Modification of a tumor antigen determinant to improve peptide/MHC stability is associated with increased immunogenicity and cross-priming a larger fraction of CD8+ T cells

J Immunol. 2012 Dec 15;189(12):5549-60. doi: 10.4049/jimmunol.1102221. Epub 2012 Nov 21.

Abstract

Altered peptide ligands (APLs) with enhanced binding to MHC class I can increase the CD8(+) T cell response to native Ags, including tumor Ags. In this study, we investigate the influence of peptide-MHC (pMHC) stability on recruitment of tumor Ag-specific CD8(+) T cells through cross-priming. Among the four known H-2(b)-restricted CD8(+) T cell determinants within SV40 large tumor Ag (TAg), the site V determinant ((489)QGINNLDNL(497)) forms relatively low-stability pMHC and is characteristically immunorecessive. Absence of detectable site V-specific CD8(+) T cells following immunization with wild-type TAg is due in part to inefficient cross-priming. We mutated nonanchor residues within the TAg site V determinant that increased pMHC stability but preserved recognition by both TCR-transgenic and polyclonal endogenous T cells. Using a novel approach to quantify the fraction of naive T cells triggered through cross-priming in vivo, we show that immunization with TAg variants expressing higher-stability determinants increased the fraction of site V-specific T cells cross-primed and effectively overcame the immunorecessive phenotype. In addition, using MHC class I tetramer-based enrichment, we demonstrate for the first time, to our knowledge, that endogenous site V-specific T cells are primed following wild-type TAg immunization despite their low initial frequency, but that the magnitude of T cell accumulation is enhanced following immunization with a site V variant TAg. Our results demonstrate that site V APLs cross-prime a higher fraction of available T cells, providing a potential mechanism for high-stability APLs to enhance immunogenicity and accumulation of T cells specific for the native determinant.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antigens, Neoplasm / genetics*
  • Antigens, Neoplasm / metabolism
  • Antigens, Polyomavirus Transforming / genetics*
  • Antigens, Polyomavirus Transforming / metabolism
  • CD8-Positive T-Lymphocytes / immunology*
  • CD8-Positive T-Lymphocytes / metabolism
  • CD8-Positive T-Lymphocytes / pathology
  • Cross-Priming / genetics
  • Cross-Priming / immunology*
  • Epitopes, T-Lymphocyte / genetics*
  • Epitopes, T-Lymphocyte / metabolism
  • Lymphocyte Activation / genetics
  • Lymphocyte Activation / immunology
  • Lymphocyte Count
  • Major Histocompatibility Complex / genetics*
  • Major Histocompatibility Complex / immunology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Peptides / metabolism*
  • Protein Stability
  • Simian virus 40 / genetics
  • Simian virus 40 / immunology*
  • Tumor Cells, Cultured
  • Up-Regulation / genetics
  • Up-Regulation / immunology

Substances

  • Antigens, Neoplasm
  • Antigens, Polyomavirus Transforming
  • Epitopes, T-Lymphocyte
  • Peptides