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

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

doi:10.3389/fimmu.2021.743704

Kaiwen Wang, Wanlong Wu + Show 8 more

Open Access

https://doi.org/10.3389/fimmu.2021.743704

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Abstract

ObjectiveAnti-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 was to address the question of whether the RNA-containing immune complex (IC) formed by MDA5 and anti-MDA5 could activate type I interferon (IFN) response.MethodPatients with anti-MDA5+ DM (n = 217), anti-MDA5− DM (n = 68), anti-synthase syndrome (ASyS, n = 57), systemic lupus erythematosus (SLE, n = 245), rheumatoid arthritis (RA, n = 89), and 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-α was further measured by ELISA. Type I IFN-inducible genes were detected by quantitative PCR (qPCR). 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.ResultsAccording to our in-house ELISA, the presence of anti-MDA5 antibody in 76.1% of DM patients, along with 14.3% of SLE patients who had a lower titer yet positive anti-MDA5 antibody, was related to the high level of peripheral IFN-α. ICs formed by MDA5 and anti-MDA5 were potent inducers of IFN-α via TLR-7 in an RNA-dependent manner in vitro.ConclusionOur data provided evidence of the mechanistic relevance between the anti-MDA5 antibody and type I IFN pathway.

Highlights

Anti-melanoma differentiation-associated gene 5 (MDA5) antibody is considered a specific serological marker in dermatomyositis (DM), which is typically linked to the amyopathic phenotype and rapidly progressive interstitial lung disease (ILD) [1]
immune complex (IC) formed by MDA5 and anti-MDA5 were potent inducers of IFN-a via Toll-like receptor 7 (TLR-7) in an RNA-dependent manner in vitro
The cutoff value of our in-house enzymelinked immunosorbent assay (ELISA) was set at 35 RU/ml, this study did not include DM-specific antibody-negative DM patients

Summary

Introduction

Anti-melanoma differentiation-associated gene 5 (MDA5) antibody is considered a specific serological marker in dermatomyositis (DM), which is typically linked to the amyopathic phenotype and rapidly progressive interstitial lung disease (ILD) [1]. MDA5, encoded by the IFIH1 gene, is the key sensor of viral double-strand RNA (dsRNA) and belongs to the retinoic acid-induced gene I (RIG-I)-like receptors [3], which are actively involved in the type I interferon (IFN-a and IFN-b) pathway. There is strong genetic evidence for a link between cytoplasmic RNA sensing pathways (RIG-I/MDA5) and SLE [6, 7]. The current knowledge suggested that the anti-MDA5 antibody, as a serological marker, is more likely to be a by-product of an “overloaded” type I IFN pathway in DM [8,9,10,11]. We are asking the question whether the anti-MDA5 antibody could enhance the type I IFN response

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