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

ABSTRACT

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 (TCA) soluble preparation of S. japonicum adult worm antigen (AWAj-TCA) via Mono-Q anion exchange chromatography was performed and analysis of specific reactivity of the eluted fractions was done by antigen-capture Enzyme Linked Immuno Sorbent Assay (ELISA) specific for CAA or CCA with reference to affinity purified preparations of S. mansoni CAA and CCA. RESULTS: When an ionic strength gradient was used, CCA was eluted in two major 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 strengths. 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 antigen-capture ELISA using anti-CCA McAbs both for capture and detection. The CAA fraction was predominantly found to be positive in the antigen-capture ELISA using anti-CAA McAbs both for capture and detection. However, in ELISA using combined anti-CAA 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 two CAA-epitopes, and one CCA-epitope.