IL1B and infection: We detected induction of pro-inflammatory cytokines and chemokines (e.g., IL-1β and MIP-1α; Fig. 6b) in neonatal rats after infection with rCDC-9 P11 and a shift to anti-inflammatory cytokines (e.g., IL-10, Fig. 6a) after infection with attenuated rCDC-9 P45 or VP4 mutants harboring AA331 mutations, either single or in combination (VP4_AA331, VP4_AA331_385_388, and VP4_AA331_364_385_388).