The interferon response to bacterial and viral infections.
Type I interferons (IFNs) were first described several decades ago as soluble factors that were capable of 'interfering' with viral replication when added to infected cells. Type I IFNs have been shown to be induced by recognition of viral DNA and RNA via three distinct pathways: (i) a TRIF-dependent pathway in macrophages via TLRs 3 and 4; (ii) a MyD88-dependent pathway in plasmacytoid dendritic cells (pDCs) via TLRs 7/8 and 9; and (iii) an intracellular recognition pathway utilizing the cytoplasmic receptors RIG-I/MDA5. Interestingly, these viral recognition pathways converge on TRAF3, which induces interferon through the activation of IRF3 or IRF7 by the TBK-1 and IKKi complexes. While type I IFN has been traditionally associated with antiviral responses, recent studies have demonstrated that many bacteria also induce type I interferon responses. The mechanisms of type I IFN induction and its role in host defense, however, are largely unclear. Studies with the Gram-positive intracellular bacterium Listeria monocytogenes indicated that it may trigger type I IFN induction through novel TLR-independent intracellular receptors and type I IFN may play a detrimental role to host response against listerial infection. In this article, we summarize some of these findings and discuss the functional differences of type I IFNs in bacterial and viral infections.
Pietras
Eric M
EM
Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, 90095, USA.
Saha
Supriya K
SK
Cheng
Genhong
G
D000818:Animals; D001419:Bacteria / Q000276:immunology*; D001424:Bacterial Infections / Q000276:immunology* / Q000503:physiopathology; D006801:Humans; D007370:Interferon Type I / Q000276:immunology*; D008089:Listeria monocytogenes / Q000276:immunology; D015398:Signal Transduction; D048008:TNF Receptor-Associated Factor 3; D051193:Toll-Like Receptors / Q000276:immunology; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000276:immunology / Q000378:metabolism; D014777:Virus Diseases / Q000276:immunology* / Q000503:physiopathology; D014780:Viruses / Q000276:immunology*
D007370:Interferon Type I; D048008:TNF Receptor-Associated Factor 3; C090656:TRAF3 protein, human; D051193:Toll-Like Receptors; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins