PARTIAL CHARACTERIZATION AND KINETICS OF EXPRESSION OF SM15, A SCHISTOSOMA-MANSONI TEGUMENTAL ANTIGEN

Differential antibody screening of an adult Schistosoma mansoni cDNA e xpression library constructed in lambda gt11 identified a partial cDNA clone, A70. This cDNA encodes a fusion protein recognized by antibodi es raised against highly irradiated schistosomula and adult worm tegum ental membranes but not by anti-egg antibodies. Anti-tegumental membra ne antisera affinity-purified on the A70 cDNA fusion protein were used for Western blotting analysis and indirect immunofluorescence, result ing in the identification of a 15-kDa protein (Sm15) in the tegument o f adult worms. This is one of the principal tegumental antigens recogn ized by antibodies from mice protectively vaccinated with adult worm t egumental membranes. Sm15 is much smaller than the protein encoded by its gene, suggesting that it results from a highly processed precursor . It was found that Sm15 behaves as an integral membrane protein upon partitioning in Triton X-114 and that it is present in worms of 2 week s or older but not in schistosomula or miracidia. The affinity-purifie d antibodies also revealed the presence of a 23-kDa antigen in whole-w orm homogenates that is apparently coexpressed with Sm15. The 23-kDa a ntigen was not found associated with membranes and is probably a solub le protein. A further series of Western blots were undertaken using an tibodies affinity-purified from serum raised against schistosomula. In this case, the 23- and 15-kDa products were not recognized, but rathe r soluble proteins ranging from 45- to 150-kDa were detected in almost all larval stages investigated. The results suggest that the precurso r is differentially processed during maturation.