When mice were vaccinated with LAIV WSN-NA followed by infection with a high lethal dosage of H5N1, the mice produced less total protein in the BAL fluid and lower levels of IFN-α, IL-2, IL-4, IL-6, and IL-17D, but higher levels of IFNγ, IL-12, and IL-27 to activate the IAV-specific CD8+ T-cell response, suggesting that the NA activity would affect the course of host immune response to IAV infection (Fig. 5). This evidence concerns the gene IL4 and infection.