Development and Evaluation of Two Live Salmonella -Vectored Vaccines for Campylobacter Control in Broiler Chickens

is the leading bacterial cause of human enteritis in developed countries. Human campylobacteriosis is commonly associated with the consumption of undercooked, contaminated chicken, a natural host of . Thus, the control of colonization in poultry at the farm level would reduce the risk of human exposure to this pathogen. Vaccination is an attractive intervention measure to mitigate in poultry. Our recent studies have demonstrated that the outer-membrane proteins CmeC (an essential component of CmeABC multidrug efflux pump) and CfrA (ferric enterobactin receptor) are feasible candidates for immune intervention against . By targeting these two promising vaccine candidates, live attenuated -vectored vaccines were developed and evaluated in this study. Briefly, the and genes were cloned into expression vector pYA3493 and transferred into serovar Typhimurium χ8914, the USDA licensed live attenuated vaccine strain. The oral live vaccines producing CfrA or CmeC (truncated or full length) were successfully constructed by using delicate molecular manipulation despite the challenge due to the potential toxic effect of the cloned gene product in the host. Expression and membrane localization of the target protein in the vaccines were confirmed by immunoblotting. The efficacies of the two live vaccines that produce full-length CfrA or CmeC were evaluated by using broiler chickens. However, oral vaccination of chickens failed to trigger significant systemic and intestinal mucosal immune responses and, consequently, did not confer protection against colonization chickens. The vaccination regimens of the constructed live -vectored vaccine need to be optimized in future studies.