Connective tissue diseases: Targeting type I interferon in systemic lupus erythematosus

Novel JAK inhibitors under investigation for systemic lupus erythematosus: - where are we now?

INTRODUCTION

Glucocorticoids and immunosuppressants are used to treat systemic lupus erythematosus (SLE). However, patients with SLE have poor long-term prognoses. This can be attributed to organ damage caused by flare-ups and drug toxicity due to the administration of nonspecific treatment. Therefore, SLE should be treated using therapeutic agents specific to its pathology. Janus kinase (JAK) inhibitors exert multitargeted effects by blocking the signaling of multiple cytokines. The use of JAK inhibitors has been approved to treat several inflammatory autoimmune diseases. Several clinical trials of JAK inhibitors for SLE treatment are ongoing.

AREA COVERED

This review summarizes the basic and clinical significance of JAK inhibitors for treating SLE and the current status of the development of JAK inhibitors based on recent reports.

EXPERT OPINION

SLE is a clinically and immunologically heterogeneous disease. Therefore, drugs targeting a single molecule require precision medicine to exert maximal therapeutic efficacy. JAK inhibitors can probably fine-tune the immune network via various mechanisms and broadly regulate complex immune-mediated pathologies in SLE. However, evidence is required to address some safety concerns associated with the use of JAK inhibitors in patients with SLE, including infections (particularly herpes zoster) and thromboembolism (particularly in the presence of concomitant antiphospholipid syndrome).

Evaluation of anifrolumab safety in systemic lupus erythematosus: A meta-analysis and systematic review

Objectives

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease, and type I interferon plays an important role in its pathogenesis. Anifrolumab is a new strategy for the treatment of systemic lupus erythematosus. It could antagonize the activity of all type 1 interferons by binding with type I interferon receptor subunit 1. The aim of our study was to evaluate the safety of anifrolumab in patients with moderate to severe SLE (excluding patients with active severe lupus nephritis or central nervous system lupus).

Methods

Four databases (Embase, Cochrane, PubMed, Web of Science) were systematically searched from inception until December 2021 for randomized controlled trials (RCTs) evaluating the safety of anifrolumab versus placebo in SLE patients. Then, the incidence of adverse events in each study was aggregated using meta-analysis.

Results

A total of 1160 SLE patients from four RCTs were included in the analysis. Serious adverse events were less common in the anifrolumab group than in the placebo group (RR: 0.76, 95% CI: 0.59-0.98, p<0.03). The most common adverse events included upper respiratory tract infection (RR: 1.48, 95% CI: 1.13-1.94, P=0.004), nasopharyngitis (RR: 1.66, 95% CI: 1.25-2.20, P=0.0004), bronchitis (RR: 1.96, 95% CI: 1.32-2.92, P=0.0009), and herpes zoster (RR: 3.40, 95% CI: 1.90-6.07, P<0.0001).

Conclusion

Anifrolumab is considered a well-tolerated option for the treatment of SLE patients with good safety.

Systematic Review Registration

https://inplasy.com, identifier 202230054.

What can we learn from DNA methylation studies in lupus?

During the past twenty years, a wide range of studies have established the existence of epigenetic alterations, particularly DNA methylation changes, in lupus. Epigenetic changes might have different contributions in children-onset versus adult-onset lupus. DNA methylation alterations have been identified and characterized in relation to disease activity and damage, different lupus subtypes and responses to drugs. However, to date there has been no practical application of these findings in the clinical milieu. In this article, we provide a review of key studies showing the relationship between DNA methylation and the many clinical aspects related to lupus. We also propose several options, in relation to the range of methodological developments and experimental design, that could optimize these findings and make them amenable for use in clinical practice.

Circulating mitochondrial DNA copy numbers represent a sensitive marker for diagnosis and monitoring of disease activity in systemic lupus erythematosus

OBJECTIVES

Cell-free DNA is involved in the pathogenesis of systemic lupus erythematosus (SLE) but the clinical value of cell-free DNA measurements in SLE is unknown. Our aim was therefore to examine the utility of mitochondrial (mt) DNA and nuclear (n) DNA quantification in SLE.

METHODS

EDTA plasma was drawn from 103 consecutive patients with SLE and from 56 healthy blood donors. mtDNA and nDNA copy numbers were quantified by PCR from cell-free plasma. Clinical parameters were recorded prospectively.

RESULTS

Circulating mtDNA copy numbers were increased 8.8-fold in the plasma of patients with SLE (median 6.6×10⁷ /mL) compared with controls (median 7.6×10⁶ /mL, p<0.0001). Among all 159 individuals, a cut-off set at 1.8×10⁷ mtDNA copies in a receiver operated curve identified patients with SLE with 87.4% sensitivity and 94.6% specificity; the area under the curve was 0.95 (p<0.0001). mtDNA levels were independent of age or gender, but correlated with Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) on multivariable analysis (p=0.004). Conversely, SLEDAI was associated with prednisone dose (p<0.001), anti-double stranded DNA-titres (p=0.003) and mtDNA levels (p=0.005), but not nDNA copy numbers. In 33 patients with SLE with available follow-up, the changes of mtDNA, but not those of nDNA concentrations, robustly correlated with the evolution of the SLEDAI (r=0.55, p=0.001).

CONCLUSIONS

Circulating mtDNA unlike nDNA molecules are markedly increased in SLE plasma. Regardless of disease activity, circulating mtDNA levels distinguish patients with SLE from healthy controls with high sensitivity and represent an independent marker of SLE activity.

Protein and DNA methylation-based scores as surrogate markers for interferon system activation in patients with primary Sjögren's syndrome

OBJECTIVE

Standard assessment of interferon (IFN) system activity in systemic rheumatic diseases depends on the availability of RNA samples. In this study, we describe and evaluate alternative methods using plasma, serum and DNA samples, exemplified in the IFN-driven disease primary Sjögren's syndrome (pSS).

METHODS

Patients with pSS seropositive or negative for anti-SSA/SSB and controls were included. Protein-based IFN (pIFN) scores were calculated from levels of PD-1, CXCL9 and CXCL10. DNA methylation-based (DNAm) IFN scores were calculated from DNAm levels at RSAD2, IFIT1 and IFI44L . Scores were compared with mRNA-based IFN scores measured by quantitative PCR (qPCR), Nanostring or RNA sequencing (RNAseq).

RESULTS

mRNA-based IFN scores displayed strong correlations between B cells and monocytes (r=0.93 and 0.95, p<0.0001) and between qPCR and Nanostring measurements (r=0.92 and 0.92, p<0.0001). The pIFN score in plasma and serum was higher in patients compared with controls (p<0.0001) and correlated well with mRNA-based IFN scores (r=0.62-0.79, p<0.0001), as well as with each other (r=0.94, p<0.0001). Concordance of classification as 'high' or 'low' IFN signature between the pIFN score and mRNA-based IFN scores ranged from 79.5% to 88.6%, and the pIFN score was effective at classifying patients and controls (area under the curve, AUC=0.89-0.93, p<0.0001). The DNAm IFN score showed strong correlation to the RNAseq IFN score (r=0.84, p<0.0001) and performed well in classifying patients and controls (AUC=0.96, p<0.0001).

CONCLUSIONS

We describe novel methods of assessing IFN system activity in plasma, serum or DNA samples, which may prove particularly valuable in studies where RNA samples are not available.

FcγRIIA expression accelerates nephritis and increases platelet activation in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease characterized by deposits of immune complexes (ICs) in organs and tissues. The expression of FcγRIIA by human platelets, which is their unique receptor for immunoglobulin G antibodies, positions them to ideally respond to circulating ICs. Whereas chronic platelet activation and thrombosis are well-recognized features of human SLE, the exact mechanisms underlying platelet activation in SLE remain unknown. Here, we evaluated the involvement of FcγRIIA in the course of SLE and platelet activation. In patients with SLE, levels of ICs are associated with platelet activation. Because FcγRIIA is absent in mice, and murine platelets do not respond to ICs in any existing mouse model of SLE, we introduced the FcγRIIA (FCGR2A) transgene into the NZB/NZWF1 mouse model of SLE. In mice, FcγRIIA expression by bone marrow cells severely aggravated lupus nephritis and accelerated death. Lupus onset initiated major changes to the platelet transcriptome, both in FcγRIIA-expressing and nonexpressing mice, but enrichment for type I interferon response gene changes was specifically observed in the FcγRIIA mice. Moreover, circulating platelets were degranulated and were found to interact with neutrophils in FcγRIIA-expressing lupus mice. FcγRIIA expression in lupus mice also led to thrombosis in lungs and kidneys. The model recapitulates hallmarks of human SLE and can be used to identify contributions of different cellular lineages in the manifestations of SLE. The study further reveals a role for FcγRIIA in nephritis and in platelet activation in SLE.

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.

Lessons from precision medicine in rheumatology

Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are two common autoimmune rheumatic diseases that vary in severity, clinical presentation, and disease course between individuals. Molecular and genetic studies of both diseases have identified candidate genes and molecular pathways that are linked to various disease outcomes and treatment responses. Currently, patients can be grouped into molecular subsets in each disease, and these molecular categories should enable precision medicine approaches to be applied in rheumatic diseases. In this article, we will review key lessons learned about disease heterogeneity and molecular characterization in rheumatology, which we hope will lead to personalized therapeutic strategies.

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

Objective

Type I interferon (IFN) is important to systemic lupus erythematosus (SLE) pathogenesis, but it is not clear how chronic elevations in IFN alter immune function. We compared cytokine responses after whole blood stimulation with Toll‐like receptor (TLR) agonists in high‐ and low‐IFN SLE patient subgroups.

Methods

SLE patients and nonautoimmune controls were recruited, and SLE patients were categorized as either high or low IFN. Whole blood was dispensed into tubes coated with lipopolysaccharide (LPS), oligonucleotides with cytosine‐guanine repeats, Resiquimod, IFN‐α, and IFN‐α + LPS. Cytokine production in patient sera and after whole blood TLR stimulation was measured by multiplex assay, and type I IFN was assessed using a functional assay.

Results

Circulating plasmacytoid dendritic cell numbers were specifically reduced in high‐IFN SLE patients and not in low‐IFN SLE patients. In serum, we observed that the correlations between cytokines in serum differed to a much greater degree between the high‐ and low‐IFN groups (P < 0.0001) than the absolute cytokine levels differed between these same groups. In stimulated conditions, the high‐IFN patients had less cytokine production in response to TLR ligation than the low‐IFN SLE patients. LPS produced the most diverse response, and a number of interactions between type I IFN and LPS were observed.

Conclusion

We find striking differences in resting and stimulated cytokine patterns in high‐ vs. low‐IFN SLE patients, which supports the biological importance of these patient subsets. These data could inform personalized treatment approaches and the pathogenesis of SLE flare following infection.

Insights from deconvolution of cell subtype proportions enhance the interpretation of functional genomic data

Cell subtype proportion variability between samples contributes significantly to the variation of functional genomic properties such as gene expression or DNA methylation. Although the impact of the variation of cell subtype composition on measured genomic quantities is recognized, and some innovative tools have been developed for the analysis of heterogeneous samples, most functional genomics studies using samples with mixed cell types still ignore the influence of cell subtype proportion variation, or just deal with it as a nuisance variable to be eliminated. Here we demonstrate how harvesting information about cell subtype proportions from functional genomics data can provide insights into cellular changes associated with phenotypes. We focused on two types of mixed cell populations, human blood and mouse kidney. Cell type prediction is well developed in the former, but not currently in the latter. Estimating the cellular repertoire is easier when a reference dataset from purified samples of all cell types in the tissue is available, as is the case for blood. However, reference datasets are not available for most other tissues, such as the kidney. In this study, we showed that the proportion of alterations attributable to changes in the cellular composition varies strikingly in the two disorders (asthma and systemic lupus erythematosus), suggesting that the contribution of cell subtype proportion changes to functional genomic properties can be disease-specific. We also showed that a reference dataset from a single-cell RNA-seq study successfully estimated the cell subtype proportions in mouse kidney and allowed us to distinguish altered cell subtype differences between two different knock-out mouse models, both of which had reported a reduced number of glomeruli compared to their wild-type counterparts. These findings demonstrate that testing for changes in cell subtype proportions between conditions can yield important insights in functional genomics studies.

Type I interferon in rheumatic diseases

The type I interferon pathway has been implicated in the pathogenesis of a number of rheumatic diseases, including systemic lupus erythematosus, Sjögren syndrome, myositis, systemic sclerosis, and rheumatoid arthritis. In normal immune responses, type I interferons have a critical role in the defence against viruses, yet in many rheumatic diseases, large subgroups of patients demonstrate persistent activation of the type I interferon pathway. Genetic variations in type I interferon-related genes are risk factors for some rheumatic diseases, and can explain some of the heterogeneity in type I interferon responses seen between patients within a given disease. Inappropriate activation of the immune response via Toll-like receptors and other nucleic acid sensors also contributes to the dysregulation of the type I interferon pathway in a number of rheumatic diseases. Theoretically, differences in type I interferon activity between patients might predict response to immune-based therapies, as has been demonstrated for rheumatoid arthritis. A number of type I interferon and type I interferon pathway blocking therapies are currently in clinical trials, the results of which are promising thus far. This Review provides an overview of the many ways in which the type I interferon system affects rheumatic diseases.

Elevated serum levels of IL-6 and CXCL9 in autoimmune retinopathy (AIR) patients

Autoimmune retinopathy (AIR) is a rare immune-mediated retinopathy associated with circulating antiretinal antibodies (ARAs). Other prominent features of AIR include visual field deficits and photoreceptor dysfunction in the setting of progressive unexplained vision loss. The role of inflammation is poorly understood in AIR. Since cytokines play a central role in the initiation and development of inflammation, we evaluated the presence of proinflammatory cytokines and chemokines in AIR patient sera. We demonstrate that IL-6 and CXCL9 are both elevated in AIR patient sera. Moreover, the presence and concentration of these 2 molecules appear to correlate with AIR patient disease severity. This cytokine profile, IL-6 and CXCL9, has been described to participate in a variety of autoimmune and inflammatory diseases. Our study provides support for an activated inflammatory process in AIR and identifies possible mechanisms that can drive autoimmunity in this disease.

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IL-6 and CXCL9 are both elevated in AIR patient sera.

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The presence and concentration of IL-6 and CXCL9 correlate with AIR patient disease severity.

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These cytokines may play a prominent role in the initiation and development of inflammation and autoimmunity.

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The data provides evidence for activated inflammatory processes in AIR.

Defining biological subsets in systemic lupus erythematosus: progress toward personalized therapy

Systemic lupus erythematosus (SLE) is a heterogeneous disease with respect to disease severity, response to treatment, and organ damage. The pathogenesis of SLE includes immunological mechanisms which are driven by both genetic and environmental factors. There are clear differences in the pathogenesis of SLE between patients of different ancestral backgrounds, including differences in genetic risk factors, immunological parameters, and clinical manifestations. Patients with high vs. low levels of type I interferon (IFN) in circulation represents one major biological subset within SLE, and these two groups of patients are present in all ancestral backgrounds. Genetic factors, autoantibodies, and levels of other cytokines all differ between high and low IFN patients. This distinction has also been important in predicting response to treatment with anti-type I IFN therapies, providing a precedent in SLE for biological subsets predicting treatment response. This review will highlight some recent developments in defining biological subsets of SLE based on disease pathophysiology, and the idea that improved knowledge of disease heterogeneity will inform our efforts to personalize therapy in this disease.