Effects of SIVmac infection on peripheral blood CD4(+)CD8(+) T lymphocytesin cynomolgus macaques

We have previously reported that CD4(+)CD8(+) double-positive (DP) T cells with a resting memory phenotype exist in a substantial proportion of periph eral blood lymphocytes of adult cynomolgus macaques. In this study, we exam ined the effects of simian immunodeficiency virus of macaque (SIVmac) infec tion on DP T cells. In vitro, SIVmac239 nef-open (239) and its nef-deletion mutant replicated well in both CD4(+)CD8(-) and DP T cells. However, when the macaques were infected with 239, DP, but not CD4(+)CD8(-), T cells were transiently increased in parallel with cell activation and viral replicati on, followed by depletion within 1 month postinfection. Interestingly, the nef gene was required for depletion but not for the increase and activation of DP T cells. These data suggest that the pathogenic SN infection may dow nmodulate production and/or blood circulation of DP T cells by a Nef functi on-related mechanism(s) different from that for the depletion of CD4(+)CD8( -) T cells, (C) 1999 Academic Press.