Since the primary role of influenza NS1 protein is to inhibit IFN and host antiviral responses during viral infection (Hale et al., 2008b; Nogales et al., 2018b), we next explored the effect of expressing heterotypic NS1 proteins in the backbone of IAV PR8, on the ability of the virus to inhibit induction of IFN in infected cells using cell- and virus-based IFN bioassays (Figure 4A). The gene discussed is IFNA1; the disease is viral infectious disease.