Th17 cell master transcription factor RORC2 regulates HIV-1 gene expression and viral outgrowth

Among CD4+ T-cells, T helper 17 (Th17) cells are particularly susceptible to HIV-1 infection and are depleted from mucosal sites, which causes damage to the gut barrier resulting in microbial translocation-induced systemic inflammation, a hallmark of disease progression. Furthermore, a proportion of latently infected Th17 cells persist long-term in the gastro-intestinal lymphatic tract, where low-level HIV-1 transcription is observed. This residual viremia contributes to chronic immune activation. Thus, Th17 cells are key players in HIV pathogenesis and viral persistence, however it is unclear why these cells are highly susceptible to HIV-1 infection. Th17 cell differentiation depends on expression of the master transcriptional regulator RORC2, a retinoic acid-related nuclear hormone receptor that regulates specific transcriptional programs by binding to promoter/enhancer DNA. Here, we report that RORC2 is a key host-cofactor for HIV replication in Th17 cells. We found that specific inhibitors that bind to the RORC2 ligand-binding domain reduced HIV replication in CD4+ T-cells. Depletion of RORC2 inhibited HIV-1 infection, whereas RORC2 overexpression enhanced it. RORC2 was found to promote HIV-1 gene expression. Chromatin immune precipitation revealed that RORC2 binds to the nuclear receptor responsive element (NRRE) in the HIV-1 LTR. In treated HIV-1 patients, RORC2+ CD4 T cells contained more proviral DNA than RORC2- cells. Pharmacological inhibition of RORC2 potently reduced HIV-1 outgrowth in CD4+ T-cells from antiretroviral-treated patients. Altogether, these results provide a new explanation as to why Th17 cells are highly susceptible to HIV-1 infection and point to RORC2 as a cell-specific target for HIV-1 therapy. Significance statementHIV-1 infects CD4 T cells and among these, Th17 cells are known to be particularly permissive for virus replication. Infection of Th17 cells is critical for AIDS pathogenesis and viral persistence, however it is not clear why these cells are highly permissive to HIV-1. We found that Th17 cell permissiveness depends on expression of the hormone receptor RORC2, which is the master transcriptional regulator of Th17 cell differentiation. We identify RORC2 as a new, cell-specific host-dependency factor that can be targeted by small molecules. Our results point to RORC2 as a cell-specific target for HIV-1 therapy, an entirely new concept in the field, and suggest HIV-1 might have evolved to exploit RORC2 to promote its own persistence.