Frontline: Polyfunctional T cell responses are a hallmark of HIV-2 infection

disease progression and maintenance of HIV-specific CD4+ T cell help in most infected subjects. Thus, HIV-2 provides a unique natural human model in which to investigate correlates of immune protection against HIV disease progression. Here, we report a detailed assessment of the HIV-2-specific CD4+ and CD8+ T cell response compared to HIV-1, using polychromatic flow cytometry to assess the quality of the HIV-specific Tcell response by measuring IFN-c, IL-2, TNF-a, MIP-1b, and CD107a mobilization (degranulation) simultaneously following Gag peptide stimulation. We find that HIV-2-specific CD4+ and CD8+ T cells are more polyfunctional that those specific for HIV-1 and that polyfunctional HIV-2-specific Tcells produce more IFN-c and TNF-a on a per-cell basis than monofunctional T cells. Polyfunctional HIV-2-specific CD4+ T cells were generally more differentiated and expressed CD57, while there was no association between function and phenotype in the CD8+ Tcell fraction. Polyfunctional HIV-specific Tcell responses are a hallmark of non-progressive HIV-2 infection and may be related to good clinical outcome in this setting