Comparison of four schistosome excretory-secretory antigens: phenol sulfuric test active peak, cathodic circulating antigen, gut-associated proteoglycan, and circulating anodic antigen.

Several carbohydrate-containing antigens of schistosomes have been characterized and tests for these antigens or for the corresponding antibodies are increasingly being used for the diagnosis and clinical analysis of human schistosomiasis. Phenol sulfuric active peak (PSAP) and cathodic circulating antigen (CCA) are 2 soluble glycoproteins found in adult worms of Schistosoma mansoni. These antigens have some similar characteristics including solubility in trichloroacetic acid and non-binding or weak binding to DEAE cellulose which suggests these 2 compounds to be identical. PSAP and CCA were therefore compared using radioimmunoassays employing monoclonal antibodies to CCA and radiolabeled PSAP as well as inhibitory assays using the original glycoproteins as inhibitors. By these criteria PSAP and CCA were found to be different glycoproteins. Using similar techniques, 2 anodic schistosome compounds, gut-associated proteoglycan (GASP) and circulating anodic antigen (CAA) were found to be identical. We now propose to call this later material GASCAP (gut-associated circulating anodic proteoglycan).