Induction of IL-17+ T-cells by HIV-Tat protein is mediated via Vascular Endothelial Growth Factor Receptor-2

Anti-retroviral therapy (ART) has transformed human immunodeficiency virus (HIV) infection from a fatal illness to a chronic condition by controlling viral replication and restoring immune function. However, chronic T-cell activation can be observed in 20-35% of individuals on ART, resulting in an immune reconstitution inflammatory syndrome (IRIS) [1-3]. IRIS involving the CNS can result in permanent disability and death [4]. Tat is a viral protein produced in HIV-infected cells and released into the extracellular space [5]. We show that the secreted-Tat protein activated uninfected T-cells in an antigen-independent manner without inducing proliferation. Notably, Tat induced the secretion of IL-17 from T-cells and increased the percentage of T-cells with a Th17 phenotype. T-cell activation was independent of the T-cell receptor but dependent on endocytosis of Tat and activation of vascular endothelial growth factor receptor 2 (VEGFR2). Tat induced global changes in histone acetylation and increased HIV infection in non-replicating T-cells. Furthermore, in an individual with CNS IRIS, Tat expressing infiltrates and secretion of IL-17 was detected in the absence of viral replication in the brain. Thus Tat can induce T-cell activation in a paracrine and autocrine manner resulting in propagation of inflammation and increased virulence. 12 Human samples in 6 pairs: 6 Human T cell HIV tat exposed 0hrs, 6 Human T cell HIV tat exposed 24hrs