Identification of Cryptosporidium parvum oocyst/sporozoite antigens recognized by infected and hyperimmune lambs.

The appearance, persistence and eventual decline of IgG, IgM and IgA antibodies recognizing Cryptosporidium parvum antigens were studied in naturally infected lambs using a Western blot technique, and the results compared with those obtained using sera from immunized lambs. There was an intense recognition of some low molecular weight proteins (15-17 kDa by IgG and IgA; 28-30 kDa by IgA, IgM and IgG) during the infection and early post-infection period. These peptides were not recognized after Days 45-60 of life. Some high molecular weight antigens (94 kDa) were weakly recognized on Day 15 but more intensely recognized from Day 30 onwards, persisting until at least Day 90. Antibody recognition of these C. parvum proteins could be an indicator of recent or past exposure to the parasite.