Induction of a protective immune IgE response in rats by injection of defined antigens of schistosomulum-released products: immunochemical properties of the target antigens.

Brown Norway rats were injected without adjuvant with the soluble products liberated in a 16-hour culture by schistosomula (schistosomula-released products, SRP-A). A strong cytotoxic and protective IgE response was elicited, mainly directed against 22- and 26-kilodalton (kDa) SRP-A molecules. In the present study, we have attempted to characterize further those molecules. Metaperiodate denaturing treatment of the SRP-A glycans before injection into rats did not modify the immunogenicity of the SRP-A antigens. Results obtained by lectin affinity suggested that the 22- and 26-kDa molecules were glycoconjugates binding to ConA. Preparative sodium dodecylsulfate electrophoresis has allowed the separation of enriched fractions of 22- and 26-kDa molecules which have been injected separately into rats. The corresponding sera were tested in antibody-dependent cell cytotoxicity and displayed a significant cytotoxic IgE response (65 and 53%, respectively) towards the larvae. These results lend further support to the view that the 22- and 26-kDa antigens are the major targets of the protective IgE response and thus appear as potentially protective antigens.