Hirofumi Ohashi

Interleukin-1 and tumor necrosis factor-α trigger restriction of hepatitis B virus infection via a cytidine deaminase activation-induced cytidine deaminase (AID).

Background: Cytokines and host factors triggering innate immunity against hepatitis B virus (HBV) are not well understood. Results: IL-1 and TNFα induced cytidine deaminase AID, an anti-HBV host factor, and reduced HBV infection into hepatocytes. Conclusion: IL-1/TNFα reduced host susceptibility to HBV infection through AID up-regulation. Significance: Proinflammatory cytokines modulate HBV infection through a novel innate immune pathway involving AID. Virus infection is restricted by intracellular immune responses in host cells, and this is typically modulated by stimulation of cytokines. The cytokines and host factors that determine the host cell restriction against hepatitis B virus (HBV) infection are not well understood. We screened 36 cytokines and chemokines to determine which were able to reduce the susceptibility of HepaRG cells to HBV infection. Here, we found that pretreatment with IL-1β and TNFα remarkably reduced the host cell susceptibility to HBV infection. This effect was mediated by activation of the NF-κB signaling pathway. A cytidine deaminase, activation-induced cytidine deaminase (AID), was up-regulated by both IL-1β and TNFα in a variety of hepatocyte cell lines and primary human hepatocytes. Another deaminase APOBEC3G was not induced by these proinflammatory cytokines. Knockdown of AID expression impaired the anti-HBV effect of IL-1β, and overexpression of AID antagonized HBV infection, suggesting that AID was one of the responsible factors for the anti-HBV activity of IL-1/TNFα. Although AID induced hypermutation of HBV DNA, this activity was dispensable for the anti-HBV activity. The antiviral effect of IL-1/TNFα was also observed on different HBV genotypes but not on hepatitis C virus. These results demonstrate that proinflammatory cytokines IL-1/TNFα trigger a novel antiviral mechanism involving AID to regulate host cell permissiveness to HBV infection.

A Novel Tricyclic Polyketide, Vanitaracin A, Specifically Inhibits the Entry of Hepatitis B and D Viruses by Targeting Sodium Taurocholate Cotransporting Polypeptide

ABSTRACT Anti-hepatitis B virus (HBV) drugs are currently limited to nucleos(t)ide analogs (NAs) and interferons. A challenge of drug development is the identification of small molecules that suppress HBV infection from new chemical sources. Here, from a fungus-derived secondary metabolite library, we identify a structurally novel tricyclic polyketide, named vanitaracin A, which specifically inhibits HBV infection. Vanitaracin A inhibited the viral entry process with a submicromolar 50% inhibitory concentration (IC50) (IC50 = 0.61 ± 0.23 μM), without evident cytotoxicity (50% cytotoxic concentration of >256 μM; selectivity index value of >419) in primary human hepatocytes. Vanitaracin A did not affect the HBV replication process. This compound was found to directly interact with the HBV entry receptor sodium taurocholate cotransporting polypeptide (NTCP) and impaired its bile acid transport activity. Consistent with this NTCP targeting, antiviral activity of vanitaracin A was observed with hepatitis D virus (HDV) but not hepatitis C virus. Importantly, vanitaracin A inhibited infection by all HBV genotypes tested (genotypes A to D) and clinically relevant NA-resistant HBV isolate. Thus, we identified a fungal metabolite, vanitaracin A, which was a potent, well-tolerated, and broadly active inhibitor of HBV and HDV entry. This compound, or its related analogs, could be part of an antiviral strategy for preventing reinfection with HBV, including clinically relevant nucleos(t)ide analog-resistant virus. IMPORTANCE For achieving better treatment and prevention of hepatitis B virus (HBV) infection, anti-HBV agents targeting a new molecule are in great demand. Although sodium taurocholate cotransporting polypeptide (NTCP) has recently been reported to be an essential host factor for HBV entry, there is a limited number of reports that identify new compounds targeting NTCP and inhibiting HBV entry. Here, from an uncharacterized chemical library, we isolated a structurally new compound, named vanitaracin A, which inhibited the process of entry of HBV and hepatitis D virus (HDV). This compound was suggested to directly interact with NTCP and inhibit its transporter activity. Importantly, vanitaracin A inhibited the entry of all HBV genotypes examined and of a clinically relevant nucleos(t)ide analog-resistant HBV isolate.

Quantifying antiviral activity optimizes drug combinations against hepatitis C virus infection

Significance Introduction of new anti-hepatitis C virus (HCV) agents, so-called direct-acting antivirals (DAAs), has greatly changed treatment for HCV, and a variety of choices for anti-HCV drug combinations are available. For better management and control of this worldwide infectious disease with anti-HCV agents, it is critical to develop a method for precisely profiling the antiviral efficacy of possible combination drug regimens and seek the “best treatment” based on scientific evidence. In this study, we showed how cell culture data can be combined with a mathematical model and computer simulation to quantify the anti-HCV drug efficacy of different drug concentrations and combinations in a preclinical setting, and hence develop a quantitative basis for selecting drug combinations prior to costly clinical trials. With the introduction of direct-acting antivirals (DAAs), treatment against hepatitis C virus (HCV) has significantly improved. To manage and control this worldwide infectious disease better, the “best” multidrug treatment is demanded based on scientific evidence. However, there is no method available that systematically quantifies and compares the antiviral efficacy and drug-resistance profiles of drug combinations. Based on experimental anti-HCV profiles in a cell culture system, we quantified the instantaneous inhibitory potential (IIP), which is the logarithm of the reduction in viral replication events, for both single drugs and multiple-drug combinations. From the calculated IIP of 15 anti-HCV drugs from different classes [telaprevir, danoprevir, asunaprevir, simeprevir, sofosbuvir (SOF), VX-222, dasabuvir, nesbuvir, tegobuvir, daclatasvir, ledipasvir, IFN-α, IFN-λ1, cyclosporin A, and SCY-635], we found that the nucleoside polymerase inhibitor SOF had one of the largest potentials to inhibit viral replication events. We also compared intrinsic antiviral activities of a panel of drug combinations. Our quantification analysis clearly indicated an advantage of triple-DAA treatments over double-DAA treatments, with triple-DAA treatments showing enhanced antiviral activity and a significantly lower probability for drug resistance to emerge at clinically relevant drug concentrations. Our framework provides quantitative information to consider in designing multidrug strategies before costly clinical trials.

Reply to Padmanabhan and Dixit: Hepatitis C virus entry inhibitors for optimally boosting direct-acting antiviral-based treatments

We thank Padmanabhan and Dixit for their comments (1) on our paper (2). They pointed out that entry inhibitors might form potent partners for optimal drug combinations. They analyzed previously published data on 10 hepatitis C virus (HCV) entry inhibitors that are under clinical or preclinical development and found some of these HCV entry inhibitors showed high instantaneous inhibitory potentials ( IIP s) (3) compared with IIP s of direct-acting antivirals (DAAs). To analyze further the utility of combining entry inhibitors with other DAAs and to extend our original results (2), we quantified the anti-HCV effect of four different classes of entry inhibitors [AR4A (anti-HCV E2 antibody) (4), BLT-1 \[scavenger receptor class B type 1 (SR-BI) inhibitor\] (5), erlotinib (EGF receptor inhibitor) (6), and dasatinib (EphA2 inhibitor) (6)] singly and in combination with six DAAs studied by Padmanabhan and Dixit (1) in the HCV infectious cell culture system (Fig. 1 A and B ). Single treatment of these entry inhibitors exhibited a dose-dependent reduction in HCV RNA … [↵][1]2To whom correspondence may be addressed. Email: siwami{at}kyushu-u.org or kwatashi{at}nih.go.jp. [1]: #xref-corresp-1-1

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

ABSTRACT 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.

Chemical array system, a platform to identify novel hepatitis B virus entry inhibitors targeting sodium taurocholate cotransporting polypeptide

Current anti-hepatitis B virus (HBV) agents including interferons and nucleos(t)ide analogs efficiently suppress HBV infection. However, as it is difficult to eliminate HBV from chronically infected liver, alternative anti-HBV agents targeting a new molecule are urgently needed. In this study, we applied a chemical array to high throughput screening of small molecules that interacted with sodium taurocholate cotransporting polypeptide (NTCP), an entry receptor for HBV. From approximately 30,000 compounds, we identified 74 candidates for NTCP interactants, and five out of these were shown to inhibit HBV infection in cell culture. One of such compound, NPD8716, a coumarin derivative, interacted with NTCP and inhibited HBV infection without causing cytotoxicity. Consistent with its NTCP interaction capacity, this compound was shown to block viral attachment to host hepatocytes. NPD8716 also prevented the infection with hepatitis D virus, but not hepatitis C virus, in agreement with NPD8716 specifically inhibiting NTCP-mediated infection. Analysis of derivative compounds showed that the anti-HBV activity of compounds was apparently correlated with the affinity to NTCP and the capacity to impair NTCP-mediated bile acid uptake. These results are the first to show that the chemical array technology represents a powerful platform to identify novel viral entry inhibitors.

Stereo-controlled synthesis of functionalized tetrahydropyridines based on the cyanomethylation of 1,6-dihydropyridines and generation of anti-hepatitis C virus agents

Densely functionalized tetrahydropyridines were stereoselectively synthesized from 1,6-dihydropyridines. Exploiting a carbonyl group installed at the C3 position of the 1,6-dihydropyridine system, we devised a strategy for cyanomethylation at C2/C6 and subsequent divergent installation of an allyl group at C3/C5 in a highly regio- and stereo-controlled manner. This versatile protocol for programmable functionalization of the 1,6-dihydropyridine system allows the divergent and streamlined synthesis of multiply-substituted tetrahydropyridines as an important class of biologically and medicinally relevant scaffolds. Two of the N-heterocyclic compounds bearing an alkyl nitrile group showed anti-hepatitis C virus (HCV) activity.

A new strategy to identify hepatitis B virus entry inhibitors by AlphaScreen technology targeting the envelope-receptor interaction

Current anti-hepatitis B virus (HBV) agents have limited effect in curing HBV infection, and thus novel anti-HBV agents with different modes of action are in demand. In this study, we applied AlphaScreen assay to high-throughput screening of small molecules inhibiting the interaction between HBV large surface antigen (LHBs) and the HBV entry receptor, sodium taurocholate cotransporting polypeptide (NTCP). From the chemical screening, we identified that rapamycin, an immunosuppressant, strongly inhibited the LHBs-NTCP interaction. Rapamycin inhibited hepatocyte infection with HBV without significant cytotoxicity. This activity was due to impaired attachment of the LHBs preS1 domain to cell surface. Pretreatment of target cells with rapamycin remarkably reduced their susceptibility to preS1 attachment, while rapamycin pretreatment to preS1 did not affect its attachment activity, suggesting that rapamycin targets the host side. In support of this, a surface plasmon resonance analysis showed a direct interaction of rapamycin with NTCP. Consistently, rapamycin also prevented hepatitis D virus infection, whose entry into cells is also mediated by NTCP. We also identified two rapamycin derivatives, everolimus and temsirolimus, which possessed higher anti-HBV potencies than rapamycin. Thus, this is the first report for application of AlphaScreen technology that monitors a viral envelope-receptor interaction to identify viral entry inhibitors.

Revealing the characteristics of antiviral agents: ~Evaluation and optimization of anti-hepatitis C virus agents with a mathematical method based on experimental data on virology~

Rapid development of novel anti-hepatitis C virus (HCV) agents in recent years has greatly improved treatment outcomes. However, such rapid progress in anti-HCV treatment has not allowed us to fully argue the different characteristics of each anti-HCV agent, optimal multidrug combinations, and the selection of treatment enabling to efficiently eliminate drug resistant viruses. We here quantified the intrinsic antiviral effect of 15 anti-HCV agents either clinically available or under developmental phase using a cell culture system, and identified the parameters that represent the antiviral profile of drugs through mathematical analysis. A computer simulation that calculated the antiviral activity and the frequency of mutation rate under dual- and triple-multidrug treatment presented the argument for the advantage of multidrug treatments. In this review, we summarize the novel approaches to evaluate intrinsic antiviral efficacy of drugs by combining the virological and mathematical analyses.