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

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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-2b-restricted CD8+ T cell determinants within SV40 large tumor Ag (TAg), the site V determinant ( 489QGINNLDNL497) 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. © 2012 The American Association of Immunologists, Inc.


Watson, A. M., Mylin, L. M., Thompson, M. M., & Schell, T. D. (2012). 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. The Journal of Immunology, 189(12), 5549–5560. https://doi.org/10.4049/jimmunol.1102221

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