Short Communication : 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 (△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 △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.