In vitro screening of therapeutic agents against Cryptosporidium: hyperimmune cow colostrum is highly inhibitory.

An in vitro model of Cryptosporidium parvum infection was developed utilizing an adherent human intestinal epithelial cell line HT29.74. The efficacy of potential immunologic therapy in the form of Cryptosporidium-specific hyperimmune bovine colostrum was evaluated for the ability to inhibit in vitro infection. Oocysts were purified from stool of chronically infected AIDS patients. Hyperimmune colostrum obtained from cows immunized with Cryptosporidium and nonimmune conventional colostrum were evaluated. oocysts (10(5)-10(6)) were pre-incubated with either hyperimmune colostrum, conventional colostrum, or saline as control, for 15 min at room temperature than applied to a 70% confluent monolayer of HT29.74 cells. Cryptosporidium schizonts were identified and counted per 1,000 HT29.74 cells under oil immersion after 24 h. In the presence of hyperimmune colostrum, parasite infection was inhibited by 82% (p less than 0.001), and the presence of conventional colostrum, infection was inhibited by 67% (p less than 0.001). Treatment with the soluble fraction of hyperimmune colostrum resulted in 69% inhibition (p less than 0.001) compared to the soluble fraction of conventional colostrum which resulted in only 17% inhibition (p = NS). In vitro Cryptosporidium parvum infection of the differentiated human enterocyte cell line HT29.74 is a viable method for screening immunologic therapies. Hyperimmune bovine colostrum was highly inhibitory of Cryptosporidium infection in vitro and its soluble fraction remained significantly inhibitory while the soluble fraction of conventional colostrum did not.