IL6 and infection: The results showed that the production of IL-6 and TNF-α in sera was obviously deceased following 2308ΔeryAΔotnK infection compared to 2308 infection, and 2308ΔotnK and 2308ΔeryA infections also resulted in a decrease in IL-6 and TNF-α release relative to 2308 infection, but there was no significant difference (Fig. S6), which was consistent with the results found in infected placenta.