Type I interferon production induced by Streptococcus pyogenes-derived nucleic acids is required for host protection

PLoS Pathog. 2011 May;7(5):e1001345. doi: 10.1371/journal.ppat.1001345. Epub 2011 May 19.

Abstract

Streptococcus pyogenes is a Gram-positive human pathogen that is recognized by yet unknown pattern recognition receptors (PRRs). Engagement of these receptor molecules during infection with S. pyogenes, a largely extracellular bacterium with limited capacity for intracellular survival, causes innate immune cells to produce inflammatory mediators such as TNF, but also type I interferon (IFN). Here we show that signaling elicited by type I IFNs is required for successful defense of mice against lethal subcutaneous cellulitis caused by S. pyogenes. Type I IFN signaling was accompanied with reduced neutrophil recruitment to the site of infection. Mechanistic analysis revealed that macrophages and conventional dendritic cells (cDCs) employ different signaling pathways leading to IFN-beta production. Macrophages required IRF3, STING, TBK1 and partially MyD88, whereas in cDCs the IFN-beta production was fully dependent on IRF5 and MyD88. Furthermore, IFN-beta production by macrophages was dependent on the endosomal delivery of streptococcal DNA, while in cDCs streptococcal RNA was identified as the IFN-beta inducer. Despite a role of MyD88 in both cell types, the known IFN-inducing TLRs were individually not required for generation of the IFN-beta response. These results demonstrate that the innate immune system employs several strategies to efficiently recognize S. pyogenes, a pathogenic bacterium that succeeded in avoiding recognition by the standard arsenal of TLRs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cells, Cultured
  • Cellulitis / microbiology
  • Cellulitis / mortality
  • DNA, Bacterial / metabolism*
  • Dendritic Cells* / immunology
  • Dendritic Cells* / metabolism
  • Dendritic Cells* / microbiology
  • Gene Silencing
  • Immunity, Innate
  • Interferon Regulatory Factor-3
  • Interferon Regulatory Factors
  • Interferon-beta / biosynthesis
  • Macrophages* / immunology
  • Macrophages* / metabolism
  • Macrophages* / microbiology
  • Membrane Proteins
  • Mice
  • Mice, Inbred C57BL
  • Microscopy, Fluorescence
  • Myeloid Differentiation Factor 88
  • Neutrophil Infiltration / immunology
  • Polymerase Chain Reaction
  • Protein Serine-Threonine Kinases
  • RNA, Bacterial / metabolism*
  • RNA, Small Interfering
  • Receptors, Pattern Recognition
  • Signal Transduction / immunology
  • Streptococcus pyogenes / genetics
  • Streptococcus pyogenes / immunology*

Substances

  • DNA, Bacterial
  • Interferon Regulatory Factor-3
  • Interferon Regulatory Factors
  • Irf5 protein, mouse
  • Membrane Proteins
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • RNA, Bacterial
  • RNA, Small Interfering
  • Receptors, Pattern Recognition
  • Sting1 protein, mouse
  • Interferon-beta
  • Tbk1 protein, mouse
  • Protein Serine-Threonine Kinases