Positive feedback regulation of type I IFN genes by the IFN-inducible transcription factor IRF-7

Type 1 IFN Induction by Cytosolic Nucleic Acid Is Intact in Neonatal Mononuclear Cells, Contrasting Starkly with Neonatal Hyporesponsiveness to TLR Ligation Due to Independence from Endosome-Mediated IRF3 Activation

Two million infants die each year from infectious diseases before they reach 12 mo; many of these diseases are vaccine preventable in older populations. Pattern recognition receptors represent the critical front-line defense against pathogens. Evidence suggests that the innate immune system does not fully develop until puberty, contributing to impaired response to infection and impaired vaccine responses in neonates, infants, and children. The activity of the pattern recognition receptor family of cytosolic nucleic acid (CNA) sensors in this pediatric population has not been reported. We show that in direct contrast to weak TLR-induced type I IFN in human cord blood mononuclear cells, cord blood mononuclear cells are capable of initiating a potent response to CNA, inducing both antiviral type I IFN and, unexpectedly, proinflammatory TNF-α. A deficiency in Rab11-GTPase endosome formation and consequent lack of IRF3 activation in neonatal monocytes is at least in part responsible for the marked disparity in TLR-induced IFN production between neonatal and adult monocytes. CNA receptors do not rely on endosome formation, and therefore, these responses remain intact in neonates. Heightened neonatal responses to CNA challenge are maintained in children up to 2 y of age and, in marked contrast to TLR4/9 agonists, result in IL-12p70 and IFN-γ generation. CNA sensors induce robust antiviral and proinflammatory pathways in neonates and children and possess great potential for use as immunostimulants or vaccine adjuvants for targeted neonatal and pediatric populations to promote cell-mediated immunity against invasive infectious disease.

Janus Kinase Inhibitor Baricitinib Modulates Human Innate and Adaptive Immune System

The purpose of this study was to elucidate the mechanism of action of baricitinib on Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling, which involves in human innate and adaptive immune system. The effects of baricitinib were evaluated using human monocyte-derived dendritic cells (MoDCs), plasmacytoid dendritic cells (pDCs), B cells, and T cells. Baricitinib concentration-dependently suppressed the expression of CD80/CD86 on MoDCs and the production of type-I interferon (IFN) by pDCs. Baricitinib also suppressed the differentiation of human B cells into plasmablasts by B cell receptor and type-I IFN stimuli and inhibited the production of interleukin (IL)-6 from B cells. Human CD4⁺ T cells proliferated after T cell receptor stimulation with anti-CD3 and anti-CD28 antibody; however, such proliferation was suppressed by baricitinib in a concentration-dependent manner. In addition, baricitinib inhibited Th1 differentiation after IL-12 stimulation and Th17 differentiation by TGF-β1, IL-6, IL-1β, and IL-23 stimulation. Tofacitinib showed similar effects in these experiments. In naive CD4⁺ T cells, IFN-α and IFN-γ induced phosphorylation of STAT1, which was inhibited by baricitinib and tofacitinib. Furthermore, IL-6-induced phosphorylation of STAT1 and STAT3 was also inhibited by JAK inhibitors. In conclusion, the results indicated that baricitinib suppresses the differentiation of plasmablasts, Th1 and Th17 cells, as well as innate immunity, such as the T cell stimulatory capacity of dendritic cells. Thus, JAK inhibitors can be potentially clinically effective not only in rheumatoid arthritis but other immune-related diseases.

CD19+CD24hiCD38hi B Cells Are Expanded in Juvenile Dermatomyositis and Exhibit a Pro-Inflammatory Phenotype After Activation Through Toll-Like Receptor 7 and Interferon-α

Juvenile dermatomyositis (JDM) is a rare form of childhood autoimmune myositis that presents with proximal muscle weakness and skin rash. B cells are strongly implicated in the pathogenesis of the disease, but the underlying mechanisms are unknown. Therefore, the main objective of our study was to investigate mechanisms driving B cell lymphocytosis and define pathological features of B cells in JDM patients. Patients were recruited through the UK JDM Cohort and Biomarker study. Peripheral blood B cell subpopulations were immunophenotyped by flow cytometry. The results identified that immature transitional B cells were significantly expanded in active JDM, actively dividing, and correlated positively with disease activity. Protein and RNAseq analysis revealed high interferon alpha (IFNα) and TLR7-pathway signatures pre-treatment. Stimulation of B cells through TLR7/8 promoted both IL-10 and IL-6 production in controls but failed to induce IL-10 in JDM patient cells. Interrogation of the CD40–CD40L pathway (known to induce B cell IL-10 and IL-6) revealed similar expression of IL-10 and IL-6 in B cells cultured with CD40L from both JDM patients and controls. In conclusion, JDM patients with active disease have a significantly expanded immature transitional B cell population which correlated with the type I IFN signature. Activation through TLR7 and IFNα may drive the expansion of immature transitional B cells in JDM and skew the cells toward a pro-inflammatory phenotype.

MicroRNA-182 inhibits HCMV replication through activation of type I IFN response by targeting FOXO3 in neural cells

Human cytomegalovirus (HCMV) has led to kinds of clinical disorders and great morbidity worldwide, such as sensorineural hearing loss (SNHL), mental retardation, and developmental delays in immunocompromised individuals. Congenital HCMV infection is a leading cause of birth defects, primarily manifesting as neurological disorders. Previous studies reported that HCMV has evolved a variety of mechanisms to evade the immune system, such as dysregulation of miRNAs. However, reports concerning the role of miRNA in HCMV infection in neural cells are limited. Here, we reported that a host microRNA, miR-182, was significantly up-regulated by HCMV infection in U-251MG and NPCs cells. Subsequently, our results of in vitro and in vivo experiments demonstrated that miR-182 was a positive regulator of interferon regulatory factor 7 (IRF7) by directly targeting FOXO3, resulting in the induction of IFN-I response and suppression of HCMV replication in neural cells. Taken together, our findings provide detailed molecular mechanisms of the antiviral function of miR-182 against HCMV infection in neural cells, and suggest an intrinsic anti-HCMV therapeutic target.

Composition and transcription of all interferon regulatory factors (IRFs), IRF1‒11 in a perciform fish, the mandarin fish, Siniperca chuatsi

Interferon regulatory factors (IRFs) are a family of mediators in various biological processes including immune modulation of interferon (IFN) and proinflammatory cytokine expression. However, the data on the complete composition of IRFs is rather limited in teleost fish. In the present study, all IRF members, i.e. IRF1‒11 with two IRF4, IRF4a and IRF4b have been characterised in an aquaculture species of fish, the mandarin fish, Siniperca chuatsi, in addition to the previous report of IRF1, IRF2, IRF3 and IRF7 from the fish. These IRFs are constitutively expressed in various organs/tissues of the fish, and their expression can be induced following the stimulation of polyinosinic:polycytidylic acid (poly(I:C)) and the infection of infectious spleen and kidney necrosis virus (ISKNV), a viral pathogen of mandarin fish in aquaculture. The ISKNV infection induced the significant increase in the expression of some IRF genes, i.e. IRF2, IRF4a, IRF7, IRF9, IRF10 at 24 or 36 h post-infection (hpi) in spleen and head-kidney, and the significant increase of some other IRF genes, e.g. IRF1, IRF3, IRF4b, IRF5, IRF6, IRF8 at later stage of infection from 72, or 96, or even 120 hpi, which may imply the inhibitory effect of ISKNV on fish immune response. It is considered that the present study provides the first detailed analysis on all IRF members in an aquaculture species of fish, and can be served as the base for further investigation on the role of IRFs in teleost fish.

Pro-apoptotic signaling induced by Retinoic acid and dsRNA is under the control of Interferon Regulatory Factor-3 in breast cancer cells

Breast cancer is one of the most lethal malignancies for women. Retinoic acid (RA) and double-stranded RNA (dsRNA) are considered signaling molecules with potential anticancer activity. RA, co-administered with the dsRNA mimic polyinosinic-polycytidylic acid (poly(I:C)), synergizes to induce a TRAIL (Tumor-Necrosis-Factor Related Apoptosis-Inducing Ligand)- dependent apoptotic program in breast cancer cells. Here, we report that RA/poly(I:C) co-treatment, synergically, induce the activation of Interferon Regulatory Factor-3 (IRF3) in breast cancer cells. IRF3 activation is mediated by a member of the pathogen recognition receptors, Toll-like receptor-3 (TLR3), since its depletion abrogates IRF3 activation by RA/poly(I:C) co-treatment. Besides induction of TRAIL, apoptosis induced by RA/poly(I:C) correlates with the increased expression of pro-apoptotic TRAIL receptors, TRAIL-R1/2, and the inhibition of the antagonistic receptors TRAIL-R3/4. IRF3 plays an important role in RA/poly(I:C)-induced apoptosis since IRF3 depletion suppresses caspase-8 and caspase-3 activation, TRAIL expression upregulation and apoptosis. Interestingly, RA/poly(I:C) combination synergizes to induce a bioactive autocrine/paracrine loop of type-I Interferons (IFNs) which is ultimately responsible for TRAIL and TRAIL-R1/2 expression upregulation, while inhibition of TRAIL-R3/4 expression is type-I IFN-independent. Our results highlight the importance of IRF3 and type-I IFNs signaling for the pro-apoptotic effects induced by RA and synthetic dsRNA in breast cancer cells.

Modulation of type I interferon signaling by African swine fever virus (ASFV) of different virulence L60 and NHV in macrophage host cells

ASFV causes an important disease of domestic swine and wild boar. Currently no vaccine is available, highlighting the necessity to understand ASFV modulation of innate immune responses in natural host cells. With this aim, macrophage cultures enriched in SWC9 and CD163 differentiation markers were infected in parallel with high virulent ASFV/L60 and low virulent ASFV/NHV, the latter lacking MGF 360 and 505/530 genes associated with type I interferon (IFN I) control. IFN I production and signaling were studied after completion of the viral cycles. None of the viruses increased IFN I production in host cells, and accordingly, didn't cause activation of the central mediator of the pathway IRF3. However, upon stimulation by poly:IC treatment during infections, L60 and NHV similarly inhibited IFN I production. This didn't seem to depend on IRF3 modulation since its activation levels were not significantly decreased in L60 infection and were even increased in NHV's, in comparison to stimulated mock infections. The infections didn't evidently activate JAK-STAT pathway mediators STAT1 and STAT2, but did increase expression of interferon stimulated genes (ISGs), to higher levels in NHV than L60 infection. Interestingly, in presence of IFN-α, L60 but not NHV was able to decrease significantly the expression of some of the ISGs tested. Overall, both L60 and NHV were able to inhibit IFN I production in macrophages, through a mechanism not dependent on IRF3 modulation. The high virulent isolate showed however a more effective control of the downstream ISGs expression pathway.

Innate Immune Response to Viral Infections in Primary Bronchial Epithelial Cells is Modified by the Atopic Status of Asthmatic Patients

Purpose

In order to gain an insight into determinants of reported variability in immune responses to respiratory viruses in human bronchial epithelial cells (HBECs) from asthmatics, the responses of HBEC to viral infections were evaluated in HBECs from phenotypically heterogeneous groups of asthmatics and in healthy controls.

Methods

HBECs were obtained during bronchoscopy from 10 patients with asthma (6 atopic and 4 non-atopic) and from healthy controls (n=9) and grown as undifferentiated cultures. HBECs were infected with parainfluenza virus (PIV)-3 (MOI 0.1) and rhinovirus (RV)-1B (MOI 0.1), or treated with medium alone. The cell supernatants were harvested at 8, 24, and 48 hours. IFN-α, CXCL10 (IP-10), and RANTES (CCL5) were analyzed by using Cytometric Bead Array (CBA), and interferon (IFN)-β and IFN-λ1 by ELISA. Gene expression of IFNs, chemokines, and IFN-regulatory factors (IRF-3 and IRF-7) was determined by using quantitative PCR.

Results

PIV3 and RV1B infections increased IFN-λ1 mRNA expression in HBECs from asthmatics and healthy controls to a similar extent, and virus-induced IFN-λ1 expression correlated positively with IRF-7 expression. Following PIV3 infection, IP-10 protein release and mRNA expression were significantly higher in asthmatics compared to healthy controls (median 36.03-fold). No differences in the release or expression of RANTES, IFN-λ1 protein and mRNA, or IFN-α and IFN-β mRNA between asthmatics and healthy controls were observed. However, when asthmatics were divided according to their atopic status, HBECs from atopic asthmatics (n=6) generated significantly more IFN-λ1 protein and demonstrated higher IFN-α, IFN-β, and IRF-7 mRNA expressions in response to PIV3 compared to non-atopic asthmatics (n=4) and healthy controls (n=9). In response to RV1B infection, IFN-β mRNA expression was lower (12.39-fold at 24 hours and 19.37-fold at 48 hours) in non-atopic asthmatics compared to atopic asthmatics.

Conclusions

The immune response of HBECs to virus infections may not be deficient in asthmatics, but seems to be modified by atopic status.

IFN-β: A Contentious Player in Host-Pathogen Interaction in Tuberculosis

Tuberculosis (TB) is a major health threat to the human population worldwide. The etiology of the disease is Mycobacterium tuberculosis (Mtb), a highly successful intracellular pathogen. It has the ability to manipulate the host immune response and to make the intracellular environment suitable for its survival. Many studies have addressed the interactions between the bacteria and the host immune cells as involving many immune mediators and other cellular players. Interferon-β (IFN-β) signaling is crucial for inducing the host innate immune response and it is an important determinant in the fate of mycobacterial infection. The role of IFN-β in protection against viral infections is well established and has been studied for decades, but its role in mycobacterial infections remains much more complicated and debatable. The involvement of IFN-β in immune evasion mechanisms adopted by Mtb has been an important area of investigation in recent years. These advances have widened our understanding of the pro-bacterial role of IFN-β in host–pathogen interactions. This pro-bacterial activity of IFN-β appears to be correlated with its anti-inflammatory characteristics, primarily by antagonizing the production and function of interleukin 1β (IL-1β) and interleukin 18 (IL-18) through increased interleukin 10 (IL-10) production and by inhibiting the nucleotide-binding domain and leucine-rich repeat protein-3 (NLRP3) inflammasome. Furthermore, it also fails to provoke a proper T helper 1 (Th1) response and reduces the expression of major histocompatibility complex II (MHC-II) and interferon-γ receptors (IFNGRs). Here we will review some studies to provide a paradigm for the induction, regulation, and role of IFN-β in mycobacterial infection. Indeed, recent studies suggest that IFN-β plays a role in Mtb survival in host cells and its downregulation may be a useful therapeutic strategy to control Mtb infection.

A protective role of IRF3 and IRF7 signalling downstream TLRs in the development of vein graft disease via type I interferons

BACKGROUND

Toll like receptors (TLR) play an important role in vein graft disease (VGD). Interferon regulatory factors (IRF) 3 and 7 are the transcriptional regulators of type I interferons (IFN) and type I IFN responsive genes and are downstream factors of TLRs. Relatively little is known with regard to the interplay of IRFs and TLRs in VGD development. The aim of this study was to investigate the role of IRF3 and IRF7 signaling downstream TLRs and the effect of IRF3 and IRF7 in VGD.

METHODS AND RESULTS

In vitro activation of TLR3 induced IRF3 and IRF7 dependent IFNβ expression in bone marrow macrophages and vascular smooth muscle cells. Activation of TLR4 showed to regulate pro-inflammatory cytokines via IRF3. Vein graft surgery was performed in Irf3^-/- , Irf7^-/- and control mice. After 14 days Irf3^-/- vein grafts had an increased vessel wall thickness compared to both control (P = 0.01) and Irf7^-/- (P = 0.02) vein grafts. After 28 days, vessel wall thickness increased in Irf3^-/- (P = 0.0003) and Irf7^-/- (P = 0.04) compared to control vein grafts and also increased in Irf7^-/- compared to Irf3^-/- vein grafts (P = 0.02). Immunohistochemical analysis showed a significant higher influx of macrophages after 14 days in Irf3^-/- vein grafts and after 28 days in Irf7^-/- vein grafts compared to control vein grafts.

CONCLUSIONS

The present study is the first to describe a protective role of both IRF3 and IRF7 in VGD. IRFs regulate VGD downstream TLRs since Irf3^-/- and Irf7^-/- vein grafts show increased vessel wall thickening after respectively 14 and 28 days after surgery.

IRF9 Prevents CD8+ T Cell Exhaustion in an Extrinsic Manner during Acute Lymphocytic Choriomeningitis Virus Infection

Effective CD8⁺ T cell responses play an important role in determining the course of a viral infection. Overwhelming antigen exposure can result in suboptimal CD8⁺ T cell responses, leading to chronic infection. This altered CD8⁺ T cell differentiation state, termed exhaustion, is characterized by reduced effector function, upregulation of inhibitory receptors, and altered expression of transcription factors. Prevention of overwhelming antigen exposure to limit CD8⁺ T cell exhaustion is of significant interest for the control of chronic infection. The transcription factor interferon regulatory factor 9 (IRF9) is a component of type I interferon (IFN-I) signaling downstream of the IFN-I receptor (IFNAR). Using acute infection of mice with lymphocytic choriomeningitis virus (LCMV) strain Armstrong, we show here that IRF9 limited early LCMV replication by regulating expression of interferon-stimulated genes and IFN-I and by controlling levels of IRF7, a transcription factor essential for IFN-I production. Infection of IRF9- or IFNAR-deficient mice led to a loss of early restriction of viral replication and impaired antiviral responses in dendritic cells, resulting in CD8⁺ T cell exhaustion and chronic infection. Differences in the antiviral activities of IRF9- and IFNAR-deficient mice and dendritic cells provided further evidence of IRF9-independent IFN-I signaling. Thus, our findings illustrate a CD8⁺ T cell-extrinsic function for IRF9, as a signaling factor downstream of IFNAR, in preventing overwhelming antigen exposure resulting in CD8⁺ T cell exhaustion and, ultimately, chronic infection.IMPORTANCE During early viral infection, overwhelming antigen exposure can cause functional exhaustion of CD8⁺ T cells and lead to chronic infection. Here we show that the transcription factor interferon regulatory factor 9 (IRF9) plays a decisive role in preventing CD8⁺ T cell exhaustion. Using acute infection of mice with LCMV strain Armstrong, we found that IRF9 limited early LCMV replication by regulating expression of interferon-stimulated genes and Irf7, encoding a transcription factor crucial for type I interferon (IFN-I) production, as well as by controlling the levels of IFN-I. Infection of IRF9-deficient mice led to a chronic infection that was accompanied by CD8⁺ T cell exhaustion due to defects extrinsic to T cells. Our findings illustrate an essential role for IRF9, as a mediator downstream of IFNAR, in preventing overwhelming antigen exposure causing CD8⁺ T cell exhaustion and leading to chronic viral infection.

Enhanced IFN-α production is associated with increased TLR7 retention in the lysosomes of palasmacytoid dendritic cells in systemic lupus erythematosus

Background

Interferon-α (IFN-α) is increased and plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). Plasmacytoid dendritic cells (pDCs) are the main producer of IFN-α, but their IFN-α producing capacity has been shown to be unchanged or reduced when stimulated with a Toll-like receptor 9 (TLR9) agonist in patients with SLE compared to in healthy individuals. In this study, we investigated the IFN-α-producing capacity of lupus pDCs under different stimulation.

Methods

pDCs from patients with SLE and healthy controls (HC) were stimulated with TLR9 or TLR7 agonist, and their IFN-α producing capacity was examined by intracellular cytokine staining and flow cytometry. The correlation of IFN-α-producing capacity with serum IFN-α levels and disease activity was assessed. The effect of in vitro IFN-α exposure on IFN-α production by pDCs was examined. Localization of TLR7 in cellular compartments in pDCs was investigated.

Results

The IFN-α producing capacity of pDCs was reduced after TLR9 stimulation, but increased when stimulated with a TLR7 agonist in SLE compared to in HC. IFN-α production by pDCs upon TLR9 stimulation was reduced and the percentage of IFN-α⁺pDC was inversely correlated with disease activity and serum IFN-α levels. However, the TLR7 agonist-induced IFN-α producing capacity of lupus pDCs was enhanced and correlated with disease activity and serum IFN-α. Exposure to IFN-α enhanced IFN-α production of TLR7-stimulated pDCs, but reduced that of pDCs activated with a TLR9 agonist. TLR7 localization was increased in late endosome/lysosome compartments in pDCs from SLE patients.

Conclusions

These findings indicate that enhanced TLR7 responses of lupus pDCs, owing to TLR7 retention in late endosome/lysosome and exposure to IFN-α, are associated with the pathogenesis of SLE.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1441-7) contains supplementary material, which is available to authorized users.

Molecular cloning and functional characterization of interferon regulatory factor 7 of the barbel chub, Squaliobarbus curriculus

The interferon regulatory factor 7 (IRF7) is a critical regulator of type-I interferon-dependent immune reaction that defense against virus. To investigate the antiviral function of IRF7 of barbel chub Squaliobarbus curriculus (ScIRF7), the cDNA of ScIRF7 was cloned and characterized. The full length cDNA of ScIRF7 was 1870 bp, consisted of 41 bp 5'-UTR, 560 bp 3'-UTR and a 1269 bp open reading frame (ORF). The ORF encoded 423 amino acids with a molecular weight of 49.426 KDa and a theoretical isoelectric point of 5.71. The putative ScIRF7 protein possesses typical domains of IRF family including a conserved N-terminal DBD-binding domain (DBD), a C-terminal IRF association domain and a serine-rich domain. In the DBD, four tryptophans were found to be highly conserved among all species, whilst in another conserved tryptophan site of mammals, the corresponding amino acids were methionine for fishes. The expression level of ScIRF7 was highest in the spleen and lowest in the liver. The expression level of IFN-β was highest in the gill and lowest in the liver. After GCRV infection, expression levels changes of ScIRF7 showed an overall tendency of firstly up-regulation and then down-regulation in the spleen and the gill; and expression levels of ScIRF7 in peripheral blood lymphocyte at 24 h post-infection was highest among all time points. In pEGFP-ScIRF7 overexpressing cells, the mRNA level of ScIRF7 was firstly up-regulation and then down-regulation; and the expression of IFN-β was significantly up-regulated at 12 h post-infection than that of control group (P < 0.05), which was significantly higher than those in pEGFP-N1 overexpressing cells. The results indicated that ScIRF7 may play a key role in immune responses of barbel chub Squaliobarbus curriculus against GCRV and may also functions in the Ctenopharyngodon idellus kidney cells.

STING-associated vasculopathy develops independently of IRF3 in mice

Patients with stimulator of interferon genes (STING)-associated vasculopathy with onset in infancy (SAVI) develop systemic inflammation characterized by vasculopathy, interstitial lung disease, ulcerative skin lesions, and premature death. Autosomal dominant mutations in STING are thought to trigger activation of IRF3 and subsequent up-regulation of interferon (IFN)-stimulated genes (ISGs) in patients with SAVI. We generated heterozygous STING N153S knock-in mice as a model of SAVI. These mice spontaneously developed inflammation within the lung, hypercytokinemia, T cell cytopenia, skin ulcerations, and premature death. Cytometry by time-of-flight (CyTOF) analysis revealed that the STING N153S mutation caused myeloid cell expansion, T cell cytopenia, and dysregulation of immune cell signaling. Unexpectedly, we observed only mild up-regulation of ISGs in STING N153S fibroblasts and splenocytes and STING N154S SAVI patient fibroblasts. STING N153S mice lacking IRF3 also developed lung disease, myeloid cell expansion, and T cell cytopenia. Thus, the SAVI-associated STING N153S mutation triggers IRF3-independent immune cell dysregulation and lung disease in mice.

Type I interferons in the pathogenesis and treatment of canine diseases

Type I interferons (IFNs) such as IFN-α, IFN-β, IFN-ε, IFN-κ, and IFN-ω represent cytokines, which are deeply involved in the regulation and activation of innate and adaptive immune responses. They possess strong antiviral, antiproliferative, and immunomodulatory activities allowing their use in the therapy of different viral diseases, neoplasms, and immune-mediated disorders, respectively. Initially, treatment strategies were based on nonspecific inducers of type I IFNs, which were soon replaced by different recombinant proteins. Drugs with type I IFNs as active agents are currently used in the treatment of hepatitis B and C virus infection, lymphoma, myeloid leukemia, renal carcinoma, malignant melanoma, and multiple sclerosis in humans. In addition, recombinant feline IFN-ω has been approved for the treatment of canine parvovirus, feline leukemia virus, and feline immunodeficiency virus infections. However, the role of type I IFNs in the pathogenesis of canine diseases remains largely undetermined so far, even though some share pathogenic mechanisms and clinical features with their human counterparts. This review summarizes the present knowledge of type I IFNs and down-stream targets such as Mx and 2',5'-oligoadenylate synthetase proteins in the pathogenesis of infectious and immune-mediated canine diseases. Moreover, studies investigating the potential use of type I IFNs in the treatment of canine lymphomas, melanomas, sarcomas, and carcinomas, canine distemper virus, parvovirus, and papillomavirus infections as well as immune-mediated keratoconjunctivitis sicca and atopic dermatitis are presented. A separate chapter is dedicated to the therapeutic potential of IFN-λ, a type III IFN, in canine diseases. However, further future studies are still needed to unravel the exact functions of the different subtypes of type I IFNs and their target genes in healthy and diseased dogs and the full potential action of type I IFNs as treatment strategy.

Spontaneous activation of a MAVS-dependent antiviral signaling pathway determines high basal interferon-β expression in cardiac myocytes

Viral myocarditis is a leading cause of sudden death in young adults as the limited turnover of cardiac myocytes renders the heart particularly vulnerable to viral damage. Viruses induce an antiviral type I interferon (IFN-α/β) response in essentially all cell types, providing an immediate innate protection. Cardiac myocytes express high basal levels of IFN-β to help pre-arm them against viral infections, however the mechanism underlying this expression remains unclear. Using primary cultures of murine cardiac and skeletal muscle cells, we demonstrate here that the mitochondrial antiviral signaling (MAVS) pathway is spontaneously activated in unstimulated cardiac myocytes but not cardiac fibroblasts or skeletal muscle cells. Results suggest that MAVS association with the mitochondrial-associated ER membranes (MAM) is a determinant of high basal IFN-β expression, and demonstrate that MAVS is essential for spontaneous high basal expression of IFN-β in cardiac myocytes and the heart. Together, results provide the first mechanism for spontaneous high expression of the antiviral cytokine IFN-β in a poorly replenished and essential cell type.

Residues F103 and M106 within the influenza A virus NS1 CPSF4-binding region regulate interferon-stimulated gene translation initiation

Influenza A virus (IAV) non-structural protein 1 (NS1) suppresses host innate immune responses by inhibiting type I interferon (IFN) production. We provide evidence that residues F103 and M106 in the CPSF4-binding domain of A/HK/1/68 [H3N2] NS1 contribute to post-transcriptional inhibition of antiviral IFN-stimulated genes (ISGs), thereby suppressing an antiviral type I IFN response. Recombinant (r) IAVs encoding F103L and M106I mutations in NS1 replicate to significantly lower viral titers in human A549 lung epithelial cells and primary type II alveolar cells. In A549 cells, rIAVs encoding these mutant NS1s induce higher levels of IFN-β production and are more sensitive to the antiviral effects of IFN-β treatment. qPCR characterization of polysomal mRNA, in the presence or absence of IFN-β treatment, identified a greater proportion of heavy polysome-associated ISGs including EIF2AK2, OAS1, and MxA in A549 cells infected with rIAVs encoding these CPSF4-binding mutant NS1s, in contrast to rIAV encoding wildtype NS1.

The Protective Role of Type I Interferons in the Gastrointestinal Tract

The immune system of the gastrointestinal (GI) tract manages the significant task of recognizing and eliminating pathogens while maintaining tolerance of commensal bacteria. Dysregulation of this delicate balance can be detrimental, resulting in severe inflammation, intestinal injury, and cancer. Therefore, mechanisms to relay important signals regulating cell growth and immune reactivity must be in place to support GI homeostasis. Type I interferons (IFN-I) are a family of pleiotropic cytokines, which exert a wide range of biological effects including promotion of both pro- and anti-inflammatory activities. Using animal models of colitis, investigations into the regulation of intestinal epithelium inflammation highlight the role of IFN-I signaling during fine modulation of the immune system. The intestinal epithelium of the gut guides the immune system to differentiate between commensal and pathogenic microbiota, which relies on intimate links with the IFN-I signal-transduction pathway. The current paradigm depicts an IFN-I-induced antiproliferative state in the intestinal epithelium enabling cell differentiation, cell maturation, and proper intestinal barrier function, strongly supporting its role in maintaining baseline immune activity and clearance of damaged epithelia or pathogens. In this review, we will highlight the importance of IFN-I in intestinal homeostasis by discussing its function in inflammation, immunity, and cancer.

Type-I-interferons in infection and cancer: Unanticipated dynamics with therapeutic implications

If there is a great new hope in the treatment of cancer, the immune system is it. Innate and adaptive immunity either promote or attenuate tumorigenesis and so can have opposing effects on the therapeutic outcome. Originally described as potent antivirals, Type-I interferons (IFNs) were quickly recognized as central coordinators of tumor-immune system interactions. Type-I-IFNs are produced by, and act on, both tumor and immune cells being either host-protecting or tumor-promoting. Here, we discuss Type-I-IFNs in infectious and cancer diseases highlighting their dichotomous role and raising the importance to deeply understand the underlying mechanisms so to reshape the way we can exploit Type-I-IFNs therapeutically.

Novel activities by ebolavirus and marburgvirus interferon antagonists revealed using a standardized in vitro reporter system

Filoviruses are highly lethal in humans and nonhuman primates, likely due to potent antagonism of host interferon (IFN) responses early in infection. Filoviral protein VP35 is implicated as the major IFN induction antagonist, while Ebola virus (EBOV) VP24 or Marburg virus (MARV) VP40 are known to block downstream IFN signaling. Despite progress elucidating EBOV and MARV antagonist function, those for most other filoviruses, including Reston (RESTV), Sudan (SUDV), Taï Forest (TAFV), Bundibugyo (BDBV) and Ravn (RAVV) viruses, remain largely neglected. Thus, using standardized vectors and reporter assays, we characterized activities by each IFN antagonist from all known ebolavirus and marburgvirus species side-by-side. We uncover noncanonical suppression of IFN induction by ebolavirus VP24, differing potencies by MARV and RAVV proteins, and intriguingly, weaker antagonism by VP24 of RESTV. These underlying molecular explanations for differential virulence in humans could guide future investigations of more-neglected filoviruses as well as treatment and vaccine studies.

Transcription factor Zeb2 regulates commitment to plasmacytoid dendritic cell and monocyte fate

Dendritic cells (DCs) and monocytes develop from a series of bone-marrow-resident progenitors in which lineage potential is regulated by distinct transcription factors. Zeb2 is an E-box-binding protein associated with epithelial-mesenchymal transition and is widely expressed among hematopoietic lineages. Previously, we observed that Zeb2 expression is differentially regulated in progenitors committed to classical DC (cDC) subsets in vivo. Using systems for inducible gene deletion, we uncover a requirement for Zeb2 in the development of Ly-6C^hi monocytes but not neutrophils, and we show a corresponding requirement for Zeb2 in expression of the M-CSF receptor in the bone marrow. In addition, we confirm a requirement for Zeb2 in development of plasmacytoid DCs but find that Zeb2 is not required for cDC2 development. Instead, Zeb2 may act to repress cDC1 progenitor specification in the context of inflammatory signals.

Bordetella pertussis outer membrane vesicle vaccine confers equal efficacy in mice with milder inflammatory responses compared to a whole-cell vaccine

The demand for improved pertussis vaccines is urgent due to the resurgence of whooping cough. A deeper understanding of the mode of action of pertussis vaccines is required to achieve this improvement. The vaccine-induced effects of a candidate outer membrane vesicle vaccine (omvPV) and a classical protective but reactogenic whole cell vaccine (wPV) were comprehensively compared in mice. The comparison revealed essential qualitative and quantitative differences with respect to immunogenicity and adverse effects for these vaccines. Both vaccines stimulated a mixed systemic Th1/Th2/Th17 response. Remarkably, omvPV evoked higher IgG levels, lower systemic pro-inflammatory cytokine responses and enhanced splenic gene expression than wPV. The omvPV-induced transcriptome revealed gene signatures of the IFN-signaling pathway, anti-inflammatory signatures that attenuate LPS responses, anti-inflammatory metabolic signatures, and IgG responses. Upon intranasal challenge, both immunized groups were equally efficient in clearing Bordetella pertussis from the lungs. This study importantly shows that immunization with omvPV provides a milder inflammatory responses but with equal protection to bacterial colonization and induction of protective antibody and Th1/Th17 type immune responses compared to wPV. These results emphasize the potential of omvPV as a safe and effective next-generation pertussis vaccine.

Human Immunodeficiency Virus-1 Impairs IFN-Alpha Production Induced by TLR-7 Agonist in Plasmacytoid Dendritic Cells

Plasmacytoid dendritic cells (pDCs) play an important role in innate immune response against viruses, mainly through interferon-α (IFN-α) secretion. Impaired IFN-α secretion has been observed in patients with acute human immunodeficiency virus type 1 (HIV-1) infection and the reasons for this impairment are still obscure. To know the grounds behind this situation, HIV-1 viral copy numbers similar to those found in primary HIV-1 infection were used to stimulate peripheral blood mononuclear cells (PBMCs) and pDCs in this study. Intracellular IFN-α production was seen as early as 2 h in pDCs with TLR-7 agonist (imiquimod) stimulation, but HIV-1 required 48 h to induce secretion of IFN-α in supernatants and it was 10 times less compared to imiquimod. Thus, it shows that HIV-1 delays and impairs IFN-α production from pDCs. Furthermore, the IFN-α inhibitory activity of HIV-1 was checked by stimulating PBMCs and pDCs with imiquimod either simultaneously with HIV-1 or after 2 h pre-exposure to HIV-1. Pre-exposure to HIV-1 resulted in significant reduction in IFN-α secretion by pDCs and PBMCs when compared to imiquimod alone. In addition, simultaneous stimulation of these populations with HIV-1 and imiquimod resulted in significant impairment in IFN-α production in pDCs but not in PBMCs. HIV-1 not only fails to induce IFN-α in adequate quantities but also inhibits IFN-α secretary capacity of pDCs. HIV-1 particles were found to bind CD303 receptor on pDC surface probably blocking initiation of cascade leading to IFN-α impairment. The understanding of the pathways that lead to this suppression may help in devising the HIV control strategies.

The Importance of Physiologically Relevant Cell Lines for Studying Virus-Host Interactions

Viruses interact intimately with the host cell at nearly every stage of replication, and the cell model that is chosen to study virus infection is critically important. Although primary cells reflect the phenotype of healthy cells in vivo better than cell lines, their limited lifespan makes experimental manipulation challenging. However, many tumor-derived and artificially immortalized cell lines have defects in induction of interferon-stimulated genes and other antiviral defenses. These defects can affect virus replication, especially when cells are infected at lower, more physiologically relevant, multiplicities of infection. Understanding the selective pressures and mechanisms underlying the loss of innate signaling pathways is helpful to choose immortalized cell lines without impaired antiviral defense. We describe the trials and tribulations we encountered while searching for an immortalized cell line with intact innate signaling, and how directed immortalization of primary cells avoids many of the pitfalls of spontaneous immortalization.

Persistent Cytomegalovirus Infection in Amniotic Membranes of the Human Placenta

Human cytomegalovirus (HCMV) is the leading viral cause of birth defects, including microcephaly, neurological deficits, hearing impairment, and vision loss. We previously reported that epithelial cells in amniotic membranes of placentas from newborns with intrauterine growth restriction and underlying congenital HCMV infection contain viral proteins in cytoplasmic vesicles. Herein, we immunostained amniotic membranes from 51 placentas from symptomatic and asymptomatic congenital infection with HCMV DNA in amniotic fluid and/or newborn saliva, intrauterine growth restriction, preterm deliveries, and controls. We consistently observed HCMV proteins in amniotic epithelial cells (AmEpCs) from infected placentas, sometimes with aberrant morphology. Primary AmEpCs isolated from mid-gestation placentas infected with pathogenic VR1814 proliferated and released infectious progeny for weeks, producing higher virus titers than late-gestation cells that varied by donor. In contrast to intact virion assembly compartments in differentiated retinal pigment epithelial cells, infected AmEpCs made dispersed multivesicular bodies. Primary AmEpCs and explants of amniochorionic membranes from mid-gestation placentas formed foci of infection, and interferon-β production was prolonged. Infected AmEpCs up-regulated anti-apoptotic proteins survivin and Bcl-x_L by mechanisms dependent and independent of the activated STAT3. Amniotic membranes naturally expressed both survivin and Bcl-x_L, indicating that fetal membranes could foster persistent viral infection. Our results suggest strengthening innate immune responses and reducing viral functions could suppress HCMV infection in the fetal compartment.

Identification of Two Subgroups of Type I IFNs in Perciforme Fish Large Yellow Croaker Larimichthys crocea Provides Novel Insights into Function and Regulation of Fish Type I IFNs

Like mammals, fish possess an interferon regulatory factor (IRF) 3/IRF7-dependent type I IFN responses, but the exact mechanism by which IRF3/IRF7 regulate the type I IFNs remains largely unknown. In this study, we identified two type I IFNs in the Perciforme fish large yellow croaker Larimichthys crocea, one of which belongs to the fish IFNd subgroup and the other is assigned to a novel subgroup of group I IFNs in fish, tentatively termed IFNh. The two IFN genes are constitutively expressed in all examined tissues, but with varied expression levels. Both IFN genes can be rapidly induced in head kidney and spleen tissues by polyinosinic–polycytidylic acid. The recombinant IFNh was shown to be more potent to trigger a rapid induction of the antiviral genes MxA and protein kinase R than the IFNd, suggesting that they may play distinct roles in regulating early antiviral immunity. Strikingly, IFNd, but not IFNh, could induce the gene expression of itself and IFNh through a positive feedback loop mediated by the IFNd-dependent activation of IRF3 and IRF7. Furthermore, our data demonstrate that the induction of IFNd can be enhanced by the dimeric formation of IRF3 and IRF7, while the IFNh expression mainly involves IRF3. Taken together, our findings demonstrate that the IFN responses are diverse in fish and are likely to be regulated by distinct mechanisms.

Protein phosphatase 1 abrogates IRF7-mediated type I IFN response in antiviral immunity

Interferon (IFN) regulatory factor 7 (IRF7) plays a key role in the production of IFN-α in response to viral infection, and phosphorylation at IRF7 C-terminal serine sites is prelude to its function. However, phosphatases that negatively regulate IRF7 phosphorylation and activity have not been reported. In this study, we have identified a conserved protein phosphatase 1 (PP1)-binding motif in human and mouse IRF7 proteins, and shown that PP1 physically interacts with IRF7. Exogenous expression of PP1 subunits (PP1α, β, or γ) ablates IKKε-stimulated IRF7 phosphorylation and dramatically attenuates IRF7 transcriptional activity. Inhibition of PP1 activity significantly increases IRF7 phosphorylation and IRF7-mediated IFN-α production in response to Newcastle disease virus (NDV) infection or Toll-like receptor 7 (TLR7) challenge, leading to impaired viral replication. In addition, IFN treatment, TLR challenges and viral infection induce PP1 expression. Our findings disclose for the first time a pivotal role for PP1 in impeding IRF7-mediated IFN-α production in host immune responses.

Type I Interferon-Mediated Induction of Antiviral Genes and Proteins Fails to Protect Cells from the Cytopathic Effects of Sendai Virus Infection

Sendai virus (SeV), a murine paramyxovirus, has been used to study the induction of type I interferon (IFN) subtypes in robust quantities. Few studies have measured whether the IFN that SeV induces actually fulfills its intended purpose of interfering with virus-mediated effects in the cells in which it is produced. We determined the effects of IFN on SeV-mediated cytopathic effects (CPE) and the ability of IFN to protect against virus infection. SeV-induced biologically active IFN resulted in Jak/STAT activation and the production of a number of interferon-stimulated genes (ISGs). However, these responses did not inhibit SeV replication or CPE. This observation was not due to SeV effects on canonical IFN signaling. Furthermore, pretreating cells with type I IFN and establishing an antiviral state before infection did not mediate SeV effects. Therefore, the induction of canonical IFN signaling pathways and ISGs does not always confer protection against the IFN-inducing virus. Because type I IFNs are approved to treat various infections, our findings suggest that typical markers of IFN activity may not be indicative of a protective antiviral response and should not be used alone to determine whether an antiviral state against a particular virus is achieved.

The Type I Interferon-IRF7 Axis Mediates Transcriptional Expression of Usp25 Gene

Viral infection or lipopolysaccharide (LPS) treatment induces expression of a large array of genes, the products of which play a critical role in host antipathogen immunity and inflammation. We have previously reported that the expression of ubiquitin-specific protease 25 (USP25) is significantly up-regulated after viral infection or LPS treatment, and this is essential for innate immune signaling. However, the mechanism behind this phenomenon is unclear. In this study, we found that viral infection-induced up-regulation of Usp25 is diminished in cells lacking interferon regulatory factor 7 (IRF7) or interferon α receptor 1 (IFNAR1) but not p65. Sendai virus- or type I interferon-induced up-regulation of Usp25 requires de novo protein synthesis of IRF7. Furthermore, IRF7 directly binds to the two conserved IRF binding sites on the USP25 promoter to drive transcription of Usp25, and mutation of these two sites abolished Sendai virus-induced IRF7-mediated activation of the USP25 promoter. Our study has uncovered a previously unknown mechanism by which viral infection or LPS induces up-regulation of USP25.

MicroRNA-223 Promotes Type I Interferon Production in Antiviral Innate Immunity by Targeting Forkhead Box Protein O3 (FOXO3)

Effective recognition of viral infection and subsequent triggering of antiviral innate immune responses are essential for the host antiviral defense, which is tightly regulated by multiple regulators, including microRNAs. Previous reports have shown that some microRNAs are induced during virus infection and participate in the regulation of the innate antiviral response. However, whether the type I IFN response is regulated by miR-223 is still unknown. Here, we reported that vesicular stomatitis virus (VSV) infection induced significant up-regulation of miR-223 in murine macrophages. We observed that miR-223 overexpression up-regulated type I IFN expression levels in VSV-infected macrophages. We also demonstrated that miR-223 directly targets FOXO3 to regulate the type I IFN production. Furthermore, type I IFN, which is triggered by VSV infection, is responsible for the up-regulation of miR-223, thus forming a positive regulatory loop for type I IFN production. Our results uncovered a novel mechanism of miR-223-mediated regulation of type I IFN production in the antiviral innate immunity for the first time.

ESX-1 exploits type I IFN-signalling to promote a regulatory macrophage phenotype refractory to IFNγ-mediated autophagy and growth restriction of intracellular mycobacteria

The ability of macrophages to eradicate intracellular pathogens is normally greatly enhanced by IFNγ, a cytokine produced mainly after onset of adaptive immunity. However, adaptive immunity is unable to provide sterilizing immunity against mycobacteria, suggesting that mycobacteria have evolved virulence strategies to inhibit the bactericidal effect of IFNγ-signalling in macrophages. Still, the host-pathogen interactions and cellular mechanisms responsible for this feature have remained elusive. We demonstrate that the ESX-1 type VII secretion systems of Mycobacterium tuberculosis and Mycobacterium  marinum exploit type I IFN-signalling to promote an IL-12(low) /IL-10(high) regulatory macrophage phenotype characterized by secretion of IL-10, IL-27 and IL-6. This mechanism had no impact on intracellular growth in the absence of IFNγ but suppressed IFNγ-mediated autophagy and growth restriction, indicating that the regulatory phenotype extends to function. The IFNγ-refractory phenotype was partly mediated by IL-27-signalling, establishing functional relevance for this downstream cytokine. These findings identify a novel macrophage-modulating function for the ESX-1 secretion system that may contribute to suppress the efficacy of adaptive immunity and provide mechanistic insight into the antagonistic cross talk between type I IFNs and IFNγ in mycobacterial infection.

The emerging role of interferon regulatory factor 9 in the antiviral host response and beyond

The host response to viral infections relies on tightly regulated and intricate signaling pathways involving type I interferons (IFN-Is). The IFN-Is mediate their antiviral effects predominantly through a signaling factor complex that comprises the transcription factors, interferon regulatory factor 9 (IRF9) and the signal transducers and activators of transcription (STAT) 1 and STAT2. While STAT1 and STAT2 have been studied extensively, the biological significance of IRF9 is only beginning to emerge. Recent studies have revealed a unique role for IRF9 as a conductor of the cellular responses to IFN-Is. Intriguingly, novel roles for IRF9 outside of the antiviral response are also being identified. Thus IRF9 may have a more extensive influence on cellular processes than previously recognized, ranging from antiviral immune responses to oncogenesis and gut homeostasis. In this review, we will focus on the distinct and emerging roles of IRF9 in the antiviral host response and beyond.

Amplified RLR signaling activation through an interferon-stimulated gene-endoplasmic reticulum stress-mitochondrial calcium uniporter protein loop

Type I interferon (IFN-I) is critical for a host against viral and bacterial infections via induction of hundreds of interferon-stimulated genes (ISGs), but the mechanism underlying the regulation of IFN-I remains largely unknown. In this study, we first demonstrate that ISG expression is required for optimal IFN-β levels, an effect that is further enhanced by endoplasmic reticulum (ER) stress. Furthermore, we identify mitochondrial calcium uniporter protein (MCU) as a mitochondrial antiviral signaling protein (MAVS)-interacting protein that is important for ER stress induction and amplified MAVS signaling activation. In addition, by performing an ectopic expression assay to screen a library of 117 human ISGs for effects on IFN-β levels, we found that tumor necrosis factor receptor 1 (TNFR1) significantly increases IFN-β levels independent of ER stress. Altogether, our findings suggest that MCU and TNFR1 are involved in the regulation of RIG-I-like receptors (RLR) signaling.

Ablation of Type-1 IFN Signaling in Hematopoietic Cells Confers Protection Following Traumatic Brain Injury

Type-1 interferons (IFNs) are pleiotropic cytokines that signal through the type-1 IFN receptor (IFNAR1). Recent literature has implicated the type-1 IFNs in disorders of the CNS. In this study, we have investigated the role of type-1 IFNs in neuroinflammation following traumatic brain injury (TBI). Using a controlled cortical impact model, TBI was induced in 8- to 10-week-old male C57BL/6J WT and IFNAR1^−/− mice and brains were excised to study infarct volume, inflammatory mediator release via quantitative PCR analysis and immune cell profile via immunohistochemistry. IFNAR1^−/− mice displayed smaller infarcts compared with WT mice after TBI. IFNAR1^−/− mice exhibited an altered anti-inflammatory environment compared with WT mice, with significantly reduced levels of the proinflammatory mediators TNFα, IL-1β and IL-6, an up-regulation of the anti-inflammatory mediator IL-10 and an increased activation of resident and peripheral immune cells after TBI. WT mice injected intravenously with an anti-IFNAR1 blocking monoclonal antibody (MAR1) 1 h before, 30 min after or 30 min and 2 d after TBI displayed significantly improved histological and behavioral outcome. Bone marrow chimeras demonstrated that the hematopoietic cells are a peripheral source of type-1 IFNs that drives neuroinflammation and a worsened TBI outcome. Type-1 IFN mRNA levels were confirmed to be significantly altered in human postmortem TBI brains. Together, these data demonstrate that type-1 IFN signaling is a critical pathway in the progression of neuroinflammation and presents a viable therapeutic target for the treatment of TBI.

Cloning and expression analysis of interferon regulatory factor 7 in the Pacific cod, Gadus macrocephalus

Interferon regulatory factor 7 (IRF7) plays an important role in regulating the response of type I interferon (IFN) to viral infection. To understand the mechanisms underlying immune reactions in the Pacific cod, Gadus macrocephalus, the gene encoding G. macrocephalus IRF7 was cloned and characterized. The cDNA of G. macrocephalus IRF7 was also cloned and sequenced. A cDNA sequence of 2032 bp was assembled using polymerase chain reaction (PCR) products. It contains an open reading frame of 1323 bp in length, which encoded a 440-amino acid polypeptide that comprised a DNA-binding domain (DBD), an IRF association domain (IAD), and a serine-rich domain (SRD). In the DBD, the tryptophan cluster consisted of only four tryptophans, which is a unique characteristic in fish IRF7. The mRNA of IRF7 was detected in various tissues, including in the spleen, thymus, kidney, intestine, and gills, using relative quantification PCR (R-qPCR). Dynamic expression of IRF7 was observed in larvae throughout post-hatching (ph) development, with the highest level detected at day of ph (dph) 25. Response to immune stimulation was examined by challenging larvae with polyriboinosinic polyribocytidylic acid (pIC) to mimic viral infection and elicit an immune reaction. R-qPCR revealed that the expression of IRF7 significantly increased in pIC-treated groups relative to that in the control groups, in a time-dependent manner, with peak responses at 48 and 72 h after pIC-treatment. These results show that IRF7 is expressed in various tissues of adult fish and larvae and is sensitive to viral infection, suggesting that it plays a role in antiviral immune defense in G. macrocephalus.

OASL1 deficiency promotes antiviral protection against genital herpes simplex virus type 2 infection by enhancing type I interferon production

Type I interferon (IFN) interferes with virus replication, promotes antiviral responses, and controls innate and adaptive immune responses to certain viruses. Recently, we reported that 2’–5’ oligoadenylate synthetase-like 1 (OASL1) negatively regulates type I IFN production by inhibiting the translation of the type I IFN-regulating master transcription factor, IRF7. Notably, while OASL1-deficient mice induce robust production of type I IFN and are resistant to systemic viral infection, the effects of OASL1 during localized viral infection has not been studied. To this end, we investigated the role of OASL1 during mucosal HSV-2 infection of the genital tract. Oasl1^−/− mice exhibited better survival rates than wild type (WT) mice following intravaginal HSV-2 infection, and suppressed virus replication more efficiently despite comparable recruitment of effector immune cells. Moreover, Ly6C^high monocytes, and not pDCs or other cell types, displayed enhanced production of type I IFNs in Oasl1^−/− mice in response to HSV-2 infection. Furthermore, cytotoxic T cell responses including IFN-γ production were accelerated in Oasl1^−/− mice after mucosal HSV-2 infection. Collectively, these results demonstrate that OASL1 deficiency promotes antiviral immunity against local mucosal viral infection and suggest that OASL1 could be a therapeutic target for treatment of HSV-2 infection of the genital mucosa.

Structural Design of Engineered Costimulation Determines Tumor Rejection Kinetics and Persistence of CAR T Cells

T cell engineering is a powerful means to rapidly generate anti-tumor T cells. The costimulatory properties of second-generation chimeric antigen receptors (CARs) determine the overall potency of adoptively transferred T cells. Using an in vivo "stress test" to challenge CD19-targeted T cells, we studied the functionality and persistence imparted by seven different CAR structures providing CD28 and/or 4-1BB costimulation. One configuration, which uses two signaling domains (CD28 and CD3ζ) and the 4-1BB ligand, provided the highest therapeutic efficacy, showing balanced tumoricidal function and increased T cell persistence accompanied by an elevated CD8/CD4 ratio and decreased exhaustion. Remarkably, induction of the IRF7/IFNβ pathway was required for optimal anti-tumor activity. Thus, 1928z-41BBL T cells possess strikingly potent intrinsic and immunomodulatory qualities.

Bropirimine inhibits osteoclast differentiation through production of interferon-β

Bropirimine is a synthetic agonist for toll-like receptor 7 (TLR7). In this study, we investigated the effects of bropirimine on differentiation and bone-resorbing activity of osteoclasts in vitro. Bropirimine inhibited osteoclast differentiation of mouse bone marrow-derived macrophages (BMMs) induced by receptor activator of nuclear factor κB ligand (RANKL) in a concentration-dependent manner. Furthermore, it suppressed the mRNA expression of nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1), a master transcription factor for osteoclast differentiation, without affecting BMM viability. Bropirimine also inhibited osteoclast differentiation induced in co-cultures of mouse bone marrow cells (BMCs) and mouse osteoblastic UAMS-32 cells in the presence of activated vitamin D3. Bropirimine partially suppressed the expression of RANKL mRNA in UAMS-32 cells induced by activated vitamin D3. Finally, the anti-interferon-β (IFN-β) antibody restored RANKL-dependent differentiation of BMMs into osteoclasts suppressed by bropirimine. These results suggest that bropirimine inhibits differentiation of osteoclast precursor cells into osteoclasts via TLR7-mediated production of IFN-β.

Virus Multiplicity of Infection Affects Type I Interferon Subtype Induction Profiles and Interferon-Stimulated Genes

Type I interferons (IFNs) are induced upon viral infection and important mediators of innate immunity. While there is 1 beta interferon (IFN-β) protein, there are 12 different IFN-α subtypes. It has been reported extensively that different viruses induce distinct patterns of IFN subtypes, but it has not been previously shown how the viral multiplicity of infection (MOI) can affect IFN induction. In this study, we discovered the novel finding that human U937 cells infected with 2 different concentrations of Sendai virus (SeV) induce 2 distinct type I IFN subtype profiles. Cells infected at the lower MOI induced more subtypes than cells infected at the higher MOI. We found that this was due to the extent of signaling through the IFN receptor (IFNAR). The cells infected at the lower viral MOI induced the IFNAR2-dependent IFN-α subtypes 4, 6, 7, 10, and 17, which were not induced in cells infected at higher virus concentrations. IFN-β and IFN-α1, -2, and -8 were induced in an IFNAR-independent manner in cells infected at both virus concentrations. IFN-α5, -14, -16, and -21 were induced in an IFNAR-dependent manner in cells infected at lower virus concentrations and in an IFNAR-independent manner in cells infected at higher virus concentrations. These differences in IFN subtype profiles in the 2 virus concentrations also resulted in distinct interferon-stimulated gene induction. These results present the novel finding that different viral MOIs differentially activate JAK/STAT signaling through the IFNAR, which greatly affects the profile of IFN subtypes that are induced.

IMPORTANCE

Type I IFNs are pleiotropic cytokines that are instrumental in combating viral diseases. Understanding how the individual subtypes are induced is important in developing strategies to block viral replication. Many studies have reported that different viruses induce distinct type I IFN subtype profiles due to differences in the way viruses are sensed in different cell types. However, we report in our study the novel finding that the amount of virus used to infect a system can also affect which type I IFN subtypes are induced due to the extent of activation of certain signaling pathways. These distinct IFN subtype profiles in cells infected at different MOIs are correlated with differences in interferon-stimulated gene induction, indicating that the same virus can induce distinct antiviral responses depending on the MOI. Because type I IFNs are used as therapeutic agents to treat viral diseases, understanding their antiviral mechanisms can enhance clinical treatments.

RNAseq expression analysis of resistant and susceptible mice after influenza A virus infection identifies novel genes associated with virus replication and important for host resistance to infection

Background

The host response to influenza A infections is strongly influenced by host genetic factors. Animal models of genetically diverse mouse strains are well suited to identify host genes involved in severe pathology, viral replication and immune responses. Here, we have utilized a dual RNAseq approach that allowed us to investigate both viral and host gene expression in the same individual mouse after H1N1 infection.

Results

We performed a detailed expression analysis to identify (i) correlations between changes in expression of host and virus genes, (ii) host genes involved in viral replication, and (iii) genes showing differential expression between two mouse strains that strongly differ in resistance to influenza infections. These genes may be key players involved in regulating the differences in pathogenesis and host defense mechanisms after influenza A infections. Expression levels of influenza segments correlated well with the viral load and may thus be used as surrogates for conventional viral load measurements. Furthermore, we investigated the functional role of two genes, Reg3g and Irf7, in knock-out mice and found that deletion of the Irf7 gene renders the host highly susceptible to H1N1 infection.

Conclusions

Using RNAseq analysis we identified novel genes important for viral replication or the host defense. This study adds further important knowledge to host-pathogen-interactions and suggests additional candidates that are crucial for host susceptibility or survival during influenza A infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1867-8) contains supplementary material, which is available to authorized users.

Ribavirin Contributes to Hepatitis C Virus Suppression by Augmenting pDC Activation and Type 1 IFN Production

Ribavirin is used as a component of combination therapies for the treatment of chronic hepatitis C virus (HCV) infection together with pegylated interferon and/or direct-acting antiviral drugs. Its mechanism of action, however, is not clear. Direct antiviral activity and immunomodulatory functions have been implicated. Plasmacytoid dendritic cells (pDCs) are the principal source of type 1 interferon during viral infection. The interaction of pDCs with HCV-infected hepatocytes is the subject of intense recent investigation, but the effect of ribavirin on pDC activation has not been evaluated. In this study we showed that ribavirin augments toll-like receptors 7 and 9-mediated IFNα/β expression from pDCs and up-regulated numerous interferon-stimulated genes. Using the H77S.3 HCV infection and replication system, we showed that ribavirin enhanced the ability of activated pDCs to inhibit HCV replication, correlated with elevated induction of IFNα. Our findings provide novel evidence that ribavirin contributes to HCV inhibition by augmenting pDCs-derived type 1 IFN production.

Secondary structure of the Irf7 5'-UTR, analyzed using SHAPE (selective 2'-hydroxyl acylation analyzed by primer extension)

OASL1 is a member of the 2’-5’-oligoadenylate synthetase (OAS) family and promotes viral clearance by activating RNase L. OASL1 interacts with the 5’-untranslated region (UTR) of interferon regulatory factor 7 (Irf7) and inhibits its translation. To identify the secondary structure required for OASL1 binding, we examined the 5’-UTR of the Irf7 transcript using “selective 2’-hydroxyl acylation analyzed by primer extension” (SHAPE). SHAPE takes advantage of the selective acylation of residues in single-stranded regions by 1-methyl-7-nitroisatoic anhydride (1M7). We found five major acylation sites located in, or next to, predicted single-stranded regions of the Irf7 5’-UTR. These results demonstrate the involvement of the stem structure of the Irf7 5’-UTR in the regulation of Irf7 translation, mediated by OASL1. [BMB Reports 2014; 47(10): 558-562]

Small molecule inhibits activity of scavenger receptor A: Lead identification and preliminary studies

Scavenger receptor A (SRA) has been implicated in the processes of tumor invasion and acts as an immunosuppressor during therapeutic cancer vaccination. Pharmacological inhibition of SRA function thus holds a great potential to improve treatment outcome of cancer therapy. Macromolecular natural product sennoside B was recently shown to block SRA function. Here we report the identification and characterization of a small molecule SRA inhibitor rhein. Rhein, a deconstructed analog of sennoside B, reversed the suppressive activity of SRA in dendritic cell-primed T cell activation, indicated by transcription activation of il2 gene and production of IL-2. Rhein also inhibited SRA ligand polyinosinic:polycytidylic acid (poly(I:C)) induced activation of transcriptional factors, including interferon regulatory factor 3 (IRF3) and signal transducer and activator of transcription 1 (STAT1). Additionally, this newly identified lead compound was docked into the homology models of the SRA cysteine rich domain to gain insights into its interaction with the receptor. It was then found that rhein can favorably interact with SRA cysteine rich domain. Collectively, rhein, being the first identified small molecule inhibitors for SRA, warrants further structure-activity relationship studies, which may lead to development of novel pharmacological intervention for cancer therapy.

Suppression of interferon β gene transcription by inhibitors of bromodomain and extra-terminal (BET) family members

We have found that interferon production is suppressed by compounds that prevent bromodomains from interacting with acetylated histones at the interferon gene promoter. This is a new way in which interferon production is regulated to combat bacterial or viral infection.

PLK (Polo-like kinase) inhibitors, such as BI-2536, have been reported to suppress IFNB (encoding IFNβ, interferon β) gene transcription induced by ligands that activate TLR3 (Toll-like receptor 3) and TLR4. In the present study, we found that BI-2536 is likely to exert this effect by preventing the interaction of the transcription factors IRF3 (interferon-regulatory factor 3) and c-Jun with the IFNB promoter, but without affecting the TBK1 {TANK [TRAF (tumour-necrosis-factor-receptor-associated factor)-associated nuclear factor κB activator]-binding kinase 1}-catalysed phosphorylation of IRF3 at Ser³⁹⁶, the dimerization and nuclear translocation of IRF3 or the phosphorylation of c-Jun and ATF2 (activating transcription factor 2). Although BI-2536 inhibits few other kinases tested, it interacts with BET (bromodomain and extra-terminal) family members and displaces them from acetylated lysine residues on histones. We found that BET inhibitors that do not inhibit PLKs phenocopied the effect of BI-2536 on IFNB gene transcription. Similarly, BET inhibitors blocked the interaction of IRF5 with the IFNB promoter and the secretion of IFNβ induced by TLR7 or TLR9 ligands in the human plasmacytoid dendritic cell line GEN2.2, but without affecting the nuclear translocation of IRF5. We found that the BET family member BRD4 (bromodomain-containing protein 4) was associated with the IFNB promoter and that this interaction was enhanced by TLR3- or TLR4-ligation and prevented by BI-2536 and other BET inhibitors. Our results establish that BET family members are essential for TLR-stimulated IFNB gene transcription by permitting transcription factors to interact with the IFNB promoter. They also show that the interaction of the IFNB promoter with BRD4 is regulated by TLR ligation and that BI-2536 is likely to suppress IFNB gene transcription by targeting BET family members.

Limited specificity of IRF3 and ISGF3 in the transcriptional innate-immune response to double-stranded RNA

The innate immune response is largely initiated by pathogen-responsive activation of the transcription factor IRF3. Among other target genes, IRF3 controls the expression of IFN-β, which triggers the activation of the transcription factor ISGF3 via the IFNAR. IRF3 and ISGF3 have been reported to control many of the same target genes and together, control the antimicrobial innate-immune program; however, their respective contributions and specificities remain unclear. Here, we used genomic technologies to characterize their specificity in terms of their physical DNA-binding and genetic function. With the use of ChiP-seq and transcriptomic measurements in WT versus ifnar(-/-) versus ifnar(-/-)irf3(-/-) macrophages responding to intracellular dsRNA, we confirmed the known ISGF3 DNA-binding motif and further specified a distinct IRF3 consensus sequence. The functional specificity of IRF3 is particularly pronounced in cytokine/chemokine regulation; yet, even in the control of IFN-β, that specificity is not absolute. By mathematically modeling IFN-β production within an abstracted tissue layer, we find that IRF3 versus ISGF3 specificity may be critical to limiting IFN-β production and ISGF3 activation, temporally and spatially, but that partial overlap in their specificity is tolerable and may enhance the effectiveness of the innate-immune response.

Negative feedback contributes to the stochastic expression of the interferon-β gene in virus-triggered type I interferon signaling pathways

Type I interferon (IFN) signaling pathways play an essential role in the defense against early viral infections; however, the diverse and intricate molecular mechanisms of virus-triggered type I IFN responses are still poorly understood. In this study, we analyzed and compared two classes of models i.e., deterministic ordinary differential equations (ODEs) and stochastic models to elucidate the dynamics and stochasticity of type I IFN signaling pathways. Bifurcation analysis based on an ODE model reveals that the system exhibits a bistable switch and a one-way switch at high or low levels when the strengths of the negative and positive feedbacks are tuned. Furthermore, we compared the stochastic simulation results under the Master and Langevin equations. Both of the stochastic equations generate the bistable switch phenomenon, and the distance between two stable states are smaller than normal under the simulation of the Langevin equation. The quantitative computations also show that a moderate ratio between positive and negative feedback strengths is required to ensure a reliable switch between the different IFN concentrations that regulate the immune response. Moreover, we propose a multi-state stochastic model based on the above deterministic model to describe the multi-cellular system coupled with the diffusion of IFNs. The perturbation and inhibition analysis showed that the positive feedback, as well as noises, has little effect on the stochastic expression of IFNs, but the negative feedback of ISG56 on the activation of IRF7 has a great influence on IFN stochastic expression. Together, these results reveal that positive feedback stabilizes IFN gene expression, and negative feedback may be the main contribution to the stochastic expression of the IFN gene in the virus-triggered type I IFN response. These findings will provide new insight into the molecular mechanisms of virus-triggered type I IFN signaling pathways.