IL17A and viral infectious disease: During HIV-1 infection, the number and function of IL-17-producing Th17 cells and Tc17 cells are impaired in the peripheral and intestinal mucosa due to direct viral infection and impaired IL-23 signaling pathways that maintain Th17 cell production and stability, and IL-17 levels are reduced, exacerbating impaired intestinal barrier integrity and thus causing microbial translocation and immune activation (Fernandes et al., 2017; Perdomo-Celis et al., 2018).