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.