Antigen incorporation on Cryptosporidium parvum oocyst walls

Cryptosporidium parvum oocysts are the infective stages responsible for tra nsmission and survival of the organism in the environment. In the present w ork we show that the oocyst wall, far from being a static structure, is abl e to incorporate antigens by a mechanism involving vesicle fusion with the wall. and the incorporation of the antigen to the outer oocyst wall. Using immunoelectron microscopy we show that the antigen recognized by a monoclon al antibody used for diagnosis of cryptosporidiosis (Merifluor(R), Meridian Diagnostic Inc.) could be found associated with vesicles in the space betw een the sporozoites and the oocysts wall, and incorporated to the outer ooc yst wall by an unknown mechanism.