HIV infection of primary human T cells is determined by tunable thresholds of T cell activation

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Abstract
HIV infection of primary human T cells requires T cell activation signals. However, how strength, duration, and quality of TCR signals affect susceptibility of resting human T cells to HIV infection remains poorly understood. We found that the same threshold and duration of antigen signals that lead to optimal T cell activation are required for HIV to progress beyond the level of reversetranscription within resting T cells. Remarkably, sustained cytokine signaling from the IL‐2 receptor following TCR triggering was critical in establishing productive infection. While blockade of TCR signaling pathways with inhibitors of the phosphatidylinositol 3‐kinase pathway caused a partial pre‐integration block, another inhibitor, rapamycin, completely suppressed the infection. In contrast, cyclosporin A or FK506, inhibitors of NFAT, failed to block infection if the T cells were pre‐activated. Collectively, these results bring to light significant parallels between successful HIV infection and optimal thresholds of T cell activation. Furthermore, our results underscore the critical role of IL‐2 signaling in establishing productive HIV infection. These findings have important implications for our understanding of the complex interplay of HIV with host factors induced upon T cell activation.