Specific IgA antibody response to coproantigens of Cryptosporidium parvum in serum and saliva of calves after experimental infection.

The antibody response to coproantigens of Cryptosporidium parvum was examined in saliva and sera of calves experimentally infected with C. parvum. Coproantigens of C. parvum with approximate molecular masses of 17, 15 and less than 14kDa were found in the feces of infected calves on day 3 or later, and 60 and 23kDa coproantigens observed between days 4 and 9 post-infection, respectively. The antibody reactivity to the coproantigens was mainly attributable to IgA class antibodies in saliva and was detectable during the convalescent phase of infection. A 15kDa protein isolated from the feces of infected calves by immunoaffinity adsorption using a monoclonal anti C. parvum antibody was recognized by IgA antibodies present in the saliva during the convalescent phase of infection. These results suggest that this coproantigen may be released from C. parvum sporozoites and may induce IgA antibody production in the mucosal immune system of infected calves.