Immunoaffinity fractionation of Schistosoma mansoni worm antigens using human antibodies and its application for serodiagnosis.

A crude Schistosoma mansoni soluble worm antigen preparation (SWAP) was fractionated using an immunoaffinity column consisting of specific human anti-SWAP antibodies obtained from chronic S. mansoni-infected human sera and bound to CNBr-activated Sepharose 4B. The chromatographic separation resulted in three fractions: the unbound material (FW), and the eluted antigens with glycine-HCl (F1) and glycine-HCl-NaCl (F2). Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the purified antigens F1 and F2 consisted of several bands when stained with Coomassie blue and silver stain, with molecular weights between 20 X 10(3) and 200 X 10(3). The F1 and F2 fractions in addition to FW and SWAP were used in an enzyme-linked immunosorbent assay (ELISA) to measure antibody levels in sera from schistosomiasis patients. Each individual serum assessed with the purified F2 antigen gave 100% positivity and three to four times higher optical density in comparison to SWAP with only 88% positivity. No detectable cross-reactive antibodies against F2 were found when a limited number of sera from filariasis, fascioliasis and trichinellosis patients were screened. Furthermore, F2 was also used and found to be more sensitive generally in detecting anti-adult worm antibodies than SWAP in recently schistosomiasis-infected persons. Thus, F2 appears to be a highly sensitive and specific reagent for the serodiagnosis of schistosomiasis infection.