Anticitrullinated Protein Antibody, But Not Its Titer, Is a Predictor of Radiographic Progression and Disease Activity in Rheumatoid Arthritis

Heavy Chain Constant Region Usage in Antibodies to Peptidylarginine Deiminase 4 as a Marker of Disease Subsets in Rheumatoid Arthritis

OBJECTIVE

The study of autoantibody isotypes in autoimmune diseases is useful for identifying clinically relevant endotypes. This study was undertaken to study the prevalence and clinical significance of different isotypes and IgG subclasses of anti-peptidylarginine deiminase 4 (anti-PAD4) autoantibodies in individuals with rheumatoid arthritis (RA).

METHODS

In 196 RA subjects and 64 healthy controls, anti-PAD4 antibody types were determined using enzyme-linked immunosorbent assay. We investigated associations between anti-PAD4 antibodies and clinical outcomes, and relevant features were confirmed in an independent RA cohort.

RESULTS

Anti-PAD4 IgG1, anti-PAD4 IgG2, anti-PAD4 IgG3, anti-PAD4 IgG4, anti-PAD4 IgA, and anti-PAD4 IgE antibodies were more frequent in RA patients than healthy controls (P < 0.001). Anti-PAD4 IgG1, anti-PAD4 IgG3, and anti-PAD4 IgE were associated with distinct clinical features. Anti-PAD4 IgG1 was predictive of progressive radiographic joint damage (odds ratio [OR] 4.88, P = 0.005), especially in RA patients without baseline joint damage (40% versus 0%, P = 0.003) or in those negative for anti-cyclic citrullinated peptide and/or rheumatoid factor (OR 32; P = 0.009). IgG1 was also associated with higher levels of C-reactive protein (P = 0.006) and interleukin-6 (P = 0.021). RA patients with anti-PAD4 IgG3 had higher baseline joint damage scores (median Sharp/van der Heijde score 13 versus 7, P = 0.046), while those with anti-PAD4 IgE had higher Disease Activity Score in 28 joints (median 4.0 versus 3.5, P = 0.025), more frequent rheumatoid nodules (31% versus 16%, P = 0.025), and more frequent interstitial lung disease (ground-glass opacification) (24% versus 9%, P = 0.014). Anti-PAD4 IgG1 antibody associations with joint damage were corroborated in an independent RA cohort.

CONCLUSION

Anti-PAD4 IgG1, anti-PAD4 IgG3, and anti-PAD4 IgE antibodies identify discrete disease subsets in RA, suggesting that heavy chain usage drives distinct effector mechanisms of anti-PAD4 antibodies in RA.

Presence of Autoantibodies in Males and Females With Rheumatoid Arthritis: A Systematic Review and Metaanalysis

OBJECTIVE

Rheumatoid arthritis (RA) is more common in females, and although the cause of RA is unknown, it is characterized by the production of autoantibodies. The aims of this study were to determine whether RA-associated autoantibodies are more often found in females than males and to identify factors that influence the relationship between sex and seropositivity.

METHODS

Databases were searched and studies of RA (N ≥ 100) were included if they reported proportion of seropositive patients with RA by sex. Metaanalyses and metaregression were conducted using the random-effects model. Covariates regressed were smoking, age, BMI, Health Assessment Questionnaire-Disability Index (HAQ-DI), and the Disease Activity Score in 28 joints (DAS28).

RESULTS

Eighty-four studies with a total of 141,381 subjects with rheumatoid factor (RF) seropositivity and 95,749 subjects with anticitrullinated protein antibody (ACPA) seropositivity met inclusion criteria. The mean age of participants ranged from 37 to 68 years and the proportion of female subjects ranged from 9% to 92%. Results indicated that females were less likely than males to be seropositive: odds ratio (OR) 0.84 [95% CI 0.77-0.91] for RF and OR 0.88 [95% CI 0.81-0.95] for ACPA. BMI, smoking, mean age, DAS28, and HAQ-DI did not affect the relationship between sex and seropositivity.

CONCLUSION

Although studies report that females have higher RA disease activity than males and that seropositivity predicts worse outcomes, females were less likely to be seropositive than males.

Efficacy of Abatacept Versus Tumor Necrosis Factor Inhibitors in Anti-citrullinated Protein Antibody-Positive Patients with Rheumatoid Arthritis: Results from a Korean Nationwide Biologics Registry

INTRODUCTION

To compare the efficacy of abatacept and tumor necrosis factor inhibitor (TNFi) in patients with anti-citrullinated protein antibody (ACPA)-positive rheumatoid arthritis (RA) and identify those who benefit most from abatacept over TNFi.

METHODS

This observational study identified RA patients who were ACPA-positive and initiated abatacept or TNFi from the Korean College of Rheumatology Biologics and Targeted therapy registry. Propensity score (PS) matching was performed to balance baseline confounding in abatacept- or TNFi-treated patients. The major endpoints were changes in Clinical Disease Activity Index (CDAI) and achievement of CDAI remission/low disease activity after 1 year of treatment. Subgroup analysis was mainly performed stratified by prior biologics use.

RESULTS

A total of 291 PS-matched, ACPA-positive RA patients who initiated abatacept (n = 97) and TNFi (n = 194) were included. From baseline CDAI scores of 26.52 in the abatacept group and 26.38 in the TNFi group, the mean changes after 1 year were - 16.78 and - 13.61, respectively (difference - 3.17, p = 0.020). The proportion of patients achieving CDAI remission/low disease activity was 68.0% with abatacept and 52.6% with TNFi (p = 0.013). In the subgroup analysis, patients that were biologics-naïve had better improvement in CDAI after treatment with abatacept than TNFi (difference - 3.35, p = 0.021).

CONCLUSIONS

This real-world study suggests that abatacept may have better clinical response compared to TNFi in patients with established ACPA-positive RA, especially in those that were biologics-naïve.

Comparison of healthcare resource utilization and medical costs between patients with seropositive and seronegative rheumatoid arthritis

Objectives:

To compare healthcare utilization and medical costs between patients with seronegative (SN) and seropositive (SP) rheumatoid arthritis (RA).

Methods:

We conducted a nationwide population study using the Korean health insurance claims database in 2016. We divided patients with RA into SN and SP groups and compared healthcare utilization including medications, medical utilization, and direct medical costs for 1 year between the groups in a cross-sectional analysis. Differences in costs between patients with SPRA and SNRA were assessed using the quantile regression model. We performed longitudinal analysis using data from 2012 and 2016 to examine changes over time.

Results:

A total of 103,815 SPRA and 75,809 SNRA patients were included in the analyses. The SPRA group used significantly more methotrexate (73.2% versus 30.3%) and biologic agents (7.9% versus 2.9%) than the SNRA group. The number of RA-related outpatient visits [6.0 ± 3.7 versus 4.4 ± 4.0 times/year, standardized difference (SD) = 0.41] and annual medical costs per patient ($1027 versus $450/year, SD = 0.25) were higher in the SPRA group than the SNRA group. Quantile regression results indicated that the incremental cost of seropositivity on total medical costs of RA patients gradually increased as medical costs approached the upper quantile. The annual direct medical costs for each patient between 2012 and 2016 increased in both groups: by 25.1% in the SPRA group and 37.6% in the SNRA group.

Conclusion:

Annual RA-related direct medical costs and RA-related healthcare utilization per patient are higher in patients with SPRA than those with SNRA.

Guidelines for biomarkers in autoimmune rheumatic diseases - evidence based analysis

Autoimmune rheumatic diseases are characterised by an abnormal immune system response, complement activation, cytokines dysregulation and inflammation. In last years, despite many progresses in managing these patients, it has been shown that clinical remission is reached in less than 50% of patients and a personalised and tailored therapeutic approach is still lacking resulting in a significant gap between guidelines and real-world practice. In this context, the need for biomarkers facilitating early diagnosis and profiling those individuals at the highest risk for a poor outcome has become of crucial interest. A biomarker generally refers to a measured characteristic which may be used as an indicator of some biological state or condition. Three different types of medical biomarkers has been suggested: i. mechanistic markers; ii. clinical disease markers; iii. therapeutic markers. A combination of biomarkers from these different groups could be used for an ideal more accurate diagnosis and treatment. However, although a growing body of evidence is focused on improving biomarkers, a significant amount of this information is not integrated on standard clinical care. The overarching aim of this work was to clarify the meaning of specific biomarkers during autoimmune diseases; their possible role in confirming diagnosis, predicting outcome and suggesting specific treatments.

Regulation of autoantibody activity by the IL-23-TH17 axis determines the onset of autoimmune disease

The checkpoints and mechanisms that contribute to autoantibody-driven disease are as yet incompletely understood. Here we identified the axis of interleukin 23 (IL-23) and the TH17 subset of helper T cells as a decisive factor that controlled the intrinsic inflammatory activity of autoantibodies and triggered the clinical onset of autoimmune arthritis. By instructing B cells in an IL-22- and IL-21-dependent manner, TH17 cells regulated the expression of β-galactoside α2,6-sialyltransferase 1 in newly differentiating antibody-producing cells and determined the glycosylation profile and activity of immunoglobulin G (IgG) produced by the plasma cells that subsequently emerged. Asymptomatic humans with rheumatoid arthritis (RA)-specific autoantibodies showed identical changes in the activity and glycosylation of autoreactive IgG antibodies before shifting to the inflammatory phase of RA; thus, our results identify an IL-23-TH17 cell-dependent pathway that controls autoantibody activity and unmasks a preexisting breach in immunotolerance.

Prognostic Factors Toward Clinically Relevant Radiographic Progression in Patients With Rheumatoid Arthritis in Clinical Practice: A Japanese Multicenter, Prospective Longitudinal Cohort Study for Achieving a Treat-to-Target Strategy

To determine prognostic factors of clinically relevant radiographic progression (CRRP) in patients with rheumatoid arthritis (RA) in clinical practice.We performed a multicenter prospective study in Japan of biological disease-modifying antirheumatic drug (bDMARD)-naive RA patients with moderate to high disease activity treated with conventional synthetic DMARDs (csDMARDs) at study entry. We longitudinally observed 408 patients for 1 year and assessed disease activity every 3 months. CRRP was defined as yearly progression of modified total Sharp score (mTSS) > 3.0 U. We also divided the cohort into 2 groups based on disease duration (<3 vs ≥3 years) and performed a subgroup analysis.CRRP was found in 10.3% of the patients. A multiple logistic regression analysis revealed that the independent variables to predict the development of CRRP were: CRP at baseline (0.30 mg/dL increase, 95% confidence interval [CI] 1.01-1.11), time-integrated Disease Activity Score in 28 joints-erythrocyte sedimentation rate (DAS28-ESR) during the 1 year postbaseline (12.4-unit increase, 95%CI 1.17-2.59), RA typical erosion at baseline (95%CI 1.56-21.1), and the introduction of bDMARDs (95%CI 0.06-0.38). The subgroup analysis revealed that time-integrated DAS28-ESR is not a predictor whereas the introduction of bDMARDs is a significant protective factor for CRRP in RA patients with disease duration <3 years.We identified factors that could be used to predict the development of CRRP in RA patients treated with DMARDs. These variables appear to be different based on the RA patients' disease durations.

Label-free detection of immune complexes with myeloid cells

The aim of this study was to provide proof-of-concept for quantitative and qualitative label-free detection of immune complexes through myeloid cells with imaging surface plasmon resonance. Surface plasmon resonance imaging was first applied to monitor the binding of human sera from healthy and rheumatoid arthritis (RA) patients to immobilized citrullinated RA-specific peptide antigens, histone citrullinated peptide 2 (HCP2) and viral citrullinated peptide 2 (VCP2). Next, the binding of monocytoid cell line U937 to the resulting immune complexes on the sensor surface was monitored. As control, binding of U937 was monitored to immunoglobulin (Ig)G subclasses simultaneously. Cell response results were compared to results of cyclic citrullinated peptide 2 (CCP2) enzyme-linked immunosorbent assay (ELISA), clinical RA diagnosis and antigen-specific antibody distribution of the samples. Human IgG3 triggered the most pronounced response, followed by IgG1 and IgG4, while IgG2 did not result in U937 cell binding. Serum samples obtained from RA patients resulted in a significantly increased cell response to VCP2 compared to healthy controls. The strength of cell response towards VCP2 immune complexes showed significant correlation with levels of antigen-specific IgA, IgG and IgG3. Cellular responses on VCP2 immune complexes showed significant association with both CCP2-based serological positivity and European League Against Rheumatism (EULAR) criteria-based clinical RA diagnosis. Immunoglobulin-triggered binding of monocytoid cells can be monitored using a label-free multiplex technology. Because these binding events are presumably initiated by Fc receptors, the system provides a tool for biological detection of autoantibodies with diagnostic value, here exemplified by anti-citrullinated antibodies. This provides added information to antibody levels, as interaction with Fc-receptor-expressing cells is also affected by post-translational modification of the immunoglobulins.

MMP-3 as a predictor for structural remission in RA patients treated with MTX monotherapy

Background

The study was undertaken to assess the efficacy of methotrexate (MTX) monotherapy on the radiographic progression of individual rheumatoid arthritis (RA) patients, each of whom had received MTX monotherapy for 3 years with an option to change to biological disease-modifying anti-rheumatic drugs (bDMARDs). We also looked for predictors of radiographic non-progression in these patients.

Methods

Rheumatoid patients (n = 161) were prospectively followed for 3 years while receiving low-dose MTX monotherapy unless disease was otherwise active and/or adverse events appeared. Their disease activity and radiographic progression were evaluated with reference to disease activity score 28 (DAS28), modified health assessment of questionnaire (mHAQ) and other indices. The change in van der Heijde-modified total Sharp score per year (∆TSS) was assessed using probability plots, in which the patients were classified into the subgroups showing structural remission (REM; ∆TSS ≤0.5), radiographic progression (∆TSS >3) or rapid radiographic progression (RRP; ∆TSS >5).

Results

MTX monotherapy, continued until disease became active and/or adverse event appeared, was associated with a significant improvement (p <0.0001) in the DAS28-ESR (3) scores, % DAS28 remission, and mHAQ scores each year, from baseline to 3 years. The mHAQ remission rate (∆mHAQ <0.5) and Boolean remission were also improved from 16 to 60 % and 0.8 to 24.0 %, respectively. We found that the ratio of patients classified as REM increased yearly from 62/161 (38.5 %) to 69/137 (50.4 %), while those classified as ∆TSS >3 decreased from 55/161 (34.2 %) to 28/137 (20.4 %) and those in RRP decreased from 35/161 (21.7 %) to 15/137 (10.9 %). Receiver operating characteristic (ROC) curve analyses showed that serum matrix metalloproteinase-3 (MMP-3) <103.7 ng/ml at outset predicts a patient subgroup that exhibits no radiographic progression.

Conclusions

Half of rheumatoid patients treated with MTX monotherapy for 3 years exhibited structural remission, and this outcome can be predicted at the outset by lower serum MMP-3.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0948-7) contains supplementary material, which is available to authorized users.

Positive association between serum thymic stromal lymphopoietin and anti-citrullinated peptide antibodies in patients with rheumatoid arthritis

Thymic stromal lymphopoietin (TSLP) has been suggested recently to play an important role in the pathophysiology of rheumatoid arthritis (RA). However, there is little information on serum TSLP concentrations in RA and its clinical significance. The present study investigated whether serum TSLP concentrations were affected in patients with RA. Using an enzyme-linked immunosorbent assay (ELISA), we measured TSLP concentrations in the serum obtained from 100 patients with RA, 60 patients with osteoarthritis (OA) and 34 healthy volunteers. We also investigated the correlation between serum TSLP concentrations and clinical parameters of disease activity in RA [disease activity score using 28 joint counts (DAS28)-C-reactive protein (CRP), DAS28-erythrocyte sedimentation rate (ESR), Clinical Disease Activity Index (CDAI]), patient's/-physician's Visual Analogue Scale (VAS), swollen joints count, tender joints count, CRP, ESR and matrix metalloproteinase-3 (MMP-3) concentrations]. In addition, we investigated the correlation between serum TSLP concentrations and anti-citrullinated peptide antibody (ACPA) and serum tumour necrosis factor (TNF)-α. Serum TSLP levels in patients with RA were significantly higher than those in patients with OA and in healthy volunteers. Interestingly, serum TSLP concentrations were correlated significantly with ACPA titres, but not with other clinical parameters. There was a significant increase in serum TSLP concentrations in patients with RA, which was correlated positively with serum ACPA titres. These findings suggest that in patients with RA, TSLP may play a role in ACPA production by B cells.

Rheumatoid factor and anti-citrullinated protein antibody positivity, but not level, are associated with increased mortality in patients with rheumatoid arthritis: results from two large independent cohorts

Introduction

This study aimed to investigate rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA) status and levels as predictors of mortality in two large cohorts of patients with early inflammatory arthritis (EIA).

Methods

Data from the Norfolk Arthritis Register (NOAR) and Leiden Early Arthritis Clinic (EAC) cohorts were used. At baseline, patients had demographic data and smoking status recorded; RF, ACPA and inflammatory markers were measured in the local laboratories. Patients were flagged with national death registers until death or censor date. Antibody status was stratified as negative, low or high positive by RF and ACPA levels individually. In addition, patients were grouped as seronegative, RF positive, ACPA positive or double antibody (RF and ACPA) positive. Cox regression models explored associations between antibody status and mortality adjusting for age, sex, smoking status, inflammatory markers and year of enrolment.

Results

A total of 4962 patients were included, 64% were female. Median age at onset was 56 (NOAR) and 54 (EAC) years. In NOAR and EAC respectively, 35% and 42% of patients were ACPA/RF positive. When antibody status was stratified as negative, low or high positive, there were no consistent findings between the two cohorts. Double antibody positivity was associated with excess mortality in both cohorts compared to seronegative patients: NOAR and EAC respective adjusted HR (95% confidence interval) 1.35 (1.09 to 1.68) and 1.58 (1.16 to 2.15).

Conclusions

Patients with EIA who are seropositive for both RF and ACPA have increased mortality compared to those who are single positive or seronegative. Antibody level in seropositive patients was not consistently associated with excess mortality.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0483-3) contains supplementary material, which is available to authorized users.

Interleukin-6 receptor blockade selectively reduces IL-21 production by CD4 T cells and IgG4 autoantibodies in rheumatoid arthritis

Interleukin-6 (IL-6) levels are known to be increased in patients with rheumatoid arthritis (RA). Tocilizumab, a monoclonal antibody to the IL-6 receptor (IL-6R), reduces disease activity in RA, although its mechanisms of action remain unclear. Since IL-6 regulates cytokine production by CD4 T cells during activation, we investigated whether treatment with tocilizumab altered the phenotype and cytokine production by CD4 T cells in patients with rheumatoid arthritis. We show here that tocilizumab treatment does not change the production of cytokines by naïve CD4 T cells. However, tocilizumab treatment causes a selective decrease of IL-21 production by memory/activated CD4 T cells. Since IL-21 is known to promote plasma cell differentiation, we examined the effect of tocilizumab on the production of autoantibodies. We show that there is a decrease in the levels of IgG4 anti-CCP antibodies, but there is no effect on IgG1 anti-CCP antibodies. In addition, we show that IL-21 is a powerful inducer of IgG4 production by B cells. Thus, IL-6 contributes to the presence of IgG4-specific anti-CCP autoantibodies in RA patients, likely through its effect on IL-21 production by CD4 T cells, and IL-6R blockade down-regulates this pathway.