Assessment of chicken protection against Campylobacter jejuni infection by immunization with avirulent Salmonella enterica sv. Typhimurium strain producing Campylobacter CjaD/Pal protein

Abstract

Campylobacter jejuni is a major food-borne pathogen, causing gastroenteritis worldwide. Chickens are considered to be one of the most common sources of human C. jejuni infection in developed countries. Campylobacter CjaD/Pal protein (annotated as Cj0113 in C. jejuni strain NCTC11168) is a highly immunogenic, membrane-located antigen, conserved among different strains, with the potential to provide broad protection against C. jejuni colonization. The present study examines the immunogenicity and the general efficacy of avirulent S. enterica sv. Typhimurium ∆crp ∆cya expressing C. jejuni CjaD as a chicken vaccine against Campylobacter colonization. The high copy number plasmid pYA3341 Asd+ was used as a cloning vector. Here, 1- and 14-day old chickens were orally immunized with a delivery vector strain, expressing C. jejuni CjaD. Two weeks later, they were challenged with a wild-type C. jejuni strain isolated from chicken carcasses. This schedule of immunization induced sig- nificant levels of serum-specific IgG as well as mucosal intestinal sIgA as measured by ELISA tests using Campylobacter membrane proteins as a coating antigen. Nevertheless, protection experiments did not result in significant reduction of colonization of vaccinated birds relative to nonvaccinated birds.