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

Authors: Yeh, Hung Yueh; Read, Quentin

Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2024
Publication Date: 12/30/2024
Citation: Yeh, H., Read, Q.D. 2024. Immune responses of chickens against recombinant Salmonella enterica serotype Heidelberg FimA and FimW fimbriae and FliD and FlgK flagellar proteins. Veterinary Immunology and Immunopathology. 280:2025(e110870). https://doi.org/10.1016/j.vetimm.2024.110870.
DOI: https://doi.org/10.1016/j.vetimm.2024.110870

Interpretive Summary: Salmonella is the leading bacterial cause of human foodborne illnesses worldwide. The major source of this microorganism for human infection is from consumption of unsanitary poultry products. Implementation of a vaccination program is one of the most effective means to control infectious diseases during production. Although lived attenuated vaccine are available, there are problems of these vaccines, such as persistence and shedding of Salmonella in and from the vaccinated animals. In this study, the recombinant Salmonella enterica serotype Heidelberg two flagellar and two fimbrial proteins that are surface-exposed were produced and tested for their antigenicity in chickens. The recombinant flagellar proteins triggered high levels of immune responses in vaccinated birds, but not the unvaccinated group, indicating the antigenicity of the recombinant proteins. On the other hand, the recombinant fimbrial proteins barely induced antibody responses in vaccinated chickens. The reasons are not clear, but it may be due to factors, such as size, compositions and/or structural complexity of the proteins. 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, a chimeric protein of the FimA and FimW proteins is needed.

Technical Abstract: Implementation of a vaccination program is considered as one of the most effective means to control infectious diseases during food animal production. Salmonella, a Gram-negative bacterium, is the 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 lived attenuated vaccine are available, there are problems of these vaccines, such as persistence and shedding of Salmonella in and from the vaccinated animals. In this study, the recombinant Salmonella enterica serotype Heidelberg FliD, FlgK, FimA and FimW proteins that are surface-exposed were produced and tested for their immunogenicity in chickens. The genes of encoding four proteins were amplified by PCR, ligated and transformed into an Escherichia coli expression system. The expressed proteins were purified by affinity chromatography using nickel-chelating resins. Chickens were vaccinated subcutaneously with four recombinant proteins emulsified in Freund’s incomplete adjuvant. Sera were collected for immunoblotting assays at appropriate times. Immunoblotting assays were carried out with an automated capillary immunoblotting instrument according to the manufacturer’s instructions. The software associated with the instrument was used for data analysis. Bayesian generalized linear mixed models to the immune response data were used. 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 immunized chickens reacted strongly to the recombinant FliD and FlgK proteins, but not from un-immunized chickens. On the other hand, IgG, IgM and IgA antibody responses to FimA and FimW from the immunized group were no different from those from un-immunized chickens, suggesting that the FimA and FimW proteins are not good antigens due to many factors, such as the size, the compositions and/or structural complexity. 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.