Lezlie A. Derber

Autoantibody Epitope Spreading in the Pre-Clinical Phase Predicts Progression to Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a prototypical autoimmune arthritis affecting nearly 1% of the world population and is a significant cause of worldwide disability. Though prior studies have demonstrated the appearance of RA-related autoantibodies years before the onset of clinical RA, the pattern of immunologic events preceding the development of RA remains unclear. To characterize the evolution of the autoantibody response in the preclinical phase of RA, we used a novel multiplex autoantigen array to evaluate development of the anti-citrullinated protein antibodies (ACPA) and to determine if epitope spread correlates with rise in serum cytokines and imminent onset of clinical RA. To do so, we utilized a cohort of 81 patients with clinical RA for whom stored serum was available from 1–12 years prior to disease onset. We evaluated the accumulation of ACPA subtypes over time and correlated this accumulation with elevations in serum cytokines. We then used logistic regression to identify a profile of biomarkers which predicts the imminent onset of clinical RA (defined as within 2 years of testing). We observed a time-dependent expansion of ACPA specificity with the number of ACPA subtypes. At the earliest timepoints, we found autoantibodies targeting several innate immune ligands including citrullinated histones, fibrinogen, and biglycan, thus providing insights into the earliest autoantigen targets and potential mechanisms underlying the onset and development of autoimmunity in RA. Additionally, expansion of the ACPA response strongly predicted elevations in many inflammatory cytokines including TNF-α, IL-6, IL-12p70, and IFN-γ. Thus, we observe that the preclinical phase of RA is characterized by an accumulation of multiple autoantibody specificities reflecting the process of epitope spread. Epitope expansion is closely correlated with the appearance of preclinical inflammation, and we identify a biomarker profile including autoantibodies and cytokines which predicts the imminent onset of clinical arthritis.

The number of elevated cytokines and chemokines in preclinical seropositive rheumatoid arthritis predicts time to diagnosis in an age-dependent manner.

OBJECTIVE To evaluate levels of biomarkers in preclinical rheumatoid arthritis (RA) and to use elevated biomarkers to develop a model for the prediction of time to future diagnosis of seropositive RA. METHODS Stored samples obtained from 73 military cases with seropositive RA prior to RA diagnosis and from controls (mean 2.9 samples per case; samples collected a mean of 6.6 years prior to diagnosis) were tested for rheumatoid factor (RF) isotypes, anti-cyclic citrullinated peptide (anti-CCP) antibodies, 14 cytokines and chemokines (by bead-based assay), and C-reactive protein (CRP). RESULTS Preclinical positivity for anti-CCP and/or ≥2 RF isotypes was >96% specific for future RA. In preclinical RA, levels of the following were positive in a significantly greater proportion of RA cases versus controls: interleukin-1α (IL-1α), IL-1β, IL-6, IL-10, IL-12p40, IL-12p70, IL-15, fibroblast growth factor 2, flt-3 ligand, tumor necrosis factor α, interferon-γ-inducible 10-kd protein, granulocyte-macrophage colony-stimulating factor, and CRP. Also, increasing numbers of elevated cytokines/chemokines were present in cases nearer to the time of diagnosis. RA patients who were ≥40 years old at diagnosis had a higher proportion of samples positive for cytokines/chemokines 5-10 years prior to diagnosis than did patients who were <40 years old at diagnosis (P < 0.01). In regression modeling using only case samples positive for autoantibodies highly specific for future RA, increasing numbers of cytokines/chemokines were predictive of decreased time to diagnosis, and the predicted time to diagnosis based on cytokines/chemokines was longer in older compared with younger cases. CONCLUSION Levels of autoantibodies, cytokines/chemokines, and CRP are elevated in the preclinical period of RA development. In preclinical autoantibody-positive cases, the number of elevated cytokines/chemokines is predictive of the time of diagnosis of future RA in an age-dependent manner.

Porphyromonas gingivalis and Disease-Related Autoantibodies in Individuals at Increased Risk of Rheumatoid Arthritis

OBJECTIVE To examine the relationship of Porphyromonas gingivalis to the presence of autoantibodies in individuals at risk of rheumatoid arthritis (RA). METHODS Study participants included the following: 1) a cohort enriched in subjects with HLA-DR4 and 2) subjects at risk of RA by virtue of having a first-degree relative with RA. None of the study subjects satisfied the American College of Rheumatology 1987 classification criteria for RA. Autoantibodies measured included anti-citrullinated protein antibody (ACPA; by second-generation anti-cyclic citrullinated peptide antibody enzyme-linked immunosorbent assay [ELISA]) and rheumatoid factor (RF; by nephelometry or ELISA for IgA, IgM, or IgG isotype). Individuals were considered autoantibody positive (n = 113) if they had ≥1 RA-related autoantibody; individuals were further categorized as high risk (n = 38) if they had ACPA or positive findings ≥2 assays for RF. Autoantibody-negative individuals (n = 171) served as a comparator group. Antibody to P gingivalis, P intermedia, and F nucleatum were measured. Associations of bacterial antibodies with group status were examined using logistic regression. RESULTS Anti-P gingivalis concentrations were higher in high-risk (P = 0.011) and autoantibody positive group (P = 0.010) than in the autoantibody negative group. There were no group differences in anti-P intermedia or anti-F nucleatum concentrations. After multivariable adjustment, anti-P gingivalis concentrations (but not anti-P intermedia or anti-F nucleatum) were significantly associated with autoantibody-positive and high-risk status (P < 0.05). CONCLUSION Immunity to P gingivalis, but not P intermedia or F nucleatum, is significantly associated with the presence of RA-related autoantibodies in individuals at risk of RA. These results support the hypothesis that infection with P gingivalis may play a central role in the early loss of tolerance to self antigens that occurs in the pathogenesis of RA.

Brief report: airways abnormalities and rheumatoid arthritis-related autoantibodies in subjects without arthritis: early injury or initiating site of autoimmunity?

OBJECTIVE To evaluate the presence of pulmonary abnormalities in rheumatoid arthritis (RA)-related autoantibody-positive subjects without inflammatory arthritis. METHODS Forty-two subjects who did not have inflammatory arthritis but were positive for anti-cyclic citrullinated peptide antibodies and/or ≥2 rheumatoid factor isotypes (a profile that is 96% specific for RA), 15 autoantibody-negative controls, and 12 patients with established seropositive early RA (<1-year duration) underwent spirometry and high-resolution computed tomography (HRCT) lung imaging. RESULTS The median age of autoantibody-positive subjects was 54 years, 52% were female, and 38% were ever-smokers; these characteristics were not significantly different from those of autoantibody-negative control subjects. No autoantibody-positive subject had inflammatory arthritis based on joint examination. HRCT revealed that 76% of autoantibody-positive subjects had airways abnormalities including bronchial wall thickening, bronchiectasis, centrilobular opacities, and air trapping, compared with 33% of autoantibody-negative controls (P = 0.005). The prevalence and type of lung abnormalities among autoantibody-positive subjects were similar to those among patients with early RA. In 2 autoantibody-positive subjects with airways disease, inflammatory arthritis classifiable as articular RA developed ∼13 months after the lung evaluation. CONCLUSION Airways abnormalities that are consistent with inflammation are common in autoantibody-positive subjects without inflammatory arthritis and are similar to airways abnormalities seen in patients with early RA. These findings suggest that the lung may be an early site of autoimmune-related injury and potentially a site of generation of RA-related autoimmunity. Further studies are needed to define the mechanistic role of lung inflammation in the development of RA.

Aberrant IgG galactosylation precedes disease onset, correlates with disease activity, and is prevalent in autoantibodies in rheumatoid arthritis†

OBJECTIVE To examine the association between aberrant IgG galactosylation and disease parameters in rheumatoid arthritis (RA). METHODS Analysis of N-glycan in serum samples from multiple cohorts was performed. The IgG N-glycan content and the timing of N-glycan aberrancy relative to disease onset were compared in healthy subjects and in patients with RA. Correlations between aberrant galactosylation and disease activity were assessed in the RA cohorts. The impact of disease activity, sex, age, anti-cyclic citrullinated peptide (anti-CCP) antibody titer, disease duration, and C-reactive protein level on aberrant galactosylation was determined using multivariate analysis. The N-glycan content was also compared between epitope affinity-purified autoantibodies and the remaining IgG repertoire in RA patients. RESULTS Our results confirm the aberrant galactosylation of IgG in RA patients as compared with healthy controls (mean +/- SD 1.36 +/- 0.43 versus 1.01 +/- 0.23; P < 0.0001). We observed a significant correlation between levels of aberrant IgG galactosylation and disease activity (Spearmans rho = 0.37, P < 0.0001). This correlation was higher in women (Spearmans rho = 0.60, P < 0.0001) than in men (Spearmans rho = 0.16, P = 0.10). Further, aberrant IgG galactosylation substantially predated the onset of arthritis and the diagnosis of RA (3.5 years) and resided selectively in the anticitrullinated antigen fraction. CONCLUSION Our findings identify aberrant IgG galactosylation as a dysregulated component of the humoral immune response in RA that begins prior to disease onset, associates with disease activity in a sex-specific manner, and resides preferentially in autoantibodies.

A prospective approach to investigating the natural history of preclinical rheumatoid arthritis (RA) using first-degree relatives of probands with RA

OBJECTIVE To describe a large, multicenter prospective cohort study of first-degree relatives (FDRs) of probands with rheumatoid arthritis (RA), and outline the use of such a study in investigating the natural history of RA development. METHODS A total of 1,058 FDRs, none of whom met the American College of Rheumatology criteria for RA, were enrolled in a prospective study investigating genetic and environmental influences on the development of RA-related autoimmunity. Demographic, epidemiologic, genetic, autoantibody, and physical examination data from the initial study enrollment visit were described for these FDRs, and the relationship was examined between genetic factors, autoantibodies, inflammation, and joint disease. RESULTS Fifty-five percent of the FDRs had > or =1 copy of the shared epitope, 20% had > or =1 copy of the PTPN22 polymorphism, and approximately 16% were positive for rheumatoid factor (RF; including isotypes) and/or anti-cyclic citrullinated peptide antibody. IgM-RF positivity is associated with > or =1 tender joint on examination (odds ratio [OR] 2.50, 95% confidence interval [95% CI] 1.27-4.89; P < 0.01) and elevated C-reactive protein (CRP) levels (OR 5.31, 95% CI 1.45-19.52; P = 0.01). CONCLUSION FDRs without RA demonstrate high prevalences of genetic risk factors and RA-related autoantibodies. Additionally, an RF association with tender joints and elevated CRP levels suggests that autoantibodies are a valid intermediate marker of RA-related autoimmunity in this cohort. This prospective FDR cohort will be a valuable resource for evaluating the relationship between genetic and epidemiologic factors and the development of RA-related autoimmunity.

Sputum Autoantibodies in Patients With Established Rheumatoid Arthritis and Subjects at Risk of Future Clinically Apparent Disease

OBJECTIVE To evaluate the generation of rheumatoid arthritis (RA)-related autoantibodies in the lung. METHODS Simultaneous collection of serum and induced sputum was performed in 21 healthy controls, 49 at-risk subjects without inflammatory arthritis but at risk of RA due to family history or seropositivity for anti-citrullinated protein antibodies, and 14 subjects with early RA. Samples were tested for anti-cyclic citrullinated peptide 2 (anti-CCP2), anti-CCP3, anti-CCP3.1, rheumatoid factor isotypes IgM, IgG, and IgA, and total IgM, IgG, and IgA. RESULTS One or more autoantibodies were present in sputum of 39% of at-risk seronegative subjects, 65% of at-risk seropositive subjects, and 86% of subjects with early RA. In at-risk seronegative subjects, the rate of anti-CCP3.1 positivity and the median number of autoantibodies were elevated in sputum versus serum. In subjects with early RA, the rate of positivity for several individual autoantibodies and the median number of autoantibodies were higher in serum than in sputum. Results in at-risk seropositive subjects were intermediate between these groups. In at-risk subjects with autoantibody positivity in sputum, the ratios of autoantibody to total Ig were higher in sputum than in serum, suggesting that these autoantibodies are generated or sequestered in the lung. CONCLUSION RA-related autoantibodies are detectable in sputum in subjects at risk of RA and in subjects with early RA. In a subset of at-risk subjects, the presence of sputum autoantibodies in the absence of seropositivity, and the increased autoantibody-to-total Ig ratios in sputum, suggest that the lung may be a site of autoantibody generation in the early development of RA. These findings suggest an important role of the lung in the pathogenesis of RA.

Multiple cytokines and chemokines are associated with rheumatoid arthritis-related autoimmunity in first-degree relatives without rheumatoid arthritis: Studies of the Aetiology of Rheumatoid Arthritis (SERA)

Objective We investigated whether rheumatoid arthritis (RA)-related autoantibodies were associated with systemic inflammation in a prospective cohort of first-degree relatives (FDRs) of RA probands, a population without RA but at increased risk for its future development. Methods We studied 44 autoantibody positive FDRs, of whom 29 were rheumatoid factor (RF) positive, 25 were positive for the high risk autoantibody profile (HRP), that is, positive for anti-cyclic citrullinated peptide and/or for at least two RF IgM, IgG or IgA isotypes, and nine FDRs who were positive for both; and 62 FDRs who were never autoantibody positive. Twenty-five cytokines/chemokines were measured using a bead-based assay in serum. As a comprehensive measure of inflammation, we calculated a Cytokine Score by summing all cytokine/chemokine levels, weighted by their regression coefficients for RA-autoantibody association. We compared C-reactive protein, individual cytokines/chemokines and Cytokine Score to the outcomes: positivity for RF and for the HRP using logistic regression. Results Adjusting for age, sex, ethnicity and ever smoking, the Cytokine Score and levels of IL-6 and IL-9 were associated with both RF and HRP. IL-2, granulocyte macrophage-colony stimulating factor (GM-CSF), and interferon (IFN)-γ were associated with HRP only. Associations between the Cytokine Score and RF and HRP positivity were replicated in an independent military personnel cohort. Conclusions In first-degree relatives of patients with RA, RA-related autoimmunity is associated with inflammation, as evidenced by associations with multiple cytokines and chemokines.

Autoimmunity to Peptidyl Arginine Deiminase Type 4 Precedes Clinical Onset of Rheumatoid Arthritis

OBJECTIVE To determine whether antibodies against peptidyl arginine deiminase type 4 (PAD-4) are present in the preclinical phase of rheumatoid arthritis (RA) and to compare the timing and extent of their appearance with those of other preclinical autoantibodies. METHODS Prediagnosis serum samples from 83 patients with RA were evaluated for the presence of anti-PAD-4 antibody, anti-cyclic citrullinated peptide (anti-CCP) antibody, and rheumatoid factor. In addition, a control cohort (n = 83) matched by age, sex, race, number of serum samples, and duration of serum storage was tested for the presence of anti-PAD-4 antibody to determine its sensitivity and specificity for the subsequent development of RA. RESULTS Fifteen of 83 patients with RA (18.1%) had at least 1 prediagnosis sample positive for anti-PAD-4. One of 83 control subjects (1.2%) had at least 1 positive sample, resulting in a sensitivity and specificity of 18.1% and 98.8%, respectively, of anti-PAD-4 for the future development of RA. The mean duration of anti-PAD-4 positivity prior to clinical diagnosis was 4.67 years. Anti-PAD-4 positivity was associated with anti-CCP positivity (odds ratio 5.13 [95% confidence interval 1.07-24.5]). In subjects with prediagnosis samples that were positive for both antibodies, anti-CCP positivity predated anti-PAD-4 positivity in 9 of 13 cases (69%). CONCLUSION Autoantibodies to PAD-4 are present during the preclinical phase of RA in a subset of patients and are associated with anti-CCP positivity. Further exploration is needed regarding the timing of appearance and disease-related effects of PAD-4 autoimmunity.

Plasma 25,OH vitamin D concentrations are not associated with rheumatoid arthritis (RA)-related autoantibodies in individuals at elevated risk for RA.

Objective. To evaluate the association between rheumatoid arthritis (RA)-related autoantibodies and plasma 25,OH vitamin D in subjects at risk for RA. Methods. In 1210 subjects without RA, 76 were positive for anti-cyclic citrullinated peptide antibodies or for at least 2 rheumatoid factors (RF; by nephelometry: RF-IgM, RF-IgG, RF-IgA). 25,OH vitamin D was measured in these cases and 154 autoantibody-negative controls from this cohort. Results. 25,OH vitamin D levels did not differ between cases and controls (adjusted OR 1.23, 95% CI 0.93–1.63). Conclusion. Vitamin D concentrations are not associated with RA-related autoimmunity in unaffected subjects at increased risk for RA.