IRF3 and infection: In line with what was reported in human airway epithelial cells37, Western blot analysis revealed increased levels of phosphorylation of both NF-κB and IRF-3 in WI-38 cells 18 h and 24 h after hMPV infection, as assessed by monitoring NF-κB p65 S536 phosphorylation and IRF3 S396 phosphorylation respectively (Fig. 5a,b).