To define a novel RNA epitope recognized by serum from a patient with Sjögren's syndrome (SS) from a randomized RNA epitope library and investigate the epitope reactivity of the anti-RNA antibodies in patients with various connective tissue diseases.
Serum from a patient with SS was used to select ligands from a library of RNA oligomers with a central region of 25 degenerate nucleotides. Bound RNA was recovered by reverse transcription, PCR amplification, and subcloning. The relationship between the antibodies to the selected RNA and disease specificity was studied using immunoprecipitation.
From the random RNA library, several unique RNA sequences were obtained. Sera from 32 of 61 patients with SS (52.5%) precipitated with one of the selected RNA (TS1-RNA), whereas sera from 8 of 41 patients with systemic lupus erythematosus (19.5%) and 3 of 25 patients with rheumatoid arthritis (12.0%) precipitated. Although the frequency of reactivity to the TS1-RNA was higher in anti-SSA/Ro positive sera, the presence of either native or recombinant SSA/Ro antigen showed no detectable competition, and no apparent sequence homology was found between the TS1-RNA and hY RNA.
These data suggest that anti-TS1-RNA is a novel antibody against sequence-specific RNA in many patients with SS.