Manabu Fujimoto1, Akihiro Murakami2, Shunsuke Kurei2, Naoko Okiyama3, Atsushi Kawakami4, Michiaki Mishima5, Shinji Sato6, Mariko Seishima7, Takafumi Suda8, Tsuneyo Mimori9, Kazuhiko Takehara10, Masataka Kuwana11. 1. Department of Dermatology, School of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan. Electronic address: mfujimoto@md.tsukuba.ac.jp. 2. Medical & Biological Laboratories Co., Ltd., 4-5-3 10F, Sakae, Naka-ku, Nagoya, Aichi 406-0008, Japan. 3. Department of Dermatology, School of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan. 4. Unit of Translational Medicine, Department of Immunology and Rheumatology, Nagasaki University School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki City, Nagasaki 852-8501, Japan. 5. Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto City, Kyoto 606-8501, Japan. 6. Division of Rheumatology, Department of Internal Medicine, Tokai University, School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan. 7. Department of Dermatology, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu City, Gifu 501-1194, Japan. 8. Second Division, Department of Internal Medicine, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi, Hamamatsu, Shizuoka 431-3192, Japan. 9. Department of Rheumatology and Clinical Immunology, Graduate School of Medicine, Kyoto University, Kyoto, Yoshida-Honmachi, Sakyo-ku, Kyoto City, Kyoto 606-8501, Japan. 10. Department of Dermatology, School of Medicine, Institute of Medical, Pharmaceutical, and Health Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa 920-8641, Japan. 11. Department of Allergy and Rheumatology, Nippon Medical School Graduate School of Medicine, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan.
Abstract
BACKGROUND: Autoantibodies against transcriptional intermediary factor 1 (TIF1) and Mi-2 are selectively detected in patients with dermatomyositis (DM). To measure these antibodies readily, the development of reliable ELISA systems has been needed. OBJECTIVE: This study aimed to establish enzyme-linked immunosorbent assays (ELISAs) for anti-TIF1γ and anti-Mi-2β antibodies (Abs) and to assess their utility. METHODS: Serum samples were obtained from 104 patients with classic DM, 68 with clinically amyopathic DM (CADM) and 70 with polymyositis, who were followed up at 8 medical centers across Japan. Serum samples from 190 patients with other connective tissue diseases (CTDs) and 123 healthy individuals were also assessed. Serum antibody levels were examined by ELISAs coated with full-length TIF1γ or Mi-2β proteins produced by a baculovirus expression system. To assess the cross-reactivity, partial-length Mi-2β proteins with or without mutations were produced and examined for reactivity. RESULTS: When compared with immunoprecipitation assay, anti-TIF1γ Ab ELISA showed 100% sensitivity and 100% specificity, while anti-Mi-2β Ab ELISA showed 100% sensitivity and 99.6% specificity. Anti-TIF1γ Ab was positive in 30 (28.8%) with classic DM and 4 (5.9%) with CADM, whereas 14 (13.5%) with classic DM, but none with CADM, were positive for anti-Mi-2β Ab. Of 30 anti-TIF1γ Ab-positive DM patients, 23 (67.6%) had malignancy. Anti-Mi-2β Ab-positive serum samples exhibited modest cross-reactivity with the TIF1γ protein due to the homologous amino acid sequence containing cysteines in their plant homeodomains. CONCLUSION: The current study demonstrates the utility of newly established ELISAs for anti-TIF1γ and anti-Mi-2β Abs, which can serve as easier detection systems for routine testing.
BACKGROUND: Autoantibodies against transcriptional intermediary factor 1 (TIF1) and Mi-2 are selectively detected in patients with dermatomyositis (DM). To measure these antibodies readily, the development of reliable ELISA systems has been needed. OBJECTIVE: This study aimed to establish enzyme-linked immunosorbent assays (ELISAs) for anti-TIF1γ and anti-Mi-2β antibodies (Abs) and to assess their utility. METHODS: Serum samples were obtained from 104 patients with classic DM, 68 with clinically amyopathic DM (CADM) and 70 with polymyositis, who were followed up at 8 medical centers across Japan. Serum samples from 190 patients with other connective tissue diseases (CTDs) and 123 healthy individuals were also assessed. Serum antibody levels were examined by ELISAs coated with full-length TIF1γ or Mi-2β proteins produced by a baculovirus expression system. To assess the cross-reactivity, partial-length Mi-2β proteins with or without mutations were produced and examined for reactivity. RESULTS: When compared with immunoprecipitation assay, anti-TIF1γ Ab ELISA showed 100% sensitivity and 100% specificity, while anti-Mi-2β Ab ELISA showed 100% sensitivity and 99.6% specificity. Anti-TIF1γ Ab was positive in 30 (28.8%) with classic DM and 4 (5.9%) with CADM, whereas 14 (13.5%) with classic DM, but none with CADM, were positive for anti-Mi-2β Ab. Of 30 anti-TIF1γ Ab-positive DMpatients, 23 (67.6%) had malignancy. Anti-Mi-2β Ab-positive serum samples exhibited modest cross-reactivity with the TIF1γ protein due to the homologous amino acid sequence containing cysteines in their plant homeodomains. CONCLUSION: The current study demonstrates the utility of newly established ELISAs for anti-TIF1γ and anti-Mi-2β Abs, which can serve as easier detection systems for routine testing.
Authors: Alexander G S Oldroyd; Andrew B Allard; Jeffrey P Callen; Hector Chinoy; Lorinda Chung; David Fiorentino; Michael D George; Patrick Gordon; Kate Kolstad; Drew J B Kurtzman; Pedro M Machado; Neil J McHugh; Anna Postolova; Albert Selva-O'Callaghan; Jens Schmidt; Sarah Tansley; Ruth Ann Vleugels; Victoria P Werth; Rohit Aggarwal Journal: Rheumatology (Oxford) Date: 2021-06-18 Impact factor: 7.580