IFNA1 and infection: To further analyze if the ability to block host gene expression correlated with the ability of PA-X proteins to inhibit IFN responses during infection, HEK293T cells were co-transfected with pCAGGS plasmids expressing the different H5N1 PA-X variants together with the ISRE Fluc plasmid, and pCAGGS-Rluc (Figure 4).