Anti-Cryptosporidium parvum antibodies inhibit infectivity in vitro and in vivo.

Cryptosporidium parvum causes acute diarrhea in immunocompetent individuals and a severe life-threatening disease in immunocompromised individuals, including AIDs patients. No efficacious therapy for cryptosporidiosis has yet been reported. However, treatment of some patients with cryptosporidiosis with hyperimmune bovine colostrum has ameliorated or eliminated clinical symptoms. Consequently, it is important to identify and characterize C. parvum antigens which are the targets of protective antibodies to facilitate the development of more efficacious therapy. We report that hyperimmune bovine colostral immunoglobulin inhibits C. parvum infectivity in a reproducible in vitro assay, and we correlate this inhibition with the protective capacity of the bovine colostrum in vivo. We have also identified the major C. parvum sporozoite antigens recognized on Western blots (immunoblots) by this colostral immunoglobulin preparation. Antibodies that recognize some surface molecules of other Apicomplexan parasites are protective in vivo. Consequently, we radioiodinated membrane proteins of sporozoites and immunoprecipitated 19 molecules which are the target of immunoglobulin that is protective in vivo and in vitro.