ERN1 and infection: In contrast, inhibition of IRE1 endonuclease activity in A549 cells, using the 3,5-dibromosalicylaldehide (DBSA) inhibitor, or infection of IRE1 knockout (KO) mouse embryonic fibroblasts (MEFs) results in increased RSV mRNA and protein levels and de novo production of infectious virions compared to control cells [25].