Pattern recognition receptor-initiated innate antiviral responses in mouse epididymal epithelial cells

Viral infections of the epididymis may impair male fertility and spread sexually transmitted pathogens. The innate antiviral immune responses in the epididymis have yet to be intensively investigated. This study found that mouse epididymal epithelial cells (EECs) constitutively express several viral sensors, including TLR3, retinoic acid-inducible gene I, and DNA-dependent activator of IFN regulatory factors. Other DNA sensors, including p204 and cGMP-AMP synthase, can be induced by transfection of synthetic HSV genomic DNA (HSV60). TLR3 and retinoic acid-inducible gene I in EECs can be activated by their common agonist, polyinosinic-polycytidylic acid [poly(I:C)]. The signaling pathway of DNA sensors can be initiated by HSV60. Both poly(I:C) and HSV60 induced the expression of type 1 IFNs and various antiviral proteins, including IFN-stimulated gene 15, 2',5'-oligoadenylate synthetase, and myxovirus resistance 1. Poly(I:C), but not HSV60, also dramatically induced the expression of major proinflammatory cytokines, including TNF-α and MCP-1, in EECs. In vivo assay confirmed that the local injection of poly(I:C) or HSV60 induced the innate antiviral responses in EECs. This study provided novel insights into the mechanisms underlying the innate antiviral responses in the mouse epididymis.