Presence of Distinct Subsets of Cytolytic CD8+T Cells in Chronic HIV Infection

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Abstract
Cytolytic T lymphocytes (CTL) play an important role in the control of HIV infection. The eventual failure to contain HIV-1 infection may arise because of a functional impairment of HIV-specific CTL. We evaluated Gag-specific cytotoxicity in HIV-1-positive Ugandans. Expression of CD107, a marker for cytolytic activity, was present in CD45RAbright and CD45RAdim CD8+ T cell populations in HIV-infected individuals. The frequency of Gag-specific CD107+CD45RAbrightCD28−CCR7− CD8+ T cells decreased with CD4 cell depletion and correlated with the presence of Gag-specific T helper response. In contrast, the frequency of Gag-specific CD107+CD45RAdimCD28−CCR7− CD8+ T cells within the same individuals has no significant association with viral load or CD4 cell count. The ratio of CD45RAbright to CD45RAdim CTL correlates significantly with CD4 cell count. This positive association decreases with antiretroviral treatment (ARV), indicating that suppression of viral replication alters the balance of circulating Gag-specific CD8+ effector T cells. Subsets of cytolytic T cells may have distinct antiviral functions and further characterization of these effector CD8+ T cells may yield important information on T cell regulation and dysfunction in HIV infection.