Rheumatoid arthritis associated autoantibodies in patients with synovitis of recent onset

The role of anti-mutated citrullinated vimentin antibodies in the diagnosis of early rheumatoid arthritis

OBJECTIVE

Anti-mutated citrullinated vimentin (MCV) antibodies have been reported as a fairly sensitive serological marker of rheumatoid arthritis (RA). We evaluated the diagnostic value of anti-MCV in a large cohort of Chinese patients with early RA.

METHODS

One hundred seventy patients with early RA (<1 yr duration), 66 with other rheumatic diseases, 10 with infectious diseases, and 60 healthy individuals were included in our study. Serum anti-MCV and second-generation anti-cyclic citrullinated peptide antibodies (anti-CCP2) were measured by ELISA, and rheumatoid factor (RF) was measured by rate nephelometry. The associated clinical data of patients with early RA were also evaluated. Then disease activity was scored by the formula for Disease Activity Score (DAS)28, and the degree of radiological changes was assessed by Sharp score.

RESULTS

The prevalence of serum anti-MCV in patients with early RA (78.2%, 133/170) was significantly higher than that of other rheumatologic patients and patients with infectious diseases. It was 12% (3/25) in systemic lupus erythematosus, 9.5% (2/21) in primary Sjögren's syndrome, 10% (1/10) in systemic sclerosis, 20% (2/10) in ankylosing spondylitis, 12.5% (1/8) in viral hepatitis type B, and 0% (0/2) in tuberculosis. Anti-MCV was not found in the serum of healthy subjects. The sensitivities of anti-MCV, anti-CCP2, and RF tests for early RA were 78.2%, 61.8%, and 72.4%, respectively, and the specificities were 93.4%, 96.3%, and 80.1%. The combination of anti-MCV and anti-CCP2 positivity showed a very high specificity (97.8%) and positive predictive value (97.1%), but a low sensitivity (58.8%). The sensitivity reached 81.2% when the union of anti-MCV and anti-CCP2 positivities was used as one combined criterion. Statistically, anti-MCV had significant correlation with anti-CCP2 (r=0.587, p=0.01, 2-tailed) and RF (r=0.389, p=0.01, 2-tailed). In addition, it had an interesting correlation with radiological assessment (r=0.349, p=0.05, 2-tailed). The anti-MCV had no significant correlation with other factors, such as erythrocyte sedimentation rate, C-reactive protein, antikeratin antibody, antiperinuclear factor, global visual analog scale score for joint pain, IgA, IgG, IgM, C3, C4, hidden rheumatoid factor for IgA (HRFIgA), HRFIgG, and DAS28.

CONCLUSION

Anti-MCV is a novel diagnostic marker for early RA. It may be more useful if the anti-CCP2 assay is performed concomitantly to diagnose patients with early RA.

Class-switched B cells display response to therapeutic B-cell depletion in rheumatoid arthritis

INTRODUCTION

Reconstitution of peripheral blood (PB) B cells after therapeutic depletion with the chimeric anti-CD20 antibody rituximab (RTX) mimics lymphatic ontogeny. In this situation, the repletion kinetics and migratory properties of distinct developmental B-cell stages and their correlation to disease activity might facilitate our understanding of innate and adaptive B-cell functions in rheumatoid arthritis (RA).

METHODS

Thirty-five 'RTX-naïve' RA patients with active arthritis were treated after failure of tumour necrosis factor blockade in an open-label study with two infusions of 1,000 mg RTX. Prednisone dose was tapered according to clinical improvement from a median of 10 mg at baseline to 5 mg at 9 and 12 months. Conventional disease-modifying antirheumatic drugs were kept stable. Subsets of CD19+ B cells were assessed by flow cytometry according to their IgD and CD27 surface expression. Their absolute number and relative frequency in PB were followed every 3 months and were determined in parallel in synovial tissue (n = 3) or synovial fluid (n = 3) in the case of florid arthritis.

RESULTS

Six of 35 patients fulfilled the European League Against Rheumatism criteria for moderate clinical response, and 19 others for good clinical response. All PB B-cell fractions decreased significantly in number (P < 0.001) after the first infusion. Disease activity developed independently of the total B-cell number. B-cell repopulation was dominated in quantity by CD27-IgD+ 'naïve' B cells. The low number of CD27+IgD- class-switched memory B cells (MemB) in the blood, together with sustained reduction of rheumatoid factor serum concentrations, correlated with good clinical response. Class-switched MemB were found accumulated in flaring joints.

CONCLUSIONS

The present data support the hypothesis that control of adaptive immune processes involving germinal centre-derived, antigen, and T-cell-dependently matured B cells is essential for successful RTX treatment.

Predicting the development of RA in patients with early undifferentiated arthritis

The rapidity with which bone and cartilage damage occurs in patients with rheumatoid arthritis (RA), and the increasing body of evidence for the effectiveness of early intervention in RA, mean that there is a great need for approaches to accurately predict the development of RA in patients with early undifferentiated arthritis. We will review developments in the prediction of outcome on the basis of clinical and laboratory features, including measures of anti-citrullinated protein/peptide antibody status. Although accurate predictions are possible in the majority of patients using recently developed predictive algorithms which utilize clinical and serological variables, there remains a group of patients for whom it is very difficult to predict the development of RA. The utility of new strategies for prediction will be discussed, including recently discovered genetic associations of RA, an assessment of material from the primary site of pathology (the joint), and assessment using the highly sensitive imaging modalities of ultrasound and magnetic resonance imaging.

Anti-cyclic citrullinated peptide antibodies distinguish hepatitis B virus (HBV)-associated arthropathy from concomitant rheumatoid arthritis in patients with chronic HBV infection

OBJECTIVE

To determine whether anti-cyclic citrullinated peptide (anti-CCP) antibodies, which are a highly specific test for rheumatoid arthritis (RA), could differentiate between hepatitis B virus (HBV)-associated arthropathy and concomitant RA in Korean patients with chronic HBV infection.

METHODS

We investigated 240 patients with HBV infection. Anti-CCP antibodies were measured by ELISA and rheumatoid factor (RF) by the latex fixation test. Patient records were reviewed, and a standard form was used to record all demographic, clinical, and laboratory characteristics. Patients were divided into 4 groups according to joint symptoms: asymptomatic, arthralgia, oligoarthritis, and RA. We categorized liver disease into 3 groups: carrier, chronic hepatitis, and cirrhosis.

RESULTS

Anti-CCP antibodies and RF were detected in 11 and 28 of 240 patients, respectively. Anti-CCP antibodies were detected in 9 of 10 RA (90%) and 2 of 230 non-RA patients (0.86%). The positive rate for RF was 90% in RA and 8.3% in non-RA. Eight of 10 RA patients were positive for both RF and anti-CCP antibodies. RF was detected in 11 patients without joint symptoms, 4 with arthralgia, and 4 with oligoarthritis, whereas anti-CCP antibodies were found in 1 patient without joint symptoms and 1 with oligoarthritis. Specificity of anti-CCP antibody for RA was 99.1%, whereas RF showed 91.7% specificity (p<0.0002). We compared the titers and positive detection rates of anti-CCP antibodies and RF among liver disease subgroups. There was no significant between-subgroup difference.

CONCLUSION

Measurement of anti-CCP antibodies is better than RF detection to discriminate HBV-associated arthropathy from concomitant RA in patients with chronic HBV infection.

Anti-cyclic citrullinated peptide antibodies in patients with juvenile idiopathic arthritis

The objectives were to determine the prevalence and clinical significance of anti-cyclic citrullinated peptide (anti-CCP) antibodies in patients with juvenile idiopathic arthritis (JIA). Anti-CCP antibodies were checked by ELISA in 68 children with JIA, 38 males and 30 females with mean age of 10.6 (+/-4.02) years and disease duration of 3.7 (+/-1.8) years. Thirty-eight (56%) patients had polyarticular disease, 20 (29%) patients had oligoarticular disease and 10 (15%) patients had systemic onset disease. All patients had their antinuclear antibodies (ANA), rheumatoid factor (RF) and ESR checked and x-rays performed to look for erosions. Results were compared to those of 20 healthy children, 14 children with juvenile systemic lupus erythematosus (JSLE) and 30 adults with rheumatoid arthritis (RA). Anti-CCP antibodies were positive in 14/68 (20.6%) patients with JIA, all had polyarticular-onset disease. All patients with positive anti-CCP antibodies had RF-positive polyarthritis. Anti-CCP antibodies were negative in all patients with oligoarticular-onset and systemic-onset disease including 2 patients with extended oligoarthritis. Anti-CCP antibodies were negative in healthy and JSLE controls but were positive in 20/30 (66.5%) adults with RA. Anti-CCP antibodies correlated significantly with joint erosions in patients with JIA (p = 0.004) but no significant relation was found between anti-CCP antibodies and ANA positivity or raised ESR. These data confirm that anti-CCP antibodies are less prevalent in JIA than adult RA but are detectable in a significant proportion of RF-positive patients with polyarticular-onset JIA. The current study showed significant relation between anti-CCP positivity and erosive joint disease in JIA.

[New autoanti-bodies in rheumatoid arthritis: anti-citrullinated protein or peptide autoanti-bodies and the others]

New treatment strategies require that rheumatoid arthritis (RA) be diagnosed as early as possible. New diagnostic markers were required, because rheumatoid factors (RF), until now criteria for classification of RA, are not sufficiently specific and sometimes appear late, thereby limiting their diagnostic usefulness. The objective of this review is to describe the current state of knowledge and more particularly to analyze the interest of new RA autoanti-bodies, called anti-peptide or anti-citrullinated protein anti-bodies (ACPA). Other autoanti-bodies have been described, including anti-Sa, anti-alpha enolase, and anti-calpastatin autoanti-bodies. Nonetheless, their diagnostic value remains limited compared to ACPA. Accordingly, in daily practice today, the only autoanti-bodies that must be tested for to diagnose RA are the ACPAs and RFs. The discovery of ACPA (initially called anti-keratin and anti-perinuclear anti-bodies) was a major step forward for the laboratory diagnosis of RA. The tests most often used routinely areenzyme-linked immunosorbent assays(ELISA) with cyclic citrullinated peptides, whence the name anti-CCP autoanti-bodies. Accordingly, the two terms ACPA and anti-CCP can both be used. The diagnostic value, in particular their specificity, is on the order of 95%, regardless of the method of identification. These markers are very useful and are often present earlier than RF. These ACPA also have prognostic value because they are associated with more aggressive forms of RA. On the other hand, their value over time, in particular, their fluctuation as a function of treatment, is more controversial. In practice, it is recommended to test for both RF and ACPA in a diagnostic work-up for early RA. During follow-up, the value of testing for these autoanti-bodies has not been demonstrated, but additional studies are still necessary with the anti-CCP autoanti-bodies and the new anti-citrullinated protein autoanti-bodies.

Diagnostic performance and predictive value of rheumatoid factor, anti-cyclic-citrullinated peptide antibodies and HLA-DRB1 locus genes in rheumatoid arthritis

BACKGROUND

We evaluated the significance of the genes, defined as DRB1*04 or DRB1*01, in rheumatoid arthritis (RA) patients. We focused on the role of genetic and serologic markers to predict disease activity and destructive process of joints.

METHODS

Sixty patients with RA were examined. Radiographic changes were evaluated by (Larsen score) and disease activity was measured by disease activity score 28 (DAS28). The markers analyzed were: erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), anti-cyclic citrullinated peptides (anti-CCP2) and HLA-DRB1 alleles typed by PCR.

RESULTS

In this study, anti-CCP antibodies, CRP, RF and AKA were detected in 83.3%, 56.7%, 71.7% and 52% of patients respectively. HLA-DRB1*01 was found in 45% of patients and 35% of them had one or two HLA-DRB1*04 alleles. According to DRB1*04 subtypes, (DRB1* 0405) was present in of 80% them. For prediction of grade of activity, the independent predictors were anti-CCP (OR 19.6), and DRB1*04 positive allele (OR 5.1). The combination of DRB1*04 + anti-CCP antibodies gave increase in the specificity and positive predictive value to 92% and 90 respectively. As regards to the prediction of radiological joint damage, the independent predictors were HLA-DRB1*04, HLA-DRB1*01, RF, and CRP > 18 (OR 5.5, 4.5, 2.5, 2.0 respectively).

CONCLUSION

Our findings suggest that anti-CCP2 is superior to RF for the detection of RA and provided predictive information on joint destruction and disease activity. The presence of RA associated antibodies (ACCP or RF) and/or the SE genes are indicative for a poorer radiological outcome and higher grade of activity.

Rheumatoid arthritis diagnosis with antimutated citrullinated vimentin ELISA by Orgentec Diagnostika

BACKGROUND

There is a need for highly sensitive and specific laboratory tests for the early diagnosis of rheumatoid arthritis (RA). Anticitrullinated protein/peptide antibodies are produced in the sera of RA patients.

OBJECTIVE

To assess and discuss the diagnostic value of Orgentec antimutated citrullinated vimentin (anti-MCV) ELISA and to compare this diagnostic to commercially available anticyclic citrullinated peptide (anti-CCP) tests.

METHODS

The evaluation is based on our recently published study on the comparison of anti-MCV and anti-CCP2 tests, as well as on published studies.

RESULTS/CONCLUSION

In established RA, the anti-MCV ELISA exerts a specificity comparable with anti-CCP2. Numerous recent studies suggest that anti-MCV may have higher sensitivity, however there are also some publications stating the opposite. In early RA, anti-MCV may be a better predictor of disease activity and radiological progression than anti-CCP tests.

Association of autoimmunity to peptidyl arginine deiminase type 4 with genotype and disease severity in rheumatoid arthritis

OBJECTIVE

Protein citrullination is an important posttranslational modification recognized by rheumatoid arthritis (RA)-specific autoantibodies. One of the citrullinating enzymes, peptidyl arginine deiminase type 4 (PAD-4), is genetically associated with development of RA in some populations, although the mechanism(s) mediating this effect are not yet clear. There have been descriptions of anti-PAD-4 autoantibodies in different rheumatic diseases. This study was undertaken to investigate whether anti-PAD-4 antibodies are specific to RA, are associated with disease phenotype or severity, and whether PAD-4 polymorphisms influence the anti-PAD-4 autoantibody response.

METHODS

Sera from patients with established RA, patients with other rheumatic diseases, and healthy adults were assayed for anti-PAD-4 autoantibodies by immunoprecipitation of in vitro-translated PAD-4. The epitope(s) recognized by PAD-4 autoantibodies were mapped using various PAD-4 truncations. PAD-4 genotyping was performed on RA patients with the TaqMan assay. Joint erosions were scored from hand and foot radiographs using the Sharp/van der Heijde method.

RESULTS

PAD-4 autoantibodies were found in 36-42% of RA patients, and were very infrequent in controls. Recognition by anti-PAD-4 autoantibodies required the 119 N-terminal amino acids, which encompass the 3 nonsynonymous polymorphisms associated with disease susceptibility. Strikingly, the anti-PAD-4 immune response was associated with the RA susceptibility haplotype of PADI4. Anti-PAD-4 antibodies were associated with more severe joint destruction in RA.

CONCLUSION

Our findings indicate that anti-PAD-4 antibodies are specific markers of RA, independently associated with more severe disease, suggesting that an anti-PAD-4 immune response may be involved in pathways of joint damage in this disease. Polymorphisms in the PADI4 gene influence the immune response to the PAD-4 protein, potentially contributing to disease propagation.

Value of anti-mutated citrullinated vimentin antibodies in diagnosing rheumatoid arthritis

We assessed the diagnostic value of anti-mutated citrullinated vimentin antibodies (anti-MCV) and compared it with those of anti-cyclic citrullinated peptide antibodies (anti-CCP), IgA (ARF), IgM (MRF) and IgG (GRF) rheumatoid factors for rheumatoid arthritis (RA). Serum samples of 170 RA patients, with early and established RA, and 309 controls were tested for anti-MCV, anti-CCP, ARF, MRF and GRF using commercially available ELISA kits. Cut off of different tests was determined with ROC curves. The sensitivity and the specificity of anti-MCV were 74.1 and 79%, respectively. Sixty-five of 309 (21%) controls were anti-MCV positive. Sensitivity and specificity of anti-CCP were 72.4 and 96.1%, respectively. Only 12 of 309 (3.9%) controls were anti-CCP positive. Sensitivity of ARF, MRF and GRF were 64.1, 65.9 and 68.2%, respectively. Their specificity was 79.6, 74.4 and 68.9%, respectively. No significant association was observed between the antibodies tested and extrarticular manifestations. Anti-MCV shows comparable sensitivity but lower specificity than that of anti-CCP. They do not appear to be very useful in the diagnosis of RA.

Arthritis induced by posttranslationally modified (citrullinated) fibrinogen in DR4-IE transgenic mice

Rheumatoid arthritis (RA) is a common autoimmune disease that afflicts the synovium of diarthrodial joints. The pathogenic mechanisms inciting this disease are not fully characterized, but may involve the loss of tolerance to posttranslationally modified (citrullinated) antigens. We have demonstrated that this modification leads to a selective increase in antigenic peptide affinity for major histocompatibility complex (MHC) class II molecules that carry the RA-associated shared epitope, such as HLA-DRB1*0401 (DR4). We describe the induction of arthritis in DR4-IE transgenic (tg) mice with citrullinated fibrinogen, a protein commonly found in inflamed synovial tissue and a frequent target of autoantibodies in RA patients. The disease induced in these mice was characterized by synovial hyperplasia followed by ankylosis, but lacked a conspicuous polymorphonuclear cell infiltrate. Immunological analysis of these mice through T cell epitope scanning and antibody microarray analysis identified a unique profile of citrulline-specific reactivity that was not found in DR4-IE tg mice immunized with unmodified fibrinogen or in wild-type C57BL/6 mice immunized with citrullinated fibrinogen, two conditions where arthritis was not observed. These observations directly implicate citrullinated fibrinogen as arthritogenic in the context of RA-associated MHC class II molecules.

Antibodies against citrullinated vimentin in rheumatoid arthritis: higher sensitivity and extended prognostic value concerning future radiographic progression as compared with antibodies against cyclic citrullinated peptides

OBJECTIVE

The Sa autoantigen can be found in inflamed synovium of patients with rheumatoid arthritis (RA), and at least part of the humoral RA-specific anti-Sa response is directed against citrullinated vimentin. This study was undertaken to evaluate the sensitivity, specificity, and prognostic value of determination of levels of antibodies against modified citrullinated vimentin (anti-MCV) as compared with antibodies against cyclic citrullinated peptides (anti-CCP) in an inception cohort of patients with early RA.

METHODS

Clinical data, radiographs, and measurements of levels of anti-MCV and anti-CCP antibodies were obtained in 273 patients with early RA at baseline, after 3 months, and after 1, 2, 3, and 5 years. Autoantibodies were also analyzed in 100 healthy controls.

RESULTS

Of the 273 patients, 193 (70.7%) were anti-MCV positive and 158 (57.9%) were anti-CCP positive at the time of diagnosis, with nearly equal specificities (95% and 96%, respectively). Forty (14.7%) were anti-MCV positive only, and 5 (1.8%) were anti-CCP positive only. Anti-MCV-positive and anti-MCV-negative patients had similar disease activity at baseline, but presence of anti-MCV was predictive of subsequent high disease activity and continued radiographic progression. Changes in anti-MCV level showed stronger correlation with changes in clinical parameters than did changes in anti-CCP level. The subgroup of patients who were anti-MCV positive and anti-CCP negative showed a higher rate of radiographic destruction than did patients who were negative for both anti-MCV and anti-CCP.

CONCLUSION

These findings show that when patients with early RA are compared with healthy controls, analysis of anti-MCV yields greater sensitivity and unchanged specificity as compared with analysis of anti-CCP. Anti-MCV also appears to perform better than anti-CCP in identifying poor radiographic prognosis in patients with early RA.

Anti-citrullinated protein/peptide antibodies (ACPA) in rheumatoid arthritis: specificity and relation with rheumatoid factor

Anti-citrullinated protein/peptide antibodies (ACPA) are highly specific and sensitive markers for rheumatoid arthritis (RA). For instance, for the anti-CCP2 assay, sensitivities ranging from 55% to 80% and specificities ranging from 90% to 98% have been reported. Despite their high specificity, recent reports have suggested that ACPA may be found in some patients with other rheumatic autoimmune diseases, including psoriatic arthritis, systemic lupus erythematosus and Sjögren's syndrome. Also, the differences between the classical rheumatoid factor (RF) and ACPA, as well as the complementarity between both tests have recently been demonstrated more clearly. Indeed, both antibody systems have a different association with specific RA features like extra-articular manifestations, a different association with the HLA shared epitope and, behave differently following anti-TNF therapy.

Antibodies to mutated citrullinated vimentin and disease activity score in early arthritis: a cohort study

INTRODUCTION

The aim of our study was to investigate the association between arthritic disease activity and antibodies to mutated citrullinated vimentin (anti-MCV), because such a relation has been suggested.

METHODS

Anti-MCV levels were measured in 162 patients with early arthritis (123 with rheumatoid arthritis and 39 with undifferentiated arthritis) at baseline and at 1 and 2 years of follow up. Disease activity was measured using the disease activity score (Disease Activity Score based on 28 joints [DAS28]) and serum C-reactive protein. General estimation equation analysis was used to assess the relation between anti-MCV levels and DAS28 over time.

RESULTS

Both, anti-MCV levels and DAS28 exhibited a significant decrease during the first and second year. However, the association between anti-MCV levels and DAS28, adjusted for dependency on sequential measurements within one individual, was very low (beta = 0.00075). In a population of patients with rheumatoid arthritis or undifferentiated arthritis, anti-MCV had a specificity of 92.3% and a sensitivity of 59.3% when using the recommended cut-off of 20 U/ml. Specificity and sensitivity of antibodies against second-generation cyclic citrullinated peptide, using the recommended cut-off value of 25 U/ml, were 92.1% and 55.3%, respectively. Anti-MCV-positive early arthritis patients had significantly higher Sharp-van der Heijde score, erythrocyte sedimentation rate and C-reactive protein levels than did anti-MCV-negative patients at all time points (P < 0.005), but DAS28 was higher in anti-MCV-positive patients at 2 years of follow up only (P < 0.05).

CONCLUSION

Because the correlation between anti-MCV levels and parameters of disease activity was very low, we conclude that it is not useful to monitor disease activity with anti-MCV levels.

Peptide-coated nanotube-based biosensor for the detection of disease-specific autoantibodies in human serum

We demonstrate a label-free peptide-coated carbon nanotube-based immunosensor for the direct assay of human serum. A rheumatoid arthritis (RA)-specific (cyclic citrulline-containing) peptide, was immobilized to functionalized single-walled carbon nanotubes deposited on a quartz crystal microbalance (QCM) sensing crystal. Serum from RA patients was used to probe these nanotube-based sensors, and antibody binding was detected by QCM sensing. Specific antibody binding was also determined by comparing the assay of two serum control groups (normal and diseased sera), and the native unmodified peptide. The sensitivity of the nanotube-based sensor (detection in the femtomol range) was higher than that of the established ELISA and recently described microarray assay systems, detecting 34.4 and 37.5% more RA patients with anti-citrullinated peptide antibodies than those found by ELISA and microarray, respectively. There was also an 18.4 and 19.6% greater chance of a negative test being a true indicator of a person not having RA than by either ELISA or microarray, respectively. The performance of our label-free biosensor enables its application in the direct assay of sera in research and diagnostics.

A new classification of HLA-DRB1 alleles differentiates predisposing and protective alleles for autoantibody production in rheumatoid arthritis

The HLA-DRB1 gene was reported to be associated with anticitrullinated protein/peptide autoantibody (ACPA) production in rheumatoid arthritis (RA) patients. A new classification of HLA-DRB1 alleles, reshaping the shared epitope (SE) hypothesis, was recently found relevant in terms of RA susceptibility and structural severity.

We investigated the relevance of this new classification of HLA-DRB1 SE⁺ alleles in terms of rheumatoid factor (RF) and ACPA production in a sample of French RA patients.

We studied 160 early RA patients included in a prospective longitudinal cohort of French Caucasian patients with recent-onset arthritis. RF, anticyclic citrullinated peptide 2 (anti-CCP2) and antideiminated human fibrinogen autoantibodies (AhFibA) were assessed in all patients at inclusion. The HLA-DRB1 gene was typed by PCR-sequence specific oligonucleotides probes (PCR-SSOP), and SE+ alleles were classified into four groups (S1, S2, S3P, S3D) according to the new classification.

The new classification of HLA-DRB1 SE+ alleles distinguishes predisposing and protective alleles for RF, anti-CCP2 or AhFibA production. The presence of S2 or S3P alleles is associated with both RF, anti-CCP2 or AhFibA positivity, whereas the presence of S3D or S1 alleles appears to be protective for RF, anti-CCP2 or AhFibA positivity.

The new classification of HLA-DRB1 SE⁺ alleles is relevant in terms of autoantibody production in early RA patients by differentiating predisposing and protective alleles for RF or ACPA production.

Citrullination by peptidylarginine deiminase in rheumatoid arthritis

Rheumatoid arthritis (RA) is a complex, multifactorial disease with genetic and immunological aspects. Because RA is an autoimmune condition, dysregulation of the immune system is implied. Many linkage and association studies have also indicated that multiple genetic factors are associated with RA. Although the contribution of each genetic factor is small, the combination of these factors affects RA development. Previous studies have suggested that genetic changes affect the internal immunological environment, which results in autoimmune diseases. More recent genetic studies indicate that the HLA-DRB gene is the predominant cause of RA and that other non-HLA genes are also involved. We reported that peptidylarginine deiminase (gene name abbreviated to PADI, protein name abbreviated to PAD) type 4 is the one of the non-HLA genetic factors involved in RA via citrullination. Antibodies against citrullinated proteins/peptides are highly specific to RA, but the physiological roles of PADI gene, PAD proteins as their products and citrullinated proteins/peptides are obscure. However, levels of anticitrullinated protein antibodies are apparently also increased and were involved in the pathogenesis of autoimmune arthritis in mice with collagen-induced arthritis (CIA). These data suggested that citrullinated protein and anticitrullinated protein antibodies play important roles in the development of RA. This review summarizes the relationship between RA and citrullination, as well as the role of PADI4 genetics.

Increased prevalence of anti-third generation cyclic citrullinated peptide antibodies in patients with rheumatoid arthritis and CREST syndrome

To investigate the prevalence of anti-third generation cyclic citrullinated peptide antibodies (anti-CCP3) in patients with systemic connective tissue diseases, we assembled a training set consisting of 115 patients with rheumatoid arthritis (RA), 52 with Calcinosis, Raynaud's phenomenon, oesophageal dysmotility, sclerodactyly, telangiectasia (CREST) syndrome, 21 with scleroderma, 20 with ankylosing spondylitis, 18 with reactive arthritis, 25 with juvenile rheumatoid arthritis (RA), 51 with osteoarthritis, 26 with mixed connective tissue disease, 23 with primary Sjogren's syndrome, 74 with systemic lupus erythematosus, 49 with Polymyalgia rheumatica, and 39 with polymyositis/dermatomyositis. The commercial enzyme-linked immunosorbent assay (ELISA) was used to detect anti-CCP antibodies, including anti-CCP2 (regular, second generation of CCP antigen) and anti-CCP3 (third generation of CCP antigen) in disease-related specimens and normal controls. These serum samples were also evaluated for anti-centomere antibodies by anti-centromere ELISA kit. The higher frequencies of anti-CCP3 and anti-CCP2 were detected in 75.6 and 70.4% patients with RA, respectively. At the same time, anti-CCP3 (not anti-CCP2) was significantly increased in samples isolated from patients with CREST syndrome. The clinical sensitivity of IgG anti-CCP3 for the patients with CREST syndrome was 29% (15 of 52) and the specificity was 96% (384 of 397), with the exception of the RA group. The anti-centromere antibodies were significantly higher in patients with CREST only. The results of our study suggest that compared to anti-CCP2 assay, the new anti-CCP3 assay can enhance the clinical sensitivity for diagnosis of RA and, as an associate marker combined with anticentromere, can distinguish CREST syndrome from other systemic connective tissue diseases, especially RA. The clinical specificity of anti-CCP3 was lower than anti-CCP2 assay in diagnosis of RA because of the crossreaction to the patients with CREST syndrome.

Antibodies to citrullinated proteins: Pathogenic and diagnostic significance

The recent demonstration of efficacy in the treatment of rheumatoid arthritis with B-cell-depleting therapy, along with the increasing understanding of the role of anticitrullinated protein antibodies (ACPA) have begun to provide new insights into the pathogenesis of this complex disease. This manuscript reviews the current understanding of ACPA with regard to clinical associations and pathogenic mechanisms in preclinical animal models. These data are synthesized into a model of the development of rheumatoid arthritis that refocuses attention on the role of B cells and immune complexes, returning in part to the origins of scientific investigation in this disease, and points to directions of research that are necessary to achieve the full therapeutic, diagnostic, and prognostic potential of the ACPA antigen-antibody system.

Established rheumatoid arthritis: clinical assessments

Clinical assessment of established rheumatoid arthritis (RA) can have several purposes. It can be used to evaluate prognosis, disease course or interventions at both the individual and the group level (i.e. in a clinical trial), over the short or long term. The instruments used for the different purposes are not always the same. For example, information on prognosis is very useful when assessing the risk:benefit ratio of early aggressive pharmacotherapy; however, established prognostic factors are currently of limited use in individual patients with established RA. As, at the individual patient level, disease activity, disability and joint damage have variable courses, the course of the disease should be evaluated regularly both with process (i.e. erythrocyte sedimentation rate, joint counts) and with outcome (i.e. radiological progression, sum of past process) measures. For the evaluation of interventions, 'core sets' of valid measures to assess disease activity, outcome and specific criteria for improvement are used; these can, to some extent, be useful in clinical practice.

Anti-citrulline antibodies in the diagnosis and prognosis of rheumatoid arthritis: evolving concepts

Citrulline is a non-standard amino acid that can be incorporated into proteins only by post-translational modification of arginine by peptidylarginine deiminase (PAD) enzymes during a variety of biologic processes, including inflammation. Rheumatoid arthritis (RA) is an inflammatory autoimmune disease, with a prevalence of 0.3 to 1% worldwide, which leads to progressive joint erosion and substantial disability if not treated early. A reliable and specific test for a marker present early in the disease would be useful to identify RA patients prior to the occurrence of joint damage. A new group of autoantibodies, the anti-cyclic citrullinated peptide antibodies (anti-CCP), can be detected in up to 80% of patients with RA, are highly specific for the disease, and may be of value for both the diagnosis and the prognosis of RA. The fact that these antibodies may appear before the onset of the disease suggests a potential role in primary prevention. Interestingly, they may also play a role in the pathophysiology of this disabling disease. The process of citrullination, its physiologic role, and citrullination-related pathologies, as well as the use of anti-citrullinated protein antibody tests (ACPA) for the early diagnosis and prognosis of RA and their potential role in the pathophysiology of the disease, are discussed.

Comparison of second- and third-generation anti-cyclic citrullinated peptide antibodies assays for detecting rheumatoid arthritis

BACKGROUND

The aims of the present study were to compare the diagnostic and clinical value of seven commercially available assays for second-generation anti-cyclic citrullinated peptide (CCP2) antibodies, anti-keratin antibodies (AKA) and rheumatoid factor (RF) determination in patients with rheumatoid arthritis (RA), and to check the potential advantages of a third-generation anti-CCP (CCP3) antibodies assay.

METHODS

Serum samples from 120 RA patients and from 170 controls were used to determine the sensitivity, the specificity, the positive (PPV) and negative predictive values (NPV) of CCP2 and CCP3 antibodies, AKA and RF assays. The respective performances of these tests were compared using a receiver-operating characteristics (ROC) curves methodology.

RESULTS

We found no significant differences in sensitivity and specificity between the tested anti-CCP assays. The CCP3 antibodies assay we evaluated was not significantly more sensitive than those of the second generation. Compared with RF technique, all anti-CCP assays showed better specificity, but lower sensitivity. In contrast, while of equivalent specificity, they proved to be more sensitive than AKA in the discrimination of RA from other rheumatic diseases.

CONCLUSIONS

Anti-CCP antibodies determination proved to be a powerful diagnostic tool, especially in RA patients with negative AKA or RF. The investigated CCP3 antibodies assay had no better diagnostic performances than the second-generation assays.

A comparison of the frequency of antibodies to cyclic citrullinated peptides using a third generation anti-CCP assay (CCP3) in systemic sclerosis, primary biliary cirrhosis and rheumatoid arthritis

The objective was to investigate the frequency of anti-cyclic citrullinated peptides (CCP) antibodies in systemic sclerosis (SSc) and primary biliary cirrhosis (PBC), utilizing a new "third generation" anti-CCP ELISA (anti-CCP3) kit and a conventional anti-CCP2 assay. Patients with PBC, SSc, RA, and normal controls were included in the study. Serum samples were screened for autoantibodies by indirect immunofluorescence (IIF), antibodies to CCP by a second- and third-generation ELISA, antibodies to "scleroderma" antigens (CENP B, Scl-70, PM/Scl and fibrillarin-Scl-34) by a line immunoassay (LIA), and IgM RF by ELISA. The frequency of anti-CCP2 antibodies in SSc and PBC samples was 14.8% (11/74) and 6.2% (5/80), respectively, and the frequency of anti-CCP3 antibodies in SSc was 13.5% (10/74) and in PBC was 3.7% (3/80). By comparison, in the RA group the frequency of anti-CCP3 and anti-CCP2 antibodies was 79.1% (38/48) and 77% (37/48), respectively. Anti-CCP3 ELISA had a sensitivity, specificity, and positive and negative likelihood ratios (LR) of 79% (95% confidence interval [CI] = 64-89%), 93% (95% CI = 88-96%), 11.8 (95% CI = 6.8-20.3), and 0.22 (95% CI = 0.12-0.38), respectively. By comparison, the anti-CCP2 assay had a sensitivity, specificity, and positive and negative LRs of 77% (95% CI = 62-87), 90% (95% CI = 85-94), 8.3 (95% CI = 5.2-13.2), and 0.25 (95% CI = 0.15-0.42), respectively. In patients with SSc, there was an association of anti-CCP2 antibodies with the presence of arthritis, but there was no association of anti-CCP2 or anti-CCP3 with anti-CENP B, anti-Scl 70, or RF. This study confirmed the high specificity and sensitivity of both anti-CCP assays for the diagnosis of RA. The presence of anti-CCP antibodies in SSc was only correlated with the presence of arthritis.

The Immunology of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is represents the most common chronic inflammatory joint disease and is still a major medical challenge because of unsolved issues related to the etiologic and pathogenetic questions. Intensive research has been conducted over the last years that focused on the inappropriate activation of the immune system: although T cells have long been deemed to play a central role in the origin and propagation of joint inflammation, data accumulated so far have widened this perspective recognizing the contribution of other cells, as well as the major histocompatibility complex class II proteins and a composite set of costimulatory signals responsible for the production of proinflammatory cytokines and other soluble mediators implicated in tissue destruction typical of the disease. This paper will provide an insight into the immune system in RA, dissecting cellular and humoral aspects both in serum and in synovium of patients.

Anti-CCP antibodies have more diagnostic impact than rheumatoid factor (RF) in a population tested for RF

To compare the diagnostic powers of rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) in a population selected for its high statistical relevance, over a 6-month period, an informed consent to test for anti-CCP was obtained from 1,025 consecutive patients for whom RF was ordered at a University laboratory. Within 1 year, a diagnosis was obtained without informing the physician about the anti-CCP result. Extensive statistical analyses were performed. A total of 768 patients satisfied the inclusion criteria, and 132 were classified as having RA, yielding a pre-test probability of RA of 17%. The sensitivities for anti-CCP and RF were 62 and 64% (P = 0.83), and the specificities were 97 and 90% (P < 0.001), respectively. The positive predictive value (PPV) was 79% for anti-CCP and 56% for RF (P < 0.001), whereas the negative predictive value was 92% for both. The likelihood ratio (LR) was 17.9 for anti-CCP and 6.2 for RF (P < 0.005). Forty RA patients were diagnosed with RA of less than 2 years length, and the same significant statistic differences between anti-CCP and RF were observed. Placing the results of both tests together, or using different cutoff points, increased the diagnostic utility of the tests. The anti-CCP test has statistically shown significant higher specificity, PPV, and LR for RA than the RF test in a clinically diverse population. If new criteria are to be devised to help diagnose early RA, anti-CCP should be included because it has a greater diagnostic impact than RF.

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.

Prevalence and clinical significance of antibodies to citrullinated fibrinogen (ACF) in Chinese patients with rheumatoid arthritis

It has been reported that citrullinated fibrin(ogen) deposits in the inflamed joints played an important role in the pathogenesis of rheumatoid arthritis (RA). Although antibodies to citrullinated fibrinogen (ACF) have been detected in the sera of RA patients, the associations between ACF and RA remain unclear. In this study, human fibrinogen was citrullinated by peptidylarginine deiminase in vitro, and the ACF were detected by an enzyme-linked immunosorbent assay in rheumatic patients, including 183 RA, 121 systemic lupus erythematosus, 48 osteoarthritis, and 108 healthy controls. The prevalence of ACF was determined, and the associations between ACF and RA were evaluated. It was shown that the sensitivity and specificity of ACF in RA were 67.21 and 84.84%, respectively. There were significant correlations between ACF and erythrocyte sedimentation rate, anti-cyclic citrullinated peptide antibody, and anti-keratin antibodies (AKA). In radiographic progression, the RA patients with ACF had higher scores than those without ACF according to the Sharp-van der Heijde method. In addition, ACF was often positive in the RA patients who were IgM rheumatoid factor negative or AKA negative or anti-perinuclear factor negative. The results indicate that ACF assay is helpful for the diagnosis of RA.

The immune response to citrullinated proteins in patients with rheumatoid arthritis

This article reviews data concerning the applicability of anti-citrullinated peptide antibodies in the diagnosis, estimation of prognosis, and follow-up of patients with rheumatoid arthritis (RA). The production of anti-citrullinated peptide antibodies is closely associated with the presence of the HLA-DRB1 shared epitope, a known risk factor for development of RA, and the production may be influenced by environmental factors such as tobacco smoking. Patients who harbor this antibody from the early stage of their disease develop more severe erosive disease than patients with RA who lack the antibody. The anti-citrullinated peptide antibody level may be a reflection of disease activity, at least in the early phase of the disease. The antibody can sometimes be found several years before the onset of clinical symptoms of RA, which may represent an open window for preventive measures to be taken.

Enumeration and phenotypical analysis of distinct dendritic cell subsets in psoriatic arthritis and rheumatoid arthritis

Dendritic cells (DCs) comprise heterogeneous subsets of professional antigen-presenting cells, linking innate and adaptive immunity. Analysis of DC subsets has been hampered by a lack of specific DC markers and reliable quantitation assays. We characterised the immunophenotype and functional characteristics of psoriatic arthritis (PsA)-derived and rheumatoid arthritis (RA)-derived myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) to evaluate their potential role in arthritis. Circulating peripheral blood (PB) pDC numbers were significantly reduced in PsA patients (P = 0.0098) and RA patients (P = 0.0194), and mDCs were significantly reduced in RA patients (P = 0.0086) compared with healthy controls. The number of circulating mDCs in RA PB was significantly inversely correlated to C-reactive protein (P = 0.021). The phenotype of both DC subsets in PsA PB and RA PB was immature as compared with healthy controls. Moreover, CD62L expression was significantly decreased on both mDCs (PsA, P = 0.0122; RA, P = 0.0371) and pDCs (PsA, P = 0.0373; RA, P = 0.0367) in PB. Both mDCs and pDCs were present in PsA synovial fluid (SF) and RA SF, with the mDC:pDC ratio significantly exceeding that in matched PB (PsA SF, P = 0.0453; RA SF, P = 0.0082). pDCs isolated from RA SF and PsA SF displayed an immature phenotype comparable with PB pDCs. RA and PsA SF mDCs, however, displayed a more mature phenotype (increased expression of CD80, CD83 and CD86) compared with PB mDCs. Functional analysis revealed that both SF DC subsets matured following toll-like receptor stimulation. pDCs from PB and SF produced interferon alpha and tumour necrosis factor alpha on TLR9 stimulation, but only SF pDCs produced IL-10. Similarly, mDCs from PB and SF produced similar tumour necrosis factor alpha levels to TLR2 agonism, whereas SF mDCs produced more IL-10 than PB controls. Circulating DC subset numbers are reduced in RA PB and PsA PB with reduced CD62L expression. Maturation is incomplete in the inflamed synovial compartment. Immature DCs in SF may contribute to the perpetuation of inflammation via sampling of the inflamed synovial environment, and in situ presentation of arthritogenic antigen.

Post-translational modifications of the major linear epitope 169-190aa of Ro60 kDa autoantigen alter the autoantibody binding

Ro60 kDa is a member of the Ro/LaRNP ribonucleoprotein complex and its major linear B cell epitope, corresponding to the region 169-190aa, has been found to be the initial target of the autoimmune response in patients with systemic lupus erythematosus. This sequence contains one serine and two arginine amino acid residues, which can potentially be modified post-translationally by phosphorylation or citrullination, respectively. The aim of this study was to develop an immunoassay for anti-Ro60 kDa epitope antibody detection and to investigate the changes in the antigenicity of the Ro60 kDa epitope when it is post-translationally modified, by either citrullination or phosphorylation. Peptide analogues corresponding to the unmodified form of the epitope, its phosphorylated form, and a form with both arginine residues citrullinated were synthesized. The peptide coating conditions were investigated and it was found that the use of highly hydrophilic surfaces increase the efficiency of the coating, as well as the sensitivity of the method for anti-peptide antibody detection. All peptides were tested by the optimized enzyme-linked immunosorbent assay (ELISA) against 119 sera from patients with primary Sjögren's syndrome, systemic lupus erythematosus and rheumatoid arthritis with anti-Ro/SSA reactivity, 20 sera from patients with systemic diseases without anti-Ro/SSA immune reactivity, as well as against 65 sera from normal individuals. A large proportion of the tested sera reacted against all three peptide analogues, although with a preference for the unmodified form of the epitope. In conclusion, post-translational modifications of the major Ro60 kDa B cell epitope can alter the autoantibody binding.

Autoantibodies in rheumatoid arthritis: a review

Emerging insights into the importance of B cells in the pathogenesis of rheumatoid arthritis (RA) as highlighted by the efficacy of B cell depletion is one factor that has contributed to the upsurge of interest in the potential role of autoantibodies both as disease markers and with respect to a pathogenic role. Since the initial description of rheumatoid factor (RF), a large number of both disease-specific and non-specific autoantibodies have been described in patients with RA including antibodies to type II collagen (CII), immunoglobulin binding protein (BiP) and antibodies directed at citrullinated peptides (anti-CCP) and other citrullinated proteins such as vimentin (anti-Sa) . Despite some overlap the serological profile of RA does appear to be distinct from other diseases such as SLE . Although the precise mechanisms responsible for the formation of these antibodies have not been well defined their presence must reflect the interaction between T and B cells believed to be relevant to the pathogenesis of RA. The specificity of the association of such factors as anti-CCP and anti-BiP with RA may reflect unique pathogenic events leading to the processing and presentation of the "cryptic self" . Ease of measurement and stability make autoantibodies attractive diagnostic and prognostic markers particularly in early disease when it may be difficult to distinguish self-limiting synovitis from persistent disease . The purpose of this article is to provide an overview of the current state of knowledge of the spectrum of autoantibodies thus far characterised in individuals with rheumatoid arthritis, and discuss their diagnostic, prognostic and pathogenetic relevance.

Treating very early rheumatoid arthritis

Rheumatoid arthritis (RA) is common and leads to joint damage due to persistent synovitis. The persistence of inflammation is maintained by hyperplastic stromal tissue, which drives the accumulation of leukocytes in the synovium. Aggressive treatment after the first 3-4 months of symptoms, with either disease modifying anti-rheumatic drugs or anti-tumor necrosis factor (TNF)-alpha therapy, reduces the rate of disease progression. However, it rarely switches off disease such that remission can be maintained without the continued need for immunosuppressive therapy. There is increasing evidence that the first few months after symptom onset represent a pathologically distinct phase of disease. This very early phase may translate into a therapeutic window of opportunity during which it may be possible to permanently switch off the disease process. The rationale for, and approaches to, treatment within this very early window are discussed.

Rheumatoid factor and antibodies to cyclic citrullinated peptides are associated with severe extra-articular manifestations in rheumatoid arthritis

OBJECTIVE

To study antibodies to cyclic citrullinated peptides (anti-CCP) and rheumatoid factor in patients with active, severe extra-articular rheumatoid arthritis (ExRA) compared with controls without ExRA.

METHODS

35 consecutive patients with severe ExRA manifestations according to predefined criteria were studied. 70 patients with rheumatoid arthritis, but no ExRA manifestations, individually matched for age, sex and disease duration, served as controls. Patients were included when ExRA was diagnosed, before any new treatment was started. Anti-CCPs were detected with ELISA, rheumatoid factor was quantified using nephelometry and anti-nuclear antibodies (ANA) were investigated using indirect immune fluorescence.

RESULTS

Anti-CCPs were detected in 77% of patients with ExRA versus 56% of controls without ExRA (p = 0.03). Anti-CCP levels also tended to be higher in patients with ExRA (p = 0.09). Rheumatoid factor was detected in 94% v 71% of patients and controls, respectively (p = 0.006), and rheumatoid factor levels were higher in patients with ExRA (median interquartile range (IQR) 245 IU/ml (94-604) v 73 IU/ml (not detected-165); p = 0.001). Levels and occurrence of ANA did not differ between patients with ExRA and controls. Patients with ExRA had higher swollen joint counts and C reactive protein levels, but no correlations were found between anti-CCP or rheumatoid factor levels and these measures within the ExRA group.

CONCLUSION

Rheumatoid factor is strongly associated with severe ExRA manifestations in patients with rheumatoid arthritis, and a similar but weaker association exists for anti-CCPs. This suggests a role for rheumatoid factor and anti-CCP in the pathogenesis of ExRA.

Antibodies against cyclic citrullinated peptide are associated with the DRB1 shared epitope and predict joint erosion in rheumatoid arthritis

OBJECTIVE

To evaluate antibodies against cyclic citrullinated peptide (anti-CCP antibodies) for their predictive value for severe joint destruction in rheumatoid arthritis (RA) and to examine their relationship to shared epitope (SE)-positive DRB1 alleles.

METHODS

Concentrations of anti-CCP antibodies were determined in sera from 126 patients with recent onset RA who had been followed prospectively for 6 yr. Progression of joint destruction was evaluated according to Larsen by scoring radiographs from the hand and feet taken at baseline and after 1, 2, 4 and 6 yr of observation. In addition to clinical parameters, the presence of SE-positive DRB1 alleles and of rheumatoid factor IgM and IgA was determined.

RESULTS

Anti-CCP antibodies were found more frequently and in higher concentrations in both DRB1*01-positive and in DRB1*04-positive SE-positive patients compared with SE-negative patients. Severe joint destruction as defined by a Larsen score in the upper third of the study population was predicted by positivity for anti-CCP antibodies, by the presence of SE-positive DRB1*04 alleles and by the presence of erosive disease at initial presentation. Multiple logistic regression analysis revealed that SE-positive DRB1*04 alleles and anti-CCP antibodies exerted a significant influence on the progression of joint destruction.

CONCLUSION

The association of anti-CCP antibodies with DRB1*01 and with SE-positive DRB1*04 alleles implies a functional role for the SE sequence motif. The determination of SE-positive DRB1*04 alleles and of anti-CCP antibody positivity facilitates the prediction of disease course and prognosis at the time of initial presentation.

Diagnosis and prognosis of early rheumatoid arthritis, with special emphasis on laboratory analysis

Diagnosis of rheumatoid arthritis (RA) is mainly based on clinical criteria of symmetric polyarthritis of the hands and feet, with morning stiffness lasting usually more than 1 h. Autoantibodies typical for RA, i.e., rheumatoid factors and anti-cyclic citrullinated peptide, and measurements of inflammation add more specific information, especially for early diagnosis, where clinical presentation may be oligosymptomatic involving only a few joints. These laboratory parameters are also relevant for prognosis of disease persistence, functional impairment and radiological progression.

Predictive value of antibodies to cyclic citrullinated peptide in patients with early arthritis

The objective of this study was to determine the diagnostic value for rheumatoid arthritis (RA) of antibodies to cyclic citrullinated peptides (anti-CCP) in patients with early arthritis and vasculitis. Sixty-four adult patients with early arthritis and disease duration of less than 4 months were clinically diagnosed by an experienced rheumatologist as having RA (n=27), spondyloarthropathy (n=11), and undifferentiated arthritis (n=26). Eighteen patients with vasculitis were also included in the study. The patients with early arthritis were followed up for 9 months. After the follow-up period, five of 26 patients with undifferentiated arthritis were diagnosed as having RA. All serum samples were tested for anti-CCP and IgM rheumatoid factor (IgM-RF). The anti-CCP positivity in RA patients (44.4%) was significantly more frequent than in patients with undifferentiated arthritis (3.8%), spondyloarthropathy (0%), and vasculitis (5.6%) (p=0.001, p<0.01, and p<0.01, respectively). The frequency of IgM-RF positivity was 40.7% in RA, 7.7% in undifferentiated arthritis, 0% in spondyloarthropathy, and 22.2% in vasculitis groups. The respective specificity of anti-CCP and IgM-RF tests for early RA were 97.3 and 94.6%, and the respective sensitivity of them were 44.4 and 40.7%, respectively. The combination of anti-CCP and IgM-RF positivity had a very high specificity and positive predictive value (100%) but a rather low sensitivity (33.3%). When either anti-CCP or IgM-RF positivity combined into one criterion, the sensitivity became high (51.9%) but the specificity decreased to 91.9%. Overall performance of anti-CCP test alone for the early RA was higher than IgM-RF and the combination of anti-CCP and IgM-RF (p<0.05), and was similar to the combination of anti-CCP or IgM-RF. The specificity of positive anti-CCP test for diagnosis of established RA reached up to 100%. In conclusion, the anti-CCP test is a new diagnostic test with extremely high specificity for RA. Anti-CCP antibody testing combined with IgM-RF testing has additional value over IgM-RF testing alone in patients with early arthritis.

Diagnostic and predictive value of anti-cyclic citrullinated protein antibodies in rheumatoid arthritis: a systematic literature review

OBJECTIVE

To evaluate the two generations of anti-cyclic citrullinated protein (CCP) antibodies as a diagnostic marker of rheumatoid arthritis (RA) and as a predictor of future development of RA in healthy subjects and in patients with early undifferentiated arthritis.

METHODS

A systematic analysis of the literature published between 1999 and February 2006 was conducted. Data were collected on the sensitivity and specificity of the two generations of anti-CCP antibodies for diagnosing RA and predicting future development of the disease.

RESULTS

Among 107 studies initially identified, 68 had interpretable data and were analysed. Diagnostic properties were assessed in 58 studies: mean (SD) sensitivity was 53 (10)% (range 41-68) and 68 (15)% (range 39-94) for anti-CCP1 and anti-CCP2, respectively; mean (SD) specificity was 96 (3)% (range 90-99) and 95 (5)% (range 81-100) for anti-CCP1 and anti-CCP2, respectively. Predictive properties were assessed in 14 studies; odds ratio (95% confidence interval) of anti-CCP1 and anti-CCP2 for the future development of RA were 20 (14 to 31) and 25 (18 to 35), respectively, among patients with early undifferentiated arthritis and 64.5 (8.5 to 489) and 28 (8 to 95), respectively, among healthy subjects.

CONCLUSION

Sensitivity of the second generation of anti-CCP is close to that of rheumatoid factor, with a higher specificity, for distinguishing RA from other rheumatic diseases. Moreover, anti-CCP antibodies appear to be highly predictive of the future development of RA in both healthy subjects and patients with undifferentiated arthritis.

Anti-CCP antibodies in rheumatoid arthritis and psoriatic arthritis

Our aim is to assess the prevalence and associated clinical features of anti-CCP (cyclic citrullinated peptide) antibodies for RF (rheumatoid factor)-positive and RF-negative rheumatoid arthritis (RA) and psoriatic arthritis (PsA). In a prospective, cross-sectional, multi-centre study, we determined the titres of anti-CCP antibodies in 208 RA patients (129 RF-positive, 79 RF-negative), 56 PsA patients and 39 healthy controls (HC). Clinical parameters including disease activity (disease activity score 28-DAS28), physical disability (health assessment questionnaire-HAQ), functional capacity (functional class) and radiological erosions were investigated in patients with RA. In PsA patients, clinical and radiological features were determined. Anti-CCP2 antibodies were measured using a second-generation anti-CCP enzyme-linked immunosorbent assay (Euro-Diagnostica, Netherlands). One-hundred four of 129 RF-positive RA (81%), 16 of 79 RF-negative RA (20%), seven of 56 PsA patients (12.5%) and none of the HC had anti-CCP antibodies. RA patients with anti-CCP antibodies had significantly higher disease activity, greater loss of function and more frequent erosive disease than anti-CCP antibody-negative group. In subgroup analysis, anti-CCP antibodies in RF-negative patients were also associated with erosive disease. All PsA patients with anti-CCP antibodies had symmetric arthritis with higher number of swollen joints. The prevalence of anti-CCP antibodies in RF-positive RA patients was significantly higher than in RF-negative RA and PsA patients. Anti-CCP antibodies were also associated with erosive disease in RF-negative RA patients. Both anti-CCP and RF tests were negative in 30% of the patients. Anti-CCP positivity was a frequent finding in PsA and associated with symmetrical polyarthritis.

Human antibodies induce arthritis in mice deficient in the low-affinity inhibitory IgG receptor Fc gamma RIIB

Rheumatoid arthritis (RA) is a complex autoimmune disease with a poorly understood pathogenesis. The disease is associated with polyclonal B cell activation and the production of autoantibodies (autoAbs), but there is a longstanding controversy as to whether such Abs contribute to, or are secondary to, the pathogenesis of RA. To address the potential pathogenicity of human RA–associated Abs, we developed a passive transfer model involving mice deficient in the low-affinity inhibitory Fc receptor, FcγRIIB. We report that plasma or serum from patients with active RA can induce inflammation and histological lesions in FcγRIIB^−/− mice consistent with arthritis, and that this pathogenic activity is caused by the immunoglobulin G–rich fraction. Our results suggest that humoral autoimmunity can contribute directly to autoimmune arthritis, and that FcγRIIB^−/− mice are a promising model to evaluate the arthritogenic potential of human autoAbs.

Antibodies to citrullinated proteins in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease of unknown etiology, characterized by chronic joint inflammation that often leads to joint destruction. Diagnosis of RA is currently based on the revised classification criteria of the American College of Rheumatology (ACR); however, it remains imprecise, especially early in the course of disease. Rheumatoid factor (RF) has been widely used in clinical practice as a useful serological marker for diagnosis of RA. Although RF is the only serological test in the criteria of the ACR, its specificity is limited since RF can be also detected in other rheumatic diseases. Because the current therapeutic strategies in RA employ increasingly aggressive regimens from early stage of the disease, more specific serological markers than RF are desirable. Recently, anti-cyclic citrullinated peptide (anti-CCP) antibodies have attracted attention as a useful marker for the diagnosis of RA with high specificity. In addition to the diagnostic properties, anti-CCP antibodies showed to be a good prognostic marker for joint destructions. In this review, we will explain about the clinical usefulness of anti-CCP antibodies for the daily practice of RA.