Coordinate overexpression of interferon‐α–induced genes in systemic lupus erythematosus

Objective

To study the contribution of interferon‐α (IFNα) and IFNγ to the IFN gene expression signature that has been observed in microarray screens of peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE).

Methods

Quantitative real‐time polymerase chain reaction analysis of healthy control PBMCs was used to determine the relative induction of a panel of IFN‐inducible genes (IFIGs) by IFNα and IFNγ. PBMCs from 77 SLE patients were compared with those from 22 disease controls and 28 healthy donors for expression of IFIGs.

Results

Expression of IFNα‐inducible genes was significantly higher in SLE PBMCs than in those from disease controls or healthy donors. The level of expression of all IFIGs in PBMCs from SLE patients with IFNα pathway activation correlated highly with the inherent responsiveness of those genes to IFNα, suggesting coordinate activation of that cytokine pathway. Expression of genes preferentially induced by IFNγ was not significantly increased in SLE PBMCs compared with control PBMCs. IFNα‐regulated gene‐inducing activity was detected in some SLE plasma samples.

Conclusion

The coordinate activation of IFNα‐induced genes is a characteristic of PBMCs from many SLE patients, supporting the hypothesis that IFNα is the predominant stimulus for IFIG expression in lupus.

     

Association of endogenous anti–interferon‐α autoantibodies with decreased interferon‐pathway and disease activity in patients with systemic lupus erythematosus

Objective

Numerous observations implicate interferon‐α (IFNα) in the pathophysiology of systemic lupus erythematosus (SLE); however, the potential impact of endogenous anti‐IFNα autoantibodies (AIAAs) on IFN‐pathway and disease activity is unclear. The aim of this study was to characterize IFN‐pathway activity and the serologic and clinical profiles of AIAA‐positive patients with SLE.

Methods

Sera obtained from patients with SLE (n = 49), patients with rheumatoid arthritis (n = 25), and healthy control subjects (n = 25) were examined for the presence of AIAAs, using a biosensor immunoassay. Serum type I IFN bioactivity and the ability of AIAA‐positive sera to neutralize IFNα activity were determined using U937 cells. Levels of IFN‐regulated gene expression in peripheral blood were determined by microarray, and serum levels of BAFF, IFN‐inducible chemokines, and other autoantibodies were measured using immunoassays.

Results

AIAAs were detected in 27% of the serum samples from patients with SLE, using a biosensor immunoassay. Unsupervised hierarchical clustering analysis identified 2 subgroups of patients, IFN^low and IFN^high, that differed in the levels of serum type I IFN bioactivity, IFN‐regulated gene expression, BAFF, anti–ribosomal P, and anti‐chromatin autoantibodies, and in AIAA status. The majority of AIAA‐positive patients had significantly lower levels of serum type I IFN bioactivity, reduced downstream IFN‐pathway activity, and lower disease activity compared with the IFN^high patients. AIAA‐positive sera were able to effectively neutralize type I IFN activity in vitro.

Conclusion

Patients with SLE commonly harbor AIAAs. AIAA‐positive patients have lower levels of serum type I IFN bioactivity and evidence for reduced downstream IFN‐pathway and disease activity. AIAAs may influence the clinical course in SLE by blunting the effects produced by IFNα.

     

The development of systemic lupus erythematosus following interferon‐α therapy for hepatitis C infection

Interferon‐alpha (IFN‐α) therapy has been associated with de novo development of systemic lupus erythematosus (SLE), and discontinuation of IFN‐α resulted in disease resolution in most patients. Recurrence of SLE in the absence of concomitant IFN‐α therapy has not been reported. We present here a woman who developed overt clinical manifestations of SLE one year after withdrawal of IFN‐α therapy for hepatitis C virus (HCV) infection. This report highlights the importance of long‐term follow‐up for the belated development of SLE in patients who have experienced IFN‐α induced autoimmune phenomena.     

Activation of the interferon‐γ signaling pathway in systemic lupus erythematosus peripheral blood mononuclear cells

Objective

To investigate interferon‐γ (IFNγ) signaling in peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE) by analyzing IFNγ receptor (IFNγR) expression, STAT‐1 expression and phosphorylation, and the regulation of IFNγ‐inducible genes.

Methods

Fluorocytometry was used to investigate expression of STAT‐1, pSTAT‐1, CD95, HLA–DR, class I major histocompatibility complex (MHC), IFNγ‐inducible 10‐kd protein (IP‐10), monokine induced by IFNγ (Mig), and IFNγR in PBMCs from SLE patients and healthy individuals. STAT‐1 phosphorylation was determined by fluorocytometry and Western blotting after stimulation with IFNα or IFNγ. Quantitative polymerase chain reaction was used to assess messenger RNA (mRNA) expression of the IFNγ‐inducible genes IP‐10 and Mig shortly after preparation or after stimulation with IFNγ in monocytes.

Results

STAT‐1 expression was increased in PBMCs from SLE patients and correlated significantly with disease activity and with the IFN‐inducible expression of CD95 and HLA–DR. STAT‐1 expression also showed a trend toward association with class I MHC expression. In addition, the expression of other IFNγ‐inducible genes, such as IP‐10 or Mig, was increased in SLE monocytes. While STAT‐1 phosphorylation in SLE PBMCs and PBMCs from healthy individuals was similar after IFNα stimulation, incubation with IFNγ induced STAT‐1 phosphorylation only in SLE lymphocytes. Moreover, SLE monocytes showed a considerably higher increase in pSTAT‐1 expression upon IFNγ stimulation than monocytes from healthy individuals. Increased responsiveness of SLE monocytes to IFNγ was also confirmed on the mRNA level, where expression of the IFN‐inducible, STAT‐1–dependent genes IP‐10 and Mig was more efficiently increased in SLE cells. However, IFNγR was similarly expressed on SLE lymphocytes and monocytes and those from healthy individuals.

Conclusion

In addition to supporting the role of IFNs in SLE immunopathogenesis in general, the findings of the present study support a role of IFNγ in this disease.

     

Anti–β2‐glycoprotein I antibodies in pediatric systemic lupus erythematosus and antiphospholipid syndrome

Objective

To determine whether serum β₂‐glycoprotein I antibody (anti‐β₂GPI) detection improves identification of pediatric subjects at risk for antiphospholipid syndrome (APS).

Methods

Serum antiphospholipid antibodies (aPL) were identified by anticardiolipin enzyme‐linked immunosorbent assay (ELISA), lupus anticoagulant assays, and syphilis screening in children with primary APS, systemic lupus erythematosus (SLE), or SLE plus APS. Anti‐β₂GPI level and isotype were determined by β₂GPI ELISA and correlated with clinical manifestations and other aPL assays.

Results

One hundred‐ten subjects under 22 years of age and of mixed ethnicity were evaluated. Fifty‐seven had SLE (including 14 with APS), 25 had primary APS, 16 had SLE‐like APS, 6 were healthy children with aPL detected incidentally, 4 had other rheumatic diseases and 2 had other conditions. Anti‐β₂GPI were detected in 48% of SLE subjects and did not improve aPL detection over standard tests. Anti‐β₂GPI were associated with stroke (P = 0.014), but not with other APS manifestations, and were rarely detected in primary APS. Among subjects with APS manifesting as chronic thrombocytopenia, anti‐β₂GPI distinguished subjects with SLE from those with primary APS.

Conclusions

With the exception of stroke, anti‐β₂GPI detection does not improve identification of pediatric APS over that of traditional aPL assays. Anti‐β₂GPI are rare in pediatric primary APS, but may predict evolution of chronic thrombocytopenia to SLE.

     

Interferon‐α accelerates murine systemic lupus erythematosus in a T cell–dependent manner

Objective

To investigate the mechanism by which interferon‐α (IFNα) accelerates systemic lupus erythematosus (SLE) in (NZB × NZW)F₁ (NZB/NZW) mice.

Methods

NZB/NZW mice were treated with an adenovirus expressing IFNα. In some mice, T cells were depleted with an anti‐CD4 antibody. The production of anti–double‐stranded DNA (anti‐dsDNA) antibodies was measured by enzyme‐linked immunosorbent assay and enzyme‐linked immunospot assay. Germinal centers and antibody‐secreting cells (ASCs) in spleens and IgG deposition and leukocyte infiltrates in kidneys were visualized by immunofluorescence staining. The phenotype of splenic cells was determined by flow cytometry. Finally, somatic hypermutation and gene usage in V_H regions of IgG2a and IgG3 were studied by single‐cell polymerase chain reaction.

Results

IFNα‐accelerated lupus in NZB/NZW mice was associated with elevated serum levels of IgG2 and IgG3 anti‐dsDNA antibodies and accumulation of many IgG ASCs in the spleen, which did not develop into long‐lived plasma cells. Furthermore, IgG2a and IgG3 antibodies in the mice were highly somatically mutated and used distinct repertoires of V_H genes. The induction of SLE in the mice was associated with an increase in B cell Toll‐like receptor 7 expression, increased serum levels of BAFF, interleukin‐6 (IL‐6), and tumor necrosis factor α, and induction of T cells expressing IL‐21. Although IFNα drove a T cell–independent increase in serum levels of IgG, autoantibody induction and the development of nephritis were both completely dependent on CD4+ T cell help.

Conclusion

These findings demonstrate that, although IFNα activates both innate and adaptive immune responses in NZB/NZW mice, CD4+ T cells are necessary for IFNα‐driven induction of anti‐dsDNA antibodies and clinical SLE.

     

Network analysis of associations between serum interferon‐α activity,autoantibodies, and clinical features in systemic lupus erythematosus

Objective

Interferon‐α (IFNα) is a primary pathogenic factor in systemic lupus erythematosus (SLE), and high IFNα levels may be associated with particular clinical manifestations. The prevalence of individual clinical and serologic features differs significantly by ancestry. This study was undertaken to detect associations between clinical and serologic disease manifestations and serum IFNα activity in a large diverse SLE cohort, using multivariate and network analyses.

Methods

We studied 1,089 SLE patients (387 African American, 186 Hispanic American, and 516 European American patients). The presence or absence of individual American College of Rheumatology (ACR) clinical criteria for SLE, autoantibodies, and serum IFNα activity data were analyzed in univariate and multivariate models. Iterative multivariate logistic regression was performed in each ancestral background group separately to establish the network of associations between variables that were independently significant following Bonferroni correction.

Results

In all ancestral backgrounds, high IFNα activity was associated with anti‐Ro and anti–double‐stranded DNA antibodies (P = 4.6 × 10⁻¹⁸ and P = 2.9 × 10⁻¹⁶, respectively). Younger age, non‐European ancestry, and anti‐RNP were also independently associated with increased serum IFNα activity (P ≤ 6.7 × 10⁻⁴). We found 14 unique associations between variables in network analysis, and only 7 of these associations were shared among >1 ancestral background. Associations between clinical criteria were different for different ancestral backgrounds, while autoantibody–IFNα relationships were similar across backgrounds. IFNα activity and autoantibodies were not associated with ACR clinical features in multivariate models.

Conclusion

Our findings indicate that serum IFNα activity is strongly and consistently associated with autoantibodies, and not independently associated with clinical features in SLE. IFNα may be more relevant to humoral tolerance and initial pathogenesis than later clinical disease manifestations.

     

Intravenous immunoglobulin abrogates dendritic cell differentiation induced by interferon‐α present in serum from patients with systemic lupus erythematosus

Objective

Alterations in the function of dendritic cells (DCs) may explain the systemic autoimmune responses that characterize systemic lupus erythematosus (SLE). Even though several reports have documented the beneficial effect of intravenous immunoglobulin (IVIG) in SLE, the underlying mechanisms of action remain poorly understood. Considering the effect of serum factors, including interferon‐α (IFNα), on the activity of DCs, we investigated the effects of IVIG on the differentiation of DCs mediated by serum from SLE patients.

Methods

DCs were differentiated from peripheral blood monocytes obtained from SLE patients and from healthy blood donors, in the presence of SLE serum. IVIG was used at a concentration of 0.15 mM. A functional assay was performed to assess the inhibitory effect of IVIG on the uptake of nucleosomes by DCs.

Results

IVIG interfered with the differentiation of DCs from SLE patients and healthy donors cultured in the presence of SLE serum. Treatment of DCs with IVIG inhibited the ingestion of nucleosomes by immature DCs, by up to 36%.

Conclusion

The present findings indicate that IVIG, by down‐regulating the IFNα‐mediated differentiation of DCs and by inhibiting uptake of nucleosomes, may exert an essential immunoregulatory effect in SLE patients at the onset of the immune response, at the DC level. Given the critical role of HLA molecules and the costimulatory signals delivered by CD80 and CD86 in optimal antigen presentation and T cell activation, inhibition of expression of HLA and CD80/CD86 on DCs by IVIG offers a plausible explanation for the efficacy of IVIG in SLE and other immune‐mediated inflammatory conditions.

     

Interferon‐α–inducible proteins are novel autoantigens in murine lupus

Objective

To investigate the spectrum of B cell autoimmunity in the recently described anti‐CD1–autoreactive T cell receptor (TCR)–transgenic murine lupus‐like (CD1 lupus‐like) model.

Methods

Lethally irradiated BALB/c/nu/nu mice were injected intravenously with donor BALB/c bone marrow and spleen cells expressing TCRα and TCRβ transgenes that recognize CD1d. Sera from adoptive host animals that developed lupus (i.e., CD1 lupus mice) were collected at serial time points and analyzed by Western blotting and immunoprecipitation, using protein extracts prepared from NIH3T3 mouse fibroblasts and EL‐4 lymphocytes, respectively. Sera obtained from older animals in several models of spontaneous lupus (NZB/NZW, MRL++, and MRL/lpr mice), unmanipulated BALB/c/nu/nu mice, and normal BALB/c mice were used as controls.

Results

Analyses demonstrated that the prominent targets of autoantibodies in the CD1 lupus‐like model are interferon‐α (IFNα)–inducible antigens. Biochemical and serologic characterizations identified one antigen as belonging to the interferon‐inducible 202 (Ifi202) subfamily of proteins within the Ifi200 family, and a second antigen as a member of the 70‐kd heat‐shock protein family. Autoantibodies directed against these antigens were rapidly produced at an early stage of disease. Anti‐p50 autoantibodies were present in sera from 7 (78%) of 9 CD1 lupus mice that developed severe kidney disease.

Conclusion

IFNα‐inducible proteins represent a novel class of autoantigens in murine lupus, and the findings suggest additional roles for IFNα in this disease. Since Ifi202 autoantigens are encoded by the murine non–major histocompatibility complex lupus‐susceptibility gene locus Ifi202, these data provide a link between recent advances in lupus genetics and the formation of autoantibodies.

     

Recombinant human anti–transforming growth factor β1 antibody therapy in systemic sclerosis: A multicenter,randomized, placebo‐controlled phase I/II trial of CAT‐192

Objective

To evaluate CAT‐192, a recombinant human antibody that neutralizes transforming growth factor β1 (TGFβ1), in the treatment of early‐stage diffuse cutaneous systemic sclerosis (dcSSc).

Methods

Patients with SSc duration of <18 months were randomly assigned to the placebo group or to 1 of 3 CAT‐192 treatment groups: 10 mg/kg, 5 mg/kg, 0.5 mg/kg. Infusions were given on day 0 and weeks 6, 12, and 18. The primary objective of this study was to evaluate the safety, tolerability, and pharmacokinetics of CAT‐192. Secondary outcomes included the modified Rodnan skin thickness score (MRSS), the Scleroderma Health Assessment Questionnaire, assessment of organ‐based disease, serum levels of soluble interleukin‐2 receptor, collagen propeptides (N propeptide of type I [PINP] and type III collagen), and tissue levels of messenger RNA for procollagens I and III and for TGFβ1 and TGFβ2.

Results

Forty‐five patients were enrolled. There was significant morbidity and mortality, including 1 death in the group receiving 0.5 mg/kg of CAT‐192 and 3 deaths in the group receiving 5 mg/kg of CAT‐192. There were more adverse events and more serious adverse events in patients receiving CAT‐192 than in those receiving placebo, although these events were not more frequent in the high‐dose treatment group. The MRSS improved in all groups during the study, but there was no evidence of a treatment effect for CAT‐192. Improvement in the MRSS correlated with the disease duration (r = −0.54, P = 0.0008). Changes in the PINP level from baseline correlated with changes in the MRSS (r = 0.37, P = 0.027).

Conclusion

We report the first evaluation of a systemically administered and repeatedly dosed anti‐TGFβ1 drug. In this pilot study, CAT‐192, in doses up to 10 mg/kg, showed no evidence of efficacy. The utility of clinical and biochemical outcome measures and the feasibility of multicenter trials of early dcSSc were confirmed.

     

Association of increased interferon‐inducible gene expression with disease activity and lupus nephritis in patients with systemic lupus erythematosus

Objective

To study 5 type I interferon (IFN)–inducible genes (LY6E, OAS1, OASL, MX1, and ISG15) in patients with systemic lupus erythematosus (SLE) and to correlate expression levels with disease activity and/or clinical manifestations.

Methods

Peripheral blood cells were obtained from 48 SLE patients, 48 normal controls, and 22 rheumatic disease controls, and total RNA was extracted and reverse transcribed into complementary DNA. Gene expression levels were measured by real‐time polymerase chain reaction, standardized to a housekeeping gene, and summed to an IFN score. Disease activity was determined by the Safety of Estrogens in Lupus Erythematosus: National Assessment–Systemic Lupus Erythematosus Disease Activity Index (SELENA‐SLEDAI) composite.

Results

Each gene was highly expressed in SLE patients compared with normal controls (P ≤ 0.0003) or disease controls (P ≤ 0.0008 except for MX1). IFN scores were positively associated with the SELENA‐SLEDAI instrument score (P = 0.001), the SELENA‐SLEDAI flare score (P = 0.03), and the physician's global assessment score (P = 0.005). Compared with patients without nephritis, lupus nephritis patients had higher IFN scores (overall P < 0.0001), especially during active renal disease. IFN scores were weakly associated with neurologic manifestations. Elevated IFN scores were positively associated with the current presence of anti–double‐stranded DNA (anti‐dsDNA) antibodies (P = 0.007) or hypocomplementemia (P = 0.007). LY6E expression levels distinguished active from inactive lupus nephritis (P = 0.02) and were positively associated with proteinuria (P = 0.009).

Conclusion

The 5 IFN‐inducible genes were highly expressed in SLE patients, and increased levels were correlated with disease activity defined by several methods. IFN scores, or LY6E levels, were elevated in lupus nephritis patients, especially during active renal disease, and in patients with anti‐dsDNA antibody positivity and hypocomplementemia. IFN scores, or LY6E levels, may be useful as a biomarker for lupus nephritis therapy.

     

Activation of the interferon‐α pathway identifies a subgroup of systemic lupus erythematosus patients with distinct serologic features and active disease

Objective

Gene‐expression studies have demonstrated increased expression of interferon (IFN)–inducible genes (IFIGs) in peripheral blood mononuclear cells (PBMCs) of many patients with systemic lupus erythematosus (SLE), with a predominant effect of type I IFN. This study examined the hypothesis that increased disease severity and activity, as well as distinct autoantibody specificities, characterize SLE patients with activation of the type I IFN pathway.

Methods

Freshly isolated PBMCs from 77 SLE patients, 22 disease controls, and 28 healthy donors were subjected to real‐time polymerase chain reaction for 3 IFIGs that are preferentially induced by IFNα, and the data were used to derive IFNα scores for all individuals. Expression of IFIGs was significantly higher in SLE patients compared with disease controls or healthy donors. SLE patients with high and low IFNα scores were compared for clinical manifestations of disease, disease severity, disease activity, serologic features, and potential confounders, by bivariate and multivariate analyses.

Results

SLE patients with a high IFNα score had a significantly higher prevalence of renal disease, a greater number of American College of Rheumatology criteria for SLE, and a higher Systemic Lupus International Collaborating Clinics damage index (SDI) score than did SLE patients with low IFNα scores. Patients with high scores showed increased disease activity, as measured by lower C3 levels, hemoglobin levels, absolute lymphocyte counts, and albumin levels, and a higher anti–double‐stranded DNA (dsDNA) titer, erythrocyte sedimentation rate, and SLE Disease Activity Index 2000 score. The presence of antibodies specific for Ro, U1 RNP, Sm, and dsDNA, but not phospholipids, was significantly associated with a high IFNα score. Logistic regression analysis confirmed that renal disease, higher SDI scores, low complement levels, and presence of anti–RNA binding protein (RBP) autoantibodies were associated with a high IFNα score.

Conclusion

Activation of the IFNα pathway defines a subgroup of SLE patients whose condition is characterized by increased disease severity, including renal disease, increased disease activity, reflected in complement activation, and autoreactivity to RBP.

     

Interferon-γ–inducible protein p16. a new target of antinuclear antibodies in patients with systemic lupus erythematosus

Objective. To determine the cellular expression and localization of interferon-γ (IFNγ)–inducible protein p16, a new antigen specificity of antinuclear antibodies (ANA), and to evaluate the prevalence of anti-p16, particularly in SLE patients. Methods. Serum levels of anti-p16 were determined by immunoblotting with recombinant p16 and cellular p16 messenger RNA (mRNA) by Northern blotting. We also utilized immunoprecipitation of ³⁵Smethionine–labeled proteins, immunostaining of blotted proteins of subcellular fractions, and immunofluorescence studies with affinity-purified rabbit and human anti–recombinant p16. Results. Protein p16 was localized within the nucleolus and nucleoplasm and constitutively expressed in Raji, HeLa, HEp-2, K562, and HL-60 cells. Synthesis of mRNA and protein was increased in the presence of IFNγ. The prevalence of anti-p16 was 29% in 374 SLE patients (35% in those positive for anti–double-stranded DNA) and 0% in 188 healthy individuals. Anti-p16 was always accompanied by positive findings on indirect immunofluorescence for ANA. Conclusion. Anti-p16 represents a main ANA specificity. Anti-p16 may help to elucidate IFNγ-dependent nuclear processes and to link autoantibody production to states of IFNγ activation.