Identification of an immunodominant peptide from citrullinated tenascin-C as a major target for autoantibodies in rheumatoid arthritis

Authors

• Anja Schwenzer, University of Oxford
• Xia Jiang, Institute of Environmental Medicine, Karolinska
• Ted R. Mikuls, University of Nebraska Medical Center
• Jeffrey B. Payne, University of Nebraska Medical CenterFollow
• Harlan R Sayles, University of Nebraska, Medical Center, Omaha
• Anne-Marie Quirke, University of Oxford
• Benedikt M Kessler, University of Oxford
• Roman Fischer, University of Oxford
• Patrick J. Venables, University of OxfordFollow
• Karin Lundberg, Karolinska Institutet
• Kim S Midwood, University of Oxford

Document Type

Article

Date of this Version

2015

Citation

Schwenzer A, et al. Ann Rheum Dis 2015;0:1–8. doi:10.1136/annrheumdis-2015-208495 1

Comments

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license

Abstract

Objectives We investigated whether citrullinated tenascin-C (cTNC), an extracellular matrix protein expressed at high levels in the joints of patients with rheumatoid arthritis (RA), is a target for the autoantibodies in RA.

Methods Citrullinated sites were mapped by mass spectrometry in the fibrinogen-like globe (FBG) domain of tenascin-C treated with peptidylarginine deiminases (PAD) 2 and 4. Antibodies to cyclic peptides containing citrullinated sites were screened in sera from patients with RA by ELISA. Potential cross-reactivity with wellestablished anticitrullinated protein antibody (ACPA) epitopes was tested by inhibition assays. The autoantibody response to one immunodominant cTNC peptide was then analysed in 101 pre-RA sera (median 7 years before onset) and two large independent RA cohorts.

Results Nine arginine residues within FBG were citrullinated by PAD2 and PAD4. Two immunodominant peptides cTNC1 (VFLRRKNG-cit-ENFYQNW) and cTNC5 (EHSIQFAEMKL-cit-PSNF-cit-NLEG-cit-cit-KR) were identified. Antibodies to both showed limited crossreactivity with ACPA epitopes from α-enolase, vimentin and fibrinogen, and no reactivity with citrullinated fibrinogen peptides sharing sequence homology with FBG. cTNC5 antibodies were detected in 18% of pre-RA sera, and in 47% of 1985 Swedish patients with RA and 51% of 287 North American patients with RA. The specificity was 98% compared with 160 healthy controls and 330 patients with osteoarthritis.

Conclusions There are multiple citrullination sites in the FBG domain of tenascin-C. Among these, one epitope is recognised by autoantibodies that are detected years before disease onset, and which may serve as a useful biomarker to identify ACPA-positive patients with high sensitivity and specificity in established disease.