Location: Egg and Poultry Production Safety Research Unit
Project Number: 6040-32420-003-004-N
Project Type: Non-Funded Cooperative Agreement
Start Date: Aug 10, 2020
End Date: Aug 9, 2023
The central aim of this project is to improve the effectiveness of vaccinations for Salmonella Typhimurium in poultry by increasing the antigenicity of live, attenuated aroA mutant vaccine preparations. Increased antigenicity will affect the gut microbiota and stimulate a stronger host immune response, improving vaccine efficacy and the duration of protection against S. Typhimurium in poultry. This will ultimately reduce bacterial loads in the farm environment, mitigate downstream contamination of the food supply chain, and reduce the number of human salmonellosis cases. ARS PI will consult on experimental design, data interpretation, and manuscript preparation to achieve this objective in research conducted at the University of Adelaide.
These experiments will apply previously developed knowledge that a live, attenuated aroA mutant Salmonella Typhimurium (ST) vaccine, which has high expression of genes involved in host colonization and virulence, induces strong cell mediated and intestinal mucosal immune responses. The manufacturer of this vaccine currently recommends administering it to egg-laying chickens in three separate doses: the first dose is reconstituted in distilled water and administered by coarse spray to day-old chicks at the hatchery or when first arriving at the farm, the second dose is administered via drinking water at 4-6 weeks of age, and the final dose is reconstituted in a proprietary aqueous diluent and injected intra-muscularly into the pectoralis muscle at 10 weeks of age. Broiler chickens typically receive only a single dose applied by coarse spray to day old chicks (sometimes followed by a second dose in the drinking water at 2 weeks of age). The proposed project aims to generate a more persistent immune response, protective against repeated challenge with wild-type ST and other salmonellae over the productive lifespan of both layers and broilers. Three sets of experiments will be conducted to achieve this objective. The first set of studies aim to increase the antigenicity of the ST vaccine strain by determining the expression of relevant immunogenic virulence genes under different vaccine reconstitution conditions and then assessing host immune response to the vaccine under each of these conditions. The second set of experiments will investigate the threshold levels of wild-type ST required to establish infection in a bird and the correlated ability of ST vaccine, reconstituted by different methods and administered by different routes, to effectively reduce infection. The third set of studies will determine whether multiple doses of the experimental vaccine enhance immunity in a cost-effective manner over the extended productive lifespan of laying hens. All research will be conducted entirely by cooperator. No research activities will be performed by ARS. Role of ARS PI will be to consult on experimental design data interpretation, and manuscript preparation in regard to research conducted by the cooperator.