Type I Interferon Predicts an Alternate Immune System Phenotype in Systemic Lupus Erythematosus

Potential role of EBV and Toll-like receptor 9 ligand in patients with systemic lupus erythematosus

SLE is a multisystem autoimmune disease characterized by multiple immunological abnormalities including production of autoantibodies. While the etiology of SLE is largely unknown, it is generally accepted that both genetic and environmental factors contribute to disease risk and immune dysregulation. Production of IFN-α is important for protecting the host against infections; however, over stimulation of innate immune pathways can induce autoimmune disease. Environmental factors, particularly Epstein-Barr virus (EBV), have been proposed to play an important role in SLE disease. Improper engagement of Toll-like receptor (TLR) pathways by endogenous or exogenous ligands may lead to the initiation of autoimmune responses and tissue injury. EBV is shown to be a potent stimulant of IFN-α by TLR signaling cascades. Given the highlighted role of IFN-α in SLE pathogenesis and potential role of EBV infection in this disease, the present study is aimed at exploring the in vitro effects of EBV infection and CPG (either alone or in combination) on IFN-α. We also examined the expression level of CD20 and BDCA-4 and CD123 in PBMCs in 32 SLE patients and 32 healthy controls. Our results showed PBMCs treated with CPG-induced higher levels of IFN-α and TLR-9 gene expression fold change compared to cells treated with either EBV or EBV-CPG. Moreover, PBMCs treated with CPG produced significantly higher IFN-α concentration in supernatant compared to cells treated with EBV but not EBV-CPG. Our results further highlight the potential role of EBV infection and TLRs in SLE patients although more studies are warranted to ascertain the global imprint that EBV infection can have on immune signature in patients with SLE.

Type I Interferons in Autoimmunity: Implications in Clinical Phenotypes and Treatment Response

Type I interferon (IFN-I) is thought to play a role in many systemic autoimmune diseases. IFN-I pathway activation is associated with pathogenic features, including the presence of autoantibodies and clinical phenotypes such as more severe disease with increased disease activity and damage. We will review the role and potential drivers of IFN-I dysregulation in 5 prototypic autoimmune diseases: systemic lupus erythematosus, dermatomyositis, rheumatoid arthritis, primary Sjögren syndrome, and systemic sclerosis. We will also discuss current therapeutic strategies that directly or indirectly target the IFN-I system.

Type I interferon pathway assays in studies of rheumatic and musculoskeletal diseases: a systematic literature review informing EULAR points to consider

OBJECTIVES

To systematically review the literature for assay methods that aim to evaluate type I interferon (IFN-I) pathway activation and to harmonise-related terminology.

METHODS

Three databases were searched for reports of IFN-I and rheumatic musculoskeletal diseases. Information about the performance metrics of assays measuring IFN-I and measures of truth were extracted and summarised. A EULAR task force panel assessed feasibility and developed consensus terminology.

RESULTS

Of 10 037 abstracts, 276 fulfilled eligibility criteria for data extraction. Some reported more than one technique to measure IFN-I pathway activation. Hence, 276 papers generated data on 412 methods. IFN-I pathway activation was measured using: qPCR (n=121), immunoassays (n=101), microarray (n=69), reporter cell assay (n=38), DNA methylation (n=14), flow cytometry (n=14), cytopathic effect assay (n=11), RNA sequencing (n=9), plaque reduction assay (n=8), Nanostring (n=5), bisulphite sequencing (n=3). Principles of each assay are summarised for content validity. Concurrent validity (correlation with other IFN assays) was presented for n=150/412 assays. Reliability data were variable and provided for 13 assays. Gene expression and immunoassays were considered most feasible. Consensus terminology to define different aspects of IFN-I research and practice was produced.

CONCLUSIONS

Diverse methods have been reported as IFN-I assays and these differ in what elements or aspects of IFN-I pathway activation they measure and how. No 'gold standard' represents the entirety of the IFN pathway, some may not be specific for IFN-I. Data on reliability or comparing assays were limited, and feasibility is a challenge for many assays. Consensus terminology should improve consistency of reporting.

Type I Interferons in Autoimmunity

Dysregulated IFN-1 responses play crucial roles in the development of multiple forms of autoimmunity. Many patients with lupus, systemic sclerosis, Sjogren's syndrome, and dermatomyositis demonstrate enhanced IFN-1 signaling. IFN-1 excess is associated with disease severity and autoantibodies and could potentially predict response to newer therapies targeting IFN-1 pathways. In this review, we provide an overview of the signaling pathway and immune functions of IFN-1s in health and disease. We also review the systemic autoimmune diseases classically associated with IFN-1 upregulation and current therapeutic strategies targeting the IFN-1 system.

The role of cyclic GMP-AMP synthase and Interferon-I-inducible protein 16 as candidatebiomarkers of systemic lupus erythematosus

BACKGROUND

Diverse clinical and serological manifestations of systemic lupus erythematosus (SLE) compromise its diagnosis and treatment. A more reliable biomarker for SLE, which can play a critical role in either diagnosis, monitoring the disease progress or evaluating the response to treatment for individualized therapeutic, is necessary. DNA sensor is an important mediator of inflammation in systemic autoimmune diseases. However, the potential role for DNA sensor as disease activity biomarkers for SLE remained obscure. We detected the aberrant activation of DNA sensors and the corresponding IFN-β response in SLE patients, and to evaluate their potential role as disease biomarkers for SLE.

METHODS

We quantified the expressions of IFN-I and DNA sensor, such as cGAS, IFI16, DDX41, DAI and their down-stream adaptor STING in PBMC derived from patients with SLE (n = 100), healthy controls (HCs) (n = 62) by real-time PCR. The relationships between the expression of cGAS or IFI16 and clinical features in SLE patients were investigated. ROC curve analysis was performed to examine the predictive value of cGAS and IFI16 in SLE diagnosis, disease activity monitoring, specific organ manifestation and therapeutic response. RNA interference-mediated depletion of IFI16 or cGAS was conducted to evaluate their impact on IFN-I response.

RESULTS

The expressions of cGAS and IFI16 were significantly higher in PBMC from SLE patients, closely correlated with the SLEDAI scores and high anti-dsDNA antibody titers. While the AUC for cGAS (0.767) was less than that of IFI16 and IFN-β, the AUC for IFI16 (0.856) and IFN-β (0.856) were similar. Expression of cGAS and IFI16 combine with IFN-β in PBMC showed high sensitivity (89.2%) and specificity (89.1%) for discrimination between mild and moderate/severe disease activity in SLE. Higher expression of IFI16 was association with ocular disorder in SLE patients. Neither IFI16 nor cGAS was a reliable indicator of therapeutic response. RNA interference-mediated depletion of IFI16 or cGAS prevented active SLE serum-induced upregulating in both IFN-α and IFN-β.

CONCLUSIONS

High expression levels of cGAS and IFI16 in PBMC from SLE patients correlated strongly with disease activity. Both cGAS and IFI16 mediated signaling pathway were account for the robust production of IFN-β. Expression of cGAS and IFI16 combined with IFN-β in PBMC might serve as potential biomarkers for early diagnosis and monitoring disease activity in SLE.

Abnormalities of the type I interferon signaling pathway in lupus autoimmunity

Type I interferons (IFNs), mostly IFNα and IFNβ, and the type I IFN Signature are important in the pathogenesis of Systemic Lupus Erythematosus (SLE), an autoimmune chronic condition linked to inflammation. Both IFNα and IFNβ trigger a signaling cascade that, through the activation of JAK1, TYK2, STAT1 and STAT2, initiates gene transcription of IFN stimulated genes (ISGs). Noteworthy, other STAT family members and IFN Responsive Factors (IRFs) can also contribute to the activation of the IFN response. Aberrant type I IFN signaling, therefore, can exacerbate SLE by deregulated homeostasis leading to unnecessary persistence of the biological effects of type I IFNs. The etiopathogenesis of SLE is partially known and considered multifactorial. Family-based and genome wide association studies (GWAS) have identified genetic and transcriptional abnormalities in key molecules directly involved in the type I IFN signaling pathway, namely TYK2, STAT1 and STAT4, and IRF5. Gain-of-function mutations that heighten IFNα/β production, which in turn maintains type I IFN signaling, are found in other pathologies like the interferonopathies. However, the distinctive characteristics have yet to be determined. Signaling molecules activated in response to type I IFNs are upregulated in immune cell subsets and affected tissues of SLE patients. Moreover, Type I IFNs induce chromatin remodeling leading to a state permissive to transcription, and SLE patients have increased global and gene-specific epigenetic modifications, such as hypomethylation of DNA and histone acetylation. Epigenome wide association studies (EWAS) highlight important differences between SLE patients and healthy controls in Interferon Stimulated Genes (ISGs). The combination of environmental and genetic factors may stimulate type I IFN signaling transiently and produce long-lasting detrimental effects through epigenetic alterations. Substantial evidence for the pathogenic role of type I IFNs in SLE advocates the clinical use of neutralizing anti-type I IFN receptor antibodies as a therapeutic strategy, with clinical studies already showing promising results. Current and future clinical trials will determine whether drugs targeting molecules of the type I IFN signaling pathway, like non-selective JAK inhibitors or specific TYK2 inhibitors, may benefit people living with lupus.

Down-regulation of LncRNA 2900052N01Rik inhibits LPS-induced B cell function in vitro

B cells play a crucial role in immune responses. The main functions include B cell protective antibody production, inflammation reduction, activation and proliferation. Long non-coding RNAs (lncRNAs) have been reported to act as important regulators of many pathological processes. However, few lncRNAs have been reported to affect B cell function. In this study, we explored the expression and role of lncRNA 2900052N01Rik (lnc-290) in lipopolysaccharide (LPS)-induced B cells purified from mouse spleens in vitro. Here, we confirmed that lnc-290 was highly expressed in B cells stimulated by LPS. Knockdown of lnc-290 inhibited the expression of CD69/CD86 and the growth of B cells. Moreover, down-regulated lnc-290 reduced B cell differentiation and immunoglobulin production in vitro. In addition, we found that lnc-290 regulated LPS-induced B cell activation via the NF-κB/ERK pathways. Interestingly, abnormal lnc-290 expression did not alter the B cell activation or proliferation induced by IL-4 or CD40/CD40L. Accordingly, these results indicated, for the first time, that lnc-290 down-regulation inhibits LPS-induced B cell proliferation, activation and differentiation by blocking the LPS/TLR4 signaling pathway. Together, the in vitro data demonstrate that lnc-290 participated in the inflammation and tissue damage mediated by LPS-activated B cells.

Type I interferon in the pathogenesis of systemic lupus erythematosus

Type I interferon (IFN) is a primary pathogenic factor in systemic lupus erythematosus (SLE). Gain-of-function genetic variants in the type I IFN pathway have been associated with risk of disease. Common polygenic as well as rare monogenic influences on type I IFN have been demonstrated, supporting a complex genetic basis for high IFN in many SLE patients. Both SLE-associated autoantibodies and high type I IFN can be observed in the pre-disease state. Patients with SLE and evidence of high type I IFN have more active disease and a greater propensity to nephritis and other severe manifestations. Despite the well-established association between type I IFN and SLE, the specific triggers of type I IFN production, the mechanisms by which IFNs help perpetuate the cycle of autoreactive cells and autoantibody production are not completely clear. This review provides an updated overview of type I IFN in SLE pathogenesis, clinical manifestations, and current therapeutic strategies targeting this pathway.

Type I interferon antagonists in clinical development for lupus

INTRODUCTION

Systemic lupus erythematosus (SLE) is a severe chronic and incurable autoimmune disease. Treatment includes glucocorticoids and immunosuppressants which typically result in partial responses, and hence there is a great need for new therapies. The type I interferon (IFN) pathway is activated in more than 50% of SLE patients, and it is strongly implicated as a pathogenic factor in SLE.

AREAS COVERED

We searched the literature using 'SLE and interferon antagonists' as search terms. This identified a number of therapeutics that have entered clinical development targeting type I IFN in SLE. These include monoclonal antibodies against type I IFN cytokines and a kinoid vaccination strategy to induce anti-IFN antibodies.

EXPERT OPINION

Type I IFN antagonists have had some success, but many molecules have not progressed to phase III. These varied results are likely attributed to the multiple concurrent cytokine abnormalities present in SLE, the imprecise nature of the IFN signature as a readout for type I IFN and difficulties with clinical trials such as background medication use and diffuse composite disease activity measures. Despite these challenges, it seems likely that a type I IFN antagonist will come to clinical utility for SLE given the large unmet need and the recent phase III success with anifrolumab.