A genetic hybrid of the Campylobacter jejuni flaA gene with LT-B of Escherichia coli and assessment of the efficacy of the hybrid protein as an oral chicken vaccine.

The objectives of this study were to produce Campylobacter jejuni flagellin fused to the B-subunit of the labile toxin (LT-B) of Escherichia coli and to assess the efficacy of the hybrid protein as a chicken vaccine. Part of the flaA gene (780 base pairs) was cloned in plasmid pBEB downstream and in frame with the LT-B to allow expression of a hybrid protein. Transformed E. coli chi 6097 expressed the hybrid protein (43 kdaltons) in inclusion bodies at mid log phase. The inclusion bodies were isolated, and the identity of the protein was verified by western blot. This hybrid protein was administered as a vaccine to chickens either orally (0, 250, 500, or 1000 micrograms total protein) or intramuscularly (250 or 1000 micrograms). Alimentary secretions were collected, and specific antibodies were assayed by western blot analyses. Seventy-two percent of the birds vaccinated orally with 1000 micrograms protein showed detectable antibodies against C. jejuni flagellin in the excreta. None of the control birds produced detectable antibody to this antigen. For trials to demonstrate clearance of Campylobacter, groups of chickens were vaccinated with the hybrid protein at 2 and 4 wk of age and challenged at 3 wk with an excess of C.jejuni. The number of birds that remained colonized at 5 wk of age was significantly lower among the vaccinated birds than among controls.