Characterization of a high molecular weight antigen of Cryptosporidium parvum micronemes possessing epitopes that are cross-reactive with all parasitic life cycle stages.

Crossreacting antigens between life cycle stages of Cryptosporidium parvum (Protozoa, Apicomplexa) were detected using monoclonal antibodies (mAbs). Shared epitopes were demonstrated by immunoelectron microscopy, at the level of micronemes of the sporozoite and merozoite stages; some dense granules were also labelled but not so intensively. The parasitophorous vacuole membranes of all intracellular stages, the wall-forming bodies of macrogametes and the outer oocyst walls all shared these epitopes. The antigens that bear these epitopes were characterized using the whole oocyst and sporozoite stages as sources of antigenic material. Complex labelling patterns were observed on Western blots. However, all the mAbs used in this study recognized an antigen of more than 500 kDa. The glycoproteinic nature of this antigen was demonstrated by its sensitivity to pronase and periodate treatments. The expression of this high molecular weight immunoreactive antigen in the intracellular stages of C parvum was not investigated and remains to be found.