Immunological and pathobiological characteristics of a novel liveTyphimurium-vectoredvaccine candidate for layer chickens.

Abstract

INTRODUCTION: Spotty liver disease (SLD) poses a significant economic and animal welfare threat to the global cage-free egg industry, primarily due to infection by the emerging pathogen. SLD can lead to a significant decline in egg production and increased mortality rates. Antibiotics remain the most effective measure for controlling the disease. However, the rise of antibiotic resistance is a growing global concern for public health, promoting efforts to reduce antibiotic usage in animal production. Poultry vaccination offers an alternative approach to decreasinglevels. Although autogenous vaccines are in use in some countries with limited efficacy, no vaccine is currently licensed for widespread use. METHODS: This study developed and characterized a liveTyphimurium vector strain designed to deliver the conserved-glycan heptasaccharide as a target antigen against. RESULTS: The replacement of theTyphimuriumgene with thelocus attenuated the vaccine strain, allowing the conjugation of the heptasaccharide toTyphimurium endogenous lipopolysaccharide (LPS). Commercial layer hens vaccinated with theTyphimurium strain producing theheptasaccharide induced significantly higher IgY antibody titres specific to theheptasaccharide compared to the birds vaccinated with the vector strain not expressing the heptasaccharide. Modification of theTyphimurium endogenous LPS with the heptasaccharide had no significant impact on IgY antibody responses againstTyphimurium. DISCUSSION: This study provides evidence that usingTyphimurium to deliverheptasaccharide is a feasible approach to providing bi-valent immunogenicity against bothTyphimurium and.