The objective in vaccinating chickens against Campylobacter is to reduce intestinal colonization and contamination of chicken meat products. Existing experimental vaccines are not able to induce a sufficiently strong immune response, and provide no or little of protection against Campylobacter colonization. There is no commercially available vaccine against Campylobacter for chickens despite many attempts to develop one.
A collaborative project between the laboratories of Prof. Shayan Sharif and Prof. Mario Monterio from the University of Guelph was initiated to try to develop an effective vaccine against Campylobacter in chickens. A prototype vaccine consisting of capsular carbohydrates of C. jejuni conjugated with a carrier (CPSconj) developed by Prof. Monterio, formed the basis of the vaccine development in the current study. Prof. Mopnterios’ CPSconj carrier has previously shown efficacy in a primate model. The efficacy of vaccination for reducing C. jejuni colonization of chicken intestinal tissues was assessed. Three administered doses of the prepared CPSconj vaccine resulted in a detectable antibody response in 75 per cent of specific pathogen free birds. Whereas vaccination of commercial broiler chicks resulted in a detectable antibody response in 33 per cent of orally challenged birds. Overall, the in vivo findings show CPSconj vaccinated birds had significantly lower numbers of C. jejuni in intestinal tissue when compared to non-vaccinated birds.
The study went on to identify an immune response enhancer which is termed an “adjuvant”, with the specific capacity to induce immune responses in cells of the chicken intestine for inclusion in the prototype vaccine or as a stand-alone prophylactic compound. In vitro studies demonstrated that adjuvant CpG-ODN elicited the highest activation of cell signaling molecules prevalent in immune responses and was therefore selected as the optimum mucosal vaccine adjuvant. To target the selected adjuvant to the intestine of chickens and ensure slow release of the adjuvant at the site of infection, a delivery system based on encapsulating the adjuvant into specific nanoparticles was employed. Results demonstrated that CpG-ODN administration reduced bacterial burden in the intestine and encapsulation of the CpG-ODN resulted in a greater decrease of bacterial burden in the chicken intestine.
Overall, Dr. Sharif and his research team have demonstrated that it is possible to employ a subunit vaccine for reducing Campylobacter jejuni in chickens. Additionally, the research team has provided evidence for CpG-ODN as a stand-alone anti-bacterial prophylactic strategy. Dr. Sharif and his research team will continue to explore better ways for control of Campylobacter jejuni through the use of vaccines, immune stimulants and probiotics.