Protection of infection using monoclonal antibody produced by Schistosoma japonicum cercariae attenuated by ultra violet-irradiation.

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BALB/c mice were immunized with cercariae of Schistosoma japonicum attenuated by irradiation with ultra violet ray at 254 nm. The highest protection attained was 47.3% by immunization with cercariae irradiated by UV at 500 mW sec/ <cm^2> . Mice were immunized with UV-attenuated cercariae and monoclonal antibodies (McAb) were produced by fusion of spleen cells from these mice. Twelve McAb, which recognized the surface of 24 hour-schistosomula by immunofluorescence, were selected and examined for reactivity to all stages of worms. Using these 12 McAb, antigenic similarity was examined between lung schistosomula and immature worms in the liver. Both were found to be close since the surface of both stages was recognized by 7 McAb and both were not by 1 McAb. The lung schistosomula, however, had a slightly different antigenicity because they were not recognized by 3 McAb which recognized immature worms in the liver. Protection of infection was examined in mice by injectng ascitic fluid of 4 McAb which recognized the surface of lung schistosomula, and 2 McAb showed comparatively high protection rates at 21.2 and 18.0%, respectively, and bound strongly to the tegument of adult and also to the parenchyma of adult worms and the egg. The killing effect of McAb on schistosomula was examined in vitro. They were damaged and killed by mouse neutrophils with the McAb, which bound to the surface of adult worms, supplemented with complement. Since these effective McAb recognized the common epitope distributed in the parenchyma and surface of adults, it was suggested that adult worms, in place of schistosomula, would be used as the source of material for obtaining antigens to induce the protective immunity.