Quantitative determination of circulating antigens in human schistosomiasis mansoni using an indirect hemagglutination assay.

In serum and urine specimens collected from a group of Schistosoma mansoni infected individuals from Makundju, Zaire, the schistosome circulating anodic antigen (CAA) and the circulating cathodic antigen (CCA) were quantitatively determined using an indirect hemagglutination reaction with sheep erythrocytes sensitized with mouse IgM monoclonal antibodies directed against these circulating antigens. Levels of CAA in serum (up to 5 ng/ml) and CCA in serum and urine (up to 50 ng/ml) were strongly correlated with egg excretion and with each other. No correlation was found between egg excretion and antibody levels against the circulating antigens. Antigen was detectable only in patients excreting greater than 500 eggs per gram of feces.