Excretion patterns of mucosally delivered antibodies to p23 in Cryptosporidium parvum infected calves.

Fecal samples obtained at intervals from six calves with acute cryptosporidiosis contained antibodies of multiple isotypes to p23. IgM-, IgA-, and IgG(1)-isotype anti-p23 appeared before IgG(2)-isotype antibodies. All anti-p23 antibodies had declined by 2 months after infection. One calf that failed to shed oocysts following initial exposure developed IgG(1)-isotype anti-p23 antibodies. One calf that died following exposure to Cryptosporidium parvum oocysts lacked detectable anti-p23 antibodies. Re-inoculation with C. parvum resulted in a brief, marked recall response to p23.