Expression And Immunogenicity Research Of Fusion Protein Of P.multocida OmpH And E.coli OmpA

The Pasteurella multocida is a major pathogen.It initiates a variety of diseases such asHaemorrhagic Septicaemia and Pneumonia which is serious damage to the development of dairyindustry.The traditional ways such as chemical injection and using of antibiotics have made us themisunderstanding,so prevention will become the benchmark of the scientific measure of animalhusbandry development in the future. According to new research,the P.multocida proteinOmpH(Outer membrane protein H) can offer higher immune protection to the animals.The OmpH,as a porin,can give priority to identification of hydrophobic material,which plays an important rolein the immune starting. Escherichia coli OmpA(Outter membrane protein A) is the key protein,associated with bacterial adhesion,can activate the antigen present cells and release the immuneactive factors to stimulate the immune system to produce nonspecific and specific immunitythroughing Toll-like receptor,and then induce lymphocyte proliferation,so the OmpA is a kind ofnatural immune adjuvant.The experiment took use Escherichia coli prokaryotic expression system to expressbiological functions’ recombinant proteins such as OmpH and OmpH-OmpA.Constructed therecminant subunit vaccines which have the ability of immunomodulatory to the animals’body.With that,we can provide a further way for preventing the cattle Hemorrhagic Septicemia with thefusion proteins.Firstly,virulent strain P.multocida CVCC448OmpH gene amplified by PCR, connected tothe pMD18-T vector and subsequently transformed into E.coli DH5α.After sequencing andsequence comparison analysising, cloning OmpH genes and connecting to pET28-a expressionvector, and then tranformed into E.coli BL-21, after inducing of IPTG, identificating theexpression of protein OmpH with Western-blotting; Secondly, OmpA’s amplification fromvirulent strain of E.coli(K88), and then the method of overlap PCR to amplify OmpH-OmpA wasuesd, after a serise of operations, abtaining the purified recombinant fusion protein OmpH-OmpA;Finally, the mices as experimental animals, detected the content of IL-2,IL-4,IFN-γ secretion andlymphocyte proliferation assay of immunized mices by the classification of the experimentalgroups and the control group. The purpose of this experiments is to test the effection ofrecombinant proteins to induce both humoral and cellulor immunity.The research has successfully constructed some certain biological active OmpH andOmpH-OmpA.Animal experiment has shown that the groups of OmpH-OmpA and OmpH+Freund’s adjuvant had significant differences in antibody titer in two weeks after the firstvaccining, the two groups showed significant antibody growth and decline curve. Two weeks afterthe third vaccining,the result of serum cytokine levels and the lymphocyte proliferation had apositive correlation. In animal protection test,the P.multocida inactivated vaccine,among OmpH-OmpA protein, OmpH protein+Freund’s adjuvant, OmpH protein and PBS control group,thechallenge protection rat were100%、80%、80%、20%、0%. In summary, the recombinant proteins of prokaryotic expression can induced and producespecific antibodies for OmpH and OmpH-OmpA to experimental animal, and show goodimmunogenicity. At the same time, the protein of the OmpA, also played a certain adjuvantfunction,which can prevent P.multocida to infect the animals.With this,it will provide a newreference to prevent and control cows hemorrhagic septicemia.