phoP, SPI1, SPI2 and aroA mutants of Salmonella Enteritidis induce a different immune response in chickens

Veterinary Research, Sep 2015

Poultry is the most frequent reservoir of non-typhoid Salmonella enterica for humans. Understanding the interactions between chickens and S. enterica is therefore important for vaccine design and subsequent decrease in the incidence of human salmonellosis. In this study we therefore characterized the interactions between chickens and phoP, aroA, SPI1 and SPI2 mutants of S. Enteritidis. First we tested the response of HD11 chicken macrophage-like cell line to S. Enteritidis infection monitoring the transcription of 36 genes related to immune response. All the mutants and the wild type strain induced inflammatory signaling in the HD11 cell line though the response to SPI1 mutant infection was different from the rest of the mutants. When newly hatched chickens were inoculated, the phoP as well as the SPI1 mutant did not induce an expression of any of the tested genes in the cecum. Despite this, such chickens were protected against challenge with wild-type S. Enteritidis. On the other hand, inoculation of chickens with the aroA or SPI2 mutant induced expression of 27 and 18 genes, respectively, including genes encoding immunoglobulins. Challenge of chickens inoculated with these two mutants resulted in repeated induction of 11 and 13 tested genes, respectively, including the genes encoding immunoglobulins. In conclusion, SPI1 and phoP mutants induced protective immunity without inducing an inflammatory response and antibody production. Inoculation of chickens with the SPI2 and aroA mutants also led to protective immunity but was associated with inflammation and antibody production. The differences in interaction between the mutants and chicken host can be used for a more detailed understanding of the chicken immune system.

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phoP, SPI1, SPI2 and aroA mutants of Salmonella Enteritidis induce a different immune response in chickens

Elsheimer-Matulova et al. Veterinary Research phoP, SPI1, SPI2 and aroA mutants of Salmonella Enteritidis induce a different immune response in chickens Marta Elsheimer-Matulova 0 Karolina Varmuzova 0 Kamila Kyrova 0 Hana Havlickova 0 Frantisek Sisak 0 Masudur Rahman 0 Ivan Rychlik 0 0 Veterinary Research Institute , Hudcova 70, 621 00, Brno , Czech Republic Poultry is the most frequent reservoir of non-typhoid Salmonella enterica for humans. Understanding the interactions between chickens and S. enterica is therefore important for vaccine design and subsequent decrease in the incidence of human salmonellosis. In this study we therefore characterized the interactions between chickens and phoP, aroA, SPI1 and SPI2 mutants of S. Enteritidis. First we tested the response of HD11 chicken macrophage-like cell line to S. Enteritidis infection monitoring the transcription of 36 genes related to immune response. All the mutants and the wild type strain induced inflammatory signaling in the HD11 cell line though the response to SPI1 mutant infection was different from the rest of the mutants. When newly hatched chickens were inoculated, the phoP as well as the SPI1 mutant did not induce an expression of any of the tested genes in the cecum. Despite this, such chickens were protected against challenge with wild-type S. Enteritidis. On the other hand, inoculation of chickens with the aroA or SPI2 mutant induced expression of 27 and 18 genes, respectively, including genes encoding immunoglobulins. Challenge of chickens inoculated with these two mutants resulted in repeated induction of 11 and 13 tested genes, respectively, including the genes encoding immunoglobulins. In conclusion, SPI1 and phoP mutants induced protective immunity without inducing an inflammatory response and antibody production. Inoculation of chickens with the SPI2 and aroA mutants also led to protective immunity but was associated with inflammation and antibody production. The differences in interaction between the mutants and chicken host can be used for a more detailed understanding of the chicken immune system. - Introduction Non-typhoid Salmonella enterica serovars are among the most common causative agents of food-borne diseases worldwide [1]. Since poultry is the most frequent reservoir of salmonellosis for humans, vaccination of chickens is understood as an effective measure to decrease S. enterica incidence in humans. Currently, construction of attenuated vaccine strains of S. enterica is not an issue and many different mutants have been tested in mice, chickens and even humans [2-7]. However, the main dilemma is which mode of attenuation to choose out of the many possibilities [8]. More detailed information on host response to S. enterica infection or vaccination is therefore needed. Such information can be obtained either by generating chickens with knocked out genes involved in innate or acquired immune response or by preparing S. enterica mutants with clearly defined defects in pathogenesis and analysis of chicken immune response. Since the former possibility is still an issue in chickens, the latter approach represents a feasible alternative. Mutants with clearly different defects in Salmonella pathogenesis include those with deletions in aroA, phoP, SPI1 or SPI2. Reduced virulence of aroA mutants can be explained by their inability to produce aromatic compounds as well as having a high sensitivity to serum [2,9]. phoP mutants belong to the most attenuated ones as they fail to survive inside phagocytic cells [10], perhaps due to their high sensitivity to acidification and host antimicrobial peptides [11]. However, phoP mutants also exhibit intracellular overgrowth in fibroblasts [12]. Recently, mutants defective in virulence genes specific to © 2015 Elsheimer-Matulova et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. S. enterica such as those localized on the Salmonella pathogenicity island (SPI) 1 and SPI2 have been successfully tested [5,13]. SPI1 mutants are impaired in invading non-professional phagocytes while SPI2 mutants are unable to survive intracellularly for a prolonged time [14-17]. SPI1 mutants are also defective in induction of apoptosis in macrophages [18,19]. Interestingly, when we recently used SPI1 and SPI2 mutants of S. enterica serovar Enteritidis for vaccination of chickens, higher antibody levels were observed in chickens vaccinated with the SPI2 mutant than in chickens vac (...truncated)


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Marta Elsheimer-Matulova, Karolina Varmuzova, Kamila Kyrova, Hana Havlickova, Frantisek Sisak, Masudur Rahman, Ivan Rychlik. phoP, SPI1, SPI2 and aroA mutants of Salmonella Enteritidis induce a different immune response in chickens, Veterinary Research, 2015, pp. 96, 46, DOI: 10.1186/s13567-015-0224-x