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Development Of Campylobacter jejuni Proteins As In Ovo Vaccines For Broiler Chickens

By Hung-Yueh Yeh, Kelli L. Hiett, J. Eric Line and Bruce S. Seal

Campylobacter jejuni, commonly associated with poultry, causes human campylobacteriosis. Although many strategies for reducing C. jejuni contamination in poultry have been examined, there are currently no practical intervention means available for the poultry industry to effectively reduce the contamination of C. jejuni during production and processing. Therefore, research for practical on-farm interventions is an urgent need.  In this proposal, we attacked this problem by development of C. jejuni subunit proteins as potential vaccines for broilers.

The hypothesis of the proposed study was that expression of a battery of C. jejuni proteins involved in colonization has the potential for discovery of novel antigen(s) that can be used for in ovo vaccination to reduce the bacterium in broiler chicken gastrointestinal systems. The specific objectives of this proposal are to (1) construct a system for expressing large amounts of important C. jejuni proteins, (2) produce and purify the recombinant C. jejuni proteins, (3) assay the immune response in broiler chickens against these C. jejuni proteins, and (4) conduct vaccination experiments with the C. jejuni proteins.

Objective 1: Fifty-seven C. jejuni genes potentially involved in colonization were identified. Twenty-eight genes were successfully over-expressed to allow purification of proteins. Objective 2: The proteins were purified using chromatography. Objective 3: Two recombinant proteins --flagellar capping protein (FliD) and methyl-accepting chemotaxis protein (Cjj0473) reacted strongly to sera from broilers older than six weeks of age in our preliminary experiments, indicating that these were antigens which the broiler immune system was exposed to and responding to in the field. Next, we evaluated whether sera collected from other areas in the U.S. contained antibodies against the FliD protein. Sera from layer breeders at 44-52 weeks of age showed 100% positive, while sera from broilers at 4-6 weeks of age from 22 premises showed 7-100% positives.

These results suggest that C. jejuni was widespread in these poultry populations, and chickens had been exposed to this microorganism. It appears that prevalence of C. jejuni in these poultry populations was age-related.  Objective 4: Three in ovo experiments were conducted. The results showed very poor hatchability, suggesting that the adjuvant used was toxic to chicken embryos. Next, one-day-old maternal antibody-positive broiler chickens were vaccinated with 100 mg/chicken of the FliD protein prepared with an equal amount of incomplete Freund's adjuvant. The broiler chicks responded by producing antibody to the protein. These results suggest that the FliD protein is immunogenic in broilers and that this protein has potential as a vaccine candidate. The results also indicate that maternal antibodies may not affect immunization.

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