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The impact of pneumolysin on the macrophage response to Streptococcus pneumoniae is strain-dependent.

Harvey RM, Hughes CE, Paton AW, Trappetti C, Tweten RK, Paton JC - PLoS ONE (2014)

Bottom Line: In recent times a clinically significant and internationally successful serotype 1 ST306 clone has been found to express a non-cytolytic variant of Ply (Ply306).Strains that expressed cytolytic Ply were found to induce a significant increase in IL-1β release from macrophage-like cells compared to the non-cytolytic and Ply-deficient strains in a background-independent manner, confirming the requirement for pore formation in the Ply-dependent activation of the NLRP3 inflammasome.However, cytolytic activity in the D39 background was found to induce increased expression of the genes encoding GM-CSF (CSF2), p19 subunit of IL-23 (IL23A) and IFNβ (IFNB1) compared to non-cytolytic and Ply-deficient D39 mutants, but had no effect in the A0229467 background.

View Article: PubMed Central - PubMed

Affiliation: Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, Australia.

ABSTRACT
Streptococcus pneumoniae is the world's leading cause of pneumonia, bacteremia, meningitis and otitis media. A major pneumococcal virulence factor is the cholesterol-dependent cytolysin, which has the defining property of forming pores in cholesterol-containing membranes. In recent times a clinically significant and internationally successful serotype 1 ST306 clone has been found to express a non-cytolytic variant of Ply (Ply306). However, while the pneumococcus is a naturally transformable organism, strains of the ST306 clonal group have to date been virtually impossible to transform, severely restricting efforts to understand the role of non-cytolytic Ply in the success of this clone. In this study isogenic Ply mutants were constructed in the D39 background and for the first time in the ST306 background (A0229467) to enable direct comparisons between Ply variants for their impact on the immune response in a macrophage-like cell line. Strains that expressed cytolytic Ply were found to induce a significant increase in IL-1β release from macrophage-like cells compared to the non-cytolytic and Ply-deficient strains in a background-independent manner, confirming the requirement for pore formation in the Ply-dependent activation of the NLRP3 inflammasome. However, cytolytic activity in the D39 background was found to induce increased expression of the genes encoding GM-CSF (CSF2), p19 subunit of IL-23 (IL23A) and IFNβ (IFNB1) compared to non-cytolytic and Ply-deficient D39 mutants, but had no effect in the A0229467 background. The impact of Ply on the immune response to the pneumococcus is highly dependent on the strain background, thus emphasising the importance of the interaction between specific virulence factors and other components of the genetic background of this organism.

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Related in: MedlinePlus

Survival of mice challenged with isogenic Ply mutants in D39.Survival times of groups of 12 CD1 mice challenged with 104 CFU of the indicated strain via the intraperitoneal route of challenge. Statistical significance was calculated using the one-way ANOVA and Kruskal-Wallis and Dunn's multiple comparisons test (‘*’ P<0.05; ‘**’ P<0.01, ‘***’ P<0.001).
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pone-0103625-g001: Survival of mice challenged with isogenic Ply mutants in D39.Survival times of groups of 12 CD1 mice challenged with 104 CFU of the indicated strain via the intraperitoneal route of challenge. Statistical significance was calculated using the one-way ANOVA and Kruskal-Wallis and Dunn's multiple comparisons test (‘*’ P<0.05; ‘**’ P<0.01, ‘***’ P<0.001).

Mentions: D39 was constructed to express the naturally occurring non-cytolytic Ply306 variant. The virulence of D39, D39ΔPly and D39::Ply306 was compared to determine whether the lack of cytolytic activity exhibited by Ply306 would lead to increased survival when expressed in D39. The survival times of groups of 12 mice challenged intraperitoneally with 104 CFU of each strain D39, D39ΔPly or D39::Ply306 were compared (Fig. 1). The median survival time of mice challenged with D39ΔPly was significantly longer than both the wild type (P<0.001) and D39::Ply306 (P<0.05), but there was a much smaller but nevertheless statistically significant difference in median survival times between the wild type and D39::Ply306 (P>0.05). Thus, we confirm that while the cytolytic properties of Ply do contribute the virulence of wild type D39, the non-cytolytic properties appear to be much more important in this model.


The impact of pneumolysin on the macrophage response to Streptococcus pneumoniae is strain-dependent.

Harvey RM, Hughes CE, Paton AW, Trappetti C, Tweten RK, Paton JC - PLoS ONE (2014)

Survival of mice challenged with isogenic Ply mutants in D39.Survival times of groups of 12 CD1 mice challenged with 104 CFU of the indicated strain via the intraperitoneal route of challenge. Statistical significance was calculated using the one-way ANOVA and Kruskal-Wallis and Dunn's multiple comparisons test (‘*’ P<0.05; ‘**’ P<0.01, ‘***’ P<0.001).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126675&req=5

pone-0103625-g001: Survival of mice challenged with isogenic Ply mutants in D39.Survival times of groups of 12 CD1 mice challenged with 104 CFU of the indicated strain via the intraperitoneal route of challenge. Statistical significance was calculated using the one-way ANOVA and Kruskal-Wallis and Dunn's multiple comparisons test (‘*’ P<0.05; ‘**’ P<0.01, ‘***’ P<0.001).
Mentions: D39 was constructed to express the naturally occurring non-cytolytic Ply306 variant. The virulence of D39, D39ΔPly and D39::Ply306 was compared to determine whether the lack of cytolytic activity exhibited by Ply306 would lead to increased survival when expressed in D39. The survival times of groups of 12 mice challenged intraperitoneally with 104 CFU of each strain D39, D39ΔPly or D39::Ply306 were compared (Fig. 1). The median survival time of mice challenged with D39ΔPly was significantly longer than both the wild type (P<0.001) and D39::Ply306 (P<0.05), but there was a much smaller but nevertheless statistically significant difference in median survival times between the wild type and D39::Ply306 (P>0.05). Thus, we confirm that while the cytolytic properties of Ply do contribute the virulence of wild type D39, the non-cytolytic properties appear to be much more important in this model.

Bottom Line: In recent times a clinically significant and internationally successful serotype 1 ST306 clone has been found to express a non-cytolytic variant of Ply (Ply306).Strains that expressed cytolytic Ply were found to induce a significant increase in IL-1β release from macrophage-like cells compared to the non-cytolytic and Ply-deficient strains in a background-independent manner, confirming the requirement for pore formation in the Ply-dependent activation of the NLRP3 inflammasome.However, cytolytic activity in the D39 background was found to induce increased expression of the genes encoding GM-CSF (CSF2), p19 subunit of IL-23 (IL23A) and IFNβ (IFNB1) compared to non-cytolytic and Ply-deficient D39 mutants, but had no effect in the A0229467 background.

View Article: PubMed Central - PubMed

Affiliation: Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, Australia.

ABSTRACT
Streptococcus pneumoniae is the world's leading cause of pneumonia, bacteremia, meningitis and otitis media. A major pneumococcal virulence factor is the cholesterol-dependent cytolysin, which has the defining property of forming pores in cholesterol-containing membranes. In recent times a clinically significant and internationally successful serotype 1 ST306 clone has been found to express a non-cytolytic variant of Ply (Ply306). However, while the pneumococcus is a naturally transformable organism, strains of the ST306 clonal group have to date been virtually impossible to transform, severely restricting efforts to understand the role of non-cytolytic Ply in the success of this clone. In this study isogenic Ply mutants were constructed in the D39 background and for the first time in the ST306 background (A0229467) to enable direct comparisons between Ply variants for their impact on the immune response in a macrophage-like cell line. Strains that expressed cytolytic Ply were found to induce a significant increase in IL-1β release from macrophage-like cells compared to the non-cytolytic and Ply-deficient strains in a background-independent manner, confirming the requirement for pore formation in the Ply-dependent activation of the NLRP3 inflammasome. However, cytolytic activity in the D39 background was found to induce increased expression of the genes encoding GM-CSF (CSF2), p19 subunit of IL-23 (IL23A) and IFNβ (IFNB1) compared to non-cytolytic and Ply-deficient D39 mutants, but had no effect in the A0229467 background. The impact of Ply on the immune response to the pneumococcus is highly dependent on the strain background, thus emphasising the importance of the interaction between specific virulence factors and other components of the genetic background of this organism.

Show MeSH
Related in: MedlinePlus