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Influence of PhoP and intra-species variations on virulence of Yersinia pseudotuberculosis during the natural oral infection route.

Pisano F, Heine W, Rosenheinrich M, Schweer J, Nuss AM, Dersch P - PLoS ONE (2014)

Bottom Line: The two-component regulatory system PhoP/PhoQ has been shown to (i) control expression of virulence-associated traits, (ii) confer survival and growth within macrophages and (iii) play a role in Yersinia infections.Our results revealed that PhoP has a low impact on virulence, lymphatic and systemic organ colonization, and on immune response modulation by IP32953 and YPIII, indicating that PhoP is not absolutely essential for oral infections but may be involved in fine-tuning the outcome.Highlighted intra-species variations may provide a potential means to rapidly adjust to environmental changes inside and outside of the host.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany.

ABSTRACT
The two-component regulatory system PhoP/PhoQ has been shown to (i) control expression of virulence-associated traits, (ii) confer survival and growth within macrophages and (iii) play a role in Yersinia infections. However, the influence of PhoP on virulence varied greatly between different murine models of infection and its role in natural oral infections with frequently used representative isolates of Y. pseudotuberculosis was unknown. To address this issue, we constructed an isogenic set of phoP+ and phoP- variants of strain IP32953 and YPIII and analyzed the impact of PhoP using in vitro functionality experiments and a murine oral infection model, whereby we tested for bacterial dissemination and influence on the host immune response. Our results revealed that PhoP has a low impact on virulence, lymphatic and systemic organ colonization, and on immune response modulation by IP32953 and YPIII, indicating that PhoP is not absolutely essential for oral infections but may be involved in fine-tuning the outcome. Our work further revealed certain strain-specific differences in virulence properties, which do not strongly rely on the function of PhoP, but affect tissue colonization, dissemination and/or persistence of the bacteria. Highlighted intra-species variations may provide a potential means to rapidly adjust to environmental changes inside and outside of the host.

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Cytokine analysis of the serum of BALB/c mice infected with phoP+ and phoP− derivatives of Y. pseudotuberculosis YPIII or IP32953.Mice were challenged with 2×108 CFU of Y. pseudotuberculosis strains YPIII (phoP−) (n = 8), YP149 (YPIII phoP+) (n = 8), IP32953 (phoP+) (n = 8) and YPIP06 (IP32953 phoP−) (n = 8) in three independent experiments; a control group of uninfected mice (n = 5) was included. At day three postinfection blood was isolated to determine the cytokine profile of the serum. Cytokine levels were statistically analyzed using One-way ANOVA with Tukey’s post hoc test (+, p<0.05; ++, p<0.01; +++, p<0.001). + indicate a comparison to the uninfected group.
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pone-0103541-g007: Cytokine analysis of the serum of BALB/c mice infected with phoP+ and phoP− derivatives of Y. pseudotuberculosis YPIII or IP32953.Mice were challenged with 2×108 CFU of Y. pseudotuberculosis strains YPIII (phoP−) (n = 8), YP149 (YPIII phoP+) (n = 8), IP32953 (phoP+) (n = 8) and YPIP06 (IP32953 phoP−) (n = 8) in three independent experiments; a control group of uninfected mice (n = 5) was included. At day three postinfection blood was isolated to determine the cytokine profile of the serum. Cytokine levels were statistically analyzed using One-way ANOVA with Tukey’s post hoc test (+, p<0.05; ++, p<0.01; +++, p<0.001). + indicate a comparison to the uninfected group.

Mentions: Infection with Yersinia induced only an increase of selected cytokines at the systemic level with major differences between the different serotypes (Fig. 7). Notably, a significantly higher production of these cytokines was observed in IP32953 infected mice compared to mice challenged with YPIII regardless of the functionality of phoP. Among the most induced cytokines was G-CSF, which is responsible for the mobilization and activation of hematopoietic cells from the bone marrow (Fig. 7A), and the neutrophil-, monocyte- and DC-chemoattractant cytokines MCP-1, IP-10 and KC (Fig. 7C–E). Concentrations of these cytokines were 2–4 fold higher in the blood of IP32953-infected mice compared to YPIII-infected mice. Most likely, this inter-serotype difference in cytokine production is reflected in different neutrophil population levels within the infected organs (Fig. 4–6). Similarly, serum levels of the pleiotropic cytokine IFNγ and the potent systemic inflammation inducer TNFα were only slightly increased in mice infected with YPIII and YPIII phoP+ whereas significantly higher amounts of IFNγ were produced in response to IP32953 and IP32953 phoP−. Notably, lack of PhoP in the IP32953 strain also resulted in a considerably lower TNFα, IFNγ and IP-10 response in comparison to the wild-type strain. Finally, the serum analysis also highlighted a strain-dependent induction of IL-13. This cytokine is responsible for the establishment of a Th2 immune response against extracellular pathogens. Infection with the YPIII-derived strains did not induce a systemic increase of IL-13 in comparison to uninfected mice, while a 2-fold rise in its levels was observed in mice infected with IP32953 and IP32953 phoP−. In contrast, levels of the potent macrophage activator cytokine GM-CSF were only slightly affected by both Y. pseudotuberculosis strains at the time-point after infection (Fig. 7B). Taken together, these results reveal major differences in the systemic cytokine response between mice infected with YPIII and IP32953, mostly in a PhoP-independent fashion.


Influence of PhoP and intra-species variations on virulence of Yersinia pseudotuberculosis during the natural oral infection route.

Pisano F, Heine W, Rosenheinrich M, Schweer J, Nuss AM, Dersch P - PLoS ONE (2014)

Cytokine analysis of the serum of BALB/c mice infected with phoP+ and phoP− derivatives of Y. pseudotuberculosis YPIII or IP32953.Mice were challenged with 2×108 CFU of Y. pseudotuberculosis strains YPIII (phoP−) (n = 8), YP149 (YPIII phoP+) (n = 8), IP32953 (phoP+) (n = 8) and YPIP06 (IP32953 phoP−) (n = 8) in three independent experiments; a control group of uninfected mice (n = 5) was included. At day three postinfection blood was isolated to determine the cytokine profile of the serum. Cytokine levels were statistically analyzed using One-way ANOVA with Tukey’s post hoc test (+, p<0.05; ++, p<0.01; +++, p<0.001). + indicate a comparison to the uninfected group.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4116203&req=5

pone-0103541-g007: Cytokine analysis of the serum of BALB/c mice infected with phoP+ and phoP− derivatives of Y. pseudotuberculosis YPIII or IP32953.Mice were challenged with 2×108 CFU of Y. pseudotuberculosis strains YPIII (phoP−) (n = 8), YP149 (YPIII phoP+) (n = 8), IP32953 (phoP+) (n = 8) and YPIP06 (IP32953 phoP−) (n = 8) in three independent experiments; a control group of uninfected mice (n = 5) was included. At day three postinfection blood was isolated to determine the cytokine profile of the serum. Cytokine levels were statistically analyzed using One-way ANOVA with Tukey’s post hoc test (+, p<0.05; ++, p<0.01; +++, p<0.001). + indicate a comparison to the uninfected group.
Mentions: Infection with Yersinia induced only an increase of selected cytokines at the systemic level with major differences between the different serotypes (Fig. 7). Notably, a significantly higher production of these cytokines was observed in IP32953 infected mice compared to mice challenged with YPIII regardless of the functionality of phoP. Among the most induced cytokines was G-CSF, which is responsible for the mobilization and activation of hematopoietic cells from the bone marrow (Fig. 7A), and the neutrophil-, monocyte- and DC-chemoattractant cytokines MCP-1, IP-10 and KC (Fig. 7C–E). Concentrations of these cytokines were 2–4 fold higher in the blood of IP32953-infected mice compared to YPIII-infected mice. Most likely, this inter-serotype difference in cytokine production is reflected in different neutrophil population levels within the infected organs (Fig. 4–6). Similarly, serum levels of the pleiotropic cytokine IFNγ and the potent systemic inflammation inducer TNFα were only slightly increased in mice infected with YPIII and YPIII phoP+ whereas significantly higher amounts of IFNγ were produced in response to IP32953 and IP32953 phoP−. Notably, lack of PhoP in the IP32953 strain also resulted in a considerably lower TNFα, IFNγ and IP-10 response in comparison to the wild-type strain. Finally, the serum analysis also highlighted a strain-dependent induction of IL-13. This cytokine is responsible for the establishment of a Th2 immune response against extracellular pathogens. Infection with the YPIII-derived strains did not induce a systemic increase of IL-13 in comparison to uninfected mice, while a 2-fold rise in its levels was observed in mice infected with IP32953 and IP32953 phoP−. In contrast, levels of the potent macrophage activator cytokine GM-CSF were only slightly affected by both Y. pseudotuberculosis strains at the time-point after infection (Fig. 7B). Taken together, these results reveal major differences in the systemic cytokine response between mice infected with YPIII and IP32953, mostly in a PhoP-independent fashion.

Bottom Line: The two-component regulatory system PhoP/PhoQ has been shown to (i) control expression of virulence-associated traits, (ii) confer survival and growth within macrophages and (iii) play a role in Yersinia infections.Our results revealed that PhoP has a low impact on virulence, lymphatic and systemic organ colonization, and on immune response modulation by IP32953 and YPIII, indicating that PhoP is not absolutely essential for oral infections but may be involved in fine-tuning the outcome.Highlighted intra-species variations may provide a potential means to rapidly adjust to environmental changes inside and outside of the host.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany.

ABSTRACT
The two-component regulatory system PhoP/PhoQ has been shown to (i) control expression of virulence-associated traits, (ii) confer survival and growth within macrophages and (iii) play a role in Yersinia infections. However, the influence of PhoP on virulence varied greatly between different murine models of infection and its role in natural oral infections with frequently used representative isolates of Y. pseudotuberculosis was unknown. To address this issue, we constructed an isogenic set of phoP+ and phoP- variants of strain IP32953 and YPIII and analyzed the impact of PhoP using in vitro functionality experiments and a murine oral infection model, whereby we tested for bacterial dissemination and influence on the host immune response. Our results revealed that PhoP has a low impact on virulence, lymphatic and systemic organ colonization, and on immune response modulation by IP32953 and YPIII, indicating that PhoP is not absolutely essential for oral infections but may be involved in fine-tuning the outcome. Our work further revealed certain strain-specific differences in virulence properties, which do not strongly rely on the function of PhoP, but affect tissue colonization, dissemination and/or persistence of the bacteria. Highlighted intra-species variations may provide a potential means to rapidly adjust to environmental changes inside and outside of the host.

Show MeSH
Related in: MedlinePlus