Detection of Simian Immunodeficiency Virus Gag-Specific CD8(+) T Lymphocytes in Semen of Chronically Infected Rhesus Monkeys by Cell Staining with a Tetrameric Major Histocompatibility Complex Class I-Peptide Complex

Evaluation of human immunodeficiency virus type 1-specific mucosal cytotoxic T lymphocytes can be hampered by limited cell yields from mucosal sites. We sought to characterize virus-specific CD8(+) T lymphocytes with cytotoxic activity in the male genital tracts of SIVmac-infected rhesus monkeys by using a peptide epitope-specific functional T-cell assay and a tetrameric major histocompatibility complex class I-peptide complex. This tetrameric complex was constructed with the rhesus monkey HLA-A homolog molecule Mamu-A*01 and a dominant-epitope 9-amino-acid fragment of SIVmac Gag (p11C, C-M). The proportion of tetramer-positive CD8(+) T cells in semen of SIVmac-infected monkeys ranged from 5.9 to 22.0%. By the use of a standard (51)Cr release assay, these cells were found to have peptide epitope-specific cytolytic activity after in vitro expansion. Four-color flow-cytometric analysis of these seminal tetramer-positive CD8(+) T cells demonstrated that they express memory-associated (CD62L(−) CD45RA(−)) and activation-associated (CD11a(+) Fas(+) HLA-DR(+)) molecules. The present experiments illustrate the power of tetramer technology for evaluating antigen-specific CD8(+) T lymphocytes in a mucosal tissue compartment.