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

The immune response to citrullinated antigens is found almost exclusively in patients with rheumatoid arthritis (RA). It is a dynamic response that expands before the onset of disease and generates antibodies (anti-citrullinated protein antibodies (ACPAs)) that are extensively glycosylated in the variable domain. This feature of ACPAs is remarkable and warrants detailed investigation, as it can offer insights into the earliest immunologic mechanisms that lead up to the development of RA. The acquisition of variable domain glycans, in fact, could enable ACPA-expressing B cells to breach tolerance. Although the underlying mechanisms are still elusive, data to support this concept are emerging, owing to the reliable identification and isolation of citrullinated antigen-directed B cells from patients with RA. This technological proficiency also allows for the generation of an increasing number of well-defined monoclonal ACPAs, and provides the opportunity to test and define the mechanisms by which the citrullinated antigen-directed B cell response contributes to the onset and persistence of inflammation. Together with a revised perception of the HLA-risk effect and novel insights into how T cells can govern antibody effector functions, these developments shape an increasingly clear picture of the B cell response to citrullinated antigens in the development of RA.

Early treatment is associated with improved outcomes in patients with rheumatoid arthritis (RA), suggesting that a 'window of opportunity', in which the disease is most susceptible to disease-modifying treatment, exists. Autoantibodies and markers of systemic inflammation can be present long before clinical arthritis, and maturation of the immune response seems to coincide with the development of RA. The pre-arthritis phase associated with symptoms such as as joint pain without clinical arthritis (athralgia) is now hypothesized to fall within the aforementioned window of opportunity. Consequently, disease modulation in this phase might prevent the occurrence of clinically apparent arthritis, which would result in a persistent disease course if untreated. Several ongoing proof-of-concept trials are now testing this hypothesis. This Review highlights the importance of adequate risk prediction for the correct design, execution and interpretation of results of these prevention trials, as well as considerations when translating these findings into clinical practice. The patients' perspectives are discussed, and the accuracy with which RA development can be predicted in patients presenting with arthralgia is evaluated. Currently, the best starting position for preventive studies is proposed to be the inclusion of patients with an increased risk of RA, such as those identified as fulfilling the EULAR definition of 'arthralgia suspicious for progression to RA'.

Objective To investigate the association between weight or body mass index (BMI) and the development of hand osteoarthritis. Methods Systematic review of observational studies. Medical databases were searched up to April 2008. Articles that presented data on the association between weight and hand osteoarthritis were selected. The qualities of these studies were then assessed by two independent reviewers using a 19 criteria scoring system. Using the mean scores of all studies as a cut-off value, the studies were deemed as high or low quality. Study quality and study designs were combined to determine the level of evidence using best-evidence synthesis, which consisted of five levels of evidence. Results From the 25 studies included, two had cohort, three case–control and 20 cross-sectional study designs. Fifteen studies were considered high-quality studies. Of these high-quality studies, one cohort, two case–control and seven cross-sectional studies showed a positive association between weight or BMI and hand osteoarthritis. Based on three high-quality studies with preferred study designs (one cohort and two case–control) with a positive association, the level of evidence of the association between overweight and developing hand osteoarthritis is moderate. The approximate risk ratio of this association is 1.9. Conclusion Weight or BMI is associated with the development of hand osteoarthritis. The level of evidence of published studies is moderate according to best-evidence synthesis. Further high-quality cohort or case–control studies are needed to elucidate the role of weight in hand osteoarthritis.

The presence of autoantibodies is a defining feature of many autoimmune diseases. The number of unique autoantibody clones is conceivably limited by immune tolerance mechanisms, but unknown due to limitations of the currently applied technologies. Here, we introduce an autoantigen-specific liquid chromatography-mass spectrometry-based IgG1 Fab profiling approach using the anti-citrullinated protein antibody (ACPA) repertoire in rheumatoid arthritis (RA) as an example. We show that each patient harbors a unique and diverse ACPA IgG1 repertoire dominated by only a few antibody clones. In contrast to the total plasma IgG1 antibody repertoire, the ACPA IgG1 sub-repertoire is characterised by an expansion of antibodies that harbor one, two or even more Fab glycans, and different glycovariants of the same clone can be detected. Together, our data indicate that the autoantibody response in a prominent human autoimmune disease is complex, unique to each patient and dominated by a relatively low number of clones. Although many autoimmune diseases are characterized by the presence of autoantibodies, complete characterisation of autoantibody repertoires is lacking. Here, the authors introduce an autoantigen-specific Fab profiling method to show that the autoantibody repertoire in rheumatoid arthritis is diverse yet dominated only by a few clones.

Rheumatoid arthritis (RA) is a chronic autoimmune disease affecting 0.5–1% of the population worldwide. The disease has a heterogeneous character, including clinical subsets of anti-citrullinated protein antibody (ACPA)-positive and APCA-negative disease. Although the pathogenesis of RA is poorly understood, progress has been made in identifying genetic factors that contribute to the disease. The most important genetic risk factor for RA is found in the human leukocyte antigen (HLA) locus. In particular, the HLA molecules carrying the amino acid sequence QKRAA, QRRAA, or RRRAA at positions 70–74 of the DRβ1 chain are associated with the disease. The HLA molecules carrying these “shared epitope” sequences only predispose for ACPA-positive disease. More than two decades after the discovery of HLA-DRB1 as a genetic risk factor, the second genetic risk factor for RA was identified in 2003. The introduction of new techniques, such as methods to perform genome-wide association has led to the identification of more than 20 additional genetic risk factors within the last 4 years, with most of these factors being located near genes implicated in immunological pathways. These findings underscore the role of the immune system in RA pathogenesis and may provide valuable insight into the specific pathways that cause RA.

Although treatment with biologic disease-modifying antirheumatic drugs (bDMARDs) has significantly improved clinical outcomes in patients with rheumatoid arthritis (RA), many patients do not have access to these treatments. As cost-effective alternatives to their reference products (RPs), biosimilars provide an opportunity to increase access to bDMARDs. The European Medicines Agency and the US Food and Drug Administration have detailed pathways for the approval of biosimilars based on establishing the similarity of the biosimilar to the RP in terms of structure and function, pharmacokinetics (PK), efficacy, safety, and immunogenicity. A number of biosimilars of adalimumab, infliximab, etanercept, and rituximab RPs have been approved in the United States and/or European Union. This article is focused on the seven adalimumab biosimilars. A review of the data for the biosimilars FKB327, ABP 501, BI 695501, GP2017, MSB11022, PF-06410293, and SB5 confirm that these products are highly similar to the adalimumab RP with regard to structure, physicochemical and biological properties, PK, safety, immunogenicity, and efficacy in the treatment of RA and other chronic immune-mediated, inflammatory conditions. Data from several switching studies showed no changes in efficacy, safety, trough serum drug concentration, or immunogenicity between the biosimilars and their RP.Trial registration: ClinicalTrials.gov identifiers: NCT02260791, NCT02405780, NCT01970475, NCT02137226, NCT02045979, NCT02744755, NCT02144714, NCT02167139, NCT03014947, NCT02114931, NCT02640612, NCT02167139, NCT03052322, NCT02480153. EudraCT numbers: 2012-005140-23, 2012-000785-37, 2013-003722-84, 2015-000579-28, 2014-002879-29, 2014-000662-21, 2013-004654-13, 2015-002634-41, 2014-005229-11, 2016-002852-26, 2014-000352-29Plain Language SummaryBiologic disease-modifying antirheumatic drugs (bDMARDs) improve outcomes for patients with rheumatoid arthritis (RA); however, many patients do not have access to these treatments. Biosimilars offer a cost-effective alternative to their reference product (RP) and provide the opportunity to increase access to bDMARDs. This article reviews available data regarding the pharmacokinetics (PK), safety, immunogenicity, and effectiveness of the adalimumab RP and its biosimilars (FKB327, ABP 501, BI 695501, GP2017, MSB11022, PF-06410293, and SB5) in the treatment of RA. Based on the published literature, we concluded that these products are similar to the adalimumab RP in terms of their structure, physicochemical and biological properties, and PK. We also found that these biosimilars have similar safety and effectiveness to the adalimumab RP in the treatment of patients with RA. In addition, switching between a biosimilar and the adalimumab RP resulted in no impact on safety, effectiveness, serum concentrations, or immunogenicity.

Background Rheumatoid arthritis (RA) is characterized by the presence of autoantibodies like rheumatoid factor (RF), anti-cyclic citrullinated peptide-2 (anti-CCP2), and anti-carbamylated protein (anti-CarP) antibodies. It is currently unclear whether changes in autoantibody levels are associated with disease activity/treatment outcomes and whether they are modified by treatment intensity. Therefore, we determined longitudinal changes in RA-autoantibody levels, the association between these changes and activity score (DAS) and treatment outcomes, and the effect of intensity of immunosuppressive treatment on levels. Methods In 381 seropositive RA patients from the IMPROVED study, we measured IgG, IgM, and IgA of anti-CCP2 and anti-CarP; IgM and IgA of RF; and IgG against four citrullinated and two acetylated peptides at 4-month intervals over the first year of treatment. Following initial prednisone and methotrexate (MTX), treatment was changed every 4 months aiming for DAS < 1.6. We investigated changes in autoantibody levels following treatment escalation versus tapering, and the association of levels with DAS over time, EULAR response, and drug-free remission (DFR) ≥ 1 year. Results For all 14 autoantibodies, levels decreased from 0 to 4 months and then rose until 12 months. Following treatment escalation, autoantibody levels dropped markedly, while they rose following tapering: RF IgM levels, a representative autoantibody, dropped 10% after restarting prednisone and rose 15% aU/mL after tapering MTX ( p  < 0.0001). There was no association between autoantibody levels and DAS over time or EULAR response. Greater relative changes between 0 and 12 months did not predict DFR (0–12-month relative change RF IgM, − 39% for no DFR ( n  = 126) and − 16% for DFR ( n  = 18)). Conclusions Changes in RA-autoantibody levels are not associated with DAS or long-term treatment response, but reflect intensity of immunosuppression. This suggests that autoantibody levels are modifiable by current therapies, but that modifying levels is in itself of limited clinical relevance. Trial registration ISRCTN11916566 . Registered on 7 November 2006

Background Rheumatoid arthritis (RA) is an autoimmune disease characterized by the presence of autoantibodies against modified proteins, known as anti-modified protein autoantibodies (AMPAs). While the relationship between different AMPA isotypes and various risk factors remains poorly understood, investigating this association is important for a deeper understanding of RA pathophysiology. Smoking, has its primary effects in the lungs, and it remains unclear whether smoking is preferentially linked to specific AMPA isotypes, such as IgA, which could suggest a mucosal origin. Therefore, we set out to investigate the association between smoking, genetic risk factors for RA, and the presence of specific AMPA isotypes, particular IgA. Methods In 618 RA patients, anti-citrullinated protein antibodies (ACPA-) and anti-acetylated protein antibodies (AAPA-) IgA, -IgG and -IgM and RF-IgA and -IgM were measured by ELISA. Associations with genetic risk factors, smoking and autoantibodies were assessed with logistic regression analysis. For replication, a comprehensive meta-analysis incorporating 3309 RA patients was performed. Results Smoking was primarily associated with IgA AMPA, with associations that prevailed after correcting for the concurrent presence of AMPA IgG (ACPA-IgA OR 1.89 [1.14–3.12], AAPA-IgA 2.30 [1.35–3.94]). To further substantiate these results, we performed a meta-analysis of 3309 RA patients and observed that smoking was again predominantly associated with the combined presence of ACPA-IgA in addition to ACPA-IgG (OR 2.05 [1.69–2.49], p  < 0.001) versus the single presence of ACPA-IgG (OR 1.18 [0.97–1.44], p  = 0.11). A gene-environment interaction between the most important genetic risk factor for RA (the HLA shared epitope alleles) and smoking was only seen in patients that were both ACPA-IgG and ACPA-IgA positive, but not in patients who were only positive for ACPA-IgG. Conclusion These data provide a pivotal refinement of existing knowledge regarding risk factor associations for RA and lend novel support to the hypothesis that smoking may exert its effect on RA by the induction of local (auto)immune responses at mucosal sites.

Background Belimumab, an anti-B-cell activating factor antibody, is approved for the treatment of auto-antibody positive systemic lupus erythematosus with a high degree of disease activity. Anti-CD20 B cell depletion with rituximab is used in refractory SLE as well, although with variable responses. We hypothesized that incomplete B cell depletion, related to a surge in BAFF levels following rituximab treatment, can cause ongoing disease activity and flares. The Synbiose 1 study primarily focused on immunological effects and shows the preliminary clinical benefit of combined rituximab and belimumab in SLE. The Synbiose 2 study will evaluate the clinical efficacy of combining belimumab with rituximab in patients with severe SLE, allowing the tapering of prednisolone and mycophenolate. Methods Synbiose 2 is a phase 3, multicenter, randomized, controlled, open-label 2-year clinical trial. Seventy adults with severe SLE including lupus nephritis will be randomized 1:1 to receive either standard of care consisting of prednisolone and mycophenolate as induction and maintenance treatment, or belimumab and rituximab combined with standard of care as induction treatment, followed by prednisolone and belimumab as maintenance treatment. The primary objective is to assess whether combined B cell therapy will lead to a reduction of treatment failure. Secondary endpoints are complete and partial clinical and renal response and the improvement of SLE-specific autoimmune phenomena. Safety endpoints include the incidence of adverse events, with a special interest in infections. Discussion The Synbiose 2 trial is the first multicenter phase 3 clinical trial investigating combined B cell targeted therapy in SLE, including lupus nephritis. The outcome of this study will provide further evidence for the clinical efficacy of this new treatment strategy in severe SLE. Trial registration ClinicalTrials.gov NCT03747159 . Registered on 20 November 2018.