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.