Immunological and pathobiological characteristics of a novel live Typhimurium-vectored vaccine candidate for layer chickens.

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 decreasing levels. 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 live Typhimurium vector strain designed to deliver the conserved -glycan heptasaccharide as a target antigen against .

RESULTS

The replacement of the Typhimurium gene with the locus attenuated the vaccine strain, allowing the conjugation of the heptasaccharide to Typhimurium endogenous lipopolysaccharide (LPS). Commercial layer hens vaccinated with the Typhimurium strain producing the heptasaccharide induced significantly higher IgY antibody titres specific to the heptasaccharide compared to the birds vaccinated with the vector strain not expressing the heptasaccharide. Modification of the Typhimurium endogenous LPS with the heptasaccharide had no significant impact on IgY antibody responses against Typhimurium.

DISCUSSION

This study provides evidence that using Typhimurium to deliver heptasaccharide is a feasible approach to providing bi-valent immunogenicity against both Typhimurium and .