Autoantibodies to filaggrin/deiminated fibrin (AFA) are useful for the diagnosis and prognosis of rheumatoid arthritis, and are probably involved in the pathophysiology of the disease

Combining Calcitonin and Procalcitonin and Rheumatoid Arthritis-Related Biomarkers Improve Diagnostic Outcomes in Early Rheumatoid Arthritis

Objective

To demonstrate whether procalcitonin (PCT) combined with calcitonin (CT) could provide additional diagnostic value to other clinically available rheumatoid arthritis- (RA-) related biomarkers in the early diagnosis of RA.

Method

The blood samples aseptically collected by venipuncture were centrifuged within 1 hour and frozen at -80°C. PCT and CT levels were measured using electrochemiluminescence immunoassay (ECLIA) in 260 subjects (48 patients with early RA, 34 patients with established RA, 37 patients with systemic lupus erythematosus, 30 with osteoarthritis, 31 with gouty arthritis, and 80 healthy participants). Anti-cyclic citrullinated peptide (Anti-CCP) and anti-RA33 antibodies (Anti-RA33) were analyzed by ELISA. RF was detected by transmission immunoturbidimetry. Mann-Whitney U tests and Kruskal-Wallis tests compared differences among groups. Spearman's rank correlation analysis determined the relationship between biomarkers. Receiver-operator characteristic (ROC) curves were generated, and diagnostic performance was assessed by area under the curve (AUC), as well as specificity, sensitivity, likelihood ratios (LR).

Results

Median serum PCT concentrations were significantly higher (p < 0.0001) in patients with early RA (0.065 ng/ml) when compared with healthy controls (0.024 ng/ml), and patients with osteoarthritis (0.025 ng/ml). When compared with gouty arthritis (GA) controls (0.072 ng/ml) and systemic lupus erythematosus (SLE) controls (0.093 ng/ml), median serum PCT concentrations were not significant in patients with early RA (0.065 ng/ml). Median serum CT concentrations were significantly lower (p < 0.0001) in patients with early RA (0.880 pg/ml) compared with healthy controls (3.159 pg/ml), patients with SLE (2.480 pg/ml), and patients with GA (2.550 pg/ml). When compared with osteoarthritis controls (0.586 pg/ml), median serum CT concentrations were not significant in patients with early RA (0.880 pg/ml). ROC curve analysis comparing early RA with healthy controls demonstrated that the AUC of RF, anti-CCP, and anti-RA33 were 0.66, 0.73, and 0.64, respectively; the additions of PCT and CT further improved the diagnostic ability of early RA with the AUC of 0.97, 0.98, and 0.97, respectively (p < 0.01). The sensitivities of RF, anti-CCP, and anti-RA33 for early RA were 33.33%, 44.74%, and 58.33%, respectively, and the additions of PCT and CT showed very high sensitivities of 83.33%, 92.11%, and 87.50%. The high-value groups of PCT moderately correlated with the anti-RA33 levels (r = 0.417, p < 0.05). CT had no significant correlation with disease duration, radiographic progression, or clinical/serological variables, such as ESR levels, CRP levels, RF, anti-CCP, and anti-RA33 levels in early RA.

Conclusions

Serum PCT and CT combined with clinically available RA-related biomarkers could further improve the diagnostic efficiency of early RA.

Epstein-Barr virus and rheumatoid arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases, with a 0.5% worldwide prevalence. The cause of RA remains unknown, however both genetic and environmental factors may contribute to its development. Among these is the Epstein-Barr virus (EBV). Here, we discuss several aspects of the close relationship between EBV and RA. Patients with RA have impaired control of EBV infection. Indeed, they have high titres of antibodies against EBV antigens. Their peripheral blood T lymphocytes are less efficient at controlling the outgrowth of EBV-infected B cells. RA patients have more EBV-infected B cells than normal controls, leading to a 10-fold systemic EBV overload. Post-transplant lymphoproliferative disorder (PTLPD) is a polyclonal EBV-positive B lymphocyte proliferation, which can evolve into an EBV-positive B cell lymphoma. RA patients also have an increased risk of developing EBV-associated lymphoproliferative disorder (LPD). Hence the need to monitor EBV load when treating RA patients with immunosuppressors. EBV, a widespread virus, highly recognized by antibodies but never eliminated, is an ideal candidate to trigger chronic immune complex disease. Anti-EBV antibody responses should be considered as one of the chronic autoantibody responses linked to the development of RA, in the same way as anti-citrullinated protein antibodies.

Effect of nonsurgical periodontal treatment in patients with periodontitis and rheumatoid arthritis: A systematic review

Background

Periodontitis has been regarded as a potential risk factor for rheumatoid arthritis (RA). A systematic review is made to determine whether nonsurgical periodontal treatment in patients with RA offers benefits in terms of the clinical activity and inflammatory markers of the disease.

Material and Methods

A search was made of the Medline-PubMed, Cochrane, Embase and Scopus databases to identify studies on the relationship between the two disease processes, and especially on the effects of nonsurgical treatment in patients of this kind. The search was based on the following keywords: rheumatoid arthritis AND periodontitis (MeSH), rheumatoid arthritis AND periodontal treatment.

Results

Eight articles on the nonsurgical treatment of patients with periodontitis and RA were finally included in the study. All of them evaluated clinical (DAS28) and laboratory test activity (ESR, CRP, IL-6, TNFα) before and after treatment. A clear decrease in DAS28 score and ESR was recorded, while other parameters such as CRP, IL-6 and TNFα showed a non significant tendency to decrease as a result of treatment.

Conclusions

Nonsurgical treatment improved the periodontal condition of patients with periodontitis and RA, with beneficial effects upon the clinical and laboratory test parameters (DAS28 and ESR), while other inflammatory markers showed a marked tendency to decrease. However, all the studies included in the review involved small samples sizes and follow-up periods of no more than 6 months. Larger and particularly longitudinal studies are therefore needed to more firmly establish possible significant relations between the two disease processes.

Key words:Periodontitis, rheumatoid arthritis, periodontal treatment.

Autoantibodies to posttranslational modifications in rheumatoid arthritis

Autoantibodies have been associated with human pathologies for a long time, particularly with autoimmune diseases (AIDs). Rheumatoid factor (RF) is known since the late 1930s to be associated with rheumatoid arthritis (RA). The discovery of anticitrullinated protein antibodies in the last century has changed this and other posttranslational modifications (PTM) relevant to RA have since been described. Such PTM introduce neoepitopes in proteins that can generate novel autoantibody specificities. The recent recognition of these novel specificities in RA provides a unique opportunity to understand human B-cell development in vivo. In this paper, we will review the three of the main classes of PTMs already associated with RA: citrullination, carbamylation, and oxidation. With the advancement of research methodologies it should be expected that other autoantibodies against PTM proteins could be discovered in patients with autoimmune diseases. Many of such autoantibodies may provide significant biomarker potential.

The use of post-translationally modified peptides for detection of biomarkers of immune-mediated diseases

Biomarkers are decision-making tools at the basis of clinical diagnostics and essential for guiding therapeutic treatments. In this context, autoimmune diseases represent a class of disorders that need early diagnosis and steady monitoring. These diseases are usually associated with humoral or cell-mediated immune reactions against one or more of the body's own constituents. Autoantibodies fluctuating in biological fluids can be used as disease biomarkers and they can be, thus, detected by diagnostic immunoassays using native autoantigens. However, it is now accepted that post-translational modifications may affect the immunogenicity of self-protein antigens, triggering an autoimmune response and creating neo-antigens. In this case, post-translationally modified peptides represent a more valuable tool with respect to isolated or recombinant proteins. In fact, synthetic peptides can be specifically modified to mimic neo-antigens and to selectively detect autoantibodies as disease biomarkers. A 'chemical reverse approach' to select synthetic peptides, bearing specific post-translational modifications, able to fishing out autoantibodies from patients' biological fluids, can be successfully applied for the development of specific in vitro diagnostic/prognostic assays of autoimmune diseases. Herein, we report the successful application of this approach to the identification of biomarkers in different autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis and multiple sclerosis.

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.

Ferrocenyl glycopeptides as electrochemical probes to detect autoantibodies in multiple sclerosis patients' sera

Glycopeptide analogues of CSF114(Glc), modified at N-terminus with new ferrocenyl carboxylic acid and a new ferrocenyl-thiphosphino amino acid, were used to implement a new electrochemical biosensor for autoantibody detection in multiple sclerosis. The ferrocenyl moiety of these "electrochemical probes" did not affect autoantibody recognition both in SP-ELISA and in inhibition experiments. By electrochemical monitoring the interactions of the modified peptides Fc-CSF114(Glc) and 4-FcPhP(S)Abu-CSF114(Glc) with the autoantibodies, we demonstrated that autoantibodies could be detected with a sensitivity comparable to ELISA method. The new electrochemical probes can be proposed to characterize autoantibodies as biomarkers of multiple sclerosis by a simple, rapid, and reproducible cyclic voltammetry-based diagnostic methodology.

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.

Deiminated Epstein-Barr virus nuclear antigen 1 is a target of anti–citrullinated protein antibodies in rheumatoid arthritis

OBJECTIVE

To test the hypothesis that deimination of viral sequences containing Arg-Gly repeats could generate epitopes recognized by anti-citrullinated protein antibodies (ACPAs) that are present in rheumatoid arthritis (RA) sera.

METHODS

Multiple antigen peptides derived from Epstein-Barr virus (EBV)-encoded Epstein-Barr nuclear antigen 1 (EBNA-1) were synthesized, substituting the arginines with citrulline, and were used to screen RA sera. Anti-cyclic citrullinated peptide antibodies were purified by affinity chromatography and tested on a panel of in vitro deiminated proteins. Their ability to bind in vivo deiminated proteins was evaluated by immunoprecipitation, using EBV-infected cell lines.

RESULTS

Antibodies specific for a peptide corresponding to the EBNA-1(35-58) sequence containing citrulline in place of arginine (viral citrullinated peptide [VCP]) were detected in 50% of RA sera and in <5% of normal and disease control sera. In addition, affinity-purified anti-VCP antibodies from RA sera reacted with filaggrin-derived citrullinated peptides, with deiminated fibrinogen, and with deiminated recombinant EBNA-1. Moreover, anti-VCP antibodies immunoprecipitated, from the lysate of calcium ionophore-stimulated lymphoblastoid cell lines, an 80-kd band that was reactive with a monoclonal anti-EBNA-1 antibody and with anti-modified citrulline antibodies.

CONCLUSION

These data indicate that ACPAs react with a viral deiminated protein and suggest that EBV infection may play a role in the induction of these RA-specific antibodies.

Diagnostic performances of anti-cyclic citrullinated peptides antibody and antifilaggrin antibody in Korean patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease of unknown etiology. We studied the diagnostic performances of anti-cyclic citrullinated peptides antibody (anti-CCP) assay and recombinant anti-citrullinated filaggrin antibody (AFA) assay by enzyme linked immunosorbent assay (ELISA) in patients with RA in Korea. Diagnostic performances of the anti-CCP assay and AFA assay were compared with that of rheumatoid factor (RF) latex fixation test. RF, anti-CCP, and AFA assays were performed in 324 RA patients, 251 control patients, and 286 healthy subjects. The optimal cut off values of each assay were determined at the maximal point of area under the curve by receiver-operator characteristics (ROC) curve. Sensitivity (72.8%) and specificity (92.0%) of anti-CCP were better than those of AFA (70.3%, 70.5%), respectively. The diagnostic performance of RF showed a sensitivity of 80.6% and a specificity of 78.5%. Anti-CCP and AFA showed positivity in 23.8% and 17.3% of seronegative RA patients, respectively. In conclusion, we consider that anti-CCP could be very useful serological assay for the diagnosis of RA, because anti-CCP revealed higher diagnostic specificity than RF and AFA at the optimal cut off values and could be performed by easy, convenient ELISA method.

Autoantigenic posttranslational modifications of proteins: does it apply to rheumatoid arthritis?

There are many posttranslational modifications of proteins of which all are homeostatically important either to carry out a particular structural or functional role or to allow efficient recycling of the amino acid constituents. An important feature of the modified proteins is the acquisition of autoantigenicity. That notion should have been recognized for years with the modifications of immunoglobulin G that constitute new targets for rheumatoid factors. Citrullination or the deimination of arginine residues in proteins creates epitopes that are targeted by rheumatoid autoantibodies with a diagnostic sensitivity and specificity of 40% to 70% and 92% to 99%, respectively. The how, when, and why of the responsible break in tolerance are largely speculative but apoptosis, multiple genetic and environmental influences are likely required. Identifying citrullinated proteins as autoantigens has resulted in new diagnostic and prognostic autoantibody markers for RA and studying the citrullination process and its nature and role in cell biology has provided new insights into its pathogenesis.

Autoantibody systems in rheumatoid arthritis: specificity, sensitivity and diagnostic value

The diagnosis of rheumatoid arthritis (RA) is primarily based on clinical symptoms, so it is often difficult to diagnose RA in very early stages of the disease. A disease-specific autoantibody that could be used as a serological marker would therefore be very useful. Most autoimmune diseases are characterized by a polyclonal B-cell response targeting multiple autoantigens. These immune responses are often not specific for a single disease. In this review, the most important autoantibody/autoantigen systems associated with RA are described and their utility as a diagnostic and prognostic tool, including their specificity, sensitivity and practical application, is discussed. We conclude that, at present, the antibody response directed to citrullinated antigens has the most valuable diagnostic and prognostic potential for RA.