IRF9 and viral infectious disease: Then type I IFN stimulates cells to initiates a signaling cascade that leads to phosphorylation and heterodimerization of STAT1 and STAT2, which interact with IRF9 to form ISGF3, regulating the synthesis of many IFN-stimulated genes (ISGs), including IRF1, IFIT1, IFIT3, Mx1, ISG15, and IFI44L, serving as an essential primary barrier for virus infection (Darnell et al., 1994; Kotenko et al., 2003; Stark and Darnell, 2012; Au-Yeung et al., 2013).