ACTIN-DEPENDENT MOTILITY IN CRYPTOSPORIDIUM-PARVUM SPOROZOITES

The present study investigated the role of actin polymerization and my osin motor protein activity in the gliding motility of Cryptosporidium parvum sporozoites. Short motility trails were detected using an indi rect immunofluorescent assay (IFA) with a polyclonal antisporozoite an tibody following incubation of sporozoites on poly-L-lysine-coated gla ss slides. Sporozoite motility was blocked following exposure to cytoc halasin D, a myosin light-chain kinase inhibitor naphthalene-1-sulfony l)-1H-hexhydro-1,4-diazapine, and the myosin ATPase inhibitor 2,3-buta nedione monoxime. Sporozoites were observed to form rounded, blunt-end ed shapes when exposed to these same inhibitors. Incubation of purifie d oocysts with these compounds did not significantly inhibit in vitro excystation or subsequent infectivity in cultured epithelial cells. In direct LFA revealed a uniform distribution of actin protein throughout the body of the sporozoite; immunoelectron microscopy confirmed a dif fuse intracellular pattern of gold particles in excysted sporozoites. Collectively, these findings show that sporozoite motility is dependen t upon an intact actin-myosin motor system, and the dynamic interactio n of F-actin and myosin motor proteins has a further role in maintaini ng the structural integrity of excysted sporozoites. Further, in vitro excystation and infectivity of C. parvum occurs in the absence of dyn amic sporozoite locomotion.