Targeting interferon-α: a promising approach for systemic lupus erythematosus therapy

Theory, targets and therapy in systemic lupus erythematosus

The treatment of systemic lupus erythematosus (SLE) has been refined over the years, with the recognition that a fine balance lies between aggressive and prompt therapy and attendant complications brought upon by immunosuppressive therapy itself. However, there has been limited change to the repertoire of drugs available to treat this challenging disease. The current standard therapy for severe manifestations of SLE includes the use of high-dose corticosteroids and cytotoxic agents such as cyclophosphamide (CYC), which have been associated with an increased risk of serious and opportunistic infections. The need for safer, more targeted therapies has been recognized and now, with the exponential increase in the understanding of immunopathogenic mechanisms in SLE, the way has been paved for the development of biologic or targeted therapies in SLE. Although the potential immunosuppression, long-term safety issues and cost-effectiveness remain unclear. These targeted therapies may range from small molecules that specifically inhibit inflammatory processes at an intracellular, cell-cell or cell-matrix level to monoclonal antibodies, soluble receptors or natural antagonists that interfere with cytokine function, cellular activation and inflammatory gene transcription.

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.

Drug-induced lupus

INTRODUCTION

Drug-induced lupus (DIL) refers to an idiosyncratic side effect of numerous, apparently unrelated, medications, in which symptoms overlap with those of systemic lupus erythematosus. DIL is reversible by discontinuation of the medication. The etiological mechanism underlying DIL is linked to the inherent susceptibility of the adaptive immune system to lapse into auto-reactivity.

AREAS COVERED

Clinical and laboratory features of DIL will be compared with those of idiopathic systemic lupus and with other types of drug reactions with overlapping features. Formerly commonly-used drugs conferred very high risk of developing DIL, although the probability of developing DIL has not been established with most lupus-inducing drugs. Pharmacological or physiochemical properties of the parent compounds are uninformative, but the importance of reactive drug metabolites in initiating autoimmunity will be discussed. As with most systemic autoimmune diseases, the pathogenesis of DIL is complex and obscure. The role of complement and human leukocyte allotypes as well as drug acetylator phenotype inform the underlying mechanism, and several of these non-mutually exclusive concepts will be described.

EXPERT OPINION

The pros and cons of proposed mechanisms for DIL will be discussed in the context of current understanding of autoimmunity and immune tolerance to self.

Identification of microRNA-31 as a novel regulator contributing to impaired interleukin-2 production in T cells from patients with systemic lupus erythematosus

OBJECTIVE

MicroRNAs (miRNAs) function to fine-tune the control of immune cell signaling. It is well established that there are abnormalities in the interleukin-2 (IL-2)-related signaling pathways in systemic lupus erythematosus (SLE). The miR-31 microRNA has been found to be markedly underexpressed in patients with SLE, and thus the present study was undertaken to investigate the role of miR-31 in IL-2 defects in lupus T cells.

METHODS

Expression levels of miR-31 were quantitated using TaqMan miRNA assays. Transfection and stimulation of cultured cells followed by TaqMan quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and reporter gene assays were conducted to determine the biologic function of miR-31. NF-AT nuclear translocation and expression were quantitatively measured using an ImageStream cytometer. Bioinformatics analysis, small interfering RNA (siRNA) knockdown, and Western blotting were performed to validate miR-31 targets and effects.

RESULTS

The expression of miR-31 was significantly decreased in lupus T cells, and this was positively correlated with the expression of IL-2. Overexpression of miR-31 in T cells increased the production of IL-2 by altering NF-AT nuclear expression and IL2 promoter activity, while knockdown of endogenous miR-31 reduced IL-2 production. RhoA expression was directly repressed by miR-31 in T cells. Of note, siRNA-mediated knockdown of RhoA enhanced IL2 promoter activity and, consequently, up-regulated IL-2 production. RhoA expression was consistently up-regulated and negatively correlated with the levels of miR-31 in lupus T cells. Manipulation of miR-31 expression in lupus T cells restored the expression of IL-2 at both the messenger RNA and protein levels.

CONCLUSION

MicroRNA-31 is a novel enhancer of IL-2 production during T cell activation. Dysregulation of miR-31 and its target, RhoA, could be a novel molecular mechanism underlying the IL-2 deficiency in patients with SLE.

Interferons as biomarkers and effectors: lessons learned from animal models

Interferons (IFNs) comprise type I, II and III families with multiple subtypes. Via transcription of IFN-stimulated genes (ISGs), IFNs can exert multiple biological effects on the cell. In infectious and chronic inflammatory diseases, the IFNs and their ISG sets can be potentially utilized as biomarkers of disease outcome. Animal models allow investigations into disease pathogenesis and gene knockout models have proved cause and effect relationships of molecules related to the IFN response. Sets of IFN subtypes and their ISG products provide immunological signature patterns for different viral and other diseases. In this article, we give an overview of IFNs in several virus infection models and autoimmune diseases of medical relevance. Lessons learned from animal models inform us of IFN system parameters as indicators of disease outcome and whether clinical research is warranted. Moreover, validated IFN biomarkers for prognosis enhance our understanding of therapeutic and vaccine development.

Complement receptor 2 is expressed in neural progenitor cells and regulates adult hippocampal neurogenesis

Injury and inflammation are potent regulators of adult neurogenesis. As the complement system forms a key immune pathway that may also exert critical functions in neural development and neurodegeneration, we asked whether complement receptors regulate neurogenesis. We discovered that complement receptor 2 (CR2), classically known as a coreceptor of the B-lymphocyte antigen receptor, is expressed in adult neural progenitor cells (NPCs) of the dentate gyrus. Two of its ligands, C3d and interferon-α (IFN-α), inhibited proliferation of wild-type NPCs but not NPCs derived from mice lacking Cr2 (Cr2(-/-)), indicating functional Cr2 expression. Young and old Cr2(-/-) mice exhibited prominent increases in basal neurogenesis compared with wild-type littermates, whereas intracerebral injection of C3d resulted in fewer proliferating neuroblasts in wild-type than in Cr2(-/-) mice. We conclude that Cr2 regulates hippocampal neurogenesis and propose that increased C3d and IFN-α production associated with brain injury or viral infections may inhibit neurogenesis.

Longitudinal expression of type I interferon responsive genes in systemic lupus erythematosus

Cross-sectional studies of patients with systemic lupus erythematosus (SLE) have demonstrated an association between activation of type I interferon (IFN) pathway and disease activity. This study examined longitudinal changes in IFN-regulated gene expression in peripheral blood using microarrays. A cross-section of 66 patients from the Autoimmune Biomarkers Collaborative Network SLE archive was evaluated. We also examined paired samples from a 15 patient subset collected during a period of low disease activity (Baseline) and at a subsequent flare event, and baseline scores of 29 patients who maintained low disease activity. IFN response (IFNr) scores were calculated from three IFN-regulated genes. Overall, higher IFNr scores were associated with increased disease activity. However, IFNr scores were not significantly different between the paired Baseline and Flare samples. An extended longitudinal analysis in 11 patients indicated little change in IFNr scores over time, even during dynamic disease activity. In patients with low disease activity, IFNr scores were not different between patients who experienced a subsequent flare and those who maintained low disease activity. In summary, although higher IFNr scores were associated with greater disease activity, IFNr scores of individual patients did not correlate with changes in disease severity or flare risk.

Detecting shared pathogenesis from the shared genetics of immune-related diseases

Recent genetic studies have revealed shared immunological mechanisms in several immune-related disorders that further our understanding of the development and concomitance of these diseases. Our Review focuses on these shared aspects, using the novel findings of recently performed genome-wide association studies and non-synonymous SNP scans as a starting point. We discuss how identifying new genes that are associated with more than one autoimmune or chronic inflammatory disorder could explain the genetic basis of the shared pathogenesis of immune-related diseases. This analysis helps to highlight the key molecular pathways that are involved in these disorders and the potential roles of novel genes in immune-related diseases.

INTERFEROME: the database of interferon regulated genes

INTERFEROME is an open access database of types I, II and III Interferon regulated genes (http://www.interferome.org) collected from analysing expression data sets of cells treated with IFNs. This database of interferon regulated genes integrates information from high-throughput experiments with annotation, ontology, orthologue sequences from 37 species, tissue expression patterns and gene regulatory information to enable a detailed investigation of the molecular mechanisms underlying IFN biology. INTERFEROME fulfils a need in infection, immunity, development and cancer research by providing computational tools to assist in identifying interferon signatures in gene lists generated by high-throughput expression technologies, and their potential molecular and biological consequences.

Idiopathic inflammatory myopathies: current and future therapeutic options

Idiopathic inflammatory myopathies (notably polymyositis and dermatomyositis) are relatively uncommon diseases with a heterogeneous clinical presentation. Only a few randomized, double-blind, placebo-controlled trials have been performed, measures to assess outcome and response to treatment have to be validated. Initial treatment options of first choice are corticosteroids, although rarely tested in randomized, controlled trials. Unfortunately, not all patients respond to them and many develop undesirable side effects. Thus, second line agents or immunosuppressants given in combination with corticosteroids are used. For dermatomyositis/polymyositis, combination with azathioprine is most common. In case this combination is not sufficient or applicable, intravenous immunoglobulins are justified. Alternative or stronger immunosuppressants, such as cyclosporine A, cyclophosphamide, methotrexate, or mycophenolate are also used. There are no defined guidelines or best treatment protocols agreed on internationally; therefore, the medical approach must be individualized based on the severity of clinical presentation, disease duration, presence of extramuscular features, and prior therapy and contraindications to particular agents. Approximately 25% of patients are nonresponders and continue to experience clinical relapses. Those are candidates for alternative treatment options and experimental therapies. New immunoselective therapies directed toward cytokine modulation, immune cell migration, or modification of certain immune subsets (B- and T-cells) are a promising avenue of research and clinical application. Possible future therapeutic options are presented and discussed.

Blockade of TLR9 agonist-induced type I interferons promotes inflammatory cytokine IFN-gamma and IL-17 secretion by activated human PBMC

Type I interferons (IFN) (IFN-alpha/beta) are recognized as both inhibitors and effectors of autoimmune disease. In multiple sclerosis, IFN-beta therapy appears beneficial, in part, due to its suppression of autoimmune inflammatory Th cell responses. In contrast, in systemic lupus erythematosus (SLE) triggering of plasmacytoid DC (pDC) Toll-like receptors (TLRs) by autoimmune complexes (autoICs) results in circulating type I IFN that appear to promote disease by driving autoantigen presentation and autoantibody production. To investigate how pDC-derived type I IFN might regulate Th cells in SLE, we examined a model in which sustained pDC stimulation by autoICs is mimicked by pretreating normal human PBMC with TLR9 agonist, CpG-A. Subsequently, PBMC Th cells are activated with superantigen, and APC are activated with CD40L. The role of CpG-A/TLR9-induced type I IFN in regulating PBMC is determined by blocking with virus-derived soluble type I IFN receptor, B18R. In summary, pretreatment with either rhIFN-alpha/beta or CpG-A inhibits PBMC secretion of superantigen-induced IFN-gamma and IL-17, and CD40L-induced IL-12p70 and IL-23. B18R prevents these effects. Data indicate that CpG-A-induced type I IFN inhibit IL-12p70-dependent PBMC IFN-gamma secretion by enhancing IL-10. Our results suggest that in SLE, circulating type I IFN may potentially act to inhibit inflammatory cytokine secretion.

Isolation and expression profiling of genes upregulated in the peripheral blood cells of systemic lupus erythematosus patients

We have identified the genes whose expressions are augmented in the blood cells of the patients with systemic lupus erythematosus (SLE) using the 'stepwise subtraction' technique along with microarray analysis. The expression levels of these genes were assessed by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) in 31 SLE patients and 30 healthy controls. We found that the transcription levels of following eight genes were significantly increased in SLE patients; interferon (IFN)-alpha-inducible protein 27 (IFI27), IFN-alpha-inducible protein IFI-15K (G1P2), IFN stimulated gene 20 kDa (ISG20), epithelial stromal interaction 1 (EPSTI1), defensin-alpha (DEFA3), amphiregulin (AREG) and two genes of unknown function (BLAST accession nos AL050290 and AY358224 = SLED1). In comparison with idiopathic thrombocytopenic purpura (ITP), an organ-specific autoimmune disease, IFI27, G1P2 and SLED1 were preferentially upregulated in SLE. In contrast, AREG and AL050290 were more highly expressed in ITP than in SLE. We correlated changes in gene expression and clinical/laboratory features of SLE and found that expression of ISG20, EPSTI1 and SLED1 are significantly correlated with lymphocyte counts. Genes linked to IFN are well known to influence SLE, but several other novel genes unrelated to IFN signaling we report here would be useful to understand the pathophysiology of SLE.

Neonatal lupus and IUGR following alpha-interferon therapy during pregnancy

Interferon alfa-2a is a cytokine produced by recombinant DNA techniques and has antiproliferative, antiviral and immunomodulating effects. A number of case reports in the past have suggested relative safety of alpha-interferons during pregnancy with little or no effect on the fetus. A 15-year-old adolescent became pregnant while receiving alpha-interferon for essential thrombocythemia. She delivered a small-for-gestational age baby girl at 33 weeks gestation. The infant displayed a facial rash characteristic of neonatal lupus and transient thrombocytopenia; maternal and neonatal serologies were typical for drug-induced lupus. These findings suggest probable association between maternal use of alpha interferon and adverse effects in the fetus.