The immunopathogenesis of retroviral diseases: no immunophenotypic alterations in T, B, and NK cell subsets in SIVmac239-challenged rhesus macaques protected by SIV delta nef vaccination.

Immunophenotype analysis was used to characterize circulating lymphocyte subset levels in both rhesus monkeys that were chronically infected with SIVmac239 and in those that had resisted SIVmac239 infection as a result of prior vaccination with an attenuated SIV strain. Alterations in T, NK, and B cell subsets were compared with those previously identified in humans chronically infected with HIV [8-11, 14, 22]. The well-known decrease in CD4+ cell levels was observed in the SIVmac239-infected animals. However, these animals had relatively little activation of circulating CD8+ T cells as compared with uninfected monkeys. This contrasts with chronically HIV-infected humans who have substantial activation of circulating CD8+ cells as evidenced by elevated HLA-DR and CD38 antigen expression on CD8+ cells as well as substantially increased percentages and numbers of total CD8+ cells. NK cells of the SIVmac239-infected animals, on the other hand, demonstrated the same changes recently described in HIV-infected humans, i.e., a decrease in circulating percentages and a decreased amount of FcRIII (CD16). B cell percentages were markedly increased in the SIVmac239-infected animals, a finding also noted in some children with HIV infection but not in HIV-infected adults. SIV delta nef-vaccinated/SIVmac239-challenged animals showed none of the immune alterations found in the SIVmac239-infected monkeys, providing further confirmation of lack of SIV disease in these vaccinated animals.