Closing the serological gap: promising novel biomarkers for the early diagnosis of rheumatoid arthritis

Utility of testing for third-generation anticyclic citrullinated peptide (anti-CCP3) antibodies in individuals who present with new musculoskeletal symptoms but have a negative second-generation anticyclic citrullinated peptide (anti-CCP2) antibody test

OBJECTIVES

To investigate the role of third-generation anticyclic citrullinated peptide (anti-CCP3) antibodies in predicting progression to inflammatory arthritis (IA) in individuals with new musculoskeletal (MSK) symptoms and a negative second-generation anti-CCP antibody test (anti-CCP2-).

METHODS

469 anti-CCP2- individuals underwent baseline anti-CCP3 testing (QUANTA Lite CCP3; Inova Diagnostics) and received a post enrolment 12-month questionnaire. A rheumatologist confirmed or excluded diagnosis of IA. Univariable/multivariable analyses were performed to assess the value of anti-CCP3 in predicting IA development in these anti-CCP2- individuals.

RESULTS

Only 16/469 (3.4%) anti-CCP2- individuals had a positive anti-CCP3 test. Of these 16 individuals, 4 developed IA. In addition, 61/469 (13.0%) anti-CCP2- individuals self-reported, to have developed, IA. Progression was confirmed in 43/61 of them (70.5%); of whom 30/43 (69.8%) and 13/43 (30.2%) were given a diagnosis of IA and rheumatoid arthritis (RA), respectively. In qualitative univariable analysis, anti-CCP3 positivity was associated with self-reported progression (p<0.01) and IA (p=0.03), but not with RA. Anti-CCP3 levels differed significantly between progressors and non-progressors (p<0.01) for all three categories. At the manufacturer's cut-off, OR for progression ranged from 2.4 (95% CI 0.5 to 18.6; RA) to 7.5 (95% CI 2.3 to 24.0; self-reported progression). Interestingly, when cut-offs for anti-CCP3 were optimised, lower values (≥5 units) significantly increased the OR for progression in all three categories. In multivariable analysis, anti-CCP3 positivity at the manufacturer's cut-off did not remain associated with IA progression, while this lower cut-off value (≥5 units) was associated with diagnosis of RA (p=0.02).

CONCLUSIONS

Anti-CCP3 testing could improve the prediction of IA development in anti-CCP2- individuals with new MSK symptoms.

Association of Mediterranean diet pattern with disease activity in the patients with rheumatoid arthritis: A cross-sectional study on Iranian patients

BACKGROUND & AIMS

Rheumatoid arthritis is a systemic autoimmune disease that causes joint erosion, as well as damage to extra-articular organs. The aim of this study was the investigation of the association between the Mediterranean diet quality index with disease activity in patients with rheumatoid arthritis.

METHODS

In this cross-sectional study 184 females with rheumatoid arthritis were studied in Kermanshah, Iran. The American College of Rheumatology's 2010 criteria were used to diagnose RA. The biochemical tests including erythrocyte sedimentation rate, C-reactive protein, rheumatoid facto, anti-nuclear antibody titration, antibodies against cyclic citrulline peptide, disease activity score 28 and the food frequency questionnaire was used to assess rheumatoid arthritis activity and the Mediterranean diet quality index, respectively. To compare the dietary intakes of participants across tertiles of Mediterranean diet score, we used Analysis of Variance. Multinomial logistic regression with three adjusted models was used to investigate the association between Mediterranean diet score with disease activity.

RESULTS

184 eligible patients with rheumatoid arthritis participated in this study. The mean age and duration of disease, body mass index, waist circumference and percent body fat did not differ significantly among the tertiles of the Mediterranean diet score (P-value>0.05). Participants in the highest tertile of Mediterranean diet score had significantly greater intakes of fruits, vegetables, fish, legume, nuts and had lowest intake of grains (refrain grain) and red and process meats to white meat ratio (P-value<0.05). There was no significant difference in terms of variables related to disease activity among the tertiles of the Mediterranean score (P-value>0.05). In multi-adjusted models, the odds ratio of Mediterranean diet scores no significant different in the third as compared to the first tertile of Mediterranean diet score (P-value>0.05).

CONCLUSION

Based on our findings there is no association between the Mediterranean diet score and disease activity of people with rheumatoid arthritis.

Performance of Anti-Carbamylated Protein Antibody Testing in the Routine Evaluation of Rheumatoid Arthritis from a Single Center

BACKGROUND

Detection of anticyclic citrullinated peptide antibodies (anti-CCP) and rheumatoid factors (RF) in sera support the diagnosis of rheumatoid arthritis (RA); however, these markers are not detected in about 20% of RA patients. More recently, antibodies against carbamylated proteins (anti-CarP) have emerged with implications for preclinical RA diagnosis. The objective of this study was to assess the clinical performance of anti-CarP and correlate with disease severity in routine clinical practice.

METHODS

Retrospective chart review of 331 subjects submitted for RA panel serology: 136 clinically defined RA-positive and 195 RA-negative patients. Fifty additional individuals were recruited for healthy controls. Patients' sera were tested for anti-CCP, anti-CarP, and RF antibodies. Clinical performance characteristics were evaluated for anti-CarP individually and in combination with anti-CCP and RF. Documented erosions and synovitis were correlated with anti-CarP positivity.

RESULTS

Anti-CarP had a clinical sensitivity and specificity of 27% and 94%, respectively, for established RA. This sensitivity was lower than anti-CCP (79%) and RF (85%). The specificity of anti-CarP was similar to anti-CCP (93%) and higher than RF (69%). Anti-CarP in combination with anti-CCP and RF increased specificity (100%) but decreased sensitivity (21%). There was no correlation of anti-CarP positivity with presence of bone erosions; however, there was an increase in anti-CarP positivity among patients with synovitis.

CONCLUSIONS

Anti-CarP demonstrates high specificity in diagnosis of established RA but lacks clinical sensitivity. In combination, anti-CarP does not improve clinical performance of anti-CCP and RF but may be useful in anti-CCP negative patients and in identifying patients with more active disease.

Should ACR/EULAR criteria be revised changing the RF and ACPA scores?

Current classification criteria for rheumatoid arthritis (RA) encompass clinical and immunological items and are capable of correctly identifying the majority of symptomatic RA patients. The presence of positive rheumatoid factor (RF) and/or and anti-cyclic citrullinated protein/peptide antibodies (ACPA) gaining increasing importance according to their serological titer eases the recognition of RA, yet the debate is open on whether this scoring system ought to be optimized by hierarchizing ACPA or the combination of ACPA and RF over single positivity, prioritizing specificity over sensitivity. The risk of misdiagnosis and misclassification are often entangled, yet they are not the same. In fact, while ideal diagnosis requires 100% sensitivity and specificity, classification criteria are conceived to gather a homogeneous patient population, favoring specificity over sensitivity. Nevertheless, as they are frequently summoned to support the diagnostic process in clinical practice, issues arise on how comprehensive those should be and on how frequently they should be updated in light of novel acquisitions regarding measurable RA-related abnormalities. In this viewpoint two different views on the topic are confronted, discussing the performance of available criteria and the potentiality and pitfalls of their refinement according to novel data on ACPA and RF contribution and emergence of newly discovered specificities.

Antibodies against advanced glycation end-products and malondialdehyde-acetaldehyde adducts identify a new specific subgroup of hitherto patients with seronegative arthritis with a distinct clinical phenotype and an HLA class II association

OBJECTIVE

In rheumatoid arthritis (RA) around two-thirds of patients are autoantibody positive for rheumatoid factor, anti-citrullinated protein antibodies and/or anti-carbamylated protein antibodies. The remaining seronegative subgroup of patients is clinically heterogeneous and thus far, biomarkers predicting the disease course are lacking. Therefore, we analysed the value of other autoantibodies in RA directed against malondialdehyde-acetaldehyde adducts (MAA) and advanced glycation end-products (AGE).

METHODS

In sera of 648 patients with RA and 538 patients without RA from the Leiden Early Arthritis Clinic, anti-MAA and anti-AGE IgG antibody levels were measured using ELISA. Associations between genetic risk factors, acute phase reactants, radiological joint damage, remission and anti-PTM positivity were investigated using regression, correlation and survival analyses.

RESULTS

Anti-AGE and anti-MAA were most prevalent in RA (44.6% and 46.1% respectively) but were also present in non-RA arthritis patients (32.9% and 30.3% respectively). Anti-AGE and anti-MAA antibodies were associated with HLA-DRB1*03 within seronegative RA (OR=1.98, p=0.003, and OR=2.37, p<0.001, respectively) and, for anti-AGE also in non-RA arthritis patients (OR=2.34, p<0.001). Presence of anti-MAA antibodies was associated significantly with markers of inflammation, erythrocyte sedimentation rate and C reactive protein, in all groups independent of anti-AGE. Interestingly, the presence of anti-AGE and anti-MAA antibodies was associated with radiological progression in patients with seronegative RA, but not evidently with sustained drug-free remission.

CONCLUSIONS

Anti-AGE and anti-MAA were present in around 45% of RA patients and 30% of non-RA arthritis patients, and although not specific for RA, their presence associated with HLA, inflammation and, for RA, with clinical outcomes especially in patients with seronegative RA.

When Autoantibodies Are Missing: The Challenge of Seronegative Rheumatoid Arthritis

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

Benefits of Autoantibody Enrichment in Early Rheumatoid Arthritis: Analysis of Efficacy Outcomes in Four Pooled Abatacept Trials

INTRODUCTION

The efficacy of abatacept is enhanced in anti-citrullinated protein antibody (ACPA) and rheumatoid factor (RF)-positive versus -negative patients with rheumatoid arthritis (RA). Four early RA abatacept trials were analyzed to understand the differential impact of abatacept among patients with SeroPositive Early and Active RA (SPEAR) compared to non-SPEAR patients.

METHODS

Pooled patient-level data from AGREE, AMPLE, AVERT, and AVERT-2 were analyzed. Patients were classified as SPEAR if they were ACPA +, RF +, disease duration < 1 year, and Disease Activity Score-28 (DAS28) C-reactive protein (CRP) ≥ 3.2 at baseline; non-SPEAR otherwise. Outcomes included: American College of Rheumatology (ACR) 20/50/70 at week 24; mean change from baseline to week 24 for DAS28 (CRP), Simple Disease Activity Index (SDAI), ACR core components; DAS28 (CRP) and SDAI remission. Adjusted regression analyses among abatacept-treated patients compared SPEAR and non-SPEAR patients, and in full trial population estimating how the efficacy of abatacept versus comparators [adalimumab + methotrexate, methotrexate] was modified by SPEAR status.

RESULTS

The study included 1400 SPEAR and 673 non-SPEAR patients; most were female (79.35%), white (77.38%), and with a mean age 49.26 (SD 12.86) years old. Around half with non-SPEAR were RF + and three-quarters ACPA +. Stronger improvements from baseline to week 24 were observed in almost all outcomes for abatacept-treated SPEAR versus non-SPEAR patients or versus SPEAR patients treated with comparators. Larger improvements were observed for SPEAR patients among the abatacept-treated population, and more strongly improved efficacy among SPEAR patients for abatacept than comparators.

CONCLUSIONS

This analysis, including large patient numbers of early-RA abatacept trials, confirmed beneficial treatment effects of abatacept in patients with SPEAR versus non-SPEAR.

Antibodies against multiple post-translationally modified proteins aid in diagnosis of autoimmune hepatitis and associate with complete biochemical response to treatment

Background

(Auto)immune mediated and cholestatic liver disease (AILD) includes autoimmune hepatitis (AIH), primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Especially AIH is characterized by the presence of autoantibodies and elevated serum immunoglobulins. In rheumatoid arthritis, autoantibodies against post-translational modifications (PTMs) such as citrullination (Cit) and carbamylation (CarP) are used as diagnostic and prognostic markers, respectively. We studied the presence of six anti-PTM antibodies in patients with the three AILDs and non-AILD.

Methods

Antibodies against six PTMs (malondialdehyde-acetaldehyde adducts (MAA), advanced glycation end-products (AGE), CarP, acetylation (AL), Cit, and nitration (NT)) were tested in sera of patients with AILD (n = 106), non-AILD (n = 101) and compared with healthy controls (HC) (n = 100). Levels and positivity were correlated with clinical and biochemical features in a well-defined cohort of untreated AIH patients.

Results

Anti-PTM antibodies were more often detectable in sera from AILD patients compared with HCs (anti-MAA: 67.9% vs. 2.0%, anti-AGE: 36.8% vs. 4.0%, anti-CarP: 47.2% vs. 5.0% and anti-AL: 18.9% vs. 5.0%). In untreated AIH, time to complete biochemical response (CBR) was associated with anti-MAA, anti-AGE, anti-CarP and anti-AL antibodies. Significantly more patients with at least three anti-PTM antibodies attained CBR at 12  months of treatment (13 vs. 3 p = 0.01).

Conclusion

Anti-PTM antibodies are frequently present in AILD. The presence of anti-MAA, anti-AGE and anti-CarP antibodies correlates with the presence of AIH within this cohort. In AIH, harboring at least three anti-PTM antibody responses is positively associated with CBR. Determination of anti-PTM antibodies in liver disease may have diagnostic and prognostic value.

Protein posttranslational modifications in health and diseases: Functions, regulatory mechanisms, and therapeutic implications

Protein posttranslational modifications (PTMs) refer to the breaking or generation of covalent bonds on the backbones or amino acid side chains of proteins and expand the diversity of proteins, which provides the basis for the emergence of organismal complexity. To date, more than 650 types of protein modifications, such as the most well-known phosphorylation, ubiquitination, glycosylation, methylation, SUMOylation, short-chain and long-chain acylation modifications, redox modifications, and irreversible modifications, have been described, and the inventory is still increasing. By changing the protein conformation, localization, activity, stability, charges, and interactions with other biomolecules, PTMs ultimately alter the phenotypes and biological processes of cells. The homeostasis of protein modifications is important to human health. Abnormal PTMs may cause changes in protein properties and loss of protein functions, which are closely related to the occurrence and development of various diseases. In this review, we systematically introduce the characteristics, regulatory mechanisms, and functions of various PTMs in health and diseases. In addition, the therapeutic prospects in various diseases by targeting PTMs and associated regulatory enzymes are also summarized. This work will deepen the understanding of protein modifications in health and diseases and promote the discovery of diagnostic and prognostic markers and drug targets for diseases.

Nanomedical approaches in the realm of rheumatoid arthritis

Rheumatoid arthritis (RA) is a heterogeneous autoimmune inflammatory disorder defined by the damage to the bone and cartilage in the synovium, which causes joint impairment and an increase in the mortality rate. It is associated with an incompletely elucidated pathophysiological mechanism. Even though disease-modifying antirheumatic drugs have contributed to recent improvements in the standard of care for RA, only a small fraction of patients is able to attain and maintain clinical remission without the necessity for ongoing immunosuppressive drugs. The evolution of tolerance over time as well as patients' inability to respond to currently available therapy can alter the overall management of RA. A significant increase in the research of RA nano therapies due to the possible improvements they may provide over traditional systemic treatments has been observed. New approaches to getting beyond the drawbacks of existing treatments are presented by advancements in the research of nanotherapeutic techniques, particularly drug delivery nano systems. Via passive or active targeting of systemic delivery, therapeutic drugs can be precisely transported to and concentrated in the affected sites. As a result, nanoscale drug delivery systems improve the solubility and bioavailability of certain drugs and reduce dose escalation. In the present paper, we provide a thorough overview of the possible biomedical applications of various nanostructures in the diagnostic and therapeutic management of RA, derived from the shortcomings of conventional therapies. Moreover, the paper suggests the need for improvement on the basis of research directions and properly designed clinical studies.

Anti-Carbamylated Protein Antibodies, Tumour Necrosis Factor Alpha and Insulin Resistance in Egyptian Patients With Rheumatoid Arthritis and Systemic Lupus Erythematosus

BACKGROUND

Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are autoimmune diseases. Premature atherosclerosis and cardiovascular diseases are two of the most important complications of these diseases. Anti-carbamylated protein antibody (Anti-carP Ab) is one of the antibodies which was studied in RA and SLE. In our study, we studied the relation between anti-carP Ab, disease activity and insulin resistance in RA and SLE patients.

METHODS

90Patients with SLE and RA were enrolled and subjected to history taking, clinical examination and assessment of disease activity using SLE disease activity index 2000 (SLEDAI-2K) scoring for SLE patients and disease activity score 28 (DAS28-ESR) for RA patients. Samples were examined for complete blood count (CBC), creatinine, inflammatory markers, Tumour necrosis factor alpha (TNF alpha), fasting insulin, fasting blood sugar (FBS), lipid profile and anti-carPAb. HOMA-IR (homeostasis model assessment for insulin resistance) was calculated.

RESULTS

Patients with RA and SLE showed higher levels of anti-carPAb in comparison with healthy subjects (8.25ng/ml for RA, 7ng/ml for SLE and 0.6ng/ml for healthy subjects with p value <0.001). There was a positive correlation between anti-carPAb and disease activity of RA (p value <0.001) and a positive correlation between anti-carPAb and TNF alpha in RA. In SLE, there was no correlation of anti-carP Ab with disease activity while, HOMA-IR showed a positive correlation with nephritis (p value 0.04).

CONCLUSION

Anti-carP antibody is a marker of disease activity in RA patients and has high specificity for both RA and SLE detection.

Anti-Protein-Arginine Deiminase 4 IgG and IgA Delineate Severe Rheumatoid Arthritis

There is a strong need for biomarkers of rheumatoid arthritis (RA) in all phases of the patient’s journey and to enable the implementation of precision medicine strategies to improve patient care. The objective of this study was to evaluate the presence of anti-protein-arginine deiminase (PAD) 4 IgG and IgA in the sera of RA patients and disease controls, and to investigate their association with joint erosion and biological treatment use. Sera from 104 RA and 155 controls were tested for the presence of anti-PAD4 IgG and IgA using a new particle-based multi-analyte technology (PMAT). Information on the erosive disease and biological treatment use was available for 54 of the RA patients, who were also tested for anti-citrullinated protein antibodies (ACPA). An association between the autoantibodies and these clinical features was investigated. Anti-PAD4 showed sensitivity and specificity values of 25.0% and 94.2% for IgG and of 21.2% and 94.8% for IgA for RA, respectively. The levels of these antibodies were also significantly higher in RA patients vs. controls, in erosive RA vs. non-erosive disease, and in patients under biologics vs. patients that were not on this treatment regimen. The anti-PAD4 IgG and IgA levels were correlated (rho = 0.60, p < 0.0001), but individuals that were positive for only one of the two isotypes were also observed. Anti-PAD4 IgG and IgA are associated with severe RA, and they represent valuable biomarkers for prognosis prediction and patient stratification.

Anti-Carbamylated Protein (Anti-CarP) Antibodies in Patients Evaluated for Suspected Rheumatoid Arthritis

(1) Background: Anti-carbamylated protein (CarP) antibodies have been studied as novel markers to aid in the diagnosis and prognosis of rheumatoid arthritis. (2) Methods: A total of 265 samples were included in the evaluation, for which 98 had results for anti-cyclic citrullinated peptide (CCP), 86 for rheumatoid factor (RF), and 212 for 14-3-3 eta protein. Anti-CarP antibodies were measured using a fetal calf serum-based single-step assay (research use only, Inova Diagnostics, San Diego, CA). (3) Results: Anti-CarP antibodies were significantly higher and more frequent in anti-CCP3.1+ (p = 0.0025), RF+ (p = 0.0043) and 14-3-3 eta+ (p = 0.028) samples compared to the negative counterpart group. In addition, isolated anti-CarP positivity occurred in samples negative for anti-CCP3.1, RF, or 14-3-3 eta. When anti-CarP antibodies were compared to each of the RF, anti-CCP3.1, and 14-3-3 eta by receiver operating characteristic (ROC) analyses, the area under the curve (AUC) values of 0.71 (RF), 0.68 (anti-CCP3.1), and 0.59 (14-3-3 eta), respectively, demonstrated a moderate correlation. Using an UpSet plot, we determined that 10.6% of the samples with available results for anti-CCP3.1, RF, and anti-CarP showed triple positivity. (4) Conclusions: Anti-carbamylated protein (anti-CarP) antibodies can be detected in anti-CCP, RF and 14-3-3 eta-positive and -negative patients, potentially identifying specific subsets of patients.

Impact of autoimmune serology test results on RA classification and diagnosis

Rheumatoid arthritis (RA) is the most common systemic autoimmune disease and also the most severe arthritic disorder. The measurement of rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA) in serum supports the diagnosis of RA, which gained increasing significance over the last 65 years. However, a high variability between RF and ACPA methods has been described, impacting the diagnostic performance of the current ACR/EULAR RA classification criteria.

The great number of commercially available assays, often lacking traceability to an international standard, is a major factor attributing to this in-between assay variability. The adoption of an international standard for ACPA, as is since long available for rheumatoid factor, is therefore highly desirable.

Further harmonization in clinical interpretation of RF/ACPA assays could be obtained by harmonization of the cut-offs, for both the low and high antibody levels, based on predefined specificity in disease controls. Reporting test result specific likelihood ratios (LR) adds value in the interpretation of autoantibody tests. However, a good understanding of the control population used to define antibody test result interval-associated LRs is crucial in defining the diagnostic performance characteristics of antibody serology.

Finally, specificity in RA classification can be improved by refining serological weight scoring taking into account the nature of the antibody, the antibody level and double RF + ACPA positivity.

Presence of anti-acetylated peptide antibodies (AAPA) in inflammatory arthritis and other rheumatic diseases suggests discriminative diagnostic capacity towards early rheumatoid arthritis

Aims:

To determine the diagnostic value of anti-acetylated peptide antibodies (AAPA) in patients with rheumatoid arthritis (RA).

Methods:

Three acetylated peptides (ac-lysine, ac-lysine.inv and ac-ornithine) derived from vimentin were employed to measure AAPA by enzyme-linked immunosorbent assay (ELISA) in sera of 120 patients with early RA (eRA), 195 patients with established RA (est RA), 99 healthy controls (HC), and 216 patients with other inflammatory rheumatic diseases. A carbamylated and a citrullinated version of the vimentin peptide were used additionally. Receiver operating characteristics and logistic regression analyses were used to assess the discriminative capacity of AAPA.

Results:

AAPA were detected in 60% of eRA and 68.7% of estRA patients, 22.2% of HC, and 7.1– 30.6% of patients with other rheumatic diseases. Importantly, AAPA were also present in 40% of seronegative RA patients, while antibodies to the carbamylated peptide were detected less frequently. Diagnostic sensitivity of individual peptides for eRA was 28.3%, 35.8%, and 34% for ac-lysine, ac-ornithine, and ac-lysine.inv, respectively. Positive likelihood ratios (LR+) for eRA versus HC were 14.0, 7.1, and 2.1. While the presence of a single AAPA showed varying specificity (range: 84–98%), the presence of two AAPA increased specificity considerably since 26.7% of eRA, as compared with 6% of disease controls, were double positive. Thus, double positivity discriminated eRA from axial spondyloarthritis with a LR+ of 18.3. Remarkably, triple positivity was 100% specific for RA, being observed in 10% of eRA and 21.5% of estRA patients, even in the absence of RF and ACPA.

Conclusion:

AAPA are highly prevalent in early RA and occur also independently of RF and ACPA, thereby reducing the gap of seronegativity. Furthermore, multiple AAPA reactivity increased the specificity for RA, suggesting high diagnostic value of AAPA testing.

The citrullinated/native index of autoantibodies against hnRNP-DL predicts an individual "window of treatment success" in RA patients

BACKGROUND

There is a need for biomarker to identify patients "at risk" for rheumatoid arthritis (risk-RA) and to better predict the therapeutic response and in this study we tested the hypothesis that novel native and citrullinated heterogeneous nuclear ribonucleoprotein (hnRNP)-DL autoantibodies could be possible biomarkers.

METHODS

Using protein macroarray and ELISA, epitope recognition against hnRNP-DL was analysed in sera from different developed RA disease and diagnosed SLE patients. Toll-like receptor (TLR) 7/9 and myeloid differentiation primary response gene 88 (MyD88)-dependency were studied in sera from murine disease models. HnRNP-DL expression in cultivated cells and synovial tissue was analysed by indirect immunofluorescence, immunoblot and immunohistochemistry.

RESULTS

HnRNP-DL was highly expressed in stress granules, citrullinated in the rheumatoid joint and targeted by autoantibodies either as native or citrullinated proteins in patient subsets with different developed RA disease. Structural citrullination dependent epitopes (SCEs) of hnRNP-DL were detected in 58% of the SLE patients although 98% of these sera were α-CCP-2-negative. To obtain a specific citrullinated signal value, we subtracted the native antibody value from the citrullinated signal. The citrullinated/native index of autoantibodies against hnRNP-DL (CNDL-Index) was identified as a new value for an "individual window of treatment success" in early RA and for the detection of RF IgM/α-CCP-2 seronegative RA patients (24-46%). Negative CNDL-index was found in SLE patients, risk-RA and early RA cohorts such as EIRA where the majority of these patients are DAS28-responders to methotrexate (MTX) treatment (87%). High positive CNDL-values were associated with more severe RA, shared epitope and parenchymal changes in the lung. Specifically, native α-hnRNP-DL is TLR7/9-dependent, associated with pain and ROC analysis revealed an association to initial MTX or etanercept treatment response, especially in seronegative RA patients.

CONCLUSION

CNDL-index defines people at risk to develop RA and the "window of treatment success" thereby closing the sensitivity gap in RA.

Anti-Carbamylated Protein Antibodies, Tumour Necrosis Factor Alpha and Insulin Resistance in Egyptian Patients With Rheumatoid Arthritis and Systemic Lupus Erythematosus

BACKGROUND

Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are autoimmune diseases. Premature atherosclerosis and cardiovascular diseases are two of the most important complications of these diseases. Anti-carbamylated protein antibody (Anti-carP Ab) is one of the antibodies which was studied in RA and SLE. In our study, we studied the relation between anti-carP Ab, disease activity and insulin resistance in RA and SLE patients.

METHODS

90Patients with SLE and RA were enrolled and subjected to history taking, clinical examination and assessment of disease activity using SLE disease activity index 2000 (SLEDAI-2K) scoring for SLE patients and disease activity score 28 (DAS28-ESR) for RA patients. Samples were examined for complete blood count (CBC), creatinine, inflammatory markers, Tumour necrosis factor alpha (TNF alpha), fasting insulin, fasting blood sugar (FBS), lipid profile and anti-carPAb. HOMA-IR (homeostasis model assessment for insulin resistance) was calculated.

RESULTS

Patients with RA and SLE showed higher levels of anti-carPAb in comparison with healthy subjects (8.25ng/ml for RA, 7ng/ml for SLE and 0.6ng/ml for healthy subjects with p value <0.001). There was a positive correlation between anti-carPAb and disease activity of RA (p value <0.001) and a positive correlation between anti-carPAb and TNF alpha in RA. In SLE, there was no correlation of anti-carP Ab with disease activity while, HOMA-IR showed a positive correlation with nephritis (p value 0.04).

CONCLUSION

Anti-carP antibody is a marker of disease activity in RA patients and has high specificity for both RA and SLE detection.

Anti-carbamylated protein antibodies in premenopausal rheumatoid arthritis women: relation to disease activity and bone loss

OBJECTIVES

Anti-carbamylated protein antibodies (anti-CarP Abs) are present in patients with RA, however, their association with bone loss is not confirmed. The purpose of this study was to determine the relation between the serum level of anti-CarP Abs in premenopausal RA women and disease activity and bone loss.

METHODS

This case-control study was conducted on 48 premenopausal women with RA and 48 matched healthy premenopausal women. All RA women were subjected to clinical examination, disease activity assessment using the 28-joint DAS (DAS28) and Clinical Disease Activity Index (CDAI), functional assessment using the HAQ, physical activity assessment using the International Physical Activity Questionnaire (IPAQ), fatigue assessment using the Modified Fatigue Impact Scale (MFIS), serological tests as well as anti-CarP Abs using ELISA. Moreover, the BMD was measured by DXA and plain X-ray of both hands was done to assess juxta-articular osteopenia and erosions.

RESULTS

The anti-CarP Abs level was significantly higher in RA patients than in healthy controls. The serum level of anti-CarP Abs had a significant positive correlation with the RA DAS28, CDAI, HAQ, MFIS and original Sharp score, while a significant negative correlation was present with the IPAQ. Anti-CarP Abs were negatively correlated with either spine BMD or Z-score and positively correlated with the original Sharp score.

CONCLUSION

Anti-CarP Abs were higher in premenopausal RA women compared with older and BMI matched healthy women. Anti-CarP Abs are associated with higher RA disease activity, increased disability and fatigability and decreased physical activity. Moreover, anti-CarP Abs are associated with systemic trabecular bone loss as well as local bone loss.

Systematic review and meta-analysis of the risk of rheumatoid arthritis-associated interstitial lung disease related to anti-cyclic citrullinated peptide (CCP) antibody

OBJECTIVE

To clarify the risk of rheumatoid arthritis-associated interstitial lung disease (RA-ILD) related to anti-cyclic citrullinated peptide (CCP) antibody.

ELIGIBILITY CRITERIA

Patients with RA with and without ILD were eligible. The primary outcome was the prevalence or incidence of ILD. Primary studies of any design aside from a case report were eligible.

INFORMATION SOURCES

Medline, EMBASE, Science Citation Index Expanded and Cochrane Central Register of Controlled Trials were searched from the inception through 12 November 2019.

DATA EXTRACTION AND RISK OF BIAS

Two reviewers independently selected eligible reports, extracted relevant data and assessed risk of bias using a modified Quality in Prognostic Studies tool.

DATA SYNTHESIS

Meta-analysis was conducted using a random-effects model.

QUALITY OF EVIDENCE

The Grades of Recommendation, Assessment, Development and Evaluation system was applied.

RESULTS

Among 29 out of 827 records retrieved through electronic databases and four additional reports identified from other sources, 29 studies were focused for the review. A total of 10158 subjects were included and the mean age at inclusion was between 45.8 and 63.9 years. The mean RA duration was between 4.3 and 14.9 years. The positivity of anti-CCP antibody ranged from 50.7% to 95.8%. All studies except for two were deemed as high risk of bias. A pooled analysis of univariate results demonstrated that the presence of anti-CCP antibody was significantly associated with RA-ILD with an OR of 2.10 (95% CI: 1.59 to 2.78). Similarly, the titre of anti-CCP antibody was significantly higher for RA-ILD with a standardised mean difference of 0.42 (95% CI: 0.20 to 0.65). These results were confirmed by multivariate analysis in the majority of studies and consistent by any subgroup and sensitivity analyses.

CONCLUSION

The presence and higher titres of anti-CCP antibody were suggested to be significantly associated with an increased risk of RA-ILD. However, the quality of evidence was rated as low or very low.

Do anti-carbamylated protein antibodies in rheumatoid arthritis reflect local and systemic osteoporosis? A study of osteoprotegrin and receptor activator for nuclear factor kappa B ligand and radiological assessment

Background

One of the most important and dangerous complications of rheumatoid arthritis (RA) is bone loss, which manifested by erosions and juxta-articular or systemic bone loss. Anti-carbamylated protein (anti-CarP) antibodies which are also called anti-homocitrulline antibodies have recently been found in RA. Increase anti-CarP antibody titres may lead to severe disease and increase the progression of bone loss. Osteoprotegrin and receptor activator for nuclear factor kappa B and its ligand (RANKL) are the main players in the pathogenesis of osteoporosis. Thus, we aimed to investigate and detect the presence and prevalence of anti-CarP in rheumatoid arthritis and their association with disease severity and osteoporosis, as well as with OPG/RANKL in 80 Egyptian RA patients to highlight this relationship which could be useful in managing RA patients with osteoporosis.

Results

Serum anti-CarP levels were significantly increased in the RA group compared with the control group (P< 0.001). We found a negative association between anti-CarP and anti-CCP and disease activity (r=−0.878, −0.534, respectively, P<0.001). We also found a positive correlation between anti-CarP and the Larsen score, DEXA score, RF, HAQ, and RANKL (r=0.646, 0.287, 0.243, 0.892, 0.671, 0.869 [respectively], P<0.001) and there was negative correlation between anti-CarP and OPG (r=−0.553, P<0.001).

Conclusion

Anti-CarP antibodies are associated with disease severity and disability in RA patients. They could play an important and significant role in the pathogenesis of osteoporosis in these patients.

The value of anti-CarP and anti-PAD4 as markers of rheumatoid arthritis in ACPA/RF negative rheumatoid arthritis patients

Background:

Anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF) are key factors in the American College of Rheumatology/European League Against Rheumatism rheumatoid arthritis (RA) classification criteria markers. However, about 30% of patients diagnosed with RA are seronegative, rationalizing the need for new serologic markers for RA. Antibodies against carbamylated proteins (anti-CarP) and against peptidyl-arginine deiminase type 4 (anti-PAD4) have been postulated to be useful RA markers. The purpose of this study is to evaluate the value of anti-CarP and anti-PAD4 in a well-characterized population of RA patients and healthy controls (HCs).

Methods:

A total of 122 RA patients and 30 HCs were enrolled in the study. Serum levels of ACPA, anti-PAD4, anti-CarP and RF were determined by enzyme-linked immunosorbent immunoassays (ELISAs). Synthetic carbamylated peptides were used in the ELISA assay to determine the protein targets of the anti-CarP antibodies.

Results:

Rates of ACPA, RF, anti-PAD4 and anti-CarP positivity were 85.2%, 67.2%, 55.7% and 46.7% in RA, and 0%, 0%, 6.7% and 6.7% in HC respectively. In the RA population, 25.4% of patients had all four types of antibodies positive, while 6.6% had no antibodies. There was a significant correlation between anti-PAD4 and ACPAs (r_s = 0.39), RF and ACPAs, (r_s = 0.3) and RF and anti-CarP, (r_s = 0.3). There was no correlation between ACPAs and anti-CarP. Anti-CarP positivity was noted in 49 (47.1%) and 45 (54.9%) of ACPAs and RF positive patients respectively. In addition, five anti-CarP+ patients did not have ACPA nor RF.

Conclusion:

Anti-CarP but not anti-PAD4 may be a useful biomarker in identifying ACPA/RF negative RA patients. This antibody may identify an additional RA population who may benefit from early implementation of aggressive therapy.

Cognitive Decline in Rheumatoid Arthritis: Insight into the Molecular Pathogenetic Mechanisms

Cognitive decline refers to a deterioration of intellectual and learning abilities and related memory problems, and is often associated with behavioral alterations, which prevents sufferers from carrying out the most common daily activities, such as maintaining normal productive interpersonal relationships, communicating, and leading an autonomous life. Numerous studies have highlighted the association between cognitive decline and autoimmune disorders, including rheumatoid arthritis (RA). RA is a chronic, inflammatory, autoimmune disease that involves systems and organs other than the bones and joints, with varying severity among patients. Here, we review the studies investigating the link between cognitive decline and RA, focusing on the main molecular pathogenetic mechanisms involved. The emerging body of data suggests that clinical, psychological, and biological factors may contribute to the pathogenesis of cognitive decline in RA, including cardiovascular complications, chronic pain, depression, inflammatory factors, changes in hormone levels, drug side effects, and genetics. Further studies are warranted in order to fully clarify the basis underlying the association between cognitive decline and RA and to find new possible diagnostic strategies and therapeutic targets for RA patients.

Serum biomarkers for Modic changes in patients with chronic low back pain

PURPOSE

Lumbar Modic change (MC) can serve as a diagnostic marker as well as an independent source of chronic low back pain (CLBP). This study aimed to test for the existence of serum biomarkers in CLBP patients with MC.

METHODS

Age- and sex-matched CLBP patients with confirmed MC on lumbar MRI (n = 40) and pain-free controls (n = 40) were assessed. MC was classified into M1, predominating M1, predominating M2 and M2. MC volumes were calculated. Fasting blood samples were assessed for inflammatory mediators, signalling molecules, growth factors and bone turnover markers. Serum concentrations of 46 biomarkers were measured.

RESULTS

Median concentrations of interleukin (IL)-15 (p < 0.001), IL-8 (p < 0.001), tumour necrosis factor (TNF)-alpha (p < 0.001), Eotaxin-1 (p < 0.05), Eotaxin-3 (p < 0.001), monocyte chemotactic protein (MCP)-1 (p < 0.05), macrophage inflammatory protein (MIP)-1alpha (p < 0.01), TEK receptor tyrosine kinase (Tie)-2 (p < 0.001), vascular cell adhesion molecule (VCAM)-1 (p < 0.001), RANTES (p < 0.001), C telopeptide of type I collagen (CTX)-1 (p < 0.001), vascular endothelial growth factor (VEGF)-C (p < 0.001), VEGF-D (p < 0.05), fms-related tyrosine kinase (Flt)-1 (p < 0.01) and intercellular adhesion molecule (ICAM)-1 (p < 0.01) were significantly higher among controls. IL-1sRII (23.2 vs. 15.5 ng/ml, p < 0.001) and hepatocyte growth factor (HGF)-1 (169 vs. 105 pg/ml, p < 0.01) concentrations were significantly higher among patients. Type or volume of MC was not associated with biomarker concentrations.

CONCLUSIONS

This is the first study to assess the blood serum biomarker profile in individuals with CLBP with MC. Several biomarkers were suppressed, while two markers (IL-1sRII and HGF) were elevated among MC patients, irrespective of MC type or size, with CLBP compared with asymptomatic controls.

The significance of serum 14-3-3η level in rheumatoid arthritis patients

BACKGROUND

RA is a systemic inflammatory condition characterized by chronic arthritis and often associated with irreversible joint damage.

OBJECTIVES

To assess the significance of serum level of 14-3-3η in RA and its association with clinical and serological features of the disease.

METHODS

This is a case-control study done on 80 participants. They were divided into 2 groups. Group 1: 40 rheumatoid arthritis patients compared to group 2: 40 healthy participants matched for age and sex. Laboratory investigations including complete blood count (CBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) rheumatoid factor (RF), anti-citrullinated peptide antibodies (ACPAs), and serum 14-3-3η were done to all participants. Radiological examination in the form of plain X-ray for hands and feet was done to all patients.

RESULTS

Serum levels of 14-3-3η were significantly higher in RA patients compared to the control group (p < 0.001). Serum 14-3-3η was the only predictor of high Larsen's score (p = 0.013) on using linear regression analysis. Serum 14-3-3η can predict RA in healthy controls in univariate (p = 0.001) and multivariate (p = 0.004) analyses. The receiver operating characteristic (ROC) curve of 14-3-3η was constructed for discrimination between RA and control subjects. The best cut-off value was 61.9 ng/mL, with fair AUC (0.773, p < 0.001), 95% CI (0.656-0.889), and the sensitivity and specificity of 14-3-3η for RA diagnosis as 65% and 95% respectively. Also, we constructed ROC curves for RF, ACPA, 14-3-3η, and their combinations; we found that the highest test sensitivity of 95.7% appeared on adding the 3 markers together, and the highest test specificity of 100% was detected on adding RF to ACPA, 14-3-3η to ACPA or the 3 molecules together.

CONCLUSION

14-3-3η could be a valuable marker for the diagnosis of RA patients and it may have prognostic value. Key Points • 14-3-3η is a valuable marker for the diagnosis of RA patients. • 14-3-3η reflects disease severity and joint damage in RA patients.

Improved classification of rheumatoid arthritis with a score including anti-acetylated ornithine antibodies

The presence of rheumatoid factor (RF) or anti-cyclic citrullinated peptide (anti-CCP) autoantibodies contributes to the current rheumatoid arthritis (RA) classification criteria. These criteria involve stratification on antibody levels, which limits reproducibility, and underperform in the RA patients without RF and anti-CCP. Here, we have explored if two anti-acetylated peptide antibodies (AAPA), anti-acetylated lysine (AcLys) and anti-acetylated ornithine (AcOrn), could improve the performance of the current criteria. The analysis was done in 1062 prospectively-followed early arthritis (EA) patients. The anti-AcOrn were more informative than the anti-AcLys, the conventional RA antibodies and the anti-carbamylated protein antibodies. The anti-AcOrn produced a classification that did not require antibody levels and showed improved specificity (77.6% vs. 72.6%, p = 0.003) and accuracy (79.0% vs. 75.8%, p = 0.002) over the current criteria. These improvements were obtained with a scoring system that values concordance between anti-AcOrn, RF and anti-CCP. No significant gain was obtained in sensitivity (80.2% vs. 78.8%, p = 0.25) or in improving the classification of the RA patients lacking RF and anti-CCP, although the anti-AcOrn ranked first among the analysed new antibodies. Therefore, the anti-AcOrn antibodies could contribute to the improvement of RA classification criteria by exploiting antibody concordance.

Citrullination as a novel posttranslational modification of matrix metalloproteinases

Matrix metalloproteinases (MMPs) are enzymes with critical roles in biology and pathology. Glycosylation, nitrosylation and proteolysis are known posttranslational modifications (PTMs) regulating intrinsically the activities of MMPs. We discovered MMP citrullination by peptidyl arginine deiminases (PADs) as a new PTM. Upon hypercitrullination, MMP-9 acquired a higher affinity for gelatin than control MMP-9. Furthermore, hypercitrullinated proMMP-9 was more efficiently activated by MMP-3 compared to control MMP-9. JNJ0966, a specific therapeutic inhibitor of MMP-9 activation, inhibited the activation of hypercitrullinated proMMP-9 by MMP-3 significantly less in comparison with control proMMP-9. The presence of citrullinated/homocitrullinated MMP-9 was detected in vivo in neutrophil-rich sputum samples of cystic fibrosis patients. In addition to citrullination of MMP-9, we report efficient citrullination of MMP-1 and lower citrullination levels of MMP-3 and MMP-13 by PAD2 in vitro. In conclusion, citrullination of MMPs is a new PTM worthy of additional biochemical and biological studies.

Omega-3 fatty acid intake suppresses induction of diverse autoantibody repertoire by crystalline silica in lupus-prone mice

Inhalation of crystalline silica (cSiO2) in the workplace is etiologically linked to lupus and other autoimmune diseases. Exposing lupus-prone NZBWF1 mice to respirable cSiO2 unleashes a vicious cycle of inflammation and cell death in the lung that triggers interferon-regulated gene expression, ectopic lymphoid structure (ELS) development, elevation of local and systemic autoantibodies (AAbs), and glomerulonephritis. However, cSiO2-induced inflammation and onset of autoimmunity can be prevented by inclusion of the ω-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) into the diet of these mice. Since cSiO2 both causes cell death and interferes with efferocytosis, secondary necrosis of residual cell corpses might provide a rich and varied autoantigen (AAg) source in the lung. While it is known that the particle induces anti-nuclear and anti-dsDNA AAbs in NZBWF1 mice, the full extent of the cSiO2-induced AAb response relative to specificity and isotype is not yet understood. The purpose of this study was to test the hypotheses that cSiO2 exposure induces a wide spectrum of AAbs in the pulmonary and systemic compartments, and that dietary DHA intervention prevents these changes. Archived tissue fluid samples were obtained from a prior study in which NZBWF1 mice were fed purified isocaloric diets containing no DHA (control) or DHA corresponding calorically to human doses of 2 and 5 g/day. Mice were intranasally instilled with 1 mg cSiO2 or saline vehicle weekly for 4 weeks, then groups euthanized 1, 5, 9, or 13 weeks post-instillation (PI) of the last cSiO2 dose. Bronchoalveolar lavage fluid (BALF) and plasma from each time point were subjected to AAb profiling using a microarray containing 122 AAgs. cSiO2 triggered robust IgG and IgM AAb responses against lupus-associated AAgs, including DNA, histones, ribonucleoprotein, Smith antigen, Ro/SSA, La/SSB, and complement as early as 1 week PI in BALF and 5 weeks PI in plasma, peaking at 9 and 13 weeks PI, respectively. Importantly, cSiO2 also induced AAbs to AAgs associated with rheumatoid arthritis (collagen II, fibrinogen IV, fibrinogen S, fibronectin, and vimentin), Sjögren's syndrome (α-fodrin), systemic sclerosis (topoisomerase I), vasculitis (MPO and PR3), myositis (Mi-2, TIF1-γ, MDA5), autoimmune hepatitis (LC-1), and celiac disease (TTG). cSiO2 elicited comparable but more modest IgA AAb responses in BALF and plasma. cSiO2-induced AAb production was strongly associated with time dependent inflammatory/autoimmune gene expression, ELS development, and glomerulonephritis. AAb responses were dose-dependently suppressed by DHA supplementation and negatively correlated with the ω-3 index, an erythrocyte biomarker of ω-3 content in tissue phospholipids. Taken together, these findings suggest that cSiO2 exposure elicits a diverse multi-isotype repertoire of AAbs, many of which have been reported in individuals with lupus and other autoimmune diseases. Furthermore, induction of this broad AAb spectrum could be impeded by increasing ω-3 tissue content via dietary DHA supplementation.

T cell immunoglobulin and mucin domain-3 is associated with disease activity and progressive joint damage in rheumatoid arthritis patients

T cell immunoglobulin and mucin domain-3 (TIM-3) is a surface molecule expressed on immune cells which play a role in immune regulation. The aims of the present study were to determine whether circulating soluble T cell immunoglobulin domain and mucin-3 (sTIM-3) are elevated in rheumatoid arthritis (RA) patients, and investigate the relationships between sTIM-3 and clinical features of RA.The study included 116 patients with established RA and 27 healthy control subjects. Serum levels of sTIM-3 were measured via the enzyme-linked immunosorbent assays (ELISA). Correlations between serum sTIM-3 and a range of parameters including anti-citrullinated peptide antibody (ACPA) titer, erythrocyte sedimentation rate (ESR), and matrix metalloproteinase-3 (MMP-3) were assessed.Serum sTIM-3 was significantly elevated in RA patients compared with those in healthy subjects, and it was positively correlated with ACPA titer (r = 0.27 P = .005), ESR (r = 0.27, P = .004) and MMP-3 (r = 0.35, P < .001). In RA patients with high ACPA titers (≥200 U/mL), sTIM-3 was not correlated with ESR or MMP-3. Whereas, sTIM-3 was significantly correlated with ESR and MMP-3 in RA patients with low ACPA titers (<200 U/mL).Serum sTIM-3 was increased in RA patients, and it was associated with proinflammatory markers and disease activity in RA patients under a particular ACPA status. Our data suggest that circulating sTIM-3 may be a useful biomarker for the determination of disease activity in RA patients.

Tocilizumab-Conjugated Polymer Nanoparticles for NIR-II Photoacoustic-Imaging-Guided Therapy of Rheumatoid Arthritis

The progressive debilitating nature of rheumatoid arthritis (RA) combined with its unknown etiology and initial similarity to other inflammatory diseases makes early diagnosis a significant challenge. Early recognition and treatment of RA is essential for achieving effective therapeutic outcome. NIR-II photoacoustic (PA) molecular imaging (PMI) is emerging as a promising new strategy for effective diagnosis and treatment guidance of RA, owing to its high sensitivity and specificity at large penetration depth. Herein, an antirheumatic targeted drug tocilizumab (TCZ) is conjugated to polymer nanoparticles (PNPs) to develop the first NIR-II theranostic nanoplatform, named TCZ-PNPs, for PA-imaging-guided therapy of RA. The TCZ-PNPs are demonstrated to have strong NIR-II extinction coefficient, high photostability and excellent biocompatibility. NIR-II PMI results reveal the excellent targeting abilities of TCZ-PNPs for the effective noninvasive diagnosis of RA joint tissue with a high signal-to noise ratio (SNR) of 35.8 dB in 3D PA tomography images. Remarkably, one-month treatment and PA monitoring using TCZ-PNPs shows RA is significantly suppressed. In addition, the therapeutic evaluation of RA mice by NIR-II PMI is shown to be consistent with clinical micro-CT and histological analysis. The TCZ-PNPs-assisted NIR-II PMI provides a new strategy for RA theranostics, therapeutic monitoring and the beyond.

A discovery of screening markers for rheumatoid arthritis by liquid chromatography mass spectrometry: A metabolomic approach

AIM

This study aimed to discover serum metabolite biomarkers for potential use in screening for rheumatoid arthritis (RA).

METHODS

The sera from 43 healthy controls (HCs) and 49 RA patients were globally analyzed using high-performance liquid chromatography- tandem mass spectrometry. Molecular features (MFs) from samples were analyzed using volcano plots, partial least squares discriminant analysis, and variable importance in projection scores to select candidates. The spectra of candidate MFs were matched with the METLIN database. We confirmed the association between candidates and RA and analyzed the receiver-operating characteristic (ROC) curves.

RESULTS

We selected a total of 57 candidate MFs that had a fold change ≥1.5, P value ≤.05, and over 80% of frequency. Among them, 18 MFs were identified as metabolites with the METLIN database. Six metabolites (dehydroepiandrosterone sulfate, androsterone sulfate, γ-linolenic acid, 9[E],11[E]-conjugated linoleic acid, docosahexaenoic acid, and docosapentaenoic acid [22n-3]) out of the 18 were associated with mechanisms of RA and were selected as final candidates. ROC curve analysis revealed their area under the curve (AUC) values were all above 0.75 and the combined AUC of the six candidates was 0.89.

CONCLUSION

Using six candidates as a marker set showed potential in distinguishing RA patients from HCs, based on high AUC values. Therefore, we propose that a marker set of these six candidates has potential clinical application in RA screening.

Elevated levels of anti-carbamylated protein antibody in patients with rheumatoid arthritis: association with disease activity and bone destruction

To measure the serum levels of anticarbamylated protein (CarP) antibodies in patients with rheumatoid arthritis (RA) in China and to evaluate the association of anti-CarP antibodies with clinical parameters and disease activity. 260 Chinese patients with RA, 40 patients with osteoarthritis (OA), 88 patients with spondyloarthritis (SpA) and 77 healthy controls were included. The serum levels of anti-CarP antibodies were detected by ELISA. Blood tests to detect the anticyclic citrullinated peptide (CCP) antibody level, rheumatoid factor (RF) level, erythrocyte sedimentation rate, C reactive protein level and Disease Activity Score in 28 joints using the erythrocyte sedimentation rate (DAS28-ESR) were performed by standard methods. Bone erosion was assessed by colour Doppler ultrasonography. A total of 18.8% of patients with RA and 9.4% of anti-CCP antibody and RF-double-negative patients were positive for anti-CarP antibody. The anti-CarP antibody level was significantly higher in patients with RA than in patients with OA or SpA and in healthy controls. Univariate and multivariate analyses showed that the level of anti-CarP antibody was positively correlated with DAS28-ESR; the higher a level of serum anti-CarP antibody, the higher the DAS28-ESR score. Anti-CarP-positive patients had higher disease activity scores than anti-CarP-negative patients. Moreover, anti-CarP-positive patients had a higher risk of developing bone erosion. The anti-CarP antibody was found to play an important role in the diagnosis of RA, especially in anti-CCP antibody and RF-double-negative patients. The anti-CarP antibody is a potential marker of disease activity and bone erosion in RA.

Profiling of IgG antibodies targeting unmodified and corresponding citrullinated autoantigens in a multicenter national cohort of early arthritis in Germany

OBJECTIVE

To assess the diagnostic potential of IgG antibodies to citrullinated and corresponding native autoantigens in early arthritis.

METHODS

IgG autoantibodies to 390 distinct unmodified and corresponding in vitro citrullinated recombinant proteins were measured by a multiplex assay in baseline blood samples from a German multicenter national cohort of 411 early arthritis patients (56.5 ± 14.6 years, 62.8% female). The cohort was randomly split into a training cohort (n = 329, 28.6% ACPA positive) and a validation cohort (n = 82, 32.9% ACPA pos.). The diagnostic properties of candidate antibodies to predict a subsequent diagnosis of rheumatoid arthritis (RA) as opposed to a non-RA diagnosis were assessed by receiver operating characteristics analysis and generalized linear modeling (GLM) with Bonferroni correction in comparison to clinically determined IgM rheumatoid factor (RF) and citrullinated peptide antibody (ACPA) status.

RESULTS

Of 411 patients, 309 (75.2%) were classified as RA. Detection rates of antibody responses to citrullinated and uncitrullinated forms of the proteins were weakly correlated (Spearman's r = 0.13 (95% CI 0.029-0.22), p = 0.01). The concentration of 34 autoantibodies (32 to citrullinated and 2 to uncitrullinated antigens) was increased at least 2-fold in RA patients and further assessed. In the training cohort, a significant association of citrullinated "transformer 2 beta homolog" (cTRA2B)-IgG with RA was observed (OR 5.3 × 103, 95% CI 0.8 × 103-3.0 × 106, p = 0.047). Sensitivity and specificity of cTRA2B-IgG (51.0%/82.9%) were comparable to RF (30.8%/91.6%) or ACPA (32.1%/94.7%). Similar results were obtained in the validation cohort. The addition of cTRA2B-IgG to ACPA improved the diagnostic performance over ACPA alone (p = 0.026 by likelihood ratio test).

CONCLUSIONS

cTRA2B-IgG has the potential to improve RA diagnosis in conjunction with RF and ACPA in early arthritis.

Metabolomics in the development and progression of rheumatoid arthritis: A systematic review

OBJECTIVE

A systematic review and analysis of data from several rheumatoid arthritis metabolomics studies attempts to determine which metabolites can be used as potential biomarkers for the diagnosis of rheumatoid arthritis and to explore the pathogenesis of rheumatoid arthritis.

METHODS

We searched all the subject-related documents published by EMBASE, PubMed, Web of Science, and Cochrane Library from the database to the September 2019 publication. Two researchers independently screened the literature and extracted the data. QUADOMICS tool was used to assess the quality of studies included in this systematic review.

RESULTS

A total of 10 studies met the inclusion criteria of systematic review, including 502 patients with rheumatoid arthritis and 373 healthy people. Among them, the biological samples utilised for metabolomic analysis include: serum (n=8), urine (n=1) and synovial fluid (n=1). Some metabolites play an important role in rheumatoid arthritis: glucose, lactic acid, citric acid, leucine, methionine, isoleucine, valine, phenylalanine, threonine, serine, proline, glutamate, histidine, alanine, cholesterol, glycerol, and ribose.

CONCLUSIONS

Metabolomics provides important new opportunities for further research in rheumatoid arthritis and is expected to elucidate the pathogenesis of rheumatoid arthritis that has not been fully understood before.

Sensitivity and specificity of Interleukin 29 in patients with rheumatoid arthritis and other rheumatic diseases

BACKGROUND

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic and progressive inflammation that can cause a high degree of disability in affected individuals. Proinflammatory cytokines play central roles in the development of degradative and inflammatory responses in RA. IL-29 has been identified in RA and reported as a biomarker of the disease.

OBJECTIVE

To analyze serum levels and accuracy of IL-29 in RA patients compared to healthy subjects and patients with other rheumatic diseases.

METHODS

IL-29 serum levels were measured in 121 patients with RA, 53 patients with systemic lupus erythematosus (SLE), 60 patients with systemic sclerosis (SSc), 29 patients with fibromyalgia (FM), 50 patients with osteoarthritis (OA) and 68 healthy individuals as controls. IL-29 levels in serum were investigated by ELISA. Sensitivity, specificity and likelihood ratios (LR) for having RA were calculated.

RESULTS

Serum levels of IL-29 were increased in RA patients 113.6 (IQR = 31.25-308.5) pg/ml compared to non-RA patients (SLE, SSc, OA, and FM) (31.25 pg/ml) and healthy controls (31.25 pg/ml, p < 0.001). The IL-29 cut-off values to distinguish patients with RA from non-RA patients were 61.11 pg/ml (sensitivity 57.02, specificity 92.71, LR: 7.82) and for all subjects 32.96 pg/ml (sensitivity 64.46, specificity 87.31, LR: 5.08). Additionally, IL-29 correlated negatively with age (r=-0189, p = 0.038) and disease duration (-0.192, p = 0.037). Interestingly, IL-29 correlated positively with neutrophil count in RA patients positive for rheumatoid factor (r = 0.259, p = 0.022).

CONCLUSION

IL-29 is higher in the serum of patients with RA compared to non-RA subjects and may have potential for use as a biological marker.

Precision medicine in the care of rheumatoid arthritis: Focus on prediction and prevention of future clinically-apparent disease

There is an emerging understanding that an individual's risk for future rheumatoid arthritis (RA) can be determined using a combination of factors while they are still in a state where clinically-apparent inflammatory arthritis (IA) is not yet present. Indeed, this concept has underpinned several completed and ongoing prevention trials in RA. Importantly, risk factors can be divided into modifiable (e.g. smoking, exercise, dental care and diet) and non-modifiable factors (e.g. genetics, sex, age). In addition, there are now several biomarkers including autoantibodies, inflammatory markers and imaging techniques that are highly predictive of future clinically-apparent IA/RA. Although none of the prevention studies have yet provided major breakthroughs, several of them have provided valuable insights that can help to improve the design of future clinical trials and enable RA prevention. In aggregate, these findings suggest that the most accurate disease prediction models will require the combination of demographic and clinical information, biomarkers and potentially medical imaging data to identify individuals for intervention. This review summarizes some of the key aspects around precision medicine in RA with special focus on disease prediction and prevention.

Immune checkpoint inhibitor-induced inflammatory arthritis as a model of autoimmune arthritis

The development of inflammatory arthritis in patients receiving immune checkpoint inhibitor therapy is increasingly recognized due to the growing use of these drugs for the treatment of cancer. This represents an important opportunity not only to define the mechanisms responsible for the development of this immune-related adverse event and to ultimately predict or prevent its development, but also to provide a unique window into early events in the development of inflammatory arthritis. Knowledge gained through the study of this patient population, for which the inciting event is known, could shed light into the pathogenesis of autoimmune arthritis. This review will highlight the clinical and immunologic features of these entities to define common elements for future study.

Comparison of methods to construct a genetic risk score for prediction of rheumatoid arthritis in the population-based Nord-Trøndelag Health Study, Norway

Objectives

To evaluate selection methods among published single-nucleotide polymorphisms (SNPs) associated with RA to construct predictive genetic risk scores (GRSs) in a population-based setting.

Methods

The Nord-Trøndelag Health (HUNT) Study is a prospective cohort study among the whole adult population of northern Trøndelag, Norway. Participants in HUNT2 (1995–1997) and HUNT3 (2006–2008) were included (489 RA cases, 61 584 controls). The initial SNP selection from relevant genome-wide studies included 269 SNPs from 30 studies. Following different selection criteria, SNPs were weighted by published odds ratios. The sum of each person’s carriage of all weighted susceptibility variants was calculated for each GRS.

Results

The best-fitting risk score included 27 SNPs [weighted genetic risk score 27 (wGRS27)] and was identified using P-value selection criterion ≤5 × 10−8, the largest possible SNP selection without high linkage disequilibrium (r2 &lt; 0.8), and lasso regression to select for positive coefficients. In a logistic regression model adjusted for gender, age and ever smoking, wGRS27 was associated with RA [odds ratio 1.86 (95% CI 1.71, 2.04) for each s.d. increase, P &lt; 0.001]. The AUC was 0.76 (95% CI 0.74, 0.78). The positive and negative predictive values were 1.6% and 99.7%, respectively, and the positive predictive value was not improved in sensitivity analyses subselecting participants to illustrate settings with increased RA prevalences. Other schemes selected more SNPs but resulted in GRSs with lower predictive ability.

Conclusion

Constructing a wGRS based on a smaller selection of informative SNPs improved predictive ability. Even with a relatively high AUC, the low PPV illustrates that there was a large overlap in risk variants among RA patients and controls, precluding clinical usefulness.

An overview of autoantibodies in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic auto-immune disease principally effecting synovial joints. RA is characterized by immune cell infiltration in the joint. The presence of autoantibodies is a hallmark for the disease, among these are rheumatoid factor and antibodies against post-translational modified proteins like citrullination (ACPA) and carbamylation (anti-CarP antibodies). These autoantibodies may form immune complexes in the joint, leading to the attraction of immune cells. Based on the presence of these autoantibodies, RA patients can be subdivided in autoantibody positive and negative disease. Both subsets can be associated with genetic and environmental risk factors for RA, like the human leukocyte antigen (HLA) allele and smoking. Autoantibodies can already be detected years before disease onset in a subgroup of patients and at symptom onset a broad isotype spectrum is observed. This suggests that various events occur prior to the development of RA in which the first autoantibodies develop in predisposed individuals. Therefore, the presence of these autoantibodies can be useful in predicting future RA patients. Research on the characteristics and effector function of these autoantibodies is ongoing and will give more knowledge in the inflammatory responses underlying RA. This will give insight in the pathogenic role of autoantibodies in RA. Recent data are suggestive of a role for mucosal surfaces in the development of auto-immune responses associated with (the development of) RA. In conclusion, investigating the potential pathogenic effector functions of autoantibody isotypes and their molecular- and physicochemical-compositions might improve understanding of the disease origin and its underlying immunological processes. This may lead to the development of new therapeutic targets and strategies.

Improved RA classification among early arthritis patients with the concordant presence of three RA autoantibodies: analysis in two early arthritis clinics

Background

The patients with RA benefit from early identification soon after the first clinical symptoms appear. The 2010 ACR/EULAR classification criteria were developed to fulfill this need and their application has been demonstrated to be effective. However, there is still room for improvement. Therefore, we aimed to evaluate the potential of the concordant presence of RF, anti-CCP and anti-carbamylated protein antibodies to improve current RA classification among early arthritis (EA) patients.

Methods

Data from the first visit of 1057 patients in two EA prospective cohorts were used. The serological scores from the 2010 ACR/EULAR criteria and the concordant presence of the three RA autoantibodies were assessed relative to a gold standard consisting of the RA classification with the 1987 ACR criteria at the 2 years of follow-up.

Results

The concordant presence of three antibodies showed predictive characteristics allowing for direct classification as RA (positive predictive value = 96.1% and OR = 80.9). They were significantly better than the corresponding to the high antibody titers defined as in the 2010 classification criteria (PPV = 88.8%, OR = 26.1). In addition, the concordant presence of two antibodies was also very informative (PPV = 82.3%, OR = 15.1). These results allowed devising a scoring system based only on antibody concordance that displayed similar overall performance as the serological scoring system of the 2010 criteria. However, the best classification was obtained combining the concordance and 2010 serological systems, a combination with a significant contribution from each of the two systems.

Discussion

The concordant presence of RA autoantibodies showed an independent contribution to the classification of EA patients that permitted increased discrimination and precision.

Differing X-ray patterns in seronegative and seropositive rheumatoid arthritis

INTRODUCTION

Anti-citrullinated protein antibody (ACPA) and rheumatoid factor (RF) status are important predictors for rheumatoid arthritis (RA) erosivity. Qualitative differences on hand/feet radiographs have been described, indicating more carpal fusion in seronegative RA. This study explores these differences further using the total Sharp/van der Heijde score (TSS), digital X-ray radiogrammetry (DXR), and qualitative description.

METHODS AND MATERIALS

Matched seronegative (ACPA negative, RF negative, snRA) and seropositive (ACPA, RF > 3xULN, spRA) were examined. TSS scores both for erosions and joint space narrowing (JSN) were registered separately and compared for both groups. Joint compartments and single joints were compared, using a heat map. The degree of carpal fusion was quantified 0-5. DXR measurements (bone mineral density, cortical thickness, bone width, metacarpal index) were determined for each hand separately. Finally, selected radiographs were examined unblinded to search for non-quantifiable differences.

RESULTS

A total of 56 snRA and 57 spRA patients were examined. spRA patients had more erosions and joint space narrowing. Erosion load differed significantly between spRA and snRA in the foot and metacarpophalangeal joint, but not in the wrist or proximal interphalangeal joint compartments. Intracompartmental differences were greater in spRA. JSN scores were greater in spRA, in all compartments except wrist. Carpal fusion and DXR scores did not differ between the groups. The qualitative comparison showed that snRA patients displayed periarticular ossifications, carpal shortening, and sparing of the CMC joints, whereas spRA patients had more CMC damage and less shortening.

CONCLUSION

X-ray manifestations in snRA and spRA are qualitatively and quantitatively different. This suggests pathophysiological differences between the two forms. Key Points • Seronegative and seropositive RA display qualitatively and quantitatively different X-ray patterns, suggesting differences in the underlying pathophysiological process. This is the first time that this has been shown in a systematic, quantitative fashion.

ACPA-negative RA consists of subgroups: patients with high likelihood of achieving sustained DMARD-free remission can be identified by serological markers at disease presentation

Background

Disease-modifying antirheumatic drug (DMARD)-free remission, the sustained absence of synovitis after DMARD cessation, is increasingly achievable, especially in autoantibody-negative rheumatoid arthritis (RA). However, underlying mechanisms are unknown and patient subgroups that achieve this outcome are insufficiently characterized. We evaluated whether serological biomarkers at disease onset, as measured within the multi-biomarker disease activity (MBDA) score, are differently expressed in RA patients who achieve sustained DMARD-free remission.

Methods

Two hundred ninety-nine RA patients were evaluated for achievement of sustained DMARD-free remission during a median follow-up of 4.3 years. Twelve biomarkers, as included in the MBDA score, were determined from the serum obtained at disease onset. Patients were categorized as having a low (< 30), moderate (30–44) or high (> 44) score. Analyses were stratified for anti-citrullinated protein antibodies (ACPA) based under the assumption that ACPA-positive and ACPA-negative RA are different disease entities.

Results

Twenty percent achieved sustained DMARD-free remission. Overall, high MBDA scores were associated with achieving DMARD-free remission (high vs. low HR 3.8, 95% CI 1.2–12.2). Among ACPA-negative RA patients, moderate or high scores associated strongly with DMARD-free remission (moderate vs. low HR 9.4, 95% CI 1.2–72.9; high vs. low HR 9.7, 95% CI 1.3–71.1). This association was independent of age and other clinical factors (high vs. low HR 8.2, 95% CI 1.1–61.8). For ACPA-negative RA patients, the biomarkers C-reactive protein, serum amyloid A and matrix metalloproteinase-3 were individually associated with sustained DMARD-free remission. Among ACPA-positive RA patients, scores were not associated with DMARD-free remission.

Conclusions

ACPA-negative RA patients who achieved sustained DMARD-free remission after treatment withdrawal were characterized by moderate to high MBDA scores at diagnosis. This is the first evidence that ACPA-negative RA can be subdivided in clinically relevant subsets at disease onset using a protein profile.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1902-2) contains supplementary material, which is available to authorized users.

Anticyclic Citrullinated Peptide Antibodies 3.1 and Anti-CCP-IgA Are Associated with Increasing Age in Individuals Without Rheumatoid Arthritis

OBJECTIVE

We investigated the association of age and anticyclic citrullinated peptide antibodies (anti-CCP) in subjects without rheumatoid arthritis (RA).

METHODS

Serum was tested for anti-CCP3.1 (IgG/IgA) in 678 first-degree relatives (FDR) of patients with RA and 330 patients with osteoarthritis (OA). Individual isotypes (anti-CCP-IgA and anti-CCP-IgG) were also tested in all FDR.

RESULTS

In FDR, increasing age was significantly associated with positivity for anti-CCP3.1 (per year, OR 1.03) and anti-CCP-IgA (per year, OR 1.05) but not anti-CCP-IgG. In FDR and OA subjects, anti-CCP3.1 prevalence was significantly increased after age 50 years.

CONCLUSION

Increasing age in individuals without RA should be considered in the interpretation of anti-CCP3.1 positivity.

Comparative study of the diagnostic and prognostic value of antibodies against chimeric citrullinated synthetic peptides and CCP3/CCP3.1 assays

BACKGROUND

The objective of the study was to compare the diagnostic yield of home-made ELISA tests based on synthetic chimeric fibrin/filaggrin citrullinated peptides (CFFCPs) with CCP3 and CCP3.1 commercial tests to detect anti-citrullinated protein/peptide antibodies (ACPAs) in rheumatoid arthritis (RA) patients. The prognostic value is also studied in a cohort of patients with early RA. Moreover, we transfer immunological assays from microtiter plates to microarray formats to allow the simultaneous analysis of several peptide sequences and reduce the volume of serum from patients.

METHODS

The diagnostic study includes: 100 RA patients who fulfilled the 1987 ACR criteria; 100 healthy blood donors; 35 patients with SLE according ACR criteria; 35 patients with PsA fulfilling the Wright and Moll criteria and 30 patients with HCV infection. The prognostic value study includes 50 patients with early RA with follow-up data available. All samples are from outpatients attending the Rheumatology Department of the Hospital Clinic of Barcelona.

RESULTS

Similar sensitivity, specificity and predictive values for the diagnosis of RA of CCFCPs compared to CCP3/CCP3.1 were obtained. Although a high concordance is observed between anti-CFFCPs and anti-CCP3/CCP3.1 in the early patients that rendered Larsen radiographic progression, CFFCPs could be a better marker of radiographic outcome. Strong correlations between the microarray and ELISA results were found for individual CFFCPs peptides.

CONCLUSIONS

The development of multiplexing techniques combining a different spectrum of markers in a single analysis, including CFFCP peptides, could allow a more detailed analysis of the autoantibodies reactivity found in the sera of patients suffering of this heterogeneous disease.

Triple Positivity for Anti-Citrullinated Protein Autoantibodies, Rheumatoid Factor, and Anti-Carbamylated Protein Antibodies Conferring High Specificity for Rheumatoid Arthritis: Implications for Very Early Identification of At-Risk Individuals

OBJECTIVE

In rheumatoid arthritis (RA), anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF) are commonly used to aid in the diagnosis. Although these autoantibodies are mainly found in RA, their specificity is not optimal. It is therefore difficult to identify RA patients, especially in very early disease, based on the presence of ACPAs and RF alone. In addition, anti-carbamylated protein (anti-CarP) antibodies have diagnostic and prognostic value, since their presence is associated with joint damage in RA patients and also associated with the future development of RA in patients with arthralgia. Therefore, the aim of the present study was to investigate the value of combined antibody testing in relation to prediction and diagnosis of (early) RA.

METHODS

A literature search resulted in identification of 12 relevant studies, consisting of RA patients, pre-RA individuals, disease controls, healthy first-degree relatives of RA patients, and healthy control subjects, in which data on RF, ACPAs, and anti-CarP antibody status were available. Using these data, random effects meta-analyses were carried out for several antibody combinations.

RESULTS

The individual antibodies were highly prevalent in patients with RA (34-80%) compared to the control groups, but were also present in non-RA controls (0-23%). For the classification of most subjects correctly as having RA or as a non-RA control, the combination of ACPAs and/or RF often performed well (specificity 65-100%, sensitivity 59-88%). However, triple positivity for ACPAs, RF, and anti-CarP antibodies resulted in a higher specificity for RA (98-100%), accompanied by a lower sensitivity (11-39%).

CONCLUSION

As the rheumatology field is moving toward very early identification of RA and possible screening for individuals at maximum risk of RA in populations with a low pretest probability, an autoantibody profile of triple positivity for ACPAs, RF, and anti-CarP provides interesting information that might help identify individuals at risk of developing RA.

The anti-carbamylated protein antibody response is of overall low avidity despite extensive isotype switching

Objective

To better understand the contribution of autoantibodies in RA and the biology of their responses, we evaluated the avidity of the anti-carbamylated protein (anti-CarP) antibody response.

Methods

The avidity of anti-CarP antibody, ACPA and anti-tetanus toxoid IgG were determined using elution assays. Anti-CarP IgG avidity was measured in sera of 107 RA patients, 15 paired SF and serum samples and 8 serially sampled sera before and after disease onset.

Results

The avidity of anti-CarP IgG is low compared with the avidity of anti-tetanus toxoid IgG present in the same sera. Likewise, although less pronounced, anti-CarP also displayed a lower avidity as compared with the avidity of ACPA IgG. No difference in anti-CarP IgG avidity is observed between ACPA positive or ACPA negative patients. Anti-CarP IgG avidity is higher in anti-CarP IgM-negative compared with IgM-positive individuals. Furthermore, the anti-CarP avidity in serum is higher than in SF. Using samples of individuals that over time developed RA we observed no anti-CarP avidity maturation in the years before disease onset. In contrast to ACPA avidity, the anti-CarP avidity is not associated with severity of joint destruction.

Conclusion

The anti-CarP response is of overall low avidity, even lower than the ACPA IgG avidity, and does not show apparent avidity maturation before or around disease onset. Overall, isotype switch and avidity maturation seem to be uncoupled as isotype switch occurs without avidity maturation, pointing towards a commonality in the regulation of both autoantibody responses as opposed to the pathways governing recall responses.