HOMOLOGOUS AND HETEROLOGOUS PROTECTIVE IMMUNITY TO EGYPTIAN STRAINS OF SCHISTOSOMA-MANSONI AND SCHISTOSOMA-HAEMATOBIUM INDUCED BY ULTRAVIOLET-IRRADIATED CERCARIAE

C57BL/6 and Balb/c mice were immunized with ultraviolet-irradiated cer cariae of Egyptian strains of Schistosoma mansoni and S. haematobium, challenged with non-irradiated irradiated cercariae of the homologous or heterologous species, and assayed for protection against challenge infection by comparing the adult worm burdens of immunized and non-imm unized mice. Homologous protection (per cent reduction in worm recover y) ranged from 56% to 69% for S. mansoni and 88% to 99% for S. haemato bium. Significant heterologous protection was consistently induced aga inst S. haematobium by immunization with S. mansoni, but not against S . mansoni by immunization with S. haematobium. These results are discu ssed in relation to those of previous studies and in terms of implicat ions for vaccine development.