Gene expression of chicken cells influenced by plasmidless non-motile mutants of Salmonella Enteritidis

Szmolka, Ama and Matulova, Marta and Imre, Ariel and Wiener, Zoltán and Rychlik, Ivan and Nagy, Béla (2014) Gene expression of chicken cells influenced by plasmidless non-motile mutants of Salmonella Enteritidis. In: A Magyar Mikrobiológiai Társaság 2014. évi Nagygyűlése és EU FP7 PROMISE Regional Meeting, 2014. október 15-17., Keszthely.

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Abstract

Salmonella Enteritidis is still a significant pathogen of human gastroenteritis, originating mainly from poultry (ECDC/EFSA supporting publication 2014). Recently we have shown that chicken embryo fibroblast cells (CEFs) proved to be useful for in vitro assessment of the innate immune response of chicks to S. Enteritidis infection. Therefore we intended to use CEFs to estimate and the significance of certain virulence determinants of S. Enteritidis in chicken. Our objective was to characterize the gene expression profiles of CEFs as a response to non-motile mutants of S. Enteritidis 11 (SE 11) lacking the serovar-specific virulence plasmid and/or the fliD gene in comparison to the wild type parental strain. Freshly isolated CEFs incubated with Salmonella for 4 hrs were used to measure the invasiveness of parental strain SE 11 and its virulence-defective mutants (Imre et al., 2011). We used Agilent custom 8×15K microarray to profile the expression of CEFs, with emphasis to genes related to the immune response. Expression of chicken genes identified as significantly up- or downregulated (≥3-fold) was verified by real-time PCR. Invasiveness of both mutants of SE11 proved to be significantly lower than that of parental strain. Infection with SE 11 induced 26 genes and led to the suppression of 39 genes. Out of them the colony-stimulating factor gene CSF3 and cytokine genes for IL-1β and IL-8 showed the highest upregulations. In contrast, infection with non-motile mutants lacking the virulence plasmid and/or fliD did not cause any significant change in host gene expression. However real-time PCR results indicated that the cell cycle G0S2 switch gene (cell division), and the enolase ENO2 gene (metabolism) were highly induced by the mutant strains, indicating that the reduced invasiveness of the mutants was concomitant to stimulated cell division and/or metabolism of the host cells. Based on these results fliD seems to be more important for the invasiveness of Salmonella Enteritidis than the serovar-specific virulence plasmid. This is in harmony with our earlier in vivo studies about minor significance of the virulence plasmid in the pathogenicity of S. Enteritidis 11. In contrast, fliD could be considered as a modulator of the chicken response to Salmonella infection. Interestingly stimulation of non-immune genes such as G0S2 and ENO2 was much stronger by the virulence-defective mutants demonstrating that plasmid- and/or flagellin of Salmonella may influence host cell metabolism and regeneration. This work was supported by the EU FP6 NoE MedVetNet and FP7 PROMISE. Ama Szmolka is a holder of János Bolyai Research Scholarship of Hungarian Academy of Sciences. A. Imre’s present address is: CEVA—Phylaxia, Szállás u.5, H-1107 Budapest, Hungary.

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