Files
Abstract
Salmonella is a foodborne pathogen that is prevalent in chickens. Chickens are the second most consumed meat worldwide. As the world population increases, the demand for chicken meat is expected to rise. For this reason, there is a need for effective Salmonella control strategies in the poultry industry. Vaccines have been an effective tool for Salmonella control in poultry. However, there are currently no commercially available oral-killed Salmonella vaccines for chickens. Currently, chitosan nanoparticles are being studied as vaccine carriers for the oral delivery of antigens. This research evaluated the protective effects of a Salmonella chitosan nanoparticle (CNP) vaccine on broilers using in-ovo vaccination, gel-spray vaccination, and a combined live vaccine followed by a killed CNP booster vaccination. In-vitro results demonstrated that the CNP vaccine is stable in acidic conditions and is biocompatible with chickens. Findings demonstrate that the in-ovo, gel-spray, and live followed by CNP vaccine delivery can elicit substantial antigen-specific IgY levels in serum and IgA levels in bile (P<0.05). At d14- and d21-of-age, the in-ovo delivery of the CNP vaccine decreased the Salmonella Enteritidis (S. Enteritidis) load by 0.62 and 0.85 Log10 CFU/g, compared to control (P<0.05). At d21-of-age, the live vaccine followed by a killed CNP vaccine booster vaccination elicited antigen-specific T-lymphocyte proliferation at 0.02 mg/mL OMPs stimulation, compared to control (P<0.05). At d28-of-age, the CNP vaccine and the live vaccine followed by a killed CNP vaccine booster decreased the cecal S. Enteritidis load by 0.9 Log10 CFU/g and 1 Log10 CFU/g, respectively (P<0.05), compared to control. Further, the CNP gel-spray vaccination induced a significant antigen-specific lymphocyte proliferation against S. Enteritidis flagellin antigens, S. Typhimurium heat-killed-antigens (HKA), and S. Litchfield HKA (P<0.05), compared to control. The gel-spray vaccination of CNP vaccine also reversed the loss in gut permeability by 13% (P<0.05). Further, at d21-post-infection, the gel-spray vaccination of CNP vaccine significantly lessened the cecal and spleen S. Enteritidis load by 2 Log CFU/g and the intestinal load by 0.6 Log10 CFU/g, compared to control (P<0.05). We conclude that the CNP vaccine is an alternative vaccine candidate against Salmonella in poultry.