Hyperimmune bovine colostrum specific for recombinant Cryptosporidium parvum antigen confers partial protection against cryptosporidiosis in immunosuppressed adult mice

Preparturient cows were immunized three times over a six-week period with r ecombinant plasmid DNA encoding the Cryptosporidium parvum CP15/60 antigen by injecting the DNA in the mammary gland. Serum was collected at each immu nization and first colostrum was collected after parturition; all were assa yed for Cryptosporidium-specific antibodies (Ab). A serological response to C. parvum sporozoite and oocyst antigen was detected in cows immunized wit h pCP15/60 plasmid DNA. Colostrum from these cows, unlike colostrum from no rmal controls, contained Ab specific for C. parvum sporozoites and oocysts as indicated by immunofluorescence Ab (IFA) staining. Colostrum was also te sted for conferring passive immunity against C. parvum infection by oral ad ministration to immunosuppressed adult inbred mice. Immune colostrum and co ntrol colostrum were administered to separate groups of dexamethasone (DEX) -treated adult C57BL/6NCr mice beginning 12 h before and at 12 h intervals for 3 days after oral C. parvum oocyst infection. Cryptosporidium developme nt was assayed in ilea of immune- and control-colostrum-treated mice 96 h p ostinfection by semiquantitative PCR. Mice receiving immune colostrum showe d partial protection (about 50% reduction) against intestinal C. parvum dev elopment compared to mice receiving control colostrum. This protection was evident at a challenge dose of 10(3) C. parvum oocysts per mouse; no differ ences were noted in parasite development between groups receiving immune or control colostrum and infected with 10(4) oocysts. This study showed that serum and colostrum Ab response to C. parvum can be elicited in preparturie nt cows by direct injection of recombinant pCP15/60 plasmid DNA and that pa ssive protection against cryptosporidiosis can be obtained by treating immu nosuppressed mice with immune colostrum before and after C. parvum infectio n. (C) 1999 Elsevier Science Ltd. All rights reserved.