Type I interferon blockade in systemic lupus erythematosus: where do we stand?

Targeting interferons in systemic lupus erythematosus: current and future prospects

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown aetiology that can be debilitating and life threatening. As new insights are gained into the underlying pathology of SLE, there have been an unprecedented number of new agents under development to treat the disease via a diverse range of targets. One such class of emerging agents target interferon (IFN) signalling. In this article, we review the preclinical evidence that the inhibition of the secretion and downstream effectors of both IFN-α and IFN-γ may be effective for the treatment of SLE. The primary agents that are currently in clinical development to treat SLE via the targeting of interferon pathways are monoclonal neutralising antibodies (Mab) that bind to and neutralise IFN-γ (AMG 811), IFN-α (sifalimumab, rontalizumab and AGS-009) or its receptor (anifrolumab), and IFN-α kinoid, which is a drug composed of inactivated IFN-α molecules coupled to the keyhole limpet haemocyanin protein. Phase I and II trials have demonstrated acceptable short-term safety with no increase in severe viral infections or reactivation, favourable pharmacokinetic profiles and an inhibition of IFN-associated gene overexpression; however, the impact of these drugs on disease activity must still be assessed in phase III clinical trials. This review concludes with a summary of the challenges that are inherent to this approach to managing SLE.

Immunoinflammatory diseases of the central nervous system - the tale of two cytokines

Cytokines are potent mediators of cellular communication that have crucial roles in the regulation of innate and adaptive immunoinflammatory responses. Clear evidence has emerged in recent years that the dysregulated production of cytokines may in itself be causative in the pathogenesis of certain immunoinflammatory disorders. Here we review current evidence for the involvement of two different cytokines, IFN-α and IL-6, as principal mediators of specific immunoinflammatory disorders of the CNS. IFN-α belongs to the type I IFN family and is causally linked to the development of inflammatory encephalopathy exemplified by the genetic disorder, Aicardi-Goutières syndrome. IL-6 belongs to the gp130 family of cytokines and is causally linked to a number of immunoinflammatory disorders of the CNS including neuromyelitis optica, idiopathic transverse myelitis and genetically linked autoinflammatory neurological disease. In addition to clinical evidence, experimental studies, particularly in genetically engineered mouse models with astrocyte-targeted, CNS-restricted production of IFN-α or IL-6 replicate many of the cardinal neuropathological features of these human cytokine-linked immunoinflammatory neurological disorders giving crucial evidence for a direct causative role of these cytokines and providing further rationale for the therapeutic targeting of these cytokines in neurological diseases where indicated.

At the Bedside: Neutrophil extracellular traps (NETs) as targets for biomarkers and therapies in autoimmune diseases

Neutrophil extracellular traps are associated with a unique form of cell death distinct from apoptosis or necrosis, whereby invading microbes are trapped and killed. Neutrophil extracellular traps can contribute to autoimmunity by exposing autoantigens, inducing IFN-α production, and activating the complement system. The association of neutrophil extracellular traps with autoimmune diseases, particularly systemic lupus erythematosus, will be reviewed. Increased neutrophil extracellular trap formation is seen in psoriasis, antineutrophil cytoplasmic antibody-associated vasculitis, antiphospholipid antibody syndrome rheumatoid arthritis, and systemic lupus erythematosus. Neutrophil extracellular traps may promote thrombus formation in antineutrophil cytoplasmic antibody-associated vasculitis and antiphospholipid antibody syndrome. In systemic lupus erythematosus, increased neutrophil extracellular trap formation is associated with increased disease activity and renal disease, suggesting that neutrophil extracellular traps could be a disease activity marker. Neutrophil extracellular traps can damage and kill endothelial cells and promote inflammation in atherosclerotic plaques, which may contribute to accelerated atherosclerosis in systemic lupus erythematosus. As neutrophil extracellular traps induce IFN-α production, measuring neutrophil extracellular traps may estimate IFN-α levels and identify which systemic lupus erythematosus patients have elevated levels and may be more likely to respond to emerging anti-IFN-α therapies. In addition to anti-IFN-α therapies, other novel agents, such as N-acetyl-cysteine, DNase I, and peptidylarginine deiminase inhibitor 4, target neutrophil extracellular traps. Neutrophil extracellular traps offer insight into the pathogenesis of autoimmune diseases and provide promise in developing disease markers and novel therapeutic agents in systemic lupus erythematosus. Priority areas for basic research based on clinical research insights will be identified, specifically the potential role of neutrophil extracellular traps as a biomarker and therapeutic target in systemic lupus erythematosus.

Lupus erythematosus revisited

Lupus erythematosus (LE) is a multifactorial autoimmune disease with clinical manifestations of differing severity. The exact pathomechanisms and interactions resulting in the inflammatory and immunological processes of this heterogeneous disease remain elusive. Approaches in the understanding of the pathomechanisms revealed that the clinical expression of LE is predisposed by susceptibility genes and that various environmental factors are responsible for an abnormal immune response. Several studies demonstrated that ultraviolet (UV) light is one of the major factors in the pathogenesis of the disease. Standardized photoprovocation in patients with LE has been shown to be a safe and efficient model for evaluating the underlying pathomechanisms which lead to the production of autoantibodies and immune complexes. In particular, interferons were defined as important players in the early activation of the immune system and were observed to play a specific role in the immunological interface between the innate and the adaptive immune system. Abnormalities or disturbances in the different processes of cell death, such as apoptosis or necrosis, have also been recognized as crucial in the pathogenesis of LE. Although each process is different and characterized by unique features, the processes are interrelated and result in a complex disease.

Interferon-β promotes macrophage foam cell formation by altering both cholesterol influx and efflux mechanisms

Foam cell formation is a crucial event in atherogenesis. While interferon-β (IFNβ) is known to promote atherosclerosis in mice, studies on the role of IFNβ on foam cell formation are minimal and conflicting. We therefore extended these studies using both in vitro and in vivo approaches and examined IFNβ's function in macrophage foam cell formation. To do so, murine bone marrow-derived macrophages (BMDMs) and human monocyte-derived macrophages were loaded with acLDL overnight, followed by 6h IFNβ co-treatment. This increased lipid content as measured by Oil red O staining. We next analyzed the lipid uptake pathways of IFNβ-stimulated BMDMs and observed increased endocytosis of DiI-acLDL as compared to controls. These effects were mediated via SR-A, as its gene expression was increased and inhibition of SR-A with Poly(I) blocked the IFNβ-induced increase in Oil red O staining and DiI-acLDL endocytosis. The IFNβ-induced increase in lipid content was also associated with decreased ApoA1-mediated cholesterol efflux, in response to decreased ABCA1 protein and gene expression. To validate our findings in vivo, LDLR(-/-) mice were put on chow or a high cholesterol diet for 10weeks. 24 and 8h before sacrifice mice were injected with IFNβ or PBS, after which thioglycollate-elicited peritoneal macrophages were collected and analyzed. In accordance with the in vitro data, IFNβ increased lipid accumulation. In conclusion, our experimental data support the pro-atherogenic role of IFNβ, as we show that IFNβ promotes macrophage foam cell formation by increasing SR-A-mediated cholesterol influx and decreasing ABCA1-mediated efflux mechanisms.

Structural basis of the broadly neutralizing anti-interferon-α antibody rontalizumab

Interferons-alpha (IFN-α) are the expressed gene products comprising thirteen type I interferons with protein pairwise sequence similarities in the 77-96% range. Three other widely expressed human type I interferons, IFN-β, IFN-κ and IFN-ω have sequences 29-33%, 29-32% and 56-60% similar to the IFN-αs, respectively. Type I interferons act on immune cells by producing subtly different immune-modulatory effects upon binding to the extracellular domains of a heterodimeric cell-surface receptor composed of IFNAR1 and IFNAR2, most notably anti-viral effects. IFN-α has been used to treat infection by hepatitis-virus type C (HCV) and a correlation between hyperactivity of IFN-α-induced signaling and systemic lupus erythematosis (SLE), or lupus, has been noted. Anti-IFN-α antibodies including rontalizumab have been under clinical study for the treatment of lupus. To better understand the rontalizumab mechanism of action and specificity, we determined the X-ray crystal structure of the Fab fragment of rontalizumab bound to human IFN-α2 at 3Å resolution and find substantial overlap of the antibody and IFNA2 epitopes on IFN-α2.

Animal Models of Interferon Signature Positive Lupus

Human lupus is strongly associated with a gene expression signature characterized by over-expression of Type I interferon-regulated genes. A strong interferon signature generally is not seen in the standard mouse models of lupus, despite considerable evidence for the involvement of toll-like receptor-driven interferon production. In contrast, pristane-induced lupus exhibits a prominent TLR7-dependent interferon signature. Importantly, genetic disorders with dysregulated interferon production in both human beings and mice cause severe autoinflammatory diseases but not the typical manifestations of lupus, suggesting that interferon over-production is insufficient to cause systemic lupus erythematosus itself. Single-gene models in mice suggest that lupus-like disease may result from abnormalities in B-cell activation and the clearance of dead cells. Pristane may mimic human systemic lupus erythematosus by causing synergistic abnormalities in interferon production along with defective clearance of apoptotic cells and over-active B-cell signaling.

Inflammasomes and human autoimmunity: A comprehensive review

Inflammasomes are multi-protein complexes composed of a NOD-like receptor (NLR)/an AIM-like receptor (ALR), the adapter molecule apoptosis-associated speck-like protein that contains a CARD (ASC), and caspase-1. Active caspase-1 cleaves pro-IL-1β and pro-IL-18 to IL-1β and IL-18, resulting in inflammation. Genetic mutations in inflammasomes were first recognized to result in autoinflammatory diseases, which are characterized by the absence of both autoantibodies and autoreactive-T/B cells. However, there is increasing attention being placed on genetic polymorphisms that are involved in the components of inflammasomes, and these have implications for innate immunity and the natural history of autoimmune diseases. For example, while the NOD-like receptor family, pyrin domain containing 1 (NLRP1) haplotypes contributes to susceptibility to developing vitiligo; there are other single nucleotide polymorphisms (SNPs) that alters the susceptibility and severity of rheumatoid arthritis (RA) and juvenile idiopathic arthritis. Indeed, there are multiple factors that contribute to lowering the threshold of immunity and inflammasomes play a key role in this threshold. For example, IL-1β and IL-18 further perpetuate Th17 responses and endothelial cell damage, which potentiate a number of autoimmune diseases, including synovitis in RA, cardiovascular disease, and systemic lupus erythematosus (SLE). There is also increasing data on the role of innate immunity in experimental autoimmune encephalomyelitis (EAE), in lupus nephritis, and in a variety of autoimmune pathologies in which activation of the innate immune system is the driver for the adaptive system. Indeed, it is likely that the chronic pathology of autoimmunity is mediated in part by otherwise innocent bystander cells, augmented by inflammasomes.

Modulation of autoimmunity and atherosclerosis - common targets and promising translational approaches against disease

Atherosclerosis is a chronic inflammatory disease of the arterial wall that is influenced by several risk factors, including hyperlipidemia and hypertension. Autoimmune diseases substantially increase the risk for cardiovascular disease (CVD). Although atherosclerotic CVD, such as myocardial and stroke, is much more prevalent than classical autoimmune conditions such as rheumatoid arthritis, psoriasis, and systemic lupus erythematosus, these types of pathology have many similarities, raising the possibility that therapies against autoimmune disease can have beneficial effects on CVD. Substantial clinical and experimental data support the potential for immunomodulatory approaches to combating both autoimmune and cardiovascular diseases, including classical immunosuppressants, anticytokine therapy, the targeting of T and B cells and their responses, and vaccination. In this review, we discuss experimental and clinical studies that have used immunomodulatory approaches to mitigate autoimmune reactions and examine their potential to prevent and treat atherosclerotic CVD.

AGS, SLE, and RNASEH2 mutations: translating insights into therapeutic advances

Systemic lupus erythematosus (SLE) is a severe autoimmune disease characterized by the presence of nucleic acid- and protein-targeting autoantibodies and an aberrant type I IFN expression signature. Aicardi-Goutières syndrome (AGS) is an autosomal-recessive encephalopathy in children that is characterized by mutations in numerous nucleic acid repair enzymes and elevated IFN levels. Phenotypically, patients with AGS and SLE share many similarities. Ribonuclease H2 (RNase H2) is a nucleic acid repair enzyme that removes unwanted ribonucleotides from DNA. In this issue of the JCI, Günther and colleagues provide an in-depth investigation of the mechanisms underlying the link between defective removal of ribonucleotides in AGS and SLE, and these findings will likely serve as a strong springboard to provide novel therapeutic inroads.

Pathogenesis and potential therapeutic targets in systemic lupus erythematosus: from bench to bedside

Systemic lupus erythematosus (SLE) is considered an autoimmune disease with multiorgan involvement. Many advances have been made during the last decade regarding inflammatory pathways, genetic and epigenetic alterations, adaptive and innate immune system mechanisms specifically involved in SLE pathogenesis. Apoptosis has been proposed as an important player in SLE pathogenesis more than a decade ago. However, only recently new key apoptotic pathways have been investigated and the link between apoptotic debris containing autoantigens, innate immunity and ongoing inflammation has been further elucidated. Better understanding of cellular mechanisms and involved cytokines contributed to the development of new biological drugs specifically addressed for SLE therapy.

Interferon alpha on NZM2328.Lc1R27: enhancing autoimmunity and immune complex-mediated glomerulonephritis without end stage renal failure

Interferon alpha (IFNα) may play a significant role in systemic lupus erythematosus (SLE) pathogenesis. Recent literature suggests that IFNα does not correlate with disease activities and blockade of IFNα is not effective in treating SLE. This study aims to delineate further the role of IFNα in SLE. 12-week old NZM2328 and its congenic NZM2328.Lc1R27 (R27) female mice were challenged with adenovirus-IFNα (adeno-IFNα) or adenovirus-LacZ (adeno-LacZ). Only adeno-IFNα treated NZM2328 developed severe proteinuria and died of chronic glomerulonephritis (GN) and end stage renal disease. Adeno-IFNα treated R27 did develop immune complex-mediated GN but had normal renal function. Adeno-LacZ treated NZM2328 showed enlarged glomeruli and increased cellularity without immune complex deposition. Adeno-LacZ treated R27 did not show serological and histological abnormalities. Adeno-IFNα induced anti-dsDNA and anti-kidney autoantibodies in NZM2328 and R27. These results suggest that end organ damage is host-dependent and less related to autoimmunity and may have significant implications in SLE pathogenesis.

When biologics should be used in systemic lupus erythematosus?

Recently, the use and evaluation of biologics increased in systemic lupus erythematosus (SLE). However, no international recommendation is available concerning the use of biologics with regards to the subset of patients who should be treated, the optimal time to treat, the objective of treatment and the manner to discontinue it. To address these complex questions, we focused on biologics already evaluated in at least two published randomized controlled trials. We summarized the results of these trials and available observational data in registries. Taking into account the clinical evidence, we proposed some guidance on the way biologics could be used in SLE. Many areas of uncertainty persist and require intensifying efforts from the academic world to set up new trials, and develop international recommendations.

Blood gene expression profiling in pediatric systemic lupus erythematosus and systemic juvenile idiopathic arthritis: from bench to bedside

Blood gene expression profiling has led to major advances in the field of rheumatology over the last few decades. Specifically, DNA microarray technology has been integral in increasing our knowledge of key players in the pathogenesis of some rare pediatric rheumatic diseases. Our group, using microarray analysis, identified the interferon (IFN) gene signature in pediatric systemic lupus erythematosus (SLE) and has published data that suggest high doses of intravenous corticosteroid treatment may have benefit over strictly oral regimens. Additionally, DNA microarray technology led to our discovery that the interleukin (IL)-1 gene signature is associated with systemic juvenile idiopathic arthritis (sJIA) and to the use of IL-1 blockade with anakinra in this disease. We also reported the biologic rationale for use of anakinra early in the disease course. Anakinra is now being used as first-line treatment in sJIA in multiple centers. Herein, we review how information obtained from blood gene expression profiling has changed our clinical practice.