Reactivity of Rheumatoid Arthritis-Associated Citrulline-Dependent Antibodies to Epstein-Barr Virus Nuclear Antigen1-3.

Ilaria Fanelli,Paul Robert Hansen,Jette Lautrup Frederiksen,Paolo Rovero,Gunnar Houen,Nicole Hartwig Trier

doi:10.3390/antib11010020

Abstract

Rheumatoid arthritis (RA) is a chronic disease which causes joint inflammation and, ultimately, erosion of the underlying bone. Diagnosis of RA is based on the presence of biomarkers, such as anti-citrullinated protein antibodies (ACPA) and rheumatoid factors, along with clinical symptoms. Much evidence points to a link between the Epstein-Barr virus and RA. In this study, we analyzed ACPA reactivity to citrullinated peptides originating from Epstein-Barr nuclear antigens (EBNA1, EBNA2, and EBNA3) in order to elaborate the diagnostic potential of citrullinated EBNA peptides. Moreover, ACPA cross-reactivity to citrullinated peptides from myelin basic protein (MBP) was analyzed, as citrullinated MBP recently was described to be associated with multiple sclerosis, and some degree of sequence homology between MBP and citrullinated EBNA exists. A peptide from EBNA2, (EBNA2-A, GQGRGRWRG-Cit-GSKGRGRMH) reacted with approximately 70% of all RA sera, whereas only limited reactivity was detected to EBNA1 and EBNA3 peptides. Moreover, screening of ACPA reactivity to hybrid peptides of EBNA3-A (EPDSRDQQS-Cit-GQRRGDENRG) and EBNA2-A and peptides containing citrulline close to the N-terminal confirmed that ACPA sera contain different populations of ACPAs. No notable ACPA reactivity to MBP peptides was found, confirming that ACPAs are specific for RA, and that other factors than the presence of a central Cit-Gly motif are crucial for antibody binding. Collectively, these findings illustrate that citrullinated EBNA2 is an optimal candidate for ACPA detection, supporting current evidence that EBV is linked to RA onset.

Highlights

Rheumatoid arthritis (RA) is a chronic systemic disease, which is characterized by inflammation in the synovial tissue of joints [1,2]
No significant difference in RA reactivity was found to EBNA1-B and EBNA1-C compared to HC samples (p = 0.6310 for EBNA1-B and p = 0.2044 for EBNA1-C), as only 11 and 18% of RA sera reacted to EBNA1-C and EBNA1-B, respectively
RA is a chronic inflammatory disease, where the serologic biomarkers anti-citrullinated protein antibodies (ACPA) and rheumatoid factors (RF) are central for the diagnosis and monitoring of RA

Summary

Introduction

Rheumatoid arthritis (RA) is a chronic systemic disease, which is characterized by inflammation in the synovial tissue of joints [1,2]. RA is diagnosed according to the EULAR/ACR classification criteria revised in 2010, which, beyond clinical disease manifestations, comprise serological biomarkers, such as rheumatoid factors (RF) and anti-citrullinated protein antibodies (ACPA) [1,3,6]. While RFs IgA and IgM isotypes are directed to the Fc region of IgG, ACPAs are mainly of the IgG isotype, and are specific for citrullinated targets [7,8]. RFs are found approximately in 60–80% of RA cases, and occasionally in healthy individuals and in individuals suffering from systemic lupus erythematosus (SLE), Sjogren’s syndrome (SjS), or affected by infections [9–11]. ACPAs have been detected up to 14 years before the clinical symptoms of RA [17,18]

Methods

Results

Conclusion