Targeting host factors: A novel rationale for the management of hepatitis C virus

Host proteins Alpha-2-Macroglobulin and LRP1 associate with Chandipura virus

Chandipura Virus is an emerging tropical pathogen with a high mortality rate among children. No mode of treatment or antivirals exists against CHPV infection, due to little information regarding its host interaction. Studying viral pathogen interaction with its host can not only provide valuable information regarding its propagation strategy, but also on which host proteins interact with the virus. Identifying these proteins and understanding their role in the infection process can provide more stable anti-viral targets. In this study, we focused on identifying host factors that interact with CHPV and may play a critical role in CHPV infection. We are the first to report the successful identification of Alpha-2-Macroglobulin (A2M), a secretory protein of the host that interacts with CHPV. We also established that LRP1 (Low-density lipoprotein receptor-related protein 1) and GRP78 (Glucose regulated protein 78), receptors of A2M, also interact with CHPV. Furthermore, we could also demonstrate that knocking out A2M has a severe effect on viral infection. We conclusively show the interaction of these host proteins with CHPV. Our findings also indicate that these host proteins could play a role in viral entry into the host cell.

Neoechinulins: Molecular, cellular, and functional attributes as promising therapeutics against cancer and other human diseases

Neoechinulins are fungal and plant-derived chemicals extracted from Microsporum sp., Eurotium rubrum, Aspergillus sp., etc. Two analogues of neoechinulin, i.e., A and B, exerted extensive pharmacological properties described in this review. Neoechinulin is an indole alkaloid and has a double bond between C8/C9, which tends to contribute to its cytoprotective nature. Neoechinulin A exhibits protection to PC12 cells against nitrosative stress via increasing NAD(P)H reserve capacity and decreasing cellular GSH levels. It also confers protection via rescuing PC12 cells from rotenone-induced stress by lowering LDH leakage. This compound has great positive potential against neurodegenerative diseases by inhibiting SIN-1 induced cell death in neuronal cells. Together with these, neoechinulin A tends to inhibit Aβ42-induced microglial activation and confers protection against neuroinflammation. Alongside, it also inhibits cervical cancer cells by caspase-dependent apoptosis and via upregulation of apoptosis inducing genes like Bax, it suppresses LPS-induced inflammation in RAW264.7 macrophages and acts as an antidepressant. Whereas, another analogue, Neoechinulin B tends to interfere with the cellular mechanism thereby, inhibiting the entry of influenza A virus and it targets Liver X receptor (LXR) and decreases the infection rate of Hepatitis C. The present review describes the pharmaceutical properties of neoechinulins with notes on their molecular, cellular, and functional basis and their therapeutic properties.

Therapeutic potential of bicyclol in liver diseases: Lessons from a synthetic drug based on herbal derivative in traditional Chinese medicine

Bicyclol, an innovative chemical drug with proprietary intellectual property rights in China, is based on derivative of traditional Chinese medicine (TCM) Schisandra chinensis (Wuweizi) of North. Mounting data has proved that bicyclol has therapeutic potential in various pathological conditions in liver. In this narrative review, we provide the first summary of pharmacological activities, pharmacokinetic characteristics and toxicity of bicyclol, and discuss future research perspectives. Our results imply that bicyclol has a wide spectrum of pharmacological properties, including anti-viral, anti-inflammatory, immuno-regulatory, anti-oxidative, antisteatotic, anti-fibrotic, antitumor, cell death regulatory effects and modulation of heat shock proteins. Pharmacokinetic studies have indicated that bicyclol is the main substrate of CYP3A/2E1. Additionally, no obvious drug interactions have been found when bicyclol is administered simultaneously with other prescriptions. Furthermore, the results of chronic toxicity have strongly addressed that bicyclol has no noticeable toxic effects on all biochemical indices and pathological examinations of the main organs. In view of good pharmacological actions and safety, bicyclol is anticipated to be a potential candidate for various liver diseases, including acute liver injury, fulminant hepatitis, non-alcoholic fatty liver disease, fibrosis and hepatocellular carcinoma. Further studies are therefore required to delineate its molecular mechanisms and targets to confer this well-designed drug a far greater potency. We hope that bicyclol-based therapeutics for liver diseases might be broadly used in clinical practice worldwide.

A proof-of-concept study in HCV-infected Huh7.5 cells for shortening the duration of DAA-based triple treatment regimens

With the development of more effective direct-acting antivirals (DAAs), dual- or triple-therapy regimens represent the major strategy used to cure chronic hepatitis C virus (HCV) infection. Thus, shorter treatment duration regimens with low burden, few adverse effects and good patient adherence are urgently needed. This study theoretically demonstrates a proof-of-concept approach for shortening therapy duration by examining HCV-infected Huh7.5 cells after treatment with a high or low fixed dose of three DAAs (simeprevir + daclatasvir + sofosbuvir) for 6-15 days. The results demonstrated that HCV-infected Huh7.5 cells achieved an ultrarapid virologic response with undetectable HCV RNA and protein and were cured after treatment with the triple-therapy regimen for 15 days. When the treatment duration was shortened, virologic relapse might occur after treatment with a low fixed dose of the three DAAs for 9 days and did occur after treatment with a low fixed dose for 6 days, although HCV was below detectable levels at the end of treatment. However, virologic relapse could be avoided with treatment of a high fixed dose of the three DAAs for 9 or 6 days. Although a virologic breakthrough occurred after an intermittent treatment regimen at the low fixed dose, the high fixed dose cured HCV-positive Huh7.5 cells with intermittent treatment. In conclusion, HCV is persistently present below detectable levels in HCV-infected Huh7.5 cells for a long time after treatment, and a shortened therapy duration is associated with an increased risk of virologic relapse, but virologic relapse or breakthrough might be avoided by treatment with a combination of more highly effective DAAs.

Direct-acting antiviral hepatitis C virus treatment perturbation of the metabolic milieu

OBJECTIVE

Hepatitis C virus (HCV), cirrhosis, and HCV medications including direct-acting antivirals (DAAs) ±ribavirin may all influence the metabolic milieu. While interferon-based regimens improve glucose tolerance, evidence is limited on DAAs. Cases of elevated lactate have recently been reported in patients treated with DAAs, and lactic acidosis is a known complication of antivirals used to treat hepatitis B virus and HIV.

PATIENTS AND METHODS

Measures were evaluated at baseline, week 4, end of treatment, and 12-24 weeks after treatment. Mixed-effects modeling was used to determine factors influencing glucose and lactate over time.

RESULTS

In total, 442 patients were treated (mean age 56, 65% male, 72% genotype 1, 48% cirrhotic). Glucose did not change on or after DAA treatment from baseline (P=0.51) aside from those with untreated diabetes, which declined (P=0.02). Overall, there was a decline in lactate following HCV treatment (mean 2.4-2.1 mmol/l; P<0.001). Lactate initially increased on treatment and then decreased after treatment completion in male patients treated with ribavirin. This pattern was not observed in other groups. There was no evidence of lactic acidosis with HCV nucleotide use.

CONCLUSION

Distinct glucose and lactate trajectories were identified without evidence of DAA metabolic toxicity. HCV treatment does not improve random glucose levels aside from perhaps in untreated diabetic patients.

Up-regulation of glycolipid transfer protein by bicyclol causes spontaneous restriction of hepatitis C virus replication

Bicyclol is a synthetic drug for hepatoprotection in clinic since 2004. Preliminary clinical observations suggest that bicyclol might be active against hepatitis C virus (HCV) with unknown mechanism. Here, we showed that bicyclol significantly inhibited HCV replication in vitro and in hepatitis C patients. Using bicyclol as a probe, we identified glycolipid transfer protein (GLTP) to be a novel restrictive factor for HCV replication. The GLTP preferentially bound host vesicle-associated membrane protein-associated protein-A (VAP-A) in competition with the HCV NS5A, causing an interruption of the complex formation between VAP-A and HCV NS5A. As the formation of VAP-A/NS5A complex is essential for viral RNA replication, up-regulation of GLTP by bicyclol reduced the level of VAP-A/NS5A complex and thus inhibited HCV replication. Bicyclol also exhibited an inhibition on HCV variants resistant to direct-acting antiviral agents (DAAs) with an efficacy identical to that on wild type HCV. In combination with bicyclol, DAAs inhibited HCV replication in a synergistic fashion. GLTP appears to be a newly discovered host restrictive factor for HCV replication, Up-regulation of GLTP causes spontaneous restriction of HCV replication.

Evolution of efficacious pangenotypic hepatitis C virus therapies

Hepatitis C compromises the quality of life of more than 350 million individuals worldwide. Over the last decade, therapeutic regimens for treating hepatitis C virus (HCV) infections have undergone rapid advancements. Initially, structure-based drug design was used to develop molecules that inhibit viral enzymes. Subsequently, establishment of cell-based replicon systems enabled investigations into various stages of HCV life cycle including its entry, replication, translation, and assembly, as well as role of host proteins. Collectively, these approaches have facilitated identification of important molecules that are deemed essential for HCV life cycle. The expanded set of putative virus and host-encoded targets has brought us one step closer to developing robust strategies for efficacious, pangenotypic, and well-tolerated medicines against HCV. Herein, we provide an overview of the development of various classes of virus and host-directed therapies that are currently in use along with others that are undergoing clinical evaluation.

Repurposed FDA-Approved drug sorafenib reduces replication of Venezuelan equine encephalitis virus and other alphaviruses

The New World alphaviruses -Venezuelan, eastern, and western equine encephalitis viruses (VEEV, EEEV, and WEEV respectively) - cause a febrile disease that is often lethal in equines and children and leads to long-term neurological sequelae in survivors. Endemic to the Americas, epizootic outbreaks of the three viruses occur sporadically in the continental United States. All three viruses aerosolize readily, replicate to high titers in cell culture, and have low infectious doses. Additionally, there are no FDA-approved vaccines or therapeutics for human use. To address the therapeutic gap, a high throughput assay utilizing a luciferase reporter virus, TC83-luc, was performed to screen a library of commercially available, FDA-approved drugs for antiviral activity. From a group of twenty compounds found to significantly decrease luminescence, the carcinoma therapeutic sorafenib inhibited replication of VEEV-TC83 and TrD in vitro. Additionally, sorafenib inhibited replication of EEEV and two Old World alphaviruses, Sindbis virus and chikungunya virus, at 8 and 16 h post-infection. Sorafenib caused no toxicity in Vero cells, and coupled with a low EC₅₀ value, yielded a selectivity index of >19. Mechanism of actions studies suggest that sorafenib inhibited viral translation through dephosphorylation of several key proteins, including eIF4E and p70S6K, leading to a reduction in viral protein production and overall viral replication.

An Effective Antiviral Approach Targeting Hepatitis B Virus with NJK14047, a Novel and Selective Biphenyl Amide p38 Mitogen-Activated Protein Kinase Inhibitor

Despite recent advances in therapeutic strategies against hepatitis B virus (HBV) infection, chronic hepatitis B remains a major global health burden. Recent studies have shown that targeting host factors instead of viral factors can be an effective antiviral strategy with low risk of the development of resistance. Efforts to identify host factors affecting viral replication have identified p38 mitogen-activated protein kinase (MAPK) as a possible target for antiviral strategies against various viruses, including HBV. Here, a series of biphenyl amides were synthesized as novel p38 MAPK selective inhibitors and assessed for their anti-HBV activities. The suppression of HBV surface antigen (HBsAg) production by these compounds was positively correlated with p38 MAPK-inhibitory activity. The selected compound NJK14047 displayed significant anti-HBV activity, as determined by HBsAg production, HBeAg secretion, and HBV production. NJK14047 efficiently suppressed the secretion of HBV antigens and HBV particles from HBV genome-transfected cells and HBV-infected sodium taurocholate cotransporting polypeptide-expressing human hepatoma cells. Furthermore, NJK14047 treatment resulted in a significant decrease of pregenomic RNA and covalently closed circular DNA (cccDNA) of HBV in HBV-harboring cells, indicating its ability to inhibit HBV replication. Considering that suppression of HBsAg secretion and elimination of cccDNA of HBV are the major aims of anti-HBV therapeutic strategies, the results suggested the potential use of these compounds as a novel class of anti-HBV agents targeting host factors critical for viral infection.

Fungus-Derived Neoechinulin B as a Novel Antagonist of Liver X Receptor, Identified by Chemical Genetics Using a Hepatitis C Virus Cell Culture System

Cell culture systems reproducing virus replication can serve as unique models for the discovery of novel bioactive molecules. Here, using a hepatitis C virus (HCV) cell culture system, we identified neoechinulin B (NeoB), a fungus-derived compound, as an inhibitor of the liver X receptor (LXR). NeoB was initially identified by chemical screening as a compound that impeded the production of infectious HCV. Genome-wide transcriptome analysis and reporter assays revealed that NeoB specifically inhibits LXR-mediated transcription. NeoB was also shown to interact directly with LXRs. Analysis of structural analogs suggested that the molecular interaction of NeoB with LXR correlated with the capacity to inactivate LXR-mediated transcription and to modulate lipid metabolism in hepatocytes. Our data strongly suggested that NeoB is a novel LXR antagonist. Analysis using NeoB as a bioprobe revealed that LXRs support HCV replication: LXR inactivation resulted in dispersion of double-membrane vesicles, putative viral replication sites. Indeed, cells treated with NeoB showed decreased replicative permissiveness for poliovirus, which also replicates in double-membrane vesicles, but not for dengue virus, which replicates via a distinct membrane compartment. Together, our data suggest that LXR-mediated transcription regulates the formation of virus-associated membrane compartments. Significantly, inhibition of LXRs by NeoB enhanced the activity of all known classes of anti-HCV agents, and NeoB showed especially strong synergy when combined with interferon or an HCV NS5A inhibitor. Thus, our chemical genetics analysis demonstrates the utility of the HCV cell culture system for identifying novel bioactive molecules and characterizing the virus-host interaction machinery.

IMPORTANCE

Hepatitis C virus (HCV) is highly dependent on host factors for efficient replication. In the present study, we used an HCV cell culture system to screen an uncharacterized chemical library. Our results identified neoechinulin B (NeoB) as a novel inhibitor of the liver X receptor (LXR). NeoB inhibited the induction of LXR-regulated genes and altered lipid metabolism. Intriguingly, our results indicated that LXRs are critical to the process of HCV replication: LXR inactivation by NeoB disrupted double-membrane vesicles, putative sites of viral replication. Moreover, NeoB augmented the antiviral activity of all known classes of currently approved anti-HCV agents without increasing cytotoxicity. Thus, our strategy directly links the identification of novel bioactive compounds to basic virology and the development of new antiviral agents.

The Amino Acid Substitution Q65H in the 2C Protein of Swine Vesicular Disease Virus Confers Resistance to Golgi Disrupting Drugs

Swine vesicular disease virus (SVDV) is a porcine pathogen and a member of the species Enterovirus B within the Picornaviridae family. Brefeldin A (BFA) is an inhibitor of guanine nucleotide exchange factors of Arf proteins that induces Golgi complex disassembly and alters the cellular secretory pathway. Since BFA has been shown to inhibit the RNA replication of different enteroviruses, including SVDV, we have analyzed the effect of BFA and of golgicide A (GCA), another Golgi disrupting drug, on SVDV multiplication. BFA and GCA similarly inhibited SVDV production. To investigate the molecular basis of the antiviral effect of BFA, SVDV mutants with increased resistance to BFA were isolated. A single amino acid substitution, Q65H, in the non-structural protein 2C was found to be responsible for increased resistance to BFA. These results provide new insight into the relationship of enteroviruses with the components of the secretory pathway and on the role of SVDV 2C protein in this process.

Identification of novel anti-hepatitis C virus agents by a quantitative high throughput screen in a cell-based infection assay

Hepatitis C virus (HCV) poses a major health threat to the world. The recent development of direct-acting antivirals (DAAs) against HCV has markedly improved the response rate of HCV and reduced the side effects in comparison to the interferon-based therapy. Despite this therapeutic advance, there is still a need to develop new inhibitors that target different stages of the HCV life cycle because of various limitations of the current regimens. In this study, we performed a quantitative high throughput screening of the Molecular Libraries Small Molecule Repository (MLSMR) of ∼350,000 chemicals for novel HCV inhibitors using our previously developed cell-based HCV infection assay. Following confirmation and structural clustering analysis, we narrowed down to 158 compounds from the initial ∼3000 molecules that showed inhibitory activity for further structural and functional analyses. We were able to assign the majority of these compounds to specific stage(s) in the HCV life cycle. Three of them are direct inhibitors of NS3/4A protease. Most of the compounds appear to act on novel targets in HCV life cycle. Four compounds with novel structure and excellent drug-like properties, three targeting HCV entry and one targeting HCV assembly/secretion, were advanced for further development as lead hits. These compounds represent diverse chemotypes that are potential lead compounds for further optimization and may offer promising candidates for the development of novel therapeutics against HCV infection. In addition, they represent novel molecular probes to explore the complex interactions between HCV and the cells.

CD81 and CLDN1 polymorphisms and hepatitis C virus infection susceptibility: a case control study

CD81 and CLDN1 interact to form a CD81-CLDN1 co-receptor complex that is crucial in hepatitis C virus (HCV) entry. Variations in the two genes were shown to influence immunological functions; therefore, we hypothesized that polymorphisms in these genes may contribute to HCV susceptibility. A case-control study consisting of 461 patients and 461 controls was conducted to explore the associations between CD81 rs708564 and CLDN1 rs893051 and HCV susceptibility in a Chinese population. We found a decreased HCV risk associated with the CD81 rs708564 TT (odds ratio (OR) = 0.66, 95% CI = 0.44-0.98) genotype. The gene-gene interaction between CD81 and CLDN1 polymorphisms also decreased HCV risk in a joint multiplicative manner (OR for the presence of both CD81 rs708564 TT and CLDN1 rs893051 GG genotypes = 0.59, 95% CI = 0.36-0.97). Furthermore, the CD81 rs708564 TT genotype conferred a more pronounced decrease in HCV susceptibility in combination with lower levels of high-density lipoprotein cholesterol (HDL-C; OR = 0.71, 95% CI = 0.52-0.96), and higher levels of low-density lipoprotein cholesterol (OR = 0.24, 95% CI = 0.09-0.65). We also observed a decreased HCV susceptibility in individuals with higher HDL-C levels who carried the CLDN1 rs893051 G/C genotype. These findings suggest that homozygous CD81 rs708564 TT may be a genetic modifier for avoiding HCV infection whether as a sole single nucleotide polymorphism or combined with the CLDN1 rs893051 GG genotype, and this effect is associated with serum levels of lipoprotein.

Effect of vitamin D therapy on interleukin-6, visfatin, and hyaluronic acid levels in chronic hepatitis C Egyptian patients

Objectives

We aimed to compare serum levels of interleukin-6, visfatin, and hyaluronic acid in chronic hepatitis C Egyptian patients who received standard of care (SOC) therapy for chronic hepatitis C virus (HCV) consisting of pegylated interferon (PEG-IFN) and ribavirin (RBV) and in those who received SOC with vitamin D (vit D) for 48 weeks in HCV genotype 4a subjects.

Design and methods

One hundred chronic HCV patients were classified into two groups: study 50 patients received SOC therapy PEG-IFN/RBV + vit D and control 50 patients received SOC PEG-IFN/RBV without vit D. Both groups were followed up at 12 weeks, 24 weeks, and 48 weeks of treatment.

Results

Results showed a significant elevation in vit D levels in the group treated with SOC and vit D compared to SOC group and a reduction in HCV RNA from the 12th week to reach zero level in the 24th week. Interleukin-6, visfatin, and hyaluronic acid levels were also reduced significantly. Alanine transaminase and aspartate transaminase biomarkers were significantly reduced, indicating decreased liver injury.

Conclusion

SOC PEG-IFN/RBV + vit D therapy for chronic HCV led to reduced interleukin-6, visfatin, and hyaluronic acid levels and follow up liver biochemical biomarkers as aspartate transaminase and alanine transaminase indicates proper liver healing and monitoring.

Nelfinavir impairs glycosylation of herpes simplex virus 1 envelope proteins and blocks virus maturation

Nelfinavir (NFV) is an HIV-1 aspartyl protease inhibitor that has numerous effects on human cells, which impart attractive antitumor properties. NFV has also been shown to have in vitro inhibitory activity against human herpesviruses (HHVs). Given the apparent absence of an aspartyl protease encoded by HHVs, we investigated the mechanism of action of NFV herpes simplex virus type 1 (HSV-1) in cultured cells. Selection of HSV-1 resistance to NFV was not achieved despite multiple passages under drug pressure. NFV did not significantly affect the level of expression of late HSV-1 gene products. Normal numbers of viral particles appeared to be produced in NFV-treated cells by electron microscopy but remain within the cytoplasm more often than controls. NFV did not inhibit the activity of the HSV-1 serine protease nor could its antiviral activity be attributed to inhibition of Akt phosphorylation. NFV was found to decrease glycosylation of viral glycoproteins B and C and resulted in aberrant subcellular localization, consistent with induction of endoplasmic reticulum stress and the unfolded protein response by NFV. These results demonstrate that NFV causes alterations in HSV-1 glycoprotein maturation and egress and likely acts on one or more host cell functions that are important for HHV replication.

Hepatitis C virus resistance to interferon therapy: an alarming situation

Hepatitis C virus is presently a major public health problem across the globe. The main objective in treating hepatitis C virus (HCV) infection is to achieve a sustained virological response (SVR). Interferon-α (IFN-α) and pegylated interferon (PegIFN) in combination with Ribavirin (RBV) are the choice of treatment nowadays against chronic hepatitis C. There are several mechanisms evolved by the hepatitis C virus that facilitate the persistence of virus and further lead the patient’s status as non responder. Various factors involved in patient’s lack ofresponse to the therapy include: (1) viral factors, (2) host factors, (3) molecular mechanisms related to the lack of response and (4) social factors. Herein we have made an attempt to summarize all the related predictors of drug resistance in one article so that the future polices can be planned to overcome this obstacle and potential therapies can be designed by considering these factors.

The myxobacterial metabolite ratjadone A inhibits HIV infection by blocking the Rev/CRM1-mediated nuclear export pathway

BACKGROUND

The nuclear export of unspliced and partially spliced HIV-1 mRNA is mediated by the recognition of a leucine-rich nuclear export signal (NES) in the HIV Rev protein by the host protein CRM1/Exportin1. This makes the CRM1-Rev complex an attractive target for the development of new antiviral drugs. Here we tested the anti-HIV efficacy of ratjadone A, a CRM1 inhibitor derived from myxobacteria.

RESULTS

Ratjadone A inhibits HIV infection in vitro in a dose-dependent manner with EC₅₀ values at the nanomolar range. The inhibitory effect of ratjadone A occurs around 12 hours post-infection and is specific for the Rev/CRM1-mediated nuclear export pathway. By using a drug affinity responsive target stability (DARTS) assay we could demonstrate that ratjadone A interferes with the formation of the CRM1-Rev-NES complex by binding to CRM1 but not to Rev.

CONCLUSION

Ratjadone A exhibits strong anti-HIV activity but low selectivity due to toxic effects. Although this limits its potential use as a therapeutic drug, further studies with derivatives of ratjadones might help to overcome these difficulties in the future.

Imino sugar glucosidase inhibitors as broadly active anti-filovirus agents

Ebola virus and Marburg virus are members of the family of Filoviridae and are etiological agents of a deadly hemorrhagic fever disease. The clinical symptoms of Ebola and Marburg hemorrhagic fevers are difficult to distinguish and there are currently no specific antiviral therapies against either of the viruses. Therefore, a drug that is safe and effective against both would be an enormous breakthrough. We and others have shown that the folding of the glycoproteins of many enveloped viruses, including the filoviruses, is far more dependent upon the calnexin pathway of protein folding than are most host glycoproteins. Drugs that inhibit this pathway would be expected to be selectively antiviral. Indeed, as we summarize in this review, imino sugars that are competitive inhibitors of the host endoplasmic reticular α-glucosidases I and II, which are enzymes that process N-glycan on nascent glycoproteins and thereby inhibit calnexin binding to the nascent glycoproteins, have been shown to have antiviral activity against a number of enveloped viruses including filoviruses. In this review, we describe the state of development of imino sugars for use against the filoviruses, and provide an explanation for the basis of their antiviral activity as well as limitations.

Amiodarone inhibits the entry and assembly steps of hepatitis C virus life cycle

HCV (hepatitis C virus) infection affects an estimated 180 million people in the world's population. Adverse effects occur frequently with current standard treatment of interferon and ribavirin, while resistance of new direct anti-viral agents, NS3 protease inhibitors, is a major concern because of their single anti-HCV mechanism against the viral factor. New anti-viral agents are needed to resolve the problems. Amiodarone, an anti-arrhythmic drug, has recently been shown to inhibit HCV infection in vitro. The detailed mechanism has yet to be clarified. The aim of the present study was to elucidate the molecular mechanism of the inhibitory effect of amiodarone on HCV life cycle. The effect of amiodarone on HCV life cycle was investigated in Huh-7.5.1 cells with HCVcc (cell culture-derived HCV), HCVpp (HCV pseudoviral particles), sub-genomic replicons, IRES (internal ribosomal entry site)-mediated translation assay, and intracellular and extracellular infectivity assays. The administration of amiodarone appeared to inhibit HCV entry independent of genotypes, which was attributed to the down-regulation of CD81 receptor expression. The inhibitory effect of amiodarone also manifested in the HCV assembly step, via the suppression of MTP (microsomal triacylglycerol transfer protein) activity. Amiodarone revealed no effects on HCV replication and translation. With the host factor-targeting characteristics, amiodarone may be an attractive agent for the treatment of HCV infection.

Phosphoinositides: tiny lipids with giant impact on cell regulation

Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.

Host cell factors as antiviral targets in arenavirus infection

Among the members of the Arenaviridae family, Lassa virus and Junin virus generate periodic annual outbreaks of severe human hemorrhagic fever (HF) in endemic areas of West Africa and Argentina, respectively. Given the human health threat that arenaviruses represent and the lack of a specific and safe chemotherapy, the search for effective antiviral compounds is a continuous demanding effort. Since diverse host cell pathways and enzymes are used by RNA viruses to fulfill their replicative cycle, the targeting of a host process has turned an attractive antiviral approach in the last years for many unrelated virus types. This strategy has the additional benefit to reduce the serious challenge for therapy of RNA viruses to escape from drug effects through selection of resistant variants triggered by their high mutation rate. This article focuses on novel strategies to identify inhibitors for arenavirus therapy, analyzing the potential for antiviral developments of diverse host factors essential for virus infection.

Anti-hepatitis C virus activity and toxicity of type III phosphatidylinositol-4-kinase beta inhibitors

Type III phosphatidylinositol-4-kinase beta (PI4KIIIβ) was previously implicated in hepatitis C virus (HCV) replication by small interfering RNA (siRNA) depletion and was therefore proposed as a novel cellular target for the treatment of hepatitis C. Medicinal chemistry efforts identified highly selective PI4KIIIβ inhibitors that potently inhibited the replication of genotype 1a and 1b HCV replicons and genotype 2a virus in vitro. Replicon cells required more than 5 weeks to reach low levels of 3- to 5-fold resistance, suggesting a high resistance barrier to these cellular targets. Extensive in vitro profiling of the compounds revealed a role of PI4KIIIβ in lymphocyte proliferation. Previously proposed functions of PI4KIIIβ in insulin secretion and the regulation of several ion channels were not perturbed with these inhibitors. Moreover, PI4KIIIβ inhibitors were not generally cytotoxic as demonstrated across hundreds of cell lines and primary cells. However, an unexpected antiproliferative effect in lymphocytes precluded their further development for the treatment of hepatitis C.

Characterization of the interaction between hepatitis C virus NS5B and the human oestrogen receptor alpha

The RNA-dependent RNA polymerase (NS5B) of hepatitis C virus (HCV) is part of the viral replicative complex and plays a crucial role in HCV replication. It has been described that NS5B interacts with cellular proteins, and that interactions between NS5B and host proteins are crucial for viral replication. Some of the host factors involved in the HCV replication cycle include the oestrogen receptor alpha (ESR1), protein kinases (c-Src) and chaperones (Hsp70). In this report, we determine the requirements for the interplay between NS5B and the domain C of ESR1 (ESR1C) by using Förster Resonance Energy Transfer. NS5B-ESR1C and ESR1C-ESR1C interactions are dependent on ionic strength, indicating that contacts are mainly electrostatic. Additionally, NS5B residues involved in NS5B oligomerization were also essential for NS5B-ESR1C interaction. The study of the interactions among viral and host factors will provide data to establish innovative therapeutic strategies and the development of new antiviral drugs.

An unhealthy relationship: viral manipulation of the nuclear receptor superfamily

The nuclear receptor (NR) superfamily is a diverse group of over 50 proteins whose function is to regulate the transcription of a vast array of cellular genes. These proteins are able to tune transcription over an extremely dynamic range due to the fact that they may act as either transcriptional activators or repressors depending on promoter context and ligand status. Due to these unique properties, diverse families of viruses have evolved strategies to exploit NRs in order to regulate expression of their own genes and to optimize the cellular milieu to facilitate the viral lifecycle. While the specific NRs targeted by these viruses vary, the strategies used to target them are common. This is accomplished at the cis-level by incorporation of nuclear receptor response elements into the viral genome and at the trans-level by viral proteins that target NRs directly or indirectly to modulate their function. The specific NR(s) targeted by a particular virus are likely to be reflective of the tissue tropism of the virus in question. Thus, the essential role played by NRs in the replication cycles of such diverse viruses underscores the importance of understanding their functions in the context of specific infections. This knowledge will allow appropriate considerations to be made when treating infected individuals with hormone-associated diseases and will potentially assist in the rational design of novel antiviral therapeutics.

c-Fos regulates hepatitis C virus propagation

Hepatitis C virus (HCV) RNA replication requires cellular factors as well as viral non-structural proteins (NS protein). Using small interfering RNA (siRNA) library screening, we previously identified c-Fos as a host factor involved in HCV propagation. In the present study, we demonstrated that silencing of c-Fos expression resulted in decrease of HCV propagation in cell culture grown HCV (HCVcc)-infected cells; whereas overexpression of c-Fos significantly increased HCV propagation. We further confirmed the positive role of c-Fos in HCV propagation by both HCV-luciferase reporter assay and immunofluorescence analysis. We showed that c-Fos level was upregulated by HCV infection. Furthermore, phorbol 12-myristate 13-acetate (PMA)-induced c-Fos level was synergistically increased by HCV infection. These data suggest that c-Fos acts as a positive regulator of HCV propagation and may contribute to HCV-associated pathogenesis.

Meta-analysis: insulin resistance and sustained virological response in hepatitis C

BACKGROUND

A higher baseline homeostasis model assessment of insulin resistance (HOMA-IR) score has sometimes predicted a poorer sustained virological response (SVR) rate to peginterferon/ribavirin therapy in treatment-naïve chronic hepatitis C patients.

AIM

To perform a meta-analysis to evaluate the impact of HOMA-IR on SVR in hepatitis C.

METHODS

Relevant studies were identified by searching Medline and EMBASE. We identified 17 publications that addressed the influence of insulin resistance on SVR. The random effect model of Der Simonian and Laird method were used for heterogeneous studies using the Meta-Disc software 1.4, Madrid, Spain.

RESULTS

Normal insulin sensitivity was associated with a higher rate of SVR [odds ratio (OR) 2.86 (95%CI: 1.97-4.16)] in comparison with insulin resistance. Moreover, in separate analysis by genotype selecting studies that used HOMA-IR > 2 as cut-off defining insulin resistance, SVR was higher in patients with HOMA-IR < 2 in all genotypes: HCV-1 [OR: 2.16 (95%CI: 1.51-3.08)], HCV-2&3 [OR: 3.06 (95%CI: 1.06-8.82)] and HCV-4 [OR: 6.65(95%CI: 2.51-17.61)]. Studies reporting no association between HOMA and SVR included easy-to-cure cohorts, analysed variables strongly related with insulin resistance like body mass index, steatosis, hyper γGT, age and fibrosis and reported differences in handling and interpretation of HOMA-IR.

CONCLUSION

Elevated HOMA-IR was associated with a lower cure rate of patients with hepatitis C treated with Peg-IFN-α/ribavirin irrespective of genotype, and the more difficult-to-treat cohort, the better the HOMA-IR prediction. HOMA-IR is, as a surrogate marker of insulin resistance, susceptible to some biases derived from both handling and interpretation.

6-desfluoroquinolones as HIV-1 Tat-mediated transcription inhibitors

The current anti-HIV treatments fail to completely eradicate the virus in HIV-infected individuals, mainly as a result of a small pool of latently infected cells. This issue, together with the emergence of multidrug-resistant viruses, clearly highlights the need to find additional strategies. An overview of the Tat-mediated transcription inhibitors 6-desfluoroquinolones (6-DFQs), identified by our group, is given in this review along with a critical appraisal of their advantages and drawbacks. Attempts are also made to place them within the context of new potential anti-HIV therapeutics. Due to their innovative mechanism of action, the 6-DFQs could be interesting candidates for use in association with the currently used cocktail of drugs. Their potential as antivirals deserves further investigation.

Insulin resistance and chronic liver disease

Increased insulin resistance is frequently associated with chronic liver disease and is a pathophysiological feature of hepatogenous diabetes. Distinctive factors including hepatic parenchymal cell damage, portal-systemic shunting and hepatitis C virus are responsible for the development of hepatogenous insulin resistance/diabetes. Although it remains unclear whether insulin secretion from pancreatic beta cells is impaired as it is in type 2 diabetes, retinopathic and cardiovascular risk is low and major causes of death in cirrhotic patients with diabetes are liver failure, hepatocellular carcinoma and gastrointestinal hemorrhage. Hemoglobin A1c is an inaccurate marker for the assessment and management of hepatogenous diabetes. Moreover, exogenous insulin or sulfonylureas may be harmful because these agents may promote hepatocarcinogenesis. Thus, pathogenesis, cause of death, assessment and therapeutic strategy for hepatogenous insulin resistance/diabetes differ from those for lifestyle-related type 2 diabetes. In this article, we review features of insulin resistance in relationship to chronic liver disease. We also discuss the impact of anti-diabetic agents on interferon treatment and hepatocarcinogenesis.

Structural investigation of the naphthyridone scaffold: identification of a 1,6-naphthyridone derivative with potent and selective anti-HIV activity

Building upon a large, previously reported series of anti-HIV 6-desfluoroquinolones endowed with a peculiar mechanism of action, the inhibition of Tat-mediated transcription, replacement of the quinolone nucleus with a naphthyridone core was shown to be very productive. In this work, the naphthyridone scaffold was investigated in depth by synthesizing various analogues. This led to the identification of NM13 as the most selective derivative obtained in MT-4 cells. It is the result of the successful combination of the 1,6-naphthyridone nucleus and the C7 benzothiazolpiperazine group, which, for the first time, not only grants potent anti-HIV activity but displays very high selectivity. Further studies aimed at a more thorough investigation of the anti-HIV profile of this new derivative are in progress.

Inhibition of enveloped virus infection of cultured cells by valproic acid

Valproic acid (VPA) is a short-chain fatty acid commonly used for treatment of neurological disorders. As VPA can interfere with cellular lipid metabolism, its effect on the infection of cultured cells by viruses of seven viral families relevant to human and animal health, including eight enveloped and four nonenveloped viruses, was analyzed. VPA drastically inhibited multiplication of all the enveloped viruses tested, including the zoonotic lymphocytic choriomeningitis virus and West Nile virus (WNV), while it did not affect infection by the nonenveloped viruses assayed. VPA reduced vesicular stomatitis virus infection yield without causing a major blockage of either viral RNA or protein synthesis. In contrast, VPA drastically abolished WNV RNA and protein synthesis, indicating that this drug can interfere the viral cycle at different steps of enveloped virus infection. Thus, VPA can contribute to an understanding of the crucial steps of viral maturation and to the development of future strategies against infections associated with enveloped viruses.

Anti-hepatitis C virus activity of Acacia confusa extract via suppressing cyclooxygenase-2

Chronic hepatitis C virus (HCV) infection continues to be an important cause of morbidity and mortality by chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) throughout the world. It is of tremendous importance to discover more effective and safer agents to improve the clinical treatment on HCV carriers. Here we report that the n-butanol-methanol extract obtained from Acacia confusa plant, referred as ACSB-M4, exhibited the inhibition of HCV RNA replication in the HCV replicon assay system, with an EC(50) value and CC(50)/EC(50) selective index (SI) of 5 ± 0.3 μg/ml and >100, respectively. Besides, ACSB-M4 showed antiviral synergy in combination with IFN-α and as HCV protease inhibitor (Telaprevir; VX-950) and polymerase inhibitor (2'-C-methylcytidine; NM-107) by a multiple linear logistic model and isobologram analysis. A complementary approach involving the overexpression of COX-2 protein in ACSB-M4-treated HCV replicon cells was used to evaluate the antiviral action at the molecular level. ACSB-M4 significantly suppressed COX-2 expression in HCV replicon cells. Viral replication was gradually restored if COX-2 was added simultaneously with ACSB-M4, suggesting that the anti-HCV activity of ACSB-M4 was associated with down-regulation of COX-2, which was correlated with the suppression of nuclear factor-kappaB (NF-κB) activation. ACSB-M4 may serve as a potential protective agent for use in the management of patients with chronic HCV infection.

Insulin resistance predicts rapid virologic response to peginterferon/ribavirin combination therapy in hepatitis C genotype 4 patients

OBJECTIVES

In patients with chronic hepatitis C (CHC) of genotype 4, the predictors of rapid virologic response (RVR) have not been determined adequately. We aimed to assess which pretreatment variables might predict an RVR and a sustained virologic response (SVR).

METHODS

A total of 131 non-diabetic, genotype 4 CHC patients were enrolled for analysis and treated with peginterferon-alpha-2b/ribavirin. Insulin resistance (IR) was evaluated by homeostasis model assessment-IR (HOMA-IR). Hepatitis C virus (HCV)-RNA levels were measured at baseline, during therapy and at follow-up.

RESULTS

The overall SVR rate was 60.3%. The SVR rate in patients with an RVR was 100%. Age, HOMA-IR, fibrosis, severity of the steatosis, and HCV viral load were all significantly associated with RVR in the univariate analysis. After logistic regression, both HOMA-IR (odds ratio: 0.12, P=0.002) and HCV viral load (odds ratio: 1.43, P=0.02) remained independent variables associated with RVR. Age, HOMA-IR, viral load, fibrosis, RVR, and "complete" early virological response were all significantly associated with SVR in the univariate analysis. After logistic regression, fibrosis (odds ratio: 5.23, P=0.007), HOMA-IR (odds ratio: 14.29, P=0.004), and viral load (odds ratio: 0.16, P=0.005) were independent factors associated with SVR. By linear regression, body mass index (P=0.001) and waist circumference (P=0.0003) were independently associated with HOMA-IR.

CONCLUSIONS

IR is a major determinant of both RVR and SVR in genotype 4 CHC patients. HOMA-IR would seem to be a useful tool for predicting the response to therapy.

Review article: specifically targeted anti-viral therapy for hepatitis C - a new era in therapy

BACKGROUND

Novel, directly acting anti-viral agents, also named 'specifically targeted anti-viral therapy for hepatitis C' (STAT-C) compounds, are currently under development.

AIM

To review the potential of STAT-C agents which are currently under clinical development, with a focus on agents that target HCV proteins.

METHODS

Studies evaluating STAT-C compounds were identified by systematic literature search using PubMed as well as databases of abstracts presented in English at recent liver and gastroenterology congresses.

RESULTS

Numerous directly-acting anti-viral agents are currently under clinical phase I-III evaluation. Final results of phase II clinical trials evaluating the most advanced compounds telaprevir and boceprevir indicate that the addition of these NS3/4A protease inhibitors to pegylated interferon-alfa and ribavirin strongly improves the chance to achieve a SVR in treatment-naive HCV genotype 1 patient as well as in prior nonresponders and relapsers to standard therapy. Monotherapy with directly acting anti-virals is not suitable. NS5B polymerase inhibitors in general have a lower anti-viral efficacy than protease inhibitors.

CONCLUSIONS

STAT-C compounds in addition to pegylated interferon-alfa and ribavirin can improve SVR rates at least in HCV genotype 1 patients. Future research needs to evaluate whether a SVR can be achieved by combination therapies of STAT-C compounds in interferon-free regimens.

Role of host cell factors in flavivirus infection: Implications for pathogenesis and development of antiviral drugs

The genus Flavivirus contains approximately 70 arthropod-borne enveloped RNA viruses many of which cause severe human and in some cases, animal disease. They include dengue virus, yellow fever virus, West Nile virus, Japanese encephalitis virus, and tick-borne encephalitis virus. Hundreds of thousands of deaths due to flavivirus infections occur each year, many of which are unpreventable due to lack of availability of appropriate vaccines and/or antiviral drugs. Flaviviruses exploit the cytoplasmic cellular machinery to facilitate propagation of infectious progeny virions. They engage in dynamic and antagonistic interactions with host cell membranes and biochemical processes. Following infection, the cells initiate various antiviral strategies to counteract viral invasion. In its defense, the virus has alternative strategies to suppress these host responses to infection. The fine balance between these interactions determines the outcome of the viral infection and disease progression. Published studies have revealed specific effects of flaviviruses on cellular processes, but the underlying mechanisms that determine the specific cytopathogenetic changes induced by different flaviviruses have not, as yet, been elucidated. Independently of the suppression of the type I IFN response which has been described in detail elsewhere, this review focuses on recent discoveries relating to alterations of host metabolism following viral infection. Such studies may contribute to new approaches to antiviral drug development. The role of host cellular factors will be examined in the context of protection and/or pathogenesis resulting from flavivirus infection, with particular emphasis on West Nile virus and dengue virus.