Immunological characterization of a 17‐kDa antigen from Cryptosporidium parvum recognized early by mucosal IgA antibodies

Cryptosporidium parvum antigens were characterized by immunoblot analysis of sera and intestinal secretions of BALB/c mice orally infected with 105 oocysts. A major band at 17 kDa under non‐reduced conditions and at 18 kDa under reduced conditions was recognized by anti‐C. parvum IgA and IgG in serum and intestinal secretions from day 15 post‐infection. This recognition persisted throughout the experiment (day 30). Mouse‐serum antibodies raised against the 17‐kDa purified antigen (P17) showed no cross‐reactivity with other C. parvum antigens. Immunofluorescence study revealed that this antigen is located on the sporozoite. It is suggested that this antigen could be a good candidate for studies of mucosal immune response to C. parvum and for vaccination.