INDUCTION OF MHC-IIDR EXPRESSION ON CIRCULATING CD8(-OPEN BUT NOT WITH ITS NEF-DELETION MUTANT() LYMPHOCYTES IN MACAQUES INFECTED WITH SIVMAC239 NEF)

We examined the expression kinetics of activation antigens CD38 and MH C-IIDR (DR) on circulating CD8(+) lymphocytes in rhesus macaques infec ted with pathogenic simian immunodeficiency virus strain SIV mac239 ne f-open (239) or its nonpathogenic nef-deletion mutant (Delta nef). In the longitudinal study, we found for the first time the induction of D R expression on CD8(+) lymphocytes in 239-infected macaques, The induc tion of DR was in parallel with an increasing viral load and a decreas ing CD4(+) lymphocyte level, In the macaques with the high viral load and low CD4 level, a considerable proportion of the DR(+)CD8(+) subpop ulation was CD69(+), indicating an activated state, On the other hand, no significant increase in the DR(+)CD8(+) subpopulation level was ob served in Delta nef-infected macaques. These data indicate that the ev aluation of activation markers such as DR and/or CD69 on circulating C D8(+) cells may be valuable as a surrogate marker in the SIV-macaque m odel.