Interferon Regulatory Factor IRF-7 Induces the Antiviral Alpha Interferon Response and Protects against Lethal West Nile Virus Infection

Daffis, Stéphane; Samuel, Melanie A.; Suthar, Mehul S.; Keller, Brian C.; Gale, Michael; Diamond, Michael S.

doi:10.1128/jvi.00918-08

Cited by 145 publications

(198 citation statements)

References 50 publications

(82 reference statements)

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“…However, the control of innate immune signaling varies according to tissue and virus (72)(73)(74)(75). Increased susceptibility of IRF-7-deficient mice to viruses such as West Nile virus, Chikungunya virus, and SINV demonstrates the central importance of IRF-7 in orchestrating IFN signaling (44,47,(76)(77)(78). Noncanonically, IRF-1, -3, and -7 can upregulate ISG expression in the absence of measurable IFN (48,(79)(80)(81)(82).…”

Section: Figmentioning

confidence: 99%

Differentiation of Neurons Restricts Arbovirus Replication and Increases Expression of the Alpha Isoform of IRF-7

Schultz

Vernon

Griffin

2015

J Virol

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Susceptibility to alphavirus infection is age dependent, and host maturation is associated with decreased virus replication and less severe encephalitis. To identify factors associated with maturation-dependent restriction of virus replication, we studied AP-7 rat olfactory bulb neuronal cells, which can differentiate in vitro. Differentiation was associated with a 150-to 1,000-fold decrease in replication of the alphaviruses Sindbis virus and Venezuelan equine encephalitis virus, as well as La Crosse bunyavirus. Differentiation delayed synthesis of SINV RNA and protein but did not alter the susceptibility of neurons to infection or virion maturation. Additionally, differentiation slowed virus-induced translation arrest and death of infected cells. Differentiation of uninfected AP-7 neurons was associated with changes in expression of antiviral genes. Expression of key transcription factors was increased, including interferon regulatory factor 3 and 7 (IRF-3 and IRF-7) and STAT-1, suggesting that neuronal maturation may enhance the capacity for antiviral signaling upon infection. IRF-7 produced by undifferentiated AP-7 neurons was exclusively the short dominant negative ␥-isoform, while that produced by differentiated neurons was the full-length ␣-isoform. A similar switch in IRF-7 isoforms also occurred in the brains of maturing C57BL/6J mice. Silencing of IRF expression did not improve virus multiplication in differentiated neurons. Therefore, neuronal differentiation is associated with upregulation of transcription factors that activate antiviral signaling, but this alone does not account for maturation-dependent restriction of virus replication. IMPORTANCEViral encephalomyelitis is an important cause of age-dependent morbidity and mortality. Because mature neurons are not readily regenerated, recovery from encephalitis suggests that mature neurons utilize unique antiviral mechanisms to block infection and/or clear virus. To identify maturational changes in neurons that may improve outcome, we compared immature and mature cultured neurons for susceptibility to three encephalitic arboviruses and found that replication of Old World and New World alphaviruses and a bunyavirus was reduced in mature compared to immature neurons. Neuronal maturation was associated with increased baseline expression of interferon regulatory factor 3 and 7 mRNAs and production of distinct isoforms of interferon regulatory factor 7 protein. Overall, our studies identified maturational changes in neurons that likely contribute to assembly of immunoregulatory factors prior to infection, a more rapid antiviral response, increased resistance to virus infection, and improved survival. Development of age-dependent resistance to fatal disease is a characteristic of many virus infections of the central nervous system (CNS) (1-9). We have used Sindbis virus (SINV), the prototype alphavirus in the family Togaviridae, as a model system to understand maturation-mediated restriction of virus multiplication in neurons. SINV preferentially i...

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Section: Figmentioning

confidence: 99%

Differentiation of Neurons Restricts Arbovirus Replication and Increases Expression of the Alpha Isoform of IRF-7

Schultz

Vernon

Griffin

2015

J Virol

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“…Therefore, Dcp2 could modulate a broad antiviral immune response by, at least in part, targeting a critical upstream transcription factor. IRF-7 is an important regulator of antiviral immunity, and an IRF-7 deficiency in mice results in increased susceptibility to viral infection and lethality in addition to a blunted systemic type I IFN response (7). Conversely, mice with a disrupted gene encoding the translational repressor 4E-BP and an increase in IRF-7 levels are highly resistant to infection by a variety of viruses (6).…”

Section: In Dcp2mentioning

confidence: 99%

Dcp2 Decapping Protein Modulates mRNA Stability of the Critical Interferon Regulatory Factor (IRF) IRF-7

Dai

Song

et al. 2012

Molecular and Cellular Biology

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bThe mammalian Dcp2 mRNA-decapping protein functions primarily on a subset of mRNAs in a transcript-specific manner. Here we show that Dcp2 is an important modulator of genes involved in the type I interferon (IFN) response, which is the initial line of antiviral innate immune response elicited by a viral challenge. Mouse embryonic fibroblast cells with reduced Dcp2 levels (Dcp2 ␤/␤ ) contained significantly elevated levels of mRNAs encoding proteins involved in the type I IFN response. In particular, analysis of a key type I IFN transcription factor, IFN regulatory factor 7 (IRF-7), revealed an increase in both IRF-7 mRNA and protein in Dcp2 ␤/␤ cells. Importantly, the increase in IRF-7 mRNA within the background of reduced Dcp2 levels was attributed to a stabilization of the IRF-7 mRNA, suggesting that Dcp2 normally modulates IRF-7 mRNA stability. Moreover, Dcp2 expression was also induced upon viral infection, consistent with a role in attenuating the antiviral response by promoting IRF-7 mRNA degradation. The induction of Dcp2 levels following a viral challenge and the specificity of Dcp2 in targeting the decay of IRF-7 mRNA suggest that Dcp2 may negatively contribute to the innate immune response in a negative feedback mechanism to restore normal homeostasis following viral infection.

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“…For example, mice with deficiencies in the induction of type I IFNs and the receptor or JAK-STAT signal transduction pathway of the cytokines are vulnerable to WNV and DENV infections (7,38,42,(49)(50)(51). In addition, a strain of WNV that fails to block the type I IFN signal transduction pathway is phenotypically attenuated in mice (23,50).…”

mentioning

confidence: 99%

Identification of Five Interferon-Induced Cellular Proteins That Inhibit West Nile Virus and Dengue Virus Infections

Jiang

Weidner

Qing

et al. 2010

J Virol

301

344

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Interferons (IFNs) are key mediators of the host innate antiviral immune response. To identify IFNstimulated genes (ISGs) that instigate an antiviral state against two medically important flaviviruses, West Nile virus (WNV) and dengue virus (DENV), we tested 36 ISGs that are commonly induced by IFN-␣ for antiviral activity against the two viruses. We discovered that five ISGs efficiently suppressed WNV and/or DENV infection when they were individually expressed in HEK293 cells. Mechanistic analyses revealed that two structurally related cell plasma membrane proteins, IFITM2 and IFITM3, disrupted early steps (entry and/or uncoating) of the viral infection. In contrast, three IFN-induced cellular enzymes, viperin, ISG20, and double-stranded-RNA-activated protein kinase, inhibited steps in viral proteins and/or RNA biosynthesis. Our results thus imply that the antiviral activity of IFN-␣ is collectively mediated by a panel of ISGs that disrupt multiple steps of the DENV and WNV life cycles.West Nile virus (WNV) and dengue virus (DENV) are mosquito-borne flaviviruses that cause invasive neurological diseases and lethal hemorrhagic fever in humans, respectively (6, 32). Since its first incursion into New York City in 1999, WNV has rapidly spread throughout the continental United States and has recently reached South America (29, 34). In most cases, WNV infection of people resolves as an asymptomatic or a mild febrile illness. However, approximately 1% of infections result in severe neurological disorders, such as encephalitis and meningitis (27). Unlike WNV, for which people are only accidental hosts, DENV has fully adapted to humans (32). It has apparently lost the need for an enzootic cycle and causes a range of diseases in people, from acute febrile illness to life-threatening dengue hemorrhagic fever/dengue shock syndrome (6). Four distinct serotypes of DENV have spread throughout the tropical and subtropical parts of the world, with an estimated 50 to 100 million human cases annually and about 2.5 billion people worldwide being at risk of infection (32). Effective antiviral therapies and vaccines to treat or prevent WNV and DENV infections in humans are not yet available.Type I interferons (IFNs), represented by IFN-␣ and IFN-␤, have been demonstrated to play an essential role in defending against WNV and DENV infections. For example, mice with deficiencies in the induction of type I IFNs and the receptor or JAK-STAT signal transduction pathway of the cytokines are vulnerable to WNV and DENV infections (7,38,42,(49)(50)(51). In addition, a strain of WNV that fails to block the type I IFN signal transduction pathway is phenotypically attenuated in mice (23,50). Clinically, during acute DENV infection, innate immune responses play a key role in determining disease outcome (35), and resolution of WNV infection requires effective IFN-mediated innate host responses (23,43,53). Therefore, understanding how the IFN-mediated innate immune response functions is one of the critical frontiers in the molecular biology of WN...

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Interferon Regulatory Factor IRF-7 Induces the Antiviral Alpha Interferon Response and Protects against Lethal West Nile Virus Infection

Cited by 145 publications

References 50 publications

Differentiation of Neurons Restricts Arbovirus Replication and Increases Expression of the Alpha Isoform of IRF-7

Differentiation of Neurons Restricts Arbovirus Replication and Increases Expression of the Alpha Isoform of IRF-7

Dcp2 Decapping Protein Modulates mRNA Stability of the Critical Interferon Regulatory Factor (IRF) IRF-7

Identification of Five Interferon-Induced Cellular Proteins That Inhibit West Nile Virus and Dengue Virus Infections

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