Disappearance of anti-MDA-5 autoantibodies in clinically amyopathic DM/interstitial lung disease during disease remission.
OBJECTIVE
Autoantibodies against melanoma differentiation-associated gene 5 (MDA-5) are one of the serological markers for DM. Anti-MDA-5 antibodies are especially associated with rapidly progressive interstitial lung disease (ILD) in amyopathic DM (ADM). It is known that the antibody status of anti-ENAs does not generally change significantly with disease course. For anti-MDA-5 antibodies, however, few longitudinal studies have investigated such changes. This study aimed to establish a quantitative assay for anti-MDA-5 antibodies towards assessing the long-term outcome of ADM patients who had anti-MDA-5 antibodies.


METHODS
We established ELISA for measuring anti-MDA-5 antibody levels using in vitro transcription and translation recombinant protein. The antibody levels were measured at different time points in 11 clinically ADM patients who tested positive for the anti-MDA-5 antibody on their first visit (range of follow-up 3 months to 16 years).


RESULTS
At the stage of clinical remission, six patients received no medication and the four others received low-dose CS. ELISA showed that anti-MDA-5 antibodies disappeared in nine of the patients and fell to just above the cut-off in one patient; in the patient who died, the antibodies remained.


CONCLUSIONS
Our results suggest that anti-MDA-5 antibodies may be useful as a marker for monitoring disease activity in ILD complicated with ADM. Serial monitoring at short intervals is required to evaluate whether anti-MDA-5 antibody levels correlate with ADM disease activity.
Division of Connective Tissue Disease and Autoimmunity, Department of Dermatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan. ymuro@med.nagoya-u.ac.jp
Yoshinao
Y
Muro
Kazumitsu
K
Sugiura
Kei
K
Hoshino
Masashi
M
Akiyama
D000328:Adult; D001323:Autoantibodies / Q000276:immunology*; D015415:Biomarkers; D053487:DEAD-box RNA Helicases / Q000276:immunology*; D003882:Dermatomyositis / Q000150:complications / Q000276:immunology*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D000072640:Interferon-Induced Helicase, IFIH1; D017563:Lung Diseases, Interstitial / Q000150:complications / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis
D001323:Autoantibodies; D015415:Biomarkers; C452815:IFIH1 protein, human; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1