IFNA1 and infection: To determine the role of NS1 and IFN antagonism, virus titers and the level of IFN expression in NSBE and NHBE cells was determined at 0-96 HPI following infection (MOI = 0.01) of undifferentiated NSBE or NHBE cells with wild type (WT) or NS1 deletion mutant (NS1 mut) influenza viruses (Figure 5).