. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-069059;

[0599] (n) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0600] 069061. IgGl .3 and a light chain comprising the light chain amino acid sequence of PI -069061;

[0601] (o) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 069063. IgGl .3 and a light chain comprising the light chain amino acid sequence of

[0602] PI -069063;

[0603] (p) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0604] 069065. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-069065;

[0605] (q) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0606] 069067. IgGl .3 and a light chain comprising the light chain amino acid sequence of PI -069067;

[0607] (r) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0608] 069069. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-069069; (s) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0609] 069071. IgGl .3 and a light chain comprising the light chain amino acid sequence of PI -069071;

[0610] (t) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 069073. IgGl .3 and a light chain comprising the light chain amino acid sequence of

[0611] PI -069073;

[0612] (u) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0613] 069075. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-069075;

[0614] (v) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0615] 069077. IgGl .3 and a light chain comprising the light chain amino acid sequence of PI -069077;

[0616] (w) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0617] 068736. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068736;

[0618] (x) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0619] 068738. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068738;

[0620] (y) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068740. IgGl .3 and a light chain comprising the light chain amino acid sequence of

[0621] Pl-068740;

[0622] (z) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0623] 068742. IgGl .3 and a light chain comprising the light chain amino acid sequence of PI -068742;

[0624] (aa) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0625] 068744. IgGl .3 and a light chain comprising the light chain amino acid sequence of PI -068744;

[0626] (bb) a heavy chain comprising the amino acid sequence of the heavy chain f Pl-

[0627] 068746. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068746; (cc) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0628] 068748. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068748;

[0629] (dd) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068750. IgGl .3 and a light chain comprising the light chain amino acid sequence of

[0630] Pl-068750;

[0631] (ee) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068752. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068752;

[0632] (ff) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0633] 068754. IgGl .3 and a light chain comprising the light chain amino acid sequence of Pl-068754;

[0634] (gg) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0635] 068761_E55A.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761 E55A;

[0636] (hh) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0637] 068761_H100G.IgG1.3 and a light chain comprising the light chain amino acid sequence of PI -068761 H100G;

[0638] (ii) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068761_E56N.IgG1.3 and a light chain comprising the light chain amino acid sequence of PI -068761_E56N;

[0639] (jj) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0640] 068761_E55A_E56N.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761_E55A_E56N;

[0641] (kk) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0642] 068761_E30D.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761 E30D;

[0643] (11) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0644] 068761_E30D_E55A.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761 E30D E55A; (mm) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068761_E56N_H100G.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761 E56N H100G;

[0645] (nn) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068761_E30D_H100G.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761 E30D H100G;

[0646] (oo) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0647] 068761_E30D_E56N.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761 E30D E56N;

[0648] (pp) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0649] 068761_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068761_E100fF;

[0650] (qq) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0651] 068761_E55A_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068761_E55A_E100fF;

[0652] (rr) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0653] 068761_H100G_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068761_H100G_E100fE;

[0654] (ss)a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068761_E30D_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068761_E30D_E100fF;

[0655] (tt) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068761_E56N_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068761_E56N_E100fF;

[0656] (uu) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0657] 068761_E32Y.IgG1.3 and a light chain comprising the light chain amino acid sequence of PI -068761 E32Y;

[0658] (vv) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0659] 068761_E32Y_E55A.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761_E32Y_E55A; (ww) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0660] 068761_E32Y_E56N.IgG1.3 and a light chain comprising the light chain amino acid sequence of PI -068761_E32Y_E56N;

[0661] (xx) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068761_E30D_E32Y.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761 E30D E32Y;

[0662] (yy) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0663] 068761_E32Y_H100G.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068761 E32Y H100G;

[0664] (zz) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0665] 068761_E32Y_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068761_E32Y_E100fF;

[0666] (aaa) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0667] 068767_D52N_D102V.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767_D52N_D102V;

[0668] (bbb) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0669] 068767_D52N.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767_D52N;

[0670] (ccc) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068767_D52N_E55A.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767_D52N_E55A;

[0671] (ddd) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0672] 068767_E55A_D102V.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767_E55A_D102V;

[0673] (eee) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0674] 068767_D102V.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767_D102V;

[0675] (fff) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0676] 068767_E55A.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767_E55A; (ggg) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0677] 068767_E30D_D52N.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767_E30D_D52N;

[0678] (hhh) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068767_E30D_D102V.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767 E30D D102V;

[0679] (iii)a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0680] 068767_E30D.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767 E30D;

[0681] Gjj)aheavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0682] 068767_E30D_E55A.IgG1.3 and a light chain comprising the light chain amino acid sequence of P1-068767 E30D E55A;

[0683] (kkk) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0684] 068767_E100fF_D102V.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068767_E100fE_D102V;

[0685] (lll)a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0686] 068767_E55A_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068767_E55A_E100fF;

[0687] (mmm) a heavy chain comprising the amino acid sequence of the heavy chain of Pl- 068767_D52N_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068767_D52N_E100fF;

[0688] (nnn) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0689] 068767_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068767_E100fF; or

[0690] (ooo) a heavy chain comprising the amino acid sequence of the heavy chain of Pl-

[0691] 068767_E30D_E100fF.IgG1.3 and a light chain comprising the light chain amino acid sequence of Pl-068767_E30D_E100fF.

[0692] An anti-h VISTA Ab may comprise: (a) a heavy chain (HC) comprising the HC CDRs of the HC of PI -061029 and a light chain (LC) comprising the LC CDRs of PI -061029 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-061029.IgG1.3, respectively;

[0693] (b) a HC comprising the HC CDRs of the HC of Pl-061015 and a LC comprising the LC CDRs of Pl-061015 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-061015.IgG1.3, respectively;

[0694] (c) a HC comprising the HC CDRs of the HC of PI -068757 and a LC comprising the LC CDRs of PI -068757 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068757.IgG1.3, respectively;

[0695] (d) a HC comprising the HC CDRs of the HC of PI -068759 and a LC comprising the LC CDRs of PI -068759 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068759.IgG1.3, respectively;

[0696] (e) a HC comprising the HC CDRs of the HC of PI -068761 and a LC comprising the LC CDRs of PI -068761 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761.IgG1.3, respectively;

[0697] (f) a HC comprising the HC CDRs of the HC of PI -068763 and a LC comprising the LC CDRs of PI -068763 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068763.IgG1.3, respectively; a HC comprising the HC CDRs of the HC of PI -068765 and a LC comprising the LC CDRs of PI -068765 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068765.IgG1.3, respectively;

[0698] a HC comprising the HC CDRs of the HC of PI -068767 and a LC comprising the LC CDRs of PI -068767 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767.IgG1.3, respectively;

[0699] a HC comprising the HC CDRs of the HC of PI -068769 and a LC comprising the LC CDRs of PI -068769 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068769.IgG1.3, respectively;

[0700] a HC comprising the HC CDRs of the HC of Pl-068771 and a LC comprising the LC CDRs of Pl-068771 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068771. IgGl .3, respectively;

[0701] a HC comprising the HC CDRs of the HC of PI -068773 and a LC comprising the LC CDRs of PI -068773 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068773.IgG1.3, respectively;

[0702] a HC comprising the HC CDRs of the HC of PI -068775 and a LC comprising the LC CDRs of PI -068775 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068775.IgG1.3, respectively; (m)a HC comprising the HC CDRs of the HC of Pl-069059 and a LC comprising the LC CDRs of Pl-069059 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069059.IgG1.3, respectively;

[0703] (n) a HC comprising the HC CDRs of the HC of PI -069061 and a LC comprising the LC CDRs of PI -069061 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069061.IgG1.3, respectively;

[0704] (o) a HC comprising the HC CDRs of the HC of PI -069063 and a LC comprising the LC CDRs of PI -069063 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069063.IgG1.3, respectively;

[0705] (p) a HC comprising the HC CDRs of the HC of PI -069065 and a LC comprising the LC CDRs of PI -069065 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069065.IgG1.3, respectively;

[0706] (q) a HC comprising the HC CDRs of the HC of PI -069067 and a LC comprising the LC CDRs of PI -069067 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069067.IgG1.3, respectively;

[0707] (r) a HC comprising the HC CDRs of the HC of PI -069069 and a LC comprising the LC CDRs of PI -069069 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069069.IgG1.3, respectively; (s) a HC comprising the HC CDRs of the HC of PI -069071 and a LC comprising the LC CDRs of PI -069071 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069071.IgG1.3, respectively;

[0708] (t) a HC comprising the HC CDRs of the HC of PI -069073 and a LC comprising the LC CDRs of PI -069073 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069073.IgG1.3, respectively;

[0709] (u) a HC comprising the HC CDRs of the HC of PI -069075 and a LC comprising the LC CDRs of PI -069075 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069075.IgG1.3, respectively;

[0710] (v) a HC comprising the HC CDRs of the HC of PI -069077 and a LC comprising the LC CDRs of PI -069077 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-069077.IgG1.3, respectively;

[0711] (w) a HC comprising the HC CDRs of the HC of Pl-068736 and a LC comprising the LC CDRs of Pl-068736 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068736.IgG1.3, respectively;

[0712] (x) a HC comprising the HC CDRs of the HC of PI -068738 and a LC comprising the LC CDRs of PI -068738 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068738.IgG1.3, respectively; (y) a HC comprising the HC CDRs of the HC of PI -068740 and a LC comprising the LC CDRs of PI -068740 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068740.IgG1.3, respectively;

[0713] (z) a HC comprising the HC CDRs of the HC of PI -068742 and a LC comprising the LC CDRs of PI -068742 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068742.IgG1.3, respectively;

[0714] (aa) a HC comprising the HC CDRs of the HC of PI -068744 and a LC comprising the LC CDRs of PI -068744 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068744.IgGl .3, respectively;

[0715] (bb) a HC comprising the HC CDRs of the HC of PI -068746 and a LC comprising the LC CDRs of PI -068746 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068746.IgGl .3, respectively;

[0716] (cc) a HC comprising the HC CDRs of the HC of PI -068748 and a LC comprising the LC CDRs of PI -068748 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068748.IgGl .3, respectively;

[0717] (dd) a HC comprising the HC CDRs of the HC of PI -068750 and a LC comprising the LC CDRs of PI -068750 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068750.IgGl .3, respectively; (ee) a HC comprising the HC CDRs of the HC of PI -068752 and a LC comprising the LC CDRs of PI -068752 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068752.IgGl .3, respectively;

[0718] (ff) a HC comprising the HC CDRs of the HC of PI -068754 and a LC comprising the LC CDRs of PI -068754 and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068754.IgG1.3, respectively;

[0719] (gg) a HC comprising the HC CDRs of the HC of Pl-068761_E55A.IgG1.3 and a

[0720] LC comprising the LC CDRs of P1-068761 E55A and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E55A.IgG1.3, respectively;

[0721] (hh) a HC comprising the HC CDRs of the HC of Pl-068761_H100G.IgG1.3 and a

[0722] LC comprising the LC CDRs of PI -068761 H100G and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_H100G.IgG1.3, respectively;

[0723] (ii) a HC comprising the HC CDRs of the HC of Pl-068761_E56N.IgG1.3 and a LC

[0724] comprising the LC CDRs of P1-068761 E56N and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E56N.IgG1.3, respectively;

[0725] (jj) a HC comprising the HC CDRs of the HC of Pl-068761_E55A_E56N.IgG1.3 and a LC comprising the LC CDRs of P1-068761 E55A E56N and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E55A_E56N.IgG1.3, respectively; (kk) a HC comprising the HC CDRs of the HC of Pl-068761_E30D.IgG1.3 and a

[0726] LC comprising the LC CDRs of P1-068761 E30D and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E30D.IgG1.3, respectively;

[0727] (11) a HC comprising the HC CDRs of the HC of Pl-068761_E30D_E55A.IgG1.3 and a LC comprising the LC CDRs of P1-068761 E30D E55A and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E30D_E55A.IgG1.3, respectively;

[0728] (mm) a HC compri sing the HC CDRs of the HC of P 1 -

[0729] 068761_E56N_H100G.IgG1.3 and a LC comprising the LC CDRs of Pl- 068761 E56N H100G and HC and LC amino acid sequences that are 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% identical to the HC and LC of P 1 -

[0730] 068761_E56N_H100G.IgG1.3, respectively;

[0731] (nn) a HC comprising the HC CDRs of the HC of P 1 -

[0732] 068761_E30D_H100G.IgG1.3 and a LC comprising the LC CDRs of Pl- 068761 E30D H100G and HC and LC amino acid sequences that are at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least

[0733] 97%, at least 98%, or at least 99% identical to the HC and LC of Pl- 068761_E30D_H100G.IgG1.3, respectively;

[0734] (oo) a HC comprising the HC CDRs of the HC of Pl-068761_E30D_E56N.IgG1.3 and a LC comprising the LC CDRs of P1-068761 E30D E56N and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E30D_E56N.IgG1.3, respectively;

[0735] (pp) a HC comprising the HC CDRs of the HC of Pl-068761_E100fF.IgG1.3 and a

[0736] LC comprising the LC CDRs of PI -06876 l ElOOfF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E100fF.IgG1.3, respectively;

[0737] (qq) a HC compri sing the HC CDRs of the HC of P 1 -

[0738] 068761_E55A_E100fF.IgG1.3 and a LC comprising the LC CDRs of Pl- 068761_E55A_E100fF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068761_E55A_E100fF.IgG1.3, respectively;

[0739] (rr) a HC comprising the HC CDRs of the HC of Pl-068761_H100G_E100fE.IgG1.3 and a LC comprising the LC CDRs of PI -06876 l HlOOG ElOOfF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_H100G_E100fF.IgG1.3, respectively;

[0740] (ss)a HC comprising the HC CDRs of the HC of Pl-068761_E30D_E100fE.IgG1.3 and a LC comprising the LC CDRs of Pl-068761_E30D_E100fF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E30D_E100fE.IgG1.3, respectively;

[0741] (tt) a HC comprising the HC CDRs of the HC of Pl-068761_E56N_E100fE.IgG1.3 and a LC comprising the LC CDRs of Pl-068761_E56N_E100fE and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E56N_E100fE.IgG1.3, respectively;

[0742] (uu) a HC comprising the HC CDRs of the HC of Pl-068761_E32Y.IgG1.3 and a LC comprising the LC CDRs of PI -068761 E32Y and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E32Y.IgG1.3, respectively;

[0743] (vv) a HC comprising the HC CDRs of the HC of Pl-068761_E32Y_E55A.IgG1.3 and a LC comprising the LC CDRs of P1-068761 E32Y E55A and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E32Y_E55A.IgG1.3, respectively;

[0744] (ww) a HC comprising the HC CDRs of the HC of Pl-068761_E32Y_E56N.IgG1.3 and a LC comprising the LC CDRs of P1-068761 E32Y E56N and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E32Y_E56N.IgG1.3, respectively;

[0745] (xx) a HC comprising the HC CDRs of the HC of Pl-068761_E30D_E32Y.IgG1.3 and a LC comprising the LC CDRs of P1-068761 E30D E32Y and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068761_E30D_E32Y.IgG1.3, respectively;

[0746] (yy) a HC comprising the HC CDRs of the HC of P 1 -

[0747] 068761_E32Y_H100G.IgG1.3 and a LC comprising the LC CDRs of Pl- 068761 E32Y H100G and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068761_E32Y_H100G.IgG1.3, respectively;

[0748] (zz) a HC comprising the HC CDRs of the HC of P 1 -

[0749] 068761_E32Y_E100fF.IgG1.3 and a LC comprising the LC CDRs of Pl- 06876 l_E32Y_E100fF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068761_E32Y_E100fF.IgG1.3, respectively;

[0750] (aaa) a HC compri sing the HC CDRs of the HC of P 1 -

[0751] 068767_D52N_D102V.IgG1.3 and a LC comprising the LC CDRs of Pl-

[0752] 068767 D52N D102V and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068767_D52N_D102V.IgG1.3, respectively;

[0753] (bbb) a HC comprising the HC CDRs of the HC of Pl-068767_D52N.IgG1.3 and a LC comprising the LC CDRs of P1-068767 D52N and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_D52N.IgG1.3, respectively;

[0754] (ccc) a HC comprising the HC CDRs of the HC of Pl-068767_D52N_E55A.IgG1.3 and a LC comprising the LC CDRs of P1-068767 D52N E55A and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_D52N_E55A.IgG1.3, respectively;

[0755] (ddd) a HC comprising the HC CDRs of the HC of P 1 -

[0756] 068767_E55A_D102V.IgG1.3 and a LC comprising the LC CDRs of Pl- 068767 E55A D102V and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068767_E55A_D102V.IgG1.3, respectively;

[0757] (eee) a HC comprising the HC CDRs of the HC of Pl-068767_D102V.IgG1.3 and a LC comprising the LC CDRs of P1-068767 D102V and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_D102V.IgG1.3, respectively;

[0758] (fff) a HC comprising the HC CDRs of the HC of Pl-068767_E55A.IgG1.3 and a LC comprising the LC CDRs of P1-068767 E55A and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_E55A.IgG1.3, respectively;

[0759] (ggg) a HC comprising the HC CDRs of the HC of Pl-068767_E30D_D52N.IgGl .3 and a LC comprising the LC CDRs of P1-068767 E30D D52N and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_E30D_D52N.IgG1.3, respectively;

[0760] (hhh) a HC comprising the HC CDRs of the HC of P 1 -

[0761] 068767_E30D_D102V.IgG1.3 and a LC comprising the LC CDRs of Pl- 068767 E30D D102V and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068767_E30D_D102V.IgG1.3, respectively;

[0762] (iii)a HC comprising the HC CDRs of the HC of Pl-068767_E30D.IgG1.3 and a LC

[0763] comprising the LC CDRs of P1-068767 E30D and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_E30D.IgG1.3, respectively;

[0764] (jjj)a HC comprising the HC CDRs of the HC of Pl-068767_E30D_E55A.IgG1.3 and a LC comprising the LC CDRs of P1-068767 E30D E55A and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_E30D_E55A.IgG1.3, respectively;

[0765] (kkk) a HC comprising the HC CDRs of the HC of P 1 -

[0766] 068767_E100fF_D102V.IgG1.3 and a LC comprising the LC CDRs of Pl- 068767_E100fF_D102V and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068767_E100fF_D102V.IgG1.3, respectively;

[0767] (lll)a HC comprising the HC CDRs of the HC of Pl-068767_E55A_E100fF.IgG1.3 and a LC comprising the LC CDRs of Pl-068767_E55A_E100fF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_E55A_E100fF.IgG1.3, respectively; (mmm) a HC compri sing the HC CDRs of the HC of P 1 -

[0768] 068767_D52N_E100ff .IgG1.3 and a LC comprising the LC CDRs of Pl- 068767_D52N_E100fF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068767_D52N_E100fF.IgG1.3, respectively;

[0769] (nnn) a HC comprising the HC CDRs of the HC of Pl-068767_E100fF.IgG1.3 and a LC comprising the LC CDRs of Pl-068767_E100fF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl-068767_E100fF.IgG1.3, respectively; or

[0770] (ooo) a HC compri sing the HC CDRs of the HC of P 1 -

[0771] 068767_E30D_E100fF.IgG1.3 and a LC comprising the LC CDRs of Pl- 068767_E30D_E100fF and HC and LC amino acid sequences that are 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% identical to the HC and LC of Pl- 068767_E30D_E100fF.IgG1.3, respectively.

[0772] In some embodiments, an anti-h VISTA Ab may comprise:

[0773] (a) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 061029. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -061029;

[0774] (b) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 061015. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of Pl-061015;

[0775] (c) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068757. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068757; (d) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068759. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068759;

[0776] (e) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068761;

[0777] (f) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068763. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068763;

[0778] (g) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068765. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068765;

[0779] (h) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068767;

[0780] (i) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068769. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068769;

[0781] (j) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0782] 068771. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068771;

[0783] (k) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0784] 068773. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068773;

[0785] (1) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0786] 068775. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068775;

[0787] (m)a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0788] 069059. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069059; (n) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0789] 069061. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069061;

[0790] (o) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0791] 069063. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069063;

[0792] (p) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0793] 069065. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069065;

[0794] (q) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0795] 069067. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069067;

[0796] (r) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0797] 069069. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069069;

[0798] (s) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0799] 069071. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069071;

[0800] (t) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0801] 069073. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069073;

[0802] (u) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0803] 069075. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069075;

[0804] (v) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0805] 069077. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -069077;

[0806] (w) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0807] 068736 and a light chain consisting of the amino acid sequence of the light chain of

[0808] Pl-068736; (x) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0809] 068738. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068738;

[0810] (y) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068740. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068740;

[0811] (z) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0812] 068742. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068742;

[0813] (aa) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0814] 068744. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068744;

[0815] (bb) a heavy chain consisting of the amino acid sequence of the heavy chain f Pl- 068746. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068746;

[0816] (cc) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068748. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068748;

[0817] (dd) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068750. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068750;

[0818] (ee) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068752. IgGl .3 and a light chain consisting of the amino acid sequence of the light chain of PI -068752;

[0819] (ff) a heavy chain consisting of the amino acid sequence of the heavy chain of PI -068754 and a light chain consisting of the amino acid sequence of the light chain of Pl- 068754;

[0820] (gg) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E55A.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 E55A; (hh) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0821] 068761_H100G.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 H100G;

[0822] (ii) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E56N.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761_E56N;

[0823] (jj) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0824] 068761_E55A_E56N.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761_E55A_E56N;

[0825] (kk) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0826] 068761_E30D.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 E30D;

[0827] (11) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0828] 068761_E30D_E55A.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 E30D E55A;

[0829] (mm) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E56N_H100G.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of PI -068761 E56N H100G;

[0830] (nn) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E30D_H100G.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 E30D H100G;

[0831] (oo) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E30D_E56N.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 E30D E56N;

[0832] (pp) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0833] 068761_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068761_E100fF;

[0834] (qq) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0835] 068761_E55A_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068761_E55A_E100fF; (rr) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_H100G_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068761_H100G_E100fF;

[0836] (ss)a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E30D_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068761_E30D_E100fF;

[0837] (tt) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E56N_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068761_E56N_E100fF;

[0838] (uu) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0839] 068761_E32Y.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 E32Y;

[0840] (vv) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0841] 068761_E32Y_E55A.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 E32Y E55A;

[0842] (ww) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E32Y_E56N.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of PI -068761_E32Y_E56N;

[0843] (xx) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068761_E30D_E32Y.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068761 E30D E32Y;

[0844] (yy) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0845] 068761_E32Y_H100G.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of PI -068761 E32Y H100G;

[0846] (zz) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0847] 068761_E32Y_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068761_E32Y_E100fF;

[0848] (aaa) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_D52N_D102V.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767_D52N_D102V; (bbb) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_D52N.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767_D52N;

[0849] (ccc) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_D52N_E55A.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767_D52N_E55A;

[0850] (ddd) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_E55A_D102V.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767 E55A D102V;

[0851] (eee) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0852] 068767_D102V.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767 D102V;

[0853] (fff) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_E55A.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767_E55A;

[0854] (ggg) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_E30D_D52N.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767_E30D_D52N;

[0855] (hhh) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_E30D_D102V.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767 E30D D102V;

[0856] (iii)a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0857] 068767_E30D.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767 E30D;

[0858] Gjj)aheavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0859] 068767_E30D_E55A.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of P1-068767 E30D E55A;

[0860] (kkk) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_E100fF_D102V.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068767_E100fF_D102V; (lll)a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0861] 068767_E55A_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068767_E55A_E100fF;

[0862] (mmm) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl- 068767_D52N_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068767_D52N_E100fF;

[0863] (nnn) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0864] 068767_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068767_E100fE; or

[0865] (ooo) a heavy chain consisting of the amino acid sequence of the heavy chain of Pl-

[0866] 068767_E30D_E100fF.IgG1.3 and a light chain consisting of the amino acid sequence of the light chain of Pl-068767_E30D_E100fF.

[0867] In some embodiments, the disclosure contemplates anti-VISTA mAbs comprising:

[0868] a heavy chain consisting of the amino acid sequences of the heavy chain of (a) to

[0869] (ooo) listed above followed by a Lys residue; and

[0870] a light chain consisting of the light chain amino acid sequence of (a) to (ooo) listed above;

[0871] wherein the heavy chain and light chain amino acid sequences are chosen from the same antibody species from among (a) to (ooo) listed above.

[0872] In some embodiments, an anti-h VISTA Ab may comprise a heavy chain amino acid sequence comprising the VH amino acid sequence of the antibody species herein, but rather than an IgGl .3 heavy chain constant region, as provided in the HC sequences in the

[0873] Sequence Table herein (and see SEQ ID NO: 163), the antibody may comprise a different heavy chain constant region sequence, such as a human wild-type IgGl constant region such as human IgGl allotype f (IgGlf) (SEQ ID NO: 182), or a modified human IgGl constant region such as IgGl . If (SEQ ID NO: 183), or a modified human IgGl constant region such as IgGl .P238K (SEQ ID NO: 184). Accordingly, embodiments of this disclosure include anti-VISTA Abs comprising: a heavy chain comprising (i) the amino acid sequence of the VH of Pl-061029 (SEQ ID NO: 67) and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-061029 (SEQ ID NO: 70); a heavy chain comprising (i) the amino acid sequence of the VH of Pl-061015 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-061015;

[0874] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068757 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068757;

[0875] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068759 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068759;

[0876] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068761 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068761;

[0877] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068763 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068763;

[0878] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068765 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068765;

[0879] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068767 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068767;

[0880] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068769 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068769;

[0881] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068771 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068771; (k) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068773 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068773;

[0882] (1) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068775 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068775;

[0883] (m)a heavy chain comprising (i) the amino acid sequence of the VH of PI -069059 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069059;

[0884] (n) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069061 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069061;

[0885] (o) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069063 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069063;

[0886] (p) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069065 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069065;

[0887] (q) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069067 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069067;

[0888] (r) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069069 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069069;

[0889] (s) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069071 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069071;

[0890] (t) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069073 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069073; (u) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069075 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069075;

[0891] (v) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069077 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -069077;

[0892] (w) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-068736 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-068736;

[0893] (x) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068738 and

[0894] (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068738;

[0895] (y) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068740 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068740;

[0896] (z) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068742 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068742;

[0897] (aa) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068744 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068744;

[0898] (bb) a heavy chain comprising the amino acid sequence of the heavy chain f Pl-

[0899] 068746 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068746;

[0900] (cc) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068748 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068748;

[0901] (dd) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068750 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-068750; (ee) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068752 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068752;

[0902] (ff) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068754 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068754;

[0903] (gg) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0904] 068761 E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of P1-068761 E55A;

[0905] (hh) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0906] 068761 H100G and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068761 H100G;

[0907] (ii) a heavy chain comprising (i) the amino acid sequence of the VH of P1-068761 E56N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of P1-068761 E56N;

[0908] (jj) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0909] 068761 E55A E56N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E55A_E56N;

[0910] (kk) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0911] 068761 E30D and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of P1-068761 E30D;

[0912] (11) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0913] 068761 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0914] 068761_E30D_E55A;

[0915] (mm) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E56N H100G and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E56N_H100G; (nn) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0916] 068761 E30D H100G and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761 E30D H100G;

[0917] (oo) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0918] 068761 E30D E56N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E30D_E56N;

[0919] (pp) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-068761_E100fF;

[0920] (qq) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0921] 068761_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E55A_E100fF;

[0922] (rr) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0923] 068761_H100G_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_H100G_E100fE;

[0924] (ss)a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0925] 068761_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E30D_E100fE;

[0926] (tt) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 06876 l_E56N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E56N_E100fE;

[0927] (uu) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0928] 068761 E32Y and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of PI -068761 E32Y; (vv) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0929] 068761 E32Y E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E32Y_E55A;

[0930] (ww) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0931] 068761 E32Y E56N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E32Y_E56N;

[0932] (xx) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E30D E32Y and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E30D_E32Y;

[0933] (yy) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0934] 068761 E32Y H100G and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0935] 068761 E32Y H100G;

[0936] (zz) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0937] 06876 l_E32Y_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E32Y_E100fE;

[0938] (aaa) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767 D52N D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068767_D52N_D102V;

[0939] (bbb) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0940] 068767 D52N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of P1-068767 D52N;

[0941] (ccc) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767 D52N E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0942] 068767_D52N_E55A;

[0943] (ddd) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0944] 068767 E55A D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0945] 068767_E55A_D102V;

[0946] (eee) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0947] 068767 D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of P1-068767 D102V;

[0948] (fff) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0949] 068767 E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of P1-068767 E55A;

[0950] (ggg) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0951] 068767 E30D D52N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0952] 068767_E30D_D52N;

[0953] (hhh) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0954] 068767 E30D D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068767_E30D_D102V;

[0955] (iii)a heavy chain comprising (i) the amino acid sequence of the VH of P1-068767 E30D and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of P1-068767 E30D;

[0956] (jjj)a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0957] 068767_E30D_E55A;

[0958] (kkk) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0959] 068767_E100fF_D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0960] 068767_E 1 OOfF D 102 V;

[0961] (lll)a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0962] 068767_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0963] 068767_E55A_E100fF;

[0964] (mmm) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0965] 068767_D52N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl- 068767_D52N_E100fF;

[0966] (nnn) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[0967] 068767_E100fE and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-068767_E100fF; or (ooo) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain comprising the light chain amino acid sequence of Pl-

[0968] 068767_E30D_E100fF.

[0969] Certain embodiments of this disclosure include anti-VISTA Abs comprising:

[0970] (a) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -061029

[0971] (SEQ ID NO: 67) and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -061029 (SEQ ID NO: 70);

[0972] (b) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-061015 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-061015;

[0973] (c) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068757 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068757; (d) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068759 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068759;

[0974] (e) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068761 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068761;

[0975] (f) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068763 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068763;

[0976] (g) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068765 and

[0977] (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068765;

[0978] (h) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-068767 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P 1 -068767;

[0979] (i) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068769 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068769;

[0980] (j) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-068771 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-068771;

[0981] (k) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068773 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068773;

[0982] (1) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068775 and

[0983] (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068775;

[0984] (m)a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-069059 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-069059; (n) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069061 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -069061;

[0985] (o) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069063 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -069063;

[0986] (p) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069065 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -069065;

[0987] (q) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069067 and

[0988] (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -069067;

[0989] (r) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069069 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P 1 -069069;

[0990] (s) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069071 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -069071;

[0991] (t) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-069073 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-069073;

[0992] (u) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069075 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-069075;

[0993] (v) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069077 and

[0994] (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -069077;

[0995] (w) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-068736 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-068736; (x) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068738 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068738;

[0996] (y) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068740 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068740;

[0997] (z) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068742 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068742;

[0998] (aa) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[0999] 068744 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068744;

[1000] (bb) a heavy chain consisting of the amino acid sequence of the heavy chain f Pl- 068746 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068746;

[1001] (cc) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1002] 068748 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068748;

[1003] (dd) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068750 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068750;

[1004] (ee) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068752 and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068752;

[1005] (ff) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068754 and

[1006] (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068754;

[1007] (gg) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1008] 068761 E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P1-068761 E55A;

[1009] - I l l - (hh) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1010] 068761 H100G and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068761 H100G;

[1011] (ii) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068761 E56N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P1-068761 E56N;

[1012] (jj) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1013] 068761 E55A E56N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E55A_E56N;

[1014] (kk) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1015] 068761 E30D and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P1-068761 E30D;

[1016] (11) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068761 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E30D_E55A;

[1017] (mm) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068761 E56N H100G and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1018] 068761_E56N_H100G;

[1019] (nn) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1020] 068761 E30D H100G and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761 E30D H100G;

[1021] (oo) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1022] 068761 E30D E56N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E30D_E56N; (pp) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1023] 068761_E100ff and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-068761_E100fF;

[1024] (qq) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068761_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E55A_E100fE;

[1025] (rr) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1026] 068761_H100G_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1027] 068761_H100G_E100fE;

[1028] (ss)a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1029] 068761_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E30D_E100fE;

[1030] (tt) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1031] 06876 l_E56N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E56N_E100fF;

[1032] (uu) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1033] 068761 E32Y and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of PI -068761 E32Y;

[1034] (vv) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1035] 068761 E32Y E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1036] 068761_E32Y_E55A;

[1037] (ww) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068761 E32Y E56N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E32Y_E56N; (xx) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1038] 068761 E30D E32Y and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E30D_E32Y;

[1039] (yy) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1040] 068761 E32Y H100G and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761 E32Y H100G;

[1041] (zz) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 06876 l_E32Y_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E32Y_E100fE;

[1042] (aaa) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767 D52N D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1043] 068767_D52N_D102V;

[1044] (bbb) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767 D52N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P1-068767 D52N; (ccc) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1045] 068767 D52N E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_D52N_E55A;

[1046] (ddd) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767 E55A D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_E55A_D102V;

[1047] (eee) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767 D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P1-068767 D102V; (fff) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1048] 068767 E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P1-068767 E55A;

[1049] (ggg) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767 E30D D52N and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1050] 068767_E30D_D52N;

[1051] (hhh) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1052] 068767 E30D D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1053] 068767_E30D_D102V;

[1054] (iii)a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1055] 068767 E30D and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of P1-068767 E30D;

[1056] Gjj)aheavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1057] 068767 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1058] 068767_E30D_E55A;

[1059] (kkk) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767_E100fF_D102V and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1060] 068767_E 1 OOfF D 102 V;

[1061] (lll)a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1062] 068767_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-

[1063] 068767_E55A_E100fF;

[1064] (mmm) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1065] 068767_D52N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_D52N_E100fF; (nnn) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767_E100ff and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl-068767_E100fF; or

[1066] (ooo) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 182, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_E30D_E100fF,

[1067] wherein the C-terminal amino acid of VH and the N-terminal amino acid of SEQ ID NO:

[1068] 182 form a peptidic bond. ome embodiments, the disclosure contemplates anti-VISTA mAbs comprising:

[1069] a heavy chain consisting of the amino acid sequences of (i) a VH of (a) to (ooo) listed above, (ii) SEQ ID NO: 182, and (iii) a Lys residue, wherein the C-terminal amino acid of VH and the N-terminal amino acid of SEQ ID NO: 182 form a peptidic bond and wherein the C-terminal amino acid of SEQ ID NO: 182 is joined to the N-terminal of the Lys; and

[1070] a light chain consisting of the light chain amino acid sequence of (a) to (ooo) listed above;

[1071] wherein the VH and light chain amino acid sequences are chosen from the same antibody species from among (a) to (ooo) listed above.

[1072] Certain embodiments of this disclosure include anti-VISTA Abs comprising:

[1073] (a) a heavy chain comprising (i) the amino acid sequence of the VH of PI -061029 (SEQ ID NO: 67) and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-061029 (SEQ ID NO: 70);

[1074] (b) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-061015 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-061015; a heavy chain comprising (i) the amino acid sequence of the VH of PI -068757 and

[1075] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068757;

[1076] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068759 and

[1077] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068759;

[1078] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068761 and

[1079] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068761;

[1080] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068763 and

[1081] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068763;

[1082] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068765 and

[1083] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068765;

[1084] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068767 and

[1085] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068767;

[1086] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068769 and

[1087] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068769;

[1088] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068771 and

[1089] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068771;

[1090] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068773 and

[1091] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068773;

[1092] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068775 and

[1093] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068775; (m)a heavy chain comprising (i) the amino acid sequence of the VH of Pl-069059 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-069059;

[1094] (n) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069061 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069061;

[1095] (o) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069063 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069063;

[1096] (p) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069065 and

[1097] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069065;

[1098] (q) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069067 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069067;

[1099] (r) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069069 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069069;

[1100] (s) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069071 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069071;

[1101] (t) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069073 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069073;

[1102] (u) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069075 and

[1103] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069075;

[1104] (v) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069077 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -069077; (w) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-068736 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-068736;

[1105] (x) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068738 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068738;

[1106] (y) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068740 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068740;

[1107] (z) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068742 and

[1108] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068742;

[1109] (aa) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068744 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068744;

[1110] (bb) a heavy chain comprising the amino acid sequence of the heavy chain f Pl-

[1111] 068746 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068746;

[1112] (cc) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068748 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068748;

[1113] (dd) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068750 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068750;

[1114] (ee) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068752 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068752;

[1115] (ff) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068754 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068754; (gg) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1116] 068761 E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of P1-068761 E55A;

[1117] (hh) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 H100G and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068761 H100G;

[1118] (ii) a heavy chain comprising (i) the amino acid sequence of the VH of P1-068761 E56N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of P1-068761 E56N;

[1119] (jj) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1120] 068761 E55A E56N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E55A_E56N;

[1121] (kk) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E30D and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of P1-068761 E30D;

[1122] (11) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1123] 068761 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E30D_E55A;

[1124] (mm) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E56N H100G and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E56N_H100G;

[1125] (nn) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1126] 068761 E30D H100G and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761 E30D H100G;

[1127] (oo) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E30D E56N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E30D_E56N;

[1128] (pp) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1129] 068761_E100fE and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-068761_E100fF;

[1130] (qq) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1131] 068761_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E55A_E100fE;

[1132] (rr) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1133] 068761_H100G_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761_H100G_E100fE;

[1134] (ss)a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E30D_E100fE;

[1135] (tt) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1136] 06876 l_E56N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-

[1137] 068761_E56N_E100fF;

[1138] (uu) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1139] 068761 E32Y and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of PI -068761 E32Y;

[1140] (vv) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1141] 068761 E32Y E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E32Y_E55A;

[1142] (ww) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E32Y E56N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-

[1143] 068761_E32Y_E56N;

[1144] (xx) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1145] 068761 E30D E32Y and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-

[1146] 068761_E30D_E32Y;

[1147] (yy) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1148] 068761 E32Y H100G and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068761 E32Y H100G;

[1149] (zz) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1150] 06876 l_E32Y_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-

[1151] 068761_E32Y_E100fE;

[1152] (aaa) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1153] 068767 D52N D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-

[1154] 068767_D52N_D102V;

[1155] (bbb) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767 D52N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of P1-068767 D52N;

[1156] (ccc) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1157] 068767 D52N E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068767_D52N_E55A;

[1158] (ddd) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1159] 068767 E55A D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-

[1160] 068767_E55A_D102V; (eee) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767 D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of P1-068767 D102V;

[1161] (fff) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767 E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of P1-068767 E55A;

[1162] (ggg) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767 E30D D52N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068767_E30D_D52N;

[1163] (hhh) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767 E30D D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068767_E30D_D102V;

[1164] (iii)a heavy chain comprising (i) the amino acid sequence of the VH of P1-068767 E30D and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of P1-068767 E30D;

[1165] (jjj)a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1166] 068767 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-

[1167] 068767_E30D_E55A;

[1168] (kkk) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1169] 068767_E100fF_D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068767_E100fE_D102V;

[1170] (lll)a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1171] 068767_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068767_E55A_E100fE; (mmm) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767_D52N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl- 068767_D52N_E100fF;

[1172] (nnn) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1173] 068767_E100fE and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-068767_E100fF; or

[1174] (ooo) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068767_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain comprising the light chain amino acid sequence of Pl-

[1175] 068767_E30D_E100fF.

[1176] Certain embodiments of this disclosure include anti-VISTA Abs comprising:

[1177] (a) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -061029 (SEQ ID NO: 67) and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -061029 (SEQ ID NO: 70);

[1178] (b) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-061015 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-061015;

[1179] (c) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068757 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068757;

[1180] (d) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068759 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068759;

[1181] (e) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068761 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068761; (f) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068763 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068763;

[1182] (g) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068765 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-068765;

[1183] (h) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068767 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068767;

[1184] (i) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-068769 and

[1185] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-068769;

[1186] (j) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-068771 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P 1 -068771 ;

[1187] (k) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-068773 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-068773;

[1188] (1) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068775 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-068775;

[1189] (m)a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-069059 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-069059;

[1190] (n) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069061 and

[1191] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -069061 ;

[1192] (o) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069063 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -069063; (p) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069065 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -069065;

[1193] (q) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069067 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -069067;

[1194] (r) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069069 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -069069;

[1195] (s) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069071 and

[1196] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -069071 ;

[1197] (t) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069073 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P 1 -069073 ;

[1198] (u) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -069075 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-069075;

[1199] (v) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-069077 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-069077;

[1200] (w) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-068736 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-068736;

[1201] (x) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068738 and

[1202] (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068738;

[1203] (y) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068740 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068740; (z) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068742 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068742;

[1204] (aa) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068744 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068744;

[1205] (bb) a heavy chain consisting of the amino acid sequence of the heavy chain f Pl- 068746 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068746;

[1206] (cc) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1207] 068748 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068748;

[1208] (dd) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068750 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068750;

[1209] (ee) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068752 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068752;

[1210] (ff) a heavy chain consisting of (i) the amino acid sequence of the VH of PI -068754 and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068754;

[1211] (gg) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1212] 068761 E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P1-068761 E55A;

[1213] (hh) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1214] 068761 H100G and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068761 H100G;

[1215] (ii) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1216] 068761 E56N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P1-068761 E56N; (jj) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1217] 068761 E55A E56N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E55A_E56N;

[1218] (kk) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1219] 068761 E30D and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P1-068761 E30D;

[1220] (11) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1221] 068761 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-

[1222] 068761_E30D_E55A;

[1223] (mm) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068761 E56N H100G and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E56N_H100G;

[1224] (nn) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1225] 068761 E30D H100G and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761 E30D H100G;

[1226] (oo) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1227] 068761 E30D E56N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E30D_E56N;

[1228] (pp) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068761_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-068761_E100fF;

[1229] (qq) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1230] 068761_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E55A_E100fE; (rr) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1231] 068761_H100G_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_H100G_E100fE;

[1232] (ss)a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1233] 068761_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E30D_E100fE;

[1234] (tt) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 06876 l_E56N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E56N_E100fF;

[1235] (uu) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1236] 068761 E32Y and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of PI -068761 E32Y;

[1237] (vv) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1238] 068761 E32Y E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E32Y_E55A;

[1239] (ww) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1240] 068761 E32Y E56N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E32Y_E56N;

[1241] (xx) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068761 E30D E32Y and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068761_E30D_E32Y;

[1242] (yy) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1243] 068761 E32Y H100G and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-

[1244] 068761 E32Y H100G;

[1245] (zz) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1246] 06876 l_E32Y_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-

[1247] 068761_E32Y_E100fE;

[1248] (aaa) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1249] 068767 D52N D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_D52N_D102V;

[1250] (bbb) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1251] 068767 D52N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P1-068767 D52N;

[1252] (ccc) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767 D52N E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-

[1253] 068767_D52N_E55A;

[1254] (ddd) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1255] 068767 E55A D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-

[1256] 068767_E55A_D102V;

[1257] (eee) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1258] 068767 D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P1-068767 D102V;

[1259] (fff) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1260] 068767 E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P1-068767 E55A;

[1261] (ggg) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1262] 068767 E30D D52N and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_E30D_D52N;

[1263] (hhh) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767 E30D D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-

[1264] 068767_E30D_D102V;

[1265] (iii)a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1266] 068767 E30D and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of P1-068767 E30D;

[1267] Gjj)aheavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1268] 068767 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_E30D_E55A;

[1269] (kkk) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767_E100fF_D102V and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_E 1 OOfF D 102 V;

[1270] (lll)a heavy chain consisting of (i) the amino acid sequence of the VH of Pl-

[1271] 068767_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-

[1272] 068767_E55A_E100fF;

[1273] (mmm) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767_D52N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl- 068767_D52N_E100fF;

[1274] (nnn) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767_E100fE and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-068767_E100fF; or (ooo) a heavy chain consisting of (i) the amino acid sequence of the VH of Pl- 068767_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 183, and a light chain consisting of the light chain amino acid sequence of Pl-

[1275] 068767_E30D_E100fF,

[1276] wherein the C-terminal amino acid of VH and the N-terminal amino acid of SEQ ID NO: 183 form a peptidic bond. ome embodiments, the disclosure contemplates anti-VISTA mAbs comprising:

[1277] a heavy chain consisting of the amino acid sequences of (i) a VH of (a) to (ooo) listed above, (ii) SEQ ID NO: 183, and (iii) a Lys residue, wherein the C-terminal amino acid of VH and the N-terminal amino acid of SEQ ID NO: 183 form a peptidic bond and wherein the C-terminal amino acid of SEQ ID NO: 183 is joined to the N-terminal of the

[1278] Lys; and

[1279] a light chain consisting of the light chain amino acid sequence of (a) to (ooo) listed above;

[1280] wherein the VH and light chain amino acid sequences are chosen from the same antibody species from among (a) to (ooo) listed above.

[1281] Further embodiments of this disclosure include anti-VISTA Abs comprising:

[1282] (a) a heavy chain comprising (i) the amino acid sequence of the VH of PI -061029 (SEQ ID NO: 67) and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-061029 (SEQ ID NO: 70);

[1283] (b) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-061015 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-061015;

[1284] (c) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068757 and

[1285] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068757;

[1286] (d) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068759 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-068759; a heavy chain comprising (i) the amino acid sequence of the VH of PI -068761 and

[1287] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068761;

[1288] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068763 and

[1289] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068763;

[1290] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068765 and

[1291] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068765;

[1292] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068767 and

[1293] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068767;

[1294] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068769 and

[1295] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068769;

[1296] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068771 and

[1297] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068771;

[1298] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068773 and

[1299] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068773;

[1300] a heavy chain comprising (i) the amino acid sequence of the VH of PI -068775 and

[1301] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068775;

[1302] a heavy chain comprising (i) the amino acid sequence of the VH of PI -069059 and

[1303] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069059;

[1304] a heavy chain comprising (i) the amino acid sequence of the VH of PI -069061 and

[1305] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069061; (o) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069063 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069063;

[1306] (p) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069065 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069065;

[1307] (q) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069067 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069067;

[1308] (r) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069069 and

[1309] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069069;

[1310] (s) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069071 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of P 1 -069071 ;

[1311] (t) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069073 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069073;

[1312] (u) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069075 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069075;

[1313] (v) a heavy chain comprising (i) the amino acid sequence of the VH of PI -069077 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -069077;

[1314] (w) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-068736 and

[1315] (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-068736;

[1316] (x) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068738 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-068738; (y) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068740 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068740;

[1317] (z) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068742 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068742;

[1318] (aa) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068744 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068744;

[1319] (bb) a heavy chain comprising the amino acid sequence of the heavy chain f Pl-

[1320] 068746 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068746;

[1321] (cc) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068748 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068748;

[1322] (dd) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068750 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068750;

[1323] (ee) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068752 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068752;

[1324] (ff) a heavy chain comprising (i) the amino acid sequence of the VH of PI -068754 and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068754;

[1325] (gg) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1326] 068761 E55A and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of P1-068761 E55A;

[1327] (hh) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1328] 068761 H100G and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068761 H100G; (ii) a heavy chain comprising (i) the amino acid sequence of the VH of P1-068761 E56N and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of P1-068761 E56N;

[1329] (jj) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E55A E56N and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1330] 068761_E55A_E56N;

[1331] (kk) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1332] 068761 E30D and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of P1-068761 E30D;

[1333] (11) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1334] 068761 E30D E55A and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1335] 068761_E30D_E55A;

[1336] (mm) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1337] 068761 E56N H100G and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E56N_H100G;

[1338] (nn) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E30D H100G and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl- 068761 E30D H100G;

[1339] (oo) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1340] 068761 E30D E56N and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1341] 068761_E30D_E56N;

[1342] (pp) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1343] 068761_E100fE and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-068761_E100fF; (qq) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1344] 068761_E55A_E100fF and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1345] 068761_E55A_E100fE;

[1346] (rr) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1347] 068761_H100G_E100fF and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1348] 068761_H100G_E100fE;

[1349] (ss)a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761_E30D_E100fF and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1350] 068761_E30D_E100fE;

[1351] (tt) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1352] 06876 l_E56N_E100fF and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1353] 068761_E56N_E100fF;

[1354] (uu) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1355] 068761 E32Y and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of PI -068761 E32Y;

[1356] (vv) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1357] 068761 E32Y E55A and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1358] 068761_E32Y_E55A;

[1359] (ww) a heavy chain comprising (i) the amino acid sequence of the VH of Pl- 068761 E32Y E56N and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1360] 068761_E32Y_E56N;

[1361] (xx) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1362] 068761 E30D E32Y and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1363] 068761_E30D_E32Y;

[1364] (yy) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1365] 068761 E32Y H100G and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1366] 068761 E32Y H100G;

[1367] (zz) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1368] 06876 l_E32Y_E100fF and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl- 068761_E32Y_E100fE;

[1369] (aaa) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1370] 068767 D52N D102V and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1371] 068767_D52N_D102V;

[1372] (bbb) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1373] 068767 D52N and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of P1-068767 D52N;

[1374] (ccc) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1375] 068767 D52N E55A and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl-

[1376] 068767_D52N_E55A;

[1377] (ddd) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1378] 068767 E55A D102V and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of Pl- 068767_E55A_D102V;

[1379] (eee) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1380] 068767 D102V and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of P1-068767 D102V; (fff) a heavy chain comprising (i) the amino acid sequence of the VH of Pl-

[1381] 068767 E55A and (ii) the amino acid sequence of SEQ ID NO: 184, and a light chain comprising the light chain amino acid sequence of P1-068767 E55A;

[1382] (ggg) a heavy chain comprising (i) the amino ac...

Claims

CLAIMS1. An isolated antibody that binds specifically to hVISTA in acidic conditions.

2. The isolated antibody of claim 1 , which binds specifically to hVISTA in acidicconditions, but not significantly in neutral or physiological conditions.

3. The isolated antibody of claim 1 or 2, wherein the antibody binds to hVISTA inacidic conditions with a KD that is at least 10 fold lower than its KD in neutral or physiological conditions.

4. The isolated antibody of any one of claims 1 to 3, wherein the antibody binds tohVISTA in acidic conditions with a KD that is at least 100 fold lower than its KD in neutral or physiological conditions.

5. The isolated antibody of any one of claims 1 -4, wherein the antibody binds tohVISTA in acidic conditions with a KD that is at least 1000 fold lower than its KD in neutral or physiological conditions.

6. The isolated antibody of any one of claims 1 -5, wherein the antibody binds tohVISTA in neutral or physiological conditions with a KD of 10"5M or more.

7. The isolated antibody of any one of claims 1 -6, wherein the antibody binds tohVISTA in neutral or physiological conditions with a KD of 10"4M or more.

8. The isolated antibody of any one of claims 1 -7, wherein the antibody binds tohVISTA in neutral or physiological conditions with a KD of 10"3M or more.

9. The isolated antibody of any one of claims 1 -8, wherein the antibody binds tohVISTA in acidic conditions with a KD of 10"7M or less.

10. The isolated antibody of any one of claims 1 -9, wherein the antibody binds tohVISTA in acidic conditions with a KD of 10"8M or less.1 1. The isolated antibody of any one of claims 1 - 10, wherein the antibody binds tohVISTA in acidic conditions with a KD of 10"9M or less.

12. The isolated antibody of any one of claims 1 - 1 1 , wherein the antibody binds tohVISTA in acidic conditions with a KD of 10"7or less and binds to hVISTA in neutral or physiological conditions with a KD of 10"4or more.

13. The isolated antibody of any one of claims 1-12, wherein the antibody binds to hVISTA in acidic conditions with a KD of 10"7or less and binds to hVISTA in neutral or physiological conditions with a KD of 10"5or more.

14. The isolated antibody of any one of claims 1-13, wherein the antibody binds tohVISTA in acidic conditions with a koff that is at least 5 fold lower than its k0ff in neutral or physiological conditions.

15. The isolated antibody of any one of claims 1-14, wherein the antibody binds tohVISTA in acidic conditions with a k0ff that is at least 10 fold lower than its koff in neutral or physiological conditions.

16. The isolated antibody of any one of claims 1-15, wherein the antibody binds tohVISTA in acidic conditions with a k0ff that is at least 50 fold lower than its koff in neutral or physiological conditions.

17. The isolated antibody of any one of claims 1-16, wherein the antibody binds tohVISTA in acidic conditions with a k0ff that is at least 100 fold lower than its koff in neutral or physiological conditions.

18. The isolated antibody of any one of claims 1-17, wherein the antibody binds tohVISTA in acidic conditions with a k0ff of 7 x 10"3s"1or less.

19. The isolated antibody of any one of claims 1-18, wherein the antibody binds tohVISTA in acidic conditions with a k0ff of 5 x 10"3s"1or less.

20. The isolated antibody of any one of claims 1-19 wherein the antibody binds tohVISTA in acidic conditions with a k0ff of 3 x 10"3s"1or less.

21. The isolated antibody of any one of claims 1-20, wherein the antibody binds tohVISTA in acidic conditions with a k0ff of 10"3s"1or less.

22. The isolated antibody of any one of claims 1-21, wherein the antibody binds tohVISTA in acidic conditions with a k0ff of 7 x 10"4s"1or less.

23. The isolated antibody of any one of claims 1-22, wherein the antibody binds tohVISTA in acidic conditions with a k0ff of 5x 10"4s"1or less.

24. The isolated antibody of any one of claims 1-23, wherein the antibody binds tohVISTA in acidic conditions with a k0ff of 3 x 10"4s"1or less.

25. The isolated antibody of any one of claims 1-24, wherein the antibody binds to hVISTA in acidic conditions with a k0ff of 10"4s"1or less.

26. The isolated antibody of any one of claims 1-25, wherein the antibody binds to hVISTA in acidic conditions with a k0ff of 7 x 10"5s"1or less.

27. The isolated antibody of any one of claims 1-26, wherein the antibody binds to hVISTA in acidic conditions with a k0ff of 5 x 10"5s"1or less.

28. The isolated antibody of any one of claims 1-21, wherein the antibody binds to hVISTA in acidic conditions with a k0ff of 3 x 10"5s"1or less.

29. The isolated antibody of any one of claims 1-28, wherein the antibody binds to hVISTA in acidic conditions with a k0ff of 10"5s"1or less.

30. The isolated antibody of any one of claims 1-29, wherein the antibody binds to hVISTA in neutral or physiological conditions with a k0ff of 10"3s"1or more.

31. The isolated antibody of any one of claims 1-30, wherein the antibody binds to hVISTA in neutral or physiological conditions with a k0ff of 3 x 10"3s"1or more.

32. The isolated antibody of any one of claims 1-31, wherein the antibody binds to hVISTA in neutral or physiological conditions with a k0ff of 5 x 10"3s"1or more.

33. The isolated antibody of any one of claims 1-32, wherein the antibody binds to hVISTA in neutral or physiological conditions with a k0ff of 7 x 10"3s"1or more.

34. The isolated antibody of any one of claims 1-33, wherein the antibody binds to hVISTA in neutral or physiological conditions with a k0ff of 10"2s"1or more.

35. The isolated antibody of any one of claims 1-34, wherein the antibody binds to hVISTA in neutral or physiological conditions with a k0ff of 3 x 10"2s"1or more.

36. The isolated antibody of any one of claims 1-35, wherein the antibody binds to hVISTA in neutral or physiological conditions with a k0ff of 5 x 10"2s"1or more.

37. The isolated antibody of any one of claims 1-36, wherein the antibody binds to hVISTA in neutral or physiological conditions with a k0ff of 7 x 10"2s"1or more.

38. The isolated antibody of any one of claims 1-37, wherein binding of the antibody to hVISTA in neutral or physiological conditions is not detectable, e.g., via SPR.

39. The isolated antibody of any one of claims 1-38, wherein the antibody binds to hVISTA in acidic conditions with a k0ff of 5 x 10"3s"1or less and in neutral or physiological conditions with a k0ff of 7 x 10"3s"1or more.

40. The isolated antibody of any one of claims 1-39, wherein the antibody binds tohVISTA in acidic conditions with a k0ff of 10"4s"1or less and in neutral or physiological conditions with a k0ff of 10"2s"1or more.

41. The isolated antibody of any one of claims 1-40, wherein the antibody binds tohVISTA in acidic conditions with a KD of 10"8M or less and a k0ff of 5 x 10"3s"1or less and in neutral of physiological conditions with a KD of 10"6M or more and a k0ff of 7 x 10"3s"1or more.

42. The isolated antibody of any one of claims 1-41, wherein the antibody binds tohVISTA in acidic conditions with a KD of 10"8M or less and a k0ff of 3 x 10"3s"1or less and in neutral of physiological conditions with a KD of 10"6M or more and a k0ff of 10"2s"1or more.

43. The isolated antibody of any one of claims 1-42, wherein the antibody binds tohVISTA in acidic conditions with a KD of 10"12to 10"8M and a k0ff of 10"4to 5 x 10"3s"1and in neutral of physiological conditions with a KD of 10"7to 10"4M and a k0ff of 3 x 10"3to 10"2s"1or more.

44. The isolated antibody of any one of claims 1-43, wherein the antibody binds tohVISTA in acidic conditions with a KD of 10"12to 10"8M and a k0ff of 10"4to 5 x 10"3s"1and in neutral of physiological conditions with a KD of 10"7to 10"4M and a k0ff of 3 x 10"3to 10"2s"1or more; and wherein the antibody binds to cyno VISTA with a KD of 10"7or less.

45. The isolated antibody of any one of claims 1-44, wherein the antibody binds tohVISTA with a KD that is at least 10 fold lower at pH 6.9 than at pH 7.4 and / or a KD that is at least 100 fold lower at pH 6.5 than at pH 7.4 and at least 1000 fold lower at pH 6.0 than at pH 7.4.

46. The isolated antibody of any one of claims 1-45, wherein the antibody binds to cyno VISTA.

47. The isolated antibody of claim 46, wherein the antibody binds to cyno VISTA with higher affinity in acidic conditions relative to physiologic conditions.

48. The isolated antibody of any one of claims 45-47, wherein the antibody binds to cyno VISTA in acidic conditions with a KD of 10"8or less and / or a k0ff of 10"2or less and in physiologic conditions with a KD of 10"6or more and / or a k0ff of 10"2or more.

49. The isolated antibody of any one of claims 1 -48, wherein acidic conditions areconditions having a pH of 6.5 or less.

50. The isolated antibody of any one of claims 1 -49, wherein acidic conditions areconditions having a pH of 6.0 to 6.5.

51. The isolated antibody of any one of claim 1 -50, wherein neutral conditions areconditions having a pH of 7.0.

52. The isolated antibody of any one of claims 1 -51 , wherein physiological conditions are conditions having a pH of 7.35 to 7.45.

53. The isolated antibody of any one of claims 1 -52, wherein physiological conditions are conditions having a pH of 7.4.

54. The isolated antibody of any one of claims 1 -53, wherein the antibody inhibits the binding of hVISTA to human T cells, such as human CD4+ T cells (an antagonist antibody).

55. The isolated antibody of claim 54, wherein the antibody inhibits the binding ofhVISTA to human T cells in conditions having a pH of less than pH 7.0.

56. The isolated antibody of any one of claims 1 -55, wherein the antibody inhibits the binding of hVISTA to huPSGL-1.

57. The isolated antibody of claim 56, wherein the antibody inhibits the binding ofhVISTA to huPSGL- 1 in conditions having a pH of less than pH 7.0.

58. The isolated antibody of anyone of claims 1 -57, wherein the antibody inhibits the binding of hVISTA to heparan sulfate proteoglycans.

59. The isolated antibody of claim 58, wherein the antibody inhibits the binding ofhVISTA to heparan sulfate proteoglycans in conditions having a pH of less than pH 7.0.

60. The isolated antibody of anyone of claims 55, 57 or 59, wherein a condition having a pH of less than pH 7.0 is a tumor or any diseased area having a pH of less than pH 7.0 in a subject and in which an immune stimulation is desired.

61. The isolated antibody of any one of claims 1-60, wherein the antibody stimulates T cell activation.

62. The isolated antibody of claim 61, wherein the antibody stimulates T cell activation in conditions having a pH of less than pH 7.0.

63. The isolated antibody of any one of claims 1-62, wherein the antibody reducesVISTA mediated cell-cell adhesion.

64. The isolated antibody of any one of claims 1-53, wherein the antibody stimulates the activity of VISTA (an agonist antibody).

65. The isolated antibody of any one of claims 1-53 and 64, wherein the antibodystimulates the binding of hVISTA to human T cells, such as human CD4+ T cells.

66. The isolated antibody of claim 65, wherein the antibody stimulates the binding of hVISTA to human T cells in conditions having a pH of less than pH 7.0.

67. The isolated antibody of any one of claims 1-53 and 64-66, wherein the antibody stimulates the binding of hVISTA to huPSGL-1.

68. The isolated antibody of claim 67, wherein the antibody stimulates the binding of hVISTA to huPSGL-1 in conditions having a pH of less than pH 7.0.

69. The isolated antibody of anyone of claims 1-53 and 64-68, wherein the antibodystimulates the binding of hVISTA to heparan sulfate proteoglycans.

70. The isolated antibody of claim 69, wherein the antibody stimulates the binding of hVISTA to heparan sulfate proteoglycans in conditions having a pH of less than pH 7.0.

71. The isolated antibody of anyone of claims 66, 68 and 70, wherein a condition having a pH of less than pH 7.0 is an autoimmune (e.g., rheumatoid arthritis and lupus) milieu, an inflammation site, or any diseased area having a pH of less than pH 7.0 in a subject and in which an immune inhibition is desired.

72. The isolated antibody of any one of claims 1-71, wherein the antibody has a mean residence time of at least 500 days in Cynomolgus macaques.

73. The isolated antibody of any one of claims 1-72, wherein the antibody is not significantly binding to VISTA positive cells, e.g., neutrophils, in the peripheral blood of a subject to whom it is administered.

74. The isolated antibody of any one of claims 1-73, wherein the antibody is notsignificantly depleting VISTA positive cells, e.g., neutrophils, in peripheral blood of a subject to whom it is administered.

75. The antibody of any one of claims 1-74, wherein the antibody has been engineered to bind to hVISTA at acidic pH, but not at neutral or physiological pH.

76. The antibody of claim 75, wherein the antibody has been engineered by replacing from 1-8 amino acids in VH CDRl, CDR2 and / or CDR3 with a glutamic acid, aspartic acid or histidine residue.

77. The antibody of any one of claims 1-63 and 72-76, wherein the antibody comprises VH CDRl, CDR2 and / or CDR3 of PI -061029 or a variant thereof comprising 1 to 6 or 1 to 8 amino acid differences in CDRl, CDR2 and / or CDR3 relative to PI -061029, wherein at most 1, 2 or 3 amino acid variations are present in any one CDR.

78. The antibody of claim 77, wherein the antibody comprises VH CDRl, CDR2 and CDR3 of Pl-061029 or a variant thereof comprising 1 to 6 or 1 to 8 amino acid differences in CDRl, CDR2 and / or CDR3 relative to Pl-061029.

79. The antibody of claim 77 or 78, wherein an amino acid variation is a substitution to a glutamic acid residue (E), aspartic acid residue (D) or a histidine residue (H).

80. The antibody of any one of claims 77-79, wherein the antibody comprises- a CDRl comprising GFTX1X2DX3AMH, wherein Xi is D or L, X2is E or D and X3 is E or Y (SEQ ID NO: 463);- a CDR2 comprising GIX4WX5 SX6X7IGYAD S VKG, wherein X4is D or N, Xs is D or N, Xe is D, E, H or A and X7 is D, E, H or N (SEQ ID NO: 464); and / or- a CDR3 comprising VPGYSX8GWIDAX9DXio, wherein X8is E, H or G, X9 is E, D or F and X10 is D, E or V (SEQ ID NO: 465).

81. The antibody of claim 80, wherein the antibody comprises- a CDRl comprising GFTX1X2DX3AMH, wherein Xi is D or L, X2is E or D and X3 is E or Y (SEQ ID NO: 463);- a CDR2 comprising GIX4WX5 SX6X7IGYAD S VKG, wherein X4is D or N, Xs is D or N, Xe is D, E, H or A and X7 is D, E, H or N (SEQ ID NO: 464); and- a CDR3 comprising VPGYSX8GWIDAX9DXio, wherein X8is E, H or G, X9 is E, D or F and X10 is D, E or V (SEQ ID NO: 465).

82. The antibody of claim 80 or 81, wherein X3 is E and X9 is E.

83. The antibody of any one of claims 80-82, wherein X2 is E, X7 is E, and / or X8is H.

84. The antibody of claim 83, wherein two or more of X2 is E, X7 is E, and X8is H are met.

85. The antibody of claim 84, wherein X2 is E, X7 is E and X8is H.

86. The antibody of any one of claims 80-85, wherein X6is E.

87. The antibody of any one of claims 80-85, wherein X6is A.

88. The antibody of any one of claims 80-86, wherein Xi is L, X4is N, X5 is N and / or X10 is V.

89. The antibody of claim 88, wherein two or more of Xi is L, X4is N, X5 is N and / or90. The antibody of claim 89, wherein three or more of Xi is L, X4is N, X5 is N and / or91. The antibody of claim 90, wherein Xi is L, X4is N, X5 is N and / or X10 is V.

92. The antibody of any one of claims 80-91, wherein X10 is D.

93. The antibody of any one of claims 80-92, wherein X9 is E.

94. The antibody of any one of claims 80-93, wherein X2 is E, X4is D and / or X6is E.

95. The antibody of claim 94, wherein two or more of X2 is E, X4is D and / or X6is E are met.

96. The antibody of claim 95, wherein X2 is E, X4is D and X6is E.

97. The antibody of any one of claims 80-96, wherein Xi is L, X3 is Y, X5 is N, X7 is N and / or X8is G.

98. The antibody of claim 97, wherein two or more of Xi is L, X3 is Y, X5 is N, X7 is N and / or X8is G are met.

99. The antibody of claim 98, wherein three or more of Xi is L, X3 is Y, X5 is N, X7 is N and / or X8is G are met.

100. The antibody of claim 99, wherein four or more of Xi is L, X3 is Y, Xs is N, X7 is N and / or X8is G are met.

101. The antibody of claim 100, wherein Xi is L, X3 is Y, X5 is N, X7 is N and X8is G.

102. The antibody of any one of claims 77-101, wherein the antibody comprises VH CDR1, CDR2 and / or CDR3 of Pl-061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl-068773, Pl- 068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075,Pl-069077, P1-068761_E55A, Pl- 068761_H100G, PI -068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, Pl- 068761 E30D E55A, P1-068761_E56N_H100G,P1-068761_E30D_H100G, or Pl- 068761 E30D E56N, PI -06876 l ElOOfF, Pl-068761_E55A_E100fE, Pl- 068761_H100G_E100fE, Pl-068761_E30D_E100fE, Pl-068761_E56N_E100fF, Pl- 068761_E32Y, P1-068761_E32Y_E55A, PI -068761_E32Y_E56N, Pl-068761 E30D E32Y, PI -068761 E32Y H100G, or PI -06876 l_E32Y_E100fF, Pl- 068767_D52N_D102V, P1-068767_D52N, P1-068767_D52N_E55A, Pl- 068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, Pl- 068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, Pl- 068767_E30D_E55A, Pl-068767_E100fF_D 102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fE, Pl-068767_E100fF or Pl-068767_E30D_E100fF.

103. The antibody of claim 102, wherein the antibody comprises VH CDR1, CDR2 and CDR3 of Pl-061029, Pl-068757, Pl-068759, Pl-068761, Pl-068763, Pl- 068765, Pl-068767, Pl-068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl-069069, Pl-069071, Pl- 069073, Pl-069075, Pl-069077, Pl-069077, P1-068761_E55A, PI -068761 H100G, PI -068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, Pl-068761 E30D E55A, P1-068761_E56N_H100G,P1-068761_E30D_H100G, or Pl- 068761 E30D E56N, PI -06876 l ElOOfF, Pl-068761_E55A_E100fE, Pl- 068761_H100G_E100fE, Pl-068761_E30D_E100fE, Pl-068761_E56N_E100fF, Pl- 068761_E32Y, P1-068761_E32Y_E55A, PI -068761_E32Y_E56N, Pl-068761 E30D E32Y, PI -068761 E32Y H100G, Pl-068761_E32Y_E100fF, Pl- 068767_D52N_D102V, P1-068767_D52N, P1-068767_D52N_E55A, Pl- 068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, Pl- 068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, Pl- 068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF or Pl-068767_E30D_E100fF.

104. The antibody of any one of claims 77-103, wherein the antibody comprises VL CDR1, CDR2 and CDR3 of the VL of PI -061029.

105. The antibody of any one of claims 1-63 and 72-104, wherein the antibody comprises a VH comprising an amino acid sequence that is at least 90%, 95%, 97%, 98% or 99% identical to that of Pl-061029, Pl-068757, Pl-068759, Pl-068761, Pl- 068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl-069069, Pl- 069071, Pl-069073, Pl-069075, Pl-069077, Pl-069077, P1-068761_E55A, Pl- 068761_H100G, PI -068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, Pl- 068761 E30D E55A, P1-068761_E56N_H100G,P1-068761_E30D_H100G, or Pl- 068761 E30D E56N, PI -06876 l ElOOfF, Pl-068761_E55A_E100fE, Pl- 068761_H100G_E100fE, Pl-068761_E30D_E100fE, Pl-068761_E56N_E100fF, Pl- 068761_E32Y, P1-068761_E32Y_E55A, PI -068761_E32Y_E56N, Pl-068761 E30D E32Y, PI -068761 E32Y H100G, Pl-068761_E32Y_E100fF, Pl- 068767_D52N_D102V, P1-068767_D52N, P1-068767_D52N_E55A, Pl- 068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, Pl- 068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, Pl- 068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fE, Pl-068767_E100fF or Pl-068767_E30D_E100fF.

106. The antibody of any one of claims 1-63 and 72-104, wherein the antibody comprises a VH comprising the amino acid sequence of the VH of Pl-061029, Pl- 068757, Pl-068759, Pl-068761, Pl-068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl-068773, Pl-068775, Pl-069059, Pl-069061, Pl-069063, Pl- 069065, Pl-069067, Pl-069069, Pl-069071, Pl-069073, Pl-069075, Pl-069077,Pl-069077, P1-068761 E55A, PI -068761 H100G, PI -068761 E56N, Pl- 068761_E55A_E56N, P1-068761_E30D, P1-068761_E30D_E55A, Pl- 068761_E56N_H100G,P1-068761_E30D_H100G, or P1-068761 E30D E56N, Pl- 068761_E100fF, Pl-068761_E55A_E100fF, PI -06876 l HlOOG ElOOfF, Pl- 068761_E30D_E100fF, Pl-068761_E56N_E100fF, PI -068761 E32Y, Pl- 068761_E32Y_E55A, PI -068761_E32Y_E56N, P1-068761_E30D_E32Y, Pl- 068761 E32Y H100G, or PI -06876 l_E32Y_E100fF, P1-068767_D52N_D102V, P1-068767_D52N, P1-068767_D52N_E55A, P1-068767_E55A_D102V, Pl- 068767_D102V, P1-068767_E55A, P1-068767_E30D_D52N, Pl- 068767_E30D_D102V, P1-068767_E30D, P1-068767_E30D_E55A, Pl- 068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl-068767_D52N_E100fF, Pl- 068767_E100fE or Pl-068767_E30D_E100fF.

107. The antibody of any one of claims 1-106, wherein the antibody comprises a VL comprising an amino acid sequence that is at least 90%, 95%, 97%, 98% or 99% identical to that of PI -061029.

108. The antibody of claim 107, wherein the antibody comprises the VL of Pl- 061029.

109. The antibody of any one of claims 1-63 and 72-76, wherein the antibodycomprises VH CDR1, CDR2 and / or CDR3 of Pl-061015 or a variant thereof comprising 1-6 or 1-8 amino acid differences in CDR1, CDR2 and / or CDR3 relative to Pl-061015, wherein at most 1, 2 or 3 amino acid variations are present in any one CDR.

110. The antibody of claim 109, wherein the antibody comprises VH CDR1, CDR2 and CDR3 of Pl-061015 or a variant thereof comprising 1-6 amino acid differences in CDR1, CDR2 and / or CDR3 relative to the Pl-061015, wherein at most 1, 2 or 3 amino acid variations are present in any one CDR.

111. The antibody of claims 108 or 109, wherein an amino acid variation is asubstitution to a glutamic acid residue (E), aspartic acid residue (D) or a histidine residue (H).

112. The antibody of any one of claims 108-111, wherein the antibody comprises- a CDRl comprising GFTFX1X2X3MH, wherein Xi is E, D, H or S; X2 is H or Y; and X3 is D or A (SEQ ID NO: 466);- a CDR2 comprising X4X5WX6DGSX7X8X9X10ADSVKG, wherein X4is E, H or I; X5is D or I; X6is D or Y; X7is D or N; Xs is D, H or K; X9is D, H or Y; and X10 is E or Y (SEQ ID NO: 467); and / or- a CDR3 comprising DX11X12FYX13X14YYDFX15, wherein X11 is E or S; X12 is E or G; Xi3 is D, E or S; Xi4is D or S; and X15 is D, E or Y (SEQ ID NO: 468).

113. The antibody of any one of claims 108-112, wherein the antibody comprises- a CDRl comprising GFTFX1X2X3MH, wherein Xi is E, D, H or S; X2 is H or Y; and X3 is D or A (SEQ ID NO: 466);- a CDR2 comprising X4X5WX6DGSX7X8X9X10ADSVKG, wherein X4is E, H or I; X5is D or I; X6is D or Y; X7is D or N; Xs is D, H or K; X9is D, H or Y; and X10 is E or Y (SEQ ID NO: 467); and- a CDR3 comprising DX11X12FYX13X14YYDFX15, wherein X11 is E or S; X12 is E or G; Xi3 is D, E or S; Xi4is D or S; and X15 is D, E or Y (SEQ ID NO: 468).

114. The antibody of anyone of claims 98-102, wherein the antibody comprises VH CDRl, CDR2 and / or CDR3 of Pl-061015, Pl-068736, Pl-068738, Pl-068740, Pl- 068742, Pl-068744, Pl-068748, Pl-068750, Pl-068752 or Pl-068754.

115. The antibody of claim 114, wherein the antibody comprises VH CDRl, CDR2 and CDR3 of Pl-061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl- 068744, Pl-068748, Pl-068750, Pl-068752 or Pl-068754.

116. The antibody of any one of claims 98-115, wherein the antibody comprises VL CDRl, CDR2 and CDR3 of the VL of Pl-061015.

117. The antibody of any one of claims 98-116, wherein the antibody comprises a VH comprising an amino acid sequence that is at least 90%, 95%, 97%, 98% or 99% identical to that of Pl-061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl- 068744, Pl-068748, Pl-068750, Pl-068752 or Pl-068754.

118. The antibody of any one of claims 98-117, wherein the antibody comprises a VH comprising the amino acid sequence of the VH of Pl-061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068748, Pl-068750, Pl-068752 or Pl-068754.

119. The antibody of any one of claims 98-118, wherein the antibody comprises a VL comprising an amino acid sequence that is at least 90%, 95%, 97%, 98% or 99% identical to that of P 1 -061015.

120. The antibody of claim 119, wherein the antibody comprises a VL comprising the amino acid sequence of Pl-061015.

121. The isolated antibody of any one of claims 1-120, wherein the antibody binds at or near the histidine rich region of hVISTA.

122. The isolated antibody of claim 121, wherein the antibody binds at or near the histidine rich region of hVISTA in conditions having a pH of 6.0-6.5.

123. The isolated antibody of any one of claims 1-122, wherein the antibodycompetes or cross-competes for binding to hVISTA with one or more antibodies comprising the VH and VL of PI -061029, Pl-068757, Pl-068759, Pl-068761, Pl- 068763, Pl-068765, Pl-068767, Pl-068769, Pl-068771, Pl-068773, Pl-068775,Pl-069059, Pl-069061, Pl-069063, Pl-069065, Pl-069067, Pl-069069, Pl- 069071, Pl-069073, Pl-069075, Pl-069077, Pl-069077, P1-068761_E55A, Pl- 068761_H100G, PI -068761_E56N, P1-068761_E55A_E56N, P1-068761_E30D, Pl- 068761 E30D E55A, P1-068761_E56N_H100G,P1-068761_E30D_H100G, or Pl- 068761_E30D_E56N, PI -068761 ElOOfF, Pl-068761_E55A_E100fF, Pl-068761_H100G_E100fF, Pl-068761_E30D_E100fF, Pl-068761_E56N_E100fF, Pl- 068761_E32Y, P1-068761_E32Y_E55A, PI -068761_E32Y_E56N, Pl- 068761 E30D E32Y, PI -068761 E32Y H100G, Pl-068761_E32Y_E100fF, Pl- 068767_D52N_D102V, P1-068767_D52N, P1-068767_D52N_E55A, Pl- 068767_E55A_D102V, P1-068767_D102V, P1-068767_E55A, Pl-068767_E30D_D52N, P1-068767_E30D_D102V, P1-068767_E30D, Pl- 068767_E30D_E55A, Pl-068767_E100fF_D102V, Pl-068767_E55A_E100fF, Pl- 068767_D52N_E100fF, Pl-068767_E100fF, Pl-068767_E30D_E100fF, Pl-061015, Pl-068736, Pl-068738, Pl-068740, Pl-068742, Pl-068744, Pl-068748, Pl-068750, Pl-068752 or Pl-068754.

124. The antibody of any one of claims 1-123, wherein the antibody does not bind significantly to hVISTA, in which one or more of the following amino acid residues have been mutated: T35, Y37, K38, T39, Y41, R54, T61, F62, Q63, L65, H66, L67, H68, H69, F97, LI 15, VI 17, 1119, H121, H122, S124, E125, R127.

125. An antibody that binds to hVISTA consisting of SEQ ID NO: 1 or 2, but does not bind significantly to hVISTA, in which one or more of the following amino acid residues have been mutated: T35, Y37, K38, T39, Y41, R54, T61, F62, Q63, L65, H66, L67, H68, H69, F97, LI 15, VI 17, 1119, H121, H122, S124, E125, R127.

126. The antibody of any one of claims 1-125, wherein the antibody does not bind significantly to hVISTA, in which 2, 3, 4, 5 or more of the following amino acid residues have been mutated: T35, Y37, K38, T39, Y41, R54, T61, F62, Q63, L65, H66, L67, H68, H69, F97, LI 15, VI 17, 1119, H121, H122, S124, E125, R127.

127. The antibody of any one of claims 124-126, wherein the antibody does not bind to a hVISTA in which one or more of the following residues have been mutated to one of the corresponding residue shown in Table 15.

128. The isolated antibody of any one of claims 1-127, wherein the antibody has an isoelectric point (pi) between 6.5 and 6.8, as measured, e.g., by icIEF.

129. The isolated antibody of any one of claims 1-128, wherein the antibodyexhibits low aggregation, e.g., an aggregation that is similar or lower than that of Ό29, '761 or '767, e.g., as determined in the Examples.

130. The isolated antibody of any one of claims 1-129, wherein the antibodyexhibits a viscosity that is similar or lower than that of '029, '761 or '767, e.g., as determined in the Examples.

131. The isolated antibody of any one of claims 1-130, wherein the antibodyexhibits a hydrodynamic radius that is similar or lower than that of '029, '761 or'767, e.g., as determined in the Examples.

132. The isolated antibody of any one of claims 1-131, wherein the antibodyexhibits a Tml that is similar or higher than that of '029, '761 or '767, e.g., as determined in the Examples.

133. The isolated antibody of any one of claims 1-132, wherein the antibody exhibits an amount of high molecular weight species that is similar to or lower than that of '029, '761 or '767, e.g., as determined in the Examples.

134. The isolated antibody of any one of claims 1-133, which is an IgG antibody.

135. The isolated antibody of claim 134, which is an IgGl, IgG2 or IgG4 antibody(IgG4 optionally with S228P).

136. The isolated antibody of any one of claims 1-135, wherein the antibody is an effectorless antibody.

137. The isolated antibody of claim 136, wherein the constant region comprises 1-5 mutations in a wild type heavy chain constant region that reduce the effector function of the antibody.

138. The isolated antibody of any one of claims 1-137, wherein the constant region of the antibody is IgGl .3, IgGl . l or is an IgGl with a P238K substitution.

139. The isolated antibody of any one of claims 1-135, wherein the antibody has effector function.

140. The isolated antibody of claim 139, wherein the antibody is afucosylated (e.g., an afucosylated IgGl antibody).

141. The isolated antibody of claim 139 or 140, wherein the constant regioncomprises 1-5 mutations that enhance the effector function of the antibody.

142. The isolated antibody of any one of claims 1- 141, which is a full lengthantibody.

143. The isolated antibody of any one of claims 1-141, which is an antigen binding fragment of the antibody.

144. The isolated antibody of anyone of claims 1-143, which is a multimeric (e.g., dimeric or trimeric) antibody.

145. The isolated antibody of anyone of claims 1-144, which is linked (e.g.,covalently) to another molecule.

146. The isolated antibody of claim 145, wherein the other molecule is a label.

147. The isolated antibody of claim 145 or 146, wherein the other molecule is a peptide.

148. The isolated antibody of anyone of claims 1-147, which is an antibody drug conjugate (ADC).

149. An isolated nucleic acid encoding an antibody of anyone of claims 1-148.

150. An isolated nucleic acid encoding the heavy chain and / or the light chain of an antibody of anyone of claims 1-149.

151. A composition comprising a nucleic acid encoding the heavy chain of an antibody of anyone of claims 1-150 and a nucleic acid encoding the light chain of the antibody.

152. A cell comprising the isolated nucleic acid of anyone of claims 149-151.

153. A method of preparing an antibody, comprising culturing the cell of claim 152 in conditions under which the antibody is expressed.

154. A composition comprising an isolated antibody, nucleic acid, composition or cell of anyone of claims 1-152 and a pharmaceutically acceptable carrier.

155. The composition of claim 154, comprising a second therapeutic agent.

156. The composition of claim 155, wherein the second therapeutic agent is an immunostimulatory agent.

157. The composition of claim 156, wherein the immunostimulating agent is an antagonist of an immunosuppressive molecule, e.g., the PD-1 / PD-L1, a CTLA-4 and LAG-3, or an agonist of an immunostimulating molecule, e.g., GITR and OX40.

158. A method of treating a subject having cancer, comprising administering to the subject a therapeutically effective amount of a composition or isolated antibody of any one of claims 1-152 and 154-157 that stimulates an immune response and / or is a VISTA antagonist antibody.

159. The method of claim 158, wherein the subject has VISTA positive cells in a tumor of the cancer.

160. The method of claim 159, wherein cells are VISTA positive infiltratinglymphocytic (e.g., T cells) or myelomonocytic cells.

161. The method of anyone of claims 158-160, wherein the subject is first tested for the presence of VISTA positive cells in a tumor.

162. The method of anyone of claims 158-161, wherein the method further comprises administering a second therapy.

163. The method of claim 162, wherein the second therapy is radiotherapy, surgery or administration of a second agent.

164. The method of claim 163, wherein the second therapy is a second agent and the second agent is an immunostimulatory agent.

165. The method of claim 164, wherein the immunostimulatory agent is anantagonist of an immunosuppressive molecule, e.g., the PD-1 / PD-L1, an CTLA-4 and LAG-3, or an agonist of an immunostimulating molecule, e.g., GITR and OX40.

166. A method of treating an infectious disease (e.g., viral disease) in a subject, comprising administering to the subject a therapeutically effective amount of a composition or isolated antibody of any one of claims 1-152 and 154-157 that stimulates an immune response and / or is a VISTA antagonist.

167. A method of treating an inflammation, an inflammatory condition, andautoimmune disease, graft versus host disease or a disease that benefits from reducing an immune response, comprising administering to the subject a therapeutically effective amount of a composition or isolated antibody of any one of claims 1-152 and 154-157 that inhibits an immune response, e.g., T cell activation or is a VISTA agonist.

168. A method for identifying an Ab that binds to hVISTA-ECD at pH 6.5 or less with a KD of 10"7M or less, comprising contacting a test Ab or a plurality of test Abs with a polypeptide comprising hVISTA-ECD or a fragment thereof comprising the IgV domain of hVISTA-ECD or comprising amino acids 20-95, 20-70, 35-70-127, or 35-127 of SEQ ID NO:2 at pH 6.5 or less, and selecting the test Ab or Abs that bind to the polypeptide with a KD of 10"7M or less.

169. A method for identifying an Ab that binds to hVISTA-ECD at pH 6.5 or less with a koff of 5 x 10"3sec"1or less, comprising contacting a test Ab or a plurality of test Abs with a polypeptide comprising hVISTA-ECD or a fragment thereof comprising the IgV domain of hVISTA-ECD or comprising amino acids 20-95, 20-70, 35-70, or 35-127 of SEQ ID NO:2 at pH 6.5 or less, and selecting the test Ab or Abs that bind to the polypeptide with a k0ff of 5 x 10"3sec"1or less.

170. A method for identifying an Ab that specifically binds to hVISTA-ECD at pH 6.5 with similar affinity at pH 7.0 comprising:a. contacting a test Ab or plurality of test Abs at pH 6.5 with a polypeptidecomprising hVISTA-ECD or a fragment thereof comprising the IgV domain of hVISTA-ECD or comprising amino acids 20-95, 20-70, or 35-70, or 35-127 of SEQ ID NO:2;b. contacting the test Ab or plurality of test Abs at pH 7.0 with the polypeptide of (a); andc. selecting a test Ab if it binds to the polypeptide with a KD of 10"7M or less at pH 6.5 and at pH 7.0.

171. A method for identifying an Ab that binds with higher affinity to hVISTA- ECD at pH 6.5 than at pH 7.0 comprising:a. contacting a test Ab or plurality of test Abs at pH 6.5 with a polypeptidecomprising hVISTA-ECD or a fragment thereof comprising the IgV domain of hVISTA-ECD or comprising amino acids 20-95, 20-70, 35-70, or 35-127 of SEQ ID NO:2;b. contacting the test Ab or plurality of test Abs at pH 7.0 with the polypeptide of (a); andc. selecting a test Ab if it binds to the polypeptide with a KD or k0ff at least 2-fold lower at pH 6.5 than at pH 7.0.

172. A method for identifying an Ab that specifically binds to hVISTA-ECD for use in treating cancer, comprisingc. identifying Abs that specifically bind to hVISTA-ECD at pH 6.5 or less, such as according to the methods of claims 168-171; andd. selecting the Abs of (a) that trigger or enhance an immune response in a tumor model or that inhibit tumor growth at pH 6.5 or less.

173. The method of claim 172, wherein step (b) comprises measuring T cellactivity.

174. The method of claim 172 or 173, further comprising measuring the anti-tumor effect of the Ab.

175. A method for improving the anti-tumor efficacy of an Ab that binds tohVISTA-ECD, comprisinga. Providing an Ab that binds to hVISTA-ECD at pH 6.5 or less with an affinity that is less than a desired value;b. substituting 1 to 5 amino acid residues in the heavy or light chain of the Ab with a different amino acid residue, wherein the 1 to 5 amino acid residues are contact residues with hVISTA-ECD;e. Determining if the Ab obtained in (b) has higher affinity for hVISTA-ECD at pH 6.5 or less relative to the Ab of (a); andf. Repeating steps (a) - (c), for a number of rounds sufficient to obtain an Ab that binds to hVISTA-ECD at pH 6.5 or less with a KD of 10"7M or less.

176. A method for improving the anti -tumor efficacy of an Ab that binds tohVISTA-ECD, comprising:a. Providing an Ab that binds to hVISTA-ECD at pH 6.5 or less with an affinity that is less than a desired value;b. Preparing a library of variants of the Ab of (a), wherein each variantcomprises a substitution of 1 to 5 amino acid residues in the heavy or light chain of the Ab with a different amino acid residue, wherein the 1 to 5 amino acid residues are contact residues with hVISTA-ECD;c. Selecting Abs of the library of variants of (b) that bind to hVISTA-ECD at pH 6.5 or less with a KD of 10"7M or less; andd. Testing the anti-tumor efficacy of the Abs of (c) in a tumor model.

177. A method for improving the pharmacokinetics of an antibody that binds to human VISTA ECD, comprising enhancing the ability of the antibody to bind to humanVISTA in acidic conditions, e.g., equal to or lower than pH 6.5.

178. A method for selecting an antibody that binds to human VISTA and having an extended half-life (good pharmacokinetic properties), wherein the method comprises selecting an antibody that binds to human VISTA in acidic conditions, e.g., equal to or lower than pH 6.5.

179. A method for improving the efficacy of antibodies that bind to hVISTA, comprising increasing the number of aspartic acid, glutamic acid and / or histidine residues in one or more VH CDRs of the antibody, to enhance binding of the antibody to hVISTA at acidic pH.

180. A method for isolating antibodies that bind to hVISTA and have a long half- life in human blood and / or stimulate T cells in a tumor environment, comprising screening a library of antibodies binding to hVISTA for those that bind at acidic pH, but not at neutral pH.

181. The method of anyone of claims 168-180, comprising counter selecting for those antibodies that bind at physiological pH.

182. The method of any one of claims 168-181, further comprising selectingantibodies that are either a VISTA antagonist or a VISTA agonist.

183. The method of any one of claims 168-182, comprising selecting for those antibodies that inhibit the interaction between VISTA and a VISTA co-receptor and / or the interation between VISTA and T cells or myelomonocytic cells.

184. The method of any one of claims 168-183, further comprising selectingantibodies that have one or more of the properties of PI -068761 or PI -068767.

185. A method of detecting VISTA in a sample, comprising contacting the sample with a VISTA antibody of any one of claims 1-148.

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