Isolation and specific detection of two major schistosoma gut-associated circulating antigens

Objectives To investigate the nature of the common epitopes of Schistosoma japonicum ( S. japonicum) circulating anodic (CAA) and circulating cathodic antigen (CCA) and to try to obtain sufficient purified material to set up a standard series for quantitative determinations. Methods Isolation of the two worm fractions from a trichloroacetic acid (TC A) soluble preparation of S, japonicum adult worm antigen (AWAj-TCA) via Mo no-Q anion exchange chromatography was performed and analysis of specific r eactivity of the eluted fractions was done by antigen-capture Enzyme Linked Immune Sorbent Assay (ELISA) specific for CAA or CCA with reference to aff inity purified preparations of S. mansoni CAA and CCA. Results When an ionic strength gradient was used, CCA was eluted in two maj or peaks, an unbound fraction CCA-1, and a major bound fraction, CCA-2. Two additional minor peaks, CCA-3 and CCA-4, were eluted at higher ionic stren gths. CAA was only detected in the bound fraction, partly overlapping with CCA-3. In the CCA-1 and CCA-2 fractions, reactivity was only found in the a ntigen-capture ELISA using anti-CCA McAbs both for capture and detection. T he CAA fraction was predominantly found to be positive in the antigen-captu re ELISA using anti-CAA McAbs both for capture and detection. However, in E LISA using combined anti-CCA and anti-CAA McAbs for capture and detection, this fraction showed some reactivity. Conclusion The two CCA fractions contain molecules which bear at least two CCA-epitopes; the CAA fraction contains molecules which contain at least tw o CAA-epitopes, and one CCA-epitope.