Enzyme immunoassay detection of Cryptosporidium parvum inhibition by sinefungin in sporozoite infected HCT-8 enterocytic cells

Complete parasite development was obtained in differentiated human enterocytic HCT-8 cells infected at confluence with Cryptosporidium parvum sporozoites, and evaluated in a quantitative enzyme imunoassay. Forty-eight hours after infection, a linear correlation was found between optical density values and the number of parasites determined in an immunofluorescent assay. Sinefungin exerted an inhibitory effect when added within 4 h after sporozoite addition to HCT-8 cultures (MIC50 = 38 mu mol L-1). while the inhibitory effects of paromomycin and pentamidine dimethanesulfonate were also easily detected (MIC50 = 0.87 mu mol L-1 and 0.27 mu mol L-1, respectively). Except for high pentamidine dimethanesulfonate concentrations, no alteration in optical microscopy morphology or trypan blue exclusion of HCT-8 cells was observed in the presence of anticryptosporidial agents, which suggests that they were primarily active against developing parasites. Data suggest that EIA detection of C. parvum development in sporozoite-infected HCT-8 cells provides an accurate and convenient model for in vitro evaluation of parasite infectivity, growth and response to anticryptosporidial agents. (C) 1999 Australian Society for Parasitology. Published by Elsevier Science Ltd. All rights reserved.