Altered immune response to glycine‐rich sequences of epstein‐barr nuclear antigen‐1 in patients with rheumatoid arthritis and systemic lupus erythematosus

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Abstract
Prior studies have shown that patients with rheumatoid arthritis (RA) have an increased number of circulating Epstein-Barr virus–infected B lymphocytes and elevated titers of antibody to Epstein-Barr nuclear antigen–1 (EBNA-1), the major nuclear antigen expressed in latently infected B cells. However, it is not known whether antibodies from RA patients recognize the same epitopes as antibodies from normal subjects. Most of the anti–EBNA-1 antibodies in normal subjects are directed at the glycine-alanine repeating region of the molecule. Antibodies specific for this region are also somewhat more prevalent in RA patients than in normal subjects. A panel of synthetic peptides derived from EBNA-1 was used to analyze the immune response to antigenic epitopes outside the glycine-alanine region, using the peptides as solid-phase antigen. Sera from RA patients and from systemic lupus erythematosus patients contained elevated levels of IgG antibodies to 2 non–glycine-alanine peptides and to 3 non–glycine-alanine peptides, respectively. Two of the 3 peptides are glycinerich, but antibodies that react with them are distinct from each other, as well as from those that react with the glycine-alanine epitope. Eight other peptides from the C-terminal portion of EBNA-1 either do not react with sera or show no difference between normal subjects and patient groups. The antibodies to the glycine-alanine peptide are enriched with k light chains, whereas antibodies to epitopes outside the glycinealanine region are not so restricted among k and λ light chains. Thus, RA patients and systemic lupus erythematosus patients have different antibody responses than do normal subjects, both quantitatively and qualitatively.

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