RESUMO
OBJECTIVES: Clinical observations in patients with dermatomyositis (DM) and autoantibodies against the melanoma differentiation-associated protein 5 (MDA5) suggest that the autoantibodies contribute to the pathogenesis of MDA5(+) DM. To gain insight into the role of the anti-MDA5 autoantibodies, we aimed to identify their binding sites on the different domains of the MDA5 protein. METHODS: We developed an in-house ELISA to assess the reactivity against the MDA5 domains (conformational epitopes) in plasma (n = 8) and serum (n = 24) samples from MDA5(+) patients with varying clinical manifestations and disease outcomes. The reactivities were also assessed using Western Blot (linearized epitopes). An ELISA-based depletion assay was developed to assess cross-reactivity among the different MDA5 domains. RESULTS: All eight plasma samples consistently showed reactivity towards conformational and linearized epitopes on the helicase domains of the MDA5 protein. The ELISA-based depletion assay suggests that anti-MDA5 autoantibodies specifically target each of the three helicase domains. Twenty-two of the 24 serum samples showed reactivity in the in-house ELISA and all 22 displayed reactivity towards the helicase domains of the MDA5 protein. CONCLUSIONS: Our data revealed that the main immunogenic targets of anti-MDA5 autoantibodies from MDA5(+) patients are the helicase domains. Considering that the helicase domains are responsible for the enzymatic activity and subsequent triggering of an inflammatory response, our findings suggest that binding of anti-MDA5 autoantibodies could alter the canonical activity of the MDA5 protein and potentially affect the downstream induction of a pro-inflammatory cascade.
RESUMO
AIMS: To investigate the association between two RIG-I-like receptor gene polymorphisms and hepatitis C virus (HCV) infection in Chinese Han population. METHODS: The current study genotyped two selected SNPs (IFIH1 rs3747517 and DDX58 rs9695310) using TaqMan allelic discrimination assay to assess their association with the susceptibility and clinical outcome of HCV infection among 3065 participants (1545 non-HCV infection individuals, 568 spontaneous HCV clearance cases, and 952 persistent infection patients). RESULTS: IFIH1 rs3747517 (dominant model: Adjusted odds ratio [OR] = 1.34, 95% confidence interval [CI] = 1.07-1.68; P = 0.009) and DDX58 rs9695310 (dominant model: Adjusted OR = 1.43, 95% CI = 1.15-1.78; P = 0.001) were associated with chronic hepatitis C (CHC). And the risk of CHC increased when people were carrying more unfavorable rs3747517-GA/AA and rs9695310-GC/CC genotypes from zero to two with the chronic rates of 56.72%, 59.38%, and 69.01%, respectively (Ptrend < 0.001). CONCLUSION: Genetic variations at IFIH1 rs3747517 and DDX58 rs9695310 were independent predictors of chronic hepatitis C in Chinese Han population.