MyD88 and STING signaling pathways are required for IRF3-mediated IFN-β induction in response to Brucella abortus infection

PLoS One. 2011;6(8):e23135. doi: 10.1371/journal.pone.0023135. Epub 2011 Aug 2.

Abstract

Type I interferons (IFNs) are cytokines that orchestrate diverse immune responses to viral and bacterial infections. Although typically considered to be most important molecules in response to viruses, type I IFNs are also induced by most, if not all, bacterial pathogens. In this study, we addressed the role of type I IFN signaling during Brucella abortus infection, a facultative intracellular bacterial pathogen that causes abortion in domestic animals and undulant fever in humans. Herein, we have shown that B. abortus induced IFN-β in macrophages and splenocytes. Further, IFN-β induction by Brucella was mediated by IRF3 signaling pathway and activates IFN-stimulated genes via STAT1 phosphorylation. In addition, IFN-β expression induced by Brucella is independent of TLRs and TRIF signaling but MyD88-dependent, a pathway not yet described for Gram-negative bacteria. Furthermore, we have identified Brucella DNA as the major bacterial component to induce IFN-β and our study revealed that this molecule operates through a mechanism dependent on RNA polymerase III to be sensed probably by an unknown receptor via the adaptor molecule STING. Finally, we have demonstrated that IFN-αβR KO mice are more resistant to infection suggesting that type I IFN signaling is detrimental to host control of Brucella. This resistance phenotype is accompanied by increased IFN-γ and NO production by IFN-αβR KO spleen cells and reduced apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brucella abortus / genetics
  • Brucella abortus / isolation & purification*
  • Brucellosis / metabolism*
  • Brucellosis / microbiology
  • Cell Line
  • DNA, Bacterial / genetics
  • Interferon Regulatory Factor-3 / physiology*
  • Interferon-beta / biosynthesis*
  • Macrophages / metabolism
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Myeloid Differentiation Factor 88 / metabolism*
  • Phosphorylation
  • RNA Polymerase III / metabolism
  • STAT1 Transcription Factor / metabolism
  • Spleen / cytology
  • Spleen / metabolism
  • TNF-Related Apoptosis-Inducing Ligand / metabolism

Substances

  • DNA, Bacterial
  • Interferon Regulatory Factor-3
  • Irf3 protein, mouse
  • Membrane Proteins
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • STAT1 Transcription Factor
  • Stat1 protein, mouse
  • Sting1 protein, mouse
  • TNF-Related Apoptosis-Inducing Ligand
  • Tnfsf10 protein, mouse
  • Interferon-beta
  • RNA Polymerase III