I Interferon Activity Research Articles

Type I interferonopathies--an expanding disease spectrum of immunodysregulation.

Type I interferons (IFNs) play a central role in the immune defense against viral infections. Type I IFN signaling is activated by pattern recognition receptors upon sensing of viral nucleic acids and induces antiviral programs through modulation of innate and adaptive immune responses. Type I interferonopathies comprise a heterogenous group of genetically determined diseases that are characterized by inappropriate activation of type I IFN. While their phenotypic spectrum is broad, ranging from severe neurological impairment to mild cutaneous disease, systemic autoinflammation, and autoimmunity are commonly shared signs of type I interferonopathies. Although the mechanisms underlying various disease phenotypes associated with inappropriate type I IFN activation have yet to be fully elucidated, our current understanding of the molecular pathogenesis of type I interferonopathies has provided a set of candidate molecules that can be interrogated in search of targeted therapies.

Endothelial progenitor cell phenotype and function are impaired in childhood-onset systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is characterized by increased cardiovascular risk in adult-onset and childhood-onset SLE. Type I interferons (IFNs) appear to play a prominent role in premature vascular damage in adult-onset SLE, at least in part, by inducing impairments in the phenotype and function of endothelial progenitor cells (EPCs), thereby hampering vascular repair. It is not clear whether EPC dysfunction is present in childhood-onset SLE in association with a type I IFN signature. The phenotype and numbers of EPCs were quantified in patients with childhood-onset SLE, patients with juvenile idiopathic arthritis (JIA), and matched healthy control subjects. In a separate cohort of patients with childhood-onset SLE, markers of subclinical atherosclerosis and endothelial dysfunction were quantified using standardized protocols and analyzed for associations with serum type I IFN activity. EPC numbers and function were significantly decreased in patients with childhood-onset SLE compared with patients with JIA and healthy control subjects. Serum from patients with childhood-onset SLE impaired differentiation of EPCs into mature endothelial cells in healthy controls, and this effect was blocked by inhibition of the type I IFN pathway. Type I IFN activity in serum was not significantly associated with subclinical atherosclerosis and endothelial function in patients with childhood-onset SLE. As in adult-onset SLE, childhood-onset SLE is characterized by phenotypic and functional EPC abnormalities, which are likely triggered by type I IFNs. Although cross-sectional analysis revealed no global association between type I IFN signatures and vascular measures of subclinical atherosclerosis, longitudinal assessments are needed to evaluate whether progression of vascular damage in patients with childhood-onset SLE is associated with type I IFNs, as observed in patients with adult-onset SLE.

Type I Interferon-Mediated Skewing of the Serotonin Synthesis Is Associated with Severe Disease in Systemic Lupus Erythematosus

Serotonin, a highly pro-inflammatory molecule released by activated platelets, is formed by tryptophan. Tryptophan is also needed in the production of kynurenine, a process mediated by the type I interferon (IFN)-regulated rate-limiting enzyme indoleamine 2,3-dioxygenase (IDO). The aim of this study was to investigate levels of serotonin in patients with the autoimmune disease systemic lupus erythematosus (SLE), association to clinical phenotype and possible involvement of IDO in regulation of serotonin synthesis. Serotonin levels were measured in serum and plasma from patients with SLE (n=148) and healthy volunteers (n=79) by liquid chromatography and ELISA, as well as intracellularly in platelets by flow cytometry. We found that SLE patients had decreased serotonin levels in serum (p=0.01) and platelets (p<0.0001) as compared to healthy individuals. SLE patients with ongoing type I IFN activity, as determined by an in-house reporter assay, had decreased serum levels of serotonin (p=0.0008) as well as increased IDO activity (p<0.0001), as determined by the kynurenine/tryptophan ratio measured by liquid chromatography. Furthermore, SLE sera induced IDO expression in WISH cells in a type I IFN-dependent manner (p=0.008). Also platelet activation contributed to reduce overall availability of serotonin levels in platelets and serum (p<0.05). Decreased serum serotonin levels were associated with severe SLE with presence of anti-dsDNA antibodies and nephritis. In all, reduced serum serotonin levels in SLE patients were related to severe disease phenotype, including nephritis, suggesting involvement of important immunopathological processes. Further, our data suggest that type I IFNs, present in SLE sera, are able to up-regulate IDO expression, which may lead to decreased serum serotonin levels.

Type I interferon response is delayed in human astrovirus infections.

Type I interferon (IFN) activation and its subsequent effects are important in the response to viral infections. Here we show that human astroviruses (HAstVs), which are important agents of acute gastroenteritis in children, induce a mild and delayed IFN response upon infecting CaCo-2 cells. Although IFN-β mRNA is detected within infected cells and supernatant from infected cells show antiviral activity against the replication of other well-known IFN-sensitive viruses, these responses occur at late stages of infection once genome replication has taken place. On the other hand, HAstV replication can be partially reduced by the addition of exogenous IFN, and inhibition of IFN activation by BX795 enhances viral replication, indicating that HAstVs are IFN-sensitive viruses. Finally, different levels of IFN response were observed in cells infected with different HAstV mutants with changes in the hypervariable region of nsP1a/4, suggesting that nsP1a/4 genotype may potentially have clinical implications due to its correlation with the viral replication phenotype and the antiviral responses induced within infected cells.

RIG-I specifically mediates group II type I IFN activation in nervous necrosis virus infected zebrafish cells

The type I interferon (IFN) response has been shown to be crucial for the survival of zebrafish larvae infected with nervous necrosis virus (NNV). Teleost type I IFNs can be divided into two groups, based on their cysteine content. While teleost group I IFNs have been extensively studied in terms of their regulation and anti-viral properties, the characteristics of teleost group II IFNs have been relatively unexplored. In this study, we describe the mechanism by which group II IFNs are activated in response to NNV infection in a zebrafish cell line, by focusing on the relationship between type I IFNs and pattern recognition receptors. Expression profile analysis of infected cells by microarray and qPCR revealed signaling activation of two pattern recognition receptors (PRRs): RIG-I like receptors (RLRs) and MyD88-dependent Toll-like receptors (TLRs). Knockdown of retinoic acid-inducible gene I (RIG-I) specifically repressed induction of group II IFNs (IFNϕ2, IFNϕ3) by NNV infection. Furthermore, Ingenuity Pathway Analysis (IPA) was used to demonstrate that RIG-I knockdown results in down-regulation of the inflammatory response in NNV-infected cells. Taken together, our results indicate that RIG-I plays an essential role in zebrafish group II type I IFN induction and the inflammatory response to NNV infection.

Higher antiviral response of RIG-I through enhancing RIG-I/MAVS-mediated signaling by its long insertion variant in zebrafish

As an intracellular pattern recognition receptor (PRR), the retinoic acid-inducible gene-I (RIG-I) is responsible for the recognition of cytosolic viral nucleic acids and the production of type I interferons (IFNs). In the present study, an insertion variant of RIG-I with 38 amino acids inserted in the N-terminal CARD2 domain, as well as the typical type, named as RIG-Ia and RIG-Ib respectively were identified in zebrafish. RIG-Ia and RIG-Ib were all up-regulated following the infection of a negative ssRNA virus, the Spring Viremia of Carp Virus (SVCV), and an intracellular Gram-negative bacterial pathogen Edwardsiella tarda, indicating the RLR may have a role in the recognition of both viruses and bacteria. The over-expression of RIG-Ib in cultured fish cells resulted in significant increase in type I IFN promoter activity, and in protection against SVCV infection, whereas the over-expression of RIG-Ia had no direct effect on IFN activation nor antiviral response. Furthermore, it was revealed that both RIG-Ia and RIG-Ib were associated with the downstream molecular mitochondrial antiviral signaling protein, MAVS, and interestingly RIG-Ia when co-transfected with RIG-Ib or MAVS, induced a significantly higher level of type I IFN promoter activity and the expression level of Mx and IRF7, implying that the RIG-Ia may function as an enhancer in the RIG-Ib/MAVS-mediated signaling pathway.

Plasma levels of galectin-3-binding protein reflect type I interferon activity and are increased in patients with systemic lupus erythematosus

ObjectiveSimple measures of type I interferon (IFN) activity constitute highly attractive biomarkers in systemic lupus erythematosus (SLE). We explore galectin-3-binding protein (G3BP) as a novel measure of type I IFN...

The exonuclease domain of Lassa virus nucleoprotein is involved in antigen-presenting-cell-mediated NK cell responses.

Lassa virus is an Old World Arenavirus which causes Lassa hemorrhagic fever in humans, mostly in West Africa. Lassa fever is an important public health problem, and a safe and effective vaccine is urgently needed. The infection causes immunosuppression, probably due to the absence of activation of antigen-presenting cells (dendritic cells and macrophages), low type I interferon (IFN) production, and deficient NK cell function. However, a recombinant Lassa virus carrying D389A and G392A substitutions in the nucleoprotein that abolish the exonuclease activity and IFN activation loses its inhibitory activity and induces strong type I IFN production by dendritic cells and macrophages. We show here that during infection by this mutant Lassa virus, antigen-presenting cells trigger efficient human NK cell responses in vitro, including production of IFN-γ and cytotoxicity. NK cell activation involves close contact with both antigen-presenting cells and soluble factors. We report that infected dendritic cells and macrophages express the NKG2D ligands major histocompatibility complex (MHC) class I-related chains A and B and that they may produce interleukin-12 (IL-12), IL-15, and IL-18, all involved in NK cell functions. NK cell degranulation is significantly increased in cocultures, suggesting that NK cells seem to kill infected dendritic cells and macrophages. This work confirms the inhibitory function of Lassa virus nucleoprotein. Importantly, we demonstrate for the first time that Lassa virus nucleoprotein is involved in the inhibition of antigen-presenting cell-mediated NK cell responses. The pathogenesis and immune responses induced by Lassa virus are poorly known. Recently, an exonuclease domain contained in the viral nucleoprotein has been shown to be able to inhibit the type I IFN response by avoiding the recognition of viral RNA by cell sensors. Here, we studied the responses of NK cells to dendritic cells and macrophages infected with a recombinant Lassa virus in which the exonuclease functions have been abolished and demonstrated that NK cells are strongly activated and presented effective functions. These results show that the strategy developed by Lassa virus to evade innate immunity is also effective on NK cells, explaining the weak NK cell activation observed with the wild-type virus. By providing a better understanding of the interactions between Lassa virus and the host immune system, these results are important for the field of arenavirus biology and may be useful for a vaccine approach against Lassa fever.

111: Aryl hydrocarbon receptor negatively regulates type I interferon production and the development of murine lupus

Background Systemic lupus erythematosus is a highly heterogenous multi-organ autoimmune disease characterized by the production of diverse autoantibodies and broad spectrum of clinical manifestations. Various studies suggest an important role for type I interferon (IFN) in the pathogenesis of lupus. Type I IFN signaling and subsequent feedback induction of type I IFN production, are critically dependent on the STAT1 transcription factor. However, how type I IFN activity is regulated through inhibition of STAT1 function is poorly understood. In our previous study we demonstrated that the aryl hydrocarbon receptor (AHR) inhibits STAT1 activity through TLR4 signaling. In the current study we investigated a role for AHR in type I IFN signaling through TLR7/9 pathways. Methods and results We showed that type I IFN production and signaling both in plasmacytoid dendritic cells (pDCs), and in vivo , is significantly higher in AHR knockout mice compared to wild-type mice, following stimulation with TLR9 ligands. Type I IFN production was suppressed by AHR agonist and in AHR over-expressing cells. We demonstrated that through TLR9 signaling or by IFN-α stimulation in pDCs, expression of AHR is induced, which in-turn forms an inhibitory interaction with STAT1. This interaction attenuates both type I IFN signaling and in-turn, positive-feedback induction of type I IFN. Interestingly, we also found that AHR also forms an inhibitory interaction with IRF7 (a transcription factor which induces type I IFN production). In pristane-induced murine lupus, we found that expression of IFN-stimulated genes, accumulation of Ly6c high IFN producing cells, production of type I IFN-dependent autoantibody and severity of proteinurea, were significantly higher in AHR knockout mice compared to wild-type mice. Conclusion We firstly report that AHR negatively regulates type I IFN production and signaling through an inhibitory interaction with IRF7 and STAT1 respectively and inhibits interferon-dependent disease in murine lupus.

FRI0394 The Proteasome Inhibitor Bortezomib Ameliorates Refractory Systemic Lupus Erythematosus (SLE): A Prospective Multi-Centre Observational Study

ObjectivesThe proteasome inhibitor bortezomib, approved for the therapy of multiple myeloma, depletes plasma cells (PCs) and ameliorates nephritis in mouse models of systemic lupus erythematosus (SLE). Here, we analyzed the...

Aryl hydrocarbon receptor negatively regulates type I interferon production and the development of murine lupus (CCR1P.245)

Abstract Systemic lupus erythematosus is a highly heterogenous multi-organ autoimmune disease characterized by the production of diverse autoantibodies and a broad spectrum of clinical manifestations. The etiology and pathogenesis of lupus remain unclear. Our current understanding highlights an important role for autoantibodies and numerous studies in both animals and humans now suggest an important role for type I interferon (IFN) in the pathogenesis of lupus. Type I IFN signaling and subsequent feedback induction of type I IFN production, are critically dependent on the STAT1 transcription factor. How type I IFN activity is regulated through inhibition of STAT1 function is poorly understood. Here, we show that type I IFN production and signaling both in cultured plasmatoid dendritic cells, and in vivo, is significantly higher in Aryl hydrocarbon receptor (AHR) knockout mice compared to wild-type mice, following stimulation with TLR7/9 agonists. We demonstrate that through TLR7/9 signaling or by IFN-α, expression of AHR is induced, which in-turn forms an inhibitory interaction with STAT1. This interaction attenuates both type I IFN signaling and in-turn, positive-feedback induction of type I IFN. Furthermore, in pristane-induced murine lupus, we found that production of type I IFN and expression of IFN-stimulated genes in AHR knockout mice is higher than in wild-type mice. In conclusion, AHR negatively regulates type I IFN signaling and production and the development of murine lupus.

Equine arteritis virus does not induce interferon production in equine endothelial cells: identification of nonstructural protein 1 as a main interferon antagonist.

The objective of this study was to investigate the effect of equine arteritis virus (EAV) on type I interferon (IFN) production. Equine endothelial cells (EECs) were infected with the virulent Bucyrus strain (VBS) of EAV and expression of IFN-β was measured at mRNA and protein levels by quantitative real-time RT-PCR and IFN bioassay using vesicular stomatitis virus expressing the green fluorescence protein (VSV-GFP), respectively. Quantitative RT-PCR results showed that IFN-β mRNA levels in EECs infected with EAV VBS were not increased compared to those in mock-infected cells. Consistent with quantitative RT-PCR, Sendai virus- (SeV-) induced type I IFN production was inhibited by EAV infection. Using an IFN-β promoter-luciferase reporter assay, we subsequently demonstrated that EAV nsps 1, 2, and 11 had the capability to inhibit type I IFN activation. Of these three nsps, nsp1 exhibited the strongest inhibitory effect. Taken together, these data demonstrate that EAV has the ability to suppress the type I IFN production in EECs and nsp1 may play a critical role to subvert the equine innate immune response.

Type I Interferon and NF-κB Activation Elicited by Herpes Simplex Virus gH/gL via αvβ3 Integrin in Epithelial and Neuronal Cell Lines

αvβ3 integrin represents a novel sensing system which detects herpes simplex virus (HSV) and bacterial constituents. In cooperation with Toll-like receptor 2 (TLR2), it elicits an innate response that leads to activation of type I interferon (IFN), NF-κB, and a specific set of cytokines. We report that this defensive branch is functional in cells which represent experimental models of epithelial, including keratinocytic, and neuronal cells. These are the major targets of HSV in vivo. HSV entered the three cell lines via distinct routes. Hence, the defensive response was independent of the route of virus entry. Soluble gH/gL sufficed to elicit type I IFN and NF-κB activation and represents the viral pathogen-associated molecular pattern (PAMP) of this defense system.

Borna disease virus nucleoprotein inhibits type I interferon induction through the interferon regulatory factor 7 pathway

The expression of type I interferon (IFN) is one of the most potent innate defences against viral infection in higher vertebrates. Borna disease virus (BDV) establishes persistent, noncytolytic infections in animals and in cultured cells. Early studies have shown that the BDV phosphoprotein can inhibit the activation of type I IFN through the TBK1–IRF3 pathway. The function of the BDV nucleoprotein in the inhibition of IFN activity is not yet clear. In this study, we demonstrated IRF7 activation and increased IFN-α/β expression in a BDV-persistently infected human oligodendroglia cell line following RNA interference-mediated BDV nucleoprotein silencing. Furthermore, we showed that BDV nucleoprotein prevented the nuclear localisation of IRF7 and inhibited endogenous IFN induction by poly(I:C), coxsackie virus B3 and IFN-β. Our findings provide evidence for a previously undescribed mechanism by which the BDV nucleoprotein inhibits type I IFN expression by interfering with the IRF7 pathway.

AB0233 Type I interferon and clinical phenotype in idiopathic inflammatory myopathies

BackgroundIdiopathic inflammatory myopathies (IIM) are rare autoimmune diseases characterized by proximal muscle weakness and muscle inflammation. Recent studies suggest a pathogenic role for type I interferon (IFN) in IIM, particularly...

SP0120 Trap deficiency, autoimmunity and other mendelian variants of lupus

Our studies of the Mendelian interferonopathy Aicardi-Goutières syndrome (AGS), and the related disorder familial chilblain lupus, have highlighted the role of cell-intrinsic nucleic acid detection in the causation of autoimmunity,...

THU0026 Genetic Variation Near IRF8 is Associated with Serologic and Cytokine Profiles in Systemic Lupus Erythematosus and Multiple Sclerosis

BackgroundAlleles of IRF8 have been associated with susceptibility to both systemic lupus erythematosus (SLE) and multiple sclerosis (MS). While type I interferon (IFN) is thought to be causal in SLE,...

Increased serum type I interferon activity in early systemic sclerosis patients is associated with antibodies against Sjögren’s syndrome antigens and nuclear ribonucleoprotein antigens

Objective: To study serum type I interferon (IFN) activity in patients with early systemic sclerosis (SSc).Method: Serum type I IFN activity was measured in 33 consecutive patients with SSc and a disease duration of < 2 years and in 13 healthy individuals by calculating a type I IFN score according to the induction of six IFN-α regulated genes in a reporter cell line.Results: Twenty-seven per cent of the SSc patients had an increased type I IFN score compared to none of the healthy individuals (p < 0.05). The clinical SSc phenotype associated with high serum type I IFN activity did not differ from patients with low serum type I IFN activity regarding the presence of skin or lung fibrosis, pulmonary hypertension, or digital complications. Patients with high serum type I IFN activity were younger (p < 0.01) and had a lower frequency of cardiac involvement (p = 0.053), lower leucocyte count (p < 0.001), higher immunoglobulin (Ig)G levels (p < 0.05), and a higher amount of antibodies against extractable nuclear antigens (p < 0.01) than patients with low serum type I IFN activity. The presence of antibodies against topoisomerase I, Sjögren’s syndrome antigen, and nuclear ribonucleoprotein antigens was associated with higher type I IFN activity (p < 0.05 for all comparisons).Conclusions: Our study indicates that increased serum type I IFN activity in early SSc patients is associated with an antibody and laboratory profile that may reflect a subclinical overlap of SSc with other type I IFN-driven connective tissue diseases (CTDs).

Increased Serum Type I Interferon Activity in Organ-Specific Autoimmune Disorders: Clinical, Imaging, and Serological Associations

Background: Activation of the type I interferon (IFN) pathway has been implicated in the pathogenesis of systemic autoimmune disorders but its role in the pathogenesis of organ-specific autoimmunity is limited. We tested the hypothesis that endogenous expression of type I IFN functional activity contributes to the pathogenesis of autoimmune thyroid disease (ATD) and type I diabetes (T1DM).Methods: We studied 39 patients with ATD and 39 age and sex matched controls along with 88 T1DM patients and 46 healthy matched controls respectively. Available clinical and serological parameters were recorded by chart review, and thyroid ultrasound was performed in 17 ATD patients. Type I IFN serum activity was determined in all subjects using a reporter cell assay. The rs1990760 SNP of the interferon-induced helicase 1 gene was genotyped in ATD patients.Results: Serum type I IFN activity was increased in patients with ATD and T1DM compared to controls (p-values: 0.002 and 0.04, respectively). ATD patients with high type I IFN serum activity had increased prevalence of antibodies against thyroglobulin (anti-Tg) and cardiopulmonary manifestations compared to those with low IFN activity. Additionally, the presence of micronodules on thyroid ultrasound was associated with higher type I IFN levels. In patients with T1DM, high IFN levels were associated with increased apolipoprotein-B levels.Conclusion: Serum type I IFN activity is increased in ATD and T1DM and is associated with specific clinical, serological, and imaging features. These findings may implicate type I IFN pathway in the pathogenesis of specific features of organ-specific autoimmunity.

Functional genetic polymorphisms in ILT3 are associated with decreased surface expression on dendritic cells and increased serum cytokines in lupus patients

Objective Hyperactivity of the type I interferon (IFN) pathway is involved in the pathogenesis of systemic lupus erythematosus (SLE). Immunoglobulin like transcript (ILT3) is an immunohibitory transmembrane molecule which is induced by type I IFNs. ILT3 is expressed by plasmacytoid dendritic cells (PDCs), monocytoid dendritic cells (MDCs), and monocytes/macrophages. Given the pathogenic role of IFN in SLE, we hypothesised that the IFN-induced immunosuppressive ILT3 receptor may be dysfunctional in human SLE. Methods 132 European-derived and 79 Hispanic-American SLE patients were genotyped for two coding-change single nucleotide polymorphisms (SNPs) predicted to interfere with protein folding in ILT3 (rs11540761 and rs1048801). 116 control DNA samples and sera from healthy controls were also studied. We detected associations between ILT3 genotype and serum cytokine profiles. ILT3 expression levels on PDCs and MDCs from 18 patients and 10 controls were studied by flow cytometry. Results The rs11540761 SNP in the extracellular region was associated with decreased cell surface expression of ILT3 on circulating MDCs and to a lesser extent PDCs in SLE patients. The cytoplasmically located rs1048801 SNP was not associated with a change in dendritic cells expression of ILT3. Both SNPs were significantly and independently associated with increased levels of serum type I IFN activity in SLE patients. The rs1048801 SNP was also associated with increased serum levels of TNF-α. Conclusions Loss-of-function polymorphisms in ILT3 are associated with increased inflammatory cytokine levels in SLE, supporting a biological role for ILT3 in SLE.