An infectious and selectable full-length replicon system with hepatitis C virus JFH-1 strain

Aim: The hepatitis C virus (HCV) strain JFH‐1 was cloned from a patient with fulminant hepatitis. A JFH‐1 subgenomic replicon and full‐length JFH‐1 RNA efficiently replicate in cultured cells. In this study, an infectious, selectable HCV replicon containing full‐length JFH‐1 cDNA was constructed. Methods: The full‐genome replicon was constructed using the neomycin‐resistant gene, EMCV IRES and wild‐type JFH‐1 cDNA. Huh7 cells were transfected with RNA synthesized in vitro, and then cultured with G418. Independent colonies were cloned to establish cell lines that replicate the full‐length HCV replicon. Results: HCV RNA replication was detected in each isolated cell line. HCV proteins and HCV RNA were secreted into culture medium, and exhibited identical density profiles. Interestingly, culture supernatants of the replicon cells were infectious for naïve Huh7 cells. Long‐term culture did not affect replication of replicon RNA in the replicon cells, but it reduced core protein secretion and infectivity of culture supernatant. Culture supernatant obtained after serial passage of replicon virus was infectious for Huh7 cells. Conclusions: Selectable infection was established using HCV replicon containing full‐length genotype 2a JFH‐1 cDNA. This system might be useful for HCV research.     

Inhibition of hepatitis C virus replication by single-stranded RNA structural mimics

AIM: To examine the effect of hepatitis C virus (HCV) structural mimics of regulatory regions of the genome on HCV replication.METHODS: HCV RNA structural mimics were constructed and tested in a HCV genotype 1b aBB7 replicon,and a Japanese fulminant hepatitis-1 (JFH-1) HCV genotype 2a infection model.All sequences were computer-predicted to adopt stem-loop structures identical to the corresponding elements in full-length viral RNA.Huh7.5 cells bearing the BB7 replicon or infected with JFH-1 virus were trans...     

Suppression of hepatitis C virus by the flavonoid quercetin is mediated by inhibition of NS3 protease activity

Phytochemicals exert antiviral activity and may play a potential therapeutic role in hepatitis C virus (HCV) infection. In this work, we aimed to isolate NS3 inhibitors from traditional Indian medicinal plants that were found, in our earlier study, to inhibit HCV NS3 protease activity and to evaluate their potential to inhibit HCV replication. A potent inhibitory effect of NS3 catalytic activity was obtained with Embelia ribes plant extracts. Quercetin, a ubiquitous plant flavonoid, was identified as the active substance in the fractioned extract. It was found to inhibit NS3 activity in a specific dose-dependent manner in an in vitro catalysis assay. Quercetin inhibited HCV RNA replication as analysed in the subgenomic HCV RNA replicon system. It also inhibited HCV infectious virus production in the HCV infectious cell culture system (HCVcc), as analysed by the focus-forming unit reduction assay and HCV RNA real-time PCR. The inhibitory effect of quercetin was also obtained when using a model system in which NS3 engineered substrates were introduced in NS3-expressing cells, providing evidence that inhibition in vivo could be directed to the NS3 and do not involve other HCV proteins. Our work demonstrates that quercetin has a direct inhibitory effect on the HCV NS3 protease. These results point to the potential of quercetin as a natural nontoxic anti-HCV agent reducing viral production by inhibiting both NS3 and heat shock proteins essential for HCV replication.     

Assembly and release of infectious hepatitis C virus involving unusual organization of the secretory pathway

AIM: To determine if calnexin(CANX), RAB1 and alphatubulin were involved in the production of hepatitis C virus(HCV) particles by baby hamster kidney-West Nile virus(BHK-WNV) cells. METHODS: Using a si RNA-based approach complemented with immuno-fluorescence confocal microscope and Western blot studies, we examined the roles of CANX, RAB1 and alpha-tubulin in the production of HCV particles by permissive BHK-WNV cells expressing HCV structural proteins or the full-length genome of HCV genotype 1a. Immuno-fluorescence studies in producer cells were performed with monoclonal antibodies against HCV structural proteins, as well as immunoglobulin from the serum of a patient recently cured from an HCV infection of same genotype. The cellular compartment stained by the serum immunoglobulin was also observedin thin section transmission electron microscopy. These findings were compared with the JFH-1 strain/Huh-7.5 cell model.RESULTS: We found that CANX was necessary for the production of HCV particles by BHK-WNV cells. This process involved the recruitment of a subset of HCV proteins, detected by immunoglobulin of an HCV-cured patient, in a compartment of rearranged membranes bypassing the endoplasmic reticulum-Golgi intermediary compartment and surrounded by mitochondria. It also involved the maturation of N-linked glycans on HCV envelope proteins, which was required for assembly and/or secretion of HCV particles. The formation of this specialized compartment required RAB1; upon expression of HCV structural genes, this compartment developed large vesicles with viral particles. RAB1 and alpha-tubulin were required for the release of HCV particles. These cellular factors were also involved in the production of HCVcc in the JFH-1 strain/Huh-7.5 cell system, which involves HCV RNA replication. The secretion of HCV particles by BHK-WNV cells presents similarities with a pathway involving caspase-1; a caspase-1 inhibitor was found to suppress the production of HCV particles from a full-length genome.CONCLUSION: Prior activity of the WNV subgenomic replicon in BHK-21 cells promoted re-wiring of host factors for the assembly and release of infectious HCV in a caspase-1-dependent mechanism.     

干扰素γ对丙型肝炎病毒复制子的抑制作用

目的研究干扰素（IFN）γ直接抑制丙型肝炎病毒（HCV）复制子的作用及其与IFN α联合用药的疗效，并对可能介导IFN γ抗HCV作用的干扰素刺激基因（ISG）的表达水平进行探讨。方法建立HCV复制子细胞模型，用IFN γ或IFN γ联合IFN α处理HCV复制子细胞，通过半定量逆转录聚合酶链反应（RT-PCR）及实时定量PCR检测细胞中HCV RNA水平；western blot检测细胞中HCV非结构蛋白5A（NS5A）。结果IFN γ对HCV RNA的复制及NS5A的表达有明显抑制作用，10U／ml IFN γ可使HCV RNA较对照组减少36％，25U／ml减少80％；IFN γ对HCV RNA及NS5A蛋白的抑制作用与其剂量及作用时间呈正相关。用IFN γ预处理的细胞对IFN α抗HCV的作用更敏感，且细胞内干扰素调节因子-1（IRF-1）、干扰素刺激基因因子3 γ（ISGF3 γ）和2’5’-寡腺苷酸合成酶（2’5’-OAS）呈明显的诱导性表达。结论IFN γ能有效抑制HCV RNA的复制，并与IFN α有协同抗HCV的作用。IRF-1、ISGF3 γ和2’5’-OAS可能参与介导IFN γ抗HCV的作用。     

Evaluation of a cyclophilin inhibitor in hepatitis C virus-infected chimeric mice in vivo

Cyclosporin A (CsA) inhibits replication of the HCV subgenomic replicon, and this effect is believed to not be mediated by its immunosuppressive action. We found that DEBIO-025, a novel non-immunosuppressive cyclophilin inhibitor derived from CsA, inhibited HCV replication in vitro more potently than CsA. We also examined the inhibitory effect of DEBIO-025 on naive HCV genotypes 1a or 1b in vivo using chimeric mice with human hepatocytes. These mice were treated for 14 days with DEBIO-025, pegylated-interferon alpha-2a (Peg-IFN), a combination of either drugs, or CsA in combination with Peg-IFN. In mice treated with Peg-IFN, serum HCV RNA levels decreased approximately 10-fold whereas DEBIO-025 treatment alone did not induce any significant change. In mice treated with both DEBIO-025 and Peg-IFN, HCV RNA levels decreased more than 100-fold. All mice treated with Peg-IFN combined with CsA died within 4 days. The combination treatment of DEBIO-025 and Peg-IFN reduced HCV RNA levels and core protein expression in liver, indicating that the HCV RNA levels reduction in serum was attributable to intrahepatic inhibition of HCV replication. CONCLUSION: We demonstrated that DEBIO-025 was better tolerated than CsA, and that its anti-HCV effect appeared to be synergistic in combination with Peg-IFN in vivo.     

Effect of hepatitis C virus core shadow protein expressed in human hepatoma cell line on human gene expression profiles

BACKGROUND AND AIMS: The hepatitis C virus (HCV) C region has been reported to have overlapping genes or regions, and may encode a core shadow protein that has a role in HCV self-replication, pathogenesis and carcinogenesis. The aim of this study was to identify the effect of HCV core shadow protein expressed in a human hepatoma (Huh-7) cell line on human gene expression profiles. METHODS: Recombinants for expression of HCV genotype 1b core shadow protein and genotype 1b core protein were constructed, and an Huh-7 cell line was established that could express the shadow protein and the core protein constitutively. Affymetrix human gene chip, HG-U133 A and B microarray analysis and semiquantitative RT-PCR were employed to identify the expression profiles of two kinds of core proteins in the Huh-7 cell line. RESULTS: The microarray analysis showed that the core shadow protein caused expression of more genes to be up/down-regulation than the core protein, including signal transduction, protease activity, molecular transport and, particularly, immune responses genes. Surprisingly, the core shadow protein could increase/decrease expression of apoptosis and anti-apoptosis genes simultaneously. The expression profiles of three up-regulated genes were confirmed by semiquantitative RT-PCR, with results similar to the microarray analysis. CONCLUSIONS: Hepatitis C virus core shadow protein may play an important role in inhibiting or stimulating host cells apoptosis processing and carcinogenesis, which is useful for the understanding of HCV core shadow protein biological functions in vivo and in vitro.     

Reciprocal effects of micro-RNA-122 on expression of heme oxygenase-1 and hepatitis C virus genes in human hepatocytes

BACKGROUND & AIMS: Heme oxygenase-1 (HO-1) is an antioxidant defense and key cytoprotective enzyme, which is repressed by Bach1. Micro-RNA-122 (miR-122) is specifically expressed and highly abundant in human liver and required for replication of hepatitis C virus (HCV) RNA. This study was to assess whether a specific miR-122 antagomir down-regulates HCV protein replication and up-regulates HO-1. METHODS: We transfected antagomir of miR-122, 2'-O-methyl-mimic miR-122, or nonspecific control antagomir, into wild-type (WT) Huh-7 cells or Huh-7 stably replicating HCV subgenomic protein core through nonstructural protein 3 of HCV (NS3) (CNS3 replicon cells) or NS3-5B (9-13 replicon cells). RESULTS: Antagomir of miR-122 reduced the abundance of HCV RNA by 64% in CNS3 and by 84% in 9-13 cells. Transfection with 2'-O-methlyl-mimic miR-122 increased HCV levels up to 2.5-fold. Antagomir of miR-122 also decreased Bach1 and increased HO-1 mRNA levels in CNS3, 9-13, and WT Huh-7 cells. Increasing HO-1 by silencing Bach1 with 50 nmol/L Bach1-short interfering RNA or by treatment with 5 mumol/L cobalt protoporphyrin or heme (known inducers of HO-1) decreased HCV RNA and protein by 50% in HCV replicon cells. CONCLUSIONS: Down-regulation of HCV replication using an antagomir targeted to miR-122 is effective, specific, and selective. Increasing HO-1, by silencing the Bach1 gene or by treatment with cobalt protoporphyrin or heme, decreases HCV replication. Thus, miR-122 plays an important role in the regulation of HCV replication and HO-1/Bach1 expression in hepatocytes. Down-regulation of miR-122 and up-regulation of HO-1 may be new strategies for anti-HCV intervention and cytoprotection.     

Desperately seeking hepatitis C virus

Spanish investigators described recently the so-called occult hepatitis C virus （HCV） infection, emphasizing the detection of genomic and antigenomic HCV RNA strands in liver and peripheral blood mononuclear cells. Therefore, the persistence of viral replication in occult HCV infection should be considered as a putative source of infection among family members and patients undergoing invasive procedures, transfusion or transplantation. Additionally, the most worrisome finding is that an occult HCV infection may persist in patients with sustained virological response.     

Post-translational modifications of hepatitis C viral proteins and their biological significance

Replication of hepatitis C virus(HCV)depends on the interaction of viral proteins with various host cellular proteins and signalling pathways.Similar to cellular proteins,post-translational modifications(PTMs)of HCV proteins are essential for proper protein function and regulation,thus,directly affecting viral life cycle and the generation of infectious virus particles.Cleavage of the HCV polyprotein by cellular and viral proteases into more than 10 proteins represents an early protein modification step after translation of the HCV positivestranded RNA genome.The key modifications include the regulated intramembranous proteolytic cleavage of core protein,disulfide bond formation of core,glycosylation of HCV envelope proteins E1 and E2,methylation of nonstructural protein 3(NS3),biotinylation of NS4A,ubiquitination of NS5B and phosphorylation of core and NS5B.Other modifications like ubiquitination of core and palmitoylation of core and NS4B proteins have been reported as well.For some modifications such as phosphorylation of NS3 and NS5A and acetylation of NS3,we have limited understanding of their effects on HCV replication and pathogenesis while the impact of other modifications is far from clear.In this review,we summarize the available information on PTMs of HCV proteins and discuss their relevance to HCV replication and pathogenesis.     

Chaperones in hepatitis C virus infection

The hepatitis C virus(HCV) infects approximately 3% of the world population or more than 185 million people worldwide. Each year, an estimated 350000-500000 deaths occur worldwide due to HCV-associated diseases including cirrhosis and hepatocellular carcinoma. HCV is the most common indication for liver transplantation in patients with cirrhosis worldwide. HCV is an enveloped RNA virus classified in the genus Hepacivirus in the Flaviviridae family. The HCV viral life cycle in a cell can be divided into six phases:(1) binding and internalization;(2) cytoplasmic release and uncoating;(3) viral polyprotein translation and processing;(4) RNA genome replication;(5) encapsidation(packaging) and assembly; and(6) virus morphogenesis(maturation) and secretion. Many host factors are involved in the HCV life cycle. Chaperones are an important group of host cytoprotective molecules that coordinate numerous cellular processes including protein folding, multimeric protein assembly, protein trafficking, and protein degradation. All phases of the viral life cycle require chaperone activity and the interaction of viral proteins with chaperones. This review will present our current knowledge and understanding of the role of chaperones in the HCV life cycle. Analysis of chaperones in HCV infection will provide further insights into viral/host interactions and potential therapeutic targets for both HCV and other viruses.     

输血后丙型肝炎病毒感染的血清病毒定量研究

目的 研究血清丙型肝炎病毒（ＨＣＶ）含量与ＨＣＶ致病的关系及ＨＣＶ含量与抗－ＨＣＶ和丙氨酸转氨酶（ＡＬＴ）的相关性。方法 以逆转录－聚合酶链反应（ＲＴ－ＰＣＲ）法对ＨＣＶ感染的受血及相关供血系列血清进行ＨＣＶ ＲＮＡ定量分析,同时检测ＡＬＴ与抗－ＨＣＶ。结果 致输血后ＨＣＶ感染的供血中,ＨＣＶ ＲＮＡ平均含量为１０＾８．６拷贝／Ｌ,抗－ＨＣＶ及ＡＬＴ的异常检出率随ＨＣＶ ＲＮＡ滴度升高而增加。结论     

热休克蛋白90抑制剂17-AAG对乙型肝炎病毒复制的抑制作用

目的探讨热休克蛋白90(HSP90)是否参与肝细胞转化生长因子(TGF)β信号通路的活化,以及HSP90对乙型肝炎病毒(HBV)复制的影响。方法 HSP90抑制剂17-AAG作用HepG2细胞,提取细胞总RNA,实时定量RT-PCR检测TGFβ下游信号分子PAI-1的表达。HepG2细胞用17-AAG预处理2 h,同时用TGFβ或TβR抑制剂SB431542作用后,将HBV复制型质粒HBV1.3转染细胞,第4 d提取HBV核心颗粒,Southern Blot检测HBV复制中间体,ELISA检测上清HBsAg的表达。结果 17-AAG能够下调HepG2细胞PAI-1的表达,HepG2细胞内HBV复制中间体表达水平明显降低,HBsAg的表达亦受到抑制,但上调或阻断TGFβ信号通路对HBV复制影响不明显。结论 HSP90参与肝细胞内TGFβ信号通路的活化,其抑制剂17-AAG能够抑制HBV的复制与蛋白表达,但该抑制作用与TGFβ信号通路活化无关。     

Anti‐ulcer agent teprenone inhibits hepatitis C virus replication: potential treatment for hepatitis C

Background: Previously we reported that 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase inhibitors, statins, inhibited hepatitis C virus (HCV) RNA replication. Furthermore, recent reports revealed that the statins are associated with a reduced risk of hepatocellular carcinoma and lower portal pressure in patients with cirrhosis. The statins exhibited anti‐HCV activity by inhibiting geranylgeranylation of host proteins essential for HCV RNA replication. Geranylgeranyl pyrophosphate (GGPP) is a substrate for geranylgeranyltransferase. Therefore, we examined the potential of geranyl compounds with chemical structures similar to those of GGPP to inhibit HCV RNA replication. Methods: We tested geranyl compounds [geranylgeraniol, geranylgeranoic acid, vitamin K₂ and teprenone (Selbex)] for their effects on HCV RNA replication using genome‐length HCV RNA‐replicating cells (the OR6 assay system) and a JFH‐1 infection cell culture system. Teprenone is the major component of the anti‐ulcer agent, Selbex. We also examined the anti‐HCV activities of the geranyl compounds in combination with interferon (IFN)‐α or statins. Results: Among the geranyl compounds tested, only teprenone exhibited anti‐HCV activity at a clinically achievable concentration. However, other anti‐ulcer agents tested had no inhibitory effect on HCV RNA replication. The combination of teprenone and IFN‐α exhibited a strong inhibitory effect on HCV RNA replication. Although teprenone alone did not inhibit geranylgeranylation, surprisingly, statins' inhibitory action against geranylgeranylation was enhanced by cotreatment with teprenone. Conclusions: The anti‐ulcer agent teprenone inhibited HCV RNA replication and enhanced statins' inhibitory action against geranylgeranylation. This newly discovered function of teprenone may improve the treatment of HCV‐associated liver diseases as an adjuvant to statins.     

Effect of human immunodeficiency virus infection on hepatitis C virus infection in hemophiliacs

Chronic liver disease due to hepatitis C virus (HCV) infection is a major problem in hemophiliacs. Recent reports suggested that hemophiliacs coinfected with hepatitis C virus and human immunodeficiency virus (HIV) have an increased incidence of liver failure but the mechanism of accelerated liver injury is not clear. We tested plasma from 100 hemophiliacs for anti-HCV by second generation ELISA, anti-HIV by EIA, and HCV RNA and HIV RNA by branched DNA and polymerase chain reaction assays to determine if hemophiliacs coinfected with HCV and HIV have higher HCV RNA levels and more active liver disease. Seventy-nine (79%) patients were anti-HCV positive, of whom 85% were HCV RNA positive. None of the anti-HCV-negative patients had detectable HCV RNA in plasma. Forty-two (42%) patients were anti-HIV positive, of whom 47% had detectable HIV RNA. All the anti-HIV-positive patients were also anti-HCV positive. The prevalence of both anti-HCV and anti-HIV increased significantly with age. There was no difference in HCV RNA levels between anti-HIV-positive and anti-HIV-negative patients (mean: 21±4 vs 18±5 Meq/ml), although HCV RNA levels were significantly higher in anti-HIV-positive patients with CD4 counts<200/mm³ (P=0.008). There was an inverse correlation between HCV RNA levels and CD4 counts but no correlation was found between HCV RNA and serum aminotransferase levels. We found a high prevalence of HCV and HIV coinfection in our hemophiliacs. Hepatitis C virus replication appears to be increased in patients with severe immunodeficiency secondary to progressive HIV infection. However, there was no correlation between HCV RNA and serum ALT level, suggesting that HCV is not directly cytopathic.     

Interaction between hepatic membrane type 1 matrix metalloproteinase and acireductone dioxygenase 1 regulates hepatitis C virus infection

Membrane type 1 matrix metalloproteinase (MT1‐MMP) binds to and regulates the function of tetraspanin‐enriched microdomains. It also physically interacts with claudin‐1 and acireductone dioxygenase 1 (ADI1), both associated with hepatitis C virus (HCV) cell entry. Here, we examined hepatic expression of MT1‐MMP, ADI1 and claudin‐1 as well as their physical interaction in relation to serum or intrahepatic HCV‐RNA levels. A total of 104 liver biopsies obtained from chronic hepatitis C patients and 84 liver tissues obtained from noncancerous parts of surgically removed HCV‐related hepatocellular carcinoma were analysed. Positive cytoplasmic ADI1 in liver biopsies was associated with higher serum HCV‐RNA levels (P = 0.009). Positive MT1‐MMP and ADI1 interaction assessed by co‐immunoprecipitation was associated with lower tissue HCV‐RNA levels (P = 0.009). Hepatic HCV‐RNA levels were positively associated with ADI1 levels in the MT1‐MMP and ADI1 co‐immunoprecipitates (P = 0.030). Overexpression of MT1‐MMP in Huh7.5 cells suppressed cell entry of HCV pseudoparticles as well as HCVcc infection. The suppression effect could be reversed by co‐expression of ADI1 in a dose‐dependent manner. In summary, clinical and cell‐based experiments suggested that physical interaction between MT1‐MMP and ADI1 led to suppression of HCV infection. This inhibitory effect could be reversed by ADI1 overexpression.     

Mutational analysis of the hepatitis C virus E1 glycoprotein in retroviral pseudoparticles and cell-culture-derived H77/JFH1 chimeric infectious virus particles

Summary.  Cell entry by enveloped viruses is mediated by viral glycoproteins, and generally involves a short hydrophobic peptide (fusion peptide) that inserts into the cellular membrane. An internal hydrophobic domain within E1 (aa262–290) of hepatitis C virus (HCV) may function as a fusion peptide. Retrovirus-based HCV-pseudotyped viruses (HCVpp; genotype 1a) containing Ala or Pro substitutions at conserved amino acid positions within this putative fusion peptide were generated. Mutation of conserved residues significantly reduced efficiency of HCVpp entry into Huh-7 cells. The majority of amino acid substitutions appeared to disrupt necessary interactions between E1 and E2. For some mutants, reductions in HCVpp-associated E1 were associated with the incorporation of a high molecular weight, hyperglycosylated E2 that displayed decreased CD81-binding. Other entry-deficient mutants displayed normal E1E2 incorporation into pseudoparticles and normal CD81-binding, and therefore might affect viral fusion. One mutant (S283P) consistently displayed two- to threefold higher infectivity than did wild-type. Three mutations that decreased HCVpp infectivity also reduced levels of HCVcc infectious virus production. However, the S283P mutation had a different effect in the two systems as it did not increase production of infectious HCVcc. This comprehensive mutational analysis of the putative HCV fusion peptide provides insight into the role of E1 in its interaction with E2 and in HCV entry.