| Hepatitis C virus (HCV) is an enveloped, positive-sense RNA virus, which belongs to the family of Flaviviridae. HCV was the most important etiologic factor for chronic liver disease, such as chronic hepatitis and cirrhosis, and closely related to the occurrence of Hepatocellular carcinoma (HCC). The current therapy for HCV infection is Peg IFN-αin combination with ribavirin. Although the sustained viral response rate for HCV genotype 2 and 3 is more than 75%, it is no more than 50% for HCV genotype 1, the most widespread type in the world. IFN-αcould induces a special condition,termed the antiviral state,in which the cells are especially resistant to infection by viral pathogens and inhibition the replication of virus. However,a large proportion of patients do not respond to IFN-α. Current concepts regarding that HCV may interfere with the key signaling pathway to decrease the expression of some IFN-αinduced antivirus proteins,which is advantageous for the establishment infection and refractory to IFN-α. Therefore it is significant to reveal these problems through understanding the specific mechanisms that HCV antagonize the IFN-α. The aim of our study is discussion of possible mechanisms in HCV antagonize the IFN-α, through researching the influence of IFN-αon replication and expression of HCV and HCV affect the transcription of MxA gene in host cell in vitro.First, the role of IFN-αin the replication and expression of HCV was investigated. The expression of HCV protein in infection of Huh7 cells was detected using immunofluorescent method, after 6h exposure of cell culture produced HCV (HCVcc) , all the cells was treated with IFN–αof indicated dose for 12h and then culture for 72h. It shows the infection of HCVcc in Huh7 is down-regulate by the up-regulate the dose of IFN-α, and the infection of virus almost disappeared with a minimum inhibition concentration at 1000 IU/ml IFN-α. Then increase the concentration of IFN-α, the number of positive cells is as the same as the condition of 1000 IU/ml IFN-α. It indicated that the 1000 IU/ml is the critical value of IFN-αantivirus. Because NS5A is known to be critical for HCV RNA replication, we detect the expression of NS5A in infected Huh7 cells treated with different dose IFN–αby western blotting. The results show that the expression of NS5A protein was decreased following IFN-αtreatment. The protein expression of NS5A in Huh7 cells was dose dependent, because increasing dose of IFN-αled to decreasing expression of NS5A. These results agree well with before and affirmed that IFN-αdown- regulate the infection of HCV and the expression of NS5A in vitro. The conclusion showed that, IFN-αexhibits antivirus action probably because the inhibition the expression of NS5A protein.How IFN-αeffect the most important antivirus protein MxA that induced by IFN-αis unclear until now. Huh7 cells were treated with 1000 IU/ml IFN-αfor 0-24h. Quantitative real-time PCR was performed to detect the relative levels of MxA mRNA and GAPDH mRNA. MxA gene transcription was increased with the processing time of IFN-αincrease, and achieve maximum by 12 h following IFN-αtreatment. Also, the transcription of MxA in Huh7 cells was dose dependent, because increasing dose of IFN-αled to increasing transcription of MxA gene, and with a maximal response occurring at 500 IU/ml IFN-α. Third, the effect of HCVcc on the transcription of MxA gene was examined. Compare with IFN-αtreat cells, cells treat with both IFN-αand HCVcc, the transcription of MxA decrease obviously. It suggests that the transcription of MxA may inhibit by HCVcc. The Huh7 cells infected with HCVcc for different dose was detected in different time. The transcription of MxA in infected Huh7 was detected at a high level to the naive Huh7. It shows that HCV can induce the transcription of MxA, and different dose and different viral persistence time of HCV result to different transcription level of MxA.Base on the above research, these confirmed the role of IFN-αin the inhibition of HCV in cells. The low infection of HCV may due to the inhibition of IFN-αin expression the protein of virus. IFN-αcould clean virus completely in a high concentration. But long-term response of chronic hepatitis C for IFN-αtreatment is low in Clinical Practice, possibly because the low concentration of IFN-αin patients. MxA is the most important antivirus protein that induced by IFN-α. But MxA also can be induced by HCV in our in vivo study. Because the infection of HCV induce the production of IFN-α, and then activety the transcription of MxA. But in cells treat with both IFN-αand HCVcc, the transcription of MxA decrease obviously. The results provide evidence that HCV could inhibit IFN-αsignaling through inhibiting the the activity of MxA by IFN-α. Further works are needed to determine how HCV block the activity of MxA by IFN-αin order to provide theoretical basis for optimizing therapeutic plans.
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