Rapid screening for Mamu-A1-positive rhesus macaques using a SIVmac Gag peptide-specific cytotoxic T-lymphocyte assay

As part of an ongoing vaccine study using peptide immunogens designed to stimulate simian immunodeficiency virus (SIV)mac-specific cytotoxic T lymphocytes (CTL) it was necessary to identify rhesus macaques within our colony bearing the Mamu-A1 major histocompatibility complex (MHC) class I haplotype. Peripheral blood mononuclear cells (PBMC) from individual monkeys were analysed by immunoelectrofocusing for the presence of a band corresponding to the Mamu-A1 molecule. In addition, PBMC were pulsed with the SIVmac Gag peptide 11 (against which CTL are Mamu-A1 restricted) and analysed for susceptibility to lysis by peptide 11-specific CTL. PBMC from all of the rhesus macaques shown to be Mamu-A1 positive by immunoelectrofocusing were highly sensitive to lysis by the peptide 11-specific CTL. A total of 46% (16 from 35) of the rhesus macaques originating from India were found to be Mamu-A1 positive, whereas none of the Chinese rhesus (0 from 37) macaques possessed this haplotype. Once a peptide-specific CTL is established, screening by CTL assay offers a faster, reliable and more relevant alternative to immunoelectrofocusing for selecting monkeys for use in vaccination trials.