The role of the shared epitope in arthralgia with anti-cyclic citrullinated peptide antibodies (anti-CCP), and its effect on anti-CCP levels

Predicting Inflammatory Arthritis in At-Risk Persons: Development of Scores for Risk Stratification

BACKGROUND

Inflammatory arthritis (IA) is an immune-related condition defined by the presence of clinical synovitis. Its most common form is rheumatoid arthritis.

OBJECTIVE

To develop scores for predicting IA in at-risk persons using multidimensional biomarkers.

DESIGN

Prospective observational cohort study.

SETTING

Single-center, Leeds, United Kingdom.

PARTICIPANTS

Persons with new musculoskeletal symptoms, a positive test result for anticitrullinated protein antibodies, and no clinical synovitis and followed for 48 weeks or more or until IA occurred.

MEASUREMENTS

A simple score was developed using logistic regression, and a comprehensive score was developed using the least absolute shrinkage and selection operator Cox proportional hazards regression. Internal validation with bootstrapping was estimated, and a decision curve analysis was done.

RESULTS

Of 455 participants, 32.5% (148 of 455) developed IA, and 15.4% (70 of 455) developed it within 1 year. The simple score identified 249 low-risk participants with a false negative rate of 5% (and 206 high-risk participants with a false-positive rate of 72%). The comprehensive score identified 119 high-risk participants with a false-positive rate of 29% (and 336 low-risk participants with a false-negative rate of 19%); 40% of high-risk participants developed IA within 1 year and 71% within 5 years.

LIMITATIONS

External validation is required. Recruitment occurred over 13 years, with lower rates of IA in later years. There was geographic variation in laboratory testing and recruitment availability.

CONCLUSION

The simple score identified persons at low risk for IA who were less likely to need secondary care. The comprehensive score identified high-risk persons who could benefit from risk stratification and preventive measures. Both scores may be useful in clinical care and should also be useful in clinical trials.

PRIMARY FUNDING SOURCE

National Institute for Health and Care Research Leeds Biomedical Research Centre.

Should We Be Screening for and Treating Periodontal Disease in Individuals Who Are at Risk of Rheumatoid Arthritis?

There is increasing evidence supporting an association between periodontal disease (PD) and rheumatoid arthritis (RA), both mechanistically and clinically. Trials have shown that treating PD in people with RA may improve RA disease activity. Patients with musculoskeletal symptoms without arthritis, who test positive for cyclic-citrullinated protein antibodies, are at risk of RA (CCP+ at-risk), with seropositivity preceding arthritis onset by months or years. Importantly, there is evidence to suggest that periodontal inflammation may precede joint inflammation in CCP+ at-risk and, therefore, this could be a trigger for RA. There has been increased research interest in RA prevention and the phenotyping of the pre-RA disease phase. This review will examine the merits of identifying individuals who are CCP+ at-risk and performing screening for PD. In addition, we discuss how PD should be treated once identified. Finally, the review will consider future research needed to advance our understanding of this disease association.

Determining in which pre-arthritis stage HLA-shared epitope alleles and smoking exert their effect on the development of rheumatoid arthritis

OBJECTIVES

The human leukocyte antigen-shared epitope (HLA-SE) alleles and smoking are the most prominent genetic and environmental risk factors for rheumatoid arthritis (RA). However, at which pre-arthritis stage (asymptomatic/symptomatic) they exert their effect is unknown. We aimed to determine whether HLA-SE and smoking are involved in the onset of autoantibody positivity, symptoms (clinically suspect arthralgia (CSA)) and/or progression to clinical arthritis.

METHODS

We performed meta-analyses on results from the literature on associations of HLA-SE and smoking with anti-citrullinated protein antibodies (ACPAs) in the asymptomatic population. Next, we studied associations of HLA-SE and smoking with autoantibody positivity at CSA onset and with progression to clinical inflammatory arthritis (IA) during follow-up. Associations in ACPA-positive patients with CSA were validated in meta-analyses with other arthralgia cohorts. Analyses were repeated for rheumatoid factor (RF), anti-carbamylated protein antibodies (anti-CarP) and anti-acetylated protein antibodies (AAPA).

RESULTS

Meta-analyses showed that HLA-SE is not associated with ACPA positivity in the asymptomatic population (OR 1.06 (95% CI:0.69 to 1.64)), whereas smoking was associated (OR 1.37 (95% CI: 1.15 to 1.63)). At CSA onset, both HLA-SE and smoking associated with ACPA positivity (OR 2.08 (95% CI: 1.24 to 3.49), OR 2.41 (95% CI: 1.31 to 4.43)). During follow-up, HLA-SE associated with IA development (HR 1.86 (95% CI: 1.23 to 2.82)), in contrast to smoking. This was confirmed in meta-analyses in ACPA-positive arthralgia (HR 1.52 (95% CI: 1.08 to 2.15)). HLA-SE and smoking were not associated with RF, anti-CarP or AAPA-positivity at CSA onset. Longitudinally, AAPA associated with IA development independent from ACPA and RF (HR 1.79 (95% CI: 1.02 to 3.16)), anti-CarP did not.

CONCLUSIONS

HLA-SE and smoking act at different stages: smoking confers risk for ACPA and symptom development, whereas HLA-SE mediates symptom and IA development. These data enhance the understanding of the timing of the key risk factors in the development of RA.

Pre-symptomatic autoimmunity in rheumatoid arthritis: when does the disease start?

It is well recognised that a state of autoimmunity, in which immunological tolerance is broken, precedes the development of symptoms in the majority of patients with rheumatoid arthritis (RA). For individuals who will later develop seropositive disease, this manifests as autoantibodies directed against proteins that have undergone specific post-translational modifications. There is evidence that the induction of this autoantibody response occurs at peripheral extra-articular mucosal sites, such as the periodontium and lung. In addition to their utility as diagnostic markers, these autoantibodies may have a pathogenic role that helps localise disease to the synovium. Alongside the development of autoantibodies, other factors contributing to pre-symptomatic autoimmunity may include dysbiosis of the gastrointestinal tract, abnormal development of lymphoid tissue, and dysregulated autonomic and lipid-mediated anti-inflammatory signalling. These factors combine to skew the balance between pro-inflammatory and anti-inflammatory signalling in a manner that is permissive for the development of clinical arthritis. We present data to support the concept that the transitions from at-risk states to systemic autoimmunity and then to classifiable RA depend on multiple “switches”. However, further prospective studies are necessary to define the molecular basis of these switches and the specific features of pre-symptomatic autoimmunity, so that preventative treatments can be targeted to individuals at high risk for RA. In this review, we analyse mechanisms that may contribute to the development of autoimmunity in at-risk individuals and discuss the relationship between this pre-symptomatic state and subsequent development of RA.

Genetic and environmental risk factors for rheumatoid arthritis

Multiple genetic and environmental factors have been associated with an increased risk for rheumatoid arthritis (RA). Of these, the strongest associations have been seen with female sex, a family history of RA, the genetic factor the "shared epitope," and exposure to tobacco smoke. There is also renewed interest in mucosal inflammation and microbial factors as contributors to the development of RA. However, the identification of a "preclinical" period of RA that can be defined as local or systemic autoimmunity as measured by autoantibodies and other biomarkers prior to the development of clinically apparent synovitis suggests that the risk factors for RA are acting long prior to first clinical evidence of IA. As such, a major challenge to the field will be to investigate the full spectrum of the development of RA, from initiation and propagation of autoimmunity during preclinical RA and transition to clinically apparent synovitis and classifiable RA, to determine which genetic and environmental factors are important at each stage of disease development. Understanding the exact role and timing of action of risk factors for RA is especially important given the advent of prevention trials in RA, and the hope that a full understanding of genetic and environmental factors in RA could lead to effective preventive interventions.

Association of human leukocyte antigen DRB1 with anti-cyclic citrullinated peptide autoantibodies in Saudi patients with rheumatoid arthritis

BACKGROUND

The genetic association between human leukocyte antigen (HLA)-DRB1 alleles and the risk of development of autoantibodies has been investigated, but there are few studies from the Gulf region.

OBJECTIVES

To investigate the association between the HLA-DRB1 shared epitope and the risk for development of autoantibodies in rheumatoid arthritis (RA) patients in a Saudi population.

DESIGN

Analytical cross-sectional study.

SETTING

Tertiary care hospital in Riyadh, Saudi Arabia.

PATIENTS AND METHODS

We enrolled consecutive Saudi RA patients attending the rheumatology clinic between January and April 2015. Previously published data on HLA typing on unmatched healthy controls were used for comparison. HLA typing was performed using sequence-specific oligonucleotide probes (SSOP). Rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibodies, and antinuclear antibodies (ANA) were also measured. Logistic regression analysis was used to study the autoantibodies as possible explanatory variables for the presence of the HLA-DRB1 shared epitope.

MAIN OUTCOME MEASURE(S)

The association between the presence of the shared epitope and the risk of developing anti-CCP antibodies, ANA, and RF.

RESULTS

In 76 patients with RA, carrying the shared epitope was associated with a significantly higher risk of having RA [OR=2.65, 95% CI (1.42-4.94), P=.0009]. However, only HLA-DRB1*04:05 was significantly as.sociated with RA [OR=3.73, 95% CI (1.61-8.96), Pc=.016]. In the logistic regression analysis, only anti-CCP was significantly associated with the shared epitope [OR=14.51, 95% CI (1.53-137.49), P=.02].

CONCLUSIONS

Our analysis indicates that the presence of the HLA-DRB1 shared epitope is strongly associated with the development of anti-CCP antibodies in Saudi patients with RA.

LIMITATIONS

A larger sample size is needed to confirm our finding.

Protective effect of HLA-DRB1*13 alleles during specific phases in the development of ACPA-positive RA

OBJECTIVE

Human leucocyte antigen (HLA)-DRB1*13 alleles are associated with protection from anticitrullinated protein antibody (ACPA)-positive rheumatoid arthritis (RA). It is, however, unknown at which phase of disease development (seroconversion, ACPA maturation, disease onset or outcome) these alleles are most important. We therefore examined the effect of HLA-DRB1*13 on: ACPA presence (systemic autoimmunity associated with RA) in individuals with and without RA, on ACPA characteristics and on clinical outcome measures.

METHODS

The effect of HLA-DRB1*13 on ACPA presence in subjects with or without RA (non-RA) was assessed in the Swedish twin registry (n=10 748). ACPA characteristics were studied in patients with ACPA-positive RA from the Swedish Epidemiological Investigation of RA (EIRA, n=1224) and the Dutch Leiden Early Arthritis Clinic (EAC, n=441). Disease activity at inclusion and disease outcome (disease-modifying antirheumatic drugs (DMARD)-free sustained remission and radiographic progression) was assessed in patients with RA from the EAC.

RESULTS

HLA-DRB1*13 is associated with protection from ACPA-positive RA (prevalence 16% vs 28% in ACPA-negative non-RA), but not with significant protection from ACPA in individuals without RA (prevalence: 22%, p value 0.09). HLA-DRB1*13 is associated with lower ACPA-levels (EIRA: 447 U/ml versus 691 U/ml, p value= 0.0002) and decreased citrullinated epitope recognition (EIRA: p<0.0001). No association between HLA-DRB1*13 and disease activity or outcome was found.

CONCLUSIONS

These data indicate that HLA-DRB1*13 mainly affects the onset of ACPA-positive RA in ACPA-positive non-RA individuals. In RA, HLA-DRB1*13 influences ACPA characteristics but not the disease course. This implies that therapeutic strategies aimed at emulating the HLA-DBR1*13 protective effect may be most effective in ACPA-positive healthy individuals at risk for RA.

New pathogenic insights into rheumatoid arthritis

PURPOSE OF REVIEW

Rheumatoid arthritis (RA) is a heterogeneous chronic immune-mediated inflammatory disease, associated with significant morbidity and reduced life expectancy. Here, we review recent discoveries; particularly those which have attempted to integrate genome-wide association studies (GWAS) with biological pathways and cell types known to play a role in disease pathology in order to expand our current understanding of the pathogenesis of RA. As the role of stromal cells in the pathogenesis of RA has been reviewed in detail in Current Opinions in Rheumatology, this area will not be covered in this review.

RECENT FINDINGS

Although our understandings of the pathogenic processes that drive disease in RA remain incomplete, remarkable advances over the past year can be highlighted. GWAS have raised awareness of important new risk loci with genes that either are the targets of approved therapies for RA, or involve pathways for drugs that could be repurposed from other disease indications such as cancer. Furthermore, promising strides have been made in predicting the likelihood of developing RA in those at risk using human leukocyte antigen (HLA), smoking, and autoantibody status prediction models. These findings give a fresh insight into RA pathogenesis and help identify new, or repurpose known therapeutic targets from other disease areas.

SUMMARY

The findings discussed in this review underscore the progress made to date and the need for future studies, investigating disease mechanisms in RA, with particular interest in at-risk RA gene loci, their function in immune and stromal cells within the synovium, and how they interact with environmental factors to initiate and perpetuate disease.

Detecting the earliest signs of rheumatoid arthritis: symptoms and examination

Signs and symptoms often occur well in advance of a formal diagnosis of rheumatoid arthritis (RA). However, these do not necessarily represent symptoms that are included in classification criteria. Their intensity, frequency, and persistence over time seem to be important in the spectrum from preclinical autoimmunity to classifiable RA. Prospective study of signs and symptoms in individuals at risk for RA will help to determine their onset and relationship with epitope spreading, cytokine evolution, sensitive imaging, and their usefulness in discriminating between individuals patients who will develop incident inflammatory arthritis versus normal controls.

The genetics of rheumatoid arthritis: risk and protection in different stages of the evolution of RA

There is now a general consensus that RA has a spectrum of disease stages that can begin many years before the onset of clinical symptoms. It is widely thought that understanding the complex interplay between genetics and environment, and their role in pathogenesis, is essential in gaining further insight into the mechanisms that drive disease development and progression. More than 100 genetic susceptibility loci have now been identified for RA through studies that have focused on patients with established RA compared with healthy controls. Studying the early preclinical phases of disease will provide valuable insights into the biological events that precede disease and could potentially identify biomarkers to predict disease onset and future therapeutic targets. In this review we will cover recent advances in the knowledge of genetic and environmental risk factors and speculate on how these factors may influence the transition from one stage of disease to another.

HLA and rheumatoid arthritis: how do they connect?

Rheumatoid arthritis (RA) is a destructive autoimmune disease that mainly affects synovial joints. RA patients can be subdivided in two distinct disease subsets based on the presence of anti-citrullinated protein antibodies (ACPA). These two disease phenotypes are associated with different environmental and genetic risk factors and clinical parameters. The HLA class II locus is the most important risk factor for ACPA-positive RA (ACPA+ RA). ACPA can be found up to 10 years before diagnosis and can be used as a predictive biomarker. During progression from breaking tolerance to a citrullinated protein to ACPA+ RA, the ACPA response matures. Recent work implicates the HLA class II locus as a risk factor in the progression from ACPA positivity to ACPA+ RA. We now propose that this locus directly influences the maturation of the ACPA response, most likely via antigen-specific T-cells providing help to ACPA-producing B-cells allowing for maturation of the citrullinated protein-specific autoantibody response. We present and discuss several models and underlying data, including antibody cross-reactivity, molecular mimicry, and neo-antigen formation, that could explain the HLA-RA connection.

Anti-cyclic citrullinated peptide antibody titer predicts time to rheumatoid arthritis onset in patients with undifferentiated arthritis: results from a 2-year prospective study

Introduction

The diagnostic, predictive and prognostic role of anti-cyclic citrullinated peptide (CCP) antibodies in rheumatoid arthritis (RA) patients is widely accepted. Moreover, detection of these antibodies in subjects presenting with undifferentiated arthritis (UA) is associated with a significant risk to develop the disease. On the other hand, clinical and prognostic significance of evaluating anti-CCP levels in subjects with inflammatory arthritis at disease onset has not been fully clarified. The goal of this prospective study is to analyze the value and prognostic significance of anti-CCP titer quantification in UA subjects.

Methods

Serial anti-CCP assays were measured in 192 consecutive patients presenting with UA lasting less than 12 weeks. Clinical and serological data and arthritis outcome were evaluated every 6 months until two years of follow-up.

Results

Anti-CCP positivity, at both low and high titer, and arthritis of hand joints significantly predicted RA at two years, risk increasing in subjects with high anti-CCP titers at baseline. Moreover, time to RA diagnosis was shorter in patients with high anti-CCP2 titers at enrollment with respect to those with low antibody concentration.

Conclusions

Presence of anti-CCP antibodies, at both low and high concentration, is significantly associated with RA development in subjects with recent onset UA. However, time interval from the onset of the first symptoms to the fulfilment of the classification criteria appears to be directly related to the initial anti-CCP level.

Environmental and gene-environment interactions and risk of rheumatoid arthritis

Multiple environmental factors including hormones, dietary factors, infections, and exposure to tobacco smoke, as well as gene-environment interactions, have been associated with increased risk for rheumatoid arthritis (RA). The growing understanding of the prolonged period before the first onset of symptoms of RA suggests that these environmental and genetic factors are likely acting to drive the development of RA-related autoimmunity long before the appearance of the first joint symptoms and clinical findings that are characteristic of RA. This article reviews these factors and interactions, especially those that have been investigated in a prospective fashion before the symptomatic onset of RA.

A spectrum of susceptibility to rheumatoid arthritis within HLA-DRB1: stratification by autoantibody status in a large UK population

Previously-proposed rheumatoid arthritis (RA) HLA-DRB1 susceptibility and protective models were compared, based on amino acids at positions 67-74 and autoantibody combinations. 3 657 RA patients and 1 357 controls were studied using logistic regression, with secondary stratification by anti-citrullinated peptide antibodies(ACPA) and rheumatoid factor(RF). Susceptibility models were based on previously defined HLA-DRB1 shared epitope(SE) subgroups. (70)DERAA(74), D(70) and I(67) protective models were compared, adjusting for HLA-DRB1 SE. A hierarchy of risk was observed within the HLA-DRB1 SE, particularly for ACPA-positive and RF-positive RA: HLA-DRB1(*)0401∼(*)0404>(*)0101∼(*)1001 ((*)0404>(*)0101: P=0.0003). HLA-DRB1(*)0401/(*)0404 compound heterozygosity conferred a risk similar to (*)0401 homozygosity (P=0.70). Protective effects of D(70) and I(67) were similar. Predictions of the D(70) model fitted the data better than those of the I(67) model. The protective effect of D(70) showed a gene-dose effect (OR 0.82, 95% CI 0.73-0.92, P=5.8 × 10(-4)), but was only seen in RA patients positive for RF or ACPA. HLA-DRB1 SE alleles were also associated with ACPA-negative, RF-positive RA (OR 1.42 (1.15-1.76), P=0.0012). In conclusion, HLA-DRB1 SE alleles show heterogeneity in RA susceptibility; their major effect appears to be mediated by ACPA positivity, but a significant association of HLA-DRB1 SE with RF-positive, ACPA-negative RA was also observed. D(70) specifically protected against antibody-positive RA.

Antibodies against cyclic citrullinated peptide don't decrease after 6 months of infliximab treatment in refractory rheumatoid arthritis

Anti-citrullinated peptide antibodies (ACPA) and the rheumatoid factor (RF) are well-established serological markers for rheumatoid arthritis (RA). ACPA are very useful in the diagnosis of RA, especially at the early stages of the disease when ACPA have a greater diagnostic value than RF. The aim of the study was to assess the influence of infliximab treatment on RF IgM and ACPA serum levels and RA activity during 6 months of treatment. Thirty-two patients with refractory RA were treated with infliximab during a 6-month period. At baseline, 3 and 6 months of treatment the patients were examined for the number swollen and tender joints out of 28 (SJC, TJC) and the visual analogue scale of arthritis activity according to the patient (VAS). Serum samples were tested for erythrocyte sedimentation rate (ESR), C-reactive protein level (CRP), ACPA and RF IgM. The disease activity score (DAS-28) parameter was also calculated at the same time. During the course of our study, we observed statistically significant improvement in ESR, CRP, TJC, SJC, VAS DAS-28, and RF IgM after 3 and 6 months of infliximab treatment when compared to the baseline, whereas the ACPA level remained unchanged after 3 and 6 months of treatment (P = 0.96 and P = 0.85). The changes in the ACPA level are not a factor for evaluation of successful infliximab treatment but the changes in RF IgM are. According to different behavior of these antibodies during infliximab treatment, we suggest that the roles of ACPA and RF in the pathogenesis of RA are different.

Contribution of HLA-DRB1*04 alleles and anti-cyclic citrullinated antibodies to development of resistance to disease-modifying antirheumatic drugs in early rheumatoid arthritis

This study was intended to evaluate HLA-DRB1 alleles and antibodies against anti-cyclic citrullinated peptides (anti-CCP Abs) for their value in predicting patient responses to treatment with disease-modifying antirheumatic drugs (DMARDs) in early rheumatoid arthritis (RA). The subjects were 124 Japanese patients who had received their first treatment with DMARDs, usually methotrexate, within 1 year of disease onset and who had been followed-up for 2 years subsequently. Approximately 40% of patients developed DMARD resistance and accordingly required anti-tumor necrosis factor α (TNFα) therapy during the 2-year period. DMARD resistance was strongly associated with the carriage of SE-positive HLA-DRB1*04 alleles, especially the *0405 allele (OR, 3.92; 95%CI, 1.83-8.41; p = 0.0003). In contrast, the SE-positive allele HLA-DRB1*0101 was less potent in contributing to DMARD resistance. The rate of anti-CCP Ab-positive patients was significantly higher in the DMARD-resistant group (OR, 6.62; 95%CI, 1.45-30.24; p = 0.008). Multivariate logistic regression analysis confirmed the strong association of DMARD resistance with the presence of SE-positive *04 alleles (OR, 2.89; 95%CI, 1.28-6.53; p = 0.011) and anti-CCP Abs (OR, 6.31; 95%CI, 1.23-32.34; p = 0.027), yielding an area under the receiver operating characteristic curve of 0.76 (95% CI, 0.68-0.84; p = 0.000). After stratification, the highest rate of DMARD resistance was observed in patients having both SE-positive *04 alleles and anti-CCP Abs. These observations show that the presence of SE-positive *04 alleles in combination with anti-CCP Abs is the strongest predictor for development of DMARD resistance and eventual need of anti-TNFα agents in patients with early RA.

Gene expression profiling in autoantibody-positive patients with arthralgia predicts development of arthritis

OBJECTIVE

To identify molecular features associated with the development of rheumatoid arthritis (RA), to understand the pathophysiology of preclinical development of RA, and to assign predictive biomarkers.

METHODS

The study group comprised 109 anti-citrullinated protein antibody (ACPA)- and/or rheumatoid factor-positive patients with arthralgia who did not have arthritis but were at risk of RA, and 25 patients with RA. The gene expression profiles of blood samples obtained from these patients were determined by DNA microarray analysis and quantitative polymerase chain reaction.

RESULTS

In 20 of the 109 patients with arthralgia who were at risk of RA, arthritis developed after a median of 7 months. Gene expression profiling of blood cells revealed heterogeneity among the at-risk patients, based on differential expression of immune-related genes. This report is the first to describe gene signatures relevant to the development of arthritis. Signatures significantly associated with arthritis development were involved in interferon (IFN)-mediated immunity, hematopoiesis, and chemokine/cytokine activity. Logistic regression analysis revealed that the odds ratio (OR) for developing arthritis within 12 months was 21.0 (95% confidence interval [95% CI] 2.8-156.1 [P = 0.003]) for the subgroup characterized by increased expression of genes involved in IFN-mediated immunity and/or cytokine/chemokine-activity. Genes involved in B cell immunology were associated with protection against progression to arthritis (OR 0.38, 95% CI 0.21-0.70 [P = 0.002]). These processes were reminiscent of those in patients with RA, implying that the preclinical phase of disease is associated with features of established disease.

CONCLUSION

The results of this study indicate that IFN-mediated immunity, hematopoiesis, and cell trafficking specify processes relevant to the progression of arthritis independent of ACPA positivity. These findings strongly suggest that certain gene signatures have value for predicting the progression to arthritis, which will pave the way to preventive medicine.