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Anti-Adult Worm Antibodies From Irradiated Cercariae-Immunized Rabbits Passively Transfer Immunity To Schistosoma haematobium-Infected Mice.

Sherif H. Abdeen.

Zoology Department, Faculty of Science, Mansoura University, Mansoura, Egypt.

Multiple vaccination with UV-irradiated cercariae results in the induction of high levels of immunity to subsequent infection. In both Schistosoma mansoni and S. japonicum, sera of vaccinated animals passively transfer immunity to naive ones indicating an important role of humoral responses. In an attempt to identify the humoral responses associated with S. haematobium UV-irradiated cercariae vaccine model, adult worm-specific antibodies (RAb1) were isolated by affinity chromatography from sera of rabbits multiply immunized (VRS) with UV-irradiated cercariae. RAb1 showed an isotypic constitution of IgG and IgM and recognized epitopes shared by soluble extracts of adult worms, 3hr schistosomula and to lesser extent eggs. By indirect immunofluorescence assay, RAb1 recognized epitopes on the surface of 3hr schistosomula (the presumed target for complement-mediated killing). RAb1 mediated ~ 97% killing of schistosomula in antibody dependent complement-mediated cytotoxicity assays (ADCC). In passive immunization experiments, RAb1 provided ~ 54% protection to naive C57BL/6 mice. The efficacy of VRS to mediate ADCC mechanisms  (95%) as well as its ability to confer passive protection (~ 51%) was not significantly different from that of RAb1. These results confirm a role of antibody-dependent responses in UV-irradiated S. haematobium cercariae vaccine model.