Title : Protective efficacy of a novel trivalent inactivated Salmonella vaccine against Salmonella Infantis in Hy-Line Brown chickens
Abstract:
The protective efficacy of a novel trivalent inactivated Salmonella bacterial vaccine against Salmonella Infantis infection was evaluated in Hy-Line Brown layers. Forty layers were randomly divided into three groups (A to C), with Group B mock-vaccinated with sterile PBS (IM) and Group C subcutaneously primed with SG9R followed by an IM boost with the trivalent inactivated vaccine. To assess immune response, splenocytes collected from five hens sacrificed from Groups A and C three weeks post-boost were restimulated with S. Enteritidis, S. Typhimurium, or S. Gallinarum extracts for real-time PCR analysis of cytokine expression. Subsequently, all remaining hens in Groups B and C were orally challenged with 5×10? CFU of virulent wild-type S. Infantis. Results showed that serum IgG titers and IFN-γ expression in Group C were significantly higher than those in Group A. All birds survived the challenge without clinical symptoms. While S. Infantis was not recovered from the liver, spleen, cecum, and cloaca in Group A, the challenge strain was isolated from 20% of Group C birds' livers and spleens and 40% of their ceca, and cloacae, compared to 100% colonization across all organs in the control Group B. These findings indicate that the priming and boosting regimen with the HJP34-inactivated S. Enteritidis whole bacterial cells is an effective strategy to protect Hy-Line Brown chickens against S. Infantis infection by successfully inducing robust humoral and cellular immune responses and significantly reducing bacterial colonization.
