Detection of mucosally delivered antibody to Cryptosporidium parvum p23 in infected calves.

We have developed an assay to detect mucosally delivered antibody to Cryptosporidium parvum sporozoite antigens. We absorbed a recombinant 23-kD sporozoite protein to polystyrene microspheres, and used flow cytometry to detect, titer, and determine the isotype of antibody to p23 that was shed in the feces of experimentally infected calves. Noninoculated calves have low levels of mucosal antibody to p23, with IgG1 as the predominant isotype. Antibody titers rise in inoculated calves as the animals recover from cryptosporidiosis. A calf that was naturally protected from cryptosporidiosis had mucosal IgM and IgG1 isotype anti-p23 antibodies prior to challenge with C. parvum oocysts. Ten days after challenge, the calf had high titers of IgM, IgA, IgG1, and IgG2 anti-p23 antibodies. Together, the data show that this method can be used to assess mucosally delivered antibody to C. parvum.