Rob J. Van De Stadt

Development of the anti–citrullinated protein antibody repertoire prior to the onset of rheumatoid arthritis

OBJECTIVE To examine how anti-citrullinated protein antibody (ACPA) epitope spreading takes place prior to the onset of clinical rheumatoid arthritis (RA), and to analyze the pattern of autoantigen reactivity at the beginning of the immune response. METHODS Multiple consecutive serum samples from 79 RA patients who had donated blood before disease onset were available for analysis. Fifty-three patients tested positive for ACPAs prior to the onset of clinical RA. For these patients, a median of 6 (interquartile range 4-9) sequential pre-RA serum samples obtained 1-2 years apart were tested. Reactivity to 5 distinct citrullinated peptides was measured by enzyme-linked immunosorbent assay. Two peptides were derived from fibrinogen, 1 from vimentin, 1 from α-enolase, and 1 from filaggrin. RESULTS In 25 of 53 ACPA-positive patients, seroconversion from ACPA absence to ACPA presence was observed. In 72% of these patients, the immune response started with reactivity to 1 peptide, without preference for a particular peptide. The number of peptides recognized increased over time, without a dominant epitope-spreading pattern. ACPAs appeared in low levels several years prior to the diagnosis of RA. Antibody titers increased markedly ∼2-4 years before diagnosis. CONCLUSION Our findings indicate that ACPA epitope spreading occurs over several years prior to the onset of clinical RA. The initial autoimmune response is mostly directed toward only 1 autoantigen, but this is not always the same antigen. The marked increase in ACPA titers a few years prior to the diagnosis of RA suggests a second stage in disease development, which might be due to a variety of factors.

The extent of the anti-citrullinated protein antibody repertoire is associated with arthritis development in patients with seropositive arthralgia

Objectives To determine the fine specificity of anti-citrullinated protein antibodies (ACPA) in the early phase of arthritis development, the ACPA repertoire in arthralgia patients and the association with arthritis development were studied. Methods A total of 244 patients with arthralgia positive for anti-cyclic citrullinated peptide antibodies (aCCPs) and/or IgM rheumatoid factor (IgM-RF), without arthritis were included. Development of arthritis was defined as presence of one or more swollen joints at clinical examination during follow-up. Sera were tested at baseline for reactivity to five citrullinated peptides derived from fibrinogen (three), vimentin (one) and α-enolase (one) and five corresponding arginine peptides in an ELISA. Results In all, 69 patients (28%) developed arthritis in a median of 3 joints after a median follow-up of 11 (IQR 5–20) months. Reactivity to each peptide was significantly associated with arthritis development (p<0.001). The ACPA repertoire did not differ between patients who did or did not develop arthritis. Among aCCP-positive patients, patients recognising two or more additional citrullinated peptides developed arthritis more often (p=0.04). The number of recognised peptides was positively associated with the aCCP level (p<0.001). Crossreactivity between different peptides was minimal. Conclusions Arthritis development is not associated with recognition of a specific citrullinated peptide once joint complaints are present. The ACPA repertoire in some patients with arthralgia is expanded. High aCCP levels are associated with a qualitatively broad ACPA repertoire. Patients with an extended ACPA repertoire have a higher risk of developing arthritis.

Antibodies to mutated citrullinated vimentin and disease activity score in early arthritis: a cohort study

IntroductionThe aim of our study was to investigate the association between arthritic disease activity and antibodies to mutated citrullinated vimentin (anti-MCV), because such a relation has been suggested.MethodsAnti-MCV levels were measured in 162 patients with early arthritis (123 with rheumatoid arthritis and 39 with undifferentiated arthritis) at baseline and at 1 and 2 years of follow up. Disease activity was measured using the disease activity score (Disease Activity Score based on 28 joints [DAS28]) and serum C-reactive protein. General estimation equation analysis was used to assess the relation between anti-MCV levels and DAS28 over time.ResultsBoth, anti-MCV levels and DAS28 exhibited a significant decrease during the first and second year. However, the association between anti-MCV levels and DAS28, adjusted for dependency on sequential measurements within one individual, was very low (β = 0.00075). In a population of patients with rheumatoid arthritis or undifferentiated arthritis, anti-MCV had a specificity of 92.3% and a sensitivity of 59.3% when using the recommended cut-off of 20 U/ml. Specificity and sensitivity of antibodies against second-generation cyclic citrullinated peptide, using the recommended cut-off value of 25 U/ml, were 92.1% and 55.3%, respectively. Anti-MCV-positive early arthritis patients had significantly higher Sharp-van der Heijde score, erythrocyte sedimentation rate and C-reactive protein levels than did anti-MCV-negative patients at all time points (P < 0.005), but DAS28 was higher in anti-MCV-positive patients at 2 years of follow up only (P < 0.05).ConclusionBecause the correlation between anti-MCV levels and parameters of disease activity was very low, we conclude that it is not useful to monitor disease activity with anti-MCV levels.

Bone metabolism is altered in preclinical rheumatoid arthritis

Radiographic damage and its progression in early rheumatoid arthritis (RA) can be predicted by markers and regulators of bone metabolism. Studies of bone formation in RA patients measuring osteocalcin or the N-terminal telopeptide of type I procollagen (P1NP) have produced varying results, whereas measurements of bone resorption using serum or urine C-terminal crosslink of type I collagen (β-CTX) mostly show increased values.1,–,3 RA patients often have elevated serum levels of the osteoclast-activating cytokine receptor activator of nuclear factor κB ligand (RANKL), as well as of osteoprotegerin, which prevents osteoclast activation.4 We previously reported increased levels of autoantibodies and acute phase reactants …

Different properties of ACPA and IgM-RF derived from a large dataset: further evidence of two distinct autoantibody systems

IntroductionThe aim of this study was to examine seroconversion and the relationship with age and inflammation of autoantibodies in a large group of patients attending an outpatient rheumatology clinic.MethodsLevels of antibodies to citrullinated proteins/peptides (ACPAs) and IgM rheumatoid factor (IgM-RF) were determined in 22,427 samples collected from 18,658 patients. The diagnosis was derived from a diagnosis registration system. The degree of seroconversion in repeated samples and the correlation of levels with age and inflammatory markers were determined for ACPA and IgM-RF in rheumatoid arthritis (RA) and non-RA patients.ResultsSeventy-one percent of RA patients (n = 1,524) were ACPA-positive and 53% were IgM-RF-positive; in non-RA patients (n = 2,245), the corresponding values were 2% and 4%, respectively. In patients with at least two samples (n = 3,769), ACPA status was more stable than IgM-RF status in RA patients. ACPA- or IgM-RF-negative non-RA patients seldom became positive. ACPA positivity was unrelated to age in both RA and non-RA patients. IgM-RF positivity was unrelated to age in RA patients; however, it increased with age in non-RA patients. The correlation between autoantibody levels and inflammatory markers was low in general and was somewhat higher for IgM-RF than for ACPA.ConclusionsACPA status is more stable in time and with increasing age than IgM-RF status, further establishing its role as a disease-specific marker. ACPA and IgM-RF levels are only moderately correlated with markers of inflammation.

Improvement of Thyroid Function in Hypothyroid Patients with Rheumatoid Arthritis After 6 Months of Adalimumab Treatment: A Pilot Study

Objective. Rheumatoid arthritis (RA) is characterized by high levels of cytokines such as tumor necrosis factor (TNF). TNF appears to have an etiologic role in thyroid dysfunction, and thyroid dysfunction is a common comorbidity in RA. Anti-TNF treatment might limit thyroid dysfunction. Thus, changes in thyroid hormones were studied during TNF-blocking therapy in patients with RA. Methods. At baseline and after 6 months’ treatment with adalimumab, thyroid function [thyroid-stimulating hormone (TSH), free thyroxine (fT4), and antibodies against thyroid peroxidase (TPOabs)] were assessed in 138 consecutive adalimumab-treated patients with RA who were naive for TNF-blocking agents. Patients were categorized as hypothyroid, hyperthyroid, or euthyroid. In these groups, changes in thyroid function were determined. Results. Prevalences of hypothyroidism, hyperthyroidism, and TPOabs were 13%, 5%, and 15%, respectively. After 6 months, TPOabs decreased from 267 to 201 IU/ml (p = 0.048). In hypothyroid patients without concomitant L-thyroxine, a trend for declining levels of TSH was observed. Subgroup analysis revealed that in patients who were hypothyroid and TPOabs-positive and L-thyroxine-naive, TSH levels decreased significantly, from 12.5 (interquartile range 6.7–18.4) to 7.1 (interquartile range 4.9–13.8) mU/l (p = 0.043). Conclusion. Anti-TNF treatment improves thyroid function in hypothyroid patients with RA (especially in those who are L-thyroxine-naive and TPOabs-positive), providing further evidence that inflammatory cytokines such as TNF have a pathogenic role in thyroid dysfunction.