Proteosome delivery of a protective 9B-antigen against Schistosoma mansoni.

We have previously characterized a stage specific, partially protective protein denoted 9B-antigen. This antigen is of 450 kDa in its native form but upon SDS-PAGE in reducing conditions it exhibits two subunits of 30 kDa and 45 kDa. The 9B-antigen is localized at the surface of schistosomula and persists at the surface of lung schistosomula. The 9B-antigen is also localized in internal organs of a vital function in the parasite such as flame cells and cytoplasmic tubes. Infected individuals or mice vaccinated with irradiated cercariae recognize the 9B-antigen. We have previously shown that when injected with complete Freunds adjuvant, the 9B-antigen can induce 40% protection against challenge infection. In this study we have used a more effective delivery system for this antigen. The 9B-antigen was coupled to proteosomes derived from meningoccocal outer membrane proteins. Vaccination of mice with this complex increased the protection level to 60%. Sera from these vaccinated mice induced high levels of complement mediated cytotoxicity of the parasite. Since the proteosomes are approved for human use, these results are promising towards the development of a vaccine against schistosomiasis.