Compared to the results for mock infection, the IFN-β–Luc promoter activity was induced by a fold of ∼80 after SeV stimulation for 16 h, but this activity was obviously inhibited in the presence of UL31 (Fig. 1A), similar to the inhibitory effect of the positive control BGLF4 (25). This evidence concerns the gene IFNB1 and infection.