Mauritian cynomolgus macaques share two exceptionally common MHC class I alleles that restrict SIV-specific CD8+ T cells.

Vaccines that elicit CD8(+) T-cell responses are routinely tested for immunogenicity in nonhuman primates before advancement to clinical trials. Unfortunately, the magnitude and specificity of vaccine-elicited T-cell responses are variable in currently utilized nonhuman primate populations, owing to heterogeneity in major histocompatibility (MHC) class I genetics. We recently showed that Mauritian cynomolgus macaques (MCM) have unusually simple MHC genetics, with three common haplotypes encoding a shared pair of MHC class IA alleles, Mafa-A*25 and Mafa-A*29. Based on haplotype frequency, we hypothesized that CD8(+) T-cell responses restricted by these MHC class I alleles would be detected in nearly all MCM. We examine here the frequency and functionality of these two alleles, showing that 88% of MCM express Mafa-A*25 and Mafa-A*29 and that animals carrying these alleles mount three newly defined simian immunodeficiency virus-specific CD8(+) T-cell responses. The epitopes recognized by each of these responses accumulated substitutions consistent with immunologic escape, suggesting these responses exert antiviral selective pressure. The demonstration that Mafa-A*25 and Mafa-A*29 restrict CD8(+) T-cell responses that are shared among nearly all MCM indicates that these animals are an advantageous nonhuman primate model for comparing the immunogenicity of vaccines that elicit CD8(+) T-cell responses.