ATTACHMENT OF CRYPTOSPORIDIUM-PARVUM SPOROZOITES TO MDCK CELLS IN-VITRO

The initial attachment of Cryptosporidium parvum sporozoites to host c ells in vivo may be a critical event in the pathogenesis of this infec tion. The molecular basis of attachment and the conditions influencing this host-parasite interaction have not been studied systematically. Therefore, we have developed a sporozoite attachment model by using pa raformaldehyde-fixed Madin-Darby canine kidney (MDCK) cells. Attachmen t of sporozoites to fixed MDCK cells was quantitated by indirect immun ofluorescence and confirmed by transmission electron microscopy. Attac hment in this system was time, temperature (37 degrees C), and pH (7.2 to 7.6) dependent. Dose-response studies demonstrated that the attach ment of sporozoites to fixed MDCK cells was a saturable process. Attac hment was enhanced in the presence of 10 mM manganese, 1 mrc I calcium , and 1 to 10 mM zinc. Attachment of sporozoites to MDCK cells was inh ibited in a dose-dependent manner by polyclonal anti-Cryptosporidium a ntisera and by purified immunoglobulin G (IgG). This model will be use ful for the study of parasite and host cell molecules involved in the initial interaction of C. parvum sporozoites with their target cell.