Induction of IFN-beta and the innate antiviral response in myeloid cells occurs through an IPS-1-dependent signal that does not require IRF-3 and IRF-7.
Interferon regulatory factors (IRF)-3 and IRF-7 are master transcriptional factors that regulate type I IFN gene (IFN-alpha/beta) induction and innate immune defenses after virus infection. Prior studies in mice with single deletions of the IRF-3 or IRF-7 genes showed increased vulnerability to West Nile virus (WNV) infection. Whereas mice and cells lacking IRF-7 showed reduced IFN-alpha levels after WNV infection, those lacking IRF-3 or IRF-7 had relatively normal IFN-b production. Here, we generated IRF-3(-/-)x IRF-7(-/-) double knockout (DKO) mice, analyzed WNV pathogenesis, IFN responses, and signaling of innate defenses. Compared to wild type mice, the DKO mice exhibited a blunted but not abrogated systemic IFN response and sustained uncontrolled WNV replication leading to rapid mortality. Ex vivo analysis showed complete ablation of the IFN-alpha response in DKO fibroblasts, macrophages, dendritic cells, and cortical neurons and a substantial decrease of the IFN-beta response in DKO fibroblasts and cortical neurons. In contrast, the IFN-beta response was minimally diminished in DKO macrophages and dendritic cells. However, pharmacological inhibition of NF-kappaB and ATF-2/c-Jun, the two other known components of the IFN-beta enhanceosome, strongly reduced IFN-beta gene transcription in the DKO dendritic cells. Finally, a genetic deficiency of IPS-1, an adaptor involved in RIG-I- and MDA5-mediated antiviral signaling, completely abolished the IFN-beta response after WNV infection. Overall, our experiments suggest that, unlike fibroblasts and cortical neurons, IFN-beta gene regulation after WNV infection in myeloid cells is IPS-1-dependent but does not require full occupancy of the IFN-beta enhanceosome by canonical constituent transcriptional factors.
Daffis
Stephane
S
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Suthar
Mehul S
MS
Szretter
Kristy J
KJ
Gale
Michael
M
Diamond
Michael S
MS
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000276:immunology; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000276:immunology / Q000821:virology; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000276:immunology*; D007113:Immunity, Innate; D050838:Interferon Regulatory Factor-3 / Q000235:genetics / Q000276:immunology; D050839:Interferon Regulatory Factor-7 / Q000235:genetics / Q000276:immunology; D016899:Interferon-beta / Q000096:biosynthesis* / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000821:virology*; D009474:Neurons / Q000276:immunology / Q000821:virology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014779:Virus Replication / Q000502:physiology; D014901:West Nile Fever / Q000235:genetics* / Q000276:immunology; D014902:West Nile virus / Q000276:immunology
D048868:Adaptor Proteins, Signal Transducing; D050838:Interferon Regulatory Factor-3; D050839:Interferon Regulatory Factor-7; D016899:Interferon-beta; C512612:MAVS protein, mouse