Infected Huh7 Cells Research Articles

IL-1β secreted by macrophages in response to commensal bacteria acts together with bone morphogenetic protein signals to increase hepcidin expression in hepatocytes (MUC5P.758)

Abstract Elevated expression of the iron regulating hormone hepcidin leads to abnormalities of iron metabolism in inflammatory diseases. The mechanisms involved in inflammation-associated hepcidin upregulation are not well understood. We have shown in mouse IBD models that the commensal microbiota significantly influences hepcidin expression. Here we describe experiments to elucidate how commensal bacteria upregulate hepcidin. Differentiated THP-1 macrophages were infected with the commensal Bifidobacterium infantis. Sterile supernatants of the infected, but not uninfected, THP-1 cells increased hepcidin expression in HuH7 human hepatocytes, whereas direct infection of HuH7 cells failed to induce hepcidin. The infected THP-1 cells secreted IL-1β, neutralization of which significantly inhibited induction of hepcidin expression in the HuH7 cells. Pretreatment of the HuH7 cells with inhibitors of the bone morphogenetic protein (BMP) signaling pathway also prevented the upregulation of hepcidin by the supernatant of B. infantis-infected THP-1 cells. Our findings demonstrate that IL-1β secreted by macrophages in response to commensal bacteria can induce increased expression of hepcidin in hepatocytes. An activator of the BMP signaling pathway is also involved but the identity and source of this molecule are yet to be determined. Furthermore, our results suggest that neutralization of IL-1β may be useful in preventing or treating the dysregulation of iron homeostasis associated with IBD.

Alternative endocytosis pathway for productive entry of hepatitis C virus.

Previous studies have shown that hepatitis C virus (HCV) enters human hepatic cells through interaction with a series of cellular receptors, followed by clathrin-mediated, pH-dependent endocytosis. Here, we investigated the mechanisms of HCV entry into multiple HCV-permissive human hepatocyte-derived cells using trans-complemented HCV particles (HCVtcp). Knockdown of CD81 and claudin-1, or treatment with bafilomycin A1, reduced infection in Huh-7 and Huh7.5.1 cells, suggesting that HCV entered both cell types via receptor-mediated, pH-dependent endocytosis. Interestingly, knockdown of the clathrin heavy chain or dynamin-2 (Dyn2), as well as expression of the dominant-negative form of Dyn2, reduced infection of Huh-7 cells with HCVtcp, whereas infectious entry of HCVtcp into Huh7.5.1 cells was not impaired. Infection of Huh7.5.1 cells with culture-derived HCV (HCVcc) via a clathrin-independent pathway was also observed. Knockdown of caveolin-1, ADP-ribosylation factor 6 (Arf6), flotillin, p21-activated kinase 1 (PAK1) and the PAK1 effector C-terminal binding protein 1 of E1A had no inhibitory effects on HCVtcp infection into Huh7.5.1 cells, thus suggesting that the infectious entry pathway of HCV into Huh7.5.1 cells was not caveolae-mediated, or Arf6- and flotillin-mediated endocytosis and macropinocytosis, but rather may have occurred via an undefined endocytic pathway. Further analysis revealed that HCV entry was clathrin- and dynamin-dependent in ORL8c and HepCD81/miR122 cells, but productive entry of HCV was clathrin- and dynamin-independent in Hep3B/miR122 cells. Collectively, these data indicated that HCV entered different target cells through different entry routes.

Identification of a novel drug lead that inhibits HCV infection and cell-to-cell transmission by targeting the HCV E2 glycoprotein.

Hepatitis C Virus (HCV) infects 200 million individuals worldwide. Although several FDA approved drugs targeting the HCV serine protease and polymerase have shown promising results, there is a need for better drugs that are effective in treating a broader range of HCV genotypes and subtypes without being used in combination with interferon and/or ribavirin. Recently, two crystal structures of the core of the HCV E2 protein (E2c) have been determined, providing structural information that can now be used to target the E2 protein and develop drugs that disrupt the early stages of HCV infection by blocking E2’s interaction with different host factors. Using the E2c structure as a template, we have created a structural model of the E2 protein core (residues 421–645) that contains the three amino acid segments that are not present in either structure. Computational docking of a diverse library of 1,715 small molecules to this model led to the identification of a set of 34 ligands predicted to bind near conserved amino acid residues involved in the HCV E2: CD81 interaction. Surface plasmon resonance detection was used to screen the ligand set for binding to recombinant E2 protein, and the best binders were subsequently tested to identify compounds that inhibit the infection of Huh-7 cells by HCV. One compound, 281816, blocked E2 binding to CD81 and inhibited HCV infection in a genotype-independent manner with IC50’s ranging from 2.2 µM to 4.6 µM. 281816 blocked the early and late steps of cell-free HCV entry and also abrogated the cell-to-cell transmission of HCV. Collectively the results obtained with this new structural model of E2c suggest the development of small molecule inhibitors such as 281816 that target E2 and disrupt its interaction with CD81 may provide a new paradigm for HCV treatment.

Antiviral activity of lanatoside C against dengue virus infection

Dengue infection poses a serious threat globally due to its recent rapid spread and rise in incidence. Currently, there is no approved vaccine or effective antiviral drug for dengue virus infection. In response to the urgent need for the development of an effective antiviral for dengue virus, the US Drug Collection library was screened in this study to identify compounds with anti-dengue activities. Lanatoside C, an FDA approved cardiac glycoside was identified as a candidate anti-dengue compound. Our data revealed that lanatoside C has an IC50 of 0.19μM for dengue virus infection in HuH-7 cells. Dose-dependent reduction in dengue viral RNA and viral proteins synthesis were also observed upon treatment with increasing concentrations of lanatoside C. Time of addition study indicated that lanatoside C inhibits the early processes of the dengue virus replication cycle. Furthermore, lanatoside C can effectively inhibit all four serotypes of dengue virus, flavivirus Kunjin, alphavirus Chikungunya and Sindbis virus as well as the human enterovirus 71. These findings suggest that lanatoside C possesses broad spectrum antiviral activity against several groups of positive-sense RNA viruses.

Modulation of Triglyceride and Cholesterol Ester Synthesis Impairs Assembly of Infectious Hepatitis C Virus

In hepatitis C virus infection, replication of the viral genome and virion assembly are linked to cellular metabolic processes. In particular, lipid droplets, which store principally triacylglycerides (TAGs) and cholesterol esters (CEs), have been implicated in production of infectious virus. Here, we examine the effect on productive infection of triacsin C and YIC-C8-434, which inhibit synthesis of TAGs and CEs by targeting long-chain acyl-CoA synthetase and acyl-CoA:cholesterol acyltransferase, respectively. Our results present high resolution data on the acylglycerol and cholesterol ester species that were affected by the compounds. Moreover, triacsin C, which blocks both triglyceride and cholesterol ester synthesis, cleared most of the lipid droplets in cells. By contrast, YIC-C8-434, which only abrogates production of cholesterol esters, induced an increase in size of droplets. Although both compounds slightly reduced viral RNA synthesis, they significantly impaired assembly of infectious virions in infected cells. In the case of triacsin C, reduced stability of the viral core protein, which forms the virion nucleocapsid and is targeted to the surface of lipid droplets, correlated with lower virion assembly. In addition, the virus particles that were released from cells had reduced specific infectivity. YIC-C8-434 did not alter the association of core with lipid droplets but appeared to decrease production of infectious virus particles, suggesting a block in virion assembly. Thus, the compounds have antiviral properties, indicating that targeting synthesis of lipids stored in lipid droplets might be an option for therapeutic intervention in treating chronic hepatitis C virus infection.

In vivo inhibition of hepatitis C virus infection by anti‐Claudin‐1 monoclonal antibodies (1062.9)

More than 170 million people worldwide are infected with hepatitis C virus (HCV). Despite concerted research efforts, anti‐HCV agents resistant to the high mutability of the HCV RNA genome have not yet been produced. Claudin 1 (CLDN1) is a co‐receptor for HCV entry into hepatocytes and is an attractive potential target for HCV therapy, because such host factors are genetically stable. Here, we investigated the effects of 4 previously generated mouse anti‐CLDN1 antibodies on HCV infection. All 4 clones attenuated the infection of Huh7 cells by HCV (genotype 2a) and HCV pseudoviral particles (HCVpp, genotypes 1b and 2a). Two of 4 clones also prevented HCV (genotype 1b) infection of human‐liver‐chimeric mice. Injection of mouse anti‐CLDN1 antibodies did not adversely affect serum human albumin levels, apparent character, and motility. For future clinical application, we prepared human‐mouse chimeric anti‐CLDN1 antibodies. The chimeric antibodies prevented HCV and HCVpp infection of Huh7 cells as effectively as did the mouse antibodies. Our findings suggest that mouse and mouse‐human chimeric anti‐CLDN1 antibodies prevent HCV infection and may therefore be promising candidate anti‐HCV agents.Grant Funding Source: supported by the Ministry of Health, Labor, and Welfare of Japan

Studies on the role of neutralizing antibodies against envelope genes in resolving HCV pseudo-particles infection

Characterization of antibodies targeting the attachment and entry of the viral particles into host cells is important for studding antibody mediated neutralization. Antibodies against the envelope glycoproteins (EGP) have neutralizing capacity and can prevent HCV infections. System based on HCV pseudo typed-particles (HCVpp) stably expressing EGP can be used for screening of HCV anti envelope neutralizing antibodies in the serum of patients with acute and chronic HCV infections. The aim of the current study was to check HCVpp as a useful tool for the detection of anti-HCV envelope antibodies in the serum of HCV infected patients and to test the binding potential of these antiviral molecules to EGP of HCV 3a. Previously developed HCVpp harboring unmodified glycoproteins from local isolates in 293T cell line were used in this study. HCVpp were pre incubated with different concentrations of anti E1 antibody and different E2 antibodies to check antiviral activity. Further we used serum samples with low/medium (≤800,000 IU/mL), and high (>800,000 IU/mL) viral titer from chronic HCV male and female patients. Infection was done in Huh-7 cells for 1 h at 37 oC. Infectivity was checked through Luciferase assay. Considerable decrease in HCVpp infectivity with anti-envelope antibodies was observed in dose dependent manner. Maximum inhibition was seen when 5 µg/ml of monoclonal anti E1 antibody used. Further increase in concentration exhibited no decrease in infectivity which suggests that other factors are also involved in causing infection. Various well characterized E2-specific monoclonal antibodies (mAbs) have been screened for their capability to reduce infection in Huh-7 cells. Three of the four mAbs specific for the E2 had no effect on the infectivity of HCVpp. Confirmation sensitive antibody H53 showed maximum inhibition of infectivity. HCV ELISA positive samples from both male and female patients were used to neutralize the HCVpp. The neutralizing antibody response was observed in both males and females patients and do not assemble the rapidly evolving HCV envelope glycoproteins. That is why in spite the presence of neutralizing antibodies in the blood they fail to resolve infections. Moreover E1 antibodies insignificantly (>0.05) inhibit HCVpp infectivity while E2 antibodies significantly (<0.05) inhibit HCVpp infection. Based on the results of this study it is concluded that anti-envelope antibodies particularly the anti-E2 could be extremely valuable for characterizing the humoral immune response to HCV and for evaluating the potential for developing passive and active immunization for hepatitis C along with interferon therapy.

HCV Genomic RNA Activates the NLRP3 Inflammasome in Human Myeloid Cells

BackgroundElevated plasma levels of IL-1β and IL-18 from patients with hepatitis C virus (HCV) infection indicate a possible activation of inflammasome by HCV.Methodology/Principal FindingsTo demonstrate whether HCV infection activates the inflammasome, we investigated inflammasome activation from HCV infected hepatic Huh7 cells, or monocytic cells and THP-1 derived macrophages challenged with HCV virions, but no any inflammasome activation was detected in these cells. However, when we transfected HCV genomic RNA into monocytes or macrophages, IL-1β was secreted in a dose-dependent manner. We also detected ASC oligomerization and caspase-1 cleavage in HCV RNA transfected macrophages. Using shRNA-mediated gene silencing or specific inhibitors, we found that HCV RNA-induced IL-1β secretion was dependent on the presence of inflammasome components such as NLRP3, ASC and caspase-1. Furthermore, we also found that RIG-I was dispensable for HCV RNA-induced NLRP3 inflammasome activation, while reactive oxygen species (ROS) production was required.ConclusionsOur results indicate that HCV RNA activates the NLRP3 inflammasome in a ROS-dependent manner, and RIG-I is not required for this process.

Generation of six genotypes of infectious HCV pseudo-particles and detection of neutralizing antibodies in HCV patients

To generate hepatitis C virus pseudo-particles (HCVpp) containing the complete E1-E2 envelope glycoprotein, in order to establish a HCVpp database covering the six major genotypes of HCV (1b, 2a, 3b, 4, 5, and 6) and to develop a simple and effective method for detection of neutralizing antibodies in HCV patients. HCVpp were generated for the six genotypes by co-transfecting 293T cells with a plasmid expressing the respective E1-E2 (p HR, CMVA 8.2 construct) and a MLV-GFP plasmid. Titration of each HCVpp was carried out by p24 ELISA. Infectivity of each HCVpp was assessed by mixing the harvested supernatant of producer cells with sera from HCV patients, adding the mixture to Huh-7 cells, and detecting the subsequent titers of neutralizing antibodies against HCVpp. All six types of HCVpp were able to infect Huh-7 cells in vitro. For healthy HCV carriers, only two genotypes of HCVpp (1b and 2a) produced neutralizing antibody titers more than 1:40. For cured HCV patients, only the 1b genotype produced neutralizing antibody titers more than 1:40. One patient showed titer of 1:200 for genotype 4. A healthy spouse of a chronic hepatitis C patient showed titers more than 1:40 for four genotypes of HCVpp (3a, 4, 5, 6). We generated six different genotypes of HCVpp successfully, established the in vitro neutralizing antibody detection method, and provided an effective model for screening antiviral drugs.

Identification of Novel Compounds Inhibiting Chikungunya Virus-Induced Cell Death by High Throughput Screening of a Kinase Inhibitor Library

Chikungunya virus (CHIKV) is a mosquito-borne arthrogenic alphavirus that causes acute febrile illness in humans accompanied by joint pains and in many cases, persistent arthralgia lasting weeks to years. The re-emergence of CHIKV has resulted in numerous outbreaks in the eastern hemisphere, and threatens to expand in the foreseeable future. Unfortunately, no effective treatment is currently available. The present study reports the use of resazurin in a cell-based high-throughput assay, and an image-based high-content assay to identify and characterize inhibitors of CHIKV-infection in vitro. CHIKV is a highly cytopathic virus that rapidly kills infected cells. Thus, cell viability of HuH-7 cells infected with CHIKV in the presence of compounds was determined by measuring metabolic reduction of resazurin to identify inhibitors of CHIKV-associated cell death. A kinase inhibitor library of 4,000 compounds was screened against CHIKV infection of HuH-7 cells using the resazurin reduction assay, and the cell toxicity was also measured in non-infected cells. Seventy-two compounds showing ≥50% inhibition property against CHIKV at 10 µM were selected as primary hits. Four compounds having a benzofuran core scaffold (CND0335, CND0364, CND0366 and CND0415), one pyrrolopyridine (CND0545) and one thiazol-carboxamide (CND3514) inhibited CHIKV-associated cell death in a dose-dependent manner, with EC50 values between 2.2 µM and 7.1 µM. Based on image analysis, these 6 hit compounds did not inhibit CHIKV replication in the host cell. However, CHIKV-infected cells manifested less prominent apoptotic blebs typical of CHIKV cytopathic effect compared with the control infection. Moreover, treatment with these compounds reduced viral titers in the medium of CHIKV-infected cells by up to 100-fold. In conclusion, this cell-based high-throughput screening assay using resazurin, combined with the image-based high content assay approach identified compounds against CHIKV having a novel antiviral activity - inhibition of virus-induced CPE - likely by targeting kinases involved in apoptosis.

MOUSE MONOCLONAL ANTIBODY TOWARDS E1 SPECIFIC EPITOPE BLOCKS VIRAL ENTRY AND INTRACELLULAR VIRAL REPLICATION IN VITRO

We characterized viral neutralization by a murine monoclonal antibody (mAb315) developed against conserved E1 specific epitope aa 315–323 at pre- and post-binding steps of infection into Huh7 cells. Detection of native virus in infected Huh7 cells by mAb315 were demonstrated by immunostaining. Inhibitions of viral entry by three different concentrations of mAb315 were measured by intracellular amplification of HCV RNA post infection. HCV RNA positive sera from 24 patients were used to infect Huh7 cell line in absence or presence of mouse monoclonal antibody produced in Balb/c mice or culture supernatant of mouse hybrid cells. Monoclonal Ab mAb315 could detect synthetic peptide p315 adsorbed on peripheral human lymphocytes by flow cytometry and showed high immuno reactivity to E1 viral antigen in infected Huh7 cells by immunostaining. Antibody-mediated neutralization assays demonstrated the ability of mAb315 to block HCV binding/entry to target cells at 0.73 mg/mL ascitic fluid or 250 µg/mL culture supernatant of mouse hybrid cells. Sixteen of 24 infected sera could infect Huh7 cells (67%). Binding/entry of HCV was completely blocked by mAb315 in 11/16 cases (69%). These findings suggest that mAb315 can induce HCV neutralization in vitro, which makes it a candidate for developing HCV therapeutic antibodies

A novel helper-dependent adenovirus-based cell culture model for Hepatitis C virus replication and production

BackgroundBy using the hepatitis C virus (HCV) genotype 2a JFH-1 or its chimeric strains, a HCV infection system has been previously developed through several methods– such as in vitro-transcribed JFH1-RNA transfection or stable transfection of the JFH1 cDNA into human hepatoma Huh-7 cell line or its derivatives. However, other reliable methods for delivery of the HCV genome into cells are still worth trying. The helper-dependent adenovirus (HDAd) is devoid of all viral coding sequences and has a package capacity of 37 kb, which is suitably large for the delivery of the HCV genome. Here we report a new method for delivery of the HCV genome into Huh-7 and HepG2 cells by using the HDAd vector.ResultsOur results demonstrated that the infection of Huh-7 cells with the HDAdJFH1 virus led to efficient HCV replication and virion production. We found that the HCV viral RNA levels could reach 107 copies per milliliter (ml) in the culture medium. HDAdJFH1-infected Huh-7 cells could be cultured for 8 passages with the culture medium remaining infectious for naïve Huh-7 cells throughout this period. This infection system proved effective for evaluating the anti-HCV effects of IFN-α in Huh-7 cells. Co-infection of HepG2 cells with the HDAdJFH1 and HDAdmiR-122 virus also resulted in HCV expression and replication.ConclusionThis is the first report of an HDAd-based strategy for HCV replication and production in vitro.

Hepatic damage caused by coxsackievirus B3 is dependent on age-related tissue tropisms associated with the coxsackievirus-adenovirus receptor

Coxsackievirus B (CVB) and enterovirus 71 (EV71) are important causes of severe enteroviral diseases in neonates or young children in Taiwan. CVB can cause fulminant hepatitis, myocarditis or meningoencephalitis. This study was designed to explore the role of coxsackievirus-adenovirus receptor (CAR) in the pathogenesis of CVB3-infected hepatocytes via in vitro and mice studies. CVB3 (CVB3/2630) was isolated from liver tissue of a neonate with fulminant hepatitis. Cell lines A549, HeLa, HEp2 and Huh-7 were maintained in Dulbecco's modified Eagle's medium. Mice progeny 1 or 7 days old were used in the experiments. Viremia was noted in 7-day-old ICR mice 2 h after intraperitoneal injection. The highest viral titers were detected in blood, liver and spleen. Histopathological studies of the liver demonstrated polymorphonuclear cell infiltration, massive hepatic cell necrosis and apoptosis. CAR was expressed more in liver than in other tissues. Expression of CAR decreased with mouse age. Anti-CAR monoclonal antibody prevented infection of Huh-7 cells from CVB3. Furthermore, anti-CAR monoclonal antibody pretreatment can reduce mortality and decrease the level of liver enzymes in CVB3-infected mice. These findings indicate that CAR plays an important role in the initiation of CVB infections and is closely associated with hepatotropism and age-specific susceptibility.

The increase in cholesterol levels at early stages after dengue virus infection correlates with an augment in LDL particle uptake and HMG-CoA reductase activity

Several cellular molecules and components, specifically, cholesterol and lipid rafts have been described as necessary elements for dengue virus entry and signaling in several human cells. Thus, changes in lipid rafts formation and cholesterol levels were evaluated. Here we report that the amount of total cholesterol and lipid rafts formation increase early after infection of Huh-7 cells. This augment correlates with an increase in the amount of low density lipoprotein receptor (LDLr) on the surface of infected cells and also with a lower phosphorylation level of the 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR). None of the changes were observed in Huh 7 cells infected with VSV used as a control. These results suggest that dengue virus infection increases intracellular cholesterol levels at early times post infection by triggering the modulation of LDL particles uptake and the increase in the enzymatic activity of HMG-CoA reductase.

PTEN protein phosphatase activity regulates hepatitis C virus secretion through modulation of cholesterol metabolism

Hepatitis C virus (HCV) infection is dependent on lipid metabolism. Hepatocyte steatosis occurs frequently in HCV infection, but the relationship between steatosis and HCV life cycle is unclear. We showed that HCV induces steatosis via the downregulation of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN). We here investigated how PTEN may affect HCV production. The effect of overexpression or silencing of PTEN on HCV secretion was assessed in genomic-length Jc1 infected HuH7 cells. The role of PTEN protein and lipid phosphatase activities on lipid metabolism and infectious viral particle secretion was investigated using dominant-negative PTEN mutants. The importance of cholesterol metabolism for PTEN-dependent lipid droplet biogenesis and viral particle secretion was examined using statins. PTEN silencing in Jc1 infected HuH7 cells stimulated HCV particle secretion, while PTEN overexpression decreased virus egress. Viral secretion was also increased by overexpression of protein phosphatase-deleted (PTENY138L), but not lipid phosphatase-deleted (PTENG129E), PTEN mutant, thus indicating that the protein phosphatase activity of PTEN controls viral secretion. Similarly, PTENY138L, but not PTENG129E mutant induced the formation of large lipid droplets. PTENY138L mutant did not affect biosynthesis of triglycerides, but promoted the biosynthesis of cholesterol esters. Consistently, statins prevented the increased cholesterol ester production, large lipid droplet formation, and viral secretion in cells expressing the PTENY138L mutant. Downregulation of PTEN protein phosphatase activity by HCV affects cholesterol metabolism, thereby inducing the appearance of large lipid droplets and increasing virion egress.

Hepatitis C virus impairs TLR3 signaling and inhibits IFN-λ 1 expression in human hepatoma cell line

Toll-like receptor 3 (TLR3) activation plays an important role in the innate immune responses to viral infections. We show here that the activation of TLR3 signaling pathway by poly I:C, a synthetic mimic of dsRNA, could induce high-level expression of interferon (IFN)-λ1 in a hepatoma cell line. The induced IFN-λ1 contributed to poly I:C-mediated inhibition of hepatitis C virus (HCV) Japanese fulminant hepatitis-1 (JFH-1) replication in Huh7 cells. This inhibitory effect of poly I:C on HCV replication, however, was compromised by HCV infection of Huh7 cells. Investigation of the mechanisms showed that HCV infection suppressed the expression of poly I:C-induced IFN-λ1 and IFN-stimulated genes [IFN-stimulated gene 56 (ISG-56), myxovirus resistance A (MxA) and 2'-5'-oligoadenylate synthetase 1 (OAS-1))], the key antiviral elements in IFN signaling pathway. Among the HCV nonstructural (NS) proteins tested, NS3/4A, NS5A and NS5B had the ability to inhibit poly I:C-induced IFN-λ1 expression in Huh7 cells. These observations provide the experimental evidence that HCV and its proteins impair TLR3 signaling and inhibit intracellular IFN-λ1/ISG expression in a hepatoma cell line, which may account for HCV persistence in the liver.

25-hydroxyvitamin D3 suppresses hepatitis C virus production

Because the current interferon (IFN)-based treatment for hepatitis C virus (HCV) infection has a therapeutic limitation and side effects, a more efficient therapeutic strategy is desired. Recent studies show that supplementation of vitamin D significantly improves sustained viral response via IFN-based therapy. However, mechanisms and an active molecular form of vitamin D for its anti-HCV effects have not been fully clarified. To address these questions, we infected HuH-7 cells with cell culture-generated HCV in the presence or absence of vitamin D(3) or its metabolites. To our surprise, 25-hydroxyvitamin D(3) [25(OH)D(3) ], but not vitamin D(3) or 1,25-dihydroxyvitamin D(3) , reduced the extra- and intracellular levels of HCV core antigen in a concentration-dependent manner. Single-cycle virus production assay with a CD81-negative cell line reveals that the inhibitory effect of 25(OH)D(3) is at the level of infectious virus assembly but not entry or replication. Long-term 25(OH)D(3) treatment generates a HCV mutant with acquired resistance to 25(OH)D(3) , and this mutation resulting in a N1279Y substitution in the nonstructural region 3 helicase domain is responsible for the resistance. 25(OH)D(3) is a novel anti-HCV agent that targets an infectious viral particle assembly step. This finding provides insight into the improved efficacy of anti-HCV treatment via the combination of vitamin D(3) and IFN. Our results also suggest that 25(OH)D(3) , not vitamin D(3) , is a better therapeutic option in patients with hepatic dysfunction and reduced enzymatic activity for generation of 25(OH)D(3) .

The pan-genotype specificity of the hepatitis C virus anti-core monoclonal antibody C7-50 is contingent on the quasispecies profile of a population

The inter/intra-genotype quasispecies makeup of hepatitis C virus (HCV) has retarded the development of antibodies capable of pan-genotype reactivity. Mutations, even in conserved domains, are tolerated to a degree. In this report, we characterise the pan-genotype specificity of the commercially available monoclonal anti-HCV core antibody C7-50. We demonstrate the antibody's ability to detect HCV core protein following infection of Huh7 cells with serum-derived HCV of genotypes 2-5 and that a single-site polymorphism in a genotype 3a core amino acid sequence is sufficient to disrupt antibody recognition of the epitope. This same polymorphism is a feature of genotype 3 viruses.

A Daphnane Diterpenoid Isolated from Wikstroemia polyantha Induces an Inflammatory Response and Modulates miRNA Activity

MicroRNAs (miRNAs) are endogenously expressed single-stranded ∼21–23 nucleotide RNAs that inhibit gene expression post-transcriptionally by binding imperfectly to elements usually within the 3′untranslated region (3′UTR) of mRNAs. Small interfering RNAs (siRNAs) mediate site-specific cleavage by binding with perfect complementarity to RNA. Here, a cell-based miRNA reporter system was developed to screen for compounds from marine and plant extracts that inhibit miRNA or siRNA activity. The daphnane diterpenoid genkwanine M (GENK) isolated from the plant Wikstroemia polyantha induces an early inflammatory response and can moderately inhibit miR-122 activity in the liver Huh-7 cell line. GENK does not alter miR-122 levels nor does it directly inhibit siRNA activity in an in vitro cleavage assay. Finally, we demonstrate that GENK can inhibit HCV infection in Huh-7 cells. In summary, the development of the cell-based miRNA sensor system should prove useful in identifying compounds that affect miRNA/siRNA activity.

Narasin, a Novel Antiviral Compound that Blocks Dengue Virus Protein Expression

Dengue virus (DENV) is a mosquito-borne virus that causes a spectrum of human diseases ranging from mild dengue fever to dengue haemorrhagic fever and dengue shock syndrome in severe cases. Currently, there is no effective antiviral therapy or vaccine against DENV infection. In order to identify potential antiviral agents against DENV, we performed high-throughput cell-based screening on a highly purified natural products library. Among the screening hits, selected compounds which displayed 50-75% inhibition against DENV2 were validated using secondary assays. Time-of-addition studies, dose-dependent assays, real time quantitative reverse transcriptase (RT)-PCR, Western blot and ultrastructural imaging were conducted in an attempt to elucidate the potential antiviral mechanisms of narasin. In this study, an ionophore, narasin was selected for detailed analysis due to its strong inhibitory profile against DENV infection with minimal cytotoxicity (50% cytotoxic concentration >1,000 μM). A dose-dependent study revealed narasin to have an 50% inhibitory concentration of less than 1 μM against all four serotypes of DENV. Time-of-addition studies of narasin-treated, DENV2-infected Huh-7 cells suggested narasin to be involved in inhibiting the post-entry stages of viral replication during DENV infection. Proteomic and ultrastructural analyses revealed the antiviral mechanism of narasin as likely to be associated with the disruption of viral protein synthesis. In addition, quantitative RT-PCR studies showed no differences in viral RNA levels between narasin-treated and control DENV2-infected cells. Narasin was identified and characterized as a novel agent that inhibits DENV replication in vitro through non-cytotoxic mechanisms, thus indicating its potential to be further developed as a therapeutic anti-DENV agent.