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

Crossing epigenetic frontiers: the intersection of novel histone modifications and diseases

Histone post-translational modifications (HPTMs), as one of the core mechanisms of epigenetic regulation, are garnering increasing attention due to their close association with the onset and progression of diseases and their potential as targeted therapeutic agents. Advances in high-throughput molecular tools and the abundance of bioinformatics data have led to the discovery of novel HPTMs which similarly affect gene expression, metabolism, and chromatin structure. Furthermore, a growing body of research has demonstrated that novel histone modifications also play crucial roles in the development and progression of various diseases, including various cancers, cardiovascular diseases, infectious diseases, psychiatric disorders, and reproductive system diseases. This review defines nine novel histone modifications: lactylation, citrullination, crotonylation, succinylation, SUMOylation, propionylation, butyrylation, 2-hydroxyisobutyrylation, and 2-hydroxybutyrylation. It comprehensively introduces the modification processes of these nine novel HPTMs, their roles in transcription, replication, DNA repair and recombination, metabolism, and chromatin structure, as well as their involvement in promoting the occurrence and development of various diseases and their clinical applications as therapeutic targets and potential biomarkers. Moreover, this review provides a detailed overview of novel HPTM inhibitors targeting various targets and their emerging strategies in the treatment of multiple diseases while offering insights into their future development prospects and challenges. Additionally, we briefly introduce novel epigenetic research techniques and their applications in the field of novel HPTM research.

Increased gene expression of CCR6 and RORγt in peripheral blood cells of rheumatoid arthritis patients and their correlation with anti-cyclic citrullinated peptide and disease activity

OBJECTIVES

The significance of T helper 17 (Th17) cells in the pathogenesis of rheumatoid arthritis (RA) has recently been demonstrated in many studies. Retinoic acid receptor-related orphan receptor γt (RORγt) is a transcription factor that is specifically involved in the generation of Th17 cells. Besides, the chemokine receptor CCR6, the receptor for CCL20, is characteristically expressed by these cells. Considering the pivotal roles of Th17 cells in RA pathogenesis, in this study, we assessed the gene expression of CCR6 and RORγt in the peripheral blood leukocytes of new case RA patients. Also, we evaluated their association with anticyclic citrullinated peptide (anti-CCP) antibodies and disease activity.

METHODS

Forty-five new case RA patients and 45 healthy persons have been recruited in this investigation. The gene expression of CCR6 and RORγt was evaluated by quantitative real-time PCR (qRT-PCR), and anti-CCP antibodies plasma levels were measured using the enzyme-linked immunosorbent assay (ELISA) technique. Disease activity was measured according to the disease activity score-28 (DAS-28) formula.

RESULTS

The gene expression of CCR6 and RORγt increased remarkably in new case RA patients compared to healthy controls (p < .05 and p < .01, respectively). Moreover, there was a positive correlation between RORγt gene expression and parameters, including gene expression of CCR6 (p = .001, r = .461), plasma levels of CCL20 (p = .0009, r = .477), ESR (p = .004, r = .419), DAS-28 (p = .006, r = .402), anti-CCP (p = .019, r = .346), and RF (p = .001, r = .451). Also, CCR6 gene expression was positively associated with the DAS-28 (p = .037, r = .310), plasma levels of anti-CCP (p = .037, r = .312), and ESR (p = .029, r = .327).

CONCLUSION

Increased gene expression of CCR6 and RORγt in peripheral blood leukocytes of new case RA patients may contribute to the exacerbation and pathogenesis of RA.

The role of glycolytic metabolic pathways in cardiovascular disease and potential therapeutic approaches

Cardiovascular disease (CVD) is a major threat to human health, accounting for 46% of non-communicable disease deaths. Glycolysis is a conserved and rigorous biological process that breaks down glucose into pyruvate, and its primary function is to provide the body with the energy and intermediate products needed for life activities. The non-glycolytic actions of enzymes associated with the glycolytic pathway have long been found to be associated with the development of CVD, typically exemplified by metabolic remodeling in heart failure, which is a condition in which the heart exhibits a rapid adaptive response to hypoxic and hypoxic conditions, occurring early in the course of heart failure. It is mainly characterized by a decrease in oxidative phosphorylation and a rise in the glycolytic pathway, and the rise in glycolysis is considered a hallmark of metabolic remodeling. In addition to this, the glycolytic metabolic pathway is the main source of energy for cardiomyocytes during ischemia-reperfusion. Not only that, the auxiliary pathways of glycolysis, such as the polyol pathway, hexosamine pathway, and pentose phosphate pathway, are also closely related to CVD. Therefore, targeting glycolysis is very attractive for therapeutic intervention in CVD. However, the relationship between glycolytic pathway and CVD is very complex, and some preclinical studies have confirmed that targeting glycolysis does have a certain degree of efficacy, but its specific role in the development of CVD has yet to be explored. This article aims to summarize the current knowledge regarding the glycolytic pathway and its key enzymes (including hexokinase (HK), phosphoglucose isomerase (PGI), phosphofructokinase-1 (PFK1), aldolase (Aldolase), phosphoglycerate metatase (PGAM), enolase (ENO) pyruvate kinase (PKM) lactate dehydrogenase (LDH)) for their role in cardiovascular diseases (e.g., heart failure, myocardial infarction, atherosclerosis) and possible emerging therapeutic targets.

Geraniol Suppresses Oxidative Stress, Inflammation, and Interstitial Collagenase to Protect against Inflammatory Arthritis

Geraniol (GER) is a plant-derived acyclic isoprenoid monoterpene that has displayed anti-inflammatory effects in numerous in vivo and in vitro models. This study was therefore designed to evaluate the antiarthritic potential of GER in complete Freund's adjuvant (CFA)-induced inflammatory arthritis (IA) model in rats. IA was induced by intraplantar injection of CFA (0.1 mL), and a week after CFA administration, rats were treated with various doses of methotrexate (MTX; 1 mg/kg) or GER (25, 50, and 100 mg/kg). Treatments were given on every alternate day, and animals were sacrificed on the 35th day. Paw volume, histopathological, hematological, radiographic, and qPCR analyses were performed to analyze the severity of the disease. GER significantly reduced paw edema after 35 days of treatment, and these results were comparable to the MTX-treated group. GER-treated animals displayed a perfect joint structure with minimal inflammation and no signs of cartilage or bone damage. Moreover, GER restored red blood cell and hemoglobin levels, normalized erythrocyte sedimentation rate, platelet, and c-reactive protein values, and also attenuated the levels of rheumatoid factor. RT-qPCR analysis demonstrated that GER decreased mRNA expression of pro-inflammatory cytokines like tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta. GER also down-regulated the transcript levels of cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-1, prostaglandin D2 synthase, and interstitial collagenase (MMP-1). Molecular docking of GER with COX-2, TNF-α, and MMP-1 also revealed that the antiarthritic effects of GER could be due to its direct interactions with these mediators. Based on our findings, it is conceivable that the antiarthritic effects of GER could be attributed to downregulation of pro-inflammatory mediators and protease like MMP-1.

Association between dietary inflammatory index scores and the increased disease activity of rheumatoid arthritis: a cross-sectional study

Background

Diet plays an important role in regulating inflammation, which is a hallmark of rheumatoid arthritis (RA). Our aim was to investigate the association between the Dietary Inflammatory Index (DII) scores and RA activity.

Methods

This cross-sectional study was conducted on 184 patients with RA in rheumatology clinic in Kermanshah city, Iran, in 2020. RA was diagnosed according to the criteria of the 2010 American College of Rheumatology/ European League against Rheumatism. The overall inflammatory potential of the diet was extracted from a validated 168-item food frequency questioner (FFQ) using the DII. RA disease activity was assessed using Disease Activity Score 28 (DAS-28) scores. Logistic regression and one-way ANOVA/ ANCOVA were conducted.

Results

Individuals in the highest DII quartile had the significantly higher odds of positive C-reactive protein than those in the lowest quartile of the DII scores (OR 4.5, 95% CI 1.16 – 17.41, P = 0.029). A statistically significant downward linear trend in fat-free mass and weight were observed with increasing the DII quartiles (P = 0.003, P = 0.019, respectively). Patients in the highest DII quartile had higher DAS-28 scores than those in the first quartile (Mean difference: 1.16, 95% CI 0.51 – 1.81, P < 0.001) and second quartile of the DII scores (Mean difference: 1.0, 95% CI 0.34 – 1.65, P < 0.001).

Conclusion

Our results indicated that reducing inflammation through diet might be one of the therapeutic strategies to control and reduce the disease activity in RA patients.

Fluorescence-encoded poly(methyl metharcylate) nanoparticles for a lateral flow assay detecting IgM autoantibodies in rheumatoid arthritis

Rheumatoid arthritis (RA) belongs to the most often occurring autoimmune diseases in the world. For serological diagnosis, IgM auto-antibodies directed against the Fc portion of IgG referred to as rheumatoid factor are used as biomarkers. The autoantibody detection is usually done by ELISA. Such assays are reliable but are not suitable for point-of-care testing in contrast to lateral flow assays. Here, we report the development of a lateral flow assay based on carboxylated fluorescence-encoded poly(methyl methacrylate) nanoparticles. Poly(methyl methacrylate) is a non-toxic plastic with an excellent biocompatibility and high optical transparency which promises especially high sensitive fluorescence detection thereby leading to very sensitive assays. We could detect a positive signal in samples with a nephelometric reading down to 0.4 U/mL. By analyzing 30 sera of patients with a RA diagnosis and 34 sera of healthy test subjects we could confirm positive ELISA results in 72% of all cases and negative ELISA results in 97% of all cases.

A Streamlined Data Analysis Pipeline for the Identification of Sites of Citrullination

Citrullination is an enzyme-catalyzed post-translational modification (PTM) that is essential for a host of biological processes, including gene regulation, programmed cell death, and organ development. While this PTM is required for normal cellular functions, aberrant citrullination is a hallmark of autoimmune disorders as well as cancer. Although aberrant citrullination is linked to human pathology, the exact role of citrullination in disease remains poorly characterized, in part because of the challenges associated with identifying the specific arginine residues that are citrullinated. Tandem mass spectrometry is the most precise method for uncovering sites of citrullination; however, due to the small mass shift (+0.984 Da) that results from citrullination, current database search algorithms commonly misannotate spectra, leading to a high number of false-positive assignments. To address this challenge, we developed an automated workflow to rigorously and rapidly mine proteomic data to unambiguously identify the sites of citrullination from complex peptide mixtures. The crux of this streamlined workflow is the ionFinder software program, which classifies citrullination sites with high confidence on the basis of the presence of diagnostic fragment ions. These diagnostic ions include the neutral loss of isocyanic acid, which is a dissociative event that is unique to citrulline residues. Using the ionFinder program, we have mapped the sites of autocitrullination on purified protein arginine deiminases (PAD1-4) and mapped the global citrullinome in a PAD2-overexpressing cell line. The ionFinder algorithm is a highly versatile, user-friendly, and open-source program that is agnostic to the type of instrument and mode of fragmentation that are used.

Rheumatoid factor positivity in antineutrophil cytoplasmic antibody-associated vasculitis: a distinct clinical entity or innocent bystander?

OBJECTIVE

To investigate the significance of rheumatoid factor (RF) positivity in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) patients.

METHODS

AAV patients were divided into groups as follows: RF (+)/ANCA (+) (n = 94), RF (-)/ANCA (+) (n = 80), RF (+)/ANCA (-) (n = 15), and RF (-)/ANCA (-) (n = 25). Their clinical data, organ involvement patterns, laboratory data, and patient outcomes were assessed. Kaplan-Meier analysis and propensity score matching (PSM) were performed to compare outcomes and analyse differences between the groups.

RESULTS

Of the 214 patients, RF and ANCA positivity was found in 109 (50.9%) and 174 (81.3%) patients, respectively. RF (+)/ANCA (+) patients more frequently presented with general manifestations (58.5%) than the other groups. Additionally, compared with those of RF (-)/ANCA (+) group, RF (+)/ANCA (+) patients were older, had higher white blood cell, neutrophil, platelet counts, and acute phase reactants; however, creatinine and albumin levels were lower. The end-stage kidney disease-free survival rate was significantly higher in the RF (+)/ANCA (+) group (p= 0.013), while the proportion of renal involvement was comparable to the RF (-)/ANCA (+) group. PSM showed no difference in patient outcomes between the two groups after adjustment.

CONCLUSION

RF positivity was associated with a distinct phenotype in AAV patients. In particular, difference was observed in clinical features and outcomes between RF (+)/ANCA (+) and RF (-)/ANCA (+) groups, although the direct prognostic implication of RF was not evident.

Histone citrullination: a new target for tumors

As the main protein components of chromatin, histones play central roles in gene regulation as spools of winding DNA. Histones are subject to various modifications, including phosphorylation, acetylation, glycosylation, methylation, ubiquitination and citrullination, which affect gene transcription. Histone citrullination, a posttranscriptional modification catalyzed by peptidyl arginine deiminase (PAD) enzymes, is involved in human carcinogenesis. In this study, we highlighted the functions of histone citrullination in physiological regulation and tumors. Additionally, because histone citrullination involves forming neutrophil extracellular traps (NETs), the relationship between NETs and tumors was illustrated. Finally, the clinical application of histone citrullination and PAD inhibitors was discussed.

Auto-antibodies to post-translationally modified proteins in osteoarthritis

OBJECTIVE

Autoantibodies (AutoAbs) have been observed in osteoarthritis (OA) with broad antigenicity, although their prevalence and role remain unclear. Post-translational modification (PTMs) of proteins (oxidation, carbamylation, citrullination) is associated with synovitis and can lead to AutoAb development. Given the prevalence of synovitis, we explored whether AutoAbs to PTM-antigens are common in OA compared with rheumatoid arthritis (RA).

METHODS

Serum (n = 895) was obtained from healthy controls, OA and RA patients; and arthritic synovial fluid (SF, n = 290). ELISAs were used to quantify anti-citrullinated peptide (ACPA), anti-carbamylated protein (anti-CarP), anti-oxidized collagen (anti-ROS-CI/CII) antibodies.

RESULTS

In sera, positivity for PTM-antigens AutoAbs was observed at a lower frequency in OA with 64.1% (95%CI: 57.2-70.1%) more ACPA+ and 29.8% (21.0-37.3%) more anti-CarP + patients in RA (both P < 0.0001). Levels of ACPA, anti-CarP were also lower in OA (P < 0.0001). Anti-ROS-CII positivity was lower in OA compared to RA (16.6%, 4.8-28.6%) less frequent, P = 0.033) but not anti-native-CII. There was no impact of age/gender on AutoAbs associations with diseases either looking at positivity or levels. In SF, OA patients were often ACPA+ (45.9%) although less frequently than in RA (P = 0.004). Anti-CarP were rarely observed (<5% all samples). All collagen AutoAbs were more frequent in RA compared to OA (all P < 0.010) but only levels of anti-CII and anti-ROS-CII were significantly higher in they RA (P < 0.050).

CONCLUSION

Although the frequency of AutoAbs for PTM proteins were lower in OA sera compared to RA, a higher proportion of OA SF were positive. The relative retention of AutoAbs in the OA joint requires further investigation.

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.

Preparation and characterization of cyclic citrullinated peptide-immobilized latex beads for measurement of anti-citrillinated protein antibody through latex particle-enhanced turbidimetric immunoassay

The anti-citrillinated protein antibody (ACPA) plays an important role in early diagnosis of rheumatoid arthritis (RA), and is usually detected by using cyclic citrullinated peptide (CCP) as antigen. The ACPA against CCP test is usually performed utilizing enzyme-linked immunosorbent assay (ELISA), but the ELISA is expensive and time-consuming. Here, latex particle-enhanced turbidimetric immunoassay (LTIA) based on CCP-immobilized latex bead was proposed for fast measurements of ACPA of RA patients. CCP-immobilized latex bead was fabricated through three methods, including direct coupling, overall coupling and layer by layer coupling. According to the optimized experiments, layer-by-layer coupling was the best method with advantages of time-saving, simple operation and good repeatability. In addition, a spacer arm of appropriate length between latex beads and CCP could avoid stereoscopic obstacles and make ACPA closer to CCP. The CCP-immobilized latex bead based on layer by layer coupling (CCP-LB-LLC) was used for assembling the homemade kit, which was applied in fast measurements of ACPA through LTIA. The homemade kit possessed a low limit of detection (0.2 U/mL) and an acceptable the batch-to-batch reproducibility. In addition, the homemade kit can be stored at 4 °C for at least one month. When used to detect 20 clinical samples, the results of homemade kit were consistent with commercial ELISA. Furthermore, LTIA based on the homemade kit was simpler and cheaper than ELISA. These results demonstrated that the homemade kit could be useful for diagnosis of RA patients.

Insights of rheumatoid arthritis biomarkers

Rheumatoid arthritis is a chronic, autoimmune connective tissue disease. In addition to joint involvement, extra-articular changes and organ complications also occur in the course of the disease. Untreated disease leads to disability and premature death. Therefore, it is important to recognise and begin treatment early. Based on the presence of rheumatoid factor and antibodies against citrullinated peptides, we can distinguish two forms of the disease: seropositive and seronegative. Research continues to elucidate the mechanisms of the onset of the disease, as well as to uncover factors that induce and influence the activity of the disease. The presence of markers that initially appear and affect the course of the disease can potentially aid in patient treatment. In this article, we have collected biomarkers of rheumatoid arthritis that are well understood as well as those that have been recently described.

Sex effect on the correlation of immunoglobulin G glycosylation with rheumatoid arthritis disease activity

Rheumatoid arthritis (RA) is a chronic autoimmune disease which affects females more than males with a presence of autoantibodies. Immunoglobulin G (IgG) produced by adaptive arm has 2 functional domains, Fc and Fab. The Fc domain binds Fc gamma receptors and C1q proteins of the innate arm. Therefore, the IgG Fc domain serves as a bridge between the innate and adaptive arms and is regulated by an evolutionarily conserved N-glycosylation with variable structures. These glycans are classified as agalactosylated G0, monogalactosylated G1, and digalactosylated G2, which are further modified by core-fucosylation (F) and bisecting N-acetylglucosamine (B) moieties such as G0F and G0FB. Interestingly, proinflammatory G0F is shown to be regulated by estrogen in vivo. Here, it is hypothesized that the regulation of G0F by estrogen contributes to sex dichotomy in RA by setting up the level of IgG-dependent inflammation and therefore, RA disease activity (Das28-CRP3). To investigate this hypothesis, IgG glycosylation was characterized in serum samples from active RA patients (n = 232) and healthy controls (n = 232) by serum N-glycan analysis using the high performance liquid chromatography. According to the results, the IgG Fc glycan phenotype originates predominantly from the structure of G0F, and both G0F and G0FB correlate with Das28-CRP3 in females, but not in males. In conclusion, IgG G0F-dependent inflammation differs in males and females, and these differences point to the differential regulation of inflammation by sex hormone estrogen via IgG glycosylation.

Biomarkers to Personalize the Treatment of Rheumatoid Arthritis: Focus on Autoantibodies and Pharmacogenetics

Rheumatoid arthritis (RA) is a chronic inflammatory disease that is very complex and heterogeneous. If not adequately treated, RA patients are likely to manifest excess of morbidity and disability with an important impact on the quality of life. Pharmacological treatment is based on the administration of the disease-modifying antirheumatic drugs (DMARDs), subdivided into conventional synthetic (csDMARDs), targeted synthetic (tsDMARDs), and biological (bDMARDs). bDMARDs are now frequently administered in patients, both as alternative treatment and together with csDMARDs. Unfortunately, there is a therapeutic response variability both to old and new drugs. Therefore, to identify pre-therapeutic and on-treatment predictors of response is a priority. This review aims to summarize recent advances in understanding the causes of the variability in treatment response in RA, with particular attention to predictive potential of autoantibodies and DMARD pharmacogenetics. In recent years, several biomarkers have been proposed to personalize the therapy. Unfortunately, a magic bullet does not exist, as many factors concur to disease susceptibility and treatment outcomes, acting around the patient’s congenital background. Models integrating demographic, clinical, biochemical, and genetic data are needed to enhance the predictive capacity of specific factors singularly considered to optimize RA treatment in light of multidisciplinary patient management.

Long Noncoding RNAs and Circular RNAs in Autoimmune Diseases

Immune responses are essential for the clearance of pathogens and the repair of injured tissues; however, if these responses are not properly controlled, autoimmune diseases can occur. Autoimmune diseases (ADs) are a family of disorders characterized by the body's immune response being directed against its own tissues, with consequent chronic inflammation and tissue damage. Despite enormous efforts to identify new drug targets and develop new therapies to prevent and ameliorate AD symptoms, no definitive solutions are available today. Additionally, while substantial progress has been made in drug development for some ADs, most treatments only ameliorate symptoms and, in general, ADs are still incurable. Hundreds of genetic loci have been identified and associated with ADs by genome-wide association studies. However, the whole list of molecular factors that contribute to AD pathogenesis is still unknown. Noncoding (nc)RNAs, such as microRNAs, circular (circ)RNAs, and long noncoding (lnc)RNAs, regulate gene expression at different levels in various diseases, including ADs, and serve as potential drug targets as well as biomarkers for disease progression and response to therapy. In this review, we will focus on the potential roles and genetic regulation of ncRNA in four autoimmune diseases-systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, and type 1 diabetes mellitus.

Prevalence of anti-cyclic citrullinated peptide antibodies in patients with spondyloarthritis: A retrospective study

OBJECTIVES

Anti-cyclic citrullinated peptide (CCP) antibodies are frequently detected in the sera of patients with rheumatoid arthritis (RA). However, recent studies have revealed a potentially high prevalence rate of these antibodies in patients with other rheumatic disorders, causing confusion while diagnosing RA. Therefore, this study aimed to evaluate the positive rate of anti-CCP antibodies in other chronic arthritis diseases focusing on patients with spondyloarthritis (SpA).

METHODS

A total of 109 patients who were diagnosed with SpA at Yukioka Hospital from 1993 to 2018 were included in this retrospective analysis, including patients with ankylosing spondylitis (AS); psoriatic arthritis (PsA); synovitis, acne, pustulosis, hyperostosis, and osteitis syndrome (SAPHO); undifferentiated spondyloarthritis (uSpA); reactive arthritis (ReA); and inflammatory bowel disease-associated SpA (IBD).

RESULTS

Overall, 15.3% (16/109) of patients with SpA were positive for anti-CCP antibodies, including 2.3% (1/43) in AS, 23.1% (3/13) in SAPHO, 35.0% (7/20) in PsA, 14.8% (4/27) in uSpA, 0% (0/3) in ReA, and 33.3% (1/3) in IBD.

CONCLUSION

PsA patients have a significantly higher prevalence rate of positive anti-CCP antibodies among SpA patients, and the positive rates in SAPHO and uSpA were also high. These findings provide insight into the heterogeneity of SpA with relevance for RA differential diagnosis.

Upregulation of circulating inflammatory biomarkers under the influence of periodontal disease in rheumatoid arthritis patients

OBJECTIVES

Periodontal disease (PD) and rheumatoid arthritis (RA) are chronic immuno-inflammatory conditions with osteolysis being a hallmark feature. The influence of PD on RA's systemic inflammatory status and disease activity remains unclear. The objective of this study was to assess the systemic inflammation and disease activity of RA under the influence of PD.

METHODS

In this case-control study, 38 RA patients (19 with PD and 19 without PD) were compared to 38 non-RA patients and 12 healthy controls. Periodontal parameters (bleeding on probing (BOP), probing pocket depth (PPD), PPD Total, PPD Disease and marginal bone loss (MBL) were determined. Serological analyses included quantification of 92 inflammatory biomarkers using a multiplex proximity extension assay, anti-citrullinated protein antibodies (ACPA), rheumatoid factor (IgM-RF) and erythrocyte sedimentation rate (ESR). RA disease activity was determined using Disease Activity Score for 28 joints (DAS28). All RA patients were on medication.

RESULTS

IgM-RF was higher in RA patients with PD. PD conditions were more severe in the non-RA group. Inflammatory biomarkers (IL-10RB, IL-18, CSF-1, NT-3, TRAIL, PD-L1, LIF-R, SLAMF1, FGF-19, TRANCE, CST5, STAMPB, SIRT2, TWEAK, CX3CL1, CXCL5, MCP-1) were significantly higher in RA patients with PD than RA without PD. DAS28 associated with twice as many inflammatory biomarkers in RA patients with PD whereas IgM-RF and ACPA associated more frequently with biomarkers in the RA without PD group. IgM-RF correlated inversely with BOP.

CONCLUSION

Periodontal disease augments systemic inflammation in RA. A profound influence exists independent of autoimmune status.

Low Level Antibodies Against Alpha-Tropomyosin Are Associated With Increased Risk of Coronary Heart Disease

Objective

Natural autoantibodies have been implicated to play a key role in the pathogenesis of coronary heart disease (CHD) because they augment autoimmune activation. The aim of this study was to identify novel specific autoantibodies of CHD, and analyze the relationship between their levels and CHD risk indicators.

Approach and Results

First, clinical data and sera from CHD patients were collected. Then, one protein microarray containing 37 proteins that represent candidate autoantigens was developed. The arrays were used to profile autoantibodies in randomly selected sera from 35 samples (20 CHD patients, and 15 healthy controls). After that, microarray data were analyzed and autoantibodies for CHD were screened out. Then, ELISA detection was conducted to validate the differentiable autoantibodies using larger numbers of serum samples (131 CHD patients, and 131 healthy controls). Finally, the associations of antibodies with CHD risk indicator parameters were assessed. Inter-group comparison by microarray indicated that three CHD novel autoantibodies, including glucose-6-phosphate isomerase (G6PI), alpha-tropomyosin (TPM1), and heterogeneous nuclear ribonucleoprotein D-like (HnRNPDL), were significantly (P < 0.05) increased when compared with the healthy controls. Moreover, a significant increase of IgG autoantibodies for these three autoantigens was confirmed in CHD patients by ELISA (P < 0.0001). The correction analysis revealed a negative correlation of anti-TPM1 antibody levels and total cholesterol (P = 0.0034), and low-density lipoprotein cholesterol (P = 0.0086), respectively.

Conclusion

G6PI, TPM1, and HnRNPDL were CHD natural autoantigens, and serum anti-TPM1 antibody could be used as a potential marker to predict the risk for CHD patients.

Electrochemical biosensor for the simultaneous determination of rheumatoid factor and anti-cyclic citrullinated peptide antibodies in human serum

A dual electrochemical biosensor for the simultaneous determination of rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCPA) autoantibodies used as biomarkers for the detection of rheumatoid arthritis autoimmune disease is developed.

Identification of Characteristic Autoantibodies Associated With Deficiency Pattern in Traditional Chinese Medicine of Rheumatoid Arthritis Using Protein Chips

Background: Rheumatoid arthritis (RA) is an autoimmune disease. Based on traditional Chinese medicine (TCM) theory, deficiency pattern (DP) which leads to specific treatment principles in clinical management is a crucial pattern diagnosis among RA patients, and autoantibodies have potential implications in TCM pattern classification. The purpose of this study was to identify specific RA DP-associated autoantibodies.

Methods: RA DP patients, RA nondeficiency pattern (NDP) patients and healthy controls (HCs) were recruited for this study. Then, clinical data and sera from all subjects were collected. After that, the sera were probed with protein chips, which were constructed by known RA related autoantigens, to screen for DP-associated candidate autoantibodies. Lastly, candidate autoantibodies were validated via enzyme-linked immunosorbent assay (ELISA) and function was evaluated by network analysis.

Results: Protein chips results showed that RA patients have higher levels of anti-vascular endothelial growth factor (VEGF) A165 antibodies than HC (P < 0.005); anti-VEGFA165 antibodies levels of patients with RA DP were lower than patients with RA NDP (P < 0.05). The results of the ELISA also showed statistically significant differences in anti-VEGFA165 antibodies between the RA and HC group (P < 0.0001); and there were statistically significant differences in anti-VEGFA165 antibodies between the RA DP and RA NDP group (P < 0.05). Network analysis results suggested IL-6 signaling pathway has a significant effect on VEGFA165 in RA patients.

Conclusion: Autoantibodies identification in RA using protein chips help in understanding DP in TCM. Discovery of anti-VEGFA165 antibodies may provide the possibility for clinical precision treatment.

Association of Changes in Anticitrullinated Protein Antibody Levels With Resource Use and Disease Activity Measures in Rheumatoid Arthritis Patients a US Observational Cohort

PURPOSE

Anticitrullinated protein antibody (ACPA) concentration, beyond ACPA positivity, is indicative of more aggressive radiographic progression in patients with rheumatoid arthritis (RA). However, there is limited information on the association of changes in ACPA with resource use measures and/or disease activity measures. We evaluate associations between changes in levels of ACPA and outcomes, including durable medical equipment (DME) use, hospitalizations, and disease activity, in patients with established RA.

METHODS

Patients from the Brigham and Women's Hospital Rheumatoid Arthritis Sequential Study who had ACPA measurements at baseline and month 12 were included. Changes in ACPA levels from baseline to month 12 were categorized as a decrease (<-10%), no change (-10% to +10%), or increase (>+10%). DME use and hospitalizations were assessed twice yearly using patient questionnaires; disease activity was assessed annually. Binary multivariate logistic regression was used to analyze the association between changes in ACPA levels and DME use and hospitalizations; linear regression was used to assess the association with disease activity.

FINDINGS

Of 840 patients included in the analysis, 291 (34.6%), 266 (31.7%), and 283 (33.7%) had a decrease, no change, or increase in ACPA levels, respectively. A decrease in ACPA levels was associated with a reduction in DME use (adjusted odds ratio [aOR] = 0.64; 95% CI, 0.44-0.93; P = 0.02) and hospitalizations (aOR = 0.62; 95% CI, 0.41-0.95; P = 0.03) versus no change or increase. Adjusted mean changes in disease activity score in 28 joints (C-reactive protein), total and swollen joint counts, and pain scores were significantly greater in patients with decreased ACPA levels versus those with no change or increase (P < 0.05).

IMPLICATIONS

Among patients with RA, reductions in ACPA levels of >10% were associated with reductions in DME use, hospitalizations, and disease activity. ClinicalTrials.gov identifier: NCT01793103.

Chronic hepatitis B viral infection among RA patients-a cross-sectional control study

BACKGROUND AND OBJECTIVES

Rheumatoid arthritis (RA) is the most common inflammatory joint disorder presenting also with extra-articular manifestations. As many other autoimmune diseases, it has been suggested that infectious diseases might contribute to its emergence. Hepatitis viruses were suggested by several reports as a trigger of RA onset. We aimed to assess the association between RA and chronic hepatitis B viral infection (HBV).

METHODS

Patients with RA were compared with age- and sex-matched controls regarding the proportion of chronic HBV infection in a case-control study. The chi-square and t tests were used for univariate analysis, whereas a logistic regression model was used for multivariate analysis. The study was performed utilizing the medical database of Clalit Health Services.

RESULTS

There was a significantly higher proportion of chronic HBV infection in RA patients compared with controls (1.19% vs 0.63%, respectively; p < 0.001). In a multivariate logistic regression analysis, RA was significantly associated with chronic HBV infection (OR = 1.89, 95%CI 1.55-2.29, p < 0.001).

CONCLUSIONS

Patients with RA have a greater proportion of chronic HBV infection than matched controls. Screening for HBV infection among RA patients may be warranted.

A novel antimicrobial peptide-derived vehicle for oligodeoxynucleotide delivery to inhibit TNF-α expression

Indolicidin (IL), an antimicrobial peptide, was investigated as a vehicle to promote oligodeoxynucleotides (ODNs) delivery. To increase charge density, IL was dimerized by adding a cysteine to its C or N terminus, which was denoted as ILC or CIL, respectively. In contrast to IL, cytotoxicity of ILC and CIL was significantly reduced because these dimeric peptides were longer than IL, which restricted their insertions to cell membrane. In contrast to ILC, CIL displayed well loading efficiency. These peptides were applied to deliver ODNs against tumor necrosis factor-α (TNF-α) because TNF-α is a pro-inflammatory cytokine which plays an important role in immunological diseases. Although IL/ODN slightly reduced TNF-α expression, the high cytotoxicity restricted its application window. Furthermore, ILC/ODN was incapable of inducing gene silence due to its low encapsulation efficiency and poor endosomal escape. In contrast, CIL exhibited excellent ODN transportation and the internalized CIL/ODN complexes may escape from endosomes. Therefore, TNF-α expression can be specifically reduced by CIL/ODN complexes, and the silence effect was maintained longer than 14 h. This study provides a useful strategy of peptide vehicle design, which may facilitate the delivery of not only ODN but also other oligonucleotides, including siRNA and miRNA, to promote gene silence application.

Variations in oral microbiome profiles in rheumatoid arthritis and osteoarthritis with potential biomarkers for arthritis screening

The key to arthritis management is early diagnosis and treatment to prevent further joint destruction and maximize functional ability. Osteoarthritis (OA) and rheumatoid arthritis (RA) are two common types of arthritis that the primary care provider must differentiate, in terms of diagnosis and treatment. Effective and non-invasive strategies for early detection and disease identification are sorely needed. Growing evidence suggests that RA has a correlation with oral microbiome and may be affected by its dynamic variations. There is already a study comparing oral microbiome in patients with RA and OA, however, it did not screen for potential biomarkers for arthritis. In this study, we assessed the oral microbiome in saliva samples from 110 RA patients, 67 OA patients and 155 healthy subjects, using 16S rRNA gene amplicon sequencing. The structure and differences in oral microbiome between RA, OA and healthy subjects were analyzed. Eight oral bacterial biomarkers were identified to differentiate RA from OA. This report provides proof of oral microbiota as an informative source for discovering non-invasive biomarkers for arthritis screening.

Pathogenic Role of Immune Cells in Rheumatoid Arthritis: Implications in Clinical Treatment and Biomarker Development

Rheumatoid arthritis (RA) is a chronic, autoimmune, systemic, inflammatory disorder that affects synovial joints, both small and large joints, in a symmetric pattern. This disorder usually does not directly cause death but significantly reduces the quality of life and life expectancy of patients if left untreated. There is no cure for RA but, patients are usually on long-term disease modifying anti-rheumatic drugs (DMARDs) to suppress the joint inflammation, to minimize joint damage, to preserve joint function, and to keep the disease in remission. RA is strongly associated with various immune cells and each of the cell type contributes differently to the disease pathogenesis. Several types of immunomodulatory molecules mainly cytokines secreted from immune cells mediate pathogenesis of RA, hence complicating the disease treatment and management. There are various treatments for RA depending on the severity of the disease and more importantly, the patient’s response towards the given drugs. Early diagnosis of RA and treatment with (DMARDs) are known to significantly improve the treatment outcome of patients. Sensitive biomarkers are crucial in early detection of disease as well as to monitor the disease activity and progress. This review aims to discuss the pathogenic role of various immune cells and immunological molecules in RA. This review also highlights the importance of understanding the immune cells in treating RA and in exploring novel biomarkers.

3,5-Di-C-β-D-glucopyranosyl phloroacetophenone, a major component of Melicope ptelefolia, suppresses fibroblast activation and alleviates arthritis in a mouse model: Potential therapeutics for rheumatoid arthritis

Melicope ptelefolia has been traditionally used to treat rheumatism and fever. The present study aimed to investigate the therapeutic effect of 3,5-di-C-β-_d-glucopyranosyl phloroacetophenone (βGP), a main component of M. ptelefolia, on rheumatoid arthritis (RA). A model of collagen-induced arthritis (CIA) was established in mice using the RAW 264.7 murine macrophage cell line and mouse embryonic fibroblasts (MEFs). The clinical scores of arthritis, swelling, histopathological findings, and micro-computed tomography in CIA mouse paws were assessed. The levels of anti-type II collagen antibody and cytokines were determined in the plasma and cell culture supernatant, respectively. Protein and gene expression levels were analyzed by western blot and reverse transcription-quantitative polymerase chain reaction analyses. βGP significantly decreased the gross arthritic scores of CIA mice and joint swelling, and decreased articular inflammation, cartilage degradation and bone erosion. However, βGP did not exert any effect on anti-type II collagen immunoglobulin G plasma levels or inflammatory cytokine expression in macrophages. βGP significantly suppressed the expression of interleukin-6 and leukemia inhibitory factor and decreased the phosphorylation of signal transducer and activator of transcription 3, and expression of receptor activator of nuclear factor-κB ligand in tumor necrosis factor-α-stimulated MEFs and in CIA mouse paws. Osteoclast-related gene expression was significantly reduced in CIA mouse paws. Taken together, βGP suppressed the development of RA by regulating the activation of synovial fibroblasts.

Damage-Associated Molecular Patterns in Inflammatory Diseases

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules that are released from damaged or dying cells and activate the innate immune system by interacting with pattern recognition receptors (PRRs). Although DAMPs contribute to the host's defense, they promote pathological inflammatory responses. Recent studies have suggested that various DAMPs, such as high-mobility group box 1 (HMGB1), S100 proteins, and heat shock proteins (HSPs), are increased and considered to have a pathogenic role in inflammatory diseases. Here, we review current research on the role of DAMPs in inflammatory diseases, including rheumatoid arthritis, systemic lupus erythematosus, osteoarthritis, atherosclerosis, Alzheimer's disease, Parkinson's disease, and cancer. We also discuss the possibility of DAMPs as biomarkers and therapeutic targets for these diseases.

Gum Arabic Fibers Decreased Inflammatory Markers and Disease Severity Score among Rheumatoid Arthritis Patients, Phase II Trial

Background

Rheumatoid arthritis (RA) is autoimmune inflammatory disease that attacks the synovium of the joints. Both TNFa and interleukin-1 play crucial roles in the pathogenesis of RA. Gum Arabic (GA) is gummy exudates from Acacia senegal tree. Gum Arabic fermentation by colonic bacteria increases serum butyrate concentrations, so it is considered as prebiotic agent. Gum Arabic (GA) has anti-inflammatory activity through its derivative butyrate. To the best of our knowledge, this is the first study conducted to investigate GA intake on inflammatory markers among RA patients.

Patients and Methods

This is clinical trial phase II in which 40 patients were enrolled aged 18 to 70 years. Patients received 30g/day GA for 12 weeks. TNF α, ESR, and complete blood count were measured and DAS-28 was calculated before and after regular GA consumption. Study was approved by the Ethical committee of National Medicines and Poisons Board.

Results

This study showed significant decrease in level of serum TNF α (p value 0.05) [95% CI, 0.65 -16.5], ESR (p value 0.011) [95% CI, 2.6 -18.89], and number of swollen and tender joints in RA patients after 12 weeks of GA intake which reflected as significant decrease in disease severity score DAS 28 P.V:0.00 [95% CI, 1.25 -1.99]. On the other hand, GA had trivial change in blood indices.

Conclusion

Gum Arabic has favorable immune modulator effect on rheumatoid arthritis. It can be utilized in clinical practice as adjuvant therapy.

Trial Registration

This trial was registered with ClinicalTrials.gov Identifier: NCT02804581 Registered at 19 June 2016, prospective registration.

Relationship between autoantibody associated with rheumatoid arthritis and tooth loss

INTRODUCTION

This study evaluated the relationship between serum Rheumatoid Factor (RF) levels and tooth loss in a community-dwelling elderly Japanese women. It was hypothesised that women with high baseline RF levels would experience greater tooth loss over 10 years than age-matched women with lower baseline serum RF levels.

MATERIALS AND METHODS

The study population consisted of 197 women aged 70 years with ≥12 teeth at baseline. One hundred and twenty-four participants completed a 10-year follow-up and were divided into 2 groups according to their baseline serum RF levels as follows: RF negative (<15 U/mL; n = 114) and RF positive (>15 U/mL; n = 10). Negative binomial regression was used to investigate the relationship between baseline RFs and tooth lost over the 10-year period. RF and its interaction with the baseline number of teeth were independent variables, with 9 other adjustment covariates.

RESULTS

Baseline RFs were significantly associated with tooth loss (P = .035). In addition, a statistical interaction between baseline RFs and baseline number of teeth was identified (P = .023), modifying the association between RFs and tooth loss. The adjusted incidence rate ratio (IRR) for RF-positive participants with 21 baseline teeth was 1.88 (95% confidence interval (95% CI): 0.76, 4.65). IRRs obtained for participants who had 25 baseline teeth (3.02; 95% CI: 1.03, 8.83) or 30 baseline teeth (5.47; 95% CI: 1.29, 23.13) suggested that RF-positive participants with a high number of baseline teeth would exhibit greater tooth loss than RF-negative participants.

CONCLUSION

High serum RF levels were associated with a greater IRR for future tooth loss in elderly Japanese women.

The Development of Benzimidazole-Based Clickable Probes for the Efficient Labeling of Cellular Protein Arginine Deiminases (PADs)

Citrullination is the post-translational hydrolysis of peptidyl-arginines to form peptidyl-citrulline, a reaction that is catalyzed by the protein arginine deiminases (PADs), a family of calcium-regulated enzymes. Aberrantly increased protein citrullination is associated with a slew of autoimmune diseases (e.g., rheumatoid arthritis (RA), multiple sclerosis, lupus, and ulcerative colitis) and certain cancers. Given the clear link between increased PAD activity and human disease, the PADs are therapeutically relevant targets. Herein, we report the development of next generation cell permeable and "clickable" probes (BB-Cl-Yne and BB-F-Yne) for covalent labeling of the PADs both in vitro and in cell-based systems. Using advanced chemoproteomic technologies, we also report the off targets of both BB-Cl-Yne and BB-F-Yne. The probes are highly specific for the PADs, with relatively few off targets, especially BB-F-Yne, suggesting the preferential use of the fluoroacetamidine warhead in next generation irreversible PAD inhibitors. Notably, these compounds can be used in a variety of modalities, including the identification of off targets of the parent compounds and as activity-based protein profiling probes in target engagement assays to demonstrate the efficacy of PAD inhibitors.

Capillary electrophoresis-laser-induced fluorescence (CE-LIF)-based immunoassay for quantifying antibodies against cyclic citrullinated peptides

CE-LIF based immunoassay to quantify antibodies against cyclic citrullinated peptides in rheumatoid arthritis patients.

Proteomics analysis reveals differential pattern of widespread protein expression and novel role of histidine-rich glycoprotein and lipopolysaccharide-binding protein in rheumatoid arthritis

Rheumatoid factor (RF) is an auto-antibody against antigen-antibody immune complexes. RF is valuable as a biomarker for the screening of autoimmune and infectious diseases. However, it is suggested that RF would be a more powerful biomarker when used complementarily with RF-correlated proteins. In this study, we utilized a proteomic approach to analyze global protein expression in RF-low and RF-high subjects using high-performance liquid chromatography tandem mass spectrometry. Histidine-rich glycoprotein (HRG) and lipopolysaccharide-binding protein (LBP) were found to be differentially expressed between RF-low and RF-high subjects (cut-off > 2-fold, p < 0.05), which was validated by enzyme-linked immunosorbent assay. To evaluate whether both proteins allow discriminating rheumatoid arthritis patients from healthy controls, receiver-operating characteristic (ROC) curves were analyzed. Areas under the ROC curves of HRG and LBP were 0.861 and 0.888, respectively. The correlation between RF and HRG was statistically significant (p = 0.003), and LBP was also correlated with RF (p = 0.044), as indicated by correlation analysis. HRG and LBP are reportedly involved in RF-producing and RF-correlated diseases. Thus, we propose that HRG and LBP could be useful screening markers for RF-correlated diseases.

Effect of Anticitrullinated Protein Antibody Status on Response to Abatacept or Antitumor Necrosis Factor-α Therapy in Patients with Rheumatoid Arthritis: A US National Observational Study

Objective.

Assess whether baseline anticyclic citrullinated peptide antibodies (anti-CCP) status is associated with treatment response in patients with rheumatoid arthritis (RA) initiating abatacept (ABA) or a tumor necrosis factor-α inhibitor (TNFi).

Methods.

Using the Corrona RA registry, patients were identified who initiated ABA or a TNFi (June 2004–January 2015), had a followup visit 6 months (± 3 mos) after initiation, and anti-CCP measured at or prior to initiation. Primary outcome was mean change in Clinical Disease Activity Index (CDAI) from initiation to 6 months. Treatment response was evaluated based on a typical patient profile (female, aged 57 yrs, body mass index of 30 kg/m2, baseline CDAI of 20, 1 prior biologic, and no comorbidities other than RA). Secondary outcomes included remission and low disease activity.

Results.

There were 566 ABA initiators [anti-CCP+ (≥ 20 units/ml): n = 362; anti-CCP− (< 20 units/ml): n = 204] and 1715 TNFi initiators (anti-CCP+: n = 1113; anti-CCP−: n = 602). Differences between treatment groups included baseline disease duration, CDAI, and prior biologic use. At 6 months, anti-CCP+ ABA initiators were associated with significantly greater CDAI response versus anti-CCP− ABA initiators; no significant difference was observed for TNFi initiators. When considering a typical RA patient profile, CDAI response was greater in anti-CCP+ versus anti-CCP− ABA initiators; anti-CCP+ versus anti-CCP− TNFi initiators were similar. Secondary outcome responses were also greater in anti-CCP+ versus anti-CCP− ABA initiators; TNFi initiators did not differ by anti-CCP status.

Conclusion.

In a US-based clinical practice setting, anti-CCP status was associated with a differential treatment response to ABA, but not TNFi.

Strongly positive anti-CCP antibodies in patients with sacroiliitis or reactive arthritis post-E. coli infection: A mini case-series based review

We report here on four cases of patients with strongly positive anti-citrullinated cyclic peptides (anti-CCP) antibodies and clinical features of seronegative spondyloarthritis (SpA) and reactive arthritis. The four patients had various clinical presentations: one had an initial diagnosis of seropositive rheumatoid arthritis (RA) with involvement of the sacroiliac joints (similar to previous reports of the association of two diseases); one had a clinical picture of reactive arthritis following an episode of an Escherichia coli positive urinary tract infection; and two had asymmetrical sacroiliitis (SII), but no evidence of peripheral joint involvement (never reported before). In all cases, high titers of anti-CCP antibodies were found. We present a comparison of the clinical manifestations, radiographic features and treatment regimens of these cases. Our report supports previous literature data of possible overlap existing between RA and SpA, but also presents for the first time the association of high titers of anti-CCP antibodies with SII and reactive arthritis in patients with no peripheral small joint involvement.

Probing the Roles of Calcium-Binding Sites during the Folding of Human Peptidylarginine Deiminase 4

Our recent studies of peptidylarginine deiminase 4 (PAD4) demonstrate that its non-catalytic Ca²⁺-binding sites play a crucial role in the assembly of the correct geometry of the enzyme. Here, we examined the folding mechanism of PAD4 and the role of Ca²⁺ ions in the folding pathway. Multiple mutations were introduced into the calcium-binding sites, and these mutants were termed the Ca1_site, Ca2_site, Ca3_site, Ca4_site and Ca5_site mutants. Our data indicate that during the unfolding process, the PAD4 dimer first dissociates into monomers, and the monomers then undergo a three-state denaturation process via an intermediate state formation. In addition, Ca²⁺ ions assist in stabilizing the folding intermediate, particularly through binding to the Ca3_site and Ca4_site to ensure the correct and active conformation of PAD4. The binding of calcium ions to the Ca1_site and Ca2_site is directly involved in the catalytic action of the enzyme. Finally, this study proposes a model for the folding of PAD4. The nascent polypeptide chains of PAD4 are first folded into monomeric intermediate states, then continue to fold into monomers, and ultimately assemble into a functional and dimeric PAD4 enzyme, and cellular Ca²⁺ ions may be the critical factor governing the interchange.

Epitope Specificity of Anti-Citrullinated Protein Antibodies

Anti-citrullinated protein antibodies are primarily associated with a progressive course in the autoimmune disease rheumatoid arthritis, a disease with a chronic and inflammatory nature. These antibodies do not appear to have any strict dependency for reactivity except from the presence of the non-genetically encoded amino acid citrulline, which is the result of a posttranslational modification, catalyzed by calcium-dependent peptidylarginine deiminase enzymes. Nevertheless, several amino acids surrounding the citrulline residue notably influence antibody reactivity, especially with a central-Cit-Gly-motif being essential for antibody reactivity. Most importantly, these antibodies have been proposed to be divided into two groups, based on their ability to recognize multiple citrullinated peptides. Thus, an "overlapping" antibody group, which appears to recognize several citrullinated peptides, and a "non-overlapping" antibody group, which only recognizes a limited number of citrullinated peptides, have been proposed. Based on these findings, we suggest that antibodies recognizing several citrullinated targets, also referred to as cross-reactive antibodies, primarily are backbone-dependent, whereas less cross-reactive antibodies primarily depend on the side chains of the amino acids comprising the epitopes for stable antibody-antigen interactions, which reduces the degree of cross-reactivity significantly. Clarifying the reactivity pattern of anti-citrullinated protein antibodies may contribute to determining their true nature of origin.

Identification of novel autoantigens via mass spectroscopy-based antibody-mediated identification of autoantigens (MS-AMIDA) using immune thrombocytopenic purpura (ITP) as a model disease

Immune thrombocytopenic purpura (ITP) is one of the best characterized autoimmune diseases. Autoantibodies (AABs) against platelet antigens are considered as the diagnostic hallmark of ITP, but are detectable in only 50% of patients. We designed and applied a novel proteomic approach termed Mass Spectroscopy-based Antibody-Mediated Identification of Autoantigens (MS-AMIDA) for platelet antigens. Patients were separated into patients with classical AABs [ITP(+)] and patients without AABs [ITP(-)]. Altogether, 181 potential AAGs were found in ITP(+) and 135 AAGs in ITP(-), with 34 and 23 AAGs reproducibly found in two runs of MS-AMIDA. After subtracting identifiers from the controls, 57 AAGs in ITP(+) and 29 AAGs in ITP(+) remained, with 16 AAGs commonly found in ITP(+) and ITP(-) patients. Label-free quantification (LFQ) revealed 15 potential AAGs that are quantitatively stronger in ITP. Dot blot validation was performed on hexokinase 1 (HK1), E1 pyruvate dehydrogenase (E1-PDH), coagulation factor XIII, filamin A (FLNA), non-muscle myosin 9. Eleven patients were found to have anti-HK1 AABs, one patient had anti-E1-PDH AABs, and two patients had anti-FLNA AABs. Most antigens were of intracellular origin with significant association with actin-cytoskeleton and regulation of programmed cell death. In conclusion, novel AAGs for ITP were identified using MS-AMIDA.

High Concentrations of Angiopoietin-Like Protein 4 Detected in Serum from Patients with Rheumatoid Arthritis Can Be Explained by Non-Specific Antibody Reactivity

Angiopoietin-like protein 4 (ANGPTL4) is suggested to be a master regulator of plasma triglyceride metabolism. Our aim was to study whether the previously reported high levels of ANGPTL4 detected in serum from patients with rheumatoid arthritis (RA) by ELISA was due to any specific molecular form of this protein (oligomers, monomers or fragments). ANGPTL4 levels were first determined in serum from 68 RA patients and 43 age and sex matched control subjects and the mean values differed by a factor of 5.0. Then, ANGPTL4 was analyzed after size exclusion chromatography (SEC) of serum samples. With serum from one of the RA patients with high levels of ANGPTL4, the dominant reactivity was found in fractions corresponding to high-molecular weight proteins. In addition, a minor peak of reactivity eluting late from the column was found both in the patient and in controls. By the use of HeteroBlock®, and by careful selection of antibodies, we documented non-specific reactions for ANGPTL4 in 39% of samples from the RA patients, most likely due to cross-reactivity of the antibodies with rheumatoid factor (RF). The corresponding figure for control subjects was 6.3%. After corrections for non-specific reactions, the mean level of ANGPTL4 in serum from RA patients was still significantly higher than in control individuals (mean levels were 101±62 and 67±39 ng/ml respectively, P = 0.02). We re-analyzed samples from our previously published studies on ANGPL4 levels in patients on hemodialysis and patients with diabetes type 2. These samples did not show false positive reactions. The levels of ANGPTL4 were comparable to those detected previously.

In vitro allogeneic immune cell response to mesenchymal stromal cells derived from human adipose in patients with rheumatoid arthritis

We investigated the regulatory activity of human adipose-derived mesenchymal stromal cells (MSCs) (n=10) towards immune cells in a cohort of 84 rheumatoid arthritis (RA) patients, 36 apparently healthy controls. We co-cultured MSCs with lymphocyte subsets of T, B, and T regulatory cells (Tregs). Levels of the pro- and anti-inflammatory markers (tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), and interleukin-10 (IL-10)) were estimated in serum and co-culture supernatants. The study revealed a two-fold increase in the proportion of Tregs and an increased level of CD4⁺CD25⁺FoxP3. MSCs altered T cell, B cell, and Treg cytokine production during an anti-inflammatory immune response. The MSCs inhibited CD3+T cell-mediated TNF-α secretion, upregulated IL-10, and suppressed the production of autoantibodies against citrullinated protein antigens produced by B cells. These data offer insight into the interactions between allogeneic MSCs and immune cells, and elucidate the dose-dependent modulation of MSCs.

High-Resolution Analysis of Antibodies to Post-Translational Modifications Using Peptide Nanosensor Microarrays

Autoantibodies are a hallmark of autoimmune diseases such as lupus and have the potential to be used as biomarkers for diverse diseases, including immunodeficiency, infectious disease, and cancer. More precise detection of antibodies to specific targets is needed to improve diagnosis of such diseases. Here, we report the development of reusable peptide microarrays, based on giant magnetoresistive (GMR) nanosensors optimized for sensitively detecting magnetic nanoparticle labels, for the detection of antibodies with a resolution of a single post-translationally modified amino acid. We have also developed a chemical regeneration scheme to perform multiplex assays with a high level of reproducibility, resulting in greatly reduced experimental costs. In addition, we show that peptides synthesized directly on the nanosensors are approximately two times more sensitive than directly spotted peptides. Reusable peptide nanosensor microarrays enable precise detection of autoantibodies with high resolution and sensitivity and show promise for investigating antibody-mediated immune responses to autoantigens, vaccines, and pathogen-derived antigens as well as other fundamental peptide-protein interactions.

Use of Rheumatology Laboratory Studies Among Primary Pediatricians

Rheumatology laboratory tests are often inappropriately ordered in situations for which they are of low diagnostic utility. We surveyed pediatricians to investigate reasons for ordering these tests. The response rate was 15.3% (93/609). The most commonly ordered tests were antinuclear antibody (ANA), anti-double-stranded DNA (dsDNA) antibody, and rheumatoid factor (RF). Of the 89% (83/93) who ordered an ANA, 86% ordered it for correct/possibly correct reasons; of the 73% (68/93) who ordered RF, 80% did so for correct/possibly correct reasons; and among the 59% (54/92) who had ordered anti-dsDNA antibody, 34% ordered it for correct reasons. A positive relationship was seen between years since residency completion and correct use of ANA. However, positive associations were not seen between measures of pediatric rheumatology experience and correct use of other tests. Interventions are needed to improve pediatricians' utilization of rheumatology tests.

Diagnostic accuracy of anti-MCV and anti-CCP antibodies in rheumatoid arthritis: A meta-analysis

OBJECTIVE

The purpose of this study was to compare the diagnostic performance of anti-mutated citrullinated vimentin (anti-MCV) and anti-cyclic citrullinated peptide (anti-CCP) antibodies in rheumatoid arthritis (RA).

METHODS

We searched the Medline, Embase, and Cochrane library databases and performed two meta-analyses on the diagnostic accuracy of anti-MCV and anti-CCP in patients with RA compared to healthy controls.

RESULTS

We identified 12 studies that included a total of 2003 RA patients and 831 healthy controls for the meta-analysis. The pooled sensitivity and specificity of anti-MCV were 68.6% [95% confidence interval (CI) 66.6-79.7] and 94.2% (95% CI 92.4-96.7) and those of anti-CCP were 61.7% (95% CI 59.5-63.8) and 97.1% (95% CI 96.7-98.1), respectively. Anti-MCV PLR, NLR, and DOR were 12.99 (95% CI 8.013-21.27), 0.297 (95% CI 0.238-0.369), and 47.78 (95% CI 28.59-79.84), and those for anti-CCP were 16.71 (95% CI 11.42-24.47), 0.378 (95% CI 0.325-0.439), and 54.20 (95% CI 31.65-92.82), respectively. The AUC of anti-MCV was 0.886, and its Q* index was 0.817, indicating modest accuracy, while the AUC of anti-CCP was 0.946, and its Q* index was 0.885. The sensitivity of anti-MCV was significantly higher than that of anti-CCP in the diagnosis of RA (difference 0.069, 95% CI 0.039-0.098, p < 0.0001), but the specificity of anti-MCV was lower than that of anti-CCP (difference -0.029, 95% CI -0.051 to -0.006, p = 0.012). The Q* index of anti-MCV was significantly lower than that of anti-CCP (difference -0.068, 95% CI -0.070 to -0.065, p < 0.0001).

CONCLUSION

Our meta-analysis demonstrates that anti-MCV is more sensitive but less specific, and has lower diagnostic accuracy than anti-CCP in RA, although anti-MCV and anti-CCP showed comparable high PLRs.