LOCALIZATION OF PARASITE ANTIGENS IN CRYPTOSPORIDIUM-PARVUM INFECTED EPITHELIAL-CELLS USING MONOCLONAL-ANTIBODIES

An immunogold ultrastructural study was made of Cryptosporidium parvum -infected intestinal cells from SCID mice to locate parasite antigens recognized by monoclonal antibodies raised against sporozoite or oocys t wall antigens. The results suggested that these antigens were presen t in more than one life-cycle stage and demonstrated that the intracel lular parasite modified the parasitophorous vacuole membrane and villo us membrane surrounding the parasite. In an immunofluorescence antibod y test monoclonal antibody (MAb) 1B5 reacted with the oocyst wall, MAb 2C3 with the whole sporozoite and MAb 2B2 with the sporozoite surface . Western and dot-blot studies demonstrated that different carbohydrat e epitopes were recognized by the respective sporozoite-reactive antib odies. In the ultrastructural examination MAb 1B5 reacted with macro- and microgametocytes as well as the oocyst wall. In the macrogametocyt e MAb 1B5 recognized the large electron-dense bodies characteristic of this stage and, in some parasites, the parasitophorous vacuole and th e parasite pellicle. The sporozoite-reactive MAbs were able to bind to all developmental stages. These antibodies recognized the parasite cy toplasm and, additionally, MAb 2B2 produced substantial labelling of t he parasite membrane. Significantly, both these antibodies also detect ed antigen in the parasitophorous vacuole membrane and, to a lesser ex tent, the villous membrane surrounding the parasite.