This confirmed the feasibility of using a screening questionnaire for eliciting population-based estimates of OA. In France, it increases with age and is greater among women above the age of 50. The geographical disparity of hip and knee OA parallels the distribution of obesity. Study registration ID number 906297 at http://www.clinicaltrials.gov/.

No abstract

Autoantibodies reactive to α36-50Cit₃₈,₄₂ and β60-74Cit₆₀,₇₂,₇₄ form two distinct, non-overlapping subfamilies of ACPA that, together, cover practically all the ACPA reactivity to citrullinated fibrinogen and to CCP2 antigens. In established RA, anti-β60-74Cit₆₀,₇₂,₇₄ autoantibodies show diagnostic indexes similar to those of anti-CCP2.

No abstract

Our study confirms the relationship between OA and HD, particularly as defined based on the HTE angle.

No abstract

Although several infectious agents and particularly Epstein-Barr virus (EBV) have been suspected to be involved in aetiology of rheumatoid arthritis (RA), their role still remains elusive. Almost 80% of RA sera contain antibodies to citrullinated proteins/peptides. Among them, the autoantibodies to citrullinated human fibrinogen (AhFibA) are composed of two non-cross-reactive subsets directed to immunodominant epitopes borne by the α36-50Cit and β60-74Cit fibrin peptides. RA sera also contain antibodies towards the citrullinated EBNA35-58Cit peptide derived from the EBNA-1 protein of EBV. Here, using a large cohort of RA patients and controls, we showed that for a diagnostic specificity of 98.5%, 47% of the AhFibA-positive patients were anti-EBNA35-58Cit-positive and that almost all (98.5%) the anti-EBNA35-58Cit-positive were AhFibA-positive, whereas 86% were anti-β60-74Cit-positive and only 43% anti-α36-50Cit-positive. AhFibA, anti-EBNA35-58Cit- and anti-β60-74Cit-antibody titres were significantly correlated. Competition assays showed that anti-EBNA35-58Cit antibodies are highly cross-reactive with the β60-74Cit peptide. The demonstration that a citrullinated peptide derived from the EBNA-1 protein of EBV presents a molecular mimicry with human citrullinated fibrin constitutes an additional argument for a possible role of EBV in RA aetiopathogeny.

Quantification of Abs toward a single epitope is critical to understanding immunobiological processes. In autoimmunity, the prognostic value of the serological profiles of patients draws much attention, but the detection of Abs toward a single epitope is not well controlled. Particularly, the rheumatoid arthritis (RA)–specific anti–citrullinated protein/peptide Abs (ACPA) are specific to a two-atom change on arginyl residues and are considered a heterogeneous family of Abs. As a model, we studied ACPA to decipher how peptide features used as immunosorbent impact Ab detection. We synthesized 30 peptides encompassing immunodominant epitopes of citrullinated fibrin differing by their length and biotin location and tested them using ELISA with 120 sera from RA and non-RA rheumatic disease controls, generating over 3000 experimental measurements. We showed that minor molecular changes in peptide chemical structure had dramatic consequences. Even when peptides exhibited the same epitope, measured Ab titers were extremely variable, and patients’ seropositivity was discordant in up to 50% of cases. The distance between epitope and biotin was the most critical parameter for efficient Ab detection irrespective of biotin position or peptide length. Finally, we identified a 15-mer peptide bearing a single citrullinated epitope detecting almost all ACPA-positive sera, thus revealing a high degree of homogeneity in RA autoimmune response. This integrative analysis deciphers the dramatic impact of the molecular design of peptide-based technologies for epitope-specific Ab quantification. It provides a model for assay development and highlights that the studies using such technologies can give a wrong perception of biological processes and therefore that medical use of data must be cautious.