Presence of autoantibodies to the glycolytic enzyme α-enolase in sera from patients with early rheumatoid arthritis

Authors


Abstract

Objective

To identify a new autoantigen/autoantibody population in rheumatoid arthritis (RA) sera.

Methods

Following a population-based recruitment effort, 255 patients with very early arthritis (median disease duration 4 months) were studied using different clinical, biologic, and radiologic assessments. After a followup period of 1 year, patients were classified as having RA (n = 145), non-RA rheumatic diseases (n = 70), and undifferentiated arthritis (n = 40). Patients' sera were analyzed by one-dimensional (1D) and 2D Western blotting. The recognized 50-kd protein was analyzed by matrix-assisted laser desorption ionization–time-of-flight (MALDI-TOF) mass spectrometry (MS). RA serum reactivities were evaluated against the recombinant protein synthesized by an in vitro coupled transcription–translation system.

Results

On 1D Western blots, 36 of the 145 RA sera bound to a 50-kd polypeptide. On 2D Western blots, anti–50-kd+ RA sera recognized a triplet of isoelectric point 6.5–7.0 and a molecular mass of 50 kd. The 3 spots of the triplet were analyzed by MALDI-TOF MS and were shown to correspond to human α-enolase. A goat anti-enolase antiserum, which recognized a band comigrating with the 50-kd antigen on 1D Western blots, gave a labeling pattern on 2D Western blots similar to that observed with anti–50-kd+ RA sera. Among the 36 RA sera that identified α-enolase in protein maps, only 8 recognized the recombinant (unmodified) α-enolase. The specificity of anti–α -enolase antibodies for RA was 97.1%. Half of the anti–α -enolase–positive RA patients were negative for both rheumatoid factor and antifilaggrin antibodies. The presence of anti–α-enolase antibodies was the greatest predictive factor of radiologic progression in the first 66 RA patients included.

Conclusion

Autoantibodies to α-enolase, an enzyme of the glycolytic pathway, are present in the sera of patients with very early RA and have potential diagnostic and prognostic value for RA.

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