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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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S. pneumoniae DNA activates type I IFN production. (A) Murine nasal epithelial cells were stimulated for 4 h with pneumococcal lysate that had been left untreated or treated with DNase. (B) Murine nasal epithelial cells were stimulated for 4 h with the WT or lytA mutant strain (n = 3). IFN-β induction was assessed by qRT-PCR and is displayed as fold induction over that in PBS-only controls. (C) Murine nasal epithelial cells were stimulated for 4 h with the WT and ply mutant strains (n = 3). DNA was extracted from the epithelial cells, and levels of S. pneumoniae 16S rRNA were measured by qRT-PCR. Un, untreated lysate. *, P < 0.05 compared to WT or untreated samples (Student’s t test). All results shown are representative of at least two independent experiments.
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f4: S. pneumoniae DNA activates type I IFN production. (A) Murine nasal epithelial cells were stimulated for 4 h with pneumococcal lysate that had been left untreated or treated with DNase. (B) Murine nasal epithelial cells were stimulated for 4 h with the WT or lytA mutant strain (n = 3). IFN-β induction was assessed by qRT-PCR and is displayed as fold induction over that in PBS-only controls. (C) Murine nasal epithelial cells were stimulated for 4 h with the WT and ply mutant strains (n = 3). DNA was extracted from the epithelial cells, and levels of S. pneumoniae 16S rRNA were measured by qRT-PCR. Un, untreated lysate. *, P < 0.05 compared to WT or untreated samples (Student’s t test). All results shown are representative of at least two independent experiments.

Mentions: During active growth, pneumococci spontaneously lyse, releasing cellular components, including DNA. S. pneumoniae produces an autolysin (LytA, an amidase) required for autolysis and release of cell wall components (9). Incubation of epithelial cells with a lytA strain of S. pneumoniae did not activate type I IFN signaling (Fig. 4B), indicating that the inducing ligand is liberated from lysed cells. DNA is a potent activator of type I IFN signaling, and Ply could permit bacterial DNA to enter the cytosol, where it would interact with one or more of the several different types of DNA sensors that induce type I IFN signaling (11). Pneumococcal lysates incubated with DNase were found to stimulate significantly less (P = 0.046) Ifnb than control lysates (Fig. 4A), further implicating pneumococcal DNA as the ligand. To further implicate pneumolysin in enabling DNA entry into the epithelial cells, we demonstrated increased amounts of pneumococcal DNA in murine epithelial cells incubated with WT S. pneumoniae compared to the ply mutant (Fig. 4C). However, reconstitution of the system in vitro, i.e., adding purified Ply and S. pneumoniae DNA to murine airway epithelial cells in primary culture, did not result in Ifnb induction.


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)

S. pneumoniae DNA activates type I IFN production. (A) Murine nasal epithelial cells were stimulated for 4 h with pneumococcal lysate that had been left untreated or treated with DNase. (B) Murine nasal epithelial cells were stimulated for 4 h with the WT or lytA mutant strain (n = 3). IFN-β induction was assessed by qRT-PCR and is displayed as fold induction over that in PBS-only controls. (C) Murine nasal epithelial cells were stimulated for 4 h with the WT and ply mutant strains (n = 3). DNA was extracted from the epithelial cells, and levels of S. pneumoniae 16S rRNA were measured by qRT-PCR. Un, untreated lysate. *, P < 0.05 compared to WT or untreated samples (Student’s t test). All results shown are representative of at least two independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3101776&req=5

f4: S. pneumoniae DNA activates type I IFN production. (A) Murine nasal epithelial cells were stimulated for 4 h with pneumococcal lysate that had been left untreated or treated with DNase. (B) Murine nasal epithelial cells were stimulated for 4 h with the WT or lytA mutant strain (n = 3). IFN-β induction was assessed by qRT-PCR and is displayed as fold induction over that in PBS-only controls. (C) Murine nasal epithelial cells were stimulated for 4 h with the WT and ply mutant strains (n = 3). DNA was extracted from the epithelial cells, and levels of S. pneumoniae 16S rRNA were measured by qRT-PCR. Un, untreated lysate. *, P < 0.05 compared to WT or untreated samples (Student’s t test). All results shown are representative of at least two independent experiments.
Mentions: During active growth, pneumococci spontaneously lyse, releasing cellular components, including DNA. S. pneumoniae produces an autolysin (LytA, an amidase) required for autolysis and release of cell wall components (9). Incubation of epithelial cells with a lytA strain of S. pneumoniae did not activate type I IFN signaling (Fig. 4B), indicating that the inducing ligand is liberated from lysed cells. DNA is a potent activator of type I IFN signaling, and Ply could permit bacterial DNA to enter the cytosol, where it would interact with one or more of the several different types of DNA sensors that induce type I IFN signaling (11). Pneumococcal lysates incubated with DNase were found to stimulate significantly less (P = 0.046) Ifnb than control lysates (Fig. 4A), further implicating pneumococcal DNA as the ligand. To further implicate pneumolysin in enabling DNA entry into the epithelial cells, we demonstrated increased amounts of pneumococcal DNA in murine epithelial cells incubated with WT S. pneumoniae compared to the ply mutant (Fig. 4C). However, reconstitution of the system in vitro, i.e., adding purified Ply and S. pneumoniae DNA to murine airway epithelial cells in primary culture, did not result in Ifnb induction.

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