Thioredoxin Interacting Protein Is Involved In HCV Inducing Autophagy And Escaping Host’s Innate Immunity

Hepatitis C virus,an important pathogen for human acute and chronic hepatitis,is a single stranded RNA virus belonging to Flaviviridae.About 80% of individuals exposed to HCV develop a chronic infection.Chronic HCV infection often results in liver fibrosis,hepatocellular carcinoma(HCC)and other severe end-stage liver diseases.Once Pegylated interferon combined with ribavirin had been the standard treatment for HCV infection,but its curative effect was impacted by HCV genotypes.The new drugs direct antiviral agents(DAAs)listed in recent years such as Ledipasvir and Sofosbuvir significantly change the treatment status of HCV infection,but they can’t be used widely in short time due to expensive price.In addition,it need to be further observed whether there are drug resistance mutations and side effects.HCV genome is highly variable,which enable HCV easily evading host adaptive immunity and causing chronic infection.HCV also has evolved other complex immune evasion mechanisms,especially those to evade innate immunity and establish persistent infection.Many developed countries paid much attention to HCV vaccine in the past nearly thirty years after HCV molecular cloning.A series of HCV vaccines have completed phase I and II clinical trials,but none completed phase III clinical trial so far.The high variability of HCV makes vaccine development difficult.On the other hand,whether HCV infection is sufficient to induce protective level of immune responses remains controversial.Although anti-HCV drugs have made great progress,but chronic HCV infection and immune escape mechanism deserve to investigate further more.Clarifing these complicated issues can provide important clues not only to control HCV infection,but also to understand persistent infection mechanisms of other human viruses.In fact,HCV has been regarded as a important model for chronic viral infection.Even if great progress has been made in anti-HCV drug research and development,HCV infection and pathogenesis still is hotspot focused by scholars.Our previous studies found that HCV infection significantly up-regulated the expression of TXNIP in Huh7 cells,and is highly dependent on the expression of TXNIP.Based on this study,we explored the mechanisms that involved in HCV inducing TXNIP expression and TXNIP promoting HCV infection.In this study,we carried out the experiments and obtained results as follows: 1)we further observed and confirmed that HCV infection up-regulated TXNIP expression in Huh7 cells and TXNIP played an important role in HCV infection;2)Using RNA interference,we confirmed that autophagy is important to HCV infection in Huh7 cells and found that inhibiting TXNIP expression significantly decreased autophagy induced by serum starvation;3)we did not observed the endoplasmic reticulum stress of Huh 7 cells induced by HCV infection;4)HCV infection could activate the transcription of IFN-beta at a low level in Huh7 cells and exogenous IFN-beta up-regulated expression of TXNIP in a dose dependent manner in Huh7 cells;5)transfection of full-length HCV genome RNA and HCV 3’-UTR in Huh7 cells induced the production of IFN-beta and up-regulation of TXNIP;6)transfection of RIG-I expression plasmid in Huh7.5.1 cells could increaseTXNIP expression and furtherup-regulate TXNIP expression after HCV infection,but this effect was not observed in na?ve Huh7.5.1;7)Redd1 might regulate HCV infection cooperatingwith TXNIP;8)calcium antagonist verapamil could supress HCV infection via inhibiting TXNIP expression.This study established a new model of chronic HCV infection: HCV infection stimulates host cells to produce interferons(no matter how the levels of interferon produced in the cell model,significant up-regulation of interferon expression in liver tissues of human and chimpanzees infected with HCV was observed).Interferons stimulate TXNIP expression and then TXNIP enhance HCV replication through promoting cellular autophagy.Based on this finding,we clarified that verapamil,an inexpensive drug used in clinical treatment for hypertension inhibited HCV infection by supressing the expression of TXNIP and the prospect used in hepatitis C treatment is worth further explored.