CXCL9 and herpes simplex virus keratitis: Studies in TLR9-knockout (KO) or IFN-α R-KO mice have demonstrated the critical role of these molecules for the induction of CXCL9 and CXCL10, the downstream recruitment of T cells and neutrophils in the cornea, and the control of viral shedding, highlighting the importance of IFN production in HSV keratitis (Conrady et al., 2011).