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 SIV mac239 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.