Characterization of Schistosoma mansoni 44.7/56.8 kDa egg antigens recognized by human monoclonal antibodies which induce protection against experimental infection and proliferation of peripheral blood mononuclear cells from schistosomiasis patients

We described here the characterization of Schistosoma mansoni egg antigens recognized by human monoclonal antibodies BIO (HmAb-B10) and D5 (HmAb-D5). SDS-PAGE and Western blot analysis revealed that these monoclonals recognized two antigens of M W 44.7/56.8 kDa, with pI of 7.0 and 7.8, respectively. The passive transfer of B10 and D5 induced a significant protection of 48% and 54% in Balb/c mice. Results of in vitro cytotoxicity assay showed that both monoclonals were able to kill schistosomula in the presence of rabbit complement. These monoclonals mediated 48% and 74% of schistosomula cytotoxicity, respectively. Egg antigens were purified by affinity chromatography using monoclonal antibodies B10 and D5. Treatment of purified antigen with periodate, galactose oxidase and trifluoromethane sulphonic acid did not prevent binding by B10 and D5 in ELISA assay. However, the treatment with pretense K and 2-mercaptoethanol affects the antibodies binding, showing that the HmAbs B10 and D5 recognize polypeptide epitopes. Vaccination of mice with these antigens in Freund's adjuvant induced 43% reduction in worms burden after challenge with S. mansoni cercariae. In vitro blastogenesis assays with peripheral blood mononuclear cells from patients infected with S. mansoni revealed that purified antigens were able to induce significant cell proliferation. (C) 1997 Elsevier Science Ltd.