Schistosoma: analysis of monoclonal antibodies reactive with the circulating antigens CAA and CCA

Abstract

Using spleen cells of mice infected or immunized respectively with cercariae or antigen preparations of Schistosoma mansoni, S. haematobium or S. japonicum monoclonal antibodies (mAbs) were produced against the schistosome gut-associated antigens CAA (circulating anodic antigen) and CCA (circulating cathodic antigen). Fusions nearly exclusively produced either anti-CAA (n = 25) or anti-CCA mAbs (n = 55) with a strong isotype restriction (IgM, IgG1 and IgG3) against both antigens, the majority of anti-CAA mAbs being IgG1 and the majority of anti-CCA mAbs being IgM. The mAbs, which on the basis of their selection were reactive with multiple carbohydrate epitopes of CAA or CCA, were applied in different immunological techniques including immunofluorescence, a dot immunobinding assay and immunoelectrophoresis to study the epitope repertoire. Anti-CAA mAbs were found to be reactive with 5 different epitopes, none of which occurred as multiple epitopes on eggs. Anti-CCA mAbs, on the other hand, recognized at least 10 different epitopes, while 44% of anti-CCA mAbs recognized epitopes common to the adult worm and the egg. Both CAA- and CCA-epitopes were found to be developmentally expressed at the level of the tegument in cercariae, schistosomula and 5-day-old lung worms, but in the adult worm were primarily found in the gut. Thus, the production of panels of mAbs has not only resulted in the selection of reagents optimally performing in diagnostic immunoassays, but also allowed a more detailed study of the epitope repertoire of these important schistosome antigens.