Analysis and antigenic activity of a carbohydrate fraction derived from adult Schistosoma mansoni.

The antigenic constituents of a crude predominately carbohydrate trichloroacetic acid soluble fraction of adult Schistosoma mansoni (TCA-S-C) were determined by comparing the antibody levels in human infections with crude TCA-S-C and fractions obtained after DEAE chromatography. Antibodies were measured using ELISA tests employing poly(L-lysine)-coated and uncoated polystyrene plates as well as radioimmunoassays to the 2 active fractions. Two active materials were identified. Acute and early infected patients had high levels of antibody to the previously characterized purified gut-associated proteoglycan (GASP), whereas the heavily infected chronically exposed patients had elevated levels to another fraction, PSAP. IgG levels to PSAP correlated significantly with the egg excretion rate. Both the acute and early infected as well as the chronically exposed patients had raised levels of antibody to crude TCA-S-C but no correlation with egg excretion or acuteness of infection. Therefore, the measurement of antibodies to specific schistosome components unmasked clinically relevant correlations that were not apparent when crude fractions were used. The pattern of response was similar whether ELISA or radioimmunoassays were used, although the radioimmunoassays were found to be more sensitive and specific. Antibody levels to GASP significantly correlated with the immunofluorescent antibody titer to schistosome gut epithelial cells. PSAP was characterized as a polydisperse PAS-positive staining material composed primarily of substances(s) with an apparent m.w. ranging from 130,000 to 90,000. The composition of this material as revealed by earlier studies suggested that PSAP was a glycoprotein(s).