Autoantibody epitope spreading in the pre-clinical phase predicts progression to rheumatoid arthritis

Antibody-induced pain-like behavior and bone erosion: links to subclinical inflammation, osteoclast activity, and acid-sensing ion channel 3-dependent sensitization

ABSTRACT

Several bone conditions, eg, bone cancer, osteoporosis, and rheumatoid arthritis (RA), are associated with a risk of developing persistent pain. Increased osteoclast activity is often the hallmark of these bony pathologies and not only leads to bone remodeling but is also a source of pronociceptive factors that sensitize the bone-innervating nociceptors. Although historically bone loss in RA has been believed to be a consequence of inflammation, both bone erosion and pain can occur years before the symptom onset. Here, we have addressed the disconnection between inflammation, pain, and bone erosion by using a combination of 2 monoclonal antibodies isolated from B cells of patients with RA. We have found that mice injected with B02/B09 monoclonal antibodies (mAbs) developed a long-lasting mechanical hypersensitivity that was accompanied by bone erosion in the absence of joint edema or synovitis. Intriguingly, we have noted a lack of analgesic effect of naproxen and a moderate elevation of few inflammatory factors in the ankle joints suggesting that B02/B09-induced pain-like behavior does not depend on inflammatory processes. By contrast, we found that inhibiting osteoclast activity and acid-sensing ion channel 3 signaling prevented the development of B02/B09-mediated mechanical hypersensitivity. Moreover, we have identified secretory phospholipase A2 and lysophosphatidylcholine 16:0 as critical components of B02/B09-induced pain-like behavior and shown that treatment with a secretory phospholipase A2 inhibitor reversed B02/B09-induced mechanical hypersensitivity and bone erosion. Taken together, our study suggests a potential link between bone erosion and pain in a state of subclinical inflammation and offers a step forward in understanding the mechanisms of bone pain in diseases such as RA.

Evaluation of the immune feature of ACPA-negative rheumatoid arthritis and the clinical value of matrix metalloproteinase-3

Anti-citrullinated protein antibodies (ACPAs) are highly specific for the diagnosis of rheumatoid arthritis (RA). However, about one-third of RA patients are negative for ACPAs, which presents a challenge to the early diagnosis of RA. The purpose of this study was to analyze differences in lymphocyte subsets and CD4+ T cell subsets between ACPA+ and ACPA- RA patients, and to evaluate the value of matrix metalloproteinase-3 (MMP-3) as a diagnostic and monitoring marker in ACA- RA patients. A total of 145 ACPA+ RA patients, 145 ACPA- RA patients, and 38 healthy controls (HCs) were included in this study. Peripheral lymphocyte subsets were detected using flow cytometry, and serum MMP-3 was detected using chemiluminescence. Information about joint symptoms, other organ involvement, and related inflammatory markers was also collected. The results showed that, compared to ACPA- RA patients, ACPA+ cases had greater imbalances between peripheral CD4+ T cell subsets, mainly manifested as an increase in T-helper 1 (Th1) cells (p < 0.001) and decrease in regulatory T (Treg) cells (p = 0.029). This makes these patients more prone to inflammatory reactions and joint erosion. MMP-3 levels in ACPA+ and ACPA- RA patients were significantly higher than in HCs (p < 0.001), and MMP-3 could effectively distinguish between ACPA- RA patients and HCs (area under the curve [AUC] = 0.930, sensitivity 84.14%, specificity 92.11%). MMP-3 was also a serum marker for distinguishing between RA patients with low and high disease activities. Further analysis showed that MMP-3 was positively correlated with the levels of inflammatory markers and disease activity, and negatively correlated with the levels of lymphocyte subsets. In addition, with improvements in the disease, MMP-3 levels decreased, and further increased as the patients started to deteriorate. In summary, our research showed that there was a mild imbalance between peripheral CD4+ T cell subsets in ACPA- RA patients. MMP-3 may be used as a potential marker for early diagnosis of ACPA- RA. MMP-3 was an important index for RA disease evaluation, disease activity stratification, and prognosis.

A Roadmap for Investigating Preclinical Autoimmunity Using Patient-Oriented and Epidemiologic Study Designs: Example of Rheumatoid Arthritis

Background & Aims

Rheumatoid arthritis (RA) is a prototypic autoimmune disease causing inflammatory polyarthritis that affects nearly 1% of the population. RA can lead to joint destruction and disability along with increased morbidity and mortality. Similar to other autoimmune diseases, RA has distinct preclinical phases corresponding to genetic risk, lifestyle risk factors, autoantibody development, and non-specific symptoms prior to clinical diagnosis. This narrative review will detail observational studies for RA risk and clinical trials for RA prevention as a roadmap to investigating preclinical autoimmunity that could be applied to other diseases.

Methods

In this narrative review, we summarized previous and ongoing research studies investigating RA risk and prevention, categorizing them related to their design and preclinical phases.

Results

We detailed the following types of studies investigating RA risk and prevention: retrospective population-based and administrative datasets; prospective studies (case-control and cohort; some enrolling based on genetics, first-degree relative status, elevated biomarkers, or early symptoms/arthritis); and randomized clinical trials. These correspond to all preclinical RA phases (genetic, lifestyle, autoimmunity, early signs/symptoms). Previous and ongoing randomized controlled trials have enrolled individuals at very elevated risk for RA based on biomarkers, symptoms, imaging abnormalities, or early signs/symptoms.

Conclusion

We detailed the rich variety of study designs that is necessary to investigate distinct preclinical phases of an autoimmune disease such as RA. However, further progress is needed to fully elucidate the pathogenesis of RA that may ultimately lead to prevention or delay of disease onset.

From risk to chronicity: evolution of autoreactive B cell and antibody responses in rheumatoid arthritis

The presence of disease-specific autoantibody responses and the efficacy of B cell-targeting therapies in rheumatoid arthritis (RA) indicate a pivotal role for B cells in disease pathogenesis. Important advances have shaped our understanding of the involvement of autoantibodies and autoreactive B cells in the disease process. In RA, autoantibodies target antigens with a variety of post-translational modifications such as carbamylation, acetylation and citrullination. B cell responses against citrullinated antigens generate anti-citrullinated protein antibodies (ACPAs), which are themselves modified in the variable domains by abundant N-linked glycans. Insights into the induction of autoreactive B cells against antigens with post-translational modifications and the development of autoantibody features such as isotype usage, epitope recognition, avidity and glycosylation reveal their relationship to particular RA risk factors and clinical phenotypes. Glycosylation of the ACPA variable domain, for example, seems to predict RA onset in ACPA⁺ healthy individuals, possibly because it affects B cell receptor signalling. Moreover, ACPA-expressing B cells show dynamic phenotypic changes and develop a continuously proliferative and activated phenotype that can persist in patients who are in drug-induced clinical remission. Together, these findings can be integrated into a conceptual framework of immunological autoreactivity in RA, delineating how it develops and persists and why disease activity recurs when therapy is tapered or stopped.

T Cell Help in the Autoreactive Germinal Center

The germinal center serves as a site of B cell selection and affinity maturation, critical processes for productive adaptive immunity. In autoimmune disease tolerance is broken in the germinal center reaction, leading to production of autoreactive B cells that may propagate disease. Follicular T cells are crucial regulators of this process, providing signals necessary for B cell survival in the germinal center. Here we review the emerging roles of follicular T cells in the autoreactive germinal center. Recent advances in immunological techniques have allowed study of the gene expression profiles and repertoire of follicular T cells at unprecedented resolution. These studies provide insight into the potential role follicular T cells play in preventing or facilitating germinal center loss of tolerance. Improved understanding of the mechanisms of T cell help in autoreactive germinal centers provides novel therapeutic targets for diseases of germinal center dysfunction.

Accelerated atherosclerosis in rheumatoid arthritis: a systematic review

Background: Rheumatoid arthritis (RA) is a highly prevalent, chronic inflammatory condition of the synovial joints that affects approximately 1% of the global population. The pathogenesis of RA is predominantly inflammatory in nature, thereby accelerating the co-occurrence of other immunoinflammatory conditions such as atherosclerosis. Apart from traditional cardiovascular risk factors, RA patients possess a multitude of other factors that predispose them to early atherosclerotic disease. The aim of this systematic review is to assess the prevalence of premature atherosclerosis in RA patients and elucidate the role that proinflammatory cytokines, RA-related autoantibodies, and endothelial dysfunction play in the pathophysiology of RA-mediated atherosclerosis. We also discussed novel biomarkers that can be used to predict early atherosclerosis in RA and current guidelines used to treat RA. Methods: This review followed the PRISMA guidelines to select and analyze relevant articles. A literature search for articles was performed on February 25, 2022, through three research databases including PubMed, ProQuest, and ScienceDirect. The query used to identify relevant publications was "Rheumatoid arthritis and atherosclerosis" and the search duration was set from 2012-2022. Relevant articles were selected based on the inclusion and exclusion criteria. Results: Our initial search generated 21,235 articles. We narrowed our search according to the inclusion and exclusion criteria. After assessing eligibility based on the full content of the articles, 73 articles were ultimately chosen for this review. Conclusion: There is an increased prevalence of accelerated atherosclerosis among RA patients. We found evidence to explain the role of proinflammatory cytokines, RA-related autoantibodies, and endothelial dysfunction in the pathophysiology RA-mediated atherosclerosis. Therapies targeting either the inflammatory load or traditional CV risk-factors seem to improve vascular outcomes in RA patients. Novel markers of atherosclerosis in RA may be useful in predicting premature atherosclerosis and serve as new targets for therapeutic intervention.

Differential Changes in ACPA Fine Specificity and Gene Expression in a Randomized Trial of Abatacept and Adalimumab in Rheumatoid Arthritis

INTRODUCTION

The biologics abatacept and adalimumab have different mechanisms of action (MoAs). We analyzed data from patients with rheumatoid arthritis treated in AMPLE (NCT00929864) to explore the pharmacodynamic effects of abatacept or adalimumab on anti-citrullinated protein antibodies (ACPAs) and gene expression.

METHODS

AMPLE was a phase IIIb, 2-year, randomized, head-to-head trial of abatacept versus adalimumab. Post hoc analyses of baseline anti-cyclic citrullinated peptide-2 (anti-CCP2, an ACPA surrogate) positive (+) status and ACPA fine-specificity profiles over time, as well as transcriptional profiling (peripheral whole blood), were performed.

RESULTS

Of 646 patients treated (abatacept, n = 318; adalimumab, n = 328), ACPA and gene expression data were available from 508 and 566 patients, respectively. In anti-CCP2+ patients (n = 388), baseline fine specificities for most ACPAs were highly correlated; over 2 years, levels decreased with abatacept but not adalimumab. By year 2, expression of genes associated with T cell co-stimulation and antibody production was lower for abatacept versus adalimumab; expression of genes associated with proinflammatory signaling was lower for adalimumab versus abatacept. Treatment modulated the expression of T- and B-cell gene signatures, with differences in CD8+ T cells, activated T cells, plasma cells, B cells, natural killer cells (all lower with abatacept versus adalimumab), and polymorphonuclear leukocytes (higher with abatacept versus adalimumab).

CONCLUSIONS

In AMPLE, despite similar clinical outcomes, data showed that pharmacodynamic/genetic changes after 2 years of abatacept or adalimumab were consistent with drug MoAs. Further assessment of the relationship between such changes and clinical outcomes, including prediction of response, is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT00929864.

Prospective Studies on the Risk of Rheumatoid Arthritis: The European Risk RA Registry

Background

The accumulation of risk for the development of rheumatoid arthritis (RA) is regarded as a continuum that may start with interacting environmental and genetic factors, proceed with the initiation of autoimmunity, and result in the formation of autoantibodies such as anti-citrullinated peptide antibodies (ACPA). In parallel, at-risk individuals may be asymptomatic or experience joint pain (arthralgia) that is itself non-specific or clinically suspicious for evolving RA, even in the absence of overt arthritis. Optimal strategies for the management of people at-risk of RA, both for symptom control and to delay or prevent progression to classifiable disease, remain poorly understood.

Methods

To help address this, groups of stakeholders from academia, clinical rheumatology, industry and patient research partners have collaborated to advance understanding, define and study different phases of the at-risk state. In this current report we describe different European initiatives in the field and the successful effort to build a European Registry of at-risk people to facilitate observational and interventional research.

Results

We outline similarities and differences between cohorts of at-risk individuals at institutions spanning several countries, and how to best combine them within the new database. Over the past 2 years, besides building the technical infrastructure, we have agreed on a core set of variables that all partners should strive to collect for harmonization purposes.

Conclusion

We emphasize to address this process from different angles and touch on the biologic, epidemiologic, analytic, and regulatory aspects of collaborative studies within a meta-database of people at-risk of RA.

Pre-RA: Can early diagnosis lead to prevention?

Rheumatoid arthritis (RA) is currently diagnosed and treated once an individual displays the clinical findings of inflammatory arthritis (IA). However, growing evidence supports that there is a 'pre-RA' stage that can be identified through factors such as autoantibodies in absence of clinically apparent IA. In particular, biomarkers, including antibodies to citrullinated protein antigens (ACPA), demonstrate a high risk for future IA/RA, and multiple clinical trials have been developed to intervene in individuals in pre-RA to prevent or delay clinically apparent disease. Herein, we will discuss in more depth what is currently known about the natural history of RA, and the emerging possibility that early 'diagnosis' of RA-related autoimmunity followed by an intervention can lead to the delay or prevention of the first onset of clinically apparent RA.

New Druggable Targets for Rheumatoid Arthritis Based on Insights From Synovial Biology

Rheumatoid arthritis (RA) is a multifactorial autoimmune disease characterized by chronic inflammation and destruction of multiple small joints which may lead to systemic complications. Altered immunity via pathogenic autoantibodies pre-date clinical symptom development by several years. Incompletely understood range of mechanisms trigger joint-homing, leading to clinically evident articular disease. Advances in therapeutic approaches and understanding pathogenesis have improved prognosis and likely remission. However, partial/non-response to conventional and biologic therapies witnessed in a subset of patients highlights the need for new therapeutics. It is now evident that joint disease chronicity stems from recalcitrant inflammatory synovial environment, majorly maintained by epigenetically and metabolically reprogrammed synoviocytes. Therefore, interference with effector functions of activated cell types seems a rational strategy to reinstate synovial homeostasis and complement existing anti-inflammatory interventions to mitigate chronic RA. Presenting this newer aspect of fibroblast-like synoviocytes and myeloid cells underlying the altered synovial biology in RA and its potential for identification of new druggable targets is attempted in this review. Major leads from i) molecular insights of pathogenic cell types from hypothesis free OMICS approaches; ii) hierarchy of their dysregulated signaling pathways; and iii) knowledge of druggability of molecular nodes in these pathways are highlighted. Development of such synovial biology-directed therapeutics hold promise for an enriched drug repertoire for RA.

Serum rheumatoid factor IgA, anti-citrullinated peptide antibodies with secretory components, and anti-carbamylated protein antibodies associate with interstitial lung disease in rheumatoid arthritis

Objective

Rheumatoid arthritis (RA) is often complicated with chronic lung diseases (CLD), including interstitial lung disease (ILD) and airway disease, which occur as extra-articular manifestations. CLD in RA have been associated with the production of rheumatoid factor (RF), anti-citrullinated peptide antibody (ACPA), or anti-carbamylated protein (CarP) antibody. However, few validation studies have been performed thus far. In the present study, we investigated the association of RF, ACPA, and anti-CarP antibodies with RA complicated with CLD.

Methods

Sera from RA patients with or without CLD were collected. The levels of serum RF, RF immunoglobulin A (IgA), ACPA IgG, ACPA IgA, and ACPA secretory component (SC) were measured using enzyme-linked immunosorbent assay.

Results

The comparison of RA patients with and without CLD showed that RF IgA was associated with ILD (mean ± standard deviation: 206.6 ± 400.5 vs. 95.0 ± 523.1 U/ml, respectively, P = 1.13 × 10^− 8), particularly usual interstitial pneumonia (UIP) (263.5 ± 502.0 U/ml, P = 1.00 × 10^− 7). ACPA SC was associated with RA complicated with ILD (mean ± standard deviation: 8.6 ± 25.1 vs. 2.3 ± 3.4 U/ml, respectively, P = 0.0003), particularly nonspecific interstitial pneumonia (NSIP) (10.7 ± 31.5 U/ml, P = 0.0017). Anti-CarP antibodies were associated with RA complicated with ILD (0.042 ± 0.285 vs. 0.003 ± 0.011 U/ml, respectively, P = 1.04X10^− 11).

Conclusion

RF IgA and ACPA SC in RA were associated with UIP and NSIP, respectively, suggesting different specificities in patients with RA. Anti-CarP antibodies were associated with ILD in RA. These results may help elucidate the different pathogeneses of UIP and NSIP in RA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04985-0.

Follicular dendritic cell differentiation is associated with distinct synovial pathotype signatures in rheumatoid arthritis

Follicular dendritic cells (FDCs) fundamentally contribute to the formation of synovial ectopic lymphoid-like structures in rheumatoid arthritis (RA) which is associated with poor clinical prognosis. Despite this critical role, regulation of FDC development in the RA synovium and its correlation with synovial pathotype differentiation remained largely unknown. Here, we demonstrate that CNA.42⁺ FDCs distinctively express the pericyte/fibroblast-associated markers PDGFR-β, NG2, and Thy-1 in the synovial perivascular space but not in established follicles. In addition, synovial RNA-Seq analysis revealed that expression of the perivascular FDC markers was strongly correlated with PDGF-BB and fibroid synovitis, whereas TNF-α/LT-β was significantly associated with lymphoid synovitis and expression of CR1, CR2, and FcγRIIB characteristic of mature FDCs in lymphoid follicles. Moreover, PDGF-BB induced CNA.42⁺ FDC differentiation and CXCL13 secretion from NG2⁺ synovial pericytes, and together with TNF-α/LT-β conversely regulated early and late FDC differentiation genes in unsorted RA synovial fibroblasts (RASF) and this was confirmed in flow sorted stromal cell subsets. Furthermore, RASF TNF-αR expression was upregulated by TNF-α/LT-β and PDGF-BB; and TNF-α/LT-β-activated RASF retained ICs and induced B cell activation in in vitro germinal center reactions typical of FDCs. Additionally, FDCs trapped peptidyl citrulline, and strongly correlated with IL-6 expression, and plasma cell, B cell, and T cell infiltration of the RA synovium. Moreover, synovial FDCs were significantly associated with RA disease activity and radiographic features of tissue damage. To the best of our knowledge, this is the first report describing the reciprocal interaction between PDGF-BB and TNF-α/LT-β in synovial FDC development and evolution of RA histological pathotypes. Selective targeting of this interplay could inhibit FDC differentiation and potentially ameliorate RA in clinically severe and drug-resistant patients.

Autoantibodies in Rheumatoid Arthritis: Historical Background and Novel Findings

Autoantibodies represent a hallmark of rheumatoid arthritis (RA), with the rheumatoid factor (RF) and antibodies against citrullinated proteins (ACPA) being the most acknowledged ones. RA patients who are positive for RF and/or ACPA ("seropositive") in general display a different etiology and disease course compared to so-called "seronegative" patients. Still, the seronegative patient population is very heterogeneous and not well characterized. Due to the identification of new autoantibodies and advancements in the diagnosis of rheumatic diseases in the last years, the group of seronegative patients is constantly shrinking. Aside from antibodies towards various post-translational modifications, recent studies describe autoantibodies targeting some native proteins, further broadening the spectrum of recognized antigens. Next to the detection of new autoantibody groups, much research has been done to answer the question if and how autoantibodies contribute to the pathogenesis of RA. Since autoantibodies can be detected years prior to RA onset, it is a matter of debate whether their presence alone is sufficient to trigger the disease. Nevertheless, there is gathering evidence of direct autoantibody effector functions, such as stimulation of osteoclastogenesis and synovial fibroblast migration in in vitro experiments. In addition, autoantibody positive patients display a worse clinical course and stronger radiographic progression. In this review, we discuss current findings regarding different autoantibody types, the underlying disease-driving mechanisms, the role of Fab and Fc glycosylation and clinical implications.

Evolution of anti-modified protein antibody responses can be driven by consecutive exposure to different post-translational modifications

Background

Besides anti-citrullinated protein antibodies (ACPA), rheumatoid arthritis patients (RA) often display autoantibody reactivities against other post-translationally modified (PTM) proteins, more specifically carbamylated and acetylated proteins. Immunizing mice with one particular PTM results in an anti-modified protein antibody (AMPA) response recognizing different PTM-antigens. Furthermore, human AMPA, isolated based on their reactivity to one PTM, cross-react with other PTMs. However, it is unclear whether the AMPA-reactivity profile is “fixed” in time or whether consecutive exposure to different PTMs can shape the evolving AMPA response towards a particular PTM.

Methods

Longitudinally collected serum samples of 8 human individuals at risk of RA and 5 with early RA were tested with ELISA, and titers were analyzed to investigate the evolution of the AMPA responses over time. Mice (13 per immunization group in total) were immunized with acetylated (or carbamylated) protein (ovalbumin) twice or cross-immunized with an acetylated and then a carbamylated protein (or vice versa) and their serum was analyzed for AMPA responses.

Results

Human data illustrated dynamic changes in AMPA-reactivity profiles in both individuals at risk of RA and in early RA patients. Mice immunized with either solely acetylated or carbamylated ovalbumin (AcOVA or CaOVA) developed reactivity against both acetylated and carbamylated antigens. Irrespective of the PTM-antigen used for the first immunization, a booster immunization with an antigen bearing the other PTM resulted in increased titers to the second/booster PTM. Furthermore, cross-immunization skewed the overall AMPA-response profile towards a relatively higher reactivity against the “booster” PTM.

Conclusions

The relationship between different reactivities within the AMPA response is dynamic. The initial exposure to a PTM-antigen induces cross-reactive responses that can be boosted by an antigen bearing this or other PTMs, indicating the formation of cross-reactive immunological memory. Upon subsequent exposure to an antigen bearing another type of PTM, the overall reactivity pattern can be skewed towards better recognition of the later encountered PTM. These data might explain temporal differences in the AMPA-response profile and point to the possibility that the PTM responsible for the initiation of the AMPA response may differ from the PTM predominantly recognized later in time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02687-5.

The current status of anti-citrullinated protein antibodies and citrullinated protein-reactive B cells in the pathogenesis of rheumatoid arthritis

Anti-citrullinated protein antibodies are a hallmark of rheumatoid arthritis. It is widely acknowledged that the presence of ACPAs is the result of the interaction of genes, the environment and epigenetic modifications. The mechanism by which the factors, especially citrullination and ACPA glycosylation, affect ACPAs is still unclear. In this article, we review the presence of the ACPAs in RA and their relationship with clinical manifestations. The pathogenicity of ACPAs and B cells in RA was also summarized. A growing body of evidence has shown that ACPA-positive patients have more serious bone erosion and destruction and poor clinical prognosis than ACPA-negative patients. Recently, with the direct study of citrullinated protein-reactive B cells, their role in the development of rheumatoid arthritis has been further understood. It indicates that further understanding of the mechanism of ACPAs and CP-reactive B cells would beneficial in the prevention and treatment of RA.

Checkpoint Inhibitor-Associated Arthritis: A Systematic Review of Case Reports and Case Series

OBJECTIVE

We performed a systematic literature review to identify all reports of immune checkpoint inhibitor-associated inflammatory arthritis to describe it phenotypically and serologically.

METHODS

PubMed, Embase, and Cochrane databases were searched for reports of musculoskeletal immune-related adverse events secondary to ICI treatment. Publications were included if they provided individual patient level data regarding the pattern of joint involvement. Descriptive statistics were used to summarize results.

RESULTS

A total of 4339 articles were screened, of which 67 were included, encompassing 372 patients. The majority of patients had metastatic melanoma (57%), and they were treated with anti-PD1 or anti-PDL1 therapy (78%). Median time to onset of arthritis was 4 months (range, 1 day to 53 months). Forty-nine percent had polyarthritis, 17% oligoarthritis, 3% monoarthritis, 10% arthralgia, and 21% polymyalgia rheumatica. More than half of patients were described as having a "rheumatoid arthritis-like" presentation. Nine percent tested positive for rheumatoid factor or anti-cyclic citrullinated peptide antibodies. Seventy-four percent required corticosteroids, and 45% required additional medications. Sixty-three percent achieved arthritis control, and 32% were ultimately able to discontinue antirheumatic treatments. Immune checkpoint inhibitors were continued in 49%, transiently withheld in 11%, and permanently discontinued due to musculoskeletal immune-related adverse events in 13%.

CONCLUSIONS

Half of reported immune checkpoint inhibitor-associated arthritis cases present with polyarthritis (often RA-like), but only 9% are seropositive. Polymyalgia rheumatica is also common. Most patients respond to steroids alone, but about half require additional medications. Further studies are needed to determine long-term musculoskeletal outcomes in these patients, and the impact of arthritis treatment on cancer survival.

Functional disability to evaluate the risk of arthritis in First-degree relatives of Rheumatoid Arthritis patients

OBJECTIVE

The events that occur prior to the onset of rheumatoid arthritis (RA) continue to be delineated. We examined the relationship between self-reported joint symptoms, functional disability, and anticitrullinated protein antibody (ACPA) status in a cohort of first-degree relatives (FDR) of RA patients who are at risk of future disease development.

METHODS

We studied a cohort of 607 FDR of First Nations (FN) RA patients who are at increased risk for future RA development, and analyzed data collected at their enrollment study visit. In parallel, we analyzed data from 279 FN People with no family history of RA. A subset of FDR developed inflammatory arthritis and we analyzed longitudinal data in this group.

RESULTS

The prevalence of joint symptoms and functional disability was higher in FDR compared to non- FDR (all p<0.001). Difficulty walking (37.3% vs 18.0%) and mHAQ were higher in ACPA positive FDR compared to ACPA negative FDR, and mHAQ was independently associated with ACPA seropositivity (OR: 2.79, 1.56-5.00). Longitudinally, in individuals who developed ACPA+ RA, ACPA level and mHAQ score were significantly associated (R = 0.43, p< 0.001) in the preclinical period.

CONCLUSION

Compared to population-based controls, FDR have a high burden of joint symptoms and functional disability. Functional disability was most closely associated with ACPA seropositivity in the FDR, suggesting a direct role for ACPA outside of the context of clinically detectable synovitis. mHAQ appears to be particularly valuable in the assessment of individuals at risk for future RA development.

Identification of a Novel Serological Marker in Seronegative Rheumatoid Arthritis Using the Peptide Library Approach

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation mainly affecting the joints leading to cartilage and bone destruction. The definition of seropositive or seronegative RA is based on the presence or absence of rheumatoid factor (RF) and anti-citrullinated peptide antibodies (ACPAs). Other autoantibodies have been identified in the last decade such as antibodies directed against carbamylated antigens, peptidyl-arginine deiminase type 4 and v-Raf murine sarcoma viral oncogene homologue B. In order to identify relevant autoantigens, we screened a random peptide library (RPL) with pooled IgGs obtained from 50 patients with seronegative RA. Patients’ sera were then used in an ELISA test to identify the most frequently recognized peptide among those obtained by screening the RPL. Sera from age- and sex-matched healthy subjects were used as controls. We identified a specific peptide (RA-peptide) recognized by RA patients’ sera, but not by healthy subjects or by patients with other immune-mediated diseases. The majority of sera from seronegative and seropositive RA patients (73.8% and 63.6% respectively) contained IgG antibodies directed against the RA-peptide. Interestingly, this peptide shares homology with some self-antigens, such as Protein-tyrosine kinase 2 beta, B cell scaffold protein, Liprin-alfa1 and Cytotoxic T lymphocyte protein 4. Affinity purified anti-RA-peptide antibodies were able to cross react with these autoantigens. In conclusion, we identified a peptide that is recognized by seropositive and, most importantly, by seronegative RA patients’ sera, but not by healthy subjects, conferring to this epitope a high degree of specificity. This peptide shares also homology with other autoantigens which can be recognized by autoantibodies present in seronegative RA sera. These newly identified autoantibodies, although present also in a percentage of seropositive RA patients, may be considered as novel serum biomarkers for seronegative RA, which lacks the presence of RF and/or ACPAs.

Antibody Responses to Epstein-Barr Virus in the Preclinical Period of Rheumatoid Arthritis Suggest the Presence of Increased Viral Reactivation Cycles

OBJECTIVE

Patients with established rheumatoid arthritis (RA) demonstrate altered immune responses to Epstein-Barr virus (EBV), but the presence and role(s) of EBV have not been fully explored in the preclinical period. We hypothesized that EBV infection, as evidenced by an altered anti-EBV antibody response, could either play an important role in driving the development or be a result of expanded RA-related autoimmunity.

METHODS

83 subjects with RA based on 1987 ACR criteria and 83 matched controls were evaluated. Subject and matched control sera from the pre and post- RA diagnosis periods were tested for 5 anti-EBV antibodies (EBNA-1-IgG, VCA-IgG, EA-IgG, VCA-IgA, and EA-IgA), 7 RA-related autoantibodies (RF-neph, RF-IgA, RF-IgM, RF-IgG, CCP2, CCP3, CCP3.1), 22 cytokine/chemokine, 36 individual APCAs, and CMV-IgG antibodies. Random forest classification, mixed and joint mixed modelling were used to determine differences in anti-EBV antibodies between RA cases and controls.

RESULTS

Random Forest analysis identified preclinical EBV antibodies that differentiate RA subjects from controls. Specifically, EA-IgG antibody levels are higher in RA cases (0.82 ± 0.72) compared to controls (0.49 ± 0.28). Elevations in EA-IgG levels significantly correlated with increasing RF-IgM levels in future RA cases (p = 0.007) but not in controls (p = 0.150). CMV-IgG antibody levels did not differ between groups.

CONCLUSION

Subjects who eventually develop classified RA demonstrate elevated EA-IgG antibody levels in the preclinical period, which suggests the presence of increased EBV re-activation cycles. A combination of RF and EBV reactivation may play an important role in the development of RA.

"Ways in which the neonatal Fc-receptor is involved in autoimmunity"

Since the neonatal IgG Fc receptor (FcRn) was discovered, its role has evolved from immunoglobulin recycling and biodistribution to antigen presentation and immune complex routing, bringing it to the center of both humoral and cellular immune responses. FcRn is thus involved in the pathophysiology of immune-related diseases such as cancer, infection, and autoimmune disorders. This review focuses on the role of FcRn in autoimmunity, based on the available data from both animal models and human studies. The knowledge concerning ways in which FcRn is involved in autoimmune response has led to the development of inhibitors for the treatment of autoimmune diseases, also described here. Up to date, the literature remains scarce, shedding light on the need for further studies to fully understand the various pathophysiological roles of this unique receptor.

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FcRn is an intracellular receptor with a key role in IgG and immune complex management.

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FcRn-targeting therapies are a promising way of treatment in antibodies mediated diseases.

PADI2 Polymorphisms Are Significantly Associated With Rheumatoid Arthritis, Autoantibodies Serologic Status and Joint Damage in Women from Southern Mexico

The enzymes of the family peptidylarginine deiminases (PADs) have an important role in the pathogenesis of rheumatoid arthritis (RA) due to their association with the anti-citrullinated protein antibodies (ACPA) production. To evaluate the association between single-nucleotide polymorphisms (SNPs) in the PADI2 gene and RA susceptibility, related clinical parameters, and the serologic status of autoantibodies in a women population with RA from southern Mexico, a case-control study was conducted (case n=229; control n=333). Sociodemographic characteristics were evaluated, along with clinical parameters, inflammation markers, the levels of ACPAs as anti-cyclic citrullinated peptides (anti-CCPs), anti-modified citrullinated vimentin (anti-MCV), and rheumatoid factor (RF). Genomic DNA was extracted from peripheral blood, and three SNPs of the PADI2 gene (rs1005753, rs2057094, and rs2235926) were performed by qPCR using TaqMan probes. The data analysis reveals that the carriers of the T allele for rs2057094 and rs2235926 presented an earlier onset of the disease (β= -3.26; p = 0.03 and β = -4.13; p = 0.015, respectively) while the carriers of the T allele for rs1005753 presented higher levels of anti-CCPs (β= 68.3; p = 0.015). Additionally, the T allele of rs2235926 was associated with a positive RF (OR = 2.90; p = 0.04), anti-MCV (OR = 2.92; p = 0.05), and with the serologic status anti-CCP+/anti-MCV+ (OR = 3.02; p = 0.03), and anti-CCP+/anti-MCV+/RF+ (OR = 3.79; p = 0.004). The haplotypes GTT (OR =1.52; p = 0.027) and TTT (OR = 1.32; p = 0.025) were associated with the presence of RA. In addition, in this study the haplotype TTT is linked to the presence of radiographic joint damage defined by a Sharp-van der Heijde score (SHS) ≥2 (OR = 1.97; p = 0.0021) and SHS ≥3 (OR = 1.94; p = 0.011). The haplotype TTT of SNPs rs1005753, rs2057094, and rs2235926 of the PADI2 gene confers genetic susceptibility to RA and radiographic joint damage in women from southern Mexico. The evidence reveals that SNPs of the PADI2 gene favors the presence of a positive serologic status in multiple autoantibodies and the clinical manifestations of RA at an early onset age.

Lung inflammation, NETosis and the pulmonary initiation of ACPA response: What came first, the chicken or the egg?

Multiple recent lines of evidence suggest that, at least in some patients, RA-associated autoimmunity and inflammation may originate in the lung (1, 2). However, what exactly is/are the initiating event(s), and the sequence of subsequent events, is not fully defined. In this issue of A&R, Okumoto et al (insert new reference), make the intriguing finding that individuals at risk of developing RA have an increased spontaneous neutrophil extracellular trap (NET) formation in sputum, in particular NETs containing citH3, and that these levels associate with presence of IgA ACPA. Such evidence has previously been reported, but the new data presented begins to paint a somewhat revised and enhanced storyline by investigating the pathway of mediation underlying these associations.

Towards prevention of autoimmune diseases: The example of rheumatoid arthritis

Prevention is the ultimate aim for clinicians and scientists concerned with severe diseases, like many immune-mediated conditions. Here, we describe recent progress in the understanding of etiology and molecular pathogenesis of rheumatoid arthritis (RA), which make this disease a potential prototype for prevention that may include both public health measures and targeted and personalized approaches that we call "personalized prevention." Critical components of this knowledge are (i) better understanding of the dynamics of the RA-associated autoimmunity that may begin many years before onset of joint inflammation; (ii) insights into how this immunity may be triggered at mucosal surfaces after distinct environmental challenges; (iii) better understanding of which features of the pre-existing immunity may cause symptoms that precede joint inflammation and predict a high risk for imminent arthritis development; and (iv) how molecular events occurring before onset of inflammation might be targeted by existing or future therapies, ultimately by specific targeting of Major histocompatibility complex (MHC) class II restricted and RA-specific immunity. Our main conclusion is that studies and interventions in the phase of autoimmunity preceding RA offer new opportunities to prevent the disease and thereby also understand the molecular pathogenesis of its different variants.

Association between number and type of different ACPA fine specificities with lung abnormalities in early, untreated rheumatoid arthritis

Background

Rheumatoid arthritis (RA)-associated anticitrullinated protein/peptide antibodies (ACPA) might originate at mucosal sites such as the lungs. We aimed to examine the relationship between the ACPA repertoire and lung abnormalities on high-resolution CT (HRCT) in patients with earlyuntreated RA.

Methods

106 patients with newly diagnosed untreated RA were examined with HRCT of the lungs. Blood samples were analysed for presence of rheumatoid factor (RF) and ACPA using either a CCP2 detection kit or an immunochip containing 10 different citrullinated peptides. Association between HRCT findings and the antibody repertoire was assessed by logistic regression analysis.

Results

The number (%) of patients with HRCT abnormalities was 58 (54.7%) for parenchymal abnormalities and 68 (64.2%) for airway abnormalities. CCP2 IgG, RF IgA and antibodies against citrullinated fibrinogen were associated with the presence of parenchymal lung abnormalities. Interestingly, a high number of ACPA fine specificities gave a high risk of having parenchymal lung abnormalities at the time of RA diagnosis. No significant signals were identified between ACPA specificities and risk for airway abnormalities.

Conclusions

The presence of RF and ACPAs (especially against citrullinated fibrinogen peptides) as well as high number of ACPAs fine specificities are associated with parenchymal lung abnormalities in patients with early, untreated RA. This provides further support for an important pathogenic link between the lung and systemic autoimmunity, contributing to RA development.

Risk Factors for Developing Rheumatoid Arthritis in Patients With Undifferentiated Arthritis and Inflammatory Arthralgia

Currently, there is an increasing interest in treating patients at risk of rheumatoid arthritis (RA) to prevent the development of this chronic disease. In this sense, research has focused attention on the early identification of predictive factors of this disease. Autoantibodies and markers of systemic inflammation can be present before clinical arthritis and RA development. So, the phase of inflammatory arthralgia preceding clinical arthritis is an important part of the window of opportunity and, starting treatment might prevent progression to chronic arthritis. Additionally, the early diagnosis and treatment initiation, in patients with inflammatory arthritis at risk of persistence and/or erosive progression, are fundamental because may allow optimal clinical responses, better chances of achieving sustained remission, preventing irreversible organ damage and optimizing long-term outcomes. This review aims to give an overview of clinical risk factors for developing RA, both in suspected arthralgia and in undifferentiated arthritis. Besides taking into consideration the role of serological markers (immunological and acute phase reactants) and clinical features assessed at consultation such as: articular affection and patient's clinical perception. Other features as sociodemographic and environmental factors (lifestyle habits, microbiota, periodontal disease among others), have been included in this revision to give an insight on strategies to prevent development of RA and/or to treat it in early stages.

Testing the Effects of Disease-Modifying Antirheumatic Drugs on Vascular Inflammation in Rheumatoid Arthritis: Rationale and Design of the TARGET Trial

Individuals with rheumatoid arthritis (RA) are at increased risk for atherosclerotic cardiovascular disease (ASCVD) events relative to the general population, potentially mediated by atherosclerotic plaques that are more inflamed and rupture prone. We sought to address whether RA immunomodulators reduce vascular inflammation, thereby reducing ASCVD risk, and whether such reduction depends on the type of immunomodulator. The TARGET (Treatments Against RA and Effect on 18-Fluorodeoxyglucose [18 F-FDG] Positron Emission Tomography [PET]/Computed Tomography [CT]) trial (NCT02374021) will enroll 150 patients with RA with active disease and an inadequate response to methotrexate. Participants will be randomized to add either a tumor necrosis factor (TNF) inhibitor (etanercept or adalimumab) or sulfasalazine and hydroxychloroquine to their background methotrexate. Participants will undergo full-body 18 F-FDG-labelled PET scanning at baseline and after 6 months. Efficacy and safety evaluations will occur every 6 weeks, with therapy modified in a treat-to-target approach. The primary outcome is the comparison of change in arterial inflammation in the wall of the aorta and carotid arteries between the randomized treatment groups, specifically, the change in the mean of the maximum target-to-background ratio of arterial 18 F-FDG uptake in the most diseased segment of either the aorta and carotid arteries. A secondary analysis will compare the effects of achieving low disease activity or remission with those of moderate to high disease activity on vascular inflammation. The TARGET trial will test, for the first time, whether RA treatments reduce arterial inflammation and whether such reduction differs according to treatment strategy with either TNF inhibitors or a combination of nonbiologic disease-modifying antirheumatic drugs.

The Expression of Non-Coding RNAs and Their Target Molecules in Rheumatoid Arthritis: A Molecular Basis for Rheumatoid Pathogenesis and Its Potential Clinical Applications

Rheumatoid arthritis (RA) is a typical autoimmune-mediated rheumatic disease presenting as a chronic synovitis in the joint. The chronic synovial inflammation is characterized by hyper-vascularity and extravasation of various immune-related cells to form lymphoid aggregates where an intimate cross-talk among innate and adaptive immune cells takes place. These interactions facilitate production of abundant proinflammatory cytokines, chemokines and growth factors for the proliferation/maturation/differentiation of B lymphocytes to become plasma cells. Finally, the autoantibodies against denatured immunoglobulin G (rheumatoid factors), EB virus nuclear antigens (EBNAs) and citrullinated protein (ACPAs) are produced to trigger the development of RA. Furthermore, it is documented that gene mutations, abnormal epigenetic regulation of peptidylarginine deiminase genes 2 and 4 (PADI2 and PADI4), and thereby the induced autoantibodies against PAD2 and PAD4 are implicated in ACPA production in RA patients. The aberrant expressions of non-coding RNAs (ncRNAs) including microRNAs (miRs) and long non-coding RNAs (lncRNAs) in the immune system undoubtedly derange the mRNA expressions of cytokines/chemokines/growth factors. In the present review, we will discuss in detail the expression of these ncRNAs and their target molecules participating in developing RA, and the potential biomarkers for the disease, its diagnosis, cardiovascular complications and therapeutic response. Finally, we propose some prospective investigations for unraveling the conundrums of rheumatoid pathogenesis.

Neutrophil extracellular trap-associated molecules: a review on their immunophysiological and inflammatory roles

Neutrophil extracellular traps (NETs) are a defense mechanism against pathogens. They are composed of DNA and various proteins and have the ability to hinder microbial spreading and survival. However, NETs are not only related to infections but also participate in sterile inflammatory events. In addition to DNA, NETs contain histones, serine proteases, cytoskeletal proteins and antimicrobial peptides, all of which have immunomodulatory properties that can augment or decrease the inflammatory response. Extracellular localization of these molecules alerts the immune system of cellular damage, which is triggered by recognition of damage-associated molecular patterns (DAMPs) through specific pattern recognition receptors. However, not all of these molecules are DAMPs and may have other immunophysiological properties in the extracellular space. The release of NETs can lead to production of pro-inflammatory cytokines (due to TLR2/4/9 and inflammasome activation), the destruction of the extracellular matrix, activation of serine proteases and of matrix metallopeptidases (MMPs), modulation of cellular proliferation, induction of cellular migration and adhesion, promotion of thrombogenesis and angiogenesis and disruption of epithelial and endothelial permeability. Understanding the dynamics of NET-associated molecules, either individually or synergically, will help to unravel their role in inflammatory events and open novel perspectives for potential therapeutic targets. We here review molecules contained within NETS and their immunophysiological roles.

Potential role of bioactive lipids in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, which involves a pathological inflammatory response against articular cartilage in multiple joints throughout the body. It is a complex disorder associated with comorbidities such as depression, lymphoma, osteoporosis and cardiovascular disease (CVD), which significantly deteriorate patients' quality of life and prognosis. This has ignited a large initiative to elucidate the physiopathology of RA, aiming to identify new therapeutic targets and approaches in its multidisciplinary management. Recently, various lipid bioactive products have been proposed to have an essential role in this process; including eicosanoids, specialized pro-resolving mediators, phospholipids/sphingolipids, and endocannabinoids. Dietary interventions using omega-3 polyunsaturated fatty acids or treatment with synthetic endocannabinoids agonists have been shown to significantly ameliorate RA symptoms. Indeed, the modulation of lipid metabolism may be crucial in the pathophysiology and treatment of autoimmune diseases.

A Comprehensive Evaluation of the Relationship Between Different IgG and IgA Anti-Modified Protein Autoantibodies in Rheumatoid Arthritis

Seropositive rheumatoid arthritis (RA) is characterized by the presence of rheumatoid factor (RF) and anti-citrullinated protein autoantibodies (ACPA) with different fine-specificities. Yet, other serum anti-modified protein autoantibodies (AMPA), e.g. anti-carbamylated (Carb), -acetylated (KAc), and malondialdehyde acetaldehyde (MAA) modified protein antibodies, have been described. In this comprehensive study, we analyze 30 different IgG and IgA AMPA reactivities to Cit, Carb, KAc, and MAA antigens detected by ELISA and autoantigen arrays in N=1985 newly diagnosed RA patients. Association with patient characteristics such as smoking and disease activity were explored. Carb and KAc reactivities by different assays were primarily seen in patients also positive for anti-citrulline reactivity. Modified vimentin (mod-Vim) peptides were used for direct comparison of different AMPA reactivities, revealing that IgA AMPA recognizing mod-Vim was mainly detected in subsets of patients with high IgG anti-Cit-Vim levels and a history of smoking. IgG reactivity to acetylation was mainly detected in a subset of patients with Cit and Carb reactivity. Anti-acetylated histone reactivity was RA-specific and associated with high anti-CCP2 IgG levels, multiple ACPA fine-specificities, and smoking status. This reactivity was also found to be present in CCP2+ RA-risk individuals without arthritis. Our data further demonstrate that IgG autoreactivity to MAA was increased in RA compared to controls with highest levels in CCP2+ RA, but was not RA-specific, and showed low correlation with other AMPA. Anti-MAA was instead associated with disease activity and was not significantly increased in CCP2+ individuals at risk of RA. Notably, RA patients could be subdivided into four different subsets based on their AMPA IgG and IgA reactivity profiles. Our serology results were complemented by screening of monoclonal antibodies derived from single B cells from RA patients for the same antigens as the RA cohort. Certain CCP2+ clones had Carb or Carb+KAc+ multireactivity, while such reactivities were not found in CCP2- clones. We conclude that autoantibodies exhibiting different patterns of ACPA fine-specificities as well as Carb and KAc reactivity are present in RA and may be derived from multireactive B-cell clones. Carb and KAc could be considered reactivities within the "Cit-umbrella" similar to ACPA fine-specificities, while MAA reactivity is distinctly different.

Microbiome-miRNA interactions in the progress from undifferentiated arthritis to rheumatoid arthritis: evidence, hypotheses, and opportunities

The human microbiome has attracted attention for its potential utility in precision medicine. Increasingly, more researchers are recognizing changes in intestinal microbiome can upset the balance between pro- and anti-inflammatory factors of host immune system, potentially contributing to arthritis immunopathogenesis. Patients who develop rheumatoid arthritis from undifferentiated arthritis can face multiple irreversible joint lesions and even deformities. Strategies for identifying undifferentiated arthritis patients who have a tendency to develop rheumatoid arthritis and interventions to prevent rheumatoid arthritis development are urgently needed. Intestinal microbiome dysbiosis and shifts in the miRNA profile affect undifferentiated arthritis progression, and may play an important role in rheumatoid arthritis pathophysiologic process via stimulating inflammatory cytokines and disturbing host and microbial metabolic functions. However, a causal relationship between microbiome–miRNA interactions and rheumatoid arthritis development from undifferentiated arthritis has not been uncovered yet. Changes in the intestinal microbiome and miRNA profiles of undifferentiated arthritis patients with different disease outcomes should be studied together to uncover the role of the intestinal microbiome in rheumatoid arthritis development and to identify potential prognostic indicators of rheumatoid arthritis in undifferentiated arthritis patients. Herein, we discuss the possibility of microbiome–miRNA interactions contributing to rheumatoid arthritis development and describe the gaps in knowledge regarding their influence on undifferentiated arthritis prognosis that should be addressed by future studies.

Elevated Anti-Citrullinated Protein Antibodies Prior to Rheumatoid Arthritis Diagnosis and Risks for Chronic Obstructive Pulmonary Disease or Asthma

OBJECTIVE

To investigate elevation of anti-citrullinated protein antibodies (ACPAs) before diagnosis of rheumatoid arthritis (RA) and risks for chronic obstructive pulmonary disease (COPD) or asthma.

METHODS

We performed a matched cohort study nested within the Nurses' Health Studies among women who donated blood. Women with incident RA after blood draw (self-reported, then confirmed by medical records) were each matched to 3 controls by age, cohort, year, and menopausal factors. Pre-RA ACPA positivity was defined as >99th percentile of control distribution by a research assay or by cyclic citrullinated peptide in a subset. Incident COPD and asthma after index date (date of blood draw) were identified by questionnaires. Cox regression estimated hazard ratios (HRs) for incident COPD or asthma (in separate analyses) associated with pre-RA, pre-RA ACPA+, or pre-RA ACPA- phenotypes each compared to their matched non-RA controls.

RESULTS

We analyzed 283 women who were pre-RA and 842 controls; blood was donated a mean ± SD of 9.7 ± 5.8 years before RA diagnosis. Fifty-nine women (20.8%) were pre-RA ACPA+. There were 107 cases of incident COPD and 105 incident asthma cases during 21,489 person-years of follow-up. Pre-RA ACPA+ was associated with increased COPD risk (HR 3.04 [95% confidence interval (95% CI) 1.33-7.00]) after adjusting for covariates including smoking pack-years. Pre-RA ACPA+ had an HR for asthma of 1.74 (multivariable 95% CI 0.72-4.24), similar to the risk of asthma for pre-RA ACPA- (HR 1.65 [95% CI 1.11-2.46]).

CONCLUSION

Women with elevated ACPA before RA diagnosis had increased risk for developing COPD compared to controls. Women who later developed RA were more likely to develop asthma than controls, regardless of pre-RA ACPA status.

Circulating anti-citrullinated protein antibodies containing secretory component are prognostic for arthritis onset in at-risk patients

Autoantibodies related to rheumatoid arthritis (RA), such as anti‐citrullinated protein antibodies (ACPA), are often detectable in the preclinical period years before arthritis onset. However, events triggering arthritis development remain incompletely known. We aimed to determine whether ACPA isotype levels are prognostic for arthritis development in patients presenting with immunoglobulin (Ig)G ACPA and musculoskeletal pain. Study participants (n = 82) had musculoskeletal pain of any sort and duration and a positive IgG ACPA test. None of the patients had arthritis upon clinical examination at baseline, but during follow‐up (mean = 6 years), 48% developed at least one arthritic joint. IgG, IgA, IgM and secretory component (SC)‐containing ACPA was measured in longitudinally collected serum samples. Cox regression analysis was performed to test the prognostic value of baseline antibody levels and changes over time. All analysed ACPA isotype levels were associated with arthritis development in univariable Cox regression analysis. In multivariable analysis, baseline SC ACPA levels were independently prognostic for arthritis development in multivariable analysis [hazard ratio (HR) = 1·006, 95% confidence interval (CI) = 1·001–1·010, P = 0·012]. There were no significant changes in ACPA isotype levels over time, and no significant association between changes over time and arthritis development. In this prospective longitudinal study, baseline serum SC ACPA levels, but neither IgG, IgA nor IgM ACPA are prognostic for future arthritis development. Repeated measurement of ACPA isotypes do not bring additional prognostic value. The results reinforce a mucosal connection in RA development and encourage further exploration of the mechanisms underlying secretory ACPA formation as a trigger for arthritis development.

Why remission is not enough: underlying disease mechanisms in RA that prevent cure

Cure is the aspirational aim for the treatment of all diseases, including chronic inflammatory conditions such as rheumatoid arthritis (RA); however, it has only been during the twenty-first century that remission, let alone cure, has been a regularly achievable target in RA. Little research has been carried out on how to cure RA, and the term 'cure' still requires definition for this disease. Even now, achieving a cure seems to be a rare occurrence among individuals with RA. Therefore, this Review is aimed at addressing the obstacles to the achievement of cure in RA. The differences between remission and cure in RA are first defined, followed by a discussion of the underlying factors (referred to as drivers) that prevent the achievement of cure in RA by triggering sustained immune activation and effector cytokine production. Such drivers include adaptive immune system activation, mesenchymal tissue priming and so-called 'remote' (non-immune and non-articular) factors. Strategies to target these drivers are also presented, with an emphasis on the development of strategies that could complement currently used cytokine inhibition and thereby improve the likelihood of curing RA.

Biglycan expression and its function in human ligamentum flavum

Hypertrophy of the ligamentum flavum (LF) is a major cause of lumbar spinal stenosis (LSS), and the pathology involves disruption of elastic fibers, fibrosis with increased cellularity and collagens, and/or calcification. Previous studies have implicated the increased expression of the proteoglycan family in hypertrophied LF. Furthermore, the gene expression profile in a rabbit experimental model of LF hypertrophy revealed that biglycan (BGN) is upregulated in hypertrophied LF by mechanical stress. However, the expression and function of BGN in human LF has not been well elucidated. To investigate the involvement of BGN in the pathomechanism of human ligamentum hypertrophy, first we confirmed increased expression of BGN by immunohistochemistry in the extracellular matrix of hypertrophied LF of LSS patients compared to LF without hypertrophy. Experiments using primary cell cultures revealed that BGN promoted cell proliferation. Furthermore, BGN induces changes in cell morphology and promotes myofibroblastic differentiation and cell migration. These effects are observed for both cells from hypertrophied and non-hypertrophied LF. The present study revealed hyper-expression of BGN in hypertrophied LF and function of increased proteoglycan in LF cells. BGN may play a crucial role in the pathophysiology of LF hypertrophy through cell proliferation, myofibroblastic differentiation, and cell migration.

Association of Agricultural, Occupational, and Military Inhalants With Autoantibodies and Disease Features in US Veterans With Rheumatoid Arthritis

OBJECTIVE

To determine the association of inhalant exposures with rheumatoid arthritis (RA)-related autoantibodies and severity in US veterans.

METHODS

Participants in the Veterans Affairs Rheumatoid Arthritis (VARA) registry were mailed surveys assessing occupational, agricultural, and military inhalant exposures. Demographic characteristics, disease activity, functional status, and extraarticular features were obtained from the VARA registry, while HLA-DRB1 shared epitope (SE) status, anti-cyclic citrullinated peptide (anti-CCP) antibodies, and rheumatoid factor (RF) were measured using banked DNA/serum from enrollment. Associations between inhalant exposures and RA-related factors (autoantibodies, severity, and extraarticular features) were assessed using multivariable linear and logistic regression models adjusted for age, sex, race, and tobacco use and stratified by SE status. Adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

RESULTS

Questionnaires were returned by 797 of 1,566 participants (50.9%). Survey respondents were older, more often White or male, and less frequently smokers, and had lower disease activity compared to nonrespondents. Anti-CCP positivity was more common among veterans exposed to burn pits (OR 1.66 [95% CI 1.02, 2.69]) and military waste disposal (OR 1.74 [95% CI 1.04, 2.93]) independent of other factors. Among participants who were positive for SE alleles, burn pit exposure (OR 5.69 [95% CI 2.73, 11.87]) and military waste disposal exposure (OR 5.05 [95% CI 2.42, 10.54]) were numerically more strongly associated with anti-CCP positivity. Several inhalant exposures were associated with the presence of chronic lung disease, but not with the presence of RF or the level of disease activity.

CONCLUSION

Military burn pit exposure and military waste disposal exposure were independently associated with the presence of anti-CCP antibodies in RA patients. These findings are consistent with emerging evidence that various inhalant exposures influence autoantibody expression and RA risk.

Insights of rheumatoid arthritis biomarkers

Rheumatoid arthritis is a chronic, autoimmune connective tissue disease. In addition to joint involvement, extra-articular changes and organ complications also occur in the course of the disease. Untreated disease leads to disability and premature death. Therefore, it is important to recognise and begin treatment early. Based on the presence of rheumatoid factor and antibodies against citrullinated peptides, we can distinguish two forms of the disease: seropositive and seronegative. Research continues to elucidate the mechanisms of the onset of the disease, as well as to uncover factors that induce and influence the activity of the disease. The presence of markers that initially appear and affect the course of the disease can potentially aid in patient treatment. In this article, we have collected biomarkers of rheumatoid arthritis that are well understood as well as those that have been recently described.

Expansion of Alternative Autoantibodies Does Not Follow the Evolution of Anti-Citrullinated Protein Antibodies in Preclinical Rheumatoid Arthritis: An Analysis in At-Risk First Degree Relatives

OBJECTIVE

Co-occurrence of autoantibodies specific for ≥1 autoimmune disease is widely prevalent in rheumatoid arthritis (RA) patients. To understand the prevalence of polyautoimmunity in preclinical RA, we performed a comprehensive autoantibody assessment in a First Nations cohort of at-risk first-degree relatives (FDR) of RA patients, a subset of whom subsequently developed RA (progressors).

METHODS

Venous blood was collected from all study participants (n = 50 RA patients and 64 FDR) at scheduled visits, and serum was stored at -20°C. High-sensitivity C-reactive protein level, anti-citrullinated protein antibody (ACPA) status, and autoantibody status were determined using commercially available enzyme-linked immunosorbent assay kits. Rheumatoid factor (RF) was detected by nephelometry. Antinuclear autoantibodies (ANA) were identified using Hep-2 indirect immunofluorescence assay (IFA) and classified according to international consensus nomenclature as various anti-cell (AC) patterns.

RESULTS

Of our study cohort, 78.9% had positive ANA reactivity (≥1:80), which was either a homogenous, fine-speckled (AC-1 and AC-4) or mixed IFA pattern. Importantly, the AC-4 and mixed ANA patterns were also observed in progressors at the time of disease onset. While all of the RA patients showed a high prevalence of arthritis-associated autoantibodies, they also had a high prevalence of extractable nuclear antigen-positive autoantibodies to other autoantigens. In FDR, we did not observe any increase in serum autoreactivity to nonarthritis autoantigens, either cross-sectionally or in samples collected longitudinally from progressors prior to RA onset.

CONCLUSION

While alternative autoimmunity and ANA positivity are widely prevalent in First Nations populations, including asymptomatic, seronegative FDR, expansion of alternative autoimmunity does not occur in parallel with ACPA expansion in FDR and is restricted to patients with established RA.

Subjects at-risk for future development of rheumatoid arthritis demonstrate a PAD4-and TLR-dependent enhanced histone H3 citrullination and proinflammatory cytokine production in CD14hi monocytes

The presence of anti-citrullinated protein/peptide antibodies (ACPA) and epitope spreading across the target autoantigens is a unique feature of rheumatoid arthritis (RA). ACPA are present in the peripheral blood for several years prior to the onset of arthritis and clinical classification of RA. ACPA recognize multiple citrullinated proteins, including histone H3 (H3). Intracellular citrullination of H3 in neutrophils and T cells is known to regulate immune cell function by promoting neutrophil extracellular trap formation and citrullinated autoantigen release as well as regulating the Th2/Th17 T cell phenotypic balance. However, the roles of H3 citrullination in other immune cells are not fully elucidated. We aimed to explore H3 citrullination and cytokine/metabolomic signatures in peripheral blood immune cells from subjects prior to and after the onset of RA, at baseline and in response to ex vivo toll-like receptor (TLR) stimulation. Here, we analyzed 13 ACPA (+) subjects without arthritis but at-risk for future development of RA, 14 early RA patients, and 13 healthy controls. We found significantly elevated H3 citrullination in CD14hi monocytes, as well as CD1c+ dendritic cells and CD66+ granulocytes. Unsupervised analysis identified two distinct subsets in CD14hi monocytes characterized by H3 modification and unique cytokine/metabolomic signatures. CD14hi monocytes with elevated TLR-stimulated H3 citrullination were significantly increased in ACPA (+) at-risk subjects. These cells were skewed to produce TNFα, MIP1β, IFNα, and partially IL-12. Additionally, they demonstrate peptidyl arginine deiminase 4 (PAD4) mediated upregulation of the glycolytic enzyme PFKFB3. These CD14hi monocytes with elevated H3 citrullination morphologically formed monocyte extracellular traps (METs). Taken together, dysregulated PAD4-driven cytokine production as well as MET formation in CD14hi monocytes in ACPA (+) at-risk subjects likely plays an important role in the development of RA via promoting and perpetuating inflammation and generation of citrullinated autoantigens.

Rheumatoid Arthritis Pathogenesis, Prediction, and Prevention: An Emerging Paradigm Shift

Rheumatoid arthritis (RA) is currently diagnosed and treated when an individual presents with signs and symptoms of inflammatory arthritis (IA) as well as other features, such as autoantibodies and/or imaging findings, that provide sufficient confidence that the individual has RA-like IA (e.g., meeting established classification criteria) that warrants therapeutic intervention. However, it is now known that there is a stage of seropositive RA during which circulating biomarkers and other factors (e.g., joint symptoms) can be used to predict if and when an individual who does not currently have IA may develop future clinically apparent IA and classifiable RA. Indeed, the discovery of the "pre-RA" stage of seropositive disease has led to the development of several clinical trials in which individuals are studied to identify ways to delay or prevent the onset of clinically apparent IA/RA. This review focuses on several issues pertinent to understanding the prevention of RA. These include discussion of the pathogenesis of pre-RA development, prediction of the likelihood and timing of future classifiable RA, and a review of completed and ongoing clinical trials in RA prevention. Furthermore, this review discusses challenges and opportunities to be addressed to effect a paradigm shift in RA, where in the near future, proactive risk assessment focused on prevention of RA will become a public health strategy in much the same manner as cardiovascular disease is managed today.

Factors associated with progression to inflammatory arthritis in first-degree relatives of individuals with RA following autoantibody positive screening in a non-clinical setting

OBJECTIVES

Little is known about the likelihood of developing inflammatory arthritis (IA) in individuals who screen autoantibody positive (aAb+) in a non-clinical research setting.

METHODS

We screened for serum cyclic citrullinated peptide antibody (anti-CCP) and rheumatoid factor isotype aAbs in subjects who were at increased risk for rheumatoid arthritis (RA) because they are a first-degree relative of an individual with classified RA (n=1780). We evaluated combinations of aAbs and high titre aAbs, as defined by 2-times (2 x) the standard cut-off and an optimal cut-off, as predictors of our two outcomes, aAb+ persistence and incident IA.

RESULTS

304 subjects (17.1%) tested aAb+; of those, 131 were IA-free and had at least one follow-up visit. Sixty-four per cent of these tested aAb+ again on their next visit. Anti-CCP+ at levels ≥2 x the standard cut-off was associated with 13-fold higher likelihood of aAb +persistence. During a median of 4.4 years (IQR: 2.2-7.2), 20 subjects (15.3%) developed IA. Among subjects that screened anti-CCP+ at ≥ 2 x or ≥an optimal cut-off, 32% and 26% had developed IA within 5 years, respectively. Both anti-CCP cut-offs conferred an approximate fourfold increased risk of future IA (HR 4.09 and HR 3.95, p<0.01).

CONCLUSIONS

These findings support that aAb screening in a non-clinical setting can identify RA-related aAb+ individuals, as well as levels and combinations of aAbs that are associated with higher risk for future IA. Monitoring for the development of IA in aAb+ individuals and similar aAb testing approaches in at-risk populations may identify candidates for prevention studies in RA.

A bioavailable form of curcumin, in combination with vitamin-D- and omega-3-enriched diet, modifies disease onset and outcomes in a murine model of collagen-induced arthritis

OBJECTIVE

Curcumin (CUR), vitamin D₃ (D3), and omega-3-fatty acids (O3FA) individually modulate inflammation and pain in arthritis. Although these supplements are widely used, their combinatorial effects have not been defined. In this study, we examined the effects of a D3 and O3FA (VO)-enriched diet in conjunction with a highly bioavailable form of CUR (Cureit/Acumin™) in a collagen-induced arthritis (CIA) murine model.

METHODS

Male DBA/1J mice were acclimatized to VO-enriched diet and challenged with bovine collagen II (CII). Bioavailable CUR was administered daily by oral gavage from the onset of CII challenge. Disease severity was determined by monitoring joint thickness and standardized clinical score. Cellular infiltration and cartilage degradation in the joints were assessed by histology, serum cytokines profiled by Meso Scale Discovery multiplex assay, and joint matrix metalloproteinases examined by western blots.

RESULTS

CUR by itself significantly decreased disease severity by ~ 60%. Administration of CUR in CIA mice taking a VO-enriched diet decreased disease severity by > 80% and maximally delayed disease onset and progression. Some of the disease-modifying effects was mediated by CUR alone, e.g., suppression of serum anti-collagen antibodies and decrease of cellular infiltration and MMP abundance in the joints of CIA mice. Although CUR alone suppressed inflammatory cytokines in serum of CIA mice, the combination of CUR and VO diet significantly enhanced the suppression (> 2-fold compared to CUR) of TNF, IFN-γ, and MCP-1, all known to be associated with RA pathogenesis.

CONCLUSION

This study provides proof-of-concept that the combination of bioavailable CUR, vitamin D₃, and O3FA substantially delays the development and severity of CIA. These findings provide a rationale for systematically evaluating these widely available supplements in individuals at risk for developing future RA.

Relationship between natural and infection-induced antibodies in systemic autoimmune diseases (SAD): SLE, SSc and RA

Infection or vaccine-induced T cell-dependent immune response and the subsequent high-affinity neutralizing antibody production have been extensively studied, while the connection between natural autoantibodies (nAAbs) and disease-specific antibodies has not been thoroughly investigated. Our goal was to find the relationship between immunoglobulin (Ig)M and IgG isotype nAAbs and infection or vaccine-induced and disease-related autoantibody levels in systemic autoimmune diseases (SAD). A previously described indirect enzyme-linked immunosorbent assay (ELISA) test was used for detection of IgM/IgG nAAbs against citrate synthase (anti-CS) and F4 fragment (anti-F4) of DNA topoisomerase I in 374 SAD samples, with a special focus on systemic lupus erythematosus (SLE) (n = 92), rheumatoid arthritis (n = 73) and systemic sclerosis (n = 157) disease groups. Anti-measles IgG and anti-dsDNA IgG/IgM autoantibodies were measured using commercial and in-house indirect ELISA tests. In all SAD groups the anti-measles IgG-seropositive cases showed significantly higher anti-CS IgG titers (P = 0·011). In anti-dsDNA IgG-positive SLE patients, we detected significantly higher levels of anti-CS and anti-F4 IgG nAAbs (P = 0·001 and < 0·001, respectively). Additionally, we found increased levels of IgM isotypes of anti-CS and anti-F4 nAAbs in anti-dsDNA IgM-positive SLE patients (P = 0·002 and 0·016, respectively). The association between IgG isotypes of pathogen- or autoimmune disease-related antibodies and the IgG nAAbs may underscore the immune response-inducible nature of the diseases investigated. The relationship between protective anti-dsDNA IgM and the IgM isotype of anti-F4 and anti-CS may provide immunoserological evidence for the beneficial roles of nAAbs in SLE patients.

Association of a Serum Protein Signature With Rheumatoid Arthritis Development

OBJECTIVE

The pathophysiologic events that precede the onset of rheumatoid arthritis (RA) remain incompletely understood. This study was undertaken to identify changes in the serum proteome that precede the onset of RA, with the aim of providing new insights into the pathogenic mechanisms that lead to its development.

METHODS

In a cohort of first-degree relatives of Indigenous North American RA patients, the SomaScan proteomics platform was used to determine the levels of 1,307 proteins in multiple longitudinal serum samples from 17 individuals who were followed up prospectively to the time of disease onset. Proteomic signatures from this group of individuals (designated the progressor group) were compared to those in a group of individuals who were considered at risk of developing RA, stratified as either positive (n = 63) or negative (n = 47) for anti-citrullinated protein antibodies (ACPAs) (designated the at-risk group). Machine learning was used to identify a protein signature that could accurately classify those individuals at highest risk of future RA development.

RESULTS

A preclinical proteomic signature that differentiated RA progressors from at-risk individuals, irrespective of ACPA status, was identified (area under the curve 0.913, accuracy 91.2%). Importantly, the predictive preclinical proteomic signature was present not only in serum samples obtained close to the onset of RA, but also in serum samples obtained a median of 30.9 months prior to onset. Network analysis implicated the activation of Toll-like receptor 2 and production of tumor necrosis factor and interleukin-1 as key events that precede RA progression.

CONCLUSION

Alterations in the serum proteome in the preclinical phase of RA can emerge years prior to the onset of disease. Our findings suggest that the serum proteome provides a rich source of proteins serving both to classify at-risk individuals and to identify molecular pathways involved in the development of clinically detectable RA.

Association of Lipid Mediators With Development of Future Incident Inflammatory Arthritis in an Anti-Citrullinated Protein Antibody-Positive Population

OBJECTIVE

To determine the association of polyunsaturated fatty acid (PUFA)-derived lipid mediators with progression from rheumatoid arthritis (RA)-related autoimmunity to inflammatory arthritis (IA).

METHODS

We conducted a prospective cohort study using data from the Studies of the Etiology of Rheumatoid Arthritis (SERA). SERA enrolled first-degree relatives (FDRs) of individuals with RA (FDR cohort) and individuals who screened positive for RA-related autoantibodies at health fairs (screened cohort). We followed up 133 anti-cyclic citrullinated peptide 3.1 (anti-CCP3.1)-positive participants, 29 of whom developed IA. Lipid mediators selected a priori were quantified from stored plasma samples using liquid chromatography tandem mass spectrometry. We fit multivariable Cox proportional hazards models for each lipid mediator as a time-varying variable. For lipid mediators found to be significantly associated with IA, we then examined interleukin-1β (IL-1β), IL-6, IL-8, and tumor necrosis factor (TNF) as potential statistical mediators.

RESULTS

For every 1 natural log pg/ml increase in the circulating plasma levels of proinflammatory 5-HETE, the risk of developing IA increased by 241% (hazard ratio 2.41 [95% confidence interval 1.43-4.07]) after adjusting for age at baseline, cohort (FDR or screened), and shared epitope status. The models examining 15-HETE and 17-HDHA had the same trend but did not reach significance. We did not find evidence that the association between 5-HETE and IA risk was influenced by the proinflammatory cytokines tested.

CONCLUSION

In a prospective cohort of anti-CCP-positive individuals, higher levels of 5-HETE, an important precursor to proinflammatory leukotrienes, is associated with subsequent IA. Our findings highlight the potential significance of these PUFA metabolites in pre-RA populations.

Fluctuation in anti-cyclic citrullinated protein antibody level predicts relapse from remission in rheumatoid arthritis: KURAMA cohort

Background

The positivity of anti-citrullinated protein/peptide antibodies (ACPAs) is a clinically useful diagnostic and prognostic marker in rheumatoid arthritis (RA). However, the significance of ACPA titer and its fluctuation remain unclear. This study aimed to assess the role of ACPA titer and its fluctuation on disease activity and the prognosis of RA.

Methods

Data obtained from the Kyoto University Rheumatoid Arthritis Management Alliance (KURAMA) cohort was analyzed. Patients whose ACPA was measured at least twice between 2011 and 2019 and whose ACPA was positive at least once were included in this study. The association between the clinical variable and ACPA titer or its change was investigated.

Results

ACPA titer was measured in a total of 3286 patients, 1806 of whom were ACPA-positive at least once. Among them, the ACPA titer level was measured more than once in 1355 patients. Very weak correlation was observed between the ACPA titer level and disease activity. Additionally, there was no trend in the fluctuation of ACPA titer level in each patient; ACPA titer level fluctuated in some patients, but not in others. Patients with high variable levels of ACPA titer were more likely to relapse from remission. In the analysis of two consecutive ACPA measurements, the titer changes predicted the relapse from remission within a year of the second measurement.

Conclusions

The ACPA titer level fluctuated in some patients. Very weak correlation was observed between the ACPA titer level and disease activity. Fluctuation in ACPA titer level predicted relapse from remission in patients with RA.

Supplementary information

The online version contains supplementary material available at 10.1186/s13075-020-02366-x.