Protective Immunization Against Schistosoma Japonicum By Recombinant Paramyosin In C57bl/6 Mice And Buffalos

A national survey reported in 2006 showed that the schistosomiasis japonica was still a serious threat to public health, though medical progress has been achived in the recent years in China. There are more than 510,000 patients and 60,000,000 people at risk.The useful therapies nowadays for controlling schistosomiasis are based on the population chemotherapy with praziquentel, combined with propaganda of health and killing snails in endemic areas, which have attained great achievements. However, the achievement of control program is being challenged by the high ratio of reinfection after chemotherapy and change of both economics and environments. In 1980s the worldwide scientists reached consensus that, it is a priority to develop an effective anti-schistosomiasis vaccine to prevent reinfection after chemotherapy.Schistosomiasis japonica is a zoonosis, farm cattle play an important role in the transmission as capital reservoir host and infection sources. The development of domestic animal schistosomiasis vaccine not only contributes to the prevalence controlling, but also to the theoretical foundation for the human schistosomiasis vaccine research. The research on the vaccine for schistosomiasis from the dead vaccine, live attenuated vaccine, engineering vaccine, to nucleic acid vaccine in the past seventy years.Paramyosin, one of the anti-schistosomiasis vaccine candidate molecules, had required promising protective effects in the S. mansoni or S. japonicum researches. The protective effects induced by the paramyosin were outstanding compared with other candidates. Native or recombinant paramyosin protein and DNA vaccines could reduce the worm burden over 60% in murine or buffalo models. Protein used in many protection experiments were biochemical purified product from worm, or recombinant expression product from E.coli. However, biochemical purification needs massive worms and recombinant expression always has poor purity. Limited resource blocked the development of paramyosin as a promising vaccine candidate.Adjuvant plays an important role in immunoregulation and boosting vaccine potency. A good adjuvant could enhance immunogenicity of antigen and protective effects, and should not cause side effect such as allergic or autoimmune response. Paramyosin used in this study was expressed and purified from E.coli, which over 95% purity, could be large-scale prepared for research. Both the structure and biological features were consistent with native paramyosin. To exploring the optimum vaccine combination, paramyosin combined with several kinds of adjuvant respectively were used to vaccinate mice. We investigated the protective effects of rSj97-ISA206 combination in buffalos against S.japonicum infection to find the optimum vaccine combination for reservoir hosts such as livestock, farm cattle especially.The main results are as follows:1. The purity of full-length paramyosin large-scale prepared is over 95%, with extreme low LPS (0.07EU/ml), meanwhile both the structure and biological features were same with native paramyosin.2. rSj97-Alhydrogel immunization could induce any protective effects in neither Kunming nor C57BL/6 mice model.3. C57BL/6 mice immunized with rSj97-ISA206 showed a significant reduction in worm burden (45.3%, P<0.01) and liver egg burden (35.4%, P<0.05) comparing with rSj97-FA or rSj97-CpG ODN-IFA, suggesting that rSj97-ISA206 could induce a good protection against schistosoma infection.4. In buffalos, rSj97-ISA206 group showed a reduction in worm burden 28.01% (P=0.443), in stool egg burden 28.03% (P=0.584) compared with ISA206 group; rSj97-ISA206 group showed a reduction in worm burden 16.08% (P=0.742), in liver egg burden 3.64% (P=0.963), in stool egg burden 38.70% (P=0.462).5. rSj97 could induce high levels of specific IgG2a and IgG1 in C57BL/6 mice, suggesting that rSj97 could induce specific Th1- and Th2-characteristic antibody, which might be responsible for the protective effects in C57BL/6 mice.6. rSj97 immunization could induce high levels specific IgG2 and IgG1, as well as a Th1 dominant response. Both the humoral and cellular immune responses may be responsible for the protection in buffalos.The results further enriched the study of protective immunity,especially in buffalos, and provide useful data to the construction of optimum vaccine combination that suiting for buffalos in the future.