LAUSR

Background Rheumatoid Arthritis (RA) patients with established disease can have autoantibodies reactive to a broad array of citrullinated antigens. Autoantibodies reactive against several citrullinated proteins can develop 10-15 years before the clinical onset of disease. Objectives We aimed to identify common patterns of citrullinated peptide reactivities that emerge among subjects during progression from a pre-disease state through diagnosis of RA. Methods 500 subjects with RA (based on ICD9-CM code) were identified from the Defense Medical Surveillance System. For each subject, up to four serum samples were obtained from the Department of Defense (DoD) serum repository: 1 from earliest time point before diagnosis (9.2 ± 2.0 years before, mean ± SD); one proximal to (immediately prior to or after) disease diagnosis (127 ± 125 days before diagnosis); plus 2 intermediate time points. A discovery subset of serum samples from 88 RA subjects confirmed to be positive for anti-citrullinated protein antibodies (ACPA) at the diagnosis-proximal time point (>5 U/mL for cyclic citrullinated peptide (CCP)-II test) was assessed for IgG antibodies to 36 antigens (24 citrullinated-peptide antigens among 14 proteins and 12 non-citrullinated antigens among 9 proteins) using a custom Luminex-based assay. Subjects testing above the upper limit of detection for the CCP-II test (300 U/mL) were considered ACPA-high (n=28), with the remainder considered moderate (n=60). Results For the group of ACPA-high subjects at the diagnosis-proximal time point, average IgG autoantibody binding to 9 citrullinated peptide antigens (from 7 proteins: clusterin, enolase, fibrinogen A, fibrinogen B, fibronectin, filaggrin, vimentin) showed significant increases from the earliest through diagnosis-proximal time points at the population level (FDR<0.05). In ACPA-moderate subjects, IgG levels to only one antigen (citrullinated-fibronectin) had a nominally significant but small increase (mean +8%) during this time frame. Significant reactivity to the non-citrullinated antigens was not observed. In ACPA -high but not -moderate subjects, group averages for a composite score of the 9 citrullinated peptide antigens increased relative to the earliest time points, with increased average levels observable 6-years before diagnosis that steadily increased as approaching diagnosis. Patterns of increases in IgG to specific citrullinated peptides differed among subjects, for both ACPA -high and -moderate groups. In the ACPA-high group, 46% of subjects had ≥50% increase in a majority (≥5) of the 9 citrullinated-peptide antigen set and the remaining had ≥50% increase for at least 1 of the antigens. In contrast, in the ACPA-moderate group, 58% of subject did not achieve ≥50% increase for any of the 9 antigens and only 8% of subjects had ≥50% increase in a majority of the 9-antigen set. The most commonly increased IgG reactivities were for citrullinated -filaggrin and -fibrinogen A, with ≥50% increase in 64% of ACPA-high and 20% of ACPA-moderate subjects. Conclusion Novel patterns of citrullinated peptide autoantibody reactivities that begin to emerge on average about 6 years before diagnosis of RA have been identified in samples from the US DoD serum repository. Evaluation of specific anti-citrullinated peptide autoantibodies could potentially provide sensitive, patient-tailored biomarkers to monitor disease trajectories as at-risk individuals progress to clinically-defined RA. Disclosure of Interests:  Matthew J Loza Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Sunil Nagpal Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Renee Laird: None declared, Suzanne Cole Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Frederic Baribaud Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Ian Anderson Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Navin Rao Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Mark Riddle: None declared, Chad Porter: None declared