TNF and infection: IL-1α, IL-1β, MIP-1α, and tumor necrosis factor alpha (TNF-α) were reduced in both IAV- and mock-infected animals at 24 h pbi during infection with each SGD mutant compared to their levels during infection with WT D39 (P < 0.05), except for D39ΔpurD in mock-infected animals (P > 0.05) (Fig. 5 and Fig. S2 to S4).