Diagnostic utility of anti-cyclic citrullinated peptide and anti-modified citrullinated vimentin antibodies in rheumatoid arthritis

Several autoantibodies found in RA are directed to epitopes in citrullinated proteins. One of them is anti modified citrullinated vimentin (Anti-MCV). We tested the value a newly developed ELISA for the detection of antibodies against a genetically modified citrullinated vimentin (anti-MCV) in comparison with an anti-CCP based ELISA system for the diagnosis of RA. Thirty-five patients with RA (mean age; 42.6 +/- 10.87 years, mean disease duration; 9.37 +/- 3.98 years) were enrolled in this study. Twenty -five ankylosing spondylitis (mean age; 35.88 +/- 6.64 years, mean disease duration; 10.25 +/- 4.61 years), and 19 healthy subjects (mean age; 40.26 +/- 5.11 years) served as controls. Anti-CCP antibodies and Anti-MCV antibodies were measured using ELISA. In all RA patients, mean anti- CCP level was 69.07 +/- 90.43 U/ml and anti-MCV level was 665.77 +/- 1040.19 U/ml. In patients with AS, the mean anti-CCP level was 10.7 +/- 5.22 U/ml and anti-MCV level was 40.54 +/- 20.15 U/ml. In healthy controls, the mean anti-CCP level was 11.11 +/- 7.65 U/ml, anti-MCV level was 23.12 +/- 12.04 U/ml. In patients with active RA, the mean serum anti-CCP level was 100.54 +/- 98.07 U/ml and anti-MCV level was 998.74 +/- 1154.93 U/ml. In patients with inactive RA, the mean serum anti-CCP level was 8.77 +/- 1.55 U/ml and anti-MCV level was 27.59 +/- 23.10 U/ml. According to these results; In patients with RA, the mean serum anti-MCV and anti-CCP levels were significantly high compared to patients with AS and healthy controls (p=0.002, p=0.001, p=0.002, p=0.001 respectively). The mean serum anti-MCV and anti- CCP levels were significantly higher in active patients with RA than in inactive patients with RA patients (p=0.001 and p=0.001 respectively). In inactive patients with RA, the mean serum anti-MCV and anti-CCP levels were similar in patients with AS and patients (p=0.484, p=0.308, p=0.09 and p=0.222 respectively). The mean serum anti-MCV levels were correlated with DAS 28 (r=0.531, p=0.001), VAS score (r=0.332, p=0.01), ESR (r=0.458, p=0.001), serum CRP levels (r=0.568, p=0.01), serum RF levels (r=0.529, p=0.001), swollen joints number (r=0.525, p=0.001) and tender joints number (r=0.638, p=0.001). As a result; measurement of serum anti-MCV levels is useful for diagnosis of RA and combined use of anti-MCV and RF may be more useful prognostic factor than either method alone, RF and anti-CCP.     

Diagnostic value of antibodies against a modified citrullinated vimentin in rheumatoid arthritis

Antibodies directed against citrullinated vimentin are members of the family of autoantibodies reactive with citrullinated proteins and are among the most specific serological markers for the diagnosis of rheumatoid arthritis (RA). This study was performed to test the diagnostic value of a newly developed enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against a genetically modified citrullinated vimentin (anti-MCV) in comparison with a second-generation anti-cyclic citrullinated peptides (anti-CCP2) ELISA test system. Blinded sera from 631 patients (409 consecutive out-patients and 222 randomly selected stored sera) with RA (n = 164) and non-RA (osteoarthritis [n = 120], polymyalgia rheumatica/giant cell arteritis [n = 80], spondyloarthritis [n = 36], and other inflammatory rheumatic or non-inflammatory disease [n = 67]) were tested for the presence of anti-MCV and anti-CCP2 antibodies according to the manufacturers' instructions. The diagnostic performance of the anti-MCV was comparable with the anti-CCP2 assay for the diagnosis of RA according to the calculated area under the curve (0.824; 95% confidence interval (CI) 0.778-0.870 versus 0.818; 95% CI 0.767-0.869) as analysed by receiving operating characteristic curve. When categorised with a cutoff value of 20.0 U/ml (as recommended by the manufacturer), sensitivity and specificity of the anti-MCV ELISA were 69.5% (95% CI 61.9%-76.5%) and 90.8% (86.9%-93.8%), respectively, compared with 70.1% (62.5%-77.0%) and 98.7% (96.7%-99.6%) of the anti-CCP2 assay. Using the cutoff values of 19.0 U/ml and 81.5 U/ml for the anti-MCV test to obtain a sensitivity and specificity identical to the anti-CCP2 assay, showed a reduced specificity (89.8%; 85.8%-92.9%) and sensitivity (53.7%; 45.7%-61.5%), respectively, of the anti-MCV ELISA compared with the anti-CCP2 test. In conclusion, the serum ELISA testing for anti-MCV antibodies as well as the anti-CCP-2 assay perform comparably well in the diagnosis of RA. In the high-specificity range, however, the anti-CCP2 assay appears to be superior to the anti-MCV test.     

Antibodies of IgG,IgA and IgM isotypes against cyclic citrullinated peptide precede the development of rheumatoid arthritis

Introduction  

We and others have previously shown that antibodies against cyclic citrullinated proteins (anti-CCP) precede the development of rheumatoid arthritis (RA) and in a more recent study we reported that individuals who subsequently developed RA had increased concentrations of several cytokines and chemokines years before the onset of symptoms of joint disease. Here we aimed to evaluate the prevalence and predictive values of anti-CCP antibodies of IgG, IgM and IgA isotype in individuals who subsequently developed RA and also to relate these to cytokines and chemokines, smoking, genetic factors and radiographic score.     

Independent associations of anti-cyclic citrullinated peptide antibodies and rheumatoid factor with radiographic severity of rheumatoid arthritis

Several recent publications have established a strong association between anti-cyclic citrullinated peptide antibody (anti-CCP)-positive rheumatoid arthritis (RA) and carriage of shared epitope (SE) alleles. Although anti-CCP have also been associated with more severe RA, the issue of whether this is independent of rheumatoid factor (RF) has not been addressed. To identify associations between RF, anti-CCP, SE status and radiological damage, we studied a large cross-sectional cohort with longstanding RA. Individuals (n = 872) enrolled in the study all fulfilled the American College of Rheumatology criteria for RA, had a minimum disease duration of 3 years, and at least one definite radiographic erosion was present in hands or feet. Radiographs were scored blind at study entry by a single musculoskeletal radiologist using a modified Larsen's score. Anti-CCP and RF levels were determined using enzyme-linked immunosorbent assay, and DRB1 typing was performed using polymerase chain reaction based methodology. Both anti-CCP and RF levels were strongly associated with radiographic severity (P < 0.0001). In subgroups stratified for both anti-CCP and RF status, evidence of independent associations of both antibodies with radiographic outcome was found (P < 0.0001). An association of SE alleles with radiographic severity was present only in RF-negative individuals. Anti-CCP positivity was associated with SE status with evidence of a gene-dose effect, most markedly in RF-negative individuals (P < 0.01). Anti-CCP and RF status are independent severity factors for RA, with SE alleles playing at most a secondary role. Our data support the view that previously described associations between SE and radiological severity, especially in RF-negative patients, may be indirect and due to an association with anti-CCP.     

Environmental risk factors differ between rheumatoid arthritis with and without auto-antibodies against cyclic citrullinated peptides

The aim of this study was to evaluate new and previously hypothesised non-genetic risk factors for serologic subtypes of rheumatoid arthritis (RA) defined by the presence or absence of auto-antibodies to cyclic citrullinated peptides (CCP). In a national case-control study, we included 515 patients recently diagnosed with RA according to the American College of Rheumatology 1987 classification criteria and 769 gender- and age-matched population controls. Telephone interviews provided information about non-genetic exposures, and serum samples for patients were tested for anti-CCP-antibodies. Associations between exposure variables and risk of anti-CCP-positive and anti-CCP-negative RA were evaluated using logistic regression. A series of RA subtype-specific risk factors were identified. Tobacco smoking (odds ratio [OR] = 1.65; 95% confidence interval: 1.03–2.64, for >20 versus 0 pack-years) was selectively associated with risk of anti-CCP-positive RA, whereas alcohol consumption exhibited an inverse dose-response association with this RA subtype (OR = 1.98, 1.22–3.19, for 0 versus >0–5 drinks per week). Furthermore, coffee consumption (OR = 2.18; 1.07–4.42, for >10 versus 0 cups per day), ever use of oral contraceptives (OR = 1.65; 1.06–2.57) and having a first-degree relative with schizophrenia (OR = 4.18; 1.54–11.3) appeared more strongly associated with risk of anti-CCP-positive RA. Obesity was selectively associated with risk of anti-CCP-negative RA, with obese individuals being at more than 3-fold increased risk of this subtype compared with normal-weight individuals (OR = 3.45; 1.73–6.87). Age at menarche was the only examined factor that was significantly associated with both serologic subtypes of RA (p-trends = 0.01); women with menarche at age ≥ 15 years had about twice the risk of either RA subtype compared with women with menarche at age ≤ 12 years. Major differences in risk factor profiles suggest distinct etiologies for anti-CCP-positive and anti-CCP-negative RA.     

Anti-cyclic citrullinated peptide antibodies in rheumatoid arthritis: relation with clinical features, cytokines and HLA-DRB1

The specificity and sensitivity of anti-cyclic citrullinated peptide antibodies (anti-CCP) was examined in Latin-American patients with rheumatoid arthritis (RA). The variables considered included: 1) relation with the activity of disease, 2) extra-articular manifestations (EAM), 3) synthesis of cytokines (IL-4, IL-10, IL-12, TNF-alpha, and IFN-gamma) and IgM and IgA rheumatoid factor (RF), and 4) the association with HLA-DRB1 polymorphism. Seventy-nine RA patients were assessed (69 with established RA, and 10 with recent-onset RA not receiving any treatment), 56 with ankylosing spondylitis (AS), 25 with systemic lupus erythematosus (SLE), 50 with primary Sj?gren's syndrome (pSS), and 10 healthy individuals. Of the 69 patients with established RA, 36 were reexamined 2 years later. The activity of the RA was measured by criteria adopted by the American College of Rheumatology. Anti-CCP2, RF and cytokines levels were determined by ELISA. HLA genotypes were established by first, PCR sequence amplification using sequence-specific primers and then, complete sequencing of the product. Anti-CCP antibodies were observed in 96% of patients with RA during the first evaluation and in 86% at the second evaluation (p = 0.12). No significant change in antibody titre was observed between the two evaluations (131 +/- 58.7 and 130.6 +/- 67.1 IU, respectively). The overall sensitivity and specificity was 94% and 92%, respectively; however, at titres > 60 IU, the values were 84% and 95%, respectively. The anti-CCP likelihood ratio positive test was 12 and the likelihood ratio negative test was 0.06. The positive predictive value was 87%, and the negative predictive value was 96%. Anti-CCP antibodies were observed in 12% of SLE and pSS patients, in 2% of AS patients, and in 10% of healthy controls. In RA patients, these antibodies were not associated with the activity of disease, EAM or HLA-DRB1 alleles; no significant correlation was observed between antibody titre and cytokines level. Although anti-CCP antibodies have potential as a diagnostic tool for RA, they are not useful for monitoring clinical activity or predicting the clinical course of disease. Antibody synthesis is HLA-DRB1 independent and not correlated with Th1/Th2 cytokines.     

Anti-cyclic citrullinated peptide antibodies in patients affected by HCV-related arthritis

Hepatitis C Virus (HCV) infection can induce immunological disorders with different clinical expressions such as arthritis, Sjogren Syndrome and various forms of vasculitis. Retrospectively, the prevalence of anti-Cyclic Citrullinated peptide antibodies (anti-CCP) in a group of patients affected by HCV-related arthritis with positivity for Rheumatoid Factor (RF) and the eventual correlations with RF and/or Anti-Nuclear Antibodies (ANA) and articular involvement were studied. Thirty patients with arthritis were selected from a population of 380 subjects affected by HCV infection. Each patient was evaluated by clinical examination (23 denoted poliarticular and 7 mono-oligoarticular involvement), by X-graphic aspects of joint involvement (8 patients presented joint erosions), by ANA, RF and anti-CCP positivity. Ten of the HCV-related arthritis patients (33.3 percent) presented positivity for anti-CCP, without significant correlation between such parameter and ANA, RF and articular involvement. Anti-CCP resulted positive in 4 out of the 8 patients with joint erosions, and only in 6 out of the 22 patients without joint erosions. Such frequencies analyzed by chi square resulted with no significant differences. Our patients presented an interesting prevalence of the positivity for anti-CCP. These data are cause to consider the specificity recently attributed to this parameter in the diagnosis of rheumatoid arthritis.     

Diagnostic and prognostic value of antibodies against chimeric fibrin/filaggrin citrullinated synthetic peptides in rheumatoid 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.     

Targeting of anti-citrullinated protein/peptide antibodies in rheumatoid arthritis using peptides mimicking endogenously citrullinated fibrinogen antigens

IntroductionWe have previously identified endogenously citrullinated peptides derived from fibrinogen in rheumatoid arthritis (RA) synovial tissues. In this study, we have investigated the auto-antigenicity of four of those citrullinated peptides, and explored their feasibility to target anti-citrullinated protein/peptide antibodies (ACPA).MethodsThe autoantigenic potential of the fibrinogen peptides was investigated by screening 927 serum samples from the Epidemiological Investigation of RA (EIRA) cohort on a peptide microarray based on the ImmunoCAP ISAC® system. In order to assay for ACPA blocking, two independent pools of purified ACPA were incubated with the respective targeting peptide prior to binding to cyclic citrullinated peptide (CCP)2 using the CCPlus® ELISA kit.ResultsTwo peptides derived from the fibrinogen α chain, Arg573Cit (563-583) and Arg591Cit (580-600), referred to as Cit573 and Cit591, and two peptides from the fibrinogen β chain, Arg72Cit (62-81) and Arg74Cit (62-81) (Cit72 and Cit74), displayed 65 %, 15 %, 35 %, and 53 % of immune reactivity among CCP2-positive RA sera, respectively. In CCP2-negative RA sera, a positive reactivity was detected in 5 % (Cit573), 6 % (Cit591), 8 % (Cit72), and 4 % (Cit74). In the competition assay, Cit573 and Cit591 peptides reduced ACPA binding to CCP2 by a maximum of 84 % and 63 % respectively. An additive effect was observed when these peptides were combined. In contrast, Cit74 and Cit72 were less effective. Cyclization of the peptide structure containing Cit573 significantly increased the blocking efficiency.ConclusionsHere we demonstrate extensive autoantibody reactivity against in vivo citrullinated fibrinogen epitopes, and further show the potential use of these peptides for antagonizing ACPA.     

Identification of citrullinated eukaryotic translation initiation factor 4G1 as novel autoantigen in rheumatoid arthritis

Antibodies against citrullinated proteins are highly specific for rheumatoid arthritis. We previously reported that functional variants of the gene encoding peptidylarginine deiminase type 4 were closely associated with RA. The purpose of this study was to investigate the citrullinated autoantigens recognized by serum samples from patients with RA. The human chondrocyte cDNA expression library was citrullinated by PADI4 and was immunoscreened with anti-modified citrulline antibodies and sera from patients with rheumatoid arthritis. One immunoreactive cDNA clone containing a 2480-base pair insert was isolated and sequence analysis revealed that the cDNA included a part of the eukaryotic translation initiation factor 4G1. Immunoreactivity against a recombinant citrullinated eIF4G1 fragment was observed with high specificity in 50.0% of RA patients. The levels of antibodies against citrullinated eIF4G1 were correlated with those of anti-CCP antibodies. Citrullinated eIF4G1 was identified as a candidate citrullinated autoantigen in RA patients. Citrullination of eIF4G1 may thus be involved in the pathogenesis of RA.     

Presence and utility of IgA-class antibodies to cyclic citrullinated peptides in early rheumatoid arthritis: the Swedish TIRA project

Introduction  

The present study was carried out to assess whether IgA-class antibodies against cyclic citrullinated peptides (IgA anti-CCP) in recent-onset rheumatoid arthritis add diagnostic and/or prognostic information to IgG anti-CCP analysis.     

RF、GPI、抗CCP抗体联合检测对类风湿关节炎的诊断意义

目的:研究类风湿因子(rheumatoid factor,RF)、葡萄糖-6-磷酸异构酶(glucose-6-phosphate isomerase,GPI)和抗环瓜氨酸肽(anti-cyclic citrullinated peptide,anti-CCP)抗体联合检测对类风湿关节炎(rheumatoid arthritis,RA)的诊断意义.方法:收集未经治疗的128例RA患者(RA组)、117例其他风湿病人(非RA组)、74例健康人(正常对照组)血清,采用酶联免疫吸附法(ELISA)检测GPI、抗CCP抗体,采用速率散射比浊法检测RF、C反应蛋白(CRP)、补体(C3、C4)、免疫球蛋白(Iga、IgG、IgM),采用魏氏法测红细胞沉降率(血沉,ESR).结果:(1)GPI、抗CCP抗体诊断RA的特异性分别为91.09%、94.14%,与RF(78.53%)比有显著差异(P<0.01),敏感性分别为75.0%、75.8%,与RF(80.47%)比无统计学差异(P>0.05).(2)GPI和RF、抗CCP抗体和RF、GPI和抗CCP抗体两两组合检测,两个指标均为阳性诊断RA的特异性分别为94.24%、95.81%、96.34%,与单独检测RF比有显著差异(P<0.01);两个指标任一阳性诊断RA的敏感性分别为85.16%、85.94%、87.50%,与单独检测RF比无统计学差异(P>0.05),但与单独检测GPI或抗CCP抗体比有统计学差异(P<0.05)计学.(3)三个指标联合检测均为阳性诊断RA的特异性高达98.43%,与单独检测RF、GPI或抗CCP抗体比有统计学差异(P=0.000,P=0.001,P=0.018),任一阳性诊断RA的敏感性为91.41%,与单独检测RF、GPI或抗CCP抗体比有统计学差异(P=0.012,P=0;000,P=0.001).(4)GPI阳性的RA患者关节炎部位数、CRP、ESR水平明显高于GPI阴性RA患者.且差异有统计学意义(P<0.05).结论:GPI、抗CCP抗体诊断RA比RF更具特异性,三者联合检测可显著提高诊断RA的特异性和敏感性.此外,GPI还可作为RA活动性指标.     

Identification of citrullinated alpha-enolase as a candidate autoantigen in rheumatoid arthritis

Antibodies against citrullinated proteins are highly specific for rheumatoid arthritis (RA), but little is understood about their citrullinated target antigens. We have detected a candidate citrullinated protein by immunoblotting lysates of monocytic and granulocytic HL-60 cells treated with peptidylarginine deiminase. In an initial screen of serum samples from four patients with RA and one control, a protein of molecular mass 47 kDa from monocytic HL-60s reacted with sera from the patients, but not with the serum from the control. Only the citrullinated form of the protein was recognised. The antigen was identified by tandem mass spectrometry as alpha-enolase, and the positions of nine citrulline residues in the sequence were determined. Serum samples from 52 patients with RA and 40 healthy controls were tested for presence of antibodies against citrullinated and non-citrullinated alpha-enolase by immunoblotting of the purified antigens. Twenty-four sera from patients with RA (46%) reacted with citrullinated alpha-enolase, of which seven (13%) also recognised the non-citrullinated protein. Six samples from the controls (15%) reacted with both forms. Alpha-enolase was detected in the RA joint, where it co-localised with citrullinated proteins. The presence of antibody together with expression of antigen within the joint implicates citrullinated alpha-enolase as a candidate autoantigen that could drive the chronic inflammatory response in RA.     

Anti-Sa antibodies and antibodies against cyclic citrullinated peptide are not equivalent as predictors of severe outcomes in patients with recent-onset polyarthritis

The prognostic value of two antibodies targeting citrullinated antigens, anti-Sa and anti-cyclic citrullinated peptide (CCP), present at inclusion, was evaluated prospectively in a cohort of 165 consecutive patients with recent-onset or early polyarthritis (EPA) followed for up to 30 months. Patients were treated according to current Good Clinical Practice standards. Predefined outcomes were severe arthritis and persistent arthritis. At inclusion, a median of 3 months after disease onset, 133 (81%) patients fulfilled at least four American College of Rheumatology criteria for rheumatoid arthritis and 30 (18%) had erosive changes on radiographs of hands and feet. Disease-modifying anti-rheumatic drugs were used in close to 80% of the patients at 30 months. Joint damage increased linearly over time, whereas disease activity declined markedly and remained low at each follow-up. Autoantibodies were identified in 76 (46%) patients: rheumatoid factor (RF) in 68 (41%), anti-CCP in 53 (33%), and anti-Sa in 46 (28%). All three antibodies were correlated, but anti-Sa antibodies best predicted severity at 18 and 30 months. RF and anti-CCP performed less well. For both outcomes, anti-Sa alone performed better than any combination of antibodies. The presence of any autoantibody identified about 50 to 60% of the patients with poor outcomes. In multivariate analysis, anti-Sa (odds ratio (OR) 8.83), the presence of erosions at inclusion (OR 3.47) and increasing age (OR 1.06/year) were significantly associated with severity, whereas RF and anti-CCP were not significant predictors. Persistent arthritis was present in up to 84% of patients; autoantibodies were specific but poorly sensitive predictors of this outcome. We conclude that assays for antibodies against citrullinated antigens differ in their ability to predict poorer outcomes in patients with EPA. In our EPA cohort treated in accordance with current standards, detection of anti-Sa but not of RF or anti-CCP antibodies, in combination with clinical and radiological variables present at the first encounter, allowed the identification of a subgroup of EPA patients suffering more rapid and more severe joint damage over 30 months.     

Influence of HLA DRB1 alleles in the susceptibility of rheumatoid arthritis and the regulation of antibodies against citrullinated proteins and rheumatoid factor

Introduction  

The purpose of this study was to investigate the association between HLA-DRB1 alleles with susceptibility to rheumatoid arthritis (RA) and production of antibodies against citrullinated proteins (ACPA) and rheumatoid factor (RF).     

Serial determination of cyclic citrullinated peptide autoantibodies predicted five-year radiological outcomes in a prospective cohort of patients with early rheumatoid arthritis

The objective of this study was to evaluate the potential of serially determined anti-cyclic citrullinated peptide (CCP) antibodies for predicting structural joint damage in patients with early rheumatoid arthritis (RA), compared to a single baseline determination. Ninety-nine RA patients with disease durations of less than one year and no history of disease-modifying antirheumatic drug therapy were followed prospectively for at least five years. Anti-CCP2 concentrations were measured using a second-generation ELISA. Sharp scores as modified by van der Heijde were determined on hand and foot radiographs. Anti-CCP2 antibodies were detected in 55.5% of patients at baseline and 63.6% at any time during the first three years. Presence of anti-CCP2 at any time during the first three years was associated with radiographic damage at baseline (odds ratio (OR), 3.66; 95% confidence interval (95% CI) 0.99–13.54) and with five year progression of the total Sharp score (OR, 3.17; 95% CI, 1.3–7.7), erosion score (OR, 5.3; 95% CI, 1.4–19.2) and joint space narrowing score (OR, 2.8; 95% CI, 1.15–6.8). The presence of anti-CCP2 or IgM RF at baseline did not predict these outcomes. Patients with negative anti-CCP2 tests throughout follow-up had less radiographic progression than patients with increasing anti-CCP2 concentrations; they did not differ from patients with decreasing anti-CCP2 antibody levels. HLADRB1* typing showed that progression of the mean modified Sharp score was not correlated with the presence of the shared epitope alleles. In conclusion, serially determined anti-CCP2 antibodies during the first three years of follow-up performs better than baseline determination for predicting radiographic progression in patients with early RA.     

Associations of antibodies against citrullinated peptides with human leukocyte antigen-shared epitope and smoking prior to the development of rheumatoid arthritis

IntroductionIt has previously been shown that an increased number of antibodies against citrullinated peptides/proteins (ACPA) predate the onset of rheumatoid arthritis (RA). Over time antibody positivity expands, involving more specific responses when approaching the onset of symptoms. We investigated the impact of human leukocyte antigen-shared epitope (HLA-SE) alleles and smoking on the development of ACPA, as well as in combination with ACPA during the state of quiescent autoimmunity (before the onset of symptoms), on the development of RA.MethodsBlood samples donated to the Medical Biobank of Northern Sweden from individuals prior to the onset of symptoms of RA (n = 370) and after onset (n = 203) and from population-based controls (n = 585) were used. Antibodies against 10 citrullinated peptides, fibrinogen (Fibα561-583, α580-600, ß62-81a, ß62-81b, ß36-52), vimentin (Vim2-17, 60-75), filaggrin (CCP-1/Fil307-324), α-enolase (CEP-1/Eno5-21), collagen type II (citC1359-369), and anti-cyclic citrullinated peptide (CCP)2 antibodies were analysed.ResultsHLA-SE-positive individuals were more frequently positive for ACPA compared with HLA-SE-negative individuals prior to the onset of symptoms of RA, particularly for antibodies against CEP-1 and Fibß62-81a (72). Smoking was associated with antibodies against Vim2-17 and citC1359-369. HLA-SE and smoking showed increasing association to the presence of the antibodies closer to disease onset. The highest odds ratio (OR) for development of RA was for the combination of HLA-SE alleles and ACPA positivity, especially for antibodies against Fibß62-81b, CCP-1/Fil307-324, and Fibβ36-52. A gene-environment additive interaction between smoking and HLA-SE alleles for the risk of disease development was found, with the highest OR for individuals positive for antibodies against Fibβ36-52, CEP-1, and Fibα580-600.ConclusionsThe relationships between antibodies against the different ACPA specificities, HLA-SE, and smoking showed a variable pattern in individuals prior to the onset of RA. The combination of smoking and HLA-SE alleles was significantly associated with the development of some of the antibody specificities closer to onset of symptoms, and these associations remained significant at diagnosis. An additive gene-environment interaction was found for several of the antibodies for the development of RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0638-x) contains supplementary material, which is available to authorized users.     

Role of anti-cyclic citrullinated peptide antibodies in discriminating patients with rheumatoid arthritis from patients with chronic hepatitis C infection-associated polyarticular involvement

This study was performed to assess the utility of anti-cyclic citrullinated peptide (anti-CCP) antibodies in distinguishing between patients with rheumatoid arthritis (RA) and patients with polyarticular involvement associated with chronic hepatitis C virus (HCV) infection. Serum anti-CCP antibodies and rheumatoid factor (RF) were evaluated in 30 patients with RA, 8 patients with chronic HCV infection and associated articular involvement and 31 patients with chronic HCV infection without any joint involvement. In addition, we retrospectively analysed sera collected at the time of first visit in 10 patients originally presenting with symmetric polyarthritis and HCV and subsequently developing well-established RA. Anti-CCP antibodies and RF were detected by commercial second-generation anti-CCP2 enzyme-linked immunosorbent assay and immunonephelometry respectively. Anti-CCP antibodies were detected in 23 of 30 (76.6%) patients with RA but not in patients with chronic HCV infection irrespective of the presence of articular involvement. Conversely, RF was detected in 27 of 30 (90%) patients with RA, 3 of 8 (37.5%) patients with HCV-related arthropathy and 3 of 31 (9.7%) patients with HCV infection without joint involvement. Finally, anti-CCP antibodies were retrospectively detected in 6 of 10 (60%) patients with RA and HCV. This indicates that anti-CCP antibodies can be useful in discriminating patients with RA from patients with HCV-associated arthropathy.     

Identification of novel citrullinated autoantigens of synovium in rheumatoid arthritis using a proteomic approach

Recently, autoantibodies to some citrullinated autoantigens have been reported to be specific for rheumatoid arthritis (RA). However, an entire profile of and autoimmunity of the citrullinated proteins have been poorly understood. To understand the profile, we examined citrullinated autoantigens by a proteomic approach and further investigated the significance of citrullination in antigenicity of one of the autoantigens. Specifically, we detected citrullinated autoantigens in synovial tissue of a patient with RA by two-dimensional electrophoresis and Western blotting by using pooled sera from five patients with RA and anti-citrulline antibodies. After identifying the detected autoantigens by mass spectrometry, we investigated the contribution of citrullination to autoantigenicity by using a recombinant protein with or without citrullination on one of the identified novel citrullinated autoantigens. As a result, we found 51 citrullinated protein spots. Thirty (58.8%) of these spots were autoantigenic. We identified 13 out of the 30 detected citrullinated autoantigenic proteins. They contained three fibrinogen derivatives and several novel citrullinated autoantigens (for example, asporin and F-actin capping protein α-1 subunit [CapZα-1]). We further analyzed the contribution of citrullination to autoantigenicity in one of the detected citrullinated autoantigens, CapZα-1. As a result, frequencies of autoantibodies to non-citrullinated CapZα-1 were 36.7% in the RA group tested, 10.7% in the osteoarthritis (OA) group, and 6.5% in healthy donors. On the other hand, those to citrullinated CapZα-1 were 53.3% in the RA group, 7.1% in the OA group, and 6.5% in the healthy donors. This shows that autoantigenicity of citrullinated or non-citrullinated CapZα-1 is relevant to RA. The antibody titers to the citrullinated CapZα-1 were significantly higher than those to the non-citrullinated CapZα-1 in 36.7% of patients; however, the other patients showed almost equal antibody titers to both citrullinated and non-citrullinated CapZα-1. Therefore, the autoantibodies would target citrulline-related and/or citrulline-unrelated epitope(s) of CapZα-1. In conclusion, we report a profile of citrullinated autoantigens for the first time. Even though citrullination is closely related to autoantigenicity, citrullination would not always produce autoantigenicity in RA. Citrullinated and non-citrullinated autoantigens/autoepitopes would have different pathological roles in RA.