IRF3 and infection: The overexpression of PBLD or IRF3 effectively impaired BPIV3 replication as indicated by decreased virus titer of tissue culture infectious dose 50 (TCID50), viral HN mRNA, and protein, while knockdown of PBLD had the opposite effect (Fig. 7A, SFig. 5A–H), suggesting that PBLD or IRF3 inhibits BPIV3 infection.