Two hybridoma cell lines against Cryptosporidium parvum oocysts (VRI- CN91) were produced. The isotype of these 2 monoclonal antibodies (mAbs) was IgG2b (1E7.2) and and IgM (C6). Enzyme immuno-transfer blotting analysis showed that 1E7.2 reacted specifically to 36 kDa protein and C6 reacted to 67 and 70 kDa proteins. C. parvum was bound specifically to the surface region of oocysts by these mAbs. No cross- reactivity was observed with tachyzoites of Toxoplasma gondii and oocysts of Eimeria zuernii, E. bovis and E. canadensis of bovine origin. The indirect immunofluorescence assay (IIF) using mAb C6 was successful with counterstain. With the IIF using mAb C6, oocysts appeared as 3 to 5 microns spherical objects fluorescing bright apple green against a reddish dark background. The IIF using mAb C6 was agreed in specificity and sensitivity with those of a commercial diagnostic kit. These results demonstrated that the produced mAbs were specific to C. parvum and that the mAb C6 could be used for diagnosis of cryptosporidiosis.
