Immunoprotection And Immunomechanism Of Sheep Immuned With E.granulosus Recombinant Protein P29

Objective:To investigate the protective immunity against Echinococcus granulosus in sheep immunized with r Eg.P29.Method:For investigating whether the immune protective efficiency of the animal can be induced by the recombinant protein(To make the test and statistic of the liver cyst charge number of animals; the immune protective efficiency which is induced by recombinant protein can be calculated by the reduction capsule rate formula), we use recombinant protein of Echinococcus granulosus which is prepared by Gene recombination technique to immune sheep(immune two times), and use the prepared eggs of Echinococcus granulosus to infect animals after the second immunization; meanwhile, in order to survey the change of humoral and cellular immunity of the animal which is induced by pre and post the recombinant protein immunity and the eggs infection, we collected animal blood and serum separately at each time period before and after the recombinant protein immunity and the eggs infection,and also use the ELISA method to test the expression level of the antibodies(Ig G, Ig A, Ig M, Ig G1, Ig G2)and the cytokines(IL-2, IL-4, IL-10, IFN-γ)of the serum.Results:1. 94.8% protection can be induced by r Eg.P29 against the a challenge oral infection of E. granulosus eggs in sheep2. Protective immunity is due to antibody immune response. Two weeks after immunization, ELISA assay indicated that the immunized sheep generated specific high levels of Ig G and of which isotypes Ig G1, Ig G2, compared with the antibody levels in the control group(P<0.01). After challenge with Eg. eggs, the levels of Ig G, Ig G1, and Ig G2 maintain significant higher than negative control(P<0.01). Ig M concentration reached a peak in the early stage of vaccination or infection. Ig A level is mild up-regulation after vaccination and reached a peak in the chronic infection(at 28w)(P<0.01), suggesting the generation of Ig A persist in a long time during the chronic infection. Taken together, our vaccine r Eg.P29 induced a sufficient protective humoral immunity against cystic echinococcosis in sheep.3. Simultaneously, protective immunity is due to cellular immune response. In vaccination group, the secretion of IFN-γ increased significantly in the vaccinated sheep(P<0.01), whereas there was no significant difference in IL-2、IL-4、IL-10 between before and after infection. The IL-2 and IFN-γ levels of vaccinated sheep were increased significantly than control(P<0.01), suggesting that our vaccine candidate induced Th1 cellular immune response. In contrast, in control group, the IL-4 levels after infection have increased significantly(P<0.01), indicating that the natural infection induced Th2 immune response which benefits for parasite escape from immune defense.Conclusion:1. The results indicate that the r Eg.P29 vaccine could induce potent protective immunity as a promising vaccine candidate to prevent cystic echinococcosis.2. Sheep immunized with r Eg.P29 induced the humoral immune response as generation of a series of antibodies such as Ig G, Ig G1, Ig G2, Ig A, Ig M.3. Sheep immunized with r Eg.P29 induced Th1 cellular immune response with release of cytokine IL-2 and IFN-γ.