CD4 and infection: In the intestines, the expression of adaptive immune-related genes (C3, TCR α, MHC I, MHC II, CD4, CD8, IgM, IgZ and IgD) was higher in immunized groups after 2 times vaccination, and most of them were also significantly up-regulated in the vaccinated groups post infection, except for CD4 and TCR α (Figure 6A; Supplemental Figure 6A).