MUC4 and infection: Meanwhile, gene expression analysis revealed that in the ΔsaaS group, Muc1 (encoding Mucin-1) had higher expression at 6 hpi; Muc2 (encoding Mucin-2) had higher expression throughout infection; while Muc4 (encoding Mucin-4) had higher expression at 72 hpi and 120 hpi (Figure 2b).