DETECTION OF IGM ANTIBODIES DIRECTED AGAINST THE GUT-ASSOCIATED CIRCULATING CATHODIC ANTIGEN IN SERA FROM SCHISTOSOMA-MANSONI INFECTED PATIENTS - DEVELOPMENT AND COMPARISON OF 3 ENZYME-LINKED IMMUNOASSAYS

The majority of the human IgM antibodies detected with an immunofluore scence assay (IFA) on adult worms are directed against the gut-associa ted circulating cathodic antigen (CCA). In order to study this phenome non further we developed and evaluated three related ELISA methods to specifically detect IgM antibodies against purified CCA. The assays em ployed 1) direct coating of CCA, 2) indirect coating of CCA via a mono clonal antibody, and 3) IgM antibody-capture by rabbit anti-mu chain a ntibodies. Using a group of 46 positive sera, it was found that the th ree ELISA's and the IFA were significantly correlated. To discriminate between positive and negative sera we used a cut-off level of average reactivity + 3 standard deviations of 50 negative sera. False negativ e reactions were not found in any of the ELISA's, while both in the di rect and indirect ELISA one false positive reaction occurred. For furt her studies or diagnostic use the antibody-capture ELISA is recommende d.