Date of Graduation

12-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor/Mentor

Kwon, Young

Committee Member

Hargis, Billy

Second Committee Member

Erf, Gisela

Third Committee Member

Sun, Xiaolun

Keywords

Broiler; Immune response; Leghorn; Poultry; Salmonella; Vaccine

Abstract

Here, a comprehensive understanding of immune responses triggered by either a multimeric CD40 receptor-agonistic DNA aptamer-based or mannosylated chitosan-based Salmonella Enteritidis inactivated vaccine platforms, along with phytobiotic supplementation as an immune modulatory strategy in response to Salmonella lipopolysaccharides, is presented. This dissertation supports the development of next-generation Salmonella vaccine platforms that simultaneously stimulate both protective cell-mediated and humoral immune responses, while indicating the potential immunomodulatory effects of phytobiotics supplementation to reduce the immunological impact of Salmonella lipopolysaccharides in chickens. The first chapter describes that both vaccine platforms administered in broiler chickens initiated local inflammatory responses, recruiting heterophils and macrophages from the blood. The DNA aptamer-based vaccine platform triggered the local infiltration of high numbers of B and T cells after boost immunization, and high levels of mucosal IgA. Meanwhile, the mannosylated chitosan-based vaccine platform polarized the humoral response towards IgY (see Chapter 1). The results found in Chapter 2, where primary and boost doses of each Salmonella inactivated vaccine platform were subcutaneously administered to Light-brown Leghorn hens, showed systemic compartmentalization of humoral responses triggered by the mannosylated chitosan-based vaccine platform. The elevated IgY levels were shown to be transferred into the eggs (yolk) 18 weeks after boost immunization, implying a long-lasting and passively transferable immunity. Instead, the DNA aptamer vaccine platform compartmentalized the humoral response towards the production of mucosal IgA. In Chapter 3, intradermal injections of Salmonella LPS were administered to chickens reared under cyclic heat stress or thermoneutral conditions and supplemented with different phytobiotics. This study suggested that HS is not capable of preventing the establishment of acute local inflammatory responses by LPS; however, it alters the chicken antioxidant status. Chapter 3 revealed phytobiotic’s capability to modulate the acute inflammatory response under the experimental conditions. Overall, the results presented in this dissertation provide a comprehensive understanding of the acute inflammatory, cellular, and humoral immune responses triggered by two experimental Salmonella inactivated vaccine platforms, providing novel insights into the characteristic immune response derived from their administration. In addition, novel insights into the characteristics of acute inflammatory responses to LPS under different environmental conditions and the potential immunomodulatory effect of phytobiotics supplemented in the feed are shared.

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