Clinical significance of antibodies to Ro52/TRIM21 in systemic sclerosis

Introduction

Autoantibodies to Ro52 recently identified as TRIM21 are among the most common autoantibodies in systemic autoimmune rheumatic diseases, but their clinical association remains poorly understood. We undertook this study to determine the clinical and serologic associations of anti-Ro52/TRIM21 antibodies in patients with systemic sclerosis (SSc).

Methods

Detailed clinical data and sera from 963 patients with SSc enrolled in a multicenter cohort study were collected and entered into a central database. Antibodies to Ro52/TRIM21 and other autoantibodies were detected with an addressable laser-bead immunoassay and different enzyme-linked immunosorbent assay (ELISA) systems. Associations between anti-Ro52/TRIM21 antibodies and clinical and other serologic manifestations of SSc were investigated.

Results

Anti-Ro52/TRIM21 antibodies were present in 20% of SSc patients and overlapped with other main SSc-related antibodies, including anti-centromere (by immunofluorescence and centromere protein (CENP)-A and CENP-B ELISA), anti-topoisomerase I, anti-RNA polymerase III, and anti-Pm/Scl antibodies. Anti-Ro52/TRIM21 antibodies were strongly associated with interstitial lung disease (odds ratio (OR), 1.53; 95% confidence interval (CI), 1.11 to 2.12; P = 0.0091) and overlap syndrome (OR, 2.06; 95% CI, 1.01 to 4.19; P = 0.0059).

Conclusions

Anti-Ro52/TRIM21 antibodies were the second most common autoantibodies in this SSc cohort. In SSc, anti-Ro52/TRIM21 antibodies may be a marker of interstitial lung disease and overlap syndrome.     

What autoantibody tests should become widely available to help scleroderma diagnosis and management?

Anti-Th/To autoantibodies have been recognized as serological markers of systemic sclerosis (SSc) for more than 20 years. However, validated immunoassay kits to test this specificity have not been commercially available. SSc autoantibodies are basically mutually exclusive and are associated with a certain subset of the disease and/or with organ involvement. Anti-Th/To are generally considered to be markers of the limited cutaneous type of SSc with the involvement of certain internal organs. The excellent correlation between anti-Rpp25 as detected by their novel chemiluminescent method and anti-Th/To as detected by immunoprecipitation suggest that the new assays may become widely available tests for clinicians in future and could help to clarify the clinical significance of anti-Th/To in SSc as well as other conditions over different races or countries.In a previous issue of Arthritis Research & Therapy, Mahler and colleagues reported a novel immunoassay for detecting anti-Th/To autoantibodies [1], which has the potential to make this testing widely available to clinicians using the newly developed ELISA and chemiluminescent immunoassay (CLIA). Serum from patients with systemic autoimmune rheumatic diseases often contains clinically important autoantibodies that react with various intracellular antigens. Detection of anti-nuclear antibodies by indirect immunofluorescence is widely accepted as a screening test for the diagnosis of many systemic autoimmune rheumatic diseases.Systemic sclerosis (SSc) is a disease characterized by collagen deposition and subsequent fibrosis in skin and internal organs. The extent of fibrosis shows considerable variation in severity, which classifies SSc into two distinct subtypes: the limited cutaneous form and the diffuse cutaneous form. Among SSc-associated autoantibodies, anti-centromere antibodies are widely accepted to be associated with limited cutaneous SSc while anti-topoisomerase I and anti-RNA polymerase III (anti-RNAP) antibodies are associated with diffuse cutaneous SSc [2]. In contrast to these three specific antibodies that have been widely used in the diagnosis and management of SSc patients, SSc autoantibodies showing nucleolar immunofluorescence staining pattern have not been utilized. There are two kinds of anti-nucleolar antibodies (ANoA): anti-U3-RNP (fibrillarin) and anti-Th/To [3]. Although they are mainly found in patients with SSc, information on their clinical significances is limited and inconclusive, partly due to a lack of commercially available antibody tests.Mahler and colleagues detected anti-Th/To antibodies using recombinant Rpp25, which is a component of the more than 10 proteins in the Th/To RNA-protein complex [4]. They utilized full-length, purified, recombinant human Rpp25 antigen for the quantitative measurement of anti-Th/To antibodies, which were defined by immunoprecipitation as the reference method. The newly established CLIA showed high sensitivity (100.0% = 8/8) and specificity (99.5% = 365/367) comparable with or better than ELISA. In another cohort, an ELISA indicated three cases showing false-negative anti-Th/To detection, which may be resolved by adding other antigenic components to the coated antigens. In CLIA, two false-positive cases were found, which were ANoA-negative. Evaluation with simultaneous performing anti-nuclear antibodies by indirect immunofluorescence is still important.The coexistence of SSc-marker antibodies in the same patient is rare. ANoA-positive SSc or SSc-suspected patients, who do not have anti-centromere, anti-topoisomerase I, or anti-RNAP antibodies, will be a subset with high probability of having anti-Th/To or antiU3-RNP antibodies. Anti-Th/To antibodies are frequently found in limited cutaneous SSc patients, often those with interstitial lung disease and pulmonary hypertension [2,5], whereas anti-U3-RNP antibodies are associated with pulmonary hypertension, renal disease and myositis in diffuse cutaneous SSc patients [2]. The prevalence of these antibodies in patients with SSc varies for different ethnic backgrounds. For example, in the US SSc cohort, all African-American patients with ANoA-dominant antibodies had anti-U3-RNP, which was found in 30% of all patients, whereas anti-Th/To was found in only 3% [6]. In Caucasian patients, however, anti-Th/To was more frequently found than anti-U3-RNP (9% vs. 4%). In Italian patients, anti-Th/To was found in 4% whereas anti-U3RNP was not found [6]. These antibodies were detected by complicated RNA analysis using immunoprecipitation and silver staining of RNAs or a radioisotope-based immunoprecipitation assay.Some autoantibodies have great diversity in their prevalence among different races and countries, besides the above instances. Recent studies showed that the prevalence of anti-RNAP antibodies was lower in French patients than in the US patients [7]. Anti-Mi-2 antibodies, which are first described as a serological marker of dermatomyositis, were the most common in patients with adult-onset dermatomyositis in Mexico City (59%) [8]. This finding is surprising to us because only 5% of Japanese dermatomyositis patients had anti-Mi-2 antibodies in our study [9]. Commercially available immunoassay kits would make it easier to perform international studies. Since immunoassays using CLIA have very high sensitivity (for example, chemiluminescent ELISA [10]) and are time-saving (for example, beads assay in a liquid phase [1]), the development of such assays would be a reasonable direction for autoantibody immunoassays.SSc specificity and the clinical association of anti-RNAP antibodies have been known for over 20 years; however, until recently, the detection of these antibodies had been utilized only at a few institutions that can perform radioimmunoprecipitation. Since the anti-RNAP ELISA kit became widely available to clinicians, it has now become a part of routine serological tests in SSc. More and more data from different countries have become available, which have illustrated the difference in prevalence and clinical association of anti-RNAP antibodies. Anti-Th/To immunoassay may become utilized in a similar way in future. The newly established method for measuring autoantibodies should be carefully evaluated using large international cohorts of SSc patients and other autoimmune conditions, to establish its utility and clinical significance. In SSc clinics, it will be ideal to have reliable, commercially available immunoassays for major ANoA, anti-Th/To antibodies and anti-U3-RNP antibodies, in addition to anti-PM-Scl antibodies, which are a marker of polymyositis/scleroderma overlap syndrome [1].     

Diagnostic value of anti-topoisomerase I antibodies in a large monocentric cohort

Introduction

In the present study, the detection of anti-topoisomerase I (anti-topo I) autoantibodies was evaluated for diagnosis and risk assessment of systemic sclerosis (SSc) patients in a well characterized large monocentric cohort.

Methods

Sera from patients with SSc (diffuse n = 96, limited n = 113), from patients with overlap syndromes (n = 51), from patients with other diseases associated with SSc (n = 20), as well as from disease controls (n = 487) were analysed for the presence of anti-topo I antibodies by line immunoblot assay and ELISA. Assessment of organ manifestations was performed as proposed by the European Scleroderma Trial and Research network.

Results

The applied test systems for the detection of anti-topo I antibodies revealed a diagnostic sensitivity for SSc of approximately 24% and a diagnostic specificity of at least 99.6%. The sensitivity to identify patients with diffuse SSc amounted to 60%. Patients with anti-topo I antibodies showed a higher burden of skin and lung fibrosis, contractures, electrocardiogram changes, as well as digital ulcers and had more active disease than antibody-negative patients. Signal strengths correlated only weakly with disease activity, with modified Rodnan skin score, with predicted forced vital capacity, and with predicted diffusion capacity levels (P = 0.01, ρ = 0.234, ρ = 0.413, ρ = -0.215, ρ = -0.219). High signal intensities were associated with an increased mortality in diffuse SSc patients (P = 0.003).

Conclusions

Diagnosis and risk assessment of SSc patients can be supported by the detection of anti-topo I antibodies. Signal intensities as obtained by line immunoblot assay or ELISA can be used as a surrogate marker for fibrosis, active disease and worse prognosis.     

Plasma cytokine profiles in systemic sclerosis: associations with autoantibody subsets and clinical manifestations

Introduction  

Systemic sclerosis (SSc) (scleroderma) is a complex autoimmune disease that clinically manifests as progressive fibrosis of the skin and internal organs. Anti-centromere antibodies (ACAs), anti-topoisomerase antibodies (ATAs), and anti-RNA polymerase III antibodies (ARAs) are three mutually exclusive SSc-associated autoantibodies that correlate with distinct clinical subsets characterized by extent of cutaneous involvement and pattern of organ involvement. The current report sought to determine whether plasma cytokine profiles differ in SSc patients grouped according to these SSc-associated autoantibody subsets.     

Clinical and serological evaluation of a novel CENP-A peptide based ELISA

Introduction

Anti-centromere antibodies (ACA) are useful biomarkers in the diagnosis of systemic sclerosis (SSc). ACA are found in 20 to 40% of SSc patients and, albeit with lower prevalence, in patients with other systemic autoimmune rheumatic diseases. Historically, ACA were detected by indirect immunofluorescence (IIF) on HEp-2 cells and confirmed by immunoassays using recombinant CENP-B. The objective of this study was to evaluate a novel CENP-A peptide ELISA.

Methods

Sera collected from SSc patients (n = 334) and various other diseases (n = 619) and from healthy controls (n = 175) were tested for anti-CENP-A antibodies by the novel CENP-A enzyme linked immunosorbent assay (ELISA). Furthermore, ACA were determined in the disease cohorts by IIF (ImmunoConcepts, Sacramento, CA, USA), CENP-B ELISA (Dr. Fooke), EliA^® CENP (Phadia, Freiburg, Germany) and line-immunoassay (LIA, Mikrogen, Neuried, Germany). Serological and clinical associations of anti-CENP-A with other autoantibodies were conducted in one participating centre. Inhibition experiments with either the CENP-A peptide or recombinant CENP-B were carried out to analyse the specificity of anti-CENP-A and -B antibodies.

Results

The CENP-A ELISA results were in good agreement with other ACA detection methods. According to the kappa method, the qualitative agreements were: 0.73 (vs. IIF), 0.81 (vs. LIA), 0.86 (vs. CENP-B ELISA) and 0.97 (vs. EliA^® CENP). The quantitative comparison between CENP-A and CENP-B ELISA using 265 samples revealed a correlation value of rho = 0.5 (by Spearman equation). The receiver operating characteristic analysis indicated that the discrimination between SSc patients (n = 131) and various controls (n = 134) was significantly better using the CENP-A as compared to CENP-B ELISA (P < 0.0001). Modified Rodnan skin score was significantly lower in the CENP-A negative group compared to the positive patients (P = 0.013). Inhibition experiments revealed no significant cross reactivity of anti-CENP-A and anti-CENP-B antibodies. Statistically relevant differences for gender ratio (P = 0.0103), specific joint involvement (Jaccoud) (P = 0.0006) and anti-phospholipid syndrome (P = 0.0157) between ACA positive SLE patients and the entire SLE cohort were observed.

Conclusions

Anti-CENP-A antibodies as determined by peptide ELISA represent a sensitive, specific and independent marker for the detection of ACA and are useful biomarkers for the diagnosis of SSc. Our data suggest that anti-CENP-A antibodies are a more specific biomarker for SSc than antibodies to CENP-B. Furthers studies are required to verify these findings.     

Atypical clinical presentation of a subset of patients with anti-RNA polymerase III - non-scleroderma cases associated with dominant RNA polymerase i reactivity and nucleolar staining

Introduction

Anti-RNA polymerase III (RNAP III) antibodies are highly specific markers of scleroderma (systemic sclerosis, SSc) and associated with a rapidly progressing subset of SSc. The clinical presentation of anti-RNAP III positive patients, onset of Raynaud's phenomenon (RP) and SSc in unselected patients in a rheumatology clinic were evaluated.

Methods

Autoantibodies in sera from 1,966 unselected patients (including 434 systemic lupus erythematosus (SLE), 119 SSc, 85 polymyositis/dermatomyositis (PM/DM)) in a rheumatology clinic were screened by radioimmunoprecipitation. Anti-RNAP III positive sera were also tested by immunofluorescence antinuclear antibodies and anti-RNAP III ELISA. Medical records of anti-RNAP III positive patients were reviewed.

Results

Among 21 anti-RNAP III positive patients, 16 met the American College of Rheumatology (ACR) SSc criteria at the initial visit but 5 did not; diagnoses were vasculitis, early polyarthritis, renal failure with RP, interstitial lung disease, and Sjögren's syndrome. The first two patients developed rapidly progressive diffuse SSc. An additional case presented with diffuse scleroderma without RP and RP developed two years later. Anti-RNAP III antibodies in these 6 cases of atypical clinical presentation were compared with those in 15 cases of typical (SSc with RP) cases. Anti-RNAP III levels by ELISA were lower in the former group (P = 0.04 by Mann-Whitney test) and 3 of 6 were negative versus only 1 of 15 negative in the latter (P < 0.05 by Fisher's exact test). Three cases of non-SSc anti-RNAP III positive patients had predominant reactivity with RNAP I with weak RNAP III reactivity and had a strong nucleolar staining. Three anti-RNAP III patients, who did not have RP at the initial visit, developed RP months later. Scleroderma developed prior to RP in 5 out of 16 (31%) in the anti-RNAP III group, but this was rare in patients with other autoantibodies. The interval between the onset of RP to scleroderma was short in anti-RNAP III positive patients.

Conclusions

Anti-RNAP III antibodies are highly specific for SSc; however, a subset of anti-RNAP III positive patients do not present as typical SSc. The interval between RP and scleroderma in this group is short, and 31% of patients developed scleroderma prior to RP in this group. Anti-RNAP III positive patients may not present as typical SSc and detecting anti-RNAP III may have predictive value.     

A new immunoprecipitation-real time quantitative PCR assay for anti-Th/To and anti-U3RNP antibody detection in systemic sclerosis

Introduction

Classic anti-nucleolar antibodies anti-Th/To and U3 ribonucleoprotein (-U3RNP) can help in the diagnosis, prediction of organ involvement and prognosis in systemic sclerosis (SSc); however, no validated commercial assay is available. We aimed at establishing a novel quantitative real time PCR (qPCR) method to detect these antibodies.

Methods

Standard immunoprecipitation (IP) was performed using K562 cell extract and RNA components were extracted. cDNA was reverse transcribed from RNA components and Th RNA and U3 RNA were detected by qPCR using custom primers. Cycle threshold (Ct) values were compared in a titration experiment to determine the assay efficacy. The new assay was evaluated by testing 22 anti-Th/To and 12 anti-U3RNP positive samples in addition to 88 controls, and the results were compared with IP as a gold standard.

Results

By testing serial 1:8 dilutions of cell lysate as the substrate in the IP step, RNA extracted after IP, and its derived cDNA, linear dose response curves were noted for both anti-Th/To and -U3RNP. With every dilution, Ct values changed approximately three as expected, reflecting the eight-fold difference of cDNA. The Ct difference between positive and negative samples was 8 to 13, which was similar throughout the dilutions. In the specificity analysis, the Ct values of positive samples were clearly different from the negative groups and the results by qPCR had a near perfect correlation with IP.

Conclusions

Our new method readily detects these two clinically important antibodies in SSc. Making tests for anti-Th/To and -U3RNP antibodies widely available to clinicians should be helpful in the diagnosis and follow-up of SSc patients.     

International cohort study of 73 anti-Ku-positive patients: association of p70/p80 anti-Ku antibodies with joint/bone features and differentiation of disease populations by using principal-components analysis

Introduction

An international cohort study of 73 anti-Ku-positive patients with different connective tissue diseases was conducted to differentiate the anti-Ku-positive populations of patients based on their autoantibody profile and clinical signs/symptoms and to establish possible correlations between antibodies against Ku p70 and Ku p80 with autoimmune diseases.

Methods

Sera of anti-Ku-positive patients were collected from six European centers and were all secondarily tested (in the reference center); 73 were confirmed as positive. Anti-Ku antibodies were detected with counter-immunoelectrophoresis (CIE), line immunoassay (LIA), and immunoblot analyses. All clinical and laboratory data were follow-up cumulative data, except for anti-Ku antibodies. Statistical analyses were performed by using R (V 2.12.1). The Fisher Exact test was used to evaluate the association between anti-Ku antibodies and diagnosis, gender, clinical signs, and other observed antibodies. The P values were adjusted for multiple testing. Separation of disease populations based on the presence of antibodies and clinical signs was investigated by principal-components analysis, which was performed by using thr// R's prcomp function with standard parameters.

Results

A 16% higher prevalence of anti-Ku p70 was found over anti-Ku p80 antibodies. In 41 (57%) patients, a combination of both was detected. Five (7%) patients, who were CIE and/or LIA anti-Ku positive, were negative for both subsets, as detected with the immunoblot; 31% of the patients had undifferentiated connective tissue disease (UCTD); 29% had systemic sclerosis (SSc); 18% had systemic lupus erythematosus (SLE); 11% had rheumatoid arthritis; 7% had polymyositis; and 3% had Sjögren syndrome.

Conclusions

A significant positive association was found between female patients with anti-Ku p70 and joint/bone features, and a significant negative association was found between female patients with anti-Ku p80 only and joint/bone features (P = 0.05, respectively). By using the first and the third components of the principal-component analysis (PCA) with 29 parameters evaluated, we observed that the anti-Ku-positive population of UCTD patients had overlapping parameters, especially with SLE, as opposed to SSc, which could be helpful in delineating UCTD patients.     

Vasoactive intestinal peptide inhibits TNF-α-induced apoptotic events in acinar cells from nonobese diabetic mice submandibular glands

Introduction

In systemic sclerosis (SSc) little evidence for the effectiveness of anti-inflammatory and immunosuppressive therapy exists. The objective of this study was to determine the extent to which SSc patients are treated with corticosteroids and immunosuppressive agents.

Methods

Data on duration and dosage of corticosteroids and on the type of immunosuppressive agent were analyzed from 1,729 patients who were registered in the German Network for Systemic Scleroderma (DNSS).

Results

A total 41.3% of all registered SSc patients was treated with corticosteroids. Corticosteroid use was reported in 49.1% of patients with diffuse cutaneous SSc and 31.3% of patients with limited cutaneous SSc (P < 0.0001). Among patients with overlap disease characteristics, 63.5% received corticosteroids (P < 0.0001 vs. limited cutaneous SSc). A total 16.1% of the patients received corticosteroids with a daily dose ≥ 15 mg prednisone equivalent. Immunosuppressive therapy was prescribed in 35.8% of patients. Again, among those patients with overlap symptoms, a much higher proportion (64.1%) was treated with immunosuppressive agents, compared with 46.4% of those with diffuse cutaneous SSc sclerosis and 22.2% of those with limited cutaneous SSc (P < 0.0001). The most commonly prescribed drugs were methotrexate (30.5%), cyclophosphamide (22.2%), azathioprine (21.8%) and (hydroxy)chloroquine (7.2%). The use of these compounds varied significantly between medical subspecialties.

Conclusions

Despite limited evidence for the effectiveness of corticosteroids and immunosuppressive agents in SSc, these potentially harmful drugs are frequently prescribed to patients with all forms of SSc. Therefore, this study indicates the need to develop and communicate adequate treatment recommendations.     

Anti-citrullinated fibronectin antibodies in rheumatoid arthritis are associated with human leukocyte antigen-DRB1 shared epitope alleles

Introduction

Fibronectin is one of the most abundant proteins present in the inflamed joint. Here, we characterized the citrullination of fibronectin in the joints of rheumatoid arthritis (RA) patients and studied the prevalence, epitope specificity and human leukocyte antigen (HLA) association of autoantibodies against citrullinated fibronectin in RA.

Methods

Citrullinated residues in fibronectin isolated from RA patient synovial fluid were identified by mass spectrometry. The corresponding citrullinated and non-citrullinated peptides were synthesized and used to analyze the presence of autoantibodies to these peptides in RA sera and sera from other diseases and healthy controls by ELISA. The data were compared with risk factors like shared epitope HLA alleles and smoking, and with clinical features.

Results

Five citrullinated residues were identified in fibronectin from RA synovial fluid. RA sera reacted in a citrulline-dependent manner with two out of four citrullinated fibronectin peptides, one of which contains two adjacent citrulline residues, in contrast to non-RA sera, which were not reactive. The most frequently recognized peptide (FN-Cit_1035,1036, LTVGLTXXGQPRQY, in which × represents citrulline) was primarily targeted by anti-CCP (cyclic citrullinated peptide) 2-positive RA patients. Anti-FN-Cit_1035,1036 autoantibodies were detected in 50% of established anti-CCP2-positive RA patients and in 45% of such patients from a early arthritis clinic. These antibodies appeared to be predominantly of the immunoglobulin G (IgG) isotype and to be associated with HLA shared epitope alleles (odds ratio = 2.11).

Conclusions

Fibronectin in the inflamed synovia of RA patients can be citrullinated at least at five positions. Together with the flanking amino acids, three of these citrullinated residues comprise two epitopes recognized by RA autoantibodies. Anti-citrullinated fibronectin peptide antibodies are associated with HLA shared epitope alleles.     

Leflunomide increases the risk of silent liver fibrosis in patients with rheumatoid arthritis receiving methotrexate

Introduction

Muscle symptoms in systemic sclerosis (SSc) may originate from altered skeletal muscle microcirculation, which can be investigated by means of blood oxygenation level dependent (BOLD) magnetic resonance imaging (MRI).

Methods

After ethics committee approval and written consent, 11 consecutive SSc patients (5 men, mean age 52.6 years, mean SSc disease duration 5.4 years) and 12 healthy volunteers (4 men, mean age 45.1 years) were included. Subjects with peripheral arterial occlusive disease were excluded. BOLD MRI was performed on calf muscles during cuff-induced ischemia and reactive hyperemia, using a 3-T whole-body scanner (Verio, Siemens, Erlangen, Germany) and fat-suppressed single-short multi-echo echo planar imaging (EPI) with four different effective echo times. Muscle BOLD signal time courses were obtained for gastrocnemius and soleus muscles: minimal hemoglobin oxygen saturation (T2*_min) and maximal T2* values (T2*_max), time to T2* peak (TTP), and slopes of oxygen normalization after T2* peaking.

Results

The vast majority of SSc patients lacked skeletal muscle atrophy, weakness or serum creatine kinase elevation. Nevertheless, more intense oxygen desaturation during ischemia was observed in calf muscles of SSc patients (mean T2*_min -15.0%), compared with controls (-9.1%, P = 0.02). SSc patients also had impaired oxygenation during hyperemia (median T2*_max 9.2% vs. 20.1%, respectively, P = 0.007). The slope of muscle oxygen normalization was significantly less steep and prolonged (TTP) in SSc patients (P<0.001 for both). Similar differences were found at a separate analysis of gastrocnemius and soleus muscles, with most pronounced impairment in the gastrocnemius.

Conclusions

BOLD MRI demonstrates a significant impairment of skeletal muscle microcirculation in SSc.     

Prevalence, correlates and clinical usefulness of antibodies to RNA polymerase III in systemic sclerosis: a cross-sectional analysis of data from an Australian cohort

Introduction

The prevalence of antibodies to RNA polymerase III (anti-RNAP) differs among systemic sclerosis (SSc) cohorts worldwide. Previously reported associations of anti-RNAP include diffuse cutaneous disease, tendon friction rubs and renal crisis, with recent reports suggesting a close temporal association between malignancy and SSc disease onset among patients with anti-RNAP.

Methods

Patients with SSc were tested for the presence of anti-RNAP at recruitment into the Australian Scleroderma Cohort Study. We used univariate and multivariable methods to identify and quantify clinical and laboratory correlates of anti-RNAP in SSc. Diagnostic testing procedures were used to determine the usefulness of these antibodies in estimating the likelihood of clinically important outcomes.

Results

There were 451 patients with mean ± standard deviation age and disease duration at recruitment of 58.1 ± 12.4 and 11.6 ± 10.0 years, respectively; 151 (33.5%) patients were recruited within 5 years of diagnosis of SSc. Overall, 69 (15.3%) patients had anti-RNAP. Univariate associations of anti-RNAP were diffuse disease (75.4% vs. 20.9%, P < 0.0001), joint contractures (73.9% vs. 30.1%, P < 0.0001), greater highest-recorded modified Rodnan skin score (20.6 ± 12.4 vs. 10.1 ± 7.9, P < 0.0001), synovitis (31.9% vs. 19.9%, P = 0.03), myositis (2.9% vs. 0.5%, P = 0.05), systemic hypertension (59.4% vs. 39.7%, P = 0.002), renal crisis (24.6% vs. 1.8%, P < 0.0001) and malignancy diagnosed within 5 years of onset of SSc skin disease (13.3% vs. 3.9%, P = 0.01). In multiple regression analysis, after adjustment for other covariates, anti-RNAP were independently associated with renal crisis (odds ratio (OR) 3.8, 95% confidence interval (CI) 1.2 to 11.5, P = 0.02; positive predictive value (PPV) 24.6%, negative predictive value (NPV) 98.2%), diffuse disease (OR 6.4, 95% CI 2.9 to 13.8, P < 0.0001; PPV 75.4%, NPV 20.9%), joint contractures (OR 2.5, 95% CI 1.2 to 5.3, P = 0.02; PPV 73.9%, NPV 69.9%) and malignancy diagnosed within 5 years of onset of SSc skin disease (OR 4.2, 95% CI 1.3 to 13.4, P = 0.01; PPV 13.3%, NPV 96.1%).

Conclusions

Anti-RNAP status is a clinically useful prognostic marker in SSc and enables clinicians to identify patients at high risk of developing renal crisis, synovitis, myositis and joint contractures. Patients with anti-RNAP also have an increased risk of malignancy within a 5-year timeframe before or after onset of SSc skin changes.     

Circulating and synovial antibody profiling of juvenile arthritis patients by nucleic acid programmable protein arrays

Introduction

Juvenile idiopathic arthritis (JIA) is a heterogeneous disease characterized by chronic joint inflammation of unknown cause in children. JIA is an autoimmune disease and small numbers of autoantibodies have been reported in JIA patients. The identification of antibody markers could improve the existing clinical management of patients.

Methods

A pilot study was performed on the application of a high-throughput platform, the nucleic acid programmable protein array (NAPPA), to assess the levels of antibodies present in the systemic circulation and synovial joint of a small cohort of juvenile arthritis patients. Plasma and synovial fluid from 10 JIA patients was screened for antibodies against 768 proteins on NAPPAs.

Results

Quantitative reproducibility of NAPPAs was demonstrated with > 0.95 intra-array and inter-array correlations. A strong correlation was also observed for the levels of antibodies between plasma and synovial fluid across the study cohort (r = 0.96). Differences in the levels of 18 antibodies were revealed between sample types across all patients. Patients were segregated into two clinical subtypes with distinct antibody signatures by unsupervised hierarchical cluster analysis.

Conclusion

The NAPPAs provide a high-throughput quantitatively reproducible platform to screen for disease-specific autoantibodies at the proteome level on a microscope slide. The strong correlation between the circulating antibody levels and those of the inflamed joint represents a novel finding and provides confidence to use plasma for discovery of autoantibodies in JIA, thus circumventing the challenges associated with joint aspiration. We expect that autoantibody profiling of JIA patients on NAPPAs could yield antibody markers that can act as criteria to stratify patients, predict outcomes and understand disease etiology at the molecular level.     

A multiparameter approach to monitor disease activity in collagen-induced arthritis

Introduction

Recent accumulating evidence indicates a crucial involvement of macrophage lineage in the pathogenesis of systemic sclerosis (SSc). To analyze the assembly of the monocyte/macrophage population, we evaluated the expression of CD163 and CD204 and various activated macrophage markers, in the inflammatory cells of the skin and in the peripheral blood mononuclear cells (PBMCs) derived from patients with SSc.

Methods

Skin biopsy specimens from 6 healthy controls and 10 SSc patients (7 limited cutaneous SSc and 3 diffuse cutaneous SSc) were analyzed by immunohistochemistry using monoclonal antibody against CD68 (pan-macrophage marker), CD163 and CD204. Surface and/or intracellular protein expression of CD14 (marker for monocyte lineage), CD163 and CD204 was analysed by flow cytometry in PBMCs from 16 healthy controls and 41 SSc patients (26 limited cutaneous SSc and 15 diffuse cutaneous SSc). Statistical analysis was carried out using Mann-Whitney U test for comparison of means.

Results

In the skin from SSc patients, the number of CD163⁺ cells or CD204⁺ cells between the collagen fibers was significantly larger than that in healthy controls. Flow cytometry showed that the population of CD14⁺ cells was significantly greater in PBMCs from SSc patients than that in healthy controls. Further analysis of CD14⁺ cells in SSc patients revealed higher expression of CD163 and the presence of two unique peaks in the CD204 histogram. Additionally, we found that the CD163⁺ cells belong to CD14^brightCD204⁺ population.

Conclusions

This is the first report indicating CD163⁺ or CD204⁺ activated macrophages may be one of the potential fibrogenic regulators in the SSc skin. Furthermore, this study suggests a portion of PBMCs in SSc patients abnormally differentiates into CD14^brightCD163⁺CD204⁺ subset. The subset specific to SSc may play an important role in the pathogenesis of this disease, as the source of CD163⁺ or CD204⁺ macrophages in the skin.     

Natural autoantibodies reactive with glycosaminoglycans in rheumatoid arthritis

Introduction

Although natural autoantibodies make up the majority of circulating immunoglobulins and are also present in high numbers in therapeutically used intravenous immunoglobulin preparations, they have received little attention and their precise role remains largely unknown. An increasing awareness of the importance of posttranslational autoantigen modifications and glycobiology led us to explore carbohydrate-reactive natural autoantibodies in patients with rheumatoid arthritis. This study examined systematic antibodies reactive to glycosaminoglycans (GAGs), the carbohydrate components of proteoglycans that are released in large amounts from degrading cartilage.

Methods

To measure antibodies reactive to six different types of GAGs, a specialised ELISA was used in which the carbohydrates were covalently linked to the plastic surface through a 2 nm spacer. Sera from rheumatoid arthritis patients (n = 66), umbilical cord serum samples (n = 11) and adult controls (n = 54) were studied. In order to explore cross-reactivity with microbial antigens, bacterial peptidoglycans and fungal polysaccharides were used. Sera and synovial fluid samples were also tested using a GlycoChip carbohydrate array to characterise individual carbohydrate recognition patterns. We followed a multistep statistical screening strategy for screening GAG-reactive antibodies as predictive disease markers.

Results

While anti-GAG antibodies were absent in the umbilical cord sera, they were readily detectable in adult controls and were significantly elevated in patients with rheumatoid arthritis (p < 0.001). Anti-GAG antibodies showed significant cross-reactivity among different types of GAGs. They also reacted with bacterial peptidoglycans and fungal polysaccharides. Interestingly, anti-chondroitin sulphate C IgM antibody levels showed inverse correlation both with the Disease Activity Score (DAS) 28 scores and C-reactive protein (CRP) levels in rheumatoid arthritis.

Conclusion

The highly abundant and cross-reactive, GAG-specific natural autoantibodies in serum may serve as novel disease-state markers in patients with rheumatoid arthritis.     

High prevalence of autoantibodies to RNA helicase A in Mexican patients with systemic lupus erythematosus

Introduction

Autoantibodies to RNA helicase A (RHA) were reported as a new serological marker of systemic lupus erythematosus (SLE) associated with early stage of the disease. Anti-RHA and other autoantibodies in Mexican SLE patients and their correlation with clinical and immunological features were examined.

Methods

Autoantibodies in sera from 62 Mexican SLE patients were tested by immunoprecipitation of ³⁵S-labeled K562 cell extract and enzyme-linked immunosorbent assay (anti-U1RNP/Sm, ribosomal P, β2GPI, and dsDNA). Anti-RHA was screened based on the immunoprecipitation of the 140-kDa protein, the identity of which was verified by Western blot using rabbit anti-RHA serum. Clinical and immunological characteristics of anti-RHA-positive patients were analyzed.

Results

Anti-RHA was detected in 23% (14/62) of patients, a prevalence higher than that of anti-Sm (13%, 8/62). Prevalence and levels of various autoantibodies were not clearly different between anti-RHA (+) vs. (-) cases, although there was a trend of higher levels of anti-RHA antibodies in patients without anti-U1RNP/Sm (P = 0.07). Both anti-RHA and -Sm were common in cases within one year of diagnosis; however, the prevalence and levels of anti-RHA in patients years after diagnosis did not reduce dramatically, unlike a previous report in American patients. This suggests that the high prevalence of anti-RHA in Mexican patients may be due to relatively stable production of anti-RHA.

Conclusions

Anti-RHA was detected at high prevalence in Mexican SLE patients. Detection of anti-RHA in races in which anti-Sm is not common should be clinically useful. Racial difference in the clinical significance of anti-RHA should be clarified in future studies.     

The prognostic value of baseline erosions in undifferentiated arthritis

Introduction

Evidence suggests that citrullinated fibrin(ogen) may be a potential in vivo target of anticitrullinated protein/peptide antibodies (ACPA) in rheumatoid arthritis (RA). We compared the diagnostic yield of three enzyme-linked immunosorbent assay (ELISA) tests by using chimeric fibrin/filaggrin citrullinated synthetic peptides (CFFCP1, CFFCP2, CFFCP3) with a commercial CCP2-based test in RA and analyzed their prognostic values in early RA.

Methods

Samples from 307 blood donors and patients with RA (322), psoriatic arthritis (133), systemic lupus erythematosus (119), and hepatitis C infection (84) were assayed by using CFFCP- and CCP2-based tests. Autoantibodies also were analyzed at baseline and during a 2-year follow-up in 98 early RA patients to determine their prognostic value.

Results

With cutoffs giving 98% specificity for RA versus blood donors, the sensitivity was 72.1% for CFFCP1, 78.0% for CFFCP2, 71.4% for CFFCP3, and 73.9% for CCP2, with positive predictive values greater than 97% in all cases. CFFCP sensitivity in RA increased to 80.4% without losing specificity when positivity was considered as any positive anti-CFFCP status. Specificity of the three CFFCP tests versus other rheumatic populations was high (> 90%) and similar to those for the CCP2. In early RA, CFFCP1 best identified patients with a poor radiographic outcome. Radiographic progression was faster in the small subgroup of CCP2-negative and CFFCP1-positive patients than in those negative for both autoantibodies. CFFCP antibodies decreased after 1 year, but without any correlation with changes in disease activity.

Conclusions

CFFCP-based assays are highly sensitive and specific for RA. Early RA patients with anti-CFFCP1 antibodies, including CCP2-negative patients, show greater radiographic progression.     

Prevalence of comorbidities in systemic sclerosis versus rheumatoid arthritis: a comparative,multicenter, matched-cohort study

Background

Comorbidities are common in chronic systemic connective tissue diseases and are associated with adverse outcomes, increased morbidity and mortality. Although the prevalence of comorbidities has been well-studied in isolated diseases, comparative studies between different autoimmune diseases are limited. In this study, we compared the prevalence of common comorbidities between patients with systemic sclerosis (SSc) and patients with rheumatoid arthritis (RA).

Methods

Between 2016 and 2017, 408 consecutive patients with SSc, aged 59?±?13?years (87% women), were matched 1:1 for age and gender with 408 patients with RA; mean disease duration was 10?±?8 and 9?±?8?years, respectively. Rates of cardiovascular risk factors, coronary artery disease, stroke, chronic obstructive pulmonary disease (COPD), osteoporosis, neoplasms and depression were compared between the two cohorts.

Results

The prevalence of dyslipidemia (18.4% vs 30.1%, p?=?0.001) and diabetes mellitus (5.6% vs 11.8%, p?=?0.007) and body mass index (p?=?0.001) were lower in SSc compared to RA, while there was no difference in arterial hypertension or smoking. While there was a trend for lower prevalence of ischemic stroke in SSc than in RA (1.1% vs 3.2%, p?=?0.085), coronary artery disease was comparable (2.7% vs 3.7%). No differences were found between patients with SSc and patients with RA in the prevalence of COPD (5.2% vs 3.7%), osteoporosis (24% vs 22%) or neoplasms overall (1.1% vs 1.7%); however lung cancer was the most prevalent cancer in SSc (7/17, 41%), whereas hematologic malignancies (7/19, 36%) and breast cancer (7/19, 36%) predominated in RA. Depression was more prevalent in SSc (22% vs 12%, p?=?0.001), especially in diffuse SSc.

Conclusions

Despite the prevalence of dyslipidemia and diabetes mellitus in SSc being almost half that in RA, the cardiovascular comorbidity burden appears to be similar in both. The overall prevalence of neoplasms is no higher in SSc than in RA, but SSc has a more negative impact on quality of life, as clearly, more SSc patients develop depression compared to patients with RA.

     

Levels of adiponectin,a marker for PPAR-gamma activity,correlate with skin fibrosis in systemic sclerosis: potential utility as biomarker?

Introduction

Progressive fibrosis in systemic sclerosis (SSc) is linked to aberrant transforming growth factor beta (TGF-beta) signaling. Peroxisome proliferator-activated receptor gamma (PPAR-gamma) blocks fibrogenic TGF-beta responses in vitro and in vivo. Reduced expression and function of PPAR-gamma in patients with SSc may contribute to progression of fibrosis. Here we evaluated the levels of adiponectin, a sensitive and specific index of PPAR-gamma activity, as a potential fibrogenic biomarker in SSc.

Methods

Adiponectin levels were determined in the sera of 129 patients with SSc and 86 healthy controls, and serial determinations were performed in 27 patients. Levels of adiponectin mRNA in skin biopsies from SSc patients were assessed in an expression profiling microarray dataset. Regulation of adiponectin gene expression in explanted human subcutaneous preadipocytes and fibroblasts was examined by real-time quantitative PCR.

Results

Patients with diffuse cutaneous SSc had reduced serum adiponectin levels. A significant inverse correlation between adiponectin levels and the modified Rodnan skin score was observed. In longitudinal studies changes in serum adiponectin levels were inversely correlated with changes in skin fibrosis. Skin biopsies from a subset of SSc patients showed reduced adiponectin mRNA expression which was inversely correlated with the skin score. An agonist ligand of PPAR-gamma potently induced adiponectin expression in explanted mesenchymal cells in vitro.

Conclusions

Levels of adiponectin, reflecting PPAR-gamma activity, are correlated with skin fibrosis and might have potential utility as a biomarker in SSc.     

Erectile dysfunction is frequent in systemic sclerosis and associated with severe disease: a study of the EULAR Scleroderma Trial and Research group

Introduction

Erectile dysfunction (ED) is common in men with systemic sclerosis (SSc) but the demographics, risk factors and treatment coverage for ED are not well known.

Method

This study was carried out prospectively in the multinational EULAR Scleroderma Trial and Research database by amending the electronic data-entry system with the International Index of Erectile Function-5 and items related to ED risk factors and treatment. Centres participating in this EULAR Scleroderma Trial and Research substudy were asked to recruit patients consecutively.

Results

Of the 130 men studied, only 23 (17.7%) had a normal International Index of Erectile Function-5 score. Thirty-eight per cent of all participants had severe ED (International Index of Erectile Function-5 score ≤ 7). Men with ED were significantly older than subjects without ED (54.8 years vs. 43.3 years, P < 0.001) and more frequently had simultaneous non-SSc-related risk factors such as alcohol consumption. In 82% of SSc patients, the onset of ED was after the manifestation of the first non-Raynaud's symptom (median delay 4.1 years). ED was associated with severe cutaneous, muscular or renal involvement of SSc, elevated pulmonary pressures and restrictive lung disease. ED was treated in only 27.8% of men. The most common treatment was sildenafil, whose efficacy is not established in ED of SSc patients.

Conclusions

Severe ED is a common and early problem in men with SSc. Physicians should address modifiable risk factors actively. More research into the pathophysiology, longitudinal development, treatment and psychosocial impact of ED is needed.