Kyriakos A. Kirou

Microarray analysis of interferon-regulated genes in SLE.

Altered regulation of interferon-α (IFNα) in systemic lupus erythematosus (SLE) was first demonstrated nearly 25 years ago. However, only recently has due attention been directed towards the central role of this cytokine family in SLE. Several laboratories have used large-scale microarray technology to study global gene expression patterns in heterogeneous populations of peripheral blood cells from lupus patients and control subjects. The results of these studies demonstrate that IFN-regulated genes are among the most significantly overexpressed in SLE mononuclear cells. In view of the protean effects of IFNs on immune system function, increased activity of IFNs may account for many of the immune system alterations that characterize SLE and contribute to autoimmunity. Definition of the nature of the major IFNs, or other factors, that drive the IFN-regulated gene expression signature noted in SLE is an important area for investigation that may lead to new approaches to targeted therapy of SLE.

Safety profile and clinical activity of sifalimumab, a fully human anti-interferon α monoclonal antibody, in systemic lupus erythematosus: a phase I, multicentre, double-blind randomised study

Background Type I interferons (IFNs) appear to play a central role in disease pathogenesis in systemic lupus erythematosus (SLE), making them potential therapeutic targets. Methods Safety profile, pharmacokinetics, immunogenicity, pharmacodynamics and clinical activity of sifalimumab, an anti-IFNα monoclonal antibody, were assessed in a phase I, multicentre, randomised, double-blind, dose-escalation study with an open-label extension in adults with moderately active SLE. Subjects received one intravenous dose of sifalimumab (n=33 blinded phase, 0.3, 1, 3, 10 or 30 mg/kg; n=17 open-label, 1, 3, 10 or 30 mg/kg) or placebo (n=17). Each phase lasted 84 days. Results Adverse events (AEs) were similar between groups; about 97% of AEs were grade 1 or 2. All grade 3 and 4 AEs and all serious AEs (2 placebo, 1 sifalimumab) were deemed unrelated to the study drug. No increase in viral infections or reactivation was observed. Sifalimumab caused dose-dependent inhibition of type I IFN-induced mRNAs (type I IFN signature) in whole blood and corresponding changes in related proteins in affected skin. Exploratory analyses showed consistent trends toward improvement in disease activity in sifalimumab-treated versus placebo-treated subjects. A lower proportion of sifalimumab-treated subjects required new or increased immunosuppressive treatments (12% vs 41%; p=0.03) and had fewer Systemic Lupus Erythematosus Disease Activity Index flares (3% vs 29%; p=0.014). Conclusions Sifalimumab had a safety profile that supports further clinical development. This trial demonstrated that overexpression of type I IFN signature in SLE is at least partly driven by IFNα, and exploratory analyses suggest that IFNα inhibition may be associated with clinical benefit in SLE. Trial registration number NCT00299819.

Cutting Edge: Autoimmune Disease Risk Variant of STAT4 Confers Increased Sensitivity to IFN-α in Lupus Patients In Vivo

Increased IFN-α signaling is a primary pathogenic factor in systemic lupus erythematosus (SLE). STAT4 is a transcription factor that is activated by IFN-α signaling, and genetic variation of STAT4 has been associated with risk of SLE and rheumatoid arthritis. We measured serum IFN-α activity and simultaneous IFN-α-induced gene expression in PBMC in a large SLE cohort. The risk variant of STAT4 (T allele; rs7574865) was simultaneously associated with both lower serum IFN-α activity and greater IFN-α-induced gene expression in PBMC in SLE patients in vivo. Regression analyses confirmed that the risk allele of STAT4 was associated with increased sensitivity to IFN-α signaling. The IFN regulatory factor 5 SLE risk genotype was associated with higher serum IFN-α activity; however, STAT4 showed dominant influence on the sensitivity of PBMC to serum IFN-α. These data provide biologic relevance for the risk variant of STAT4 in the IFN-α pathway in vivo.

Elevated levels and functional capacity of soluble CD40 ligand in systemic lupus erythematosus sera.

OBJECTIVE To measure soluble CD40 ligand (sCD40L) in sera from patients with systemic lupus erythematosus (SLE) and to study the functional capacity of sCD40L in mediating B cell activation. METHODS A 2-site enzyme-linked immunosorbent assay (ELISA) was used to measure sCD40L in the sera of 66 SLE patients, 30 disease control patients, and 23 healthy subjects. Induction of B cell activation antigen expression was used to assess the functional capacity of sCD40L in SLE sera. RESULTS The mean concentration of sCD40L was statistically significantly higher (P < 0.0001) in SLE patients than in disease controls or healthy subjects, and segregation of SLE patients by severe, moderate, or mild extent of disease showed a relationship between disease severity and sCD40L concentration. Western blot analysis demonstrated the presence of the 18-kd band of sCD40L in SLE sera, and the results of a 1-site ELISA protocol suggested that some of the product in SLE sera was present in dimer or trimer form. Functional studies showed that 10 ng/ml of recombinant CD40L, a level present in some SLE sera, induced increased expression of CD95 on B cells. Several SLE sera also induced CD95 or CD86 on Ramos B cells, a result that was inhibited by anti-CD40L monoclonal antibodies. CONCLUSION The soluble form of CD40L is present in the sera of most patients with SLE and may have the capacity to mediate B cell activation. Aberrant expression of CD40L might be predicted to result in activation of bystander B cells, including those that have encountered self antigens, and to contribute to autoantibody secretion.

Imatinib mesylate (Gleevec) in the treatment of diffuse cutaneous systemic sclerosis: results of a 1-year, phase IIa, single-arm, open-label clinical trial

Objective To assess the safety and effectiveness of imatinib mesylate in the treatment of diffuse cutaneous systemic sclerosis (dcSSc). Methods In this phase IIa, open-label, single-arm clinical trial, 30 patients with dcSSc were treated with imatinib 400 mg daily. Patients were monitored monthly for safety assessments. Modified Rodnan skin scores (MRSS) were assessed every 3 months. Pulmonary function testing, chest radiography, echocardiography and skin biopsies were performed at baseline and after 12 months of treatment. Results Twenty-four patients completed 12 months of therapy. 171 adverse events (AE) with possible relation to imatinib were identified; 97.6% were grade 1 or 2. Twenty-four serious AE were identified, two of which were attributed to study medication. MRSS decreased by 6.6 points or 22.4% at 12 months (p=0.001). This change was evident starting at the 6-month time point (Δ=−4.5; p<0.001) and was seen in patients with both early and late-stage disease. Forced vital capacity (FVC) improved by 6.4% predicted (p=0.008), and the diffusion capacity remained stable. The improvement in FVC was significantly greater in patients without interstitial lung disease. Health-related quality of life measures improved or remained stable. Blinded dermatopathological analysis confirmed a significant decrease in skin thickness and improvement in skin morphology. Conclusions Treatment with imatinib was tolerated by most patients in this cohort. Although AE were common, most were mild to moderate. In this open-label experience, improvements in skin thickening and FVC were observed. Further investigation of tyrosine kinase inhibition for dcSSc in a double-blind randomised placebo controlled trial is warranted. ClinicalTrials.gov, NCT00555581

Interferon-α in systemic lupus erythematosus

Purpose of review To describe the lines of evidence supporting a significant role for interferon-α (IFNα) in the pathogenesis of systemic lupus erythematosus (SLE) and to propose potential mechanisms by which IFNα contributes to the autoimmunity and immune dysfunction of SLE. Recent findings Long-standing data indicating elevated levels of IFNα in the circulation of patients with SLE have recently been supplemented by reports from clinical practice, gene expression data, analysis of patient cells studied ex vivo, and studies of mechanisms of induction of IFNα production to provide complementary data strongly supporting a pathogenic role for IFNα in SLE. Recombinant IFNα, when administered as a therapy to patients with malignancy or hepatitis infection, can induce SLE. IFNα-regulated genes are highly expressed in SLE peripheral blood cells compared with cells from control subjects. Functional alterations of SLE mononuclear cells have been attributed to effects of IFNα. In addition, immune complexes bearing lupus autoantibodies and RNA or DNA have been shown to induce IFNα production. Finally, progress in understanding the role of Toll-like receptors (TLR) in the activation of the innate immune response has suggested potential mechanisms by which adjuvant-like factors act through TLR to induce IFNα as well as effective processing of self-antigens, resulting in activation of an adaptive immune response directed against self, as well as cytokine-mediated immune dysfunction. Summary Substantial evidence supports a significant role for IFNα in the pathogenesis of lupus. The IFNα pathway represents a promising target for therapeutic intervention in patients with SLE.

Felty's syndrome autoantibodies bind to deiminated histones and neutrophil extracellular chromatin traps

OBJECTIVE To test the hypothesis that autoantigen modifications by peptidylarginine deiminase type 4 (PAD-4) increase immunoreactivity. METHODS We assembled sera from patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Feltys syndrome (FS), and antineutrophil cytoplasmic antibody-associated vasculitides (AAVs), as well as sera from control subjects without autoimmune diseases. The sera were tested for binding to activated neutrophils, deiminated histones, and neutrophil extracellular chromatin traps (NETs). IgG binding to lipopolysaccharide-activated neutrophils was assessed with confocal microscopy, and binding to in vitro-deiminated histones was measured using enzyme-linked immunosorbent assay (ELISA) and Western blotting. In addition, we quantitated histone deimination in freshly isolated neutrophils from the blood of patients and control subjects. RESULTS Increased IgG reactivity with activated neutrophils, particularly binding to NETs, was paralleled by preferential binding to deiminated histones over nondeiminated histones by ELISA in a majority of sera from FS patients but only in a minority of sera from SLE and RA patients. Immunoblotting revealed autoantibody preference for deiminated histones H3, H4, and H2A in most FS patients and in a subset of SLE and RA patients. In patients with AAVs, serum IgG preferentially bound nondeiminated histones over deiminated histones. Increased levels of deiminated histones were detected in neutrophils from RA patients. CONCLUSION Circulating autoantibodies in FS are preferentially directed against PAD-4-deiminated histones and bind to activated neutrophils and NETs. Thus, increased reactivity with modified autoantigens in FS implies a direct contribution of neutrophil activation and the production of NET-associated nuclear autoantigens in the initiation or progression of FS.

Relationship between the type I interferon signature and the response to rituximab in rheumatoid arthritis patients

OBJECTIVE To analyze the relationship between the type I interferon (IFN) signature and clinical response to rituximab in rheumatoid arthritis (RA) patients. METHODS Twenty RA patients were treated with rituximab (cohort 1). Clinical response was defined as a decrease in the Disease Activity Score evaluated in 28 joints (DAS28) and as a response according to the European League Against Rheumatism (EULAR) criteria at week 12 and week 24. The presence of an IFN signature was analyzed in peripheral blood mononuclear cells by measuring the expression levels of 3 IFN response genes by quantitative polymerase chain reaction analysis. After comparison with the findings in healthy controls, patients were classified as having an IFN high or an IFN low signature. The data were confirmed in a second independent cohort (n = 31). Serum IFNα bioactivity was analyzed using a reporter assay. RESULTS In cohort 1, there was a better clinical response to rituximab in the IFN low signature group. Consistent with these findings, patients with an IFN low signature had a significantly greater reduction in the DAS28 and more often achieved a EULAR response at weeks 12 and 24 as compared with the patients with an IFN high signature in cohort 2 versus cohort 1. The pooled data showed a significantly stronger decrease in the DAS28 in IFN low signature patients at weeks 12 and 24 as compared with the IFN high signature group and a more frequent EULAR response at week 12. Accordingly, serum IFNα bioactivity at baseline was inversely associated with the clinical response, although this result did not reach statistical significance. CONCLUSION The type I IFN signature negatively predicts the clinical response to rituximab treatment in patients with RA. This finding supports the notion that IFN signaling plays a role in the immunopathology of RA.

Autoimmune Disease Risk Variant of IFIH1 Is Associated with Increased Sensitivity to IFN-α and Serologic Autoimmunity in Lupus Patients

Increased IFN-α signaling is a heritable risk factor for systemic lupus erythematosus (SLE). IFN induced with helicase C domain 1 (IFIH1) is a cytoplasmic dsRNA sensor that activates IFN-α pathway signaling. We studied the impact of the autoimmune-disease–associated IFIH1 rs1990760 (A946T) single nucleotide polymorphism upon IFN-α signaling in SLE patients in vivo. We studied 563 SLE patients (278 African-American, 179 European-American, and 106 Hispanic-American). Logistic regression models were used to detect genetic associations with autoantibody traits, and multiple linear regression was used to analyze IFN-α–induced gene expression in PBMCs in the context of serum IFN-α in the same blood sample. We found that the rs1990760 T allele was associated with anti-dsDNA Abs across all of the studied ancestral backgrounds (meta-analysis odds ratio = 1.34, p = 0.026). This allele also was associated with lower serum IFN-α levels in subjects who had anti-dsDNA Abs (p = 0.0026). When we studied simultaneous serum and PBMC samples from SLE patients, we found that the IFIH1 rs1990760 T allele was associated with increased IFN-induced gene expression in PBMCs in response to a given amount of serum IFN-α in anti-dsDNA–positive patients. This effect was independent of the STAT4 genotype, which modulates sensitivity to IFN-α in a similar way. Thus, the IFIH1 rs1990760 T allele was associated with dsDNA Abs, and in patients with anti-dsDNA Abs this risk allele increased sensitivity to IFN-α signaling. These studies suggest a role for the IFIH1 risk allele in SLE in vivo.

Age- and gender-specific modulation of serum osteopontin and interferon-α by osteopontin genotype in systemic lupus erythematosus.

Osteopontin (OPN) is a multifunctional cytokine involved in long bone remodeling and immune system signaling. Additionally, OPN is critical for interferon-α (IFN-α) production in murine plasmacytoid dendritic cells. We have previously shown that IFN-α is a heritable risk factor for systemic lupus erythematosus (SLE). Genetic variants of OPN have been associated with SLE susceptibility, and one study suggests that this association is particular to men. In this study, the 3′ UTR SLE-risk variant of OPN (rs9138C) was associated with higher serum OPN and IFN-α in men (P=0.0062 and P=0.0087, respectively). In women, the association between rs9138 C and higher serum OPN and IFN-α was restricted to younger subjects, and risk allele carriers showed a strong age-related genetic effect of rs9138 genotype on both serum OPN and IFN-α (P<0.0001). In African-American subjects, the 5′ region single nucleotide polymorphisms, rs11730582 and rs28357094, were associated with anti-RNP antibodies (odds ratio (OR)=2.9, P=0.0038 and OR=3.9, P=0.021, respectively). Thus, we demonstrate two distinct genetic influences of OPN on serum protein traits in SLE patients, which correspond to previously reported SLE-risk variants. This study provides a biologic relevance for OPN variants at the protein level, and suggests an influence of this gene on the IFN-α pathway in SLE.