TOXOPLASMA-GONDII - A FAMILY OF APICAL ANTIGENS ASSOCIATED WITH THE CYTOSKELETON

Antigens associated with the conoid and apical pellicle in Apicomplexa n parasites have previously been defined by a panel of monoclonal anti bodies that recognize distinct but overlapping protein subsets (Morris sette et al. 1994). To probe the association of these antigens with th e apical membrane skeleton of Toxoplasma gondii, we examined their dis tribution in detergent-extracted tachyzoites and in intracellular para sites treated with drugs that disrupt microtubules. Although intact pa rasites are labeled only at their extreme apex, immunogold localizatio n in detergent-extracted tachyzoites indicates that the antigens under study are associated with the subpellicular microtubules along their full length. Brief treatment with oryzalin, which results in dissociat ion of subpellicular microtubules from the pellicle, permits identific ation of the apical antigens farther along the length of the parasite. Longer dinitroaniline treatment completely eliminates the subpellicul ar microtubules, after which the apical antigens are found as insolubl e patches associated with the parasite pellicle. Taken together, these observations argue that the apical antigens under study are present a long the entire microtubule in intact parasites but are inaccessible t o antibody binding. In turn, this suggests that these antigens may pla y a role in the close association of microtubules with the parasite pe llicle. (C) 1998 Academic Press.