Distinct profile of T cell activation in HIV type 2 compared to HIV type 1 infection: differential mechanism for immunoprotection.

The mechanism for the lower rate of disease progression in HIV-2 infection remains undefined. We evaluated T cell activation in a cohort of HIV-infected commercial sex workers in Dakar, Senegal. CD8+ T cell activation was significantly lower in HIV-2- compared to HIV-1-infected volunteers and both groups displayed higher activation levels compared to seronegative individuals. In contrast, CD4+ T cell activation was similar between the HIV-1 and HIV-2 groups and significantly higher compared to the seronegative group. Interestingly, HIV-2-positive volunteers with evidence of Gag-specific CD8+ T cell responses displayed lower CD4+ T cell activation. Our data suggest that the distinct T cell activation profile in HIV-2-positive individuals may reflect on the presence of effective host immune responses in HIV-2 infection.