The Immunoprotection of OmpH Gene Deletion Mutation of Pasteurella multocida on Hemorrhagic Sepsis in Qinghai Yak

Abstract

OmpH is among the most important virulence factors of Pasteurella multocida, which mediates septicemia in yaks (Bos grunniens I) after infection with the bacteria. In the present study, yaks were infected with wild-type (WT) (P0910) and OmpH-deficient (ΔOmpH) P. multocida strains. The mutant strain was generated through the reverse genetic operation system of pathogens and proteomics technology. The live-cell bacterial count and clinical manifestations of P. multocida infection in Qinghai yak tissues (thymus, lung, spleen, lymph node, liver, kidney, and heart) were analyzed. The expression of differential proteins in the yak spleen under different treatments was analyzed using the marker-free method. We found that compared with the mutant strain, the titer of wild-type strains was significantly higher in tissues. Additionally, compared with other organs, the bacteria titer was significantly higher in the spleen. Compared with the WT p0910 strain, the mutant strain generated milder pathological changes in the tissues of yak. Proteomics analysis revealed that 57 of the 773 proteins expressed in P. multocida were significantly differentially expressed between the ΔOmpH and P0910 groups. Of the 57, 14 were over-expressed, whereas 43 were under-expressed. The differentially expressed proteins in the ΔompH group regulated the ABC transporter (ATP-powered translocation of many substrates across membranes) system, the two-component system, RNA degradation, RNA transcription, glycolysis/gluconeogenesis, biosynthesis of ubiquinone and other terpenoid-quinones, oxidative phosphorylation (citrate cycle) as well as fructose and mannose metabolism. The relationship among 54 significantly regulated proteins was analyzed using STRING. We found that WT P0910 and ΔOmpH of P. multocida infection activated the expression of ropE, HSPBP1, FERH, ATP10A, ABCA13, RRP7A, IL-10, IFN-γ, IL-17A, EGFR, and dnaJ. Overall, deletion of the OmpH gene weakened the virulence but maintained the immunogenicity of P. multocida in yak. The findings of this study provide a strong foundation for the pathogenesis of P. multocida and the management of related septicemia in yaks.