Phenotypic and functional characterization of HIV-1-specific CD4+CD8+ double-positive T cells in early and chronic HIV-1 infection.

OBJECTIVE: CD4+CD8+ double-positive (DP) T cells represent a poorly characterized population of effector T cells found at low frequencies in the peripheral blood. Virus-specific DP T cells have been identified in HIV-1-infected patients but their origin, relationship to conventional CD4+ and CD8+ single-positive (SP) T cells, and role in disease pathogenesis are unclear.
METHODS: In this study, peripheral blood T cells were analyzed for cytokine production, maturation, and cytolytic marker expression by polychromatic flow cytometry in subjects with both early (n = 27) and chronic (n = 21) HIV-1 infection. RESULTS AND
CONCLUSIONS: HIV-1-specific interferon gamma (IFN-g)-producing DP T cells were identified at a median frequency of 0.48% compared with 1.08% and 0.02% for CD8 and CD4 SP cells, respectively, in response to pooled HIV-1 peptides. HIV-1- specific DP T cells exhibited polyfunctionality with characteristics of both CD4 and CD8 SP T cells, including coproduction of IFN-gamma and IL-2 and expression of cytolytic-associated lysosomal-associated membrane protein. No differences in frequencies of unstimulated DP T cells were observed in early compared with chronic infection. However, chronic infection was associated with higher frequencies of HIV-specific, IFN-gamma-producing DP T cells and higher fractions of effector memory and lysosomal-associated membrane protein expression among these cells, suggesting an effect of cumulative viral antigen burden on DP T-cell function.