Schistosoma mansoni: in vivo and in vitro studies of immunity using the guinea-pig model.

In vivo and in vitro parameters of immunity have been assessed in guinea-pigs sensitized with 500 normal or 500 radiation-attenuated cercariae of Schistosoma mansoni. High levels of resistance to a challenge infection developed in both the chronic and irradiated vaccine model, but immunity was expressed earlier (week 4) and reached higher levels (90%) in the latter case. Vaccinated guinea-pigs have thus been shown to achieve greater resistance than the more commonly used rodent hosts. In vitro cytotoxicity assays have demonstrated that antibodies capable of participating in complement-dependent (lethal antibody) or eosinophil-mediated schistosomular killing, develop in the serum of guinea-pigs immunized with either normal or irradiated cercariae. The time course of development of the eosinophil adherence promoting antibody approximated in both models, the development of immunity in vivo, but the lethal antibody response paralleled the immune status of the animal only in the irradiated vaccine model.