Contribution of PTPN22 1858T, TNFRII 196R and HLA-shared epitope alleles with rheumatoid factor and anti-citrullinated protein antibodies to very early rheumatoid arthritis diagnosis

Biomarkers in the diagnosis, prognosis and management of rheumatoid arthritis: A comprehensive review

Rheumatoid arthritis (RA) is a chronic, systemic, autoimmune condition that primarily affects the joints and periarticular soft tissues. In the past two decades, the discovery of new biomarkers has contributed to advances in the understanding of the pathogenesis and natural history of RA. These biomarkers, including genetic, clinical, serological and imaging biomarkers, play a key role in the different stages and aspects of RA, from the so called 'pre-clinical RA', which is characterized by subclinical pathological events, such as autoimmunity and inflammation, to diagnosis (including differential diagnosis), treatment decision making and disease monitoring.This review will provide an overview on the current role of traditional and newer biomarkers in the main aspects of RA management, from the identification of individuals 'at-risk' of RA who are likely to progress to clinically evident disease, to 'early' diagnosis of RA, prognosis, precision medicine, and prediction of response to treatment.

A common missense variant rs874881 of PADI4 gene and rheumatoid arthritis: Genetic association study and in-silico analysis

The peptidylarginine-deiminase 4 (PADI4) is involved in the post-translational catalytic conversion of arginine into citrulline. The autoantibodies including anti-citrullinated protein antibodies (ACPAs) produced in response to hypercitrullinated proteins are a hallmark of rheumatoid arthritis (RA) autoimmunity. Therefore, the role of a missense variant rs874881 (Gly112Ala) of PADI4 in RA susceptibility was analyzed, along with in-silico analysis of structural and functional impacts of this substitution. We did a case-control association study and in-silico analysis. For the case-control study, confirmed RA cases and healthy controls were recruited. Genotyping for rs874881 (n = 750) was performed through polymerase chain reaction-restriction fragment length polymorphism. Multivariate logistic regression analysis was employed to determine association. The in-silico analysis was carried out through HOPE, VarMap, MutationAssessor, MutPred2, SIFT, PolyPhen, CADD, REVEL and MetaLR. In the case-control study, the rs874881 exhibited a strong association with increased RA susceptibility (G vs C odds ratio = 3.85, 95 % confidence interval = 2.81-5.27). Interaction analysis revealed significant interaction of genotype with smoking and gender (p < 0.05). Significant results (p < 0.05) were also obtained in stratified analysis by presence/absence of comorbidities and radiographic damage. According to in-silico pathogenicity prediction analysis, this Gly112Ala substitution does not exert a major effect on protein structure and function including its enzymatic activity. We report a significant association of PADI4 rs874881 with overall RA susceptibility. To our knowledge, this is the first study to do the interaction and stratified analyses on the PADI4 rs874881 in RA. Similar detailed studies should also be performed in other populations.

Genetic Polymorphism of PTPN22 in Autoimmune Diseases: A Comprehensive Review

It is known that the etiology and clinical outcomes of autoimmune diseases are associated with a combination of genetic and environmental factors. In the case of the genetic factor, the SNPs of the PTPN22 gene have shown strong associations with several diseases. The recent exploding numbers of genetic studies have made it possible to find these associations rapidly, and a variety of autoimmune diseases were found to be associated with PTPN22 polymorphisms. Proteins encoded by PTPN22 play a key role in the adaptative and immune systems by regulating both T and B cells. Gene variants, particularly SNPs, have been shown to significantly disrupt several immune functions. In this review, we summarize the mechanism of how PTPN22 and its genetic variants are involved in the pathophysiology of autoimmune diseases. In addition, we sum up the findings of studies reporting the genetic association of PTPN22 with different types of diseases, including type 1 diabetes mellitus, systemic lupus erythematosus, juvenile idiopathic arthritis, and several other diseases. By understanding these findings comprehensively, we can explain the complex etiology of autoimmunity and help to determine the criteria of disease diagnosis and prognosis, as well as medication developments.

Regulation of activated T cell survival in rheumatic autoimmune diseases

Adaptive immune responses rely on the proliferation of T lymphocytes able to recognize and eliminate pathogens. The magnitude and duration of the expansion of activated T cell clones are finely regulated to minimize immunopathology and avoid autoimmunity. In patients with rheumatic autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis, activated lymphocytes survive and exert effector functions for prolonged periods, defying the mechanisms that normally curb their capacities during acute and chronic infections. Here, we review the molecular mechanisms that limit the duration of immune responses in health and discuss the factors that alter such regulation in the setting of systemic lupus erythematosus and rheumatoid arthritis. We highlight defects that could contribute to the development and progression of autoimmune disease and describe how chronic inflammation can alter the regulation of activated lymphocyte survival, promoting its perpetuation. These concepts might contribute to the understanding of the mechanisms that underlie the chronicity of inflammation in the context of autoimmunity.

Reactivity of Rheumatoid Arthritis-Associated Citrulline-Dependent Antibodies to Epstein-Barr Virus Nuclear Antigen1-3

Rheumatoid arthritis (RA) is a chronic disease which causes joint inflammation and, ultimately, erosion of the underlying bone. Diagnosis of RA is based on the presence of biomarkers, such as anti-citrullinated protein antibodies (ACPA) and rheumatoid factors, along with clinical symptoms. Much evidence points to a link between the Epstein-Barr virus and RA. In this study, we analyzed ACPA reactivity to citrullinated peptides originating from Epstein-Barr nuclear antigens (EBNA1, EBNA2, and EBNA3) in order to elaborate the diagnostic potential of citrullinated EBNA peptides. Moreover, ACPA cross-reactivity to citrullinated peptides from myelin basic protein (MBP) was analyzed, as citrullinated MBP recently was described to be associated with multiple sclerosis, and some degree of sequence homology between MBP and citrullinated EBNA exists. A peptide from EBNA2, (EBNA2-A, GQGRGRWRG-Cit-GSKGRGRMH) reacted with approximately 70% of all RA sera, whereas only limited reactivity was detected to EBNA1 and EBNA3 peptides. Moreover, screening of ACPA reactivity to hybrid peptides of EBNA3-A (EPDSRDQQS-Cit-GQRRGDENRG) and EBNA2-A and peptides containing citrulline close to the N-terminal confirmed that ACPA sera contain different populations of ACPAs. No notable ACPA reactivity to MBP peptides was found, confirming that ACPAs are specific for RA, and that other factors than the presence of a central Cit-Gly motif are crucial for antibody binding. Collectively, these findings illustrate that citrullinated EBNA2 is an optimal candidate for ACPA detection, supporting current evidence that EBV is linked to RA onset.

PTPN22 1858 C/T polymorphism is associated with alteration of cytokine profiles as a potential pathogenic mechanism in rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is one of the most common prevalent autoimmune diseases. The 1858 C/T (rs2476601) single nucleotide polymorphism (SNP) within the PTPN22 gene has been associated with susceptibility to inflammatory based diseases in several populations. It is implicated that altered cytokine production has a potential pathogenic role in the development of RA. The aim of this work was to analyze the association of 1858 C/T PTPN22 polymorphism in RA patients with cytokine profiles.

MATERIALS AND METHODS

This study was performed on 120 RA patients who were referred to the Rheumatology Research Centre, Shariati Hospital (Tehran, Iran), and 120 healthy controls. Genomic DNA was extracted and genotyped for 1858 C/T PTPN22 gene SNP using the PCR-RFLP technique. Serum levels of IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ as well as Anti-CCP and RF was measured by ELISA method.

RESULTS

Results showed that 1858 C/T PTPN22 SNP significantly (P =  0.007, OR = 2.321, 95% CI = 1.063-5.067) associated with RA. The 1858 T allele frequency was also significantly increased in RA patients in comparison to the controls (P =  0.008, OR = 3.583, 95% CI = 1.3-9.878). Our data demonstrated a significant reduction of IL-4 and IL-10 in PTPN22 1858C/T compared to 1858C/C RA patients. In addition, upregulation of IL-6, IFN-γ, and TNF-α was observed in PTPN22 1858C/T vs. 1858C/C RA patients.

DISCUSSION

Our findings implicate altered cytokine profiles as a possible pathogenic mechanism by which the 1858 T allele may contribute to the progress of RA.

The Contribution of PTPN22 to Rheumatic Disease

One of the unresolved questions in modern medicine is why certain individuals develop a disorder such as rheumatoid arthritis (RA) or lupus, while others do not. Contemporary science indicates that genetics is partly responsible for disease development, while environmental and stochastic factors also play a role. Among the many genes that increase the risk of autoimmune conditions, the risk allele encoding the W620 variant of protein tyrosine phosphatase N22 (PTPN22) is shared between multiple rheumatic diseases, suggesting that it plays a fundamental role in the development of immune dysfunction. Herein, we discuss how the presence of the PTPN22 risk allele may shape the signs and symptoms of these diseases. Besides the emerging clarity regarding how PTPN22 tunes T and B cell antigen receptor signaling, we discuss recent discoveries of important functions of PTPN22 in myeloid cell lineages. Taken together, these new insights reveal important clues to the molecular mechanisms of prevalent diseases like RA and lupus and may open new avenues for the development of personalized therapies that spare the normal function of the immune system.

Genetic implications in the pathogenesis of rheumatoid arthritis; an updated review

Three important factors, including genetics, environment factors and autoimmunity play a role in the pathogenesis of rheumatoid arthritis (RA). The heritability of RA has been accounted to be 50-60%, while the HLA involvement in heritability of the disease has been accounted to be 10-40%. It has been documented that shared epitope (SE) alleles, such as HLA-DRB1*01 and DRB1*04, some HLA alleles like HLA-DRB1*13 and DRB1*15 are connected to RA susceptibility. An advanced classification of SE categorizes SE alleles into four main groups namely, S1, S2, S3D, and S3P. The S2 and S3P groups have been linked to susceptibility of seropositive RA. Various genome-wide association studies (GWAS) have discovered many susceptibility loci implicated in pathogenesis of RA. Some of the important single nucleotide polymorphisms (SNPs) linked to RA are TRAF1, STAT4, CTLA4, IRF5, CCR6, PTPN22, IL23R, and PADI4. HLA and non-HLA genes may discriminate anti-cyclic citrullinated peptide (anti-CCP) antibody-positive and anti-CCP-negative RA groups. Furthermore, risk of the disease has also been linked to environmental agents, mainly cigarette smoking. Pharmacogenomics has also confirmed SNPs or genetic patterns that might be linked to drugs responses. Different aspects of genetic involvement in the pathogenesis, etiology, and RA complications are reviewed in this article.

Association of STAT4 rs7574865 and PTPN22 rs2476601 polymorphisms with rheumatoid arthritis and non-systemically reacting antibodies in Egyptian patients

The aim of this study was to investigate association of protein tyrosine phosphatase non-receptor type 22 (PTPN22) rs2476601 and signal transducer and activator of transcription 4 (STAT4) rs7574865 polymorphisms with rheumatoid arthritis (RA) susceptibility and to assess potential association with the status of rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies, serum neopterin, and disease activity. RF, anti-CCP antibodies, and neopterin were assayed in serum of 100 unrelated RA patients and 114 controls. STAT4 rs7574865 G/T and PTPN22 rs2476601 C/T polymorphisms were genotyped by the TaqMan allelic discrimination method. The frequency of STAT4 variant allele was significantly higher in RA patients than in controls (p = 0.01), while the variant allele of PTPN22 was identified in only two RA patients, in a heterozygous form and in none of control subjects. The frequency of STAT4 variant allele carrier genotypes (GT+TT) was significantly higher among RA patients than in controls (43.7 vs. 10.5%, p = 0.02) and associated with RA under additive and dominant models. The frequency of RF and anti-CCP positivity was significantly higher among RA patients carrying T allele genotypes compared to patients carrying wild genotype (P = 0.02 and 0.04, respectively). No significant associations between STAT4 variant and serum neopterin or disease activity parameters were identified. Our study confirmed the association of STAT4 rs7574865 polymorphism with RA and was the first to indicate an association with RF and anti-CCP antibodies positivity. We also found PTPN22 rs2476601 has no role in susceptibility to RA in Egyptian patients.

Association of PTPN22 rs2476601 and STAT4 rs7574865 polymorphisms with rheumatoid arthritis: A meta-analysis update

BACKGROUND

Rheumatoid arthritis (RA) is a common autoimmune disease with a complex genetic background. The genes encoding protein tyrosine phosphatase non-receptor type 22 (PTPN22) and signal transducer and activator of transcription 4 (STAT4) have been reported to be associated with RA in several ethnic populations.

OBJECTIVES

This work aims to assess the association between PTPN22 rs2476601 and STAT4 rs7574865 polymorphisms with RA susceptibility through an updated meta-analysis of available case-control studies.

METHODS

A literature search of all relevant studies published from January 2007 up to December 2014 was conducted using Pubmed and Science Direct databases. The observed studies that were related to an association between PTPN22 rs2476601 and STAT4 rs7574865 polymorphisms with RA susceptibility were identified. Meta-analysis of the pooled and stratified data was done and assessed using varied genetic models.

RESULTS

Thirty-seven case-control studies with a total of 47 comparisons (29 for PTPN22 rs2476601 polymorphism and 18 for STAT4 rs7574865 polymorphism) met our inclusion criteria. The meta-analysis showed an association between PTPN22 T allele, CT+TT and TT genotypes with RA susceptibility. Furthermore, The meta-analysis showed an association between STAT4 T allele, GT+TT and TT genotypes with RA susceptibility. Stratification of RA patients according to ethnic groups showed that PTPN22 T allele, CT+TT genotypes, STAT4 T allele and STAT4 GT+TT were significantly associated with RA in European, Asian, African subjects, while PTPN22 TT genotype was significantly associated with RA in European but not in Asian and African subjects and STAT4 TT genotype was significantly associated with RA in European and Asian but not in African subject. A subgroup analysis according to the presence or absence of rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies revealed that the association between PTPN22 rs2476601 and STAT4 rs7574865 polymorphisms with RA susceptibility may not be dependent on RF and anti-CCP antibodies.

CONCLUSIONS

Our meta-analysis demonstrated that PTPN22 rs2476601 and STAT4 rs7574865 polymorphisms confers susceptibility to RA in total subjects and in major ethnic groups. The association may not be dependent on RF and anti-CCP antibodies.

Cytotoxic T lymphocyte associated antigen-4 (CTLA-4) +49 A>G gene polymorphism in Egyptian cases with rheumatoid arthritis

BACKGROUND

The gene encoding cytotoxic T lymphocyte associated antigen-4 (CTLA-4) has been reported to be associated with rheumatoid arthritis (RA) in several ethnic populations. The aim of this work is to assess the association of this polymorphism with the susceptibility, activity and functional disability of RA in Egyptian subjects.

SUBJECTS AND METHODS

This study included 112 unrelated RA Egyptian patients who were compared to 122 healthy controls from the same locality. For all subjects, DNA was genotyped for CTLA-4 +49 A>G (rs231775) polymorphism using the PCR-RFLP technique. Antibodies to cyclic citrullinated peptides (anti-CCP) were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The frequency of the CTLA-4 G allele was significantly higher among cases compared to controls (37.1% vs. 23.4%, OR=1.93; 95% CI=1.29-2.89, p=0.002). Also, the frequency of CTLA-4 +49 G allele carriage (AG+GG genotypes) was significantly higher among cases with RA compared to controls (61.6% vs. 41.8%, OR=2.23, 95% CI=1.32-3.77, p=0.003). Logistic regression analysis showed that cases positive to the G allele (GA+GG genotypes) had less frequency of rheumatoid deformities and also a lower DAS28-CRP score, yet with a higher visual analogue scale (VAS) i.e. more functional disability than other cases.

CONCLUSIONS

CTLA-4 +49 G allele carriage was associated with increased susceptibility and functional disability of RA in Egyptian patients.

PTPN22: the archetypal non-HLA autoimmunity gene

PTPN22 encodes a tyrosine phosphatase that is expressed by haematopoietic cells and functions as a key regulator of immune homeostasis by inhibiting T-cell receptor signalling and by selectively promoting type I interferon responses after activation of myeloid-cell pattern-recognition receptors. A single nucleotide polymorphism of PTPN22, 1858C>T (rs2476601), disrupts an interaction motif in the protein, and is the most important non-HLA genetic risk factor for rheumatoid arthritis and the second most important for juvenile idiopathic arthritis. PTPN22 exemplifies a shared autoimmunity gene, affecting the pathogenesis of systemic lupus erythematosus, vasculitis and other autoimmune diseases. In this Review, we explore the role of PTPN22 in autoimmune connective tissue disease, with particular emphasis on candidate-gene and genome-wide association studies and clinical variability of disease. We also propose a number of PTPN22-dependent functional models of the pathogenesis of autoimmune diseases.

Signal transducer and activator of transcription 4 (STAT4) G>T gene polymorphism in Egyptian cases with rheumatoid arthritis

BACKGROUND

The gene encoding signal transducer and activator of transcription 4 (STAT4) has been reported to be associated with rheumatoid arthritis (RA) in several populations. This work aimed at assessing the association of STAT4 G>T gene polymorphism with the susceptibility, activity and functional disability of RA in Egyptian subjects.

SUBJECTS AND METHODS

This study included 112 unrelated RA Egyptian patients who were compared to 122 healthy unrelated individuals taken from the same locality. For all subjects, DNA was genotyped for STAT4 G>T (rs7574865) polymorphism using the PCR-RFLP technique. Antibodies to cyclic citrullinated peptides (anti-CCP) were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Cases showed a significantly higher frequency of the STAT4 T allele carriage (GT+TT genotypes) compared to controls (51.8% vs. 31.1%, OR = 2.37, 95% CI = 1.39-4.05, p = 0.001). Also the frequency of the STAT4 T allele was significantly higher among cases compared to controls (30.4% vs. 16.8%, OR = 2.16, 95% CI = 1.39-3.35, p = 0.001). Cases positive to the STAT4 T allele (GT+TT genotypes) showed no significant difference compared to those with the GG genotype regarding their clinical and immune parameters. Nonetheless, they showed a more functional disability presented in their significantly higher health assessment questionnaire (HAQ) score (p = 0.02).

CONCLUSIONS

This study gives an extra evidence to the association of the STAT4 T allele with the susceptibility and functional disability of RA.

Genetics of rheumatoid arthritis - a comprehensive review

The "Bermuda triangle" of genetics, environment and autoimmunity is involved in the pathogenesis of rheumatoid arthritis (RA). Various aspects of genetic contribution to the etiology, pathogenesis and outcome of RA are discussed in this review. The heritability of RA has been estimated to be about 60 %, while the contribution of HLA to heritability has been estimated to be 11-37 %. Apart from known shared epitope (SE) alleles, such as HLA-DRB1*01 and DRB1*04, other HLA alleles, such as HLA-DRB1*13 and DRB1*15 have been linked to RA susceptibility. A novel SE classification divides SE alleles into S1, S2, S3P and S3D groups, where primarily S2 and S3P groups have been associated with predisposition to seropositive RA. The most relevant non-HLA gene single nucleotide polymorphisms (SNPs) associated with RA include PTPN22, IL23R, TRAF1, CTLA4, IRF5, STAT4, CCR6, PADI4. Large genome-wide association studies (GWAS) have identified more than 30 loci involved in RA pathogenesis. HLA and some non-HLA genes may differentiate between anti-citrullinated protein antibody (ACPA) seropositive and seronegative RA. Genetic susceptibility has also been associated with environmental factors, primarily smoking. Some GWAS studies carried out in rodent models of arthritis have confirmed the role of human genes. For example, in the collagen-induced (CIA) and proteoglycan-induced arthritis (PgIA) models, two important loci - Pgia26/Cia5 and Pgia2/Cia2/Cia3, corresponding the human PTPN22/CD2 and TRAF1/C5 loci, respectively - have been identified. Finally, pharmacogenomics identified SNPs or multiple genetic signatures that may be associated with responses to traditional disease-modifying drugs and biologics.

Differences in synovial fluid cytokine levels but not in synovial tissue cell infiltrate between anti-citrullinated peptide/protein antibody-positive and -negative rheumatoid arthritis patients

Introduction

Comparative data on synovial cell infiltrate and cytokine levels in anti citrullinated peptide/protein antibody (ACPA)-positive and ACPA negative rheumatoid arthritis (RA) patients are scarce. Our aim was to analyze synovial cell infiltrate and synovial fluid (SF) levels of cytokines in patients with RA according to the presence or absence of ACPA in serum.

Methods

A cross-sectional study in a single center including consecutive RA patients was performed. Patients were defined as 'ACPA negative' if serum was negative to two different ACPAs [second generation commercial anti-cyclic citrullinated peptide antibodies (CCP2) and chimeric fibrin/filaggrin citrullinated antibodies]. Parallel synovial tissue (ST) biopsies and SF were obtained by knee arthroscopy. Synovial cell infiltrate and endothelial cells were analyzed by immunohistochemistry and SF levels of Th1, Th2, Th17 and pro-inflammatory cytokines by Quantibody(R) Human Array.

Results

A total of 83 patients underwent arthroscopy, with a mean age of 55.9 ± 12 years, and mean disease duration of 45 months (interquartile range, IQR 10.8 to 122). 62% were female and 77% were ACPA positive. No significant differences were found in clinical variables, acute phase reactants, synovial cell infiltrate or lymphoid neogenesis (LN) between ACPA positive and negative patients. However ACPA positive patients had significantly higher levels of IL-1β, IL-10, IL-17 F and CC chemokine ligand 20 (CCL-20) than ACPA negative patients.

Conclusions

In our cohort of patients with RA no significant differences were found in synovial cell infiltrate or synovial LN according to ACPA status. However, ACPA positive patients had higher levels of T-cell derived and pro-inflammatory cytokines than ACPA negative patients. As systemic and local inflammation was similar in the two groups, these findings support a distinct synovial physiopathology.

Autoantibodies to posttranslationally modified type II collagen as potential biomarkers for rheumatoid arthritis

OBJECTIVE

Type II collagen (CII) posttranslationally modified by reactive oxygen species (ROS-CII) that are present in the inflamed joint is an autoantigen in rheumatoid arthritis (RA). The aim of this study was to investigate the potential use of anti-ROS-CII autoantibodies as a biomarker of RA.

METHODS

CII was exposed to oxidants that are present in the rheumatoid joint. Autoreactivity to ROS-CII was assessed by enzyme-linked immunosorbent assays in synovial fluid (SF) and serum samples obtained from patients during various phases of RA. This group included disease-modifying antirheumatic drug (DMARD)-naive patients with early RA (n = 85 serum samples) and patients with established RA (n = 80 serum and 50 SF samples), who were categorized as either DMARD responders or DMARD nonresponders. Control subjects included anti-citrullinated protein antibody (ACPA)-positive patients with arthralgia (n = 58 serum samples), patients with osteoarthritis (OA; n = 49 serum and 52 SF samples), and healthy individuals (n = 51 serum samples).

RESULTS

Reactivity to ROS-CII among DMARD-naive patients with early RA was significantly higher than that among patients with ACPA-positive arthralgia, patients with OA, and healthy control subjects (P < 0.0001), with 92.9% of serum samples from the patients with early RA binding to anti-ROS-II. There was no significant difference in anti-ROS-CII reactivity between ACPA-positive and ACPA-negative patients with RA, with 93.8% and 91.6% of serum samples, respectively, binding to ROS-CII. The sensitivity and specificity of binding to ROS-CII in patients with early RA were 92% and 98%, respectively. Among patients with established RA, serum reactivity in DMARD nonresponders was significantly higher than that in DMARD responders (P < 0.01); 58.3% of serum samples from nonresponders and 7.6% of serum samples from responders bound to HOCl-ROS, while the respective values for SF were 70% and 60%. In patients with longstanding RA, autoreactivity to ROS-CII changed longitudinally.

CONCLUSION

Autoantibodies to ROS-CII have the potential to become diagnostic biomarkers of RA.

Progression to rheumatoid arthritis in early inflammatory arthritis is associated with low IL-7 serum levels

OBJECTIVE

Early diagnosis of rheumatoid arthritis (RA) remains a challenge. Interleukin (IL)-7 is a pleiotropic cytokine that plays a central role in the development and maintenance of T-cells and has been associated with T-cell dysfunction in RA. Serum levels of IL-7 are reduced in both early and established disease. The aim of this study was to determine whether serum IL-7 can identify patients with very early inflammatory joint symptoms who will progress to RA, and to examine whether IL-7 levels predict disease persistence and radiographic progression.

METHODS

Patients with inflammatory joint symptoms<6 months followed over 5 years for progression to RA and 80 healthy controls were studied. Baseline IL-7 levels were measured by ELISA.

RESULTS

Of 250 patients, 108 developed RA (ACR 1987- criteria). IL-7 at inclusion was reduced significantly in RA compared with non-RA patients (p=0.009). IL-7 was categorised using the lower limit of the healthy control distribution (10 pg/ml). In multivariate analysis, independent predictors of RA development were: antibodies against citrullinated peptides (ACPA) positivity (p=0.001), IL-7<10 pg/ml (p=0.003) and swollen joint count (p=0.050). In the ACPA-negative subgroup (n=199), the only predictors were: DAS-44 (p=0.001), IL-7<10 pg/ml (p=0.010) and radiographic erosions (p=0.050). At 1-year follow-up, remission (DAS<1.6) was only predicted by ACPA negativity (p=0.019) and IL-7>17 pg/ml at recruitment (p=0.013).

CONCLUSION

These data demonstrate that low IL-7 levels in patients with recent onset of symptoms may have value as a diagnostic biomarker predicting the progression to RA, particularly in ACPA-negative disease, as well as being related to RA progression.

The +1858C/T PTPN22 gene polymorphism confers genetic susceptibility to rheumatoid arthritis in Mexican population from the Western Mexico

INTRODUCTION

Rheumatoid arthritis (RA) is a common autoimmune disease with a complex genetic background. The PTPN22 gene encodes lymphoid tyrosine phosphatase LYP, a potent negative regulator of T cell activation. Polymorphic variants of this gene have previously been associated with various autoimmune disorders. The +1858C/T single-nucleotide polymorphism (SNP) (rs2476601), in the exon 14 of the PTPN22 gene has been associated with susceptibility to RA in several population.

OBJECTIVE

The aim of this work was to investigate whether the +1858C/T of the PTPN22 gene is associated with susceptibility to RA in Western Mexico population.

METHODS

A total of 309 unrelated RA patients, classified according to American College of Rheumatology (ACR) 1987 criteria, as well as 347 controls residents from Western Mexico were recruited for this study. The DNA samples were genotyped for +1858C/T PTPN22 gene SNP using the PCR-RFLP technique. Antibodies to cyclic citrullinated peptides (anti-CCP) were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The frequency of +1858T risk allele was significantly increased in patients with RA compared with controls (p=0.001, OR=2.83, 95%CI=1.50-5.32). To confirm this results we established a comparison between subjects carrying of CT+TT genotypes versus those carrying CC genotype, between both groups (p=0.004, OR=2.65, 95%CI=1.33-5.36). Nevertheless, we not observed association of the +1858C/T PTPN22 gene SNP with clinical activity and functional disability in RA patients. Likewise, the +1858T variant in RA patients seropositive for anti-CCP antibodies, increased the risk for RA (p=0.008, OR=2.5, 95%CI=1.3-5.0) when we compared with controls; however, in the group of seronegative patients, no was found significant difference (p=0.1, OR=2.5, 95%CI=0.9-7.2).

CONCLUSIONS

Our results support the association of the +1858T risk allele of the +1858C/T PTPN22 polymorphism with susceptibility to RA and confirm that, in combination with anti-CCP antibodies, this SNP influence the autoimmune processes towards a development of RA in Mexican population.

Synovium CD20 expression is a potential new predictor of bone erosion progression in very-early arthritis treated by sequential DMARDs monotherapy -- a pilot study from the VErA cohort

OBJECTIVE

Because available biomarkers (rheumatoid factors [RF], anti-cyclic citrullinated autoantibodies [anti-CCP2], erythrocyte sedimentation rate at 1st hour [ESR]/C-reactive peptide [CRP] and bone erosions) are insufficient to predict rheumatoid arthritis (RA) structural damage, to determine whether synovium expression of greater or equal to 1 markers could constitute new prognostic factor(s).

METHOD

The study was conducted on 18 prospectively enrolled disease-modifying anti-rheumatic drug (DMARD)- and glucocorticoid-naïve, VErA cohort patients with very-early arthritis (median duration: 4months). Recorded at baseline were: clinical and biological (serum ESR, CRP, RF-isotypes, anti-CCP2, osteoprotegerin, receptor activator of nuclear κB-ligand [RANK-L] and cartilage oligomeric matrix protein [COMP] levels) data; synovium expression (HLA-DR, CD163, CD3, CD20, VEGF, osteoprotegerin, RANK-L, Bcl2 and global inflammation index) for a metacarpophalangeal joint-synovium biopsy. Baseline and 3-year hand-and-foot X-rays were graded with the van der Heijde-modified-Sharp score; the judgment criterion was its progression during follow-up. Pearson's product moment correlation statistics were used to test for association between paired samples.

RESULTS

A baseline, a significant relationship was found between erosive damage and markers of B-cell activation, notably the synovium CD20 expression (r=0.68; P=0.0001). Quantified by the modified-Sharp erosion score variation, the 3-year structural damage progression was significantly correlated with: serum levels of RF-IgG (r=0.75; P=0.0003), -IgM (r=0.69; P=0.001), anti-CCP2 (r=0.53; P=0.02) and RANK-L (r=0.61; P=0.007); synovium CD20 expression (r=0.70; P=0.001).

CONCLUSION

This analysis of the prognostic value of a large panel of synovium markers in a limited sample of prospectively followed, well-documented patients suggested that both synovial CD20 and serum RANK-L levels might be new predictors of structural damage progression in very-early RA.

Soluble VE-cadherin in rheumatoid arthritis patients correlates with disease activity: evidence for tumor necrosis factor α-induced VE-cadherin cleavage

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disorder that principally attacks synovial joints. However, accelerated atherosclerosis and increased cardiovascular morbidity and mortality are major clinical consequences of endothelial dysfunction in RA patients. Tumor necrosis factor α (TNFα) is the major mediator of inflammation in RA, related to vascular injury by targeting VE-cadherin, an endothelium-specific adhesion molecule of vital importance for endothelium integrity and angiogenesis. We undertook this study to examine the mechanisms regulating VE-cadherin processing by TNFα and their occurrence in RA.

METHODS

Human umbilical vein endothelial cells were used in primary culture and treated with recombinant TNFα to study VE-cadherin cleavage. Cell lysates and conditioned media were analyzed by Western blotting for VE-cadherin cytoplasmic domain and extracellular domain (VE-90) generation, respectively. VE-90 was analyzed at baseline and at the 1-year followup in sera from 63 RA patients (from the Very Early Rheumatoid Arthritis cohort) with disease duration of <6 months.

RESULTS

TNFα induced a time-dependent shedding of VE-90 in cell media. This effect was prevented by tyrosine kinase inhibitors (genistein and PP2) or by knocking down Src kinase. In contrast, tyrosine phosphatase blockade enhanced VE-cadherin cleavage, confirming the requirement of tyrosine phosphorylation processes. In addition, using the matrix metalloproteinase (MMP) activator APMA and the MMP inhibitor GM6001, we demonstrated that MMPs are involved in TNFα-induced VE-cadherin cleavage. Of major importance, VE-90 was detected in sera from the 63 RA patients and was positively correlated with the Disease Activity Score at baseline and after 1-year followup.

CONCLUSION

These findings provide the first evidence of VE-cadherin proteolysis upon TNFα stimulation and suggest potential clinical relevance of soluble VE-cadherin in management of RA.

Multinational evidence-based recommendations on how to investigate and follow-up undifferentiated peripheral inflammatory arthritis: integrating systematic literature research and expert opinion of a broad international panel of rheumatologists in the 3E Initiative

OBJECTIVE

To develop evidence-based recommendations on how to investigate and follow-up undifferentiated peripheral inflammatory arthritis (UPIA).

METHODS

697 rheumatologists from 17 countries participated in the 3E (Evidence, Expertise, Exchange) Initiative of 2008-9 consisting of three separate rounds of discussions and modified Delphi votes. In the first round 10 clinical questions were selected. A bibliographic team systematically searched Medline, Embase, the Cochrane Library and ACR/EULAR 2007-2008 meeting abstracts. Relevant articles were reviewed for quality assessment, data extraction and synthesis. In the second round each country elaborated a set of national recommendations. Finally, multinational recommendations were formulated and agreement among the participants and the potential impact on their clinical practice was assessed.

RESULTS

A total of 39,756 references were identified, of which 250 were systematically reviewed. Ten multinational key recommendations about the investigation and follow-up of UPIA were formulated. One recommendation addressed differential diagnosis and investigations prior to establishing the operational diagnosis of UPIA, seven recommendations related to the diagnostic and prognostic value of clinical and laboratory assessments in established UPIA (history and physical examination, acute phase reactants, autoantibodies, radiographs, MRI and ultrasound, genetic markers and synovial biopsy), one recommendation highlighted predictors of persistence (chronicity) and the final recommendation addressed monitoring of clinical disease activity in UPIA.

CONCLUSIONS

Ten recommendations on how to investigate and follow-up UPIA in the clinical setting were developed. They are evidence-based and supported by a large panel of rheumatologists, thus enhancing their validity and practical use.

Update on the genetic risk factors for rheumatoid arthritis

Rheumatoid arthritis (RA) is a complex disease, meaning that multiple genetic variants, environmental factors and random events interact to trigger pathological pathways. Although many of these etiological factors have not yet been identified, recent groundbreaking advances have expanded our knowledge about the genetic factors that contribute to RA. Here, we review the most recent findings on the genetic risk factors for RA. First, we give an overview of the genetics of RA and briefly describe the susceptibility loci discovered prior to the availability of genome-wide association studies (GWAS). Second, we focus on the newly discovered RA loci that have arisen from GWAS in populations of European ancestry. Through these studies, the number of established RA susceptibility loci has now grown to 13. Third, we discuss several important issues emerging from GWAS, such as ethnic heterogeneity and shared autoimmunity risk loci. Finally, we discuss what still needs to be accomplished before a more complete picture of the genetic risk to RA can be attained.

What happens before the onset of rheumatoid arthritis?

PURPOSE OF REVIEW

To give an overview of publications on presence of autoantibodies, rheumatoid factor and anticitrullinated protein/peptide antibodies (ACPAs) and their relationships to genetic markers and soluble factors as indicators of immune activation and identified predating the onset of symptoms of rheumatoid arthritis (RA).

RECENT FINDINGS

The development during recent years concerning autoantibodies with high specificity for RA, ACPAs, has confirmed previous findings of presence of autoantibodies, such as rheumatoid factors and antikeratin antibodies, years before disease onset. Particularly, ACPAs in combination with human leukocyte antigen-shared epitope alleles and PTPN22 1858T carriage increased the relative risks of developing RA compared with not having these factors. Both shared epitope alleles and 1858T variant seemed to contribute to development of ACPAs rather than independently contribute to RA. Soluble factors such as hypersensitive C-reactive protein, cytokines, cytokine receptors and chemokines are upregulated before disease onset, though, not as long antedating time as ACPAs and rheumatoid factors.

SUMMARY

Presence of ACPAs and rheumatoid factors are present several years before disease onset suggesting a gradual process leading to the development of RA. Genetic markers such as shared epitope alleles and PTPN22 1858T variant increase the relative risk for disease development. Soluble immunological markers are also increased closer to the onset of symptoms indicating activation of the immune system.

Association of common polymorphisms in known susceptibility genes with rheumatoid arthritis in a Slovak population using osteoarthritis patients as controls

Introduction

Both genetic and environmental factors contribute to rheumatoid arthritis (RA), a common and complex autoimmune disease. As well as the major susceptibility gene HLA-DRB1, recent genome-wide and candidate-gene studies reported additional evidence for association of single nucleotide polymorphism (SNP) markers in the PTPN22, STAT4, OLIG3/TNFAIP3 and TRAF1/C5 loci with RA. This study was initiated to investigate the association between defined genetic markers and RA in a Slovak population. In contrast to recent studies, we included intensively-characterized osteoarthritis (OA) patients as controls.

Methods

We used material of 520 RA and 303 OA samples in a case-control setting. Six SNPs were genotyped using TaqMan assays. HLA-DRB1 alleles were determined by employing site-specific polymerase chain reaction (PCR) amplification.

Results

No statistically significant association of TRAF1/C5 SNPs rs3761847 and rs10818488 with RA was detected. However, we were able to replicate the association signals between RA and HLA-DRB1 alleles, STAT4 (rs7574865), PTPN22 (rs2476601) and OLIG3/TNFAIP3 (rs10499194 and rs6920220). The strongest signal was detected for HLA-DRB1*04 with an allelic P = 1.2*10^-13 (OR = 2.92, 95% confidence interval (CI) = 2.18 – 3.91). Additionally, SNPs rs7574865_STAT4 (P = 9.2*10^-6; OR = 1.71, 95% CI = 1.35 – 2.18) and rs2476601_PTPN22 (P = 9.5*10^-4; OR = 1.67, 95% CI = 1.23 – 2.26) were associated with susceptibility to RA, whereas after permutation testing OLIG3/TNFAIP3 SNPs rs10499194 and rs6920220 missed our criteria for significance (P_corr = 0.114 and P_corr = 0.180, respectively).

Conclusions

In our Slovak population, HLA-DRB1 alleles as well as SNPs in STAT4 and PTPN22 genes showed a strong association with RA.

Anti-citrullinated protein/peptide autoantibodies in association with genetic and environmental factors as indicators of disease outcome in rheumatoid arthritis

Anti-citrullinated protein/peptide antibodies (ACPA) have recently emerged as sensitive and specific serological markers of rheumatoid arthritis (RA), providing superior alternative of the rheumatoid factor (RF) test in the laboratory diagnostics of RA. Citrullination is a post-translational modification of arginine by deimination, physiologically occurring during apoptosis, inflammation or keratinization. The presence of several citrullinated proteins has been demonstrated in the RA synovium. The identification of citrullinated epitopes as targets led to the development of the first and later second-generation anti-cyclic citrullinated peptide (anti-CCP) antibody assays. The anti-Sa antibody has been identified a decade ago; however, recent studies confirmed that anti-Sa is directed against citrullinated vimentin. The determination of ACPA may have important prognostic significance, since ACPA production can precede the onset of clinical RA symptoms by years. ACPA(+) individuals with early, undifferentiated arthritis may have higher risk to develop RA. ACPA has important prognostic role during the progression of RA and it has also been associated with pronounced radiographic progression. ACPA production has been associated with several genetic predisposing factors, including HLA-DRB1 and PTPN22 1858T alleles, as well as with environmental and lifestyle-related factors, primarily smoking and possibly, the use of oral contraceptives and excessive caffeine intake. Thus, the assessment of ACPA, in addition to clinical, radiographic and genetic outcome measures may be important to assess disease prognosis and aids to design effective, early therapeutic strategies.

Candidate autoantigens identified by mass spectrometry in early rheumatoid arthritis are chaperones and citrullinated glycolytic enzymes

Introduction

The aim of our study was to identify new early rheumatoid arthritis (RA) autoantibodies.

Methods

Sera obtained from 110 early untreated RA patients (<6 months) were analyzed by western blot using HL-60 cell extract, separated on one-dimensional and two-dimensional gel electrophoresis (1-DE, 2-DE). Sera from 50 healthy blood donors and 20 patients with non-RA rheumatisms were used as controls for 1-DE and 2-DE, respectively. The immunoreactive proteins were identified by MALDI-TOF mass spectrometric analysis and the presence of potential sites of citrullination in each of these proteins was evaluated. FT-ICR mass spectrometry was used to verify experimentally the effect of citrullination upon the mass profile observed by MALDI-TOF analysis.

Results

The 110 1-DE patterns allowed detection of 10 recurrent immunoreactive bands of 33, 39, 43, 46, 51, 54, 58, 62, 67 and 70 kDa, which were further characterized by 2-DE and proteomic analysis. Six proteins were already described RA antigens: heterogeneous nuclear ribonucleoprotein A2/B1, aldolase, α-enolase, calreticulin, 60 kDa heat shock protein (HSP60) and BiP. Phosphoglycerate kinase 1 (PGK1), stress-induced phosphoprotein 1 and the far upstream element-binding proteins (FUSE-BP) 1 and 2 were identified as new antigens. Post-translational protein modifications were analyzed and potentially deiminated peptides were found on aldolase, α-enolase, PGK1, calreticulin, HSP60 and the FUSE-BPs. We compared the reactivity of RA sera with citrullinated and noncitrullinated α-enolase and FUSE-BP linear peptides, and showed that antigenicity of the FUSE-BP peptide was highly dependent on citrullination. Interestingly, the anti-cyclic citrullinated peptide antibody (anti-CCP2) status in RA serum at inclusion was not correlated to the reactivity directed against FUSE-BP citrullinated peptide.

Conclusions

Two categories of antigens, enzymes of the glycolytic family and molecular chaperones are also targeted by the early untreated RA autoantibody response. For some of them, and notably the FUSE-BPs, citrullination is involved in the immunological tolerance breakdown observed earlier in RA patients. Autoantibodies recognizing a citrullinated peptide from FUSE-BP may enhance the sensibility for RA of the currently available anti-CCP2 test.

Smoking and inflammatory diseases

Smoking has an impact on the development and outcome of rheumatoid arthritis (RA) and lupus. In RA, smoking is associated with the development of the anti-cyclic citrullinated peptide (CCP2)-positive subset. This risk is increased in heavy smokers carrying at least one copy of the HLA DRB1 shared epitope (SE) alleles. Whereas this interaction between smoking and SE relevant in northern Europe, discrepant results have been observed in other geographic locations, suggesting the involvement of other environmental stimuli and/or gene polymorphisms. There is no interaction between tobacco exposure and PTPN22 1858T for the development of anti-CCP-positive or anti-CCP-negative RA. A strong association exists between smoking and the occurrence of extra-articular manifestations (subcutaneous nodules and cardiovascular events), but smoking has no influence on radiographic outcome. In lupus, tobacco exposure has an impact on the production of anti-double-stranded Desoxyribonuclic (dsDNA) and possibly on the development of the disease, as well as on disease activity/severity. In both diseases, smoking might interfere with drug efficacy.