Induction of Mucosal Humoral Immunity by Subcutaneous Injection of an Oil-emulsion Vaccine against Salmonella enterica subsp. enterica serovar Enteritidis in Chickens

Abstract

Salmonella enterica subsp. enterica serovar Enteritidis (SE) is one of the major causes of food poisoning. Much effort has been made to develop a vaccine for the prevention of SE colonization and infection in poultry. However, the effect of inactivated whole-cell SE vaccines on the bacterial attachment has not been clarified. This study investigated the immune responses to a killed whole-cell SE vaccine in chickens and the effect of vaccination on the bacterial attachment of SE to cultured Vero cells. A 1 ml dose of 10⁸–10⁹ CFU viable SE bacterial cells was orally administered to chickens at 4 weeks or 10 months post vaccination. The number (CFU) of SE in 1 g of cecal droppings was counted on day 6 after administration. The SE CFUs were significantly lower (p < 0.05) in the vaccinated chickens, not only at 4 weeks but also at 10 months after vaccination, than in the unvaccinated control chickens. Anti-SE IgG and anti-SE IgA were detected using enzyme-linked immunosorbent assay (ELISA) in serum and intestinal and oviduct fluid samples from vaccinated chickens. Adhesion of heat-killed SE cells to Vero cells was reduced by pre-treatment of the bacteria by the vaccinated chicken-derived intestinal fluid, indicating the potential of the vaccine-induced antibody to prevent SE adhesion to epithelial cell surfaces.