T-cell modulatory multimeric polypeptides and methods of use thereof

A heterodimer comprising:

• a) a first polypeptide comprising:
• i) a peptide epitope;
• ii) a first major histocompatibility complex (MHC) polypeptide, wherein the first MHC polypeptide is a beta-2 microglobulin (β2M) polypeptide;
• and
• b) a second polypeptide comprising:
• i) a second MHC polypeptide, wherein the second MHC polypeptide is an MHC class I heavy chain polypeptide;
• and
• wherein the first and/or the second polypeptide comprises one or more immunomodulatory polypeptides,
• optionally, wherein the heterodimer comprises an immunoglobulin (Ig) Fc polypeptide or a non-Ig scaffold,
• wherein at least one of the one or more immunomodulatory polypeptides is a variant CD86 polypeptide comprising an amino acid sequence having at least 98% amino acid sequence identity to the amino acid sequence set forth in SEQ ID NO:2
• wherein the variant CD86 polypeptide comprises
• a substitution of H91 with Ala, Arg, Asn, Asp, Cys, Gln, Glu, Gly, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val, based on the numbering of the amino acid sequence set forth in SEQ ID NO:2;
• and
• wherein the variant CD86 polypeptide binds to a CD28 polypeptide having the amino acid sequence depicted in SEQ ID NO:30, and wherein the variant CD86 polypeptide exhibits reduced binding affinity to the CD28 polypeptide, compared to the binding affinity of the CD86 amino acid sequence set forth in SEQ ID NO:2 for the CD28 polypeptide,
• wherein one or more independently selected linkers may be interposed between the components of the first polypeptide and one or more independently selected linkers may be interposed between the components of the second polypeptide, and
• wherein, when the heterodimer comprises two or more immunomodulatory polypeptides, a peptide linker may be interposed between the immunomodulatory polypeptides.