IFNAR1-deficient Mice Research Articles

IFN-I promotes T cell-independent immunity and RBC autoantibodies via modulation of B-1 cell subsets in murine SCD.

The pathophysiology of sickle cell disease (SCD) is characterized by hemolytic anemia and vaso-occlusion, although its impact on the adaptive immune responses remains incompletely understood. To comprehensibly profile the humoral immune responses, we immunized SCD mice with T cell-independent (TI) and T cell-dependent (TD) antigens. Our study showed that SCD mice have significantly enhanced type 2 TI (TI-2) immune responses in a manner dependent on the level of type I IFN (IFN-I), while maintaining similar or decreased TD immune responses depending on the route of antigen administration. Consistent with the enhanced TI-2 immune responses in SCD mice, the frequencies of B-1b cells (B-1 cells in humans), a major cell type responding to TI-2 antigens, were significantly increased in both the peritoneal cavity and spleens of SCD mice and in blood of patients with SCD. In support of expanded B-1 cells, elevated levels of anti-red blood cell (RBC) autoantibodies were detected in both SCD mice and patients. Both the levels of TI-2 immune responses and anti-RBC autoantibodies were significantly reduced following IFNAR antibody blockades and in IFNAR-1 deficient SCD mice. Moreover, the alteration of B-1 cell subsets were reversed in IFNAR-1 deficient SCD mice, uncovering a critical role for IFN-I in the enhanced TI-2 immune responses and the increased production of anti-RBC autoantibodies by modulating the innate B-1 cell subsets in SCD. Overall, our study provides experimental evidence that the modulation of B-1 cells and IFN-I can regulate TI immune responses and the levels of anti-RBC autoantibodies in SCD.

Targeting mechanistic target of rapamycin complex 2 attenuates immunopathology in Systemic Lupus Erythematosus.

We aim to explore the role of mechanistic target of rapamycin complex (mTORC) 2 in systemic lupus erythematosus (SLE) development, the in vivo regulation of mTORC2 by type I interferon (IFN) signaling in autoimmunity, and to use mTORC2 targeting therapy to ameliorate lupus-like symptoms in an in vivo lupus mouse model and an in vitro coculture model using human PBMCs. We first induced lupus-like disease in T cell specific Rictor, a key component of mTORC2, deficient mice by topical application of imiquimod (IMQ) and monitored disease development. Next, we investigated the changes of mTORC2 signaling and immunological phenotypes in type I IFNAR deficient Lpr mice. We then tested the beneficial effects of anti-Rictor antisense oligonucleotide (Rictor-ASO) in a mouse model of lupus: MRL/lpr mice. Finally, we examined the beneficial effects of RICTOR-ASO on SLE patients' PBMCs using an in vitro T-B cell coculture assay. T cell specific Rictor deficient mice have reduced age-associated B cells, plasma cells and germinal center B cells, and less autoantibody production than WT mice following IMQ treatment. IFNAR1 deficient Lpr mice have reduced mTORC2 activity in CD4+ T cells accompanied by restored CD4+ T cell glucose metabolism, partially recovered T cell trafficking, and reduced systemic inflammation. In vivo Rictor-ASO treatment improves renal function and pathology in MRL/lpr mice, along with improved immunopathology. In human SLE (N = 5) PBMCs derived T-B coculture assay, RICTOR-ASO significantly reduce immunoglobulin and autoantibodies production (P < 0.05). Targeting mTORC2 could be a promising therapeutic for SLE.

Differential roles of type I interferon signaling in tumor versus host cells in experimental glioma models

Despite multimodal treatment approaches including surgery, radiotherapy and chemotherapy, the median survival for patients with glioblastoma remains in the range of one year and thus poor. Type I interferons (IFN) are involved in immune responses to viral infection and exhibit anti-tumor activity in certain cancers.Here we explored the biological relevance of constitutive type I IFN signaling in murine glioma models in vitro and in vivo. CT-2A, GL-261, SMA-497, SMA-540 and SMA-560 murine glioma cells expressed IFN type I receptors IFNAR1 and IFNAR2 and were responsive to exogenous IFN stimulation. CRISPR/Cas9-mediated deletion of IFNAR1 decreased the baseline expression of type I IFN response genes in GL-261 cells, but neither in CT-2A nor in SMA-560 cells. IFNAR1 deletion slowed growth in GL-261 and SMA-560, but not in CT-2A cells. However, only the growth of IFNAR1-depleted GL-261 tumors and not that of SMA-560 tumors was delayed in vivo upon orthotopic tumor cell implantation into syngeneic mice. This survival gain was no longer detected when the IFNAR1-depleted GL-261 cells were inoculated into IFNAR1-deficient mice. Altogether these data suggest that constitutive type I IFN signaling in gliomas may be pro-tumorigenic, but only in a microenvironment that is proficient for type I IFN signaling in the host.

Type I Interferon Receptor Subunit 1 Deletion Attenuates Experimental Abdominal Aortic Aneurysm Formation.

Objective: Type I interferon receptor signaling contributes to several autoimmune and vascular diseases such as lupus, atherosclerosis and stroke. The purpose of this study was to assess the influence of type I interferon receptor deficiency on the formation and progression of experimental abdominal aortic aneurysms (AAAs). Methods: AAAs were induced in type I interferon receptor subunit 1 (IFNAR1)-deficient and wild type control male mice via intra-infrarenal aortic infusion of porcine pancreatic elastase. Immunostaining for IFNAR1 was evaluated in experimental and clinical aneurysmal abdominal aortae. The initiation and progression of experimental AAAs were assessed via ultrasound imaging prior to (day 0) and days 3, 7 and 14 following elastase infusion. Aneurysmal histopathology was analyzed at sacrifice. Results: Increased aortic medial and adventitial IFNAR1 expression was present in both clinical AAAs harvested at surgery and experimental AAAs. Following AAA induction, wild type mice experienced progressive, time-dependent infrarenal aortic enlargement. This progression was substantially attenuated in IFNAR1-deficient mice. On histological analyses, medial elastin degradation, smooth muscle cell depletion, leukocyte accumulation and neoangiogenesis were markedly diminished in IFNAR1-deficient mice in comparison to wild type mice. Conclusion: IFNAR1 deficiency limited experimental AAA progression in response to intra-aortic elastase infusion. Combined with clinical observations, these results suggest an important role for IFNAR1 activity in AAA pathogenesis.

Role of type l IFN in lacrimal gland-protective Treg dysfunction in nonobese diabetic mouse model of Sjögren’s disease

Abstract Sjogren’s disease is a chronic autoimmune disease of the lacrimal and salivary glands characterized by foci of inflammation in the tissue composed of aggregations of lymphocytes. Male non-obese diabetic (NOD) mice spontaneously develop autoimmunity of the lacrimal glands. Tregs from these mice are dysfunctional. Disruption of the type I interferon (IFN) signaling pathway protects NOD mice from developing lacrimal gland disease. Whether type l IFN signaling drives lacrimal gland protective Treg dysfunction is not known. Here we investigated the role of type l IFN in modulating Treg phenotype and function. Through adoptive transfer studies comparing cells from wild-type or IFNAR1-deficient donor mice, we found that recipients of IFNAR1-deficient cells had fewer foci of inflammation. IFNAR1 expression was correlated with a population of CD44loCD62Lhi Tregs. Co-adoptive transfer of both WT and IFNAR1-deficient cells determined that this altered Treg phenotype was due to intrinsic type l IFN signaling. In vitro studies suggest that Treg phenotype can be shaped by IFNα in a dose dependent manner. Ongoing in vivo studies will interrogate the impact of IFNAR1 expression on Treg function. Type l IFN signaling plays a role in shaping Treg phenotype and may antagonize Treg function. These studies will help define the role of type l IFN signaling in early pathogenesis of Sjögren’s disease and may provide insight into other systemic autoimmune diseases. Supported by grants from NIH (R01EY027731-01A1)

Type I interferon limits mast cell-mediated anaphylaxis by controlling secretory granule homeostasis.

Type I interferon (IFN-I) is a family of multifunctional cytokines that modulate the innate and adaptive immunity and are used to treat mastocytosis. Although IFN-I is known to suppress mast cell function, including histamine release, the mechanisms behind its effects on mast cells have been poorly understood. We here investigated IFN-I’s action on mast cells using interferon-α/β receptor subunit 1 (Ifnar1)-deficient mice, which lack a functional IFN-I receptor complex, and revealed that IFN-I in the steady state is critical for mast cell homeostasis, the disruption of which is centrally involved in systemic anaphylaxis. Ifnar1-deficient mice showed exacerbated systemic anaphylaxis after sensitization, which was associated with increased histamine in the circulation, even though the mast cell numbers and high affinity immunoglobulin E receptor (FcεRI) expression levels were similar between Ifnar1-deficient and wild-type (WT) mice. Ifnar1-deficient mast cells showed increased secretory granule synthesis and exocytosis, which probably involved the increased transcription of Tfeb. Signal transducer and activator of transcription 1(Stat1) and Stat2 were unexpectedly insufficient to mediate these IFN-I functions, and instead, Stat3 played a critical role in a redundant manner with Stat1. Our findings revealed a novel regulation mechanism of mast cell homeostasis, in which IFN-I controls lysosome-related organelle biogenesis.

Chronic neurodegeneration induces type I interferon synthesis via STING, shaping microglial phenotype and accelerating disease progression.

Type I interferons (IFN‐I) are the principal antiviral molecules of the innate immune system and can be made by most cell types, including central nervous system cells. IFN‐I has been implicated in neuroinflammation during neurodegeneration, but its mechanism of induction and its consequences remain unclear. In the current study, we assessed expression of IFN‐I in murine prion disease (ME7) and examined the contribution of the IFN‐I receptor IFNAR1 to disease progression. The data indicate a robust IFNβ response, specifically in microglia, with evidence of IFN‐dependent genes in both microglia and astrocytes. This IFN‐I response was absent in stimulator of interferon genes (STING−/−) mice. Microglia showed increased numbers and activated morphology independent of genotype, but transcriptional signatures indicated an IFNAR1‐dependent neuroinflammatory phenotype. Isolation of microglia and astrocytes demonstrated disease‐associated microglial induction of Tnfα, Tgfb1, and of phagolysosomal system transcripts including those for cathepsins, Cd68, C1qa, C3, and Trem2, which were diminished in IFNAR1 and STING deficient mice. Microglial increases in activated cathepsin D, and CD68 were significantly reduced in IFNAR1−/− mice, particularly in white matter, and increases in COX‐1 expression, and prostaglandin synthesis were significantly mitigated. Disease progressed more slowly in IFNAR1−/− mice, with diminished synaptic and neuronal loss and delayed onset of neurological signs and death but without effect on proteinase K‐resistant PrP levels. Therefore, STING‐dependent IFN‐I influences microglial phenotype and influences neurodegenerative progression despite occurring secondary to initial degenerative changes. These data expand our mechanistic understanding of IFN‐I induction and its impact on microglial function during chronic neurodegeneration.

TLR5 Signaling Ameliorates Liver Fibrosis by Inducing Interferon β-Interleukin-1 Receptor Antagonist in Mice

Background: Bacterial flagellin, recognized by cell surface of toll-like receptor (TLR) 5, is a potent activator of many types of cells, leading to the activation of innate or adaptive immunity, which are pivotal in regulating fibrotic process. However, the exact role of TLR5 signaling in liver fibrosis is still unclear. Methods: Hepatotoxin- and cholestasis-induced liver fibrosis models were used in this study. Real-time PCR, Western blotting, and histopathologic analysis were performed to elucidate the underlying mechanism of TLR5 signaling in the pathogenesis of liver fibrosis. Findings: Flagellin-induced TLR5 activation significantly decreased the severity of liver fibrosis. Notably, hepatic expression of interleukin-1 receptor antagonist (IL-1ra) and interferon (IFN) β was markedly increased in fibrotic livers upon flagellin treatment. Consistently, in vivo activation of TLR5 signaling significantly increased IFNβ and IL-1ra expression in the livers. Interestingly, flagellin injection significantly exacerbated the severity of liver fibrosis in IFN-α/β receptor-1 (IFNAR1)-deficient mice. Furthermore, hepatic expression of IL-1ra in the fibrotic livers of IFNAR1-deficient mice was significantly lower than those of WT mice. In support of these findings, flagellin-mediated IL-1ra production is not sufficient to alleviate the severity of hepatic fibro-inflammatory responses in IFNAR1-deficient milieu. Finally, hepatic stellate cells treated with IL-1ra showed significantly decreased cellular activation and its associated fibrogenic responses. Interpretation: Collectively, manipulation of TLR5 signaling may be a promising therapeutic strategy for the treatment of liver fibrosis. Funding Statement: This research was supported by grant (NRF-2017R1D1A3B03030521, 2017R1A6A3A11032024) of the Basic Science Research Program through the National Research Foundation (NRF), funded by the Ministry of Education, Republic of Korea Declaration of Interests: The authors declare that there are no conflicts of interests. Ethics Approval Statement: Experimental procedures and animal management procedures were undertaken in accordance with the requirements of the Animal Care and Ethics Committees of Chonbuk National University. The animal facility of Chonbuk National University is fully accredited by the National Association of Laboratory Animal Care.

The role of type I IFN signaling at the choroid plexus during agingA

Event Abstract Back to Event The role of type I IFN signaling at the choroid plexus during agingA Nina Gorlé1, 2*, Sriram Balusu3, 4, Elien Van Wonterghem1, 2, Griet Van Imschoot1, 2, Jan Hoeijmakers5 and Roos Vandenbroucke1, 2 1 Center for Inflammation Research, Flanders Institute for Biotechnology, Belgium 2 Department of Biomedical Molecular Biology, Ghent University, Belgium 3 VIB & KU Leuven Center for Brain & Disease Research, Belgium 4 Department of Neurosciences, KU Leuven, Belgium 5 Department of Molecular Genetics, Erasmus University Medical Center, Netherlands Background. Biological barriers between the brain and the systemic blood circulation are important for the homeostasis in the brain, hence malfunctioning of these barriers can cause damage to the CNS. One of these barriers is the blood-cerebrospinal fluid (CSF) barrier, formed by choroid plexus epithelial (CPE) cells. Aging is a complex, multifactorial process, characterized by progressive loss of physiological integrity and is a major risk factor for neurodegenerative diseases such as Alzheimer’s disease. Changes at the blood-CSF barrier during aging have already been reported. However it is not yet clear how aging affects blood-CSF barrier integrity. Results. Natural aging is associated with decreased blood-CSF barrier integrity and increased type I IFN signaling in the CPE cells. Interestingly, old IFNAR1 deficient mice show less age-induced blood-CSF barrier leakage and intracerebroventricular (icv) injection of type I IFNs in young mice induced blood-CSF barrier leakage. Moreover, icv injection of type I IFNs in wild type mice induced cognitive decline, which was absent in IFNAR1 deficient mice. Altogether, these data suggest a causative relation between increased type I IFN signaling, loss of blood-CSF barrier integrity and cognitive decline. Next, we hypothesized that the presence of DNA damage that has been described at the choroid plexus upon aging is the cause of the age-dependent increase in type I IFN signaling . Analysis of 12 weeks old ERCC1Δ/- mice, a model of fast aging based on the accumulation of DNA damage, revealed that these mice show similar alterations at the choroid plexus as what we observed in naturally-aged mice: loss of blood-CSF barrier integrity and increased expression of type I IFN dependent genes. These data confirm that age-associated DNA damage might be responsible for the increased type I IFN signaling and loss of blood-CSF barrier integrity. Conclusion. Our data indicate that DNA accumulation upon aging induces type I IFN signaling at the blood-CSF barrier, which is responsible for the loss of blood-CSF barrier integrity and subsequent cognitive decline. Keywords: Choroid Plexus, DNA Damage, type I interferon, blood-CSF barrier, Aging Conference: 13th National Congress of the Belgian Society for Neuroscience , Brussels, Belgium, 24 May - 24 May, 2019. Presentation Type: Poster presentation Topic: Cellular/Molecular Neuroscience Citation: Gorlé N, Balusu S, Van Wonterghem E, Van Imschoot G, Hoeijmakers J and Vandenbroucke R (2019). The role of type I IFN signaling at the choroid plexus during agingA. Front. Neurosci. Conference Abstract: 13th National Congress of the Belgian Society for Neuroscience . doi: 10.3389/conf.fnins.2019.96.00049 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Apr 2019; Published Online: 27 Sep 2019. * Correspondence: Mx. Nina Gorlé, Center for Inflammation Research, Flanders Institute for Biotechnology, Ghent, East Flanders, 9052, Belgium, ninag@irc.ugent.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Nina Gorlé Sriram Balusu Elien Van Wonterghem Griet Van Imschoot Jan Hoeijmakers Roos Vandenbroucke Google Nina Gorlé Sriram Balusu Elien Van Wonterghem Griet Van Imschoot Jan Hoeijmakers Roos Vandenbroucke Google Scholar Nina Gorlé Sriram Balusu Elien Van Wonterghem Griet Van Imschoot Jan Hoeijmakers Roos Vandenbroucke PubMed Nina Gorlé Sriram Balusu Elien Van Wonterghem Griet Van Imschoot Jan Hoeijmakers Roos Vandenbroucke Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Type I Interferon Signaling Is Required for Dacryoadenitis in the Nonobese Diabetic Mouse Model of Sjögren Syndrome.

Nonobese diabetic (NOD) mice spontaneously develop lacrimal and salivary gland autoimmunity similar to human Sjögren syndrome. In both humans and NOD mice, the early immune response that drives T-cell infiltration into lacrimal and salivary glands is poorly understood. In NOD mice, lacrimal gland autoimmunity spontaneously occurs only in males with testosterone playing a role in promoting lacrimal gland inflammation, while female lacrimal glands are protected by regulatory T cells (Tregs). The mechanisms of this male-specific lacrimal gland autoimmunity are not known. Here, we studied the effects of Treg depletion in hormone-manipulated NOD mice and lacrimal gland gene expression to determine early signals required for lacrimal gland inflammation. While Treg-depletion was not sufficient to drive dacryoadenitis in castrated male NOD mice, chemokines (Cxcl9, Ccl19) and other potentially disease-relevant genes (Epsti1, Ubd) were upregulated in male lacrimal glands. Expression of Cxcl9 and Ccl19, in particular, remained significantly upregulated in the lacrimal glands of lymphocyte-deficient NOD-severe combined immunodeficiency (SCID) mice and their expression was modulated by type I interferon signaling. Notably, Ifnar1-deficient NOD mice did not develop dacryoadenitis. Together these data identify disease-relevant genes upregulated in the context of male-specific dacryoadenitis and demonstrate a requisite role for type I interferon signaling in lacrimal gland autoimmunity in NOD mice.

Type I IFNs drive hematopoietic stem and progenitor cell collapse via impaired proliferation and increased RIPK1-dependent cell death during shock-like ehrlichial infection.

Type I interferons (IFNα/β) regulate diverse aspects of host defense, but their impact on hematopoietic stem and progenitor cells (HSC/HSPCs) during infection remains unclear. Hematologic impairment can occur in severe infections, thus we sought to investigate the impact of type I IFNs on hematopoiesis in a tick-borne infection with a virulent ehrlichial pathogen that causes shock-like disease. During infection, IFNα/β induced severe bone marrow (BM) loss, blunted infection-induced emergency myelopoiesis, and reduced phenotypic HSPCs and HSCs. In the absence of type I IFN signaling, BM and splenic hematopoiesis were increased, and HSCs derived from Ifnar1-deficient mice were functionally superior in competitive BM transplants. Type I IFNs impaired hematopoiesis during infection by both limiting HSC/HSPC proliferation and increasing HSPC death. Using mixed BM chimeras we determined that type I IFNs restricted proliferation indirectly, whereas HSPC death occurred via direct IFNαR -mediated signaling. IFNαR-dependent signals resulted in reduced caspase 8 expression and activity, and reduced cleavage of RIPK1 and RIPK3, relative to Ifnar1-deficient mice. RIPK1 antagonism with Necrostatin-1s rescued HSPC and HSC numbers during infection. Early antibiotic treatment is required for mouse survival, however antibiotic-treated survivors had severely reduced HSPCs and HSCs. Combination therapy with antibiotics and Necrostatin-1s improved HSPC and HSC numbers in surviving mice, compared to antibiotic treatment alone. We reveal two mechanisms whereby type I IFNs drive hematopoietic collapse during severe infection: direct sensitization of HSPCs to undergo cell death and enhanced HSC quiescence. Our studies reveal a strategy to ameliorate the type I IFN-dependent loss of HSCs and HSPCs during infection, which may be relevant to other infections wherein type I IFNs cause hematopoietic dysfunction.

Investigation of the immunological mechanisms underlying the attenuation of vaccinia virus lacking host-range factor C7

Abstract Vaccinia virus C7 protein is an important host-range factor for the vaccinia virus life cycle in mammalian cells. Type I IFN plays an important role in host defense of viral infection. However, the role of C7 in immune modulation of the IFN pathway is unclear. Here, we find that C7 functions as a dual inhibitor of IFN production and IFN signaling by interfering with the activation of two transcription factors IRF3 and STAT2. Furthermore, vaccinia virus with deletion of C7 (VACVΔC7L) is non-pathogenic in wild-type C57BL/6J mice in an intranasal infection model. We elucidated the immunological mechanisms underlying the attenuation phenotype of VACVΔC7L, which can be summarized as follows: (i) intranasal infection of VACVΔC7L triggers the production of interferons (IFNs), proinflammatory cytokines and chemokines in bronchoalveolar lavage fluid (BAL), whereas WT VACV does not; (ii) intranasal infection of VACVΔC7L results in the recruitment of dendritic cells, inflammatory monocytes, neutrophils, CD8+, and CD4+ in the BAL, whereas WT VACV does not; and (iii) infection of primary type II lung alveolar epithelial cells (AECs) with VACVΔC7L induces IFN, proinflammatory cytokine and chemokine gene expression and protein secretion, whereas WT VACV does not. However, VACVΔC7L dramatically gained virulence in STAT2 or IFNAR1-deficient mice, with increased titers in the lungs and systemic dissemination of the viruses to the blood and distant organs. Taken together, our results provide evidence that vaccinia C7 is a key virulence factor that antagonize both IFN production and signaling and IFNAR1 and STAT2 are critical in restricting vaccinia viral replication in the lung alveolar epithelial cells.

A Plant-Derived Nucleic Acid Reconciles Type I IFN and a Pyroptotic-like Event in Immunity against Respiratory Viruses.

Nucleic acids carrying pathogen-associated molecular patterns trigger innate immune responses and are used to activate host immunity. Although synthetic nucleic acids have been used for that purpose, they have shown limitations for in vivo and clinical applications. To address this issue, we tested a naturally occurring dsRNA extracted from rice bran (rb-dsRNA) and characterized it as a potent ligand of TLR3 and MDA5. In this study, intranasal administration of rb-dsRNA induced production of type I IFNs by alveolar macrophages and protected mice from morbidity and mortality resulting from respiratory virus infection, such as influenza A virus. This protection was completely absent in mice lacking both TRIF and MDA5, indicating the essential role of TLR3- and MDA5-dependent pathways. Interestingly, IFNAR1-deficient mice retained residual antiviral protection, which was abolished by pharmacological inhibition of caspase 1, but not IL-1β signaling. In fact, rb-dsRNA activated caspase 1 via TRIF, resulting in the release of IL-1β and LDH. In addition to the direct antiviral activity, rb-dsRNA modulated the immune cell population in the lungs by repopulating virus-depleted alveolar macrophages. Our data demonstrate that rb-dsRNA orchestrates IFN-dependent and -independent direct antiviral protection and that it is a potent immune stimulator modulating antiviral immunity in the lungs. These findings open doors to a range of precise immune-modulating studies and therapeutic options.

Type I Interferon Signaling Prevents IL-1β-Driven Lethal Systemic Hyperinflammation during Invasive Bacterial Infection of Soft Tissue.

Type I interferons (IFN-Is) are fundamental for antiviral immunity, but their role in bacterial infections is contradictory and incompletely described. Streptococcus pyogenes activates IFN-I production in innate immune cells, and IFN-I receptor 1 (Ifnar1)-deficient mice are highly susceptible to S. pyogenes infection. Here we report that IFN-I signaling protects the host against invasive S. pyogenes infection by restricting inflammation-driven damage in distant tissues. Lethality following infection in Ifnar1-deficient mice is caused by systemically exacerbated levels of the proinflammatory cytokine IL-1β. Critical cellular effectors of IFN-I in vivo are LysM+ and CD11c+ myeloid cells, which exhibit suppression of Il1b transcription upon Ifnar1 engagement. These cells are also the major source of IFN-β, which is significantly induced by S. pyogenes 23S rRNA in an Irf5-dependent manner. Our study establishes IL-1β and IFN-I levels as key homeostatic variables of protective, yet tuned, immune responses against severe invasive bacterial infection.

Dual Inhibition of TNFR1 and IFNAR1 in Imiquimod-Induced Psoriasiform Skin Inflammation in Mice.

Psoriasis is a chronic inflammatory skin disease affecting 2-3% of the world population and is mainly characterized by epidermal hyperplasia, scaling, and erythema. A prominent role for TNF in the pathogenesis of psoriasis has been shown, and consequently various types of TNF antagonists such as etanercept and infliximab have been used successfully. Recently, increasing amounts of data suggest that type I IFNs are also crucial mediators of psoriasis. To investigate whether blocking their respective receptors would be useful, TNFR1- and IFNAR1-deficient mice were challenged with Aldara, which contains imiquimod, and is used as an experimental model to induce psoriasis-like skin lesions in mice. Both transgenic mice showed partial protection toward Aldara-induced inflammation compared with control groups. Additionally, TNFR1 knockout mice showed sustained type I IFN production in response to Aldara. Double knockout mice lacking both receptors showed superior protection to Aldara in comparison with the single knockout mice and displayed reduced levels of IL-12p40, IL-17F, and S100A8, indicating that the TNF and type I IFN pathways contribute significantly to inflammation upon treatment with Aldara. Our findings reveal that dual inhibition of TNFR1 and IFNAR1 may represent a potential novel strategic treatment of psoriasis.

21: Essential function of type I IFN signaling in balancing inflammation during Streptococcus pyogenes infection

Streptococcus pyogenes also known as Group A Streptoccocus (GAS) is a common human pathogen responsible of a variety of diseases that range from mild pharyngitis to rare but invasive and life-threatening infections. We have demonstrated that type I interferon (IFN) signaling is required for mice survival in a model of subcutaneous infection with S. pyogenes . However, it is not understood how these cytokines are induced and how they protect the host. Using mice deficient in the type I IFN receptor IFNAR1 we observed increased tissue damage at the site of infection despite similar bacterial loads in the absence of type I IFN signaling. IFNAR1-deficient mice exhibit hyperinflammation with increased levels of IL-1s in the infected tissue and in the liver and spleen. Excessive IL-1s production seems to promote organ injury as confirmed by the histology analysis and by the levels of transaminases and other parameters measured in the blood. On the other hand, IL-1s signaling is essential for mouse survival during infection with S. pyogenes since mice lacking the IL-1 receptor or Caspase-1, the key IL-1s-processing enzyme, are highly susceptible to S. pyogenes infection. Together, our data provide evidence that type I IFNs are essential for balancing the immune response against S. pyogenes and that the absence of type I IFN signaling results in lethal systemic hyperinflammation accompanied by overproduction of IL-1b.

Toll-like receptor 7-mediated type I interferon signaling prevents cholestasis- and hepatotoxin-induced liver fibrosis

Toll-like receptor 7 (TLR7) signaling predominantly regulates production of type I interferons (IFNs), which has been suggested in clinical studies to be antifibrotic. However, the mechanistic role of the TLR7-type I IFN axis in liver fibrosis has not been elucidated. In the present study, liver fibrosis was induced in wild-type (WT), TLR7-deficient, and IFN-α/β receptor-1 (IFNAR1)-deficient mice and TLR7-mediated signaling was assessed in liver cells isolated from these mice. TLR7-deficient and IFNAR1-deficient mice were more susceptible to liver fibrosis than WT mice, indicating that TLR7-type I IFN signaling exerts a protective effect against liver fibrosis. Notably, the hepatic expression of interleukin-1 receptor antagonist (IL-1ra) was suppressed in TLR7- or IFNAR1-deficient mice compared with respective WT mice, and treatment with recombinant IL-1ra reduced liver fibrosis. In vivo activation of TLR7 significantly increased IFNa4 and IL-1ra expression in the liver. Interestingly, each cytokine had a different cellular source, showing that dendritic cells (DCs) are the responsible cell type for production of type I IFN, while Kupffer cells (KCs) mainly produce IL-1ra in response to type I IFN. Furthermore, TLR7 activation by R848 injection suppressed liver fibrosis and production of proinflammatory cytokines, and these effects were dependent on type I IFN signaling. Consistent with in vivo data, IFN-α significantly induced IL-1ra production in primary KCs. TLR7 signaling activates DCs to produce type I IFN, which in turn induces antifibrogenic IL-1ra production in KCs. Thus, manipulation of the TLR7-type I IFN-IL-1ra axis may be a new therapeutic strategy for the treatment of liver fibrosis.

Type I IFN signaling in CD8- DCs impairs Th1-dependent malaria immunity.

Many pathogens, including viruses, bacteria, and protozoan parasites, suppress cellular immune responses through activation of type I IFN signaling. Recent evidence suggests that immune suppression and susceptibility to the malaria parasite, Plasmodium, is mediated by type I IFN; however, it is unclear how type I IFN suppresses immunity to blood-stage Plasmodium parasites. During experimental severe malaria, CD4+ Th cell responses are suppressed, and conventional DC (cDC) function is curtailed through unknown mechanisms. Here, we tested the hypothesis that type I IFN signaling directly impairs cDC function during Plasmodium infection in mice. Using cDC-specific IFNAR1-deficient mice, and mixed BM chimeras, we found that type I IFN signaling directly affects cDC function, limiting the ability of cDCs to prime IFN-γ-producing Th1 cells. Although type I IFN signaling modulated all subsets of splenic cDCs, CD8- cDCs were especially susceptible, exhibiting reduced phagocytic and Th1-promoting properties in response to type I IFNs. Additionally, rapid and systemic IFN-α production in response to Plasmodium infection required type I IFN signaling in cDCs themselves, revealing their contribution to a feed-forward cytokine-signaling loop. Together, these data suggest abrogation of type I IFN signaling in CD8- splenic cDCs as an approach for enhancing Th1 responses against Plasmodium and other type I IFN-inducing pathogens.

Alpha/Beta Interferon Receptor Signaling Amplifies Early Proinflammatory Cytokine Production in the Lung during Respiratory Syncytial Virus Infection

ABSTRACTType I interferons (IFNs) are produced early upon virus infection and signal through the alpha/beta interferon (IFN-α/β) receptor (IFNAR) to induce genes that encode proteins important for limiting viral replication and directing immune responses. To investigate the extent to which type I IFNs play a role in the local regulation of inflammation in the airways, we examined their importance in early lung responses to infection with respiratory syncytial virus (RSV). IFNAR1-deficient (IFNAR1−/−) mice displayed increased lung viral load and weight loss during RSV infection. As expected, expression of IFN-inducible genes was markedly reduced in the lungs of IFNAR1−/− mice. Surprisingly, we found that the levels of proinflammatory cytokines and chemokines in the lungs of RSV-infected mice were also greatly reduced in the absence of IFNAR signaling. Furthermore, low levels of proinflammatory cytokines were also detected in the lungs of IFNAR1−/− mice challenged with noninfectious innate immune stimuli such as selected Toll-like receptor (TLR) agonists. Finally, recombinant IFN-α was sufficient to potentiate the production of inflammatory mediators in the lungs of wild-type mice challenged with innate immune stimuli. Thus, in addition to its well-known role in antiviral resistance, type I IFN receptor signaling acts as a central driver of early proinflammatory responses in the lung. Inhibiting the effects of type I IFNs may therefore be useful in dampening inflammation in lung diseases characterized by enhanced inflammatory cytokine production.IMPORTANCE The initial response to viral infection is characterized by the production of interferons (IFNs). One group of IFNs, the type I IFNs, are produced early upon virus infection and signal through the IFN-α/β receptor (IFNAR) to induce proteins important for limiting viral replication and directing immune responses. Here we examined the importance of type I IFNs in early responses to respiratory syncytial virus (RSV). Our data suggest that type I IFN production and IFNAR receptor signaling not only induce an antiviral state but also serve to amplify proinflammatory responses in the respiratory tract. We also confirm this conclusion in another model of acute inflammation induced by noninfectious stimuli. Our findings are of relevance to human disease, as RSV is a major cause of infant bronchiolitis and polymorphisms in the IFN system are known to impact disease severity.

IFNβ Produced by TLR4-Activated Tumor Cells Is Involved in Improving the Antitumoral Immune Response

Toll-like receptor (TLR) ligands may be a valuable tool to promote antitumor responses by reinforcing antitumor immunity. In addition to their expression in immune cells, functional TLRs are also expressed by many cancer cells, but their significance has been controversial. In this study, we examined the action of TLR ligands on tumor pathophysiology as a result of direct tumor cell effects. B16 murine melanoma cells were stimulated in vitro with a TLR4 ligand (LPS-B16) prior to inoculation into TLR4-deficient mice (Tlr4 (lps-del)). Under such conditions, B16 cells yielded smaller tumors than nonstimulated B16 cells. The apoptosis/proliferation balance of the cells was not modified by TLR ligand treatment, nor was this effect compromised in immunocompromised nude mice. Mechanistic investigations revealed that IFNβ was the critical factor produced by TLR4-activated tumor cells in mediating their in vivo outgrowth. Transcriptional analysis showed that TLR4 activation on B16 cells induced changes in the expression of type I IFN and type I IFN-related genes. Most importantly, culture supernatants from LPS-B16 cells improved the maturation of bone marrow-derived dendritic cells (BMDC) from TLR4-deficient mice, upregulating the expression of interleukin-12 and costimulatory molecules on those cells. BMDC maturation was blunted by addition of an IFNβ-neutralizing antibody. Moreover, tumor growth inhibition observed in LPS-B16 tumors was abrogated in IFNAR1-deficient mice lacking a functional type I IFN receptor for binding IFN. Together, our findings show that tumor cells can be induced through the TLR4 pathway to produce IFN and positively contribute to the antitumoral immune response.