Field evaluation of vaccine candidates against schistosomiasis japonica and molecular analysis of vaccine efficacy

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In the year of 2002, we prepared a large amount of recombinant protein of calpain of Schistosoma japonicum, and by the use of the recombinant protein, we produced monoclonal antibodies to S.japonicum calpain and also tested their vaccine effects in pigs. Immunohistochemistry using our mAbs revealed tissue distribution and changes of expression in developmental stages in S.japonicum. We observed strong signal in the excretory grand of cercariae. This seemed to explain a probable explanation of vaccine efficacy of calpain. In our pig trials, we observed significant reduction in egg production, however, no reduction in worm burden occurred. Durning experimental infection in pigs, there was no booster effect for antibody production to calpain, and this might explain not so good effects as were observed for paramyosin in pig trials. DNA vaccination was also investigated. As a rout of DNA inoculation, intradermal injection at ear pad induced strong antibody production. In our previous results, Th1-dominant responses seem to be important for vaccine effects. In line with this, we tested effects of CpG oligonucleotides in protective immunity to S.japonicum. Mice treated with CpG induced strong Th1 responses and significant reduction in egg granuloma formation in the liver. Intranasal treatment of CpG also induced strong effects comparable to those by intramuscular injection. Considering short half-life of CpG in vivo, repeated treatment is needed. Our intranasal treatment as a non-invasive inoculation is good for repeated treatment of CpG. As a cooperative research with Chinese counterparts, we made progress of calpain vaccine for schistosomiasis japonica, and the near future prospect has been fixed in our research project.