T-cell modulatory multimeric polypeptides and methods of use thereof

Abstract

The present disclosure provides variant immunomodulatory polypeptides, and fusion polypeptides comprising the variant immunomodulatory peptides. The present disclosure provides T-cell modulatory multimeric polypeptides, and compositions comprising same, where the T-cell modulatory multimeric polypeptides comprise a variant immunomodulatory polypeptide of the present disclosure. The present disclosure provides nucleic acids comprising nucleotide sequences encoding the T-cell modulatory multimeric polypeptides, and host cells comprising the nucleic acids. The present disclosure provides methods of modulating the activity of a T cell; the methods comprise contacting the T cell with a T-cell modulatory multimeric polypeptide of the present disclosure.

What is claimed is: 
     
         1 . A variant IL-2 polypeptide comprising an amino acid sequence having at least 85% amino acid sequence identity to set forth in SEQ ID NO:1,
 wherein the variant IL-2 polypeptide has one or more amino acid substitutions relative to set forth in SEQ ID NO:1, and   wherein the variant IL-2 polypeptide exhibits reduced binding affinity to an IL-2 receptor (IL2R) comprising alpha, beta, and gamma polypeptides having amino acid sequences depicted in  FIG. 3A-3C , compared to the binding affinity of the IL-2 amino acid sequence set forth in one of SEQ ID NO:1 for the IL2R.   
     
     
         2 . The variant IL2 polypeptide of  claim 1 , wherein the variant comprises a substitution of one or more of E15, H16, D20, F42, Y45, and Q126. 
     
     
         3 . The variant IL2 polypeptide of  claim 1  or  claim 2 , wherein the variant immunomodulatory polypeptide exhibits from less than 10% to less than 50% of the binding affinity exhibited by the IL2 amino acid sequence set forth in SEQ ID NO:1 for the IL2R. 
     
     
         4 . The variant IL2 polypeptide of any one of  claims 1 - 3 , wherein the variant comprises substitutions of F42 with Ala, Gly, Val, Ile, or Leu. 
     
     
         5 . The variant IL2 polypeptide of any one of  claims 1 - 3 , wherein the variant comprises substitutions of F42 and D20, or substitutions of F42 and H16. 
     
     
         6 . The variant IL2 polypeptide of any one of  claims 1 - 3 , wherein the variant comprises substitutions of F42, D20, and Y45; or where the variant comprises substitutions of F42, H16, and Q126. 
     
     
         7 . A multimeric polypeptide comprising:
 a) a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope; 
 ii) a first major histocompatibility complex (MHC) polypeptide; and 
   b) a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) a second MHC polypeptide; and 
 ii) optionally an immunoglobulin (Ig) Fc polypeptide or a non-Ig scaffold, 
   wherein the multimeric polypeptide comprises one or more immunomodulatory domains, wherein the one or more immunomodulatory domain is:
 A) at the C-terminus of the first polypeptide; 
 B) at the N-terminus of the second polypeptide; 
 C) at the C-terminus of the second polypeptide; or 
 D) at the C-terminus of the first polypeptide and at the N-terminus of the second polypeptide, and 
   wherein at least one of the immunomodulatory domains is a variant of a naturally occurring costimulatory protein, and wherein the variant exhibits a reduced affinity for its counterpart costimulatory protein as compared to the affinity of the naturally occurring costimulatory protein for the counterpart costimulatory protein.   
     
     
         8 . A multimeric polypeptide comprising:
 a) a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope; 
 ii) a first major histocompatibility complex (MHC) polypeptide; and 
   b) a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) a second MHC polypeptide; and 
 ii) optionally an immunoglobulin (Ig) Fc polypeptide or a non-Ig scaffold, 
   wherein the multimeric polypeptide comprises one or more immunomodulatory domains, wherein the one or more immunomodulatory domain is:
 A) at the C-terminus of the first polypeptide; 
 B) at the N-terminus of the second polypeptide; 
 C) at the C-terminus of the second polypeptide; or 
 D) at the C-terminus of the first polypeptide and at the N-terminus of the second polypeptide, 
   wherein at least one of the one or more immunomodulatory domains is a variant IL2 polypeptide of any one of  claims 1 - 6 , and   wherein the multimeric polypeptide exhibits reduced binding affinity to an IL-2 receptor (IL2R) comprising alpha, beta, and gamma polypeptides having amino acid sequences depicted in  FIG. 3A-3C , compared to the binding affinity of a control multimeric polypeptide comprising the IL2 amino acid sequence set forth in SEQ ID NO:1 for the IL2R polypeptide.   
     
     
         9 . The multimeric polypeptide of  claim 8 , wherein:
 a) the first polypeptide comprises, in order from N-terminus to C-terminus:
 i) the epitope; 
 ii) the first MHC polypeptide; and 
 iii) the variant IL2 polypeptide; and 
   b) the second polypeptide comprises, in order from N-terminus to C-terminus:
 i) the second MHC polypeptide; and 
 ii) the Ig Fc polypeptide. 
   
     
     
         10 . The multimeric polypeptide of  claim 8 , wherein:
 a) the first polypeptide comprises, in order from N-terminus to C-terminus:
 i) the epitope; and 
 ii) the first MHC polypeptide; and 
   b) the second polypeptide comprises, in order from N-terminus to C-terminus:
 i) the variant IL2 polypeptide; 
 ii) the second MHC polypeptide; and 
 iii) the Ig Fc polypeptide. 
   
     
     
         11 . The multimeric polypeptide of  claim 8 , wherein:
 a) the first polypeptide comprises, in order from N-terminus to C-terminus:
 i) the epitope; and 
 ii) the first MHC polypeptide; and 
   b) the second polypeptide comprises, in order from N-terminus to C-terminus:
 i) the second MHC polypeptide; and 
 ii) the variant IL2 polypeptide. 
   
     
     
         12 . The multimeric polypeptide of  claim 8 , wherein:
 a) the first polypeptide comprises, in order from N-terminus to C-terminus:
 i) the epitope; and 
 ii) the first MHC polypeptide; and 
   b) second polypeptide comprising, in order from N-terminus to C-terminus:
 i) the variant IL2 polypeptide; and 
 ii) the second MHC polypeptide. 
   
     
     
         13 . The multimeric polypeptide of  claim 8 , wherein:
 a) the first polypeptide comprises, in order from N-terminus to C-terminus:
 i) the epitope; 
 ii) the first MHC polypeptide; and 
 iii) the variant IL2 polypeptide; and 
   b) the second polypeptide comprises the second MHC polypeptide.   
     
     
         14 . The multimeric polypeptide of  claim 7  or  8 , wherein the non-Ig scaffold is an XTEN polypeptide, a transferrin polypeptide, an elastin-like polypeptide, a silk-like polypeptide, or a silk-elastin-like polypeptide. 
     
     
         15 . The multimeric polypeptide of any one of  claims 7 - 14 , wherein the first MHC polypeptide is a β2-microglobulin polypeptide; and wherein the second MHC polypeptide is an MHC class I heavy chain polypeptide. 
     
     
         16 . The multimeric polypeptide of  claim 15 , wherein the β2-microglobulin polypeptide comprises an amino acid sequence having at least 85% amino acid sequence identity to one of the amino acid sequences set forth in  FIG. 6 . 
     
     
         17 . The multimeric polypeptide of  claim 15 , wherein the MHC class I heavy chain polypeptide is an HLA-A, an HLA-B, or an HLA-C heavy chain. 
     
     
         18 . The multimeric polypeptide of  claim 15 , wherein the MHC class I heavy chain polypeptide comprises an amino acid sequence having at least 85% amino acid sequence identity to the amino acid sequence set forth in one of  FIG. 5A-5C . 
     
     
         19 . The multimeric polypeptide of any one of  claims 7 - 14 , wherein the first MHC polypeptide is an MHC Class II alpha chain polypeptide; and wherein the second MHC polypeptide is an MHC class II beta chain polypeptide. 
     
     
         20 . The multimeric polypeptide of any one of  claims 7 - 19 , wherein the epitope is a T-cell epitope. 
     
     
         21 . The multimeric polypeptide of any one of  claims 7 - 13  and  15 - 20 , wherein multimeric polypeptide comprises an Fc polypeptide, and wherein the Ig Fc polypeptide is an IgG1 Fc polypeptide, an IgG2 Fc polypeptide, an IgG3 Fc polypeptide, an IgG4 Fc polypeptide, an IgA Fc polypeptide, or an IgM Fc polypeptide. 
     
     
         22 . The multimeric polypeptide of  claim 21 , wherein the Ig Fc polypeptide comprises an amino acid sequence having at least 85% amino acid sequence identity to an amino acid sequence depicted in  FIG. 4A-4C . 
     
     
         23 . The multimeric polypeptide of any one of  claims 7 - 22 , wherein the first polypeptide and the second polypeptide are non-covalently associated. 
     
     
         24 . The multimeric polypeptide of any one of  claims 7 - 22 , wherein the first polypeptide and the second polypeptide are covalently linked to one another. 
     
     
         25 . The multimeric polypeptide of  claim 24 , wherein the covalent linkage is via a disulfide bond. 
     
     
         26 . The multimeric polypeptide of  claim 25 , wherein the first MHC polypeptide or a linker between the epitope and the first MHC polypeptide comprises an amino acid substitution to provide a first Cys residue, and the second MHC polypeptide comprises an amino acid substitution to provide a second Cys residue, and wherein the disulfide linkage is between the first and the second Cys residues. 
     
     
         27 . The multimeric polypeptide of any one of  claims 7 - 26 , comprising a linker interposed between the epitope and the first MHC polypeptide. 
     
     
         28 . The multimeric polypeptide of any one of  claims 7 - 26 , comprising a linker interposed between the MHC polypeptide and the immunomodulatory polypeptide. 
     
     
         29 . The multimeric polypeptide of any one of  claims 7 - 28 , comprising 2 variant IL2 polypeptides. 
     
     
         30 . The multimeric polypeptide of any one of  claims 7 - 28 , comprising 3 variant IL2 polypeptides. 
     
     
         31 . The multimeric polypeptide of  claim 29  or  claim 30 , wherein the 2 or 3 variant IL2 polypeptides are in tandem, and wherein the multimeric polypeptide comprises a linker between the variant IL2 polypeptides. 
     
     
         32 . The multimeric polypeptide of any one of  claims 8 - 28 , wherein the variant IL2 comprises a substitution of one or more of E15, H16, D20, F42, Y45, and Q126/ 
     
     
         33 . The multimeric polypeptide of any one of  claims 8 - 28 , wherein the variant IL2 comprises a substitution of F42 with Ala, Gly, Val, Ile, or Leu. 
     
     
         34 . The multimeric polypeptide of  claim 33 , wherein the variant IL2 comprises substitutions of F42 and D20, or substitutions of F42 and H16. 
     
     
         35 . The multimeric polypeptide of  claim 33 , wherein the variant IL2 comprises substitutions of F42, D20, and Y45, or substitutions of F42, H16, and Q126. 
     
     
         36 . A nucleic acid comprising a nucleotide sequence encoding a recombinant polypeptide,
 i) wherein the recombinant polypeptide comprises, in order from N-terminus to C-terminus:
 a) an epitope; 
 b) a first major histocompatibility complex (MHC) polypeptide; 
 c) an immunomodulatory polypeptide; 
 d) a proteolytically cleavable linker or a ribosome skipping signal; 
 e) a second MHC polypeptide; and 
 f) an immunoglobulin (Ig) Fc polypeptide; 
 wherein the immunomodulatory polypeptide is a variant of a naturally occurring costimulatory protein, and wherein the variant exhibits a reduced affinity for its counterpart costimulatory protein as compared to the affinity of the naturally occurring costimulatory protein for the counterpart costimulatory protein; or 
   ii) wherein the recombinant polypeptide comprises, in order from N-terminus to C-terminus:
 a) an epitope; 
 b) a first MHC polypeptide; 
 c) a proteolytically cleavable linker or a ribosome skipping signal; 
 d) an immunomodulatory polypeptide 
 e) a second MHC polypeptide; and 
 f) an Ig Fc polypeptide, 
   wherein the immunomodulatory polypeptide is a variant of a naturally occurring costimulatory protein, and wherein the variant exhibits a reduced affinity for its counterpart costimulatory protein as compared to the affinity of the naturally occurring costimulatory protein for the counterpart costimulatory protein.   
     
     
         37 . A nucleic acid comprising a nucleotide sequence encoding a recombinant polypeptide,
 i) wherein the recombinant polypeptide comprises, in order from N-terminus to C-terminus:
 a) an epitope; 
 b) a first major histocompatibility complex (MHC) polypeptide; 
 c) an immunomodulatory polypeptide; 
 d) a proteolytically cleavable linker or a ribosome skipping signal; 
 e) a second MHC polypeptide; and 
 f) an immunoglobulin (Ig) Fc polypeptide; 
 wherein the immunomodulatory polypeptide is a variant immunomodulatory polypeptide of any one of  claims 1 - 6 ; or 
   ii) wherein the recombinant polypeptide comprises, in order from N-terminus to C-terminus:
 a) an epitope; 
 b) a first MHC polypeptide; 
 c) a proteolytically cleavable linker or a ribosome skipping signal; 
 d) an immunomodulatory polypeptide 
 e) a second MHC polypeptide; and 
 f) an Ig Fc polypeptide, 
 wherein the immunomodulatory polypeptide is a variant immunomodulatory polypeptide of any one of  claims 1 - 6 . 
   
     
     
         38 . The nucleic acid of  claim 36  or  37 , wherein the first MHC polypeptide is a β2-microglobulin polypeptide; and wherein the second MHC polypeptide is an MHC class I heavy chain polypeptide. 
     
     
         39 . The nucleic acid of  claim 38 , wherein the β2-microglobulin polypeptide comprises an amino acid sequence having at least 85% amino acid sequence identity to one of the amino acid sequences set forth in  FIG. 6 . 
     
     
         40 . The nucleic acid of  claim 38 , wherein the MHC class I heavy chain polypeptide is an HLA-A, HLA-B, or HLA-C heavy chain. 
     
     
         41 . The nucleic acid of  claim 40 , wherein the MHC class I heavy chain polypeptide comprises an amino acid sequence having at least 85% amino acid sequence identity to the amino acid sequence set forth in any one of  FIG. 5A-5C . 
     
     
         42 . The nucleic acid of  claim 36  or  37 , wherein the first MHC polypeptide is an MHC Class II alpha chain polypeptide; and wherein the second MHC polypeptide is an MHC class II beta chain polypeptide. 
     
     
         43 . The nucleic acid of any one of  claims 36 - 42 , wherein the epitope is a T-cell epitope. 
     
     
         44 . The nucleic acid of any one of  claims 36 - 43 , wherein the Ig Fc polypeptide is an IgG1 Fc polypeptide, an IgG2 Fc polypeptide, an IgG3 Fc polypeptide, an IgG4 Fc polypeptide, an IgA Fc polypeptide, or an IgM Fc polypeptide. 
     
     
         45 . The nucleic acid of  claim 44 , wherein the Ig Fc polypeptide comprises an amino acid sequence having at least 85% amino acid sequence identity to an amino acid sequence depicted in  FIGS. 4A-4C . 
     
     
         46 . The nucleic acid of any one of  claims 37 - 45 , wherein the variant IL2 immunomodulatory polypeptide comprises a substitution of one or more of E15, H16, D20, F42, Y45, and Q126. 
     
     
         47 . The nucleic acid of any one of  claims 36 - 46 , wherein the multimeric polypeptide comprises a second immunomodulatory polypeptide selected from a CD7, CD30L, CD40, CD70, CD83, HLA-G, MICA, MICB, HVEM, lymphotoxin beta receptor, 3/TR6, ILT3, ILT4, and HVEM. 
     
     
         48 . The nucleic acid of any one of  claims 36 - 47 , wherein the proteolytically cleavable linker or ribosome skipping signal comprises an amino acid sequence selected from:
 a) LEVLFQGP (SEQ ID NO:29);   b) ENLYTQS (SEQ ID NO:30);   c) a furin cleavage site;   d) LVPR (SEQ ID NO:32);   e) GSGATNFSLLKQAGDVEENPGP (SEQ ID NO:33);   f) GSGEGRGSLLTCGDVEENPGP (SEQ ID NO:34);   g) GSGQCTNYALLKLAGDVESNPGP (SEQ ID NO:35); and   h) GSGVKQTLNFDLLKLAGDVESNPGP (SEQ ID NO:36).   
     
     
         49 . The nucleic acid of any one of  claim 36 - 48 , wherein the recombinant polypeptide comprises, in order from N-terminus to C-terminus:
 a) a first leader peptide;   b) the epitope;   c) the first MHC polypeptide;   d) the immunomodulatory polypeptide;   e) the proteolytically cleavable linker or ribosome skipping signal;   f) a second leader peptide;   g) the second MHC polypeptide; and   h) the immunoglobulin (Ig) Fc polypeptide.   
     
     
         50 . The nucleic acid of  claim 49 , wherein the first leader peptide and the second leader peptide is a β2-M leader peptide. 
     
     
         51 . The nucleic acid of any one of  claims 36 - 50 , wherein the nucleotide sequence is operably linked to a transcriptional control element. 
     
     
         52 . The nucleic acid of  claim 51 , wherein the transcriptional control element is a promoter that is functional in a eukaryotic cell. 
     
     
         53 . The nucleic acid of any one of  claims 36 - 52 , wherein the first MHC polypeptide or a linker between the epitope and the first MHC polypeptide comprises an amino acid substitution to provide a first Cys residue, and the second MHC polypeptide comprises an amino acid substitution to provide a second Cys residue, and wherein the first and the second Cys residues provide for a disulfide linkage between the first MHC polypeptide and the second MHC polypeptide. 
     
     
         54 . A recombinant expression vector comprising the nucleic acid of any one of  claims 36 - 52 , wherein the vector is optionally a viral vector. 
     
     
         55 . A host cell genetically modified with the recombinant expression vector of  claim 54 . 
     
     
         56 . The host cell of  claim 55 , wherein the host cell is in vitro and wherein the host cell is optionally genetically modified such that the cell does not produce an endogenous MHC β2-microglobulin polypeptide. 
     
     
         57 . A composition comprising:
 a) a first nucleic acid comprising a nucleotide sequence encoding a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope; 
 ii) a first MHC polypeptide; and 
 iii) an immunomodulatory domain, 
   wherein the immunomodulatory polypeptide is a variant of a naturally occurring costimulatory protein, and wherein the variant exhibits a reduced affinity for its counterpart costimulatory protein as compared to the affinity of the naturally occurring costimulatory protein for the counterpart costimulatory protein; and   b) a first nucleic acid comprising a nucleotide sequence encoding a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) a second MHC polypeptide; and 
 ii) an Ig Fc polypeptide. 
   
     
     
         58 . A composition comprising:
 a) a first nucleic acid comprising a nucleotide sequence encoding a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope; and 
 ii) a first MHC polypeptide; and 
   b) a first nucleic acid comprising a nucleotide sequence encoding a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) an immunomodulatory domain, wherein the immunomodulatory domain is a variant of a naturally occurring costimulatory protein, and wherein the variant exhibits a reduced affinity for its counterpart costimulatory protein as compared to the affinity of the naturally occurring costimulatory protein for its counterpart costimulatory protein; 
 ii) a second MHC polypeptide; and 
 iii) an Ig Fc polypeptide. 
   
     
     
         59 . A composition comprising:
 a) a first nucleic acid comprising a nucleotide sequence encoding a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope; 
 ii) a first MHC polypeptide; and 
 iii) an immunomodulatory domain, 
   wherein the immunomodulatory domain is a variant IL2 polypeptide of any one of  claims 1 - 6 ; and   b) a first nucleic acid comprising a nucleotide sequence encoding a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) a second MHC polypeptide; and 
 ii) an Ig Fc polypeptide. 
   
     
     
         60 . A composition comprising:
 a) a first nucleic acid comprising a nucleotide sequence encoding a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope; and 
 ii) a first MHC polypeptide; and 
   b) a first nucleic acid comprising a nucleotide sequence encoding a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) an immunomodulatory domain, wherein the immunomodulatory domain is a variant IL2 polypeptide of any one of  claims 1 - 6 ; 
 ii) a second MHC polypeptide; and 
 iii) an Ig Fc polypeptide. 
   
     
     
         61 . The composition of any one of  claims 57 - 60 , wherein the first and/or the second nucleic acid is present in a recombinant expression vector. 
     
     
         62 . A host cell genetically modified with the composition of any one of  claims 57 - 61 . 
     
     
         63 . A method of producing the multimeric polypeptide of any one of  claims 7 - 35 , the method comprising:
 a) culturing the host cell of any one of  claims 55 ,  56 , and  62  in vitro in a culture medium under conditions such that the host cell synthesizes the multimeric polypeptide; and   b) isolating the multimeric polypeptide from the host cell and/or from the culture medium.   
     
     
         64 . The method of  claim 63 , wherein the second polypeptide comprises an affinity tag, and wherein said isolating comprises contacting the multimeric polypeptide produced by the cell with a binding partner for the affinity tag, wherein the binding partner is immobilized, thereby immobilizing the multimeric polypeptide. 
     
     
         65 . The method of  claim 64 , comprising eluting the immobilized multimeric polypeptide. 
     
     
         66 . A method of selectively activating an epitope-specific T cell, the method comprising contacting the T cell with the multimeric polypeptide of any one of  claims 7 - 35 , wherein said contacting selectively activates the epitope-specific T cell. 
     
     
         67 . The method of  claim 66 , wherein said contacting is in vitro. 
     
     
         68 . The method of  claim 66 , wherein said contacting is in vivo. 
     
     
         69 . The method of  claim 66 , wherein the epitope is a cancer-associated epitope, and wherein said administering selectively increases the activity of a T cell specific for the cancer-associate epitope. 
     
     
         70 . A method of treating cancer in an individual, the method comprising administering to the individual an effective amount of:
 a) the multimeric polypeptide of any one of  claims 7 - 35 ; or   b) one or more recombinant expression vectors comprising nucleotide sequences encoding the multimeric polypeptide of any one of  claims 7 - 35 ; or   c) one or more mRNAs comprising nucleotide sequences encoding the multimeric polypeptide of any one of  claims 7 - 35 ,   wherein the epitope is a cancer-associated epitope, and wherein said administering effective to selectively activate a cancer epitope-specific T cell in an individual.   
     
     
         71 . The method of  claim 70 , wherein said administering is subcutaneous. 
     
     
         72 . The method of  claim 70 , wherein said administering is intravenous. 
     
     
         73 . The method of  claim 70 , wherein said administering is peritumoral. 
     
     
         74 . The method of  claim 70 , wherein said administering is systemic. 
     
     
         75 . The method of  claim 70 , wherein said administering is distal to a treatment site. 
     
     
         76 . The method of  claim 70 , wherein said administering is local. 
     
     
         77 . The method of  claim 70 , wherein said administering is at or near a treatment site. 
     
     
         78 . A composition comprising:
 a) the multimeric polypeptide of any one of  claims 7 - 35 ; and   b) a pharmaceutically acceptable excipient.   
     
     
         79 . A composition comprising:
 a) the nucleic acid of any one of  claims 36 - 53  or the recombinant expression vector of  claim 54 ; and   b) a pharmaceutically acceptable excipient.   
     
     
         80 . A multimeric polypeptide comprising:
 a) a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope; 
 ii) a β2-microglobulin (β2M) polypeptide comprising the amino acid sequence depicted in  FIG. 34A ; and 
   b) a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) a variant of a naturally occurring costimulatory protein, and wherein the variant exhibits a reduced affinity for its counterpart costimulatory protein on a T cell as compared to the affinity of the naturally occurring costimulatory protein for the counterpart costimulatory protein, which variant may optionally be a variant IL-2 polypeptide of any one of  claims 1 - 6 ; 
 ii) a major histocompatibility comples (MHC) heavy chain polypeptide comprising the amino acid sequence depicted in  FIG. 34C ; and 
 iii) an IgG1 Fc polypeptide comprising one or more amino acid substitutions selected from N297A, L234A, L235A, L234F, L235E, and P331S. 
   
     
     
         81 . The multimeric polypeptide of  claim 80 , wherein the IgG1 Fc polypeptide comprises an N297A substitution. 
     
     
         82 . The multimeric polypeptide of  claim 80 , wherein the IgG1 Fc polypeptide comprises an L234A substitution and an L235A substitution. 
     
     
         83 . The multimeric polypeptide of  claim 80 , wherein the IgG1 Fc polypeptide comprises an L234F substitution and an L235E substitution. 
     
     
         84 . The multimeric polypeptide of  claim 80 , wherein the IgG1 Fc polypeptide comprises an L234F substitution, an L235E substitution, and a P331S substitution. 
     
     
         85 . The multimeric polypeptide of any one of  claims 80 - 84 , wherein the second polypeptide comprises two copies of the variant IL-2 polypeptide. 
     
     
         86 . The multimeric polypeptide of any one of  claims 80 - 85 , wherein the first polypeptide comprises a peptide linker between the epitope and the β2M polypeptide. 
     
     
         87 . The multimeric polypeptide of any one of  claims 80 - 86 , wherein the second polypeptide comprises a peptide linker between one or more of:
 a) a first copy of the variant IL-2 polypeptide and a second copy of the variant IL-2 polypeptide;   b) the variant IL-2 polypeptide and the MHC heavy chain polypeptide; and   c) between the MHC heavy chain polypeptide and the IgG1 Fc polypeptide.   
     
     
         88 . The multimeric polypeptide of  claim 86  or  claim 87 , wherein the peptide linker is selected from (GGGGS) 3 , (GGGGS) 4 , and AAAGG. 
     
     
         89 . A multimeric polypeptide comprising:
 a) a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope; 
 ii) a β2-microglobulin polypeptide comprising the amino acid sequence depicted in  FIG. 34A ; and 
   b) a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) a variant IL-2 polypeptide comprising the amino acid sequence depicted in  FIG. 34B ; 
 ii) a major histocompatibility comples (MHC) heavy chain polypeptide comprising the amino acid sequence depicted in  FIG. 34C ; and 
 iii) an IgG1 Fc polypeptide comprising one or more amino acid substitutions selected from N297A, L234A, L235A, L234F, L235E, and P331S. 
   
     
     
         90 . The multimeric polypeptide of  claim 89 , wherein the IgG1 Fc polypeptide comprises an N297A substitution. 
     
     
         91 . The multimeric polypeptide of  claim 89 , wherein the IgG1 Fc polypeptide comprises an L234A substitution and an L235A substitution. 
     
     
         92 . The multimeric polypeptide of  claim 89 , wherein the IgG1 Fc polypeptide comprises an L234F substitution and an L235E substitution. 
     
     
         93 . The multimeric polypeptide of  claim 89 , wherein the IgG1 Fc polypeptide comprises an L234F substitution, an L235E substitution, and a P331S substitution. 
     
     
         94 . The multimeric polypeptide of any one of  claims 89 - 93 , wherein the second polypeptide comprises two copies of the variant IL-2 polypeptide. 
     
     
         95 . The multimeric polypeptide of any one of  claims 89 - 94 , wherein the first polypeptide comprises a peptide linker between the epitope and the β2M polypeptide. 
     
     
         96 . The multimeric polypeptide of any one of  claims 89 - 95 , wherein the second polypeptide comprises a peptide linker between one or more of:
 a) a first copy of the variant IL-2 polypeptide and a second copy of the variant IL-2 polypeptide;   b) the variant IL-2 polypeptide and the MHC heavy chain polypeptide; and   c) the MHC heavy chain polypeptide and the IgG1 Fc polypeptide.   
     
     
         97 . The multimeric polypeptide of  claim 95  or  claim 96 , wherein the peptide linker is selected from (GGGGS) 3 , (GGGGS) 4 , and AAAGG. 
     
     
         98 . A multimeric polypeptide comprising:
 a) a first polypeptide comprising, in order from N-terminus to C-terminus:
 i) an epitope comprising the amino acid sequence YMLDLQPETT (SEQ ID NO:13); 
 ii) a β2-microglobulin polypeptide comprising the amino acid sequence depicted in  FIG. 34A ; and 
   b) a second polypeptide comprising, in order from N-terminus to C-terminus:
 i) a variant IL-2 polypeptide comprising the amino acid sequence depicted in  FIG. 34B ; 
 ii) a major histocompatibility comples (MHC) heavy chain polypeptide comprising the amino acid sequence depicted in  FIG. 34C ; and 
 iii) an IgG1 Fc polypeptide comprising the amino acid sequence depicted in  FIG. 33A, 33B, 33C , or  33 D. 
   
     
     
         99 . The multimeric polypeptide of  claim 98 , wherein the IgG1 Fc polypeptide comprises the amino acid sequence depicted in  FIG. 33B . 
     
     
         100 . The multimeric polypeptide of  claim 98 , wherein the IgG1 Fc polypeptide comprises the amino acid sequence depicted in  FIG. 33C . 
     
     
         101 . The multimeric polypeptide of  claim 98 , wherein the IgG1 Fc polypeptide comprises the amino acid sequence depicted in  FIG. 33D . 
     
     
         102 . The multimeric polypeptide of any one of  claims 98 - 101 , wherein the second polypeptide comprises two copies of the variant IL-2 polypeptide. 
     
     
         103 . The multimeric polypeptide of any one of  claims 98 - 102 , wherein the first polypeptide comprises a peptide linker between the epitope and the β2M polypeptide. 
     
     
         104 . The multimeric polypeptide of any one of  claims 98 - 103 , wherein the second polypeptide comprises a peptide linker between one or more of:
 a) a first copy of the variant IL-2 polypeptide and a second copy of the variant IL-2 polypeptide;   b) the variant IL-2 polypeptide and the MHC heavy chain polypeptide; and   c) the MHC heavy chain polypeptide and the IgG1 Fc polypeptide.   
     
     
         105 . The multimeric polypeptide of  claim 103  or  claim 104 , wherein the peptide linker is selected from (GGGGS) 3 , (GGGGS) 4 , and AAAGG. 
     
     
         106 . A multimeric polypeptide comprising:
 a) a first polypeptide comprising the amino acid sequence depicted in  FIG. 31 ;   b) a second polypeptide comprising the amino acid sequence depicted in  FIG. 22 .   
     
     
         107 . A multimeric polypeptide comprising:
 a) a first polypeptide comprising the amino acid sequence depicted in  FIG. 31 ;   b) a second polypeptide comprising the amino acid sequence depicted in  FIG. 25 .   
     
     
         108 . A multimeric polypeptide comprising:
 a) a first polypeptide comprising the amino acid sequence depicted in  FIG. 31 ;   b) a second polypeptide comprising the amino acid sequence depicted in  FIG. 28 .   
     
     
         109 . A pharmaceutical composition comprising:
 a) a multimeric polypeptide according to any one of  claims 80 - 108 ; and   b) a pharmaceutically acceptable excipient.   
     
     
         110 . One or more nucleic acids comprising nucleotide sequences encoding the first and/or the second polypeptide of the multimeric polypeptide according to any one of  claims 80 - 108 . 
     
     
         111 . The one or more nucleic acids of  claim 110 , wherein the nucleic acids are present in recombinant expression vectors. 
     
     
         112 . A method of selectively activating an epitope-specific T cell, the method comprising contacting the T cell with the multimeric polypeptide of any one of  claims 80 - 108 , wherein said contacting selectively activates the epitope-specific T cell. 
     
     
         113 . The method of  claim 112 , wherein said contacting is in vitro. 
     
     
         114 . The method of  claim 112 , wherein said contacting is in vivo. 
     
     
         115 . A method comprising administering to an individual an effective amount of:
 a) the multimeric polypeptide of any one of  claims 80 - 108 ; or   b) one or more recombinant expression vectors comprising nucleotide sequences encoding the multimeric polypeptide of any one of  claims 80 - 108 ; or   c) one or more mRNAs comprising nucleotide sequences encoding the multimeric polypeptide of any one of  claims 80 - 108 ,   wherein said administering induces a T cell response to epitope in the individual.   
     
     
         116 . The method of  claim 115 , wherein said administering is subcutaneous. 
     
     
         117 . The method of  claim 115 , wherein said administering is intravenous. 
     
     
         118 . The method of  claim 115 , wherein said administering is systemic. 
     
     
         119 . The method of  claim 115 , wherein said administering is intramuscular. 
     
     
         120 . The method of  claim 115 , wherein said administering is distal to a treatment site. 
     
     
         121 . The method of  claim 115 , wherein said administering is local. 
     
     
         122 . The method of  claim 115 , wherein said administering is at or near a treatment site. 
     
     
         123 . A method of delivering a costimulatory polypeptide selectively to target T cell, the method comprising contacting a mixed population of T cells with a multimeric polypeptide of any one of  claims 7 - 35  and  80 - 108 , wherein the mixed population of T cells comprises the target T cell and non-target T cells,
 wherein the target T cell is specific for the epitope present within the multimeric polypeptide, and 
 wherein said contacting delivers the costimulatory polypeptide present within the multimeric polypeptide to the target T cell. 
 
     
     
         124 . A method of delivering IL-2 or a IL-2 variant selectively to a target T cell, the method comprising contacting a mixed population of T cells with the multimeric polypeptide of any one of  claims 8 - 35  and  80 - 108 , wherein the mixed population of T cells comprises the target T cell and non-target T cells,
 wherein the target T cell is specific for the epitope present within the multimeric polypeptide, and 
 wherein said contacting delivers the IL-2 or IL-2 variant present within the multimeric polypeptide to the target T cell. 
 
     
     
         125 . The method of  claim 123  or  124 , wherein the population of T cells is in vitro. 
     
     
         126 . The method of  claim 123  or  124 , wherein the population of T cells is in vivo in an individual. 
     
     
         127 . The method of  claim 126 , comprising administering the multimeric polypeptide to the individual. 
     
     
         128 . The method of any one of  claims 123 - 127 , wherein the target T cell is a regulatory T cell. 
     
     
         129 . The method of any one of  claims 123 - 127 , wherein the target T cell is a cytotoxic T cell. 
     
     
         130 . The method of  claim 123  or  124 , wherein the mixed population of T cells is an in vitro population of mixed T cells obtained from an individual, and wherein said contacting results in activation and/or proliferation of the target T cell, generating a population of activated and/or proliferated target T cells. 
     
     
         131 . The method of  claim 130 , further comprising administering the population of activated and/or proliferated target T cells to the individual. 
     
     
         132 . A method of detecting, in a mixed population of T cells obtained from an individual, the presence of a target T cell that binds an epitope of interest, the method comprising:
 a) contacting in vitro the mixed population of T cells with the multimeric polypeptide of any one of  claims 7 - 35  and  80 - 108 , wherein the multimeric polypeptide comprises the epitope of interest; and   b) detecting activation and/or proliferation of T cells in response to said contacting, wherein activated and/or proliferated T cells indicates the presence of the target T cell.