211 research outputs found
Interferon regulatory factor-1 (irf-1) shapes both innate and cd8 + t cell immune responses against west nile virus infection
Interferon regulatory factor (IRF)-1 is an immunomodulatory transcription factor that functions downstream of pathogen recognition receptor signaling and has been implicated as a regulator of type I interferon (IFN)-Ξ±Ξ² expression and the immune response to virus infections. However, this role for IRF-1 remains controversial because altered type I IFN responses have not been systemically observed in IRF-1 -/- mice. To evaluate the relationship of IRF-1 and immune regulation, we assessed West Nile virus (WNV) infectivity and the host response in IRF-1 -/- cells and mice. IRF-1 -/- mice were highly vulnerable to WNV infection with enhanced viral replication in peripheral tissues and rapid dissemination into the central nervous system. Ex vivo analysis revealed a cell-type specific antiviral role as IRF-1 -/- macrophages supported enhanced WNV replication but infection was unaltered in IRF-1 -/- fibroblasts. IRF-1 also had an independent and paradoxical effect on CD8 + T cell expansion. Although markedly fewer CD8 + T cells were observed in naΓ―ve animals as described previously, remarkably, IRF-1 -/- mice rapidly expanded their pool of WNV-specific cytolytic CD8 + T cells. Adoptive transfer and in vitro proliferation experiments established both cell-intrinsic and cell-extrinsic effects of IRF-1 on the expansion of CD8 + T cells. Thus, IRF-1 restricts WNV infection by modulating the expression of innate antiviral effector molecules while shaping the antigen-specific CD8 + T cell response
Cell-Specific IRF-3 Responses Protect against West Nile Virus Infection by Interferon-Dependent and -Independent Mechanisms
Interferon regulatory factor (IRF)-3 is a master transcription factor that activates host antiviral defense programs. Although cell culture studies suggest that IRF-3 promotes antiviral control by inducing interferon (IFN)-Ξ², near normal levels of IFN-Ξ± and IFN-Ξ² were observed in IRF-3β/β mice after infection by several RNA and DNA viruses. Thus, the specific mechanisms by which IRF-3 modulates viral infection remain controversial. Some of this disparity could reflect direct IRF-3-dependent antiviral responses in specific cell types to control infection. To address this and determine how IRF-3 coordinates an antiviral response, we infected IRF-3β/β mice and two primary cells relevant for West Nile virus (WNV) pathogenesis, macrophages and cortical neurons. IRF-3β/β mice were uniformly vulnerable to infection and developed elevated WNV burdens in peripheral and central nervous system tissues, though peripheral IFN responses were largely normal. Whereas wild-type macrophages basally expressed key host defense molecules, including RIG-I, MDA5, ISG54, and ISG56, and restricted WNV infection, IRF-3β/β macrophages lacked basal expression of these host defense genes and supported increased WNV infection and IFN-Ξ± and IFN-Ξ² production. In contrast, wild-type cortical neurons were highly permissive to WNV and did not basally express RIG-I, MDA5, ISG54, and ISG56. IRF-3β/β neurons lacked induction of host defense genes and had blunted IFN-Ξ± and IFN-Ξ² production, yet exhibited only modestly increased viral titers. Collectively, our data suggest that cell-specific IRF-3 responses protect against WNV infection through both IFN-dependent and -independent programs
IPS-1 Is Essential for the Control of West Nile Virus Infection and Immunity
The innate immune response is essential for controlling West Nile virus (WNV) infection but how this response is propagated and regulates adaptive immunity in vivo are not defined. Herein, we show that IPS-1, the central adaptor protein to RIG-I-like receptor (RLR) signaling, is essential for triggering of innate immunity and for effective development and regulation of adaptive immunity against pathogenic WNV. IPS-1β/β mice exhibited increased susceptibility to WNV infection marked by enhanced viral replication and dissemination with early viral entry into the CNS. Infection of cultured bone-marrow (BM) derived dendritic cells (DCs), macrophages (Macs), and primary cortical neurons showed that the IPS-1-dependent RLR signaling was essential for triggering IFN defenses and controlling virus replication in these key target cells of infection. Intriguingly, infected IPS-1β/β mice displayed uncontrolled inflammation that included elevated systemic type I IFN, proinflammatory cytokine and chemokine responses, increased numbers of inflammatory DCs, enhanced humoral responses marked by complete loss of virus neutralization activity, and increased numbers of virus-specific CD8+ T cells and non-specific immune cell proliferation in the periphery and in the CNS. This uncontrolled inflammatory response was associated with a lack of regulatory T cell expansion that normally occurs during acute WNV infection. Thus, the enhanced inflammatory response in the absence of IPS-1 was coupled with a failure to protect against WNV infection. Our data define an innate/adaptive immune interface mediated through IPS-1-dependent RLR signaling that regulates the quantity, quality, and balance of the immune response to WNV infection
Interferon Regulatory Factor-1 (IRF-1) Shapes Both Innate and CD8+ T Cell Immune Responses against West Nile Virus Infection
Interferon regulatory factor (IRF)-1 is an immunomodulatory transcription factor that functions downstream of pathogen recognition receptor signaling and has been implicated as a regulator of type I interferon (IFN)-Ξ±Ξ² expression and the immune response to virus infections. However, this role for IRF-1 remains controversial because altered type I IFN responses have not been systemically observed in IRF-1-/- mice. To evaluate the relationship of IRF-1 and immune regulation, we assessed West Nile virus (WNV) infectivity and the host response in IRF-1-/- cells and mice. IRF-1-/- mice were highly vulnerable to WNV infection with enhanced viral replication in peripheral tissues and rapid dissemination into the central nervous system. Ex vivo analysis revealed a cell-type specific antiviral role as IRF-1-/- macrophages supported enhanced WNV replication but infection was unaltered in IRF-1-/- fibroblasts. IRF-1 also had an independent and paradoxical effect on CD8+ T cell expansion. Although markedly fewer CD8+ T cells were observed in naΓ―ve animals as described previously, remarkably, IRF-1-/- mice rapidly expanded their pool of WNV-specific cytolytic CD8+ T cells. Adoptive transfer and in vitro proliferation experiments established both cell-intrinsic and cell-extrinsic effects of IRF-1 on the expansion of CD8+ T cells. Thus, IRF-1 restricts WNV infection by modulating the expression of innate antiviral effector molecules while shaping the antigen-specific CD8+ T cell response
Therapeutic potential of TLR8 agonist GS-9688 (selgantolimod) in chronic hepatitis B: re-modelling of antiviral and regulatory mediators
Background & Aims:
GSβ9688 (selgantolimod) is a tollβlike receptor 8 (TLR8) agonist in clinical development for the treatment of chronic hepatitis B (CHB). Antiviral activity of GSβ9688 has previously been evaluated in vitro in hepatitis B virus (HBV)βinfected hepatocytes and in vivo in the woodchuck model of CHB. Here we evaluated the potential of GSβ9688 to boost responses contributing to viral control and to modulate regulatory mediators.
Approach & Results:
We characterised the effect of GSβ9688 on immune cell subsets in vitro in PBMC of healthy controls and CHB patients. GSβ9688 activated dendritic cells and mononuclear phagocytes to produce ILβ12 and other immunomodulatory mediators, inducing a comparable cytokine profile in healthy controls and CHB patients. GSβ9688 increased the frequency of activated natural killer (NK) cells, mucosalβassociated invariant Tβcells (MAITs), CD4+ follicular helper Tβcells (TFH) and, in ~50% of patients, HBVβspecific CD8+Tβcells expressing interferonβΞ³ (IFNΞ³). Moreover, in vitro stimulation with GSβ9688 induced NK cell expression of IFNΞ³ and TNFΞ± and promoted hepatocyte lysis. We also assessed whether GSβ9688 inhibited immunosuppressive cell subsets that might enhance antiviral efficacy. Stimulation with GSβ9688 reduced the frequency of CD4+ regulatory Tβcells and monocytic myeloidβderived suppressor cells (MDSC). Residual MDSC expressed higher levels of negative immune regulators, galectinβ9 and PDβL1. Conversely, GSβ9688 induced an expansion of immunoregulatory TNFβrelated apoptosisβinducing ligand+ (TRAIL) regulatory NK cells and degranulation of arginaseβI+ polymorphonuclearβMDSC (PMNβMDSC).
Conclusions:
GSβ9688 induces cytokines in human PBMC that are able to activate antiviral effector function by multiple immune mediators (HBVβspecific CD8+Tβcells, TFH, NK cells and MAITs). Whilst reducing the frequency of some immunoregulatory subsets, it enhances the immunosuppressive potential of others, highlighting potential biomarkers and immunotherapeutic targets to optimise the antiviral efficacy of GSβ9688
2β²-O Methylation of the Viral mRNA Cap by West Nile Virus Evades Ifit1-Dependent and -Independent Mechanisms of Host Restriction In Vivo
Prior studies have shown that 2β²-O methyltransferase activity of flaviviruses, coronaviruses, and poxviruses promotes viral evasion of Ifit1, an interferon-stimulated innate immune effector protein. Viruses lacking 2β²-O methyltransferase activity exhibited attenuation in primary macrophages that was rescued in cells lacking Ifit1 gene expression. Here, we examined the role of Ifit1 in restricting pathogenesis in vivo of wild type WNV (WNV-WT) and a mutant in the NS5 gene (WNV-E218A) lacking 2β²-O methylation of the 5β² viral RNA cap. While deletion of Ifit1 had marginal effects on WNV-WT pathogenesis, WNV-E218A showed increased replication in peripheral tissues of Ifit1β/β mice after subcutaneous infection, yet this failed to correlate with enhanced infection in the brain or lethality. In comparison, WNV-E218A was virulent after intracranial infection as judged by increased infection in different regions of the central nervous system (CNS) and a greater than 16,000-fold decrease in LD50 values in Ifit1β/β compared to wild type mice. Ex vivo infection experiments revealed cell-type specific differences in the ability of an Ifit1 deficiency to complement the replication defect of WNV-E218A. In particular, WNV-E218A infection was impaired in both wild type and Ifit1β/β brain microvascular endothelial cells, which are believed to participate in blood-brain barrier (BBB) regulation of virus entry into the CNS. A deficiency of Ifit1 also was associated with increased neuronal death in vivo, which was both cell-intrinsic and mediated by immunopathogenic CD8+ T cells. Our results suggest that virulent strains of WNV have largely evaded the antiviral effects of Ifit1, and viral mutants lacking 2β²-O methylation are controlled in vivo by Ifit1-dependent and -independent mechanisms in different cell types
Induction of IFN-Ξ² 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-Ξ±/Ξ²) 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-Ξ± levels after WNV infection, those lacking IRF-3 or IRF-7 had relatively normal IFN-b production. Here, we generated IRF-3β/βΓ IRF-7β/β 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-Ξ± response in DKO fibroblasts, macrophages, dendritic cells, and cortical neurons and a substantial decrease of the IFN-Ξ² response in DKO fibroblasts and cortical neurons. In contrast, the IFN-Ξ² response was minimally diminished in DKO macrophages and dendritic cells. However, pharmacological inhibition of NF-ΞΊB and ATF-2/c-Jun, the two other known components of the IFN-Ξ² enhanceosome, strongly reduced IFN-Ξ² 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-Ξ² response after WNV infection. Overall, our experiments suggest that, unlike fibroblasts and cortical neurons, IFN-Ξ² gene regulation after WNV infection in myeloid cells is IPS-1-dependent but does not require full occupancy of the IFN-Ξ² enhanceosome by canonical constituent transcriptional factors
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Ribose 2β²-O-methylation provides a molecular signature for the distinction of self and non-self mRNA dependent on the RNA sensor Mda5
The 5'-cap-structures of higher eukaryote mRNAs are ribose 2'-O-methylated. Likewise, a number of viruses replicating in the cytoplasm of eukayotes have evolved 2'-O-methyltransferases to modify autonomously their mRNAs. However, a defined biological role of mRNA 2'-O-methylation remains elusive. Here we show that viral mRNA 2'-O-methylation is critically involved in subversion of type-I-interferon (IFN-I) induction. We demonstrate that human and murine coronavirus 2'-O-methyltransferase mutants induce increased IFN-I expression, and are highly IFN-I sensitive. Importantly, IFN-I induction by 2'-O-methyltransferase-deficient viruses is dependent on the cytoplasmic RNA sensor melanoma differentiation-associated gene 5 (MDA5). This link between MDA5-mediated sensing of viral RNA and mRNA 2'-O-methylation suggests that RNA modifications, such as 2'-O-methylation, provide a molecular signature for the discrimination of self and non-self mRNA
IL-10 Signaling Blockade Controls Murine West Nile Virus Infection
West Nile virus (WNV), a mosquito-borne single-stranded RNA flavivirus, can cause significant human morbidity and mortality. Our data show that interleukin-10 (IL-10) is dramatically elevated both in vitro and in vivo following WNV infection. Consistent with an etiologic role of IL-10 in WNV pathogenesis, we find that WNV infection is markedly diminished in IL-10 deficient (IL-10β/β) mice, and pharmacologic blockade of IL-10 signaling by IL-10 neutralizing antibody increases survival of WNV-infected mice. Increased production of antiviral cytokines in IL-10β/β mice is associated with more efficient control of WNV infection. Moreover, CD4+ T cells produce copious amounts of IL-10, and may be an important cellular source of IL-10 during WNV infection in vivo. In conclusion, IL-10 signaling plays a negative role in immunity against WNV infection, and blockade of IL-10 signaling by genetic or pharmacologic means helps to control viral infection, suggesting a novel anti-WNV therapeutic strategy
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