Immune responses of chickens against recombinant Salmonella enterica serotype Heidelberg FimA and FimW fimbriae and FliD and FlgK flagellar proteins

Abstract

Implementation of a vaccination program is one of the most effective means to control infectious diseases during food animal production. Salmonella, a Gram-negative bacterium, is a leading bacterial cause of human foodborne illnesses worldwide. The major source of this microorganism for human infection is from consumption of unsanitary poultry products. Although live attenuated vaccines are available, these vaccines suffer from problems including persistence and shedding of Salmonella in and from the vaccinated animals. To overcome these problems, the recombinant Salmonella enterica serotype Heidelberg FliD, FlgK, FimA and FimW subunit proteins that are surface-exposed were produced and tested for their immunogenicity in chickens in this study. As expected, there were no detrimental signs observed in chickens after vaccination during the six-week experimental period. These four proteins migrated in a single band to their respective positions. Analysis of immune responses to the proteins reveals that the immunoglobulin (Ig) G, IgM and IgA from most vaccinated chickens reacted strongly to the recombinant FliD and FlgK proteins, but not from unvaccinated chickens. On the other hand, IgG, IgM and IgA antibody responses to FimA and FimW from the vaccinated group were no difference from those from unvaccinated chickens, suggesting that the FimA and FimW proteins may be not good antigens, potentially due to their size, composition, and/or structural complexity. In addition, IgG could be induced by FliD and FlgK after a single vaccination. These antibody studies suggest that recombinant FliD and FlgK have potential as targets for vaccine development. Because of the importance of bacterial fimbriae in pathogenesis and for immunogenicity, a chimeric protein of the FimA and FimW proteins is needed.