EBV-encoded small RNA1 and nonresolving inflammation in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by perpetuated inflammation in multiple joints. To date, there is no cure for RA, and the causal factor for non-resolving inflammation in RA remains unclear. In this study, we initially observed expression of Epstein–Barr virus-encoded small RNA1 (EBER1) in the synovial tissue of all five patients who showed nonresolving RA inflammation. By contrast, EBER1 was detected in the synovial tissue of only one out of seven patients with advanced osteoarthritis (OA; p < 0.01, Fisher’s exact test). To confirm this finding, we conducted a second study on synovial tissue samples taken from 23 patients with nonresolving RA inflammation and 13 patients with OA. All synovial samples from patients with nonresolving inflammation of RA showed positive expression of EBER1 (23/23, 100%), whereas none of the synovial samples from patients with OA showed expression of EBER1 (0/13, 0%; p < 0.001, by Fisher’s exact test). In vitro, transfection of RA synovial fibroblasts with EBER1 induced the production of interleukin-6. Taken together, these data strongly suggest that nonresolving RA inflammation is strongly related to the presence of EBER1, which might be, at least partially, responsible for synovial fibroblast interleukin-6 production.