Immunological identification of Schistosoma mansoni peptidases

Precipitin arcs formed after immunoelectrophoresis of Schistosoma mansoni egg, worm and cercarial antigens with polyspecific rabbit antisera have been 'stained' at neutral pH with chromogenic enzyme substrates specific for proteases and peptidases. A total of 7 antigenically distinct enzymes with peptidolytic properties were identified. An enzyme which hydrolyzed phenylalanine naphthyl ester bonds was found in adult worm extracts, but appeared to be host-derived in so far as it was also immunoprecipitable from the same extracts by rabbit anti-normal mouse plasma. Three more phenylalanine naphthyl esterases were found, all stage-specific; one was in cercarial homogenates and two were in egg homogenates. A leucine naphthylamidase was also found in egg extracts, and it was antigenically distinct from, and did not react on dipeptide substrates that were hydrolyzed by two other leucine aminopeptidases present in extracts of all three stages of S. mansoni. The method provides a simple means of distinguishing constituents of complex mixtures of antigens by a combination of their immunological and biochemical properties.