Study On The Pathogenic Role Of Pasteurella Multocida OmpH In Mediating Hemorrhagic Septicaemia In Yak

Pasteurella multocida,(P.multocida;Pm)is the aetiological bacteria of hemorrhagic septicaemia in yak of Qinghai-Tibet Plateau,however,its virulence factors and pathogenesis are poorly understood.The outer membrane protein H(OmpH)is the most bundant protein in the outer membrane of Pm and also has been identified as a multifunctional crucial protein involved in pathogenicity and invasiveness.Previously,we showed that the recombinant OmpH protein from the virulent strain P0910 isolated from yak could produce 90% of the protection in mice,which suggested that the OmpH is an important protective antigen in Pm.However,whether the OmpH is involved in the initial adhesion to cell and invasion into host tissues has not been studied yet.So,the serum resistance,anti-phagocytosis and the adhesion ability of the bronchial epithelial cells of yak were studied.It provided an important theoretical basis for the pathogenesis role of Pm OmpH and the development of gene deletion vaccine.In order to study the bactericidal effect of P0910 parent strain on the complement of yak serum,the bacterias were suspended in the fresh or inactivated serum from yak.The results showed that there are differences of the survival rate of bacteria,in each different concentration for P0910 strain treatment with fresh serum or inactivated serum from yak.But with the decreasing concentration of bacteria,bactericidal action of fresh yak serum was better than that of inactivated serum.It may be a pathogenesis of yak Pm that resistance to yak serum.In this study,mouse peritoneal macrophages were isolated so as to study the anti-phagocytic effect of P0910 strain and P0910 strain were treated with antiserum againt OmpH or normal rabbit serum.The results show that the phagocytosis of mouse peritoneal macrophages to yak P0910 strain treatment with rabbit antiserum against OmpH was better than that of normal rabbit serum(phagocytic index: P<0.05,P=0.0178).It shows that antiserum against OmpH can promote phagocytosis of mouse peritoneal macrophages to P0910 strain.The bronchial mucosal epithelial cells from yak were cultured by the use of cold digestionof bronchial ligation and bronchial tissue adherence respectively.The results show that the two methods are all high activity and high purity of cells,which the former is better for increase significantly the number of cells and improve its vitality.It can be used to culture bronchial epithelial cells from yak.The adhesion model of bronchial epithelial cells from yak was established to study the adhesion ability of bacteria on cells.Different concentration bacterium suspension which were in logarithmic phase were used to infect bronchial epithelial cells and fibroblasts from yak.The results showed that P0910 strain could adhere to the bronchial epithelial cells and fibroblasts from yak,When the bacteria content of 1.0 × 10~7 mL and 4h after infection,the adhesion is best.The result showed that adhesion ability of P0910 strain on bronchial mucosa epithelial cells far more than fibroblasts from yak.As a result,it was used to laid a foundation on study biological characteristics of ?ompH and its complemented strain of P0910 strain and the pathogenic role of PmOmpH in Mediating Hemorrhagic Septicaemia in Yak.