Obtaining hyperimmune anti-Cryptosporidium parvum ovine colostrum. A study of the humoral immune response in immunized sheep.

Three ewes were immunized five times over a 2-month period prior to giving birth by intramuscular injection, oral administration and intramammary infusion of antigen and viable or freeze-dried Cryptosporidium parvum oocyst solution emulsified with Freund's complete and incomplete adjuvant. Two animals served as controls and another two as adjuvant controls. Serum was collected at first immunization and thereafter every 2 to 4 weeks. Colostrum and milk were collected as well. All samples were assayed for C. parvum-specific antibodies using an enzyme-linked immunosorbent assay methodology, and Western blotting was used to recognize the C. parvum antigens. Hyperimmunization resulted in a progressive and significant increase in specific anti-C. parvum serum IgG, IgA and IgM titres, with the highest values noted at the point of lambing. Titres decreased slightly in milk, although they were in all cases higher than those in the control animals. Moreover, some 30 bands of C. parvum were recognized.