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Streptococcus pneumoniae DNA initiates type I interferon signaling in the respiratory tract.

Parker D, Martin FJ, Soong G, Harfenist BS, Aguilar JL, Ratner AJ, Fitzgerald KA, Schindler C, Prince A - MBio (2011)

Bottom Line: These studies suggest that the type I IFN cascade is a central component of the mucosal response to airway bacterial pathogens and is responsive to bacterial pathogen-associated molecular patterns that are capable of accessing intracellular receptors.Although it is known that antibody is critical for efficient phagocytosis, it is not known how this pathogen is sensed by the mucosal epithelium.We demonstrate that this extracellular pathogen activates mucosal signaling typically activated by viral pathogens via the pneumolysin pore to activate intracellular receptors and the type I interferon (IFN) cascade.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA. dp2375@columbia.edu

ABSTRACT

Unlabelled: The mucosal epithelium is the initial target for respiratory pathogens of all types. While type I interferon (IFN) signaling is traditionally associated with antiviral immunity, we demonstrate that the extracellular bacterial pathogen Streptococcus pneumoniae activates the type I IFN cascade in airway epithelial and dendritic cells. This response is dependent upon the pore-forming toxin pneumolysin. Pneumococcal DNA activates IFN-β expression through a DAI/STING/TBK1/IRF3 cascade. Tlr4(-/-), Myd88(-/-), Trif(-/-), and Nod2(-/-) mutant mice had no impairment of type I IFN signaling. Induction of type I IFN signaling contributes to the eradication of pneumococcal carriage, as IFN-α/β receptor mice had significantly increased nasal colonization with S. pneumoniae compared with that of wild-type mice. These studies suggest that the type I IFN cascade is a central component of the mucosal response to airway bacterial pathogens and is responsive to bacterial pathogen-associated molecular patterns that are capable of accessing intracellular receptors.

Importance: The bacterium Streptococcus pneumoniae is a leading cause of bacterial pneumonia, leading to upwards of one million deaths a year worldwide and significant economic burden. Although it is known that antibody is critical for efficient phagocytosis, it is not known how this pathogen is sensed by the mucosal epithelium. We demonstrate that this extracellular pathogen activates mucosal signaling typically activated by viral pathogens via the pneumolysin pore to activate intracellular receptors and the type I interferon (IFN) cascade. Mice lacking the receptor to type I IFNs have a reduced ability to clear S. pneumoniae, suggesting that the type I IFN cascade is central to the mucosal clearance of this important pathogen.

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Pneumolysin is involved in the induction of type I IFN. C57BL/6J mice were infected with 2 × 107 CFU of S. pneumoniae (S. p.) intranasally and studied at 4 h (A to D). (A) WT-infected lung data are shown in black, and ply mutant-infected lung data are shaded grey. *, P < 0.05 (Student’s t test; n = 8). Lung homogenates were analyzed for bacterial counts (B), neutrophils (percentage of Ly6G Ly6C+ CD45+ cells) (C), and CD11c+ cells (D) by FACS. Lines represent median values. *, P < 0.05 (WT versus ply mutant; Mann-Whitney test; n = 8, except for the PBS controls). (E) Murine nasal epithelial cells in primary culture were stimulated for the times indicated with WT or ply mutant S. pneumoniae D39 in the presence or absence of cytochalasin D (CytoD) (F). DMSO, dimethyl sulfoxide. *, P < 0.05 (Student’s t test; n = 3). (G) Mice were intranasally administered S. pneumoniae strains (P1121 background) expressing WT pneumolysin, no pneumolysin, or a nonhemolytic toxoid variant and examined 4 h later. Lung homogenates were immunoblotted for P-STAT1. Each lane represents an individual mouse. (H) AF488-labeled pneumolysin is visualized in murine nasal epithelial cells at 1 h poststimulation. Murine epithelial cells in primary culture following stimulation with S. pneumoniae D39 or purified pneumolysin (Ply) (I) or with ply lysates with and without purified pneumolysin or PdB (J). *, P < 0.05 compared to unstimulated cells (Student’s t test; n = 3). RNA was extracted and analyzed for levels of IFN-β by qRT-PCR. All graphs display means with standard deviations.
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f2: Pneumolysin is involved in the induction of type I IFN. C57BL/6J mice were infected with 2 × 107 CFU of S. pneumoniae (S. p.) intranasally and studied at 4 h (A to D). (A) WT-infected lung data are shown in black, and ply mutant-infected lung data are shaded grey. *, P < 0.05 (Student’s t test; n = 8). Lung homogenates were analyzed for bacterial counts (B), neutrophils (percentage of Ly6G Ly6C+ CD45+ cells) (C), and CD11c+ cells (D) by FACS. Lines represent median values. *, P < 0.05 (WT versus ply mutant; Mann-Whitney test; n = 8, except for the PBS controls). (E) Murine nasal epithelial cells in primary culture were stimulated for the times indicated with WT or ply mutant S. pneumoniae D39 in the presence or absence of cytochalasin D (CytoD) (F). DMSO, dimethyl sulfoxide. *, P < 0.05 (Student’s t test; n = 3). (G) Mice were intranasally administered S. pneumoniae strains (P1121 background) expressing WT pneumolysin, no pneumolysin, or a nonhemolytic toxoid variant and examined 4 h later. Lung homogenates were immunoblotted for P-STAT1. Each lane represents an individual mouse. (H) AF488-labeled pneumolysin is visualized in murine nasal epithelial cells at 1 h poststimulation. Murine epithelial cells in primary culture following stimulation with S. pneumoniae D39 or purified pneumolysin (Ply) (I) or with ply lysates with and without purified pneumolysin or PdB (J). *, P < 0.05 compared to unstimulated cells (Student’s t test; n = 3). RNA was extracted and analyzed for levels of IFN-β by qRT-PCR. All graphs display means with standard deviations.

Mentions: S. pneumoniae pneumolysin is reported to interact with TLR4 (7, 18), which interacts with TRIF (TIR domain-containing adapter inducing IFN-β) to participate in the induction of type I IFN signaling. Recent data (19) have suggested that the immune response to pneumolysin does not involve TLR4. Pneumolysin also functions as a pore that allows bacterial PAMPs access to the epithelial cytosol and pathogen recognition receptors (10). We assessed Ifnb production in mice 4 h following intranasal infection with 107 CFU of wild-type (WT) S. pneumoniae D39 or a ply mutant. There was 40-fold induction of Ifnb by the WT S. pneumoniae strain under these conditions but only a 3-fold induction in mice infected with the ply mutant (P = 0.029) (Fig. 2A). At this 4-h time point, LIF and Mx1 were expressed and this expression was pneumolysin dependent. Significantly reduced levels of KC and IL-6 were also associated with exposure to the ply mutant (P < 0.001).


Streptococcus pneumoniae DNA initiates type I interferon signaling in the respiratory tract.

Parker D, Martin FJ, Soong G, Harfenist BS, Aguilar JL, Ratner AJ, Fitzgerald KA, Schindler C, Prince A - MBio (2011)

Pneumolysin is involved in the induction of type I IFN. C57BL/6J mice were infected with 2 × 107 CFU of S. pneumoniae (S. p.) intranasally and studied at 4 h (A to D). (A) WT-infected lung data are shown in black, and ply mutant-infected lung data are shaded grey. *, P < 0.05 (Student’s t test; n = 8). Lung homogenates were analyzed for bacterial counts (B), neutrophils (percentage of Ly6G Ly6C+ CD45+ cells) (C), and CD11c+ cells (D) by FACS. Lines represent median values. *, P < 0.05 (WT versus ply mutant; Mann-Whitney test; n = 8, except for the PBS controls). (E) Murine nasal epithelial cells in primary culture were stimulated for the times indicated with WT or ply mutant S. pneumoniae D39 in the presence or absence of cytochalasin D (CytoD) (F). DMSO, dimethyl sulfoxide. *, P < 0.05 (Student’s t test; n = 3). (G) Mice were intranasally administered S. pneumoniae strains (P1121 background) expressing WT pneumolysin, no pneumolysin, or a nonhemolytic toxoid variant and examined 4 h later. Lung homogenates were immunoblotted for P-STAT1. Each lane represents an individual mouse. (H) AF488-labeled pneumolysin is visualized in murine nasal epithelial cells at 1 h poststimulation. Murine epithelial cells in primary culture following stimulation with S. pneumoniae D39 or purified pneumolysin (Ply) (I) or with ply lysates with and without purified pneumolysin or PdB (J). *, P < 0.05 compared to unstimulated cells (Student’s t test; n = 3). RNA was extracted and analyzed for levels of IFN-β by qRT-PCR. All graphs display means with standard deviations.
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Related In: Results  -  Collection

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f2: Pneumolysin is involved in the induction of type I IFN. C57BL/6J mice were infected with 2 × 107 CFU of S. pneumoniae (S. p.) intranasally and studied at 4 h (A to D). (A) WT-infected lung data are shown in black, and ply mutant-infected lung data are shaded grey. *, P < 0.05 (Student’s t test; n = 8). Lung homogenates were analyzed for bacterial counts (B), neutrophils (percentage of Ly6G Ly6C+ CD45+ cells) (C), and CD11c+ cells (D) by FACS. Lines represent median values. *, P < 0.05 (WT versus ply mutant; Mann-Whitney test; n = 8, except for the PBS controls). (E) Murine nasal epithelial cells in primary culture were stimulated for the times indicated with WT or ply mutant S. pneumoniae D39 in the presence or absence of cytochalasin D (CytoD) (F). DMSO, dimethyl sulfoxide. *, P < 0.05 (Student’s t test; n = 3). (G) Mice were intranasally administered S. pneumoniae strains (P1121 background) expressing WT pneumolysin, no pneumolysin, or a nonhemolytic toxoid variant and examined 4 h later. Lung homogenates were immunoblotted for P-STAT1. Each lane represents an individual mouse. (H) AF488-labeled pneumolysin is visualized in murine nasal epithelial cells at 1 h poststimulation. Murine epithelial cells in primary culture following stimulation with S. pneumoniae D39 or purified pneumolysin (Ply) (I) or with ply lysates with and without purified pneumolysin or PdB (J). *, P < 0.05 compared to unstimulated cells (Student’s t test; n = 3). RNA was extracted and analyzed for levels of IFN-β by qRT-PCR. All graphs display means with standard deviations.
Mentions: S. pneumoniae pneumolysin is reported to interact with TLR4 (7, 18), which interacts with TRIF (TIR domain-containing adapter inducing IFN-β) to participate in the induction of type I IFN signaling. Recent data (19) have suggested that the immune response to pneumolysin does not involve TLR4. Pneumolysin also functions as a pore that allows bacterial PAMPs access to the epithelial cytosol and pathogen recognition receptors (10). We assessed Ifnb production in mice 4 h following intranasal infection with 107 CFU of wild-type (WT) S. pneumoniae D39 or a ply mutant. There was 40-fold induction of Ifnb by the WT S. pneumoniae strain under these conditions but only a 3-fold induction in mice infected with the ply mutant (P = 0.029) (Fig. 2A). At this 4-h time point, LIF and Mx1 were expressed and this expression was pneumolysin dependent. Significantly reduced levels of KC and IL-6 were also associated with exposure to the ply mutant (P < 0.001).

Bottom Line: These studies suggest that the type I IFN cascade is a central component of the mucosal response to airway bacterial pathogens and is responsive to bacterial pathogen-associated molecular patterns that are capable of accessing intracellular receptors.Although it is known that antibody is critical for efficient phagocytosis, it is not known how this pathogen is sensed by the mucosal epithelium.We demonstrate that this extracellular pathogen activates mucosal signaling typically activated by viral pathogens via the pneumolysin pore to activate intracellular receptors and the type I interferon (IFN) cascade.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA. dp2375@columbia.edu

ABSTRACT

Unlabelled: The mucosal epithelium is the initial target for respiratory pathogens of all types. While type I interferon (IFN) signaling is traditionally associated with antiviral immunity, we demonstrate that the extracellular bacterial pathogen Streptococcus pneumoniae activates the type I IFN cascade in airway epithelial and dendritic cells. This response is dependent upon the pore-forming toxin pneumolysin. Pneumococcal DNA activates IFN-β expression through a DAI/STING/TBK1/IRF3 cascade. Tlr4(-/-), Myd88(-/-), Trif(-/-), and Nod2(-/-) mutant mice had no impairment of type I IFN signaling. Induction of type I IFN signaling contributes to the eradication of pneumococcal carriage, as IFN-α/β receptor mice had significantly increased nasal colonization with S. pneumoniae compared with that of wild-type mice. These studies suggest that the type I IFN cascade is a central component of the mucosal response to airway bacterial pathogens and is responsive to bacterial pathogen-associated molecular patterns that are capable of accessing intracellular receptors.

Importance: The bacterium Streptococcus pneumoniae is a leading cause of bacterial pneumonia, leading to upwards of one million deaths a year worldwide and significant economic burden. Although it is known that antibody is critical for efficient phagocytosis, it is not known how this pathogen is sensed by the mucosal epithelium. We demonstrate that this extracellular pathogen activates mucosal signaling typically activated by viral pathogens via the pneumolysin pore to activate intracellular receptors and the type I interferon (IFN) cascade. Mice lacking the receptor to type I IFNs have a reduced ability to clear S. pneumoniae, suggesting that the type I IFN cascade is central to the mucosal clearance of this important pathogen.

Show MeSH
Related in: MedlinePlus