Recognition of gut-associated antigens by immunoglobulin M in the indirect fluorescent antibody test for schistosomiasis mansoni.

The specific reactivity of immunoglobulin M antibodies, as measured by a commonly used immunodiagnostic technique for schistosomiasis mansoni, the immunofluorescence assay (IFA) on Rossman-fixed sections of adult worms, was analyzed with monoclonal antibodies. Using monoclonal antibodies directed against 3 major gut-associated antigens, circulating anodic antigen (CAA), circulating cathodic antigen (CCA) and the 32 kDa antigen in blocking experiments, it was demonstrated that the measured IFA reaction was primarily due to reactivity with CCA. After blocking with anti-CCA monoclonal antibody, a mean decrease of fluorescent antibody titres of 95.8%, 92.9% and 83.8% was observed for sera from groups of patients with a recent infection (0-6 months), a static infection (6 months - 5 years), and a chronic infection (over 5 years), respectively. Titres of the group of recently infected patients were, after blocking, significantly lower (P less than 0.05) than those of the group of chronically infected patients.