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Anti-Zo antibodies in Japanese myositis patients detected by a newly developed ELISA


1, 2, 3, 4, 5, 6, 7, 8

 

  1. Department of Dermatology, Nagoya University Graduate School of Medicine, Nagoya, Japan. ymuro@med.nagoya-u.ac.jp
  2. Division of Rheumatology, Department of Internal Medicine, Fujita Health University School of Medicine, Toyoake, Japan.
  3. Department of Respiratory Medicine, National Centre for Global Health and Medicine, Shinjuku, Tokyo, Japan.
  4. Department of Dermatology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
  5. Department of Dermatology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
  6. Division of Rheumatic Diseases, National Centre for Global Health and Medicine, Shinjuku, Tokyo, Japan.
  7. Division of Rheumatology, Department of Internal Medicine, Fujita Health University School of Medicine, Toyoake, Japan.
  8. Department of Dermatology, Nagoya University Graduate School of Medicine, Nagoya, Japan.

CER13719
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PMID: 33124571 [PubMed]

Received: 22/06/2020
Accepted : 07/09/2020
In Press: 09/10/2020

Abstract

OBJECTIVES:
The myositis-specific autoantibodies that characterise certain forms of idiopathic inflammatory myopathy (IIM) are useful for diagnosing dermatomyositis (DM) / polymyositis (PM) and predicting its prognosis. The autoantibody to phenylalanyl-tRNA synthetase (anti-Zo) has been identified as a disease marker antibody for anti-synthetase syndrome only in a UK cohort. Here we aim to establish an ELISA for the measurement of anti-Zo and to characterise the clinical features of Japanese patients who have this autoantibody.
METHODS:
Anti-Zo was investigated by immunoprecipitation with recombinant phenylalanyl-tRNA synthetase α/β proteins. The results were confirmed by immunoprecipitation-Western blotting with cell extract. Sera from patients with DM/PM (n=224) were screened by an ELISA with the recombinant proteins. Medical records were retrospectively reviewed to obtain detailed information on the clinical phenotypes of the anti-Zo-positive patients.
RESULTS:
Only two male patients were confirmed to have anti-Zo. Both patients had fever, myopathy, interstitial lung disease, and mechanic’s hands, and these clinical features are consistent with those of anti-synthetase syndrome. Another patient’s serum showed a higher level than the cut-off value for anti-phenylalanyl-tRNA synthetase α by our in-house ELISA, but was judged to be negative for anti-Zo by immunoprecipitation-Western blotting.
CONCLUSIONS:
This is the first report of anti-Zo-positive IIM patients from Asia. Although Japanese patients with anti-Zo have a clinical phenotype similar to that of Caucasian patients, further large cohort studies are necessary to confirm the frequency of anti-Zo in Japanese IIM patients. Our newly developed ELISA should be validated for sensitivity and specificity in large cohorts.

Rheumatology Article