AUTHOR=Wang Kaiwen , Zhao Jiangfeng , Wu Wanlong , Xu Wenwen , Sun Shuhui , Chen Zhiwei , Fu Yakai , Guo Li , Du Hui , Ye Shuang 

TITLE=RNA-Containing Immune Complexes Formed by Anti-Melanoma Differentiation Associated Gene 5 Autoantibody Are Potent Inducers of IFN-α

JOURNAL=Frontiers in Immunology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.743704

DOI=10.3389/fimmu.2021.743704

ISSN=1664-3224

ABSTRACT=Objective: Anti-melanoma differentiation associated gene 5 (MDA5) autoantibody is a distinctive serology hallmark of dermatomyositis (DM). As an autoantigen, MDA5 is a cytoplasmic RNA recognition receptor; the aim of this study is to address the question that whether the RNA-containing immune complex (IC) formed by MDA5 and anti-MDA5 could activate type I IFN response.
Method: Patients with anti-MDA5+ dermatomyositis (n=217), anti-MDA5- dermatomyositis (n=68), anti-synthase syndrome (ASyS, n=57), systemic lupus erythematosus (SLE, n=245), rheumatoid arthritis (RA, n=89), systemic sclerosis (SSc, n=30) and healthy donors (HD, n=94) were enrolled in our studies. Anti-MDA5 antibody was detected by line-blotting, enzyme-linked immunosorbent assay (ELISA), immunoprecipitation and Western blotting. Cytokine profiling was determined by multiplex flow cytometry and IFN-ɑ was further measured by ELISA. Type I IFN-inducible genes were detected by qPCR. The RNA-IC binding was analyzed by RNA immunoprecipitation. Plasmacytoid dendritic cells (pDCs) derived from healthy donors were cultivated and stimulated with MDA5 ICs with or without RNase and Toll-like receptor 7 (TLR-7) agonist. The interaction between MDA5 ICs and TLR7 was evaluated by immunoprecipitation and confocal microscopy.
Results: The presence of anti-MDA5 antibody in DM patients, along with 14.3% of SLE patients who had lower titer yet positive anti-MDA5 antibody, were related to high level of peripheral IFN-ɑ. ICs formed by MDA5 and anti-MDA5 were potent inducers of IFN-ɑ via TLR-7 in a RNA-dependent manner in vitro. 
Conclusion: Our data provided evidence of the mechanistic relevance between anti-MDA5 antibody and type I IFN pathway.