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

Caco-2 cells were grown on permeable filters:and infected with Cryptos poridium parvum. Infection rates exceeded 50% of target cells with a s ufficient inoculum dose of parasites. Infection induced a dose- and ti me-dependent fall in transmonolayer resistance, which was closely rela ted to both the inoculum dose and the number of parasites detected by immunofluorescence. Caco-2a, MDBK, and MDBK subclone F5D2 evidenced si milar declines in resistance when grown and infected under similar cir cumstances. Caco-2. monolayers became permeable to molecules of less t han or equal to 1,000 Da but continued to remain impermeable to exogen ously added, or endogenously produced, proteins of greater than or equ al to 1,881 Da. We found that infected monolayers released up to 50% o f the total cellular lactase dehydrogenase into apical media, but not basal media, and that the vital dye propidium iodide avidly stained in fected cells, and often parasites, when added to the apical reservoir. Cryptosporidium infection of Caco-2 monolayers increases transmonolay er permeability, induces an apical cellular and monolayer defect, and causes cell death.