Induction of MHC-IIDR expression on circulating CD8+ lymphocytes in macaques infected with SIVmac239 nef-open but not with its nef-deletion mutant.

We examined the expression kinetics of activation antigens CD38 and MHC-IIDR (DR) on circulating CD8+ lymphocytes in rhesus macaques infected with pathogenic simian immunodeficiency virus strain SIVmac239 nef-open (239) or its nonpathogenic nef-deletion mutant (delta nef). In the longitudinal study, we found for the first time the induction of DR expression on CD8+ lymphocytes in 239-infected macaques. The induction of DR was in parallel with an increasing viral load and a decreasing CD4+ lymphocyte level. In the macaques with the high viral load and low CD4 level, a considerable proportion of the DR+CD8+ subpopulation was CD69+, indicating an activated state. On the other hand, no significant increase in the DR+CD8+ subpopulation level was observed in delta nef-infected macaques. These data indicate that the evaluation of activation markers such as DR and/or CD69 on circulating CD8+ cells may be valuable as a surrogate marker in the SIV-macaque model.