Schistosoma mansoni: characterization of two protective monoclonal antibodies.

Two monoclonal antibodies against the surface of S. mansoni schistosomula were found to confer significant passive protection to mice (M7B3A, range 28-70%; M22H12C, range 14-58%). No additive effect was observed when both were transferred together. Neither McAb bound to the cercarial surface but both bound to the surface of in vitro derived schistosomula and schistosomula recovered from mouse skin up to 3 days after infection. The McAbs were species specific, but not S. mansoni strain specific. M22H12C immunoprecipitated an 125I-labelled surface antigen of relative molecular weight (mol. wt) 32 000. In Western blotting of an NP40 schistosomular extract, M7B3A recognized an antigen smear of 13 000-18 000 with a dominant band at 16 000. This 16 000 antigen was recognized by serum from demonstrably immune mice and rats vaccinated with highly irradiated carcariae but not by sera from mice with chronic single sex or bisexual infections.