Abstract: Objective To study the effect of spvB/spvC gene on Salmonella virulence and the Host immune. Methods STM.211,
STM.211-ΔspvB, STM.211-ΔspvC, STM.211-ΔspvB.spvC and PBS were infected with 0.2 mL 105 CFU corresponding strain
respectively by intraperitoneal. We observed the mental status, movement, diarrhea, weight, pelage changed hair of the
infected mouse. Then the level of IL-10, IL-12, IFN-γ were detected by ELISA. Finally, we observe the pathological changes of
liver and spleen with the general view and the microscope. Results Infection symptoms of STM.211, STM.211-ΔspvB and
STM.211-ΔspvC were significantly worse than PBS group, but there was no significant difference between STM.211-spvB.spvC
group and PBS group. The secretion of IFN-γ and IL-12 of STM.211, STM.211-ΔspvB, STM.211-ΔspvC group were significantly
lower than those in the STM.211-ΔspvB.spvC group (P<0.05), but IL-10 secretion was significantly higher than STM.211-ΔspvB.
spvC group (P<0.05). There were no statistical significance among the STM.211, STM.211-ΔSpvB, STM.211-ΔspvC groups (P>
0.05). Conclusion Salmonella virulence can be affected obviously by spvB combined with spvC gene, but not by spvB or spvC.
spvB/spvC gene can inhibit the TH1 cytokines (IFN-γ and IL-12) secretion but promote the TH2 cytokines (IL-10) expression,
leading immune response trend to TH2 shift. It shows that spvB/spvC gene can help the bacteria evade the host immune
defenses, leading to aggravation of infection.