Homologous and heterologous protective immunity to Egyptian strains of Schistosoma mansoni and S-haematobium induced by ultraviolet-irradiated cercariae

C57BL/6 and Balb/c mice were immunized with ultraviolet-irradiated cercariae 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-immunized mice. Homologous protection (per cent reduction in worm recovery) ranged from 56% to 69% for S. mansoni and 88% to 99% for S. haematobium. Significant heterologous protection was consistently induced against S. haematobium by immunization with S. mansoni, but not against S. mansoni by immunization with S. haematobium. These results are discussed in relation to those of previous studies and in terms of implications for vaccine development.