Evaluation of an ELISA for combined measurement of CAA and CCA in schistosomiasis mansoni.

An enzyme-linked immunosorbent assay was developed for combined measurement of schistosome circulating anodic antigen (CAA) and circulating cathodic antigen (CCA). Monoclonal antibodies against CAA and CCA were used as coating and as fluorescein-labeled detecting antibodies in a FITC-anti-FITC system. The lower detection limit of the assay was 1.1 ng antigen (AWA-TCA)/ml. Serum samples of Schistosoma mansoni infected individuals from Zaire (n = 60) and Burundi (n = 60) were tested in this assay and in single-antigen ELISAs. Sensitivities of assaying for CAA, CCA, combined CAA + CCA, and of parallel testing for CAA and for CCA were calculated from titres and antigen concentrations. With serum samples from the heavily infected individuals (Zaire), all assays had a sensitivity of 97% or higher. In contrast, with serum samples from individuals from Burundi (low to moderate infections) it was shown that combined testing resulted in a slightly lower sensitivity than testing for individual antigens. By parallel testing for CAA and CCA, the sensitivity could be increased considerably (to 95%), however.