Evaluation of autoantibodies against vimentin and α-enolase in rheumatoid arthritis patients

Abstract

Introduction: Rheumatoid arthritis (RA) is categorized as an autoimmune disease with a frequency of 0.2-1% worldwide. It is reported that various autoantibodies are produced in the RA population, particularly against citrullinated peptides. Among various candidate markers for RA diagnosis, the citrullinated proteins have the highest specificity and sensitivity for both diagnosis and prognosis of RA. Anti-mutated citrullinated vimentin and α-enolase constitute a new class of autoantibodies for early detection of RA.

Material and methods: 45 serum samples and 19 synovial fluid (SF) specimens collected from RA patients were considered for American College of Rheumatology criteria and 20 serum samples and 10 SF specimens were provided from healthy subjects as a control group. To assess the quantity of anti-citrullinated protein antibodies (ACPA), anti-mutated citrullinated vimentin (MCV) and anti-α-enolase in the serum and SF of RA patients were determined by the enzyme-linked immunosorbent assay (ELISA) method. For the evaluation of disease activity and joint destruction, we used the Disease Activity Score of 28 joints based on erythrocyte sedimentation rate (ESR) Disease Activity Score 28 (DAS28). Furthermore, to measure the molecular weight of vimentin and α-enolase, electrophoresis on 10% SDS-PAGE was performed as described before.

Results: The anti-α-enolase level among serum samples from RA patients was significantly higher than in healthy subjects (4.49 ±0.20 ng/ml vs. 0.76 ±0.12 ng/ml) (p < 0.001). There was a direct relation between α-enolase quantity and (rheumatoid factor) RF and C-reactive protein (CRP) levels. The mean ESR value in positive and negative ACPA patients was 38.2 ±22.6 mm/h and 9.2 ±5.8 mm/h respectively (p < 0.0001). The mean DAS28-ESR was 3.3. The level of anti-MCV in the serum of RA patients (244.6 ±53.3 U/ml) was higher than in serum of the healthy group (148.73 ±71.8) (p < 0.0001). The level of anti-MCV in the SF of patients was 687.5 ±148.4 U/ml.

Conclusions: In conclusion, both autoantibodies against MCV and α-enolase are two important markers that increase in serum and SF of RA patients and are specific for diagnosis of RA disease.

Keywords: Disease Activity Score; anti-citrullinated peptide antibodies; autoantibodies; rheumatoid arthritis; synovial fluid; vimentin; α-enolase.

Fig. 1

Anti-α-enolase concentrations in serum and synovial fluid of healthy and patient group.

Fig. 2

Comparison of anti-mutated citrullinated vimentin concentrations in serum and synovial fluid (healthy and patient group).

Fig. 3

Evaluation of enzyme in serum (A) and synovial fluid (SF) (B) on 10% SDS-PAGE. The molecular weight of α-enolase is about 47 kDa. In (A), lanes 1 and 2 indicate healthy serum samples, and lanes 3 and 4 belong to the rheumatoid arthritis (RA) serum samples (B). Lane M indicates protein marker. All lanes indicate the SF samples from RA patients.

Fig. 4

Evaluation of vimentin in serum (A) and synovial fluid (SF) (B) on 10% SDS-PAGE. The molecular weight of vimentin is about 57 kDa. In (a), lanes 1, 2, 3 and 6 indicate rheumatoid arthritis (RA) serum samples, and lanes 4, 5 and 7 belong to the healthy serum samples. In (b) lanes 1, 2, 3 and 4 indicate RA SF specimens, and lanes 5 and 6 belong to the healthy SF samples.