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Streptolysin O Rapidly Impairs Neutrophil Oxidative Burst and Antibacterial Responses to Group A Streptococcus.

Uchiyama S, Döhrmann S, Timmer AM, Dixit N, Ghochani M, Bhandari T, Timmer JC, Sprague K, Bubeck-Wardenburg J, Simon SI, Nizet V - Front Immunol (2015)

Bottom Line: Group A Streptococcus (GAS) causes a wide range of human infections, ranging from simple pharyngitis to life-threatening necrotizing fasciitis and toxic shock syndrome.The secreted GAS pore-forming toxin streptolysin O (SLO), which induces eukaryotic cell lysis in a cholesterol-dependent manner, is highly upregulated in the GAS M1T1 clone during bloodstream dissemination.We conclude that SLO exerts a novel cytotoxic-independent function at early stages of invasive infections (<30 min), contributing to GAS escape from neutrophil clearance.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, University of California San Diego , La Jolla, CA , USA.

ABSTRACT
Group A Streptococcus (GAS) causes a wide range of human infections, ranging from simple pharyngitis to life-threatening necrotizing fasciitis and toxic shock syndrome. A globally disseminated clone of M1T1 GAS has been associated with an increase in severe, invasive GAS infections in recent decades. The secreted GAS pore-forming toxin streptolysin O (SLO), which induces eukaryotic cell lysis in a cholesterol-dependent manner, is highly upregulated in the GAS M1T1 clone during bloodstream dissemination. SLO is known to promote GAS resistance to phagocytic clearance by neutrophils, a critical first element of host defense against invasive bacterial infection. Here, we examine the role of SLO in modulating specific neutrophil functions during their early interaction with GAS. We find that SLO at subcytotoxic concentrations and early time points is necessary and sufficient to suppress neutrophil oxidative burst, in a manner reversed by free cholesterol and anti-SLO blocking antibodies. In addition, SLO at subcytotoxic concentrations blocked neutrophil degranulation, interleukin-8 secretion and responsiveness, and elaboration of DNA-based neutrophil extracellular traps, cumulatively supporting a key role for SLO in GAS resistance to immediate neutrophil killing. A non-toxic SLO derivate elicits protective immunity against lethal GAS challenge in a murine infection model. We conclude that SLO exerts a novel cytotoxic-independent function at early stages of invasive infections (<30 min), contributing to GAS escape from neutrophil clearance.

No MeSH data available.


Related in: MedlinePlus

Streptolysin O inhibits neutrophil degranulation and IL-8 release/responsiveness. (A) Neutrophil degranulation was determined by elastase release upon infection with live GAS WT, ΔSLO mutant, complemented bacteria and media only control, as quantified by ELISA. (B) SLO prevents IL-8 release from infected neutrophils compared to ΔSLO mutant bacteria and media only control as quantified by ELISA. (C) SLO inhibits neutrophil migration in MOI-dependent manner in contrast to ΔSLO mutant bacteria and media only control as measured by microscopic analysis. Results are given in average ± SEM and analyzed by Student’s t-test (n.s., not significant).
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Figure 4: Streptolysin O inhibits neutrophil degranulation and IL-8 release/responsiveness. (A) Neutrophil degranulation was determined by elastase release upon infection with live GAS WT, ΔSLO mutant, complemented bacteria and media only control, as quantified by ELISA. (B) SLO prevents IL-8 release from infected neutrophils compared to ΔSLO mutant bacteria and media only control as quantified by ELISA. (C) SLO inhibits neutrophil migration in MOI-dependent manner in contrast to ΔSLO mutant bacteria and media only control as measured by microscopic analysis. Results are given in average ± SEM and analyzed by Student’s t-test (n.s., not significant).

Mentions: Reactive oxygen species have been implicated in the activation of neutrophil granule proteases including elastase (41, 42). GAS suppressed the degranulation of neutrophils in a SLO-dependent manner as quantified by elastase release into the supernatant (Figure 4A). Activated neutrophils themselves are an important source of chemokine interleukin-8 (IL-8), the release of which recruits additional neutrophils to the site of inflammation or infection (43). After 60 min bacterial coincubation, we observed a clear reduction in IL-8 secretion by neutrophils exposed to WT GAS compared to the ΔSLO mutant (Figure 4B). Finally, the mean distance of neutrophil migration over 3 min in response to IL-8 as stimulus was significantly reduced in neutrophils exposed to WT GAS compared to those exposed to the ΔSLO mutant (Figure 4C). Thus, SLO production by GAS impairs neutrophil IL-8 release and their activation and migratory responses to the chemokine.


Streptolysin O Rapidly Impairs Neutrophil Oxidative Burst and Antibacterial Responses to Group A Streptococcus.

Uchiyama S, Döhrmann S, Timmer AM, Dixit N, Ghochani M, Bhandari T, Timmer JC, Sprague K, Bubeck-Wardenburg J, Simon SI, Nizet V - Front Immunol (2015)

Streptolysin O inhibits neutrophil degranulation and IL-8 release/responsiveness. (A) Neutrophil degranulation was determined by elastase release upon infection with live GAS WT, ΔSLO mutant, complemented bacteria and media only control, as quantified by ELISA. (B) SLO prevents IL-8 release from infected neutrophils compared to ΔSLO mutant bacteria and media only control as quantified by ELISA. (C) SLO inhibits neutrophil migration in MOI-dependent manner in contrast to ΔSLO mutant bacteria and media only control as measured by microscopic analysis. Results are given in average ± SEM and analyzed by Student’s t-test (n.s., not significant).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4644796&req=5

Figure 4: Streptolysin O inhibits neutrophil degranulation and IL-8 release/responsiveness. (A) Neutrophil degranulation was determined by elastase release upon infection with live GAS WT, ΔSLO mutant, complemented bacteria and media only control, as quantified by ELISA. (B) SLO prevents IL-8 release from infected neutrophils compared to ΔSLO mutant bacteria and media only control as quantified by ELISA. (C) SLO inhibits neutrophil migration in MOI-dependent manner in contrast to ΔSLO mutant bacteria and media only control as measured by microscopic analysis. Results are given in average ± SEM and analyzed by Student’s t-test (n.s., not significant).
Mentions: Reactive oxygen species have been implicated in the activation of neutrophil granule proteases including elastase (41, 42). GAS suppressed the degranulation of neutrophils in a SLO-dependent manner as quantified by elastase release into the supernatant (Figure 4A). Activated neutrophils themselves are an important source of chemokine interleukin-8 (IL-8), the release of which recruits additional neutrophils to the site of inflammation or infection (43). After 60 min bacterial coincubation, we observed a clear reduction in IL-8 secretion by neutrophils exposed to WT GAS compared to the ΔSLO mutant (Figure 4B). Finally, the mean distance of neutrophil migration over 3 min in response to IL-8 as stimulus was significantly reduced in neutrophils exposed to WT GAS compared to those exposed to the ΔSLO mutant (Figure 4C). Thus, SLO production by GAS impairs neutrophil IL-8 release and their activation and migratory responses to the chemokine.

Bottom Line: Group A Streptococcus (GAS) causes a wide range of human infections, ranging from simple pharyngitis to life-threatening necrotizing fasciitis and toxic shock syndrome.The secreted GAS pore-forming toxin streptolysin O (SLO), which induces eukaryotic cell lysis in a cholesterol-dependent manner, is highly upregulated in the GAS M1T1 clone during bloodstream dissemination.We conclude that SLO exerts a novel cytotoxic-independent function at early stages of invasive infections (<30 min), contributing to GAS escape from neutrophil clearance.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, University of California San Diego , La Jolla, CA , USA.

ABSTRACT
Group A Streptococcus (GAS) causes a wide range of human infections, ranging from simple pharyngitis to life-threatening necrotizing fasciitis and toxic shock syndrome. A globally disseminated clone of M1T1 GAS has been associated with an increase in severe, invasive GAS infections in recent decades. The secreted GAS pore-forming toxin streptolysin O (SLO), which induces eukaryotic cell lysis in a cholesterol-dependent manner, is highly upregulated in the GAS M1T1 clone during bloodstream dissemination. SLO is known to promote GAS resistance to phagocytic clearance by neutrophils, a critical first element of host defense against invasive bacterial infection. Here, we examine the role of SLO in modulating specific neutrophil functions during their early interaction with GAS. We find that SLO at subcytotoxic concentrations and early time points is necessary and sufficient to suppress neutrophil oxidative burst, in a manner reversed by free cholesterol and anti-SLO blocking antibodies. In addition, SLO at subcytotoxic concentrations blocked neutrophil degranulation, interleukin-8 secretion and responsiveness, and elaboration of DNA-based neutrophil extracellular traps, cumulatively supporting a key role for SLO in GAS resistance to immediate neutrophil killing. A non-toxic SLO derivate elicits protective immunity against lethal GAS challenge in a murine infection model. We conclude that SLO exerts a novel cytotoxic-independent function at early stages of invasive infections (<30 min), contributing to GAS escape from neutrophil clearance.

No MeSH data available.


Related in: MedlinePlus