Detection of the schistosome circulating cathodic antigen by enzyme immunoassay using biotinylated monoclonal antibodies

We have developed an enzyme immunoassay (EL-ISA) for the quantification of the schistosome circulating cathodic antigen (CCA), a glycoprotein associated with the syncitium lining the gut of the parasite. A mouse monoclonal antibody of IgG 3 isotype was used as coating (antigen-capture) antibody, while a biotinylated mouse monoclonal IgM was used as second (antigen-detecting) antibody. Streptavidin-alkaline phosphatase was used as enzyme label. The lower detection limit of the assay was 1·0 ng of the trichloroacetic acid soluble fraction of adult worm antigen (AWA-TCA) per ml, which corresponds to approximately 0·2 ng CCA per ml. The ELISA showed a linear range from 1·0 to 62·5 ng AWA-TCA per ml. Serum and urine samples of 16 individuals infected with Schistosoma mansoni (egg counts ranging from 5 to 4820 eggs per gram of faeces) were tested in the assay. Antigen titres ranged from