Identification of low-molecular-mass coproantigens of Cryptosporidium parvum

Cryptosporidium parvum coproantigens (CCAg) of 18 and 20 kDa were identified in the stool eluates of calves and humans infected with Cryptosporidium species. Monospecific antibodies raised against the 20-kDa antigen recognized both 18- and 20-kDa CCAg in all positive but no negative control samples. These antibodies reacted with C. parvum sporozoites in an immunofluorescence assay. Human immune sera recognized the 20-kDa antigen in infected calf stool eluates. Both 18- and 20-kDa CCAg remained intact in commonly used preservatives and at various temperatures. These CCAg may be useful in designing sensitive, reliable methods for diagnosing cryptosporidiosis.