Gene-environment interaction between the DRB1 shared epitope and smoking in the risk of anti-citrullinated protein antibody-positive rheumatoid arthritis: all alleles are important

Targeting the vivid facets of apolipoproteins as a cardiovascular risk factor in rheumatoid arthritis

Mostly, cardiovascular diseases are blamed for casualties in rheumatoid arthritis (RA) patients. Customarily, dyslipidemia is probably the most prevalent underlying cause of untimely demise in people suffering from RA as it hastens the expansion of atherosclerosis. The engagement of inflammatory cytokines like tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6), etc., is crucial in the progression and proliferation of both RA and abnormal lipid parameters. Thus, lipid abnormalities should be monitored frequently in patients with both primary and advanced RA stages. An advanced lipid profile examination, i.e., direct role of apolipoproteins associated with various lipid molecules is a more dependable approach for better understanding of the disease and selecting suitable therapeutic targets. Therefore, studying their apolipoproteins is more relevant than assessing RA patients' altered lipid profile levels. Among the various apolipoprotein classes, Apo A1 and Apo B are primarily being focused. In addition, it also addresses how calculating Apo B:Apo A1 ratio can aid in analyzing the disease's risk. The marketed therapies available to control lipid abnormalities are associated with many other risk factors. Hence, directly targeting Apo A1 and Apo B would provide a better and safer option.

Periodontitis and rheumatoid arthritis-Global efforts to untangle two complex diseases

Understanding the impact of oral health on rheumatoid arthritis (RA) will inform how best to manage patients with both periodontitis and RA. This review seeks to provide an update on interventional and mechanistic investigations, including a brief summary of European Research programs investigating the link between periodontitis and RA. Recent clinical studies are described that evaluate how the treatment of one disease impacts on the other, as are studies in both humans and animal models that have sought to identify the potential mechanisms linking the two diseases.

Gene-respiratory disease interactions for rheumatoid arthritis risk

OBJECTIVE

We aimed to identify gene by respiratory tract disease interactions that increase RA risk.

METHODS

In this case-control study using the Mass General Brigham Biobank, we matched incident RA cases, confirmed by ACR/EULAR criteria, to four controls on age, sex, and electronic health record history. Genetic exposures included a validated overall genetic risk score (GRS) for RA, a Human Leukocyte Antigen (HLA) GRS for RA, and the MUC5B promoter variant, an established risk factor for RA-associated interstitial lung disease (ILD). Preceding respiratory tract diseases came from diagnosis codes (positive predictive value 86%). We estimated attributable proportions (AP) and multiplicative odds ratios (OR) with 95% confidence intervals (CI) for RA for each genetic and respiratory exposure using conditional logistic regression models, adjusting for potential confounders.

RESULTS

We identified 653 incident RA cases and 2,607 matched controls (mean 54 years, 76% female). The highest tertile of the overall GRS and the HLA GRS were both associated with increased RA risk (OR 2.28, 95% CI 1.89,2.74; OR 2.02, 95% CI 1.67-2.45). ILD and the HLA GRS exhibited a synergistic relationship for RA risk (OR for both exposures 4.30, 95% CI 1.28,14.38; AP 0.51, 95% CI-0.16,1.18). Asthma and the MUC5B promoter variant also exhibited a synergistic interaction for seropositive RA (OR for both exposures 2.58, 95% CI 1.10,6.07; AP 0.62, 95% CI 0.24,1.00).

CONCLUSION

ILD-HLA GRS and asthma-MUC5B promoter variant showed synergistic interactions for RA risk. Such interactions may prove useful for RA prevention and screening.

When Autoantibodies Are Missing: The Challenge of Seronegative Rheumatoid Arthritis

Seronegative rheumatoid arthritis (SNRA) is characterized by the absence of both rheumatoid factor (RF) and antibodies against the cyclic citrullinated protein (ACPA) in serum. However, the differences between the two forms of RA are more complex and have not yet been definitively characterized. Several lines of evidences support the idea that there are specific elements of the two forms, including genetic background, epidemiology, pathogenesis, severity of progression over time, and response to therapy. Clinical features that may differentiate SNRA from SPRA are also suggested by data obtained from classical radiology and newer imaging techniques. Although new evidence seems to provide additional help in differentiating the two forms of RA, their distinguishing features remain largely elusive. It should also be emphasized that the distinctive features of RA forms, if not properly recognized, can lead to the underdiagnosis of SNRA, potentially missing the period called the "window of opportunity" that is critical for early diagnosis, timely treatment, and better prognosis. This review aims to summarize the data provided in the scientific literature with the goal of helping clinicians diagnose SNRA as accurately as possible, with emphasis on the most recent findings available.

Vitamin D Levels Among Rheumatoid Arthritis Sudanese Patients: Prevalence and Correlation to Disease Activity - A Bicentric Study

Purpose

To evaluate vitamin D levels among adult Sudanese RA patients and identify its correlation with RA disease activity.

Patients and Methods

A bicentric cross-sectional analytical hospital-based study was performed in two Khartoum State Hospitals between October 2019 and January 2020, enrolling 90 Sudanese patients with RA. Serum vitamin D levels were measured with a standard reference level of 30ng/mL-100ng/mL. A detailed interview-based questionnaire was used to collect the patient's information, clinical data and lab results-disease activity was assessed via the DAS-28 score. The data was then analyzed using SPSS v-24.

Results

Vitamin D levels were low in 79 candidates (87.8%), 53 of which (67.1%) showed moderate insufficiency (10-30ng/mL), and 26 candidates (32.9%) had severe deficiency (less than 10 ng/mL). Regarding the disease activity, 57 participants (63.3%) had moderate disease activity (DAS-28=3.2-5.1), and 22 participants (24.4%) had high disease activity (DAS-28 >5.1). A significant negative correlation was reported between high DAS-28 scores and low vitamin D levels with p-value = <0.001 (95% CI: -0.8591 to 0.0015) and r = -0.44.

Conclusion

Most adult Sudanese rheumatoid arthritis patients showed low vitamin D levels (87.8%), which was also significantly correlated with increased disease activity (P-value <0.05). Moreover, the prevalence of low vitamin D levels was significantly higher than in numerous countries worldwide.

C-terminal citrullinated peptide alters antigen-specific APC:T cell interactions leading to breach of immune tolerance

In rheumatoid arthritis, the emergence of anti-citrullinated autoimmunity is associated with HLA-antigen-T cell receptor complexes. The precise mechanisms underpinning this breach of tolerance are not well understood. Porphyromonas gingivalis expresses an enzyme capable of non-endogenous C-terminal citrullination with potential to generate citrullinated autoantigens. Here we document how C-terminal citrullination of ovalbumin peptide^323-339 alters the interaction between antigen-presenting cells and OTII T cells to induce functional changes in responding T cells. These data reveal that C-terminal citrullination is sufficient to breach T cell peripheral tolerance in vivo and reveal the potential of C-terminal citrullination to lower the threshold for T cell activation. Finally, we demonstrate a role for the IL-2/STAT5/CD25 signalling axis in breach of tolerance. Together, our data identify a tractable mechanism and targetable pathways underpinning breach of tolerance in rheumatoid arthritis and provide new conceptual insight into the origins of anti-citrullinated autoimmunity.

Prevention of rheumatoid arthritis: A systematic literature review of preventive strategies in at-risk individuals

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune disease characterized by symmetrical peripheral polyarthritis in the hands and/or feet, leading to long-term disability if not treated effectively. RA is preceded by a preclinical phase, in which genetically predisposed individuals accumulate environmental risk factors, and during which autoimmunity develops, followed by the emergence of non-specific signs and symptoms before arthritis becomes manifest. Early treatment in at-risk individuals - i.e. before the disease is fully established - has the theoretical potential to delay or prevent disease onset, with a positive impact on both patients' life and society.

OBJECTIVES

We aimed to understand the feasibility of preventive treatment in at-risk individuals, taking into account recently performed studies and ongoing clinical trials, as well as patient perspectives.

METHODS

We performed a systematic literature review (SLR) on Medline and Embase, searching articles published between 2010 and 2021 with the following key-words: "Rheumatoid arthritis", "arthralgia", "pre-treatment" or "prevent".

RESULTS

Our SLR identified a total of 1821 articles. Articles were independently screened by two researchers. A total of 14 articles were included after screening, and an additional 8 reports were manually included. We identified ten relevant clinical trials performed in at-risk individuals, or in individuals with undifferentiated inflammatory arthritis. Although no treatment was shown to prevent RA onset, early treatment with rituximab and abatacept delayed onset of full-blown RA, and both conventional and biological disease-modifying anti-rheumatic drugs (DMARDs) decreased disease-related physical limitations and increased DAS28-defined remission, at least temporarily.

CONCLUSIONS

This SLR demonstrates that early treatment of at-risk individuals may be effective in delaying RA onset, thereby decreasing disease-related limitations in individuals in the pre-clinical phase of RA. Whether this may ultimately lead to prevention of RA remains to be determined.

Inhalant and Additional Mucosal-Related Environmental Risks for Rheumatoid Arthritis

Rheumatoid arthritis (RA) occurs as the result of a complex interplay of environmental factors in a genetically susceptible individual. There is considerable evidence that the lungs may serve as an initial site of tolerance loss in the generation of RA-related autoimmunity, and several environmental inhalant exposures and lung diseases have been associated with RA risk. There is additional evidence that immune and microbial dysregulation of other mucosal sites, including the oral and gastrointestinal mucosa, may contribute to the development of RA. Epidemiologic evidence linking mucosal exposures to various environmental insults as risk determinants in RA will be reviewed.

Bibliometric analysis of research relating to the use of herbal medicine for rheumatoid arthritis between 1991 to 2021

BACKGROUND

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease, which is well known for its poor symptoms, and the incidence is increasing worldwide. Although conventional medicines are practiced initially, patients often move or accompany to complementary and alternative medicines for better outcomes. Herbal medications, one of traditional medicinal approach, are widely used in clinical conditions. However, no research has broadly reviewed the current research trends regarding the scope of herbal medicines in RA. The aim of this study was to conduct a bibliometric analysis of applications of herbal medicine for RA from 1991 to the present.

METHODS

We retrieved literature on herbal medicine for RA from the Web of Science database from 1991 to 2021. The VOSviewer program was used to analyze keywords, authors, countries, and organizations through visual knowledge mapping to assess the research hotspots and trends.

RESULTS

A total of 516 articles were included in the analysis, which showed an increasing trend in the number of publications over time. Four clusters were identified from the keyword analysis: complementary and alternative medicine cluster, mechanism of the pain cluster, control for the pain cluster, and recent research trend cluster. People's Republic of China published 250 articles, which was the greatest number of publications, followed by the United States of America (82 articles) and South Korea (52 articles). Furthermore, Moudgil, KD of the University of Maryland published 15 articles about the mechanism of herbal medicine on autoimmune arthritis and their interaction with various drugs. Lu, AP of the Hong Kong Baptist University published 14 articles about herbal medicine interactions. On an institutional level, the China Academy of Chinese Medical Science published 33 articles, followed by the Hong Kong Baptist University and the University of Maryland with 27 and 20 articles, respectively. Clusters of organizations from the People's Republic of China and the United States of America revealed higher average citations for earlier average publication years.

CONCLUSIONS

This bibliometric study identified trends in herbal medicine for RA from 1991 to 2021, which may guide the hot topics and future directions in this research field.

Clinical Implications of Shared Epitope and Anti-citrullinated Peptide Antibody in Patients With Rheumatoid Arthritis

Objective

The shared epitope (SE) and anti-citrullinated peptide antibody (ACPA) are involved in the pathogenesis of rheumatoid arthritis (RA). This study evaluated the clinical implications of SE and ACPA in terms of disease manifestation and response to biologic disease modifying anti-rheumatic drugs (DMARDs).

Methods

Patients with identified human leukocyte antigen (HLA)-DRB1 alleles were included to compare the clinical characteristics and drug survival rate of tumor necrosis factor (TNF) inhibitors or abatacept based on the presence of SE and ACPA.

Results

Of the 533 patients with identified HLA-DRB1 alleles, 329 patients (61.7%) with SE alleles showed higher disease activity and erosive changes compared to patients without SE alleles. SE-positive patients were more likely to start biologic (b-) or targeted synthetic DMARDs (tsDMARDs) within the first 5 years (p=0.020). The presence of SE, smoking, dyslipidemia, and higher erythrocyte sedimentation rate were independently associated with the initiation of b- or tsDMARDs (p=0.016, 0.028, 0.031, and 0.001, respectively). The presence of SE and ACPA did not affect the drug survival rate of TNF inhibitors, whereas the abatacept retention rate was higher in ACPA-positive patients (p=0.024).

Conclusion

The presence of SE affected disease characteristics and prognosis in Korean patients with RA without a significant impact on drug survival rate of TNF inhibitors and abatacept. ACPA positivity was associated with abatacept drug retention, suggesting that abatacept may be helpful in ACPA-positive patients than in ACPA-negative patients.

Preclinical Autoimmune Disease: a Comparison of Rheumatoid Arthritis, Systemic Lupus Erythematosus, Multiple Sclerosis and Type 1 Diabetes

The preclinical phase of autoimmune disorders is characterized by an initial asymptomatic phase of varying length followed by nonspecific signs and symptoms. A variety of autoimmune and inflammatory manifestations can be present and tend to increase in the last months to years before a clinical diagnosis can be made. The phenotype of an autoimmune disease depends on the involved organs, the underlying genetic susceptibility and pathophysiological processes. There are different as well as shared genetic or environmental risk factors and pathophysiological mechanisms between separate diseases. To shed more light on this, in this narrative review we compare the preclinical disease course of four important autoimmune diseases with distinct phenotypes: rheumatoid arthritis (RA), Systemic Lupus Erythematosus (SLE), multiple sclerosis (MS) and type 1 diabetes (T1D). In general, we observed some notable similarities such as a North-South gradient of decreasing prevalence, a female preponderance (except for T1D), major genetic risk factors at the HLA level, partly overlapping cytokine profiles and lifestyle risk factors such as obesity, smoking and stress. The latter risk factors are known to produce a state of chronic systemic low grade inflammation. A central characteristic of all four diseases is an on average lengthy prodromal phase with no or minor symptoms which can last many years, suggesting a gradually evolving interaction between the genetic profile and the environment. Part of the abnormalities may be present in unaffected family members, and autoimmune diseases can also cluster in families. In conclusion, a promising strategy for prevention of autoimmune diseases might be to address adverse life style factors by public health measures at the population level.

Timing of sinusitis and other respiratory tract diseases and risk of rheumatoid arthritis

OBJECTIVE

To investigate the association between timing of respiratory tract diseases and risk of rheumatoid arthritis (RA).

METHODS

This case-control study using the Mass General Brigham Biobank matched incident RA cases, confirmed by ACR/EULAR criteria, with at least seven years preceding electronic health record (EHR) data to three controls on age, sex, and EHR history from RA diagnosis (index date). We ascertained timing (>0-5 years/>5-10 years/>10 years) of the first documented respiratory tract disease prior to index date using diagnosis codes. We estimated odds ratios (OR) with 95% confidence intervals (CI) for RA for each respiratory exposure using logistic regression models, adjusting for potential confounders. We also conducted a stratified analysis by serostatus and smoking.

RESULTS

We identified 625 incident RA cases (median 56 years, 75% female, 57% seropositive) and 1,875 controls. Acute sinusitis was associated with RA only in the >5 to 10 years before RA (OR 3.90, 95% CI:1.90,8.01). In contrast, pneumonia was associated with RA only in the >0 to 5 years before RA (OR 1.73, 95% CI:1.00,3.00), and chronic respiratory tract diseases only >10 years before RA (OR 1.43, 95% CI:1.00,2.05). All respiratory tract diseases tended to show a stronger association with seronegative RA than seropositive RA, although the interaction was statistically significant only for chronic sinusitis (p=0.04). Respiratory diseases showed a nonsignificantly stronger association among smokers than nonsmokers.

CONCLUSION

Sinusitis and other respiratory diseases are associated with increased risk of RA, especially 5 years before RA onset. RA may begin many years before clinical onset.

PADI4 Polymorphisms Confer Risk of Anti-CCP-Positive Rheumatoid Arthritis in Synergy With HLA-DRB1*04 and Smoking

Peptidylarginine deiminases (PADs) catalyze citrullination, a post-translational modification playing a pathogenic role in anti-citrullinated protein antibody (ACPA)-positive rheumatoid arthritis (RA). The interplay between single nucleotide polymorphisms (SNPs) in the PADI genes and known risk factors for ACPA-positive RA, including smoking, HLA-DR4 and -1, and the PTPN22 R620W polymorphism, was investigated. We typed four PADI2 SNPs, four PADI4 SNPs, and the PTPN22 R620W SNP in 445 Danish RA patients and 533 age-matched healthy controls, as well as in 200 North American RA patients and 100 age- and sex-matched controls. The HLA-DRB1 locus was typed in the Danish cohort. Logistic regression analyses, adjusted for age, sex, smoking status, and PTPN22 R620W, revealed increased risk of anti-CCP-positive RA in carriers of rs11203367(T) (OR: 1.22, p=0.03) and reduced risk in carriers of rs2240335(A) in PADI4 (OR: 0.82, p=0.04). rs74058715(T) in PADI4 conferred reduced risk of anti-CCP-negative RA (OR: 0.38, p=0.003). In HLA-DRB1*04-positive individuals, specifically, the risk of anti-CCP-positive RA was increased by carriage of PADI4 rs1748033(T) (OR: 1.54, p=0.007) and decreased by carriage of PADI4 rs74058715(T) (OR: 0.44, p=0.01), and we observed an interaction between these SNPs and HLA-DRB1*04 (p=0.004 and p=0.008, respectively) Thus, PADI4 polymorphisms associate with ACPA-positive RA, particularly in HLA-DRB1*04-positive individuals, and with ACPA-negative RA independently of HLA-DRB1*04.

Association of sinusitis and upper respiratory tract diseases with incident rheumatoid arthritis: A case-control study

OBJECTIVE

We aimed to determine whether specific respiratory tract diseases are associated with increased rheumatoid arthritis (RA) risk.

METHODS

This case-control study within the Mass General Brigham Biobank matched newly diagnosed RA cases to three controls on age, sex, and electronic health record history. We identified RA using a validated algorithm and confirmed by medical record review. Respiratory tract disease exposure required one inpatient or two outpatient codes at least two years before index date of RA clinical diagnosis or matched date. Logistic regression models calculated odds ratios (OR) for RA with 95% confidence intervals (CI), adjusting for confounders. We then stratified by serostatus ("seropositive" was positive rheumatoid factor and/or anti-citrullinated protein antibodies) and smoking.

RESULTS

We identified 741 RA cases and 2,223 controls (both median age 55, 76% female). Acute sinusitis (OR 1.61, 95% CI:1.05,2.45), chronic sinusitis (OR 2.16, 95% CI:1.39,3.35), and asthma (OR 1.39, 95% CI:1.03,1.87) were associated with increased risk of RA. Acute respiratory tract disease burden during the pre-index exposure period was also associated with increased RA risk (OR 1.30 per 10 codes, 95% CI:1.08,1.55). Acute pharyngitis was associated with seronegative (OR 1.68, 95% CI:1.02,2.74) but not seropositive RA; chronic rhinitis/pharyngitis was associated with seropositive (OR 2.46, 95% CI:1.01,5.99) but not seronegative RA. Respiratory tract diseases tended towards higher associations in smokers, especially >10 packyears (OR 1.52, 95% CI:1.02,2.27; p=0.10 for interaction).

CONCLUSION

Acute/chronic sinusitis and pharyngitis and acute respiratory burden increased RA risk. The mucosal paradigm of RA pathogenesis may involve the upper respiratory tract.

High Body Mass Index is Associated with Shorter Retention of Tumor Necrosis Factor-Alpha Blocker Treatment in Rheumatoid Arthritis

Purpose

To evaluate the association between body mass index (BMI) and tumor necrosis factor α (TNF-α) blockers retention in patients with rheumatoid arthritis (RA).

Patients and Methods

This prospective cohort study analyzed data about patients with RA who initiated TNF blockers from the Israeli registry of inflammatory diseases from 2011 to 2019. Patients were grouped by BMI: normal (BMI <24.9 kg/m2), overweight (BMI 25–29.9 kg/m2), obese (BMI 30–34.9 kg/m2) and morbid obese (BMI ≥35 kg/m2). Treatment cessation due to inefficacy was defined as an “event” and therapy with a drug above 3 months was defined as a “course.” Kaplan–Meier survival curve was used to describe drug survival. Event-free survival was calculated using Cox regression with a hazard ratio and confidence interval of 95%.

Results

The final analysis included 521 RA patients (80% females) treated with etanercept, infliximab, adalimumab or golimumab. Eight hundred and eighteen treatment initiations were included in the final analysis, 334 (41%) in the normal weight group, 261 (32%) in the overweight, 144 (17%) in the obese and 79 (10%) in the morbid obesity group. Three hundred and twenty-six (40%) treatment initiations were with etanercept, 215 (26%) with adalimumab 197 (24%) with infliximab, and 80 (10%) with golimumab. BMI was inversely associated with drug survival. Morbid obese patients were more likely to discontinue treatment compared with normal weight patients HR 2.28 (95% CI 1.67–3.10, p<0.01). This association remained significant for each drug type (except for golimumab) in a subgroup analysis. Adalimumab switch rate was higher compared to etanercept with HR =1.51 (95% CI 1.20–1.91, p<0.01), no other significant differences were noted between the other drugs.

Conclusion

Morbid obese RA patients have lower TNF-α blocker retention compared to normal weight patients.

Is seronegative rheumatoid arthritis true rheumatoid arthritis? A nationwide cohort study

OBJECTIVES

The classification of seronegative arthritides can be challenging. Our aim was to examine the incidence of SpA diagnosis among patients initially diagnosed as seronegative RA.

METHODS

Using nationwide Finnish registers from social insurance institutions, we identified all adult patients who were diagnosed with incident seronegative RA [International Classification of Diseases (ICD)-10 code M06] from 1 January 2000 to 31 December 2014. The patients whose diagnoses subsequently changed to the ICD-10 codes of SpA (M07, M45, M46, K50 and K51) were identified in the national care register, until 31 December 2016.

RESULTS

A total of 9784 adult seronegative RA patients were identified. Of these, 564 patients had their diagnosis subsequently changed to SpA: 275 (48.7%) patients with PsA, 245 (43.4%) patients with axial SpA and 44 (7.8%) patients with diagnoses related to IBD. The cumulative incidence of SpA diagnoses in 15 years was 10.4% (95% CI 8.9, 12.1) and 8.1% (95% CI 7.1, 9.3) in men and women, respectively.

CONCLUSION

This study calls for vigilance in seronegative RA patients, especially those with more atypical presentations, since the diagnosis could change. The possibility of SpA diagnosis should be considered and specifically looked for, as this could impact on management and response to treatment.

Association Between Baseline Anti-cyclic Citrullinated Peptide Antibodies and 6-Month Clinical Response Following Abatacept or TNF Inhibitor Treatment: A Real-World Analysis of Biologic-Experienced Patients with RA

INTRODUCTION

Anti-cyclic citrullinated peptide (anti-CCP) antibodies are associated with poor prognosis in patients with rheumatoid arthritis (RA). Previous data from randomized controlled trials and clinical practice have shown anti-CCP-positive (+) patients had a better response to treatment with abatacept or tumor necrosis factor inhibitor (TNFi) treatment than those who were anti-CCP negative. This study assessed the association between baseline anti-CCP2 [a surrogate for anti-citrullinated protein antibody (ACPA)] concentration and 6-month treatment responses to abatacept or TNFi in patients with RA.

METHODS

This real-world analysis included biologic-experienced patients from CERTAIN (Comparative Effectiveness Registry to study Therapies for Arthritis and Inflammatory CoNditions) who initiated abatacept or TNFi, had prior biologic disease-modifying drug exposure and baseline anti-CCP2 concentration/serostatus and serum samples (baseline and 6 months). Baseline demographics and disease characteristics were compared. Change from baseline at 6 months in Clinical Disease Activity Index (CDAI) score and patient-reported outcomes [PROs: pain, fatigue, patient global assessment (PtGA), modified Health Assessment Questionnaire (mHAQ) score], by baseline anti-CCP2 quartile and binary cut-off (> 10-250 and > 250 U/ml), were evaluated separately in the abatacept and TNFi groups using a linear regression model adjusted for age, sex, CDAI/PROs, comorbidity index, and methotrexate use.

RESULTS

Included were 138 abatacept and 137 TNFi initiators who were anti-CCP2+. At baseline, there were significant differences between anti-CCP2 quartiles and mean CDAI, swollen joint count 28, C-reactive protein (CRP), Disease Activity Score 28 (CRP), rheumatoid factor (RF), mHAQ and physician global assessment among abatacept initiators, and in mean RF, mHAQ, and PtGA among TNFi initiators. Among abatacept (but not TNFi) initiators, CDAI numerically improved (p = 0.208) and PROs significantly improved (p < 0.05) with increasing baseline anti-CCP2.

CONCLUSIONS

In patients treated with abatacept, not TNFi, higher anti-CCP2 concentrations at baseline were associated with numerically greater improvements in CDAI and significant improvements in PROs after 6 months.

CLINICAL TRIAL NUMBER

NCT01625650.

The pre-clinical phase of rheumatoid arthritis: From risk factors to prevention of arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease considered as a multistep process spanning from the interaction of genetic (e.g., shared epitope or non-HLA loci), environmental and behavioral risk factors (e.g., smoking) leading to breaking immune tolerance and autoimmune processes such as the production of autoantibodies (e.g., antibodies against citrullinated proteins ACPA or rheumatoid factors, RF), development of the first symptoms without clinical arthritis, and, finally, the manifestation of arthritis. Despite the typical joint involvement in established RA, the pathogenesis of the disease likely begins far from joint structures: in the lungs or periodontium in association with citrullination, intestinal microbiome, or adipose tissue, which supports normal findings in synovial tissue in ACPA+ patients with arthralgia. The presence of ACPA is detectable even years before the first manifestation of RA. The pre-clinical phase of RA is the period preceding clinically apparent RA with ACPA contributing to the symptoms without subclinical inflammation. While the combination of ACPA and RF increases the risk of progression to RA by up to 10 times, increasing numbers of novel autoantibodies are to be investigated to contribute to the increased risk and pathogenesis of RA. With growing knowledge about the course of RA, new aspiration emerges to cure and even prevent RA, shifting the "window of opportunity" to the pre-clinical phases of RA. The clinical definition of individuals at risk of developing RA (clinically suspect arthralgia, CSA) makes it possible to unify these at-risk individuals' clinical characteristics for "preventive" treatment in ongoing clinical trials using mostly biological or conventional synthetic disease-modifying drugs. However, the combination of symptoms, laboratory, and imaging biomarkers may be the best approach to select the correct target at-risk population. The current review aims to explore different phases of RA and discuss the potential of (non)pharmacological intervention aiming to prevent RA.

Interactions Between Genome-Wide Genetic Factors and Smoking Influencing Risk of Systemic Lupus Erythematosus

OBJECTIVE

To identify interactions between genetic factors and current or recent smoking in relation to risk of developing systemic lupus erythematosus (SLE).

METHODS

For the study, 673 patients with SLE (diagnosed according to the American College of Rheumatology 1997 updated classification criteria) were matched by age, sex, and race (first 3 genetic principal components) to 3,272 control subjects without a history of connective tissue disease. Smoking status was classified as current smoking/having recently quit smoking within 4 years before diagnosis (or matched index date for controls) versus distant past/never smoking. In total, 86 single-nucleotide polymorphisms and 10 classic HLA alleles previously associated with SLE were included in a weighted genetic risk score (wGRS), with scores dichotomized as either low or high based on the median value in control subjects (low wGRS being defined as less than or equal to the control median; high wGRS being defined as greater than the control median). Conditional logistic regression models were used to estimate both the risk of SLE and risk of anti-double-stranded DNA autoantibody-positive (dsDNA+) SLE. Additive interactions were assessed using the attributable proportion (AP) due to interaction, and multiplicative interactions were assessed using a chi-square test (with 1 degree of freedom) for the wGRS and for individual risk alleles. Separate repeated analyses were carried out among subjects of European ancestry only.

RESULTS

The mean ± SD age of the SLE patients at the time of diagnosis was 36.4 ± 15.3 years. Among the 673 SLE patients included, 92.3% were female and 59.3% were dsDNA+. Ethnic distributions were as follows: 75.6% of European ancestry, 4.5% of Asian ancestry, 11.7% of African ancestry, and 8.2% classified as other ancestry. A high wGRS (odds ratio [OR] 2.0, P = 1.0 × 10^-51 versus low wGRS) and a status of current/recent smoking (OR 1.5, P = 0.0003 versus distant past/never smoking) were strongly associated with SLE risk, with significant additive interaction (AP 0.33, P = 0.0012), and associations with the risk of anti-dsDNA+ SLE were even stronger. No significant multiplicative interactions with the total wGRS (P = 0.58) or with the HLA-only wGRS (P = 0.06) were found. Findings were similar in analyses restricted to only subjects of European ancestry.

CONCLUSION

The strong additive interaction between an updated SLE genetic risk score and current/recent smoking suggests that smoking may influence specific genes in the pathogenesis of SLE.

Sex-Based Differences in Monocytic Lineage Cells Contribute to More Severe Collagen-Induced Arthritis in Female Rats Compared with Male Rats

Monocytes' plasticity has an important role in the development of rheumatoid arthritis (RA), an autoimmune disease exhibiting greater prevalence in women. Contribution of this phenomenon to sex bias in RA severity was investigated in rat collagen-induced arthritis (CIA) model of RA. The greater severity of CIA in females (exhibiting signs of bone resorption) was accompanied by the higher blood level of advanced oxidation protein products and a more pro-oxidant profile. Consistently, in females, the greater density of giant multinuclear cells (monocytes/macrophages and osteoclasts) in inflamed joint tissue was found. This correlated with the higher frequencies of CCR2- and CX3CR1- expressing cells (precursors of inflammatory monocytes/macrophages and osteoclasts) among CD11b+ splenocytes. This in conjunction with the enhanced migratory capacity of CD11b+ monocytic cells in females compared with males could be linked with the higher frequencies of CCR2+CX3CR1-CD43^lowCD11b+ and CCR2-CX3CR1+CD43^hiCD11b+ cells (corresponding to "classical" and "non-classical" monocytes, respectively) and the greater density of CD68+ cells (monocytes/macrophages and osteoclast precursors/osteoclasts) in blood and inflamed paws from female rats, respectively. Consistently, the higher levels of GM-CSF, TNF-α and IL-6, IL-1β (driving Th17 cell differentiation), and IL-17 followed by the lower level of IL-10 were measured in inflamed paw cultures from female compared with male rats. To the greater IL-17 production (associated with enhanced monocyte immigration and differentiation into osteoclasts) most likely contributed augmented Th17 cell generation in the lymph nodes draining arthritic joints from female compared with male rats. Overall, the study suggests the sex-specific contribution of monocytic lineage cells to CIA, and possibly RA development.

Long-term exposure to a mixture of industrial SO2, NO2, and PM2.5 and anti-citrullinated protein antibody positivity

BACKGROUND

Studies of associations between industrial air emissions and rheumatic diseases, or diseases-related serological biomarkers, are few. Moreover, previous evaluations typically studied individual (not mixed) emissions. We investigated associations between individual and combined exposures to industrial sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and fine particles matter (PM_2.5) on anti-citrullinated protein antibodies (ACPA), a characteristic biomarker for rheumatoid arthritis (RA).

METHODS

Serum ACPA was determined for 7600 randomly selected CARTaGENE general population subjects in Quebec, Canada. Industrial SO₂, NO₂, and PM_2.5 concentrations, estimated by the California Puff (CALPUFF) atmospheric dispersion model, were assigned based on residential postal codes at the time of sera collection. Single-exposure logistic regressions were performed for ACPA positivity defined by 20 U/ml, 40 U/ml, and 60 U/ml thresholds, adjusting for age, sex, French Canadian origin, smoking, and family income. Associations between regional overall PM_2.5 exposure and ACPA positivity were also investigated. The associations between the combined three industrial exposures and the ACPA positivity were assessed by weighted quantile sum (WQS) regressions.

RESULTS

Significant associations between individual industrial exposures and ACPA positivity defined by the 20 U/ml threshold were seen with single-exposure logistic regression models, for industrial emissions of PM_2.5 (odds ratio, OR = 1.19, 95% confidence intervals, CI: 1.04-1.36) and SO₂ (OR = 1.03, 95% CI: 1.00-1.06), without clear associations for NO₂ (OR = 1.01, 95% CI: 0.86-1.17). Similar findings were seen for the 40 U/ml threshold, although at 60 U/ml, the results were very imprecise. The WQS model demonstrated a positive relationship between combined industrial exposures and ACPA positivity (OR = 1.36, 95% CI: 1.10-1.69 at 20 U/ml) and suggested that industrial PM_2.5 may have a closer association with ACPA positivity than the other exposures. Again, similar findings were seen with the 40 U/ml threshold, though 60 U/ml results were imprecise. No clear association between ACPA and regional overall PM_2.5 exposure was seen.

CONCLUSIONS

We noted positive associations between ACPA and industrial emissions of PM_2.5 and SO₂. Industrial PM_2.5 exposure may play a particularly important role in this regard.

The Impact of Cigarette Smoking on Risk of Rheumatoid Arthritis: A Narrative Review

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and subsequent proliferation of synovial tissues, which eventually leads to cartilage and bone destruction without effective treatments. Anti-citrullinated cyclic peptide/protein antibody (ACPA) and rheumatoid factor (RF) are two main characteristic autoantibodies found in RA patients and are associated with unfavorable disease outcomes. Although etiologies and causes of the disease have not been fully clarified yet, it is likely that interactive contributions of genetic and environmental factors play a main role in RA pathology. Previous works have demonstrated several genetic and environmental factors as risks of RA development and/or autoantibody productions. Among these, cigarette smoking and HLA-DRB1 are the well-established environmental and genetic risks, respectively. In this narrative review, we provide a recent update on genetic contributions to RA and the environmental risks of RA with a special focus on cigarette smoking and its impacts on RA pathology. We also describe gene–environmental interaction in RA pathogenesis with an emphasis on cigarette smoking and HLA-DRB1.

Exposure to ambient air pollution and autoantibody status in rheumatoid arthritis

OBJECTIVE

To evaluate the relationship between air pollutant (AP) exposure and rheumatoid arthritis (RA) autoantibody status METHODS: We performed a cross sectional study utilizing enrollment data from participants in the Veterans Affairs rheumatoid arthritis registry. HLA-DRB1 shared epitope (SE), smoking, rheumatoid factor (RF), and anti-cyclic citrullinated peptide antibody (ACPA) status were collected. Mean exposure levels were obtained for AP (NO₂, SO₂, particulate matter [PM_2.5, PM₁₀], and ozone) from air quality monitoring stations at patients' residential zip codes in the year prior to enrollment. Multivariable logistic and ordinary least squares regression models were used to determine independent associations of AP with RA seropositivity and autoantibody concentration.

RESULTS

The cohort included 557 veterans (90% male, 76% Caucasian), with mean age of 70 years and mean disease duration of 13 years. The majority were HLA-DRB1 SE, RF, and ACPA positive (73%, 79%, and 76%, respectively). In univariate models, PM_2.5 exposure was associated with higher ACPA concentration (p = 0.009). Similarly, in multivariable regression models, PM_2.5 exposure was independently associated with higher ACPA concentration (p = 0.037). Current smoking independently predicted RF and ACPA positivity and titers, while HLA-DRB1 SE alleles were associated with RF positivity and ACPA positivity and titers.

CONCLUSIONS

In an elderly cohort of RA patients, fine particulate matter (PM_2.5) exposure independently predicted higher ACPA concentration. Further study of fine particulate matter in the pathogenesis of RA is warranted. Key Points • A study that integrates both genetic and environmental exposure data, relative to RA autoantibody status. • Of different air pollutants measures, exposure to fine particulate matter (PM_2.5) appears to be most closely linked to ACPA titers.

Mechanisms of lung disease development in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disorder that causes joint inflammation and damage. Extra-articular manifestations occur in many patients and can include lung involvement in the form of airway or parenchymal inflammation and fibrosis. Although the pathophysiology of articular RA has been extensively investigated, the mechanisms causing airway and parenchymal lung disease are not well defined. Infections, cigarette-smoking, mucosal dysbiosis, host genetics and premature senescence are all potentially important contributors to the development of lung disease in patients with RA. RA-associated lung disease (which can predate the onset of articular disease by many years) probably originates from chronic airway and alveolar epithelial injury that occurs in an individual with a genetic background that permits the development of autoimmunity, leading to chronic inflammation and subsequent airway and lung parenchymal remodelling and fibrosis. Further investigations into the specific mechanisms by which lung disease develops in RA will be crucial for the development of effective therapies. Identifying mechanisms by which environmental and host factors cooperate in the induction of autoimmunity in the lung might also help to establish the order of early events in RA.

Helminths-based bi-functional molecule, tuftsin-phosphorylcholine (TPC), ameliorates an established murine arthritis

A novel small molecule named tuftsin-phosphorylcholine (TPC), which is linked to the biological activity of helminths, was constructed. The current study address the effect of TPC treatment in established collagen-induced arthritis (CIA) mice and propose TPC bi-functional activity. TPC treatment was initiated when clinical score was 2 to 4. Arthritis scores in TPC treated mice were lower compared to mice treated with vehicle (P < 0.001). Joint staining showed normal joint structure in TPC-treated mice compared to control groups treated with phosphate buffered saline (PBS), phosphorylcholine, or tuftsin, which exhibited severely inflamed joints. TPC enhanced anti-inflammatory response due to increased IL-10 secretion, and reduced pro-inflammatory cytokine secretion (IL-1-β, IL-6, TNF-αP < 0.001). Furthermore, TPC therapy increased expansion of CD4⁺CD25⁺FOXP3⁺T regulatory cells and IL-10⁺CD5⁺CD1d⁺B regulatory cells. We propose that the immunomodulatory activity of TPC can be a result of a bi-specific activity of TPC: (a) The tuftsin part of the TPC shifts RAW macrophage cells from pro-inflammatory macrophages M1 to anti-inflammatory M2-secreting IL-10 (P < 0.001) through neuropilin-1 and (b) TPC significantly reduce mouse TLR4 expression via NFkB pathway by HEK^TM cells (P < 0.02) via the phosphorylcholine site of the molecule. Our results indicate that TPC, significantly ameliorated established CIA by its immunomodulatory activity. These data could lead to a novel self bi-functional small molecule for treating patients with progressive RA.

Human Leukocyte Antigen-Disease Associations in Rheumatoid Arthritis

The cause and pathogenesis of rheumatoid arthritis (RA) are influenced by environmental and genetic risk factors. Shared epitope-coding human leukocyte antigen (HLA)-DRB1 alleles increase RA risk and severity; however, the underlying mechanisms of action remain unclear. In contrast, several other DRB1 alleles protect against RA. Additionally, genome-wide association studies suggest that RA associates with other, HLA and non-HLA, genes; but the relative contributions of such risk loci to RA are incompletely understood. Future research challenges include integrating the epidemiologic and genomic data into validated arthritogenic pathways and determining the mechanisms of interaction between RA risk genes and environmental influences.

Gene and Protein Expression Profiles in a Mouse Model of Collagen-Induced Arthritis

The risk of rheumatoid arthritis (RA), an autoimmune disease, in the elderly population increases along with that of atherosclerosis, cardiovascular disease, type 2 diabetes, and Alzheimer's disease. Identifying specific biomarkers for RA can clarify the underlying molecular mechanisms and can aid diagnosis and patient care. To this end, the present study investigated the genes and proteins that are differentially expressed in RA using a mouse collagen-induced arthritis (CIA) model. We performed gene microarray and proteome array analyses using blood samples from the mice and found that 50 genes and 24 proteins were upregulated and 48 genes were downregulated by more than 2-fold in the CIA model relative to the control. The gene microarray and proteome array results were validated by evaluating the expression levels of select genes and proteins by real-time PCR and western blotting, respectively. We found that the level of integrin α2, which has not been previously reported as a biomarker of RA, was significantly increased in CIA mice as compared to controls. These findings provide a set of novel biomarkers that can be useful for diagnosing and evaluating the progression of RA.

Spectrum of orocutaneous disease associations: Immune-mediated conditions

There are a number of diseases that manifest both on the skin and the oral mucosa, and therefore the importance for dermatologists in clinical practice to be aware of these associations is paramount. In the following continuing medical education series, we outline orocutaneous disease associations with both immunologic and inflammatory etiologies.

Immunopathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most common inflammatory arthropathy. The majority of evidence, derived from genetics, tissue analyses, models, and clinical studies, points to an immune-mediated etiology associated with stromal tissue dysregulation that together propogate chronic inflammation and articular destruction. A pre-RA phase lasting months to years may be characterized by the presence of circulating autoantibodies, increasing concentration and range of inflammatory cytokines and chemokines, and altered metabolism. Clinical disease onset comprises synovitis and systemic comorbidities affecting the vasculature, metabolism, and bone. Targeted immune therapeutics and aggressive treatment strategies have substantially improved clinical outcomes and informed pathogenetic understanding, but no cure as yet exists. Herein we review recent data that support intriguing models of disease pathogenesis. They allude to the possibility of restoration of immunologic homeostasis and thus a state of tolerance associated with drug-free remission. This target represents a bold vision for the future of RA therapeutics.

The effect of rheumatoid arthritis-associated autoantibodies on the incidence of cardiovascular events in a large inception cohort of early inflammatory arthritis

Objective

. RA is associated with an increased risk of cardiovascular events (CVEs). The objective was to estimate independent effects of RA autoantibodies on the incident CVEs in patients with early RA.

Methods

Patients were enrolled in the Canadian Early Inflammatory Arthritis Cohort, a prospective multicentre inception cohort. Incident CVEs, including acute coronary syndromes and cerebrovascular events, were self-reported by the patient and partially validated by medical chart review. Seropositive status was defined as either RF or ACPA positive. Multivariable Cox proportional hazards survival analysis was used to estimate the effects of seropositive status on incident CVEs, controlling for RA clinical variables and traditional cardiovascular risk factors.

Results

. A total of 2626 patients were included: the mean symptom duration at diagnosis was 6.3 months ( s . d . 4.6), the mean age was 53 years ( s . d . 15), 72% were female and 86% met classification criteria for RA. Forty-six incident CVEs occurred over 6483 person-years [incidence rate 7.1/1000 person-years (95% confidence interval 5.3, 9.4)]. The CVE rate did not differ in seropositive vs seronegative subjects and seropositivity was not associated with incident CVEs in multivariable Cox regression models. Baseline covariates independently associated with incident CVEs were older age, a history of hypertension and a longer duration of RA symptoms prior to diagnosis.

Conclusion

The rate of CVEs early in the course of inflammatory arthritis was low; however, delays in the diagnosis of arthritis increased the rate of CVEs. Hypertension was the strongest independent risk factor for CVEs. Results support early aggressive management of RA disease activity and co-morbidities to prevent severe complications.

Identification of IRX1 as a Risk Locus for Rheumatoid Factor Positivity in Rheumatoid Arthritis in a Genome-Wide Association Study

OBJECTIVE

Rheumatoid factor (RF) is a well-established diagnostic and prognostic biomarker in rheumatoid arthritis (RA). However, ∼20% of RA patients are negative for this anti-IgG antibody. To date, only variation at the HLA-DRB1 gene has been associated with the presence of RF. This study was undertaken to identify additional genetic variants associated with RF positivity.

METHODS

A genome-wide association study (GWAS) for RF positivity was performed using an Illumina Quad610 genotyping platform. A total of 937 RF-positive and 323 RF-negative RA patients were genotyped for >550,000 single-nucleotide polymorphisms (SNPs). Association testing was performed using an allelic chi-square test implemented in Plink software. An independent cohort of 472 RF-positive and 190 RF-negative RA patients was used to validate the most significant findings.

RESULTS

In the discovery stage, a SNP in the IRX1 locus on chromosome 5p15.3 (SNP rs1502644) showed a genome-wide significant association with RF positivity (P = 4.13 × 10(-8) , odds ratio [OR] 0.37 [95% confidence interval (95% CI) 0.26-0.53]). In the validation stage, the association of IRX1 with RF was replicated in an independent group of RA patients (P = 0.034, OR 0.58 [95% CI 0.35-0.97] and combined P = 1.14 × 10(-8) , OR 0.43 [95% CI 0.32-0.58]).

CONCLUSION

To our knowledge, this is the first GWAS of RF positivity in RA. Variation at the IRX1 locus on chromosome 5p15.3 is associated with the presence of RF. Our findings indicate that IRX1 and HLA-DRB1 are the strongest genetic factors for RF production in RA.

Incidence of Chronic Persistent Rheumatoid Arthritis and the Impact of Smoking: A Historical Twin Cohort Study

OBJECTIVE

To assess the incidence of chronic persistent rheumatoid arthritis (RA) in a population-based cohort of twins and to determine the impact of smoking.

METHODS

In a historical cohort study on twins born in 1920 to 1982, we identified 157 cases of RA among 45,280 responders (response rate 80%). Information on smoking was obtained by questionnaire and interview. A mixed-effects Poisson regression model was used to estimate incidence rate ratios with age, sex, smoking duration, and smoking intensity as covariates. We used the SplitLexis procedure in the Epi R package to study a possible effect of period or cohort in addition to age on the variation of the incidence.

RESULTS

The annual incidence of chronic persistent RA was 18.8 per 100,000 person-years, ages 15-73 years (females 25.2, males 12.0), increasing with age to a maximum at age 60 years in females and age 70 years in males. The incidence rate ratio among ever-smoking patients was 1.96 (95% confidence interval [95% CI] 1.43-3.76), 1.93 (95% CI 1.00-3.7) after 30 pack-years, and 1.034 (P < 0.001) per year of smoking, implying a doubling of risk after 20 years regardless of sex and smoking intensity. We did not detect significant period or cohort effects.

CONCLUSION

The incidence of chronic persistent RA is lower than the incidence figures reported in inception cohorts. Smoking duration, but not intensity, doubled the risk of RA after 20 years of smoking in both sexes.

DNA methylation mediates genotype and smoking interaction in the development of anti-citrullinated peptide antibody-positive rheumatoid arthritis

BACKGROUND

Multiple factors, including interactions between genetic and environmental risks, are important in susceptibility to rheumatoid arthritis (RA). However, the underlying mechanism is not fully understood. This study was undertaken to evaluate whether DNA methylation can mediate the interaction between genotype and smoking in the development of anti-citrullinated peptide antibody (ACPA)-positive RA.

METHODS

We investigated the gene-smoking interactions in DNA methylation using 393 individuals from the Epidemiological Investigation of Rheumatoid Arthritis (EIRA). The interaction between rs6933349 and smoking in the risk of developing ACPA-positive RA was further evaluated in a larger portion of the EIRA (1119 controls and 944 ACPA-positive patients with RA), and in the Malaysian Epidemiological Investigation of Rheumatoid Arthritis (MyEIRA) (1556 controls and 792 ACPA-positive patients with RA). Finally, mediation analysis was performed to investigate whether DNA methylation of cg21325723 mediates this gene-environment interaction on the risk of developing of ACPA-positive RA.

RESULTS

We identified and replicated one significant gene-environment interaction between rs6933349 and smoking in DNA methylation of cg21325723. This gene-smoking interaction is a novel interaction in the risk of developing ACPA-positive in both Caucasian (multiplicative P value = 0.056; additive P value = 0.016) and Asian populations (multiplicative P value = 0.035; additive P value = 0.00027), and it is mediated through DNA methylation of cg21325723.

CONCLUSIONS

We showed that DNA methylation of cg21325723 can mediate the gene-environment interaction between rs6933349 and smoking, impacting the risk of developing ACPA-positive RA, thus being a potential regulator that integrates both internal genetic and external environmental risk factors.

Anticollagen type II antibodies are associated with an acute onset rheumatoid arthritis phenotype and prognosticate lower degree of inflammation during 5 years follow-up

OBJECTIVE

Antifibrillar collagen type II (anti-CII) antibody-positive patients with rheumatoid arthritis (RA) have early but not late signs of increased inflammation and joint erosions. We wanted to replicate this in a large RA cohort, and to relate to human leukocyte antigen (HLA)-DRB1* alleles.

METHODS

Anti-CII and anti-cyclic citrullinated peptide (CCP)2 were measured at baseline in 773 patients with RA from the Swedish Epidemiological Investigation in Rheumatoid Arthritis (EIRA) study with clinical follow-up data from the Swedish Rheumatology Quality Register (SRQ) registry, and 1476 with HLA-DRB1* information. Comparisons were done concerning C reactive protein (CRP), erythrocyte sedimentation rate (ESR), tender joint count (TJC), swollen joint count (SJC), Disease Activity Score encompassing 28 joints based on ESR (DAS28), DAS28CRP, pain-Visual Analogue Scale (VAS), global-VAS and Health Assessment Questionnaire Score (HAQ) at eight occasions during 5 years, and association with HLA-DRB1* alleles.

RESULTS

Anti-CII associated with elevated CRP, ESR, SJC, DAS28 and DAS28CRP at diagnosis and up to 6 months, whereas anti-CCP2 associated with SJC and DAS28 from 6 months to 5 years, but not earlier. The anti-CII-associated phenotype was strong, and predominated in anti-CII/anti-CCP2 double-positive patients. Anti-CII was associated with improvements in CRP, ESR, SJC, TJC and DAS28, whereas anti-CCP2 was associated with deteriorations in SJC and DAS28 over time. Anti-CII-positive patients achieved European League Against Rheumatism good or moderate response more often than negative patients. Anti-CII was positively associated with HLA-DRB1*01 and HLA-DRB1*03, with significant interaction, and double-positive individuals had >14 times higher mean anti-CII levels than HLA double negatives. Whereas smoking was associated with elevated anti-CCP2 levels, smokers had lower anti-CII levels.

CONCLUSIONS

Anti-CII seropositive RA represents a distinct phenotype, in many respects representing the converse to the clinical, genetic and smoking associations described for anticitrullinated protein peptide autoantibodies. Although not diagnostically useful, early anti-CII determinations predict favourable inflammatory outcome in RA.

Experimental silicosis does not aggravate collagen-induced arthritis in mice

Objectives

To investigate the effect of chronic lung inflammation on the incidence and severity of collagen-induced arthritis in mice.

Methods

Chronic lung inflammation in the form of silicosis was induced via intranasal application of silica particles. Immunization with collagen Type II commenced one week later and mice were sacrificed six weeks after booster immunization. Thereafter, silicosis was confirmed via flow cytometry and arthritis was evaluated performing knee and paw histology.

Results

Pronounced lung inflammation in the silica-treated compared to PBS-treated control mice was demonstrated by significantly elevated broncho-alveolar lavage (BAL) cell count, attributable to increased numbers of macrophages and granulocytes. Inflammation in the lungs was not associated with elevated PAD2 and PAD4 expression, yet silica treated animals had significantly higher aCCP serum titers. However, lung inflammation did not lead to an increase in the incidence of arthritis, nor did it exacerbate the macroscopic or histologic joint scores.

Conclusions

Chronic lung inflammation resulting from silicosis does not aggravate collagen-induced arthritis in mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12952-017-0071-6) contains supplementary material, which is available to authorized users.

Immune Mechanisms and Novel Targets in Rheumatoid Arthritis

Significant progress has been made in understanding the pathophysiology of rheumatoid arthritis. It is widely recognized that early institution of treatment is one of the best predictive factors for response to therapy. Several novel approaches are currently being investigated and several novel biologics are in various stages of development. With advances in the fields of proteomics, genomics, and metabolomics, specific phenotypes of the disease can be better identified and specific therapies for particular phases of the disease and specific patients will allow for improved control of this condition.

TMEM187-IRAK1 Polymorphisms Associated with Rheumatoid Arthritis Susceptibility in Tunisian and French Female Populations: Influence of Geographic Origin

Polymorphisms have been identified in the Xq28 locus as risk loci for rheumatoid arthritis (RA). Here, we investigated the association between three polymorphisms in the Xq28 region containing TMEM187 and IRAK1 (rs13397, rs1059703, and rs1059702) in two unstudied populations: Tunisian and French. The rs13397 G and rs1059703 T major alleles were significantly increased in RA patients (n = 408) compared with age-matched controls (n = 471) in both Tunisian and French women. These results were confirmed by a meta-analysis replication study including two independent Greek and Korean cohorts. The rs1059702 C major allele was significantly associated with RA, only with French women. In the French population, the GTC haplotype displayed a protective effect against RA, while the ATC, GCC, and GTT haplotypes conferred significant risk for RA. No association for these haplotypes was found in the Tunisian population. Our results replicated for the first time the association of the three Xq28 polymorphisms with RA risk in Tunisian and French populations and suggested that RA susceptibility is associated with TMEM187-IRAK1 polymorphisms in women. Our data further support the involvement of X chromosome in RA susceptibility and evidence ethnicities differences that might be explained by differences in the frequencies of SE HLA-DRB1 alleles between both populations.

Differences in the Spectrum of Anti-Citrullinated Protein Antibody Fine Specificities Between Malaysian and Swedish Patients With Rheumatoid Arthritis: Implications for Disease Pathogenesis

Objective

Antibodies to the citrullinated protein antigens (ACPAs) are important in the diagnosis and pathogenesis of rheumatoid arthritis (RA). However, the prevalence of ACPAs with different fine specificities in different populations is unclear. This study sought to examine the fine specificity of the antibody responses toward citrullinated proteins in RA patients from Malaysia, an area where genetic and environmental determinants of RA are different from those in more frequently studied cohorts of Caucasian subjects.

Methods

A multiplex analytic microarray system was used to analyze the occurrence of antibodies to 10 different citrullinated peptides (filaggrin [fil307–324], vimentin [Vim2–17, Vim60–75], fibrinogen [Fibα563–583, Fibα580–600, Fibβ36–52, Fibβ62–81a, Fibβ62–81b], enolase [Eno5–21], and type II collagen [CitCII355–378]) in serum samples from 4,089 RA patients (1,231 Malaysian and 2,858 Swedish) and 827 healthy control subjects (249 Malaysian and 578 Swedish). The positive reaction threshold for each peptide was set separately for each population based on a specificity of 98%.

Results

Distinct differences in the frequencies of 5 ACPA fine specificities (Vim60–75, Vim2–17, Fibβ62–81b, Eno5–21, and CitCII355–378) were found between the Malaysian and Swedish RA populations, despite a nearly identical percentage of patients in each population who were positive for anti–cyclic citrullinated peptide 2 antibodies. In Malaysian RA patients compared with Swedish RA patients, the frequencies of antibodies to Vim60–75 (54% versus 44%, corrected P [P_corr] = 1.06 × 10⁻⁸) and CitCII355–378 (17% versus 13%, P_corr = 0.02) were significantly higher, while the frequencies of antibodies to Vim2–17 (25% versus 32%, P_corr = 1.91 × 10⁻⁴), Fibβ62–81b (15% versus 30%, P_corr = 2.47 × 10⁻²²), and Eno5–21 (23% versus 50%, P_corr = 3.64 × 10⁻⁵⁷) were significantly lower.

Conclusion

Serum ACPA fine specificities differ between RA patients in different populations, although the total proportions of individuals positive for ACPAs are similar. Differing patterns of ACPA fine specificity could be attributed to variations in genetic and/or environmental factors.

Bone loss and aggravated autoimmune arthritis in HLA-DRβ1-bearing humanized mice following oral challenge with Porphyromonas gingivalis

Background

The linkage between periodontal disease and rheumatoid arthritis is well established. Commonalities among the two are that both are chronic inflammatory diseases characterized by bone loss, an association with the shared epitope susceptibility allele, and anti-citrullinated protein antibodies.

Methods

To explore immune mechanisms that may connect the two seemingly disparate disorders, we measured host immune responses including T-cell phenotype and anti-citrullinated protein antibody production in human leukocyte antigen (HLA)-DR1 humanized C57BL/6 mice following exposure to the Gram-negative anaerobic periodontal disease pathogen Porphyromonas gingivalis. We measured autoimmune arthritis disease expression in mice exposed to P. gingivalis, and also in arthritis-resistant mice by flow cytometry and multiplex cytokine-linked and enzyme-linked immunosorbent assays. We also measured femoral bone density by microcomputed tomography and systemic cytokine production.

Results

Exposure of the gingiva of DR1 mice to P. gingivalis results in a transient increase in the percentage of Th17 cells, both in peripheral blood and cervical lymph nodes, a burst of systemic cytokine activity, a loss in femoral bone density, and the generation of anti-citrullinated protein antibodies. Importantly, these antibodies are not produced in response to P. gingivalis treatment of wild-type C57BL/6 mice, and P. gingivalis exposure triggered expression of arthritis in arthritis-resistant mice.

Conclusions

Exposure of gingival tissues to P. gingivalis has systemic effects that can result in disease pathology in tissues that are spatially removed from the initial site of infection, providing evidence for systemic effects of this periodontal pathogen. The elicitation of anti-citrullinated protein antibodies in an HLA-DR1-restricted fashion by mice exposed to P. gingivalis provides support for the role of the shared epitope in both periodontal disease and rheumatoid arthritis. The ability of P. gingivalis to induce disease expression in arthritis-resistant mice provides support for the idea that periodontal infection may be able to trigger autoimmunity if other disease-eliciting factors are already present.

The role for neutrophil extracellular traps in cystic fibrosis autoimmunity

While respiratory failure in cystic fibrosis (CF) frequently associates with chronic infection by Pseudomonas aeruginosa, no single factor predicts the extent of lung damage in CF. To elucidate other causes, we studied the autoantibody profile in CF and rheumatoid arthritis (RA) patients, given the similar association of airway inflammation and autoimmunity in RA. Even though we observed that bactericidal permeability-increasing protein (BPI), carbamylated proteins, and citrullinated proteins all localized to the neutrophil extracellular traps (NETs), which are implicated in the development of autoimmunity, our study demonstrates striking autoantibody specificity in CF. Particularly, CF patients developed anti-BPI autoantibodies but hardly any anti-citrullinated protein autoantibodies (ACPA). In contrast, ACPA-positive RA patients exhibited no reactivity with BPI. Interestingly, anti-carbamylated protein autoantibodies (ACarPA) were found in both cohorts but did not cross-react with BPI. Contrary to ACPA and ACarPA, anti-BPI autoantibodies recognized the BPI C-terminus in the absence of posttranslational modifications. In fact, we discovered that P. aeruginosa-mediated NET formation results in BPI cleavage by P. aeruginosa elastase, which suggests a novel mechanism in the development of autoimmunity to BPI. In accordance with this model, autoantibodies associated with presence of P. aeruginosa on sputum culture. Finally, our results provide a role for autoimmunity in CF disease severity, as autoantibody levels associate with diminished lung function.

Mechanisms involved in triggering rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory syndrome with a strong autoimmune component. The autoantigens in RA are neither tissue nor organ-specific, but comprise a broad collection of post-translational modified proteins, such as citrullinated proteins. These modifications are likely to be triggered by innate stimuli. In genetically susceptible hosts, they can lead to a more substantiated secondary autoimmune reaction targeting the joints and precipitating the clinical onset of RA. Both innate and adaptive mechanisms will then closely interplay to promote chronic joint inflammation in the several absence of appropriate treatment. This scenario, is shared with other autoimmune diseases where potentially pathogenic immune responses are present already before disease onset. Better understanding of these processes will allow both earlier diagnosis of RA and identification of those healthy individuals that are at risk of developing disease, opening possibilities for disease prevention. In this review, we discuss the iterative processes of innate and adaptive immunity responsible for the (longitudinal) development of immune reactions that may contribute to the development of RA.

Cigarette Smoke Induces Immune Responses to Vimentin in both, Arthritis-Susceptible and -Resistant Humanized Mice

Rheumatoid arthritis (RA) is an autoimmune disease marked by chronic synovial inflammation and both, genetic and environmental factors are involved in its pathogenesis. Human leukocyte antigen (HLA) DRB1*0401 is associated with susceptibility to develop RA, while cigarette smoke (CS) exposure promotes seropositive disease with increased severity in DRB1*0401+ individuals. Smokers have higher levels of antibodies against citrullinated peptides. In this study, we determined whether the response to a known autoantigen, Vimentin (Vim) is shared epitope specific and how CS influences this response using transgenic-mice carrying RA-susceptible,*0401, and -resistant, *0402, genes. Following relatively brief exposure to CS, peptidyl arginine deiminase (PAD) enzyme expression was increased in murine lungs. Cigarette smoking led to production of Interferon (IFN)-γ with reduced levels of Interleukin (IL)-10 by splenocytes of *0401 mice. In contrast, CS augmented Th2 cytokines along with T-regulatory cells in *0402 mice. An increase in levels of antibodies to native and citrullinated Vim was observed in naïve mice of both strains following CS exposure. Our data showed that both arthritis-susceptible and -resistant mice can generate cellular and humoral immunity to Vim; however CS-induced modulation of host immunity is dependent on the interaction with the host HLA genes.

The Prerequisites for Central Tolerance Induction against Citrullinated Proteins in the Mouse

Objectives

To assess the prerequisites for negative selection of peptidylcitrulline-specific T cells in the thymus. In detail, we here analyzed murine medullary thymic epithelial cells for the expression of peptidylarginine deiminases (PAD) and subsequent citrullination.

Methods

Medullary thymic epithelial cells were sorted, their mRNA was isolated and the expression of Pad genes was analyzed by quantitative PCR. Citrullination was detected by Western Blot in lysates of sorted medullary thymic epithelial cells and histologically by immunofluorescence of thymic thin sections.

Results

Pad2 and Pad4 are the main Pad isoforms expressed in mature medullary thymic epithelial cells of the mouse and their levels of expression are comparable to that of insulin (Ins2), another highly and promiscuously expressed protein in the thymus. Citrullination was detected in medullary thymic epithelial cells as shown by Western Blot and immunofluorescence.

Conclusions

Even though we here show that the murine thymus harbors the prerequisites for central tolerance to PAD and citrullinated peptides, it remains an open question whether the emergence of peptidylcitrulline-specific T cells and of autoantibodies recognizing citrullinated epitopes is caused by a failure of central or peripheral tolerance mechanisms.

Scintigraphic detection of TNF-driven inflammation by radiolabelled certolizumab pegol in patients with rheumatoid arthritis and spondyloarthritis

BACKGROUND

Biologicals are the cornerstone for many treatment algorithms in inflammatory arthritis. While tumour necrosis factor (TNF) inhibitors may achieve important responses in ∼50% of patients with rheumatoid arthritis (RA) and spondyloarthritis (SpA), a significant fraction of patients are partial or non-responders. We hypothesised that in vivo assessment of TNF by scintigraphy with 99mTc-radiolabelled certolizumab pegol (CZP) might lead to a more 'evidence-based biological therapy'.

OBJECTIVES

Our goal was to perform a proof-of-concept study of in vivo detection of TNF by immunoscintigraphy of a radiolabelled TNF inhibitor in RA and SpA, and correlate this with clinical, imaging findings and therapeutic outcome.

METHODS

CZP was conjugated with succinimidyl-6-hydrazino-nicotinamide and subsequently radiolabelled with Tc99m. Whole body and static images of hands, feet and sacroiliac joints of 20 patients (5 RA; 15 SpA) were acquired at 3 time points. Immunoscintigraphic findings were scored semiquantitatively. Subsequently, all patients were treated with CZP.

RESULTS

In peripheral joints, clinically affected joints or abnormal ultrasound findings were observed more frequently (p<0.001) in the scintigraphic-positive group. In patients with axial SpA, bone marrow edema on MRI was detected more frequently (p<0.001) in quadrants with tracer uptake. At the patient level, the odds of a joint remaining tender despite 24 weeks of CZP treatment was significantly smaller in joints with clear tracer uptake as compared with those with no uptake (OR=0.42, p=0.04).

CONCLUSIONS

Immunoscintigraphy with radiolabelled CZP demonstrated both axial and peripheral inflammation, and displayed good correlation with clinical features, conventional imaging and therapy response.

TRIAL REGISTRATION NUMBER

NCT01590966; Results.

How the microbiota shapes rheumatic diseases

The human gut harbours a tremendously diverse and abundant microbial community that correlates with, and even modulates, many health-related processes. The mucosal interfaces are particularly active sites of microorganism-host interplay. Growing insight into the characteristic composition and functionality of the mucosal microbiota has revealed that the microbiota is involved in mucosal barrier integrity and immune function. This involvement affects proinflammatory and anti-inflammatory processes not only at the epithelial level, but also at remote sites such as the joints. Here, we review the role of the gut microbiota in shaping local and systemic immune responses and how disturbances in the host-microorganism interplay can potentially affect the development and progression of rheumatic diseases. Increasing our understanding of how to promote host-microorganism homeostasis could therefore reveal novel strategies for the prevention or alleviation of rheumatic disease.

Recent Advances in Defining the Genetic Basis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most common inflammatory arthritis and exhibits genetic overlap with other autoimmune and inflammatory disorders. Although predominant associations with the HLA-DRB1 locus have been known for decades, recent data have revealed additional insight into the likely causative variants within HLA-DRB1 as well as within other HLA loci that contribute to disease risk. In addition, more than 100 common variants in non-HLA loci have been implicated in disease susceptibility. Genetic factors are involved not only in the development of RA, but also with various disease subphenotypes, including production and circulating levels of autoantibodies and joint destruction. The major current challenge is to integrate these new data into a precise understanding of disease pathogenesis, including the critical cell types and molecular networks involved as well as interactions with environmental factors. We predict that delineating the functional effects of genetic variants is likely to drive new diagnostic and therapeutic approaches to the disease.

Central corneal thickness and corneal curvature in patients with rheumatoid arthritis

The aims of this study were to determine the central corneal thickness (CCT) and corneal curvature (CC) in patients with rheumatoid arthritis (RA), and to evaluate the correlations between the CCT, CC, RA activity, and RA duration. Fifty-four RA patients (104 eyes; 35 with dry eye, 69 without dry eye) and 21 age- and gender-matched control patients (42 eyes) were enrolled in the study. The CCT and CC were measured by ultrasonic pachymeter and autorefractor-keratometer, respectively. RA activity was assessed using the disease activity score (DAS) 28. The independent samples' t test and Pearson correlation analysis were used in the statistical analyses. Mean CCTs were found to be 535.88 ± 38.24, 530.46 ± 32.88, 538.64 ± 40.64, and 543.40 ± 40.66 μm in all RA eyes, RA with dry eyes, RA without dry eyes, and control eyes, respectively. Mean keratometry (K) readings were found to be 43.84 ± 1.76, 43.73 ± 1.23, 43.90 ± 1.98, and 43.60 ± 1.48 D in all RA eyes, RA with dry eyes, RA without dry eyes, and control eyes, respectively. There were no significant differences in CCT values (p values, 0.293, 0.134, and 0.550, respectively) and K readings (p values, 0.435, 0.681, and 0.402, respectively) between the RA and control eyes. These findings led us to the conclusion that the CCT and K readings were not significantly associated with DAS (p values, 0.678 and 0.812, respectively) and RA duration (p values, 0.108 and 0.080, respectively). Our results show that CCTs and CCs were not significantly different between the RA eyes and control eyes. CCTs and CCs were also not associated with RA activity and RA duration.