Protective immunization against the intestinal parasite Eimeria acervulina with recombinant coccidial antigen.

The gene encoding an immunodominant Eimeria acervulina merozoite surface antigen (EAMZ250) was expressed in bacteria as a fusion peptide with the galactose-binding protein (GBP) of Escherichia coli. Recombinant and control antigens were administered to 1-wk-old chickens by peroral inoculation with live nonpathogenic bacteria that were expressing GBP-EAMZ250 or GBP protein. The immunization elicited antigen-specific humoral and cellular immune responses as measured by ELISA and T-cell blastogenesis assay. In addition, chickens immunized with recombinant GBP-EAMZ250 exhibited significant protection against weight loss and intestinal lesions after E. acervulina challenge. Bacterial transformants were recoverable from the upper and middle intestine of inoculated chickens for various times after immunization. These data indicate that oral administration of live E. coli expressing a recombinant E. acervulina antigen is an effective means of inducing resistance to coccidiosis.