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The modulation of hepatitis C virus 1a replication by PKR is dependent on NF-kB mediated interferon beta response in Huh7.5.1 cells.

ABSTRACT: Protein kinase R (PKR), a sensor of double-stranded RNA, plays an important role in the host response to viral infection. Hepatitis C genotype 2a virus (HCV2a) has been shown to induce PKR activation to suppress the translation of antiviral interferon stimulated genes (ISGs), suggesting that PKR inhibitor can be beneficial for treating chronically HCV-infected patients in conjunction with interferon alpha and ribavirin. However, in this study, we found that PKR inhibition using siRNA PKR, shRNA PKR or PKR inhibitor enhanced HCV 1a replication and rendered Huh7.5.1 cells more susceptible to HCV1a infection. Additionally, PKR silencing suppressed NF-kB activation and NF-kB mediated STAT1 phosphorylation in Huh7.5.1 cells and HCV1a persistently infected Huh7.5.1 cells (2HDD4). These effects were accompanied by a reduction of interferon beta response and thereby enhanced HCV1a replication in Huh7.5.1 cells. We conclude that host cells can employ PKR activation to restrict HCV1a replication through regulation of NF-kB expression.

SUBMITTER: Zhang L

PROVIDER: S-EPMC3594529 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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The modulation of hepatitis C virus 1a replication by PKR is dependent on NF-kB mediated interferon beta response in Huh7.5.1 cells.

Zhang Lumin L Alter Harvey J HJ Wang Haiping H Jia Shuaizheng S Wang Ena E Marincola Francesco M FM Shih James W-K JW Wang Richard Y RY

Virology 20130209 1

Protein kinase R (PKR), a sensor of double-stranded RNA, plays an important role in the host response to viral infection. Hepatitis C genotype 2a virus (HCV2a) has been shown to induce PKR activation to suppress the translation of antiviral interferon stimulated genes (ISGs), suggesting that PKR inhibitor can be beneficial for treating chronically HCV-infected patients in conjunction with interferon alpha and ribavirin. However, in this study, we found that PKR inhibition using siRNA PKR, shRNA ...[more]

PMID: 23399035

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Project description:Hepatitis C virus is a poor inducer of interferon (IFN), although its structured viral RNA can bind the RNA helicase RIG-I, and activate the IFN-induction pathway. Low IFN induction has been attributed to HCV NS3/4A protease-mediated cleavage of the mitochondria-adapter MAVS. Here, we have investigated the early events of IFN induction upon HCV infection, using the cell-cultured HCV JFH1 strain and the new HCV-permissive hepatoma-derived Huh7.25.CD81 cell subclone. These cells depend on ectopic expression of the RIG-I ubiquitinating enzyme TRIM25 to induce IFN through the RIG-I/MAVS pathway. We observed induction of IFN during the first 12 hrs of HCV infection, after which a decline occurred which was more abrupt at the protein than at the RNA level, revealing a novel HCV-mediated control of IFN induction at the level of translation. The cellular protein kinase PKR is an important regulator of translation, through the phosphorylation of its substrate the eIF2alpha initiation factor. A comparison of the expression of luciferase placed under the control of an eIF2alpha-dependent (IRES(EMCV)) or independent (IRES(HCV)) RNA showed a specific HCV-mediated inhibition of eIF2alpha-dependent translation. We demonstrated that HCV infection triggers the phosphorylation of both PKR and eIF2alpha at 12 and 15 hrs post-infection. PKR silencing, as well as treatment with PKR pharmacological inhibitors, restored IFN induction in JFH1-infected cells, at least until 18 hrs post-infection, at which time a decrease in IFN expression could be attributed to NS3/4A-mediated MAVS cleavage. Importantly, both PKR silencing and PKR inhibitors led to inhibition of HCV yields in cells that express functional RIG-I/MAVS. In conclusion, here we provide the first evidence that HCV uses PKR to restrain its ability to induce IFN through the RIG-I/MAVS pathway. This opens up new possibilities to assay PKR chemical inhibitors for their potential to boost innate immunity in HCV infection.

Project description:BackgroundPharmacological therapies of proven efficacy in coronavirus disease 2019 (COVID-19) are still lacking. We have identified IFNβ-1a as the most promising drug to be repurposed for COVID-19. The rationale relies on the evidence of IFNβ anti-viral activity in vitro against SARS-CoV-2 and animal models resembling SARS-CoV-2 infection and on a recent clinical trial where IFNβ was indicated as the key component of a successful therapeutic combination.MethodsThis is a randomized, controlled, open-label, monocentric, phase II trial (INTERCOP trial). One hundred twenty-six patients with positive swab detection of SARS-CoV-2, radiological signs of pneumonia, and mild-to-moderate disease will be randomized 2:1 to IFNβ-1a in addition to standard of care vs standard of care alone. No other anti-viral drugs will be used as part of the regimens, both in the control and the intervention arms. IFNβ-1a will be administered subcutaneously at the dose of 44 mcg (equivalent to 12 million international units) three times per week, at least 48 h apart, for a total of 2 weeks. The primary outcome is the time to negative conversion of SARS-CoV-2 nasopharyngeal swabs. Secondary outcomes include improvement or worsening in a clinical severity score measured on a 7-point ordinal scale (including transfer to intensive care unit and death), oxygen- and ventilator-free days, mortality, changes in pulmonary computed tomography severity score, hospital stay duration, reduction of viral load measured on nasopharyngeal swabs, number of serious adverse events, and changes in biochemical markers of organ dysfunction. Exploratory outcomes include blood cell counts, cytokine and inflammatory profile, peripheral mRNA expression profiles of interferon-stimulated genes, and antibodies to SARS-CoV-2 and to IFNβ-1a. INTERCOP is the first study to specifically investigate the clinical benefits of IFNβ-1a in COVID-19 patients.DiscussionPotential implications of this trial are multifaceted: should the primary outcome be fulfilled and the treatment be safe, one may envisage that IFNβ-1a be used to reduce the infectivity of patients with mild-to moderate disease. In case IFNβ-1a reduced the duration of hospital stay and/or ameliorated the clinical status, it may become a cornerstone of COVID-19 treatment.Trial registrationEudraCT 2020-002458-25. Registered on May 11, 2020 ClinicalTrials.gov Identifier: NCT04449380.

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The modulation of hepatitis C virus 1a replication by PKR is dependent on NF-kB mediated interferon beta response in Huh7.5.1 cells.

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The modulation of hepatitis C virus 1a replication by PKR is dependent on NF-kB mediated interferon beta response in Huh7.5.1 cells.

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