Association of Antibodies to Prevotella copri in Anti-Cyclic Citrullinated Peptide-Positive Individuals At Risk of Developing Rheumatoid Arthritis and in Patients With Early or Established Rheumatoid Arthritis.

Objective: Prevotella copri (P copri), a gut commensal, has been reported to be an immune-relevant organism in individuals with rheumatoid arthritis (RA). This study sought to evaluate anti-P copri (anti-Pc) antibody responses in our participant cohorts and to determine when in the natural history of RA such responses develop.

Methods: We analyzed serum levels of immunoglobulin A (IgA) and IgG antibodies from a 27-kd protein of P copri (anti-Pc-p27), an immunogenic P copri protein, in study participants at risk of developing RA, participants who transitioned to RA, participants with early RA (<1 year of disease), and participants with established RA, with comparisons made to their matched controls.