Annette H. M. van der Helm-van Mil

Genome-wide association study meta-analysis identifies seven new rheumatoid arthritis risk loci

To identify new genetic risk factors for rheumatoid arthritis, we conducted a genome-wide association study meta-analysis of 5,539 autoantibody-positive individuals with rheumatoid arthritis (cases) and 20,169 controls of European descent, followed by replication in an independent set of 6,768 rheumatoid arthritis cases and 8,806 controls. Of 34 SNPs selected for replication, 7 new rheumatoid arthritis risk alleles were identified at genome-wide significance (P < 5 × 10−8) in an analysis of all 41,282 samples. The associated SNPs are near genes of known immune function, including IL6ST, SPRED2, RBPJ, CCR6, IRF5 and PXK. We also refined associations at two established rheumatoid arthritis risk loci (IL2RA and CCL21) and confirmed the association at AFF3. These new associations bring the total number of confirmed rheumatoid arthritis risk loci to 31 among individuals of European ancestry. An additional 11 SNPs replicated at P < 0.05, many of which are validated autoimmune risk alleles, suggesting that most represent genuine rheumatoid arthritis risk alleles.

Common variants at CD40 and other loci confer risk of rheumatoid arthritis

To identify rheumatoid arthritis risk loci in European populations, we conducted a meta-analysis of two published genome-wide association (GWA) studies totaling 3,393 cases and 12,462 controls. We genotyped 31 top-ranked SNPs not previously associated with rheumatoid arthritis in an independent replication of 3,929 autoantibody-positive rheumatoid arthritis cases and 5,807 matched controls from eight separate collections. We identified a common variant at the CD40 gene locus (rs4810485, P = 0.0032 replication, P = 8.2 × 10−9 overall, OR = 0.87). Along with other associations near TRAF1 (refs. 2,3) and TNFAIP3 (refs. 4,5), this implies a central role for the CD40 signaling pathway in rheumatoid arthritis pathogenesis. We also identified association at the CCL21 gene locus (rs2812378, P = 0.00097 replication, P = 2.8 × 10−7 overall), a gene involved in lymphocyte trafficking. Finally, we identified evidence of association at four additional gene loci: MMEL1-TNFRSF14 (rs3890745, P = 0.0035 replication, P = 1.1 × 10−7 overall), CDK6 (rs42041, P = 0.010 replication, P = 4.0 × 10−6 overall), PRKCQ (rs4750316, P = 0.0078 replication, P = 4.4 × 10−6 overall), and KIF5A-PIP4K2C (rs1678542, P = 0.0026 replication, P = 8.8 × 10−8 overall).

Autoantibodies recognizing carbamylated proteins are present in sera of patients with rheumatoid arthritis and predict joint damage

Autoimmune responses against posttranslationally modified antigens are a hallmark of several autoimmune diseases. For example, antibodies against citrullinated protein antigens (ACPA) have shown their relevance for the prognosis and diagnosis of rheumatoid arthritis (RA), and have been implicated in disease pathogenesis. It is conceivable that other autoantibody systems, recognizing other posttranslationally modified proteins, are also present in RA. Here, we describe the presence of an autoantibody system that discriminates between citrulline- and homocitrulline-containing antigens in the sera of RA-patients. IgG antibodies recognizing carbamylated (homocitrulline-containing) antigens were present in sera of over 45% of RA-patients. Likewise, anticarbamylated protein (anti-CarP) IgA antibodies were observed in 43% of RA-sera. ACPA and anti-CarP antibodies are distinct autoantibodies because, in selected double-positive patients, the anti-CarP antibody binding to carbamylated antigens could be inhibited by carbamylated antigens, but not by control or citrullinated antigens. Similarly, ACPA-binding to citrullinated antigens could only be inhibited by citrullinated antigens. In line with this observation, 16% of ACPA-negative RA-patients, as measured by a standard ACPA assay, harbored IgG anti-CarP antibodies, whereas 30% of these patients tested positive for IgA anti-CarP antibodies. The presence of anti-CarP antibodies was predictive for a more severe disease course in ACPA-negative patients as measured by radiological progression. Taken together, these data show the presence of a unique autoantibody system recognizing carbamylated, but not citrullinated, protein antigens. These antibodies are predictive for a more severe clinical course in ACPA-negative RA-patients, indicating that anti-CarP antibodies are a unique and relevant serological marker for ACPA-negative RA.

Genetic variants at CD28, PRDM1, and CD2/CD58 are associated with rheumatoid arthritis risk

To discover new rheumatoid arthritis (RA) risk loci, we systematically examined 370 SNPs from 179 independent loci with P < 0.001 in a published meta-analysis of RA genome-wide association studies (GWAS) of 3,393 cases and 12,462 controls. We used Gene Relationships Across Implicated Loci (GRAIL), a computational method that applies statistical text mining to PubMed abstracts, to score these 179 loci for functional relationships to genes in 16 established RA disease loci. We identified 22 loci with a significant degree of functional connectivity. We genotyped 22 representative SNPs in an independent set of 7,957 cases and 11,958 matched controls. Three were convincingly validated: CD2-CD58 (rs11586238, P = 1 × 10−6 replication, P = 1 × 10−9 overall), CD28 (rs1980422, P = 5 × 10−6 replication, P = 1 × 10−9 overall) and PRDM1 (rs548234, P = 1 × 10−5 replication, P = 2 × 10−8 overall). An additional four were replicated (P < 0.0023): TAGAP (rs394581, P = 0.0002 replication, P = 4 × 10−7 overall), PTPRC (rs10919563, P = 0.0003 replication, P = 7 × 10−7 overall), TRAF6-RAG1 (rs540386, P = 0.0008 replication, P = 4 × 10−6 overall) and FCGR2A (rs12746613, P = 0.0022 replication, P = 2 × 10−5 overall). Many of these loci are also associated to other immunologic diseases.

A Candidate Gene Approach Identifies the TRAF1/C5 Region as a Risk Factor for Rheumatoid Arthritis

Background Rheumatoid arthritis (RA) is a chronic autoimmune disorder affecting ∼1% of the population. The disease results from the interplay between an individuals genetic background and unknown environmental triggers. Although human leukocyte antigens (HLAs) account for ∼30% of the heritable risk, the identities of non-HLA genes explaining the remainder of the genetic component are largely unknown. Based on functional data in mice, we hypothesized that the immune-related genes complement component 5 (C5) and/or TNF receptor-associated factor 1 (TRAF1), located on Chromosome 9q33–34, would represent relevant candidate genes for RA. We therefore aimed to investigate whether this locus would play a role in RA. Methods and Findings We performed a multitiered case-control study using 40 single-nucleotide polymorphisms (SNPs) from the TRAF1 and C5 (TRAF1/C5) region in a set of 290 RA patients and 254 unaffected participants (controls) of Dutch origin. Stepwise replication of significant SNPs was performed in three independent sample sets from the Netherlands (n cases/controls = 454/270), Sweden (n cases/controls = 1,500/1,000) and US (n cases/controls = 475/475). We observed a significant association (p < 0.05) of SNPs located in a haplotype block that encompasses a 65 kb region including the 3′ end of C5 as well as TRAF1. A sliding window analysis revealed an association peak at an intergenic region located ∼10 kb from both C5 and TRAF1. This peak, defined by SNP14/rs10818488, was confirmed in a total of 2,719 RA patients and 1,999 controls (odds ratiocommon = 1.28, 95% confidence interval 1.17–1.39, p combined = 1.40 × 10−8) with a population-attributable risk of 6.1%. The A (minor susceptibility) allele of this SNP also significantly correlates with increased disease progression as determined by radiographic damage over time in RA patients (p = 0.008). Conclusions Using a candidate-gene approach we have identified a novel genetic risk factor for RA. Our findings indicate that a polymorphism in the TRAF1/C5 region increases the susceptibility to and severity of RA, possibly by influencing the structure, function, and/or expression levels of TRAF1 and/or C5.

Long-Term Impact of Delay in Assessment of Patients With Early Arthritis

OBJECTIVE During the last decade, rheumatologists have learned to initiate disease-modifying antirheumatic drugs (DMARDs) early to improve the outcome of rheumatoid arthritis (RA). However, the effect of delay in assessment by a rheumatologist on the outcome of RA has scarcely been explored. The purpose of this study was to examine the association between delay in assessment by a rheumatologist, rates of joint destruction, and probability of achieving DMARD-free remission in patients with RA. Patient characteristics associated with components of delay (by the patient, by the general practitioner [GP], and overall) were assessed. METHODS A total of 1,674 early arthritis patients from the Leiden Early Arthritis Clinic cohort were evaluated for patient delay, GP delay, and total delay in assessment by a rheumatologist. Among 598 RA patients, associations between total delay, achievement of sustained DMARD-free remission, and the rate of joint destruction over 6 years followup were determined. RESULTS The median patient, GP, and total delays in seeing a rheumatologist among patients with early arthritis were 2.4 weeks, 8.0 weeks, and 13.7 weeks, respectively. Among all diagnoses, those diagnosed as having RA or spondylarthritis had the longest total delay (18 weeks). Among the RA patients, 69% were assessed in ≥12 weeks; this was associated with a hazard ratio of 1.87 for not achieving DMARD-free remission and a 1.3 times higher rate of joint destruction over 6 years, as compared with assessment in <12 weeks. Older age, female sex, gradual symptom onset, involvement of the small joints, lower levels of C-reactive protein, and the presence of autoantibodies were associated with longer total delay. CONCLUSION Only 31% of the RA patients were assessed in <12 weeks of symptom onset. Assessment in <12 weeks is associated with less joint destruction and a higher chance of achieving DMARD-free remission as compared with a longer delay in assessment. These results imply that attempts to diminish the delay in seeing a rheumatologist will improve disease outcome in patients with RA.

Predicting arthritis outcomes—what can be learned from the Leiden Early Arthritis Clinic?

OBJECTIVES In order to allow personalized medicine, adequate prediction of disease outcome is required. In early undifferentiated arthritis (UA), prediction of the development of RA is crucial, and in case of RA predicting the severity of the disease course may guide individualized treatment decisions. METHODS A total of 570 UA patients and 676 RA patients included in the Leiden Early Arthritis Clinic cohort were studied for baseline characteristics. The disease outcomes studied were fulfillment of the 1987 ACR-RA criteria and arthritis persistence in UA patients and the rate of radiological joint destruction and achieving sustained DMARD-free remission in RA patients. RESULTS Predictive factors for fulfillment of the 1987 ACR-RA criteria and for persistent arthritis in UA were largely similar. Risk factors for a severe rate of joint destruction were: older age (P<0.001); male gender (P<0.001); longer symptom duration at first visit (P=0.048), involvement of lower extremities (P<0.001); BMI (P<0.001); high acute phase reactants, presence of IgM-RF (P<0.001); anti-CCP2 antibodies (P<0.001); anti-modified citrullinated vimentin antibodies (P<0.001) and HLA-DRB1 shared epitope alleles (P=0.001). A high BMI was associated with a lower rate of joint destruction but with a higher risk of disease persistence. The proportion of variance in joint destruction explained was 32% CONCLUSION Predictors for RA development, previously used to develop a prediction rule in UA patients, are largely similar to predictors for arthritis persistency. Only part of the joint destruction level in RA is explained by the currently known risk factors. New factors need to be identified in order to guide pharmaceutical intervention at the level of individual RA patients.

EULAR recommendations for terminology and research in individuals at risk of rheumatoid arthritis: report from the Study Group for Risk Factors for Rheumatoid Arthritis

The Study Group for Risk Factors for Rheumatoid Arthritis was established by the EULAR Standing Committee on Investigative Rheumatology to facilitate research into the preclinical and earliest clinically apparent phases of rheumatoid arthritis (RA). This report describes the recommendation for terminology to be used to define specific subgroups during different phases of disease, and defines the priorities for research in this area. Terminology was discussed by way of a three-stage structured process: A provisional list of descriptors for each of the possible phases preceding the diagnosis of RA were circulated to members of the study group for review and feedback. Anonymised comments from the members on this list were fed back to participants before a 2-day meeting. 18 participants met to discuss these data, agree terminologies and prioritise important research questions. The study group recommended that, in prospective studies, individuals without RA are described as having: genetic risk factors for RA; environmental risk factors for RA; systemic autoimmunity associated with RA; symptoms without clinical arthritis; unclassified arthritis; which may be used in a combinatorial manner. It was recommended that the prefix ‘pre-RA with:’ could be used before any/any combination of the five points above but only to describe retrospectively a phase that an individual had progressed through once it was known that they have developed RA. An approach to dating disease onset was recommended. In addition, important areas for research were proposed, including research of other tissues in which an adaptive immune response may be initiated, and the identification of additional risk factors and biomarkers for the development of RA, its progression and the development of extra-articular features. These recommendations provide guidance on approaches to describe phases before the development of RA that will facilitate communication between researchers and comparisons between studies. A number of research questions have been defined, requiring new cohorts to be established and new techniques to be developed to image and collect material from different sites.

Quantitative Heritability of Anti-Citrullinated Protein Antibody-Positive and Anti-Citrullinated Protein Antibody-Negative Rheumatoid Arthritis

OBJECTIVE The majority of genetic risk factors for rheumatoid arthritis (RA) are associated with anti-citrullinated protein antibody (ACPA)-positive RA, while far fewer genetic risk factors have been identified for ACPA-negative RA. This study was undertaken to quantify the contribution of genetic risk factors in general, and of the predisposing HLA-DRB1 shared epitope (SE) alleles in particular, to the ACPA-positive and ACPA-negative subsets of RA, by computing their heritability and assessing the contribution of the HLA SE alleles. METHODS One hundred forty-eight RA twin pairs, in which at least 1 twin of each pair had RA, were tested for ACPAs and typed for HLA-DRB1 genotypes. Heritability was assessed in a logistic regression model including a bivariate, normally distributed random effect, representing the contribution of unobserved genetic factors to RA susceptibility, with the correlation of the random effects fixed according to twin zygosity. The contribution of the HLA SE alleles to genetic variance was assessed using a similar model, except that estimates were based on genotype-specific population prevalences. RESULTS The heritability of RA among the twin pairs was 66% (95% confidence interval [95% CI] 44-75%). For ACPA-positive RA, the heritability was 68% (95% CI 55-79%), and for ACPA-negative RA it was 66% (95% CI 21-82%). Presence of the HLA SE alleles explained 18% (95% CI 16-19%) of the genetic variance of ACPA-positive RA but only 2.4% (95% CI 1.6-10%) of the genetic variance of ACPA-negative RA. CONCLUSION The heritability of ACPA-positive RA is comparable with that of ACPA-negative RA. These data indicate that genetic predisposition plays an important role in the pathogenesis of ACPA-negative RA, for which most individual genetic risk factors remain to be identified.

Prevalence of and predictive factors for sustained disease-modifying antirheumatic drug-free remission in rheumatoid arthritis: results from two large early arthritis cohorts.

OBJECTIVE Remission has become an attainable goal of rheumatoid arthritis (RA) treatment, especially since the advent of biologic antirheumatic therapy. Because little is known about patients who achieve disease remission with conventional treatment, we used 2 large independent inception cohorts to study the prevalence of and predictive factors for disease-modifying antirheumatic drug (DMARD)-free sustained remission after treatment with conventional therapy. METHODS Remission of disease was assessed in 454 patients from the Leiden Early Arthritis Clinic (EAC) and in 895 patients from the British Early Rheumatoid Arthritis Study (ERAS) who fulfilled the American College of Rheumatology 1987 revised criteria for the classification of RA and were treated with conventional therapy. Sustained DMARD-free remission was defined as fulfilling the following criteria for at least 1 year: 1) no current DMARD use, 2) no swollen joints, and 3) classification as DMARD-free remission by the patients rheumatologist. Predictive factors were identified by Cox regression analysis. RESULTS Sustained DMARD-free remission was achieved by 68 of 454 patients (15.0%) in the Leiden EAC and by 84 of 895 patients (9.4%) in the ERAS. Six factors were associated with sustained DMARD-free remission in both cohorts: acute onset, short symptom duration before inclusion, not smoking, little radiographic damage at baseline, absence of IgM rheumatoid factor (IgM-RF), and absence of HLA shared epitope alleles. In the ERAS, low disease activity at baseline was also predictive of remission. Multivariate analyses revealed symptom duration and the absence of autoantibodies (anti-cyclic citrullinated peptide 2 and IgM-RF) as independent predictors. CONCLUSION Sustained DMARD-free remission in RA patients treated with conventional therapy is not uncommon. Symptom duration at presentation and the absence of autoantibodies are associated with sustained DMARD-free remission.