CRYPTOSPORIDIUM-PARVUM INFECTION OF CACO-2 CELL MONOLAYERS INDUCES AN APICAL MONOLAYER DEFECT, SELECTIVELY INCREASES TRANSMONOLAYER PERMEABILITY, AND CAUSES EPITHELIAL-CELL DEATH

Caco-2 cells were grown on permeable filters:and infected with Cryptosporidium parvum. Infection rates exceeded 50% of target cells with a sufficient inoculum dose of parasites. Infection induced a dose- and time-dependent fall in transmonolayer resistance, which was closely related to both the inoculum dose and the number of parasites detected by immunofluorescence. Caco-2a, MDBK, and MDBK subclone F5D2 evidenced similar declines in resistance when grown and infected under similar circumstances. Caco-2. monolayers became permeable to molecules of less than or equal to 1,000 Da but continued to remain impermeable to exogenously added, or endogenously produced, proteins of greater than or equal to 1,881 Da. We found that infected monolayers released up to 50% of the total cellular lactase dehydrogenase into apical media, but not basal media, and that the vital dye propidium iodide avidly stained infected cells, and often parasites, when added to the apical reservoir. Cryptosporidium infection of Caco-2 monolayers increases transmonolayer permeability, induces an apical cellular and monolayer defect, and causes cell death.