Hepatitis B virus efficiently infects non-adherent hepatoma cells via human sodium taurocholate cotransporting polypeptide

Hepatitis B and D virus entry

Hepatitis B virus (HBV) entry is the initial step of viral infection, leading to the formation of covalently closed circular DNA, which is a molecular reservoir of viral persistence and a key obstacle for HBV cure. The restricted entry of HBV into specific cell types determines the nature of HBV, which has a narrow host range in tissues and species. Hepatitis D virus (HDV) shares viral surface antigens with HBV and thus follows a similar entry mechanism at its early stages. In late 2012, sodium taurocholate cotransporting polypeptide was discovered as an HBV and HDV entry receptor. Since then, the mechanisms of HBV and HDV entry have been extensively analysed. These analyses have expanded our understanding of HBV and HDV host tropism and have provided new strategies for the development of antiviral agents. Notably, the structures of sodium taurocholate cotransporting polypeptide and its interaction with the 2-48 amino acid region of viral preS1 have been recently solved. These findings will stimulate further entry studies. In this Review, we summarize current understanding of HBV and HDV entry and future perspectives.

Berberine promotes K48-linked polyubiquitination of HNF4α, leading to the inhibition of HBV replication

The current antiviral agents for the treatment of chronic infection with hepatitis B virus (HBV) do not completely remove covalently closed circular DNA (cccDNA) and integrated viral DNA fragments from patients. Berberine is an isoquinoline alkaloid extracted from various plants and has been reported to inhibit the replication of various types of DNA. In this study, we tested the effects of berberine and its derivatives on HBV infection. Berberine inhibited viral core promoter activity at the highest level among the compounds tested and suppressed HBV production and cccDNA synthesis in primary human hepatocytes and HBV-infected HepG2-NTCP cells at an EC50 value of 3.6 μM and a CC50 value of over 240.0 μM. Compared with other viral promoter activities, berberine treatment potently downregulated core promoter activity and reduced protein levels, but not RNA levels, of hepatic nuclear factor 4α (HNF4α), which primarily enhances enhancer II/core promoter activity. Furthermore, berberine treatment enhanced K48-linked, but not K63-linked, polyubiquitination and subsequent proteasome-dependent degradation of HNF4α. These results suggest that berberine enhances the polyubiquitination- and proteasome-dependent degradation of HNF4α and then inhibits HBV replication via the suppression of core promoter activity. The development of antiviral agents based on berberine may contribute to the amelioration of HBV-related disorders, regardless of the presence of residual cccDNA or integrated viral DNA fragments.

Bile acid-microbiota crosstalk in hepatitis B virus infection

Hepatitis B virus (HBV) is a hepatotropic non-cytopathic virus characterized by liver-specific gene expression. HBV infection highjacks bile acid metabolism, notably impairing bile acid uptake via sodium taurocholate cotransporting polypeptide (NTCP), which is a functional receptor for HBV entry. Concurrently, HBV infection induces changes in bile acid synthesis and the size of the bile acid pool. Conversely, bile acid facilitates HBV replication and expression through the signaling molecule farnesoid X receptor (FXR), a nuclear receptor activated by bile acid. However, in HepaRG cells and primary hepatocytes, FXR agonists suppress HBV RNA expression and the synthesis and secretion of DNA. In the gut, the size and composition of the bile acid pool significantly influence the gut microbiota. In turn, the gut microbiota impacts bile acid metabolism and innate immunity, potentially promoting HBV clearance. Thus, the bile acid-gut microbiota axis represents a complex and evolving relationship in the context of HBV infection. This review explores the interplay between bile acid and gut microbiota in HBV infection and discusses the development of HBV entry inhibitors targeting NTCP.

Cardiac glycosides inhibit early and late vaccinia virus protein expression

Cardiac glycosides (CGs) are natural steroid glycosides, which act as inhibitors of the cellular sodium-potassium ATPase pump. Although traditionally considered toxic to human cells, CGs are widely used as drugs for the treatment of cardiovascular-related medical conditions. More recently, CGs have been explored as potential anti-viral drugs and inhibit replication of a range of RNA and DNA viruses. Previously, a compound screen identified CGs that inhibited vaccinia virus (VACV) infection. However, no further investigation of the inhibitory potential of these compounds was performed, nor was there investigation of the stage(s) of the poxvirus lifecycle they impacted. Here, we investigated the anti-poxvirus activity of a broad panel of CGs. We found that all CGs tested were potent inhibitors of VACV replication. Our virological experiments showed that CGs did not impact virus infectivity, binding, or entry. Rather, experiments using recombinant viruses expressing reporter proteins controlled by VACV promoters and arabinoside release assays demonstrated that CGs inhibited early and late VACV protein expression at different concentrations. Lack of virus assembly in the presence of CGs was confirmed using electron microscopy. Thus, we expand our understanding of compounds with anti-poxvirus activity and highlight a yet unrecognized mechanism by which poxvirus replication can be inhibited.

Broad-spectrum antiviral strategy: Host-targeting antivirals against emerging and re-emerging viruses

Viral infections are amongst the most prevalent diseases that pose a significant threat to human health. Targeting viral proteins or host factors represents two primary strategies for the development of antiviral drugs. In contrast to virus-targeting antivirals (VTAs), host-targeting antivirals (HTAs) offer advantages in terms of overcoming drug resistance and effectively combating a wide range of viruses, including newly emerging ones. Therefore, targeting host factors emerges as an extremely promising strategy with the potential to address critical challenges faced by VTAs. In recent years, extensive research has been conducted on the discovery and development of HTAs, leading to the approval of maraviroc, a chemokine receptor type 5 (CCR5) antagonist used for the treatment of HIV-1 infected individuals, with several other potential treatments in various stages of development for different viral infections. This review systematically summarizes advancements made in medicinal chemistry regarding various host targets and classifies them into four distinct catagories based on their involvement in the viral life cycle: virus attachment and entry, biosynthesis, nuclear import and export, and viral release.

Role of sodium taurocholate cotransporting polypeptide (NTCP) in HBV-induced hepatitis: Opportunities for developing novel therapeutics

Hepatitis B is an infectious disease caused by the HBV virus. It presents a significant challenge for treatment due to its chronic nature and the potential for developing severe complications, including hepatocirrhosis and hepatocellular carcinoma. These complications not only cause physical and psychological distress to patients but also impose substantial economic and social burdens on both individuals and society as a whole. The internalization of HBV relies on endocytosis and necessitates the involvement of various proteins, including heparin sulfate proteoglycans, epidermal growth factor receptors, and NTCP. Among these proteins, NTCP is pivotal in HBV internalization and is primarily located in the liver's basement membrane. As a transporter of bile acids, NTCP also serves as a receptor facilitating HBV entry into cells. Numerous molecules have been identified to thwart HBV infection by stifling NTCP activity, although only a handful exhibit low IC50 values. In this systematic review, our primary focus dwells on the structure and regulation of NTCP, as well as the mechanism involved in HBV internalization. We underscore recent drug breakthroughs that specifically target NTCP to combat HBV infection. By shedding light on these advances, this review contributes novel insights into developing effective anti-HBV medications.

From a Single Cell to a Whole Human Liver: Disease Modeling and Transplantation

Although the underlying cause may vary across countries and demographic groups, liver disease is a major cause of morbidity and mortality globally. Orthotopic liver transplantation is the only definitive treatment for liver failure but is limited by the lack of donor livers. The development of drugs that prevent the progression of liver disease and the generation of alternative liver constructs for transplantation could help alleviate the burden of liver disease. Bioengineered livers containing human induced pluripotent stem cell (iPSC)-derived liver cells are being utilized to study liver disease and to identify and test potential therapeutics. Moreover, bioengineered livers containing pig hepatocytes and endothelial cells have been shown to function and survive after transplantation into pig models of liver failure, providing preclinical evidence toward future clinical applications. Finally, bioengineered livers containing human iPSC-derived liver cells have been shown to function and survive after transplantation in rodents but require considerable optimization and testing prior to clinical use. In conclusion, bioengineered livers have emerged as a suitable tool for modeling liver diseases and as a promising alternative graft for clinical transplantation. The integration of novel technologies and techniques for the assembly and analysis of bioengineered livers will undoubtedly expand future applications in basic research and clinical transplantation.

Identification of potent inhibitors of SARS-CoV-2 infection by combined pharmacological evaluation and cellular network prioritization

Pharmacologically active compounds with known biological targets were evaluated for inhibition of SARS-CoV-2 infection in cell and tissue models to help identify potent classes of active small molecules and to better understand host-virus interactions. We evaluated 6,710 clinical and preclinical compounds targeting 2,183 host proteins by immunocytofluorescence-based screening to identify SARS-CoV-2 infection inhibitors. Computationally integrating relationships between small molecule structure, dose-response antiviral activity, host target, and cell interactome produced cellular networks important for infection. This analysis revealed 389 small molecules with micromolar to low nanomolar activities, representing >12 scaffold classes and 813 host targets. Representatives were evaluated for mechanism of action in stable and primary human cell models with SARS-CoV-2 variants and MERS-CoV. One promising candidate, obatoclax, significantly reduced SARS-CoV-2 viral lung load in mice. Ultimately, this work establishes a rigorous approach for future pharmacological and computational identification of host factor dependencies and treatments for viral diseases.

HepG2-NTCP Subclones Exhibiting High Susceptibility to Hepatitis B Virus Infection

HepG2 cells reconstituted with Hepatitis B virus (HBV) entry receptor sodium taurocholate co-transporting polypeptide (NTCP) are widely used as a convenient in vitro cell culture infection model for HBV replication studies. As such, it is pertinent that HBV infectivity is maintained at steady-state levels for an accurate interpretation of in vitro data. However, variations in the HBV infection efficiency due to imbalanced NTCP expression levels in the HepG2 cell line may affect experimental results. In this study, we performed single cell-cloning of HepG2-NTCP-A3 parental cells via limiting dilution and obtained multiple subclones with increased permissiveness to HBV. Specifically, one subclone (HepG2-NTCP-A3/C2) yielded more than four-fold higher HBV infection compared to the HepG2-NTCP-A3 parental clone. In addition, though HBV infectivity was universally reduced in the absence of polyethylene glycol (PEG), subclone C2 maintained relatively greater permissiveness under PEG-free conditions, suggesting the functional heterogeneity within parental HepG2-NTCP-A3 may be exploitable in developing a PEG-free HBV infection model. The increased viral production correlated with increased intracellular viral antigen expression as evidenced through HBcAg immunofluorescence staining. Further, these subclones were found to express different levels of NTCP, albeit with no remarkable morphology or cell growth differences. In conclusion, we isolated the subclones of HepG2-NTCP-A3 which support efficient HBV production and thus provide an improved in vitro HBV infection model.

Fungal Secondary Metabolite Exophillic Acid Selectively Inhibits the Entry of Hepatitis B and D Viruses

Current anti-hepatitis B virus (HBV) drugs are suppressive but not curative for HBV infection, so there is considerable demand for the development of new anti-HBV agents. In this study, we found that fungus-derived exophillic acid inhibits HBV infection with a 50% maximal inhibitory concentration (IC50) of 1.1 µM and a 50% cytotoxic concentration (CC50) of >30 µM in primary human hepatocytes. Exophillic acid inhibited preS1-mediated viral attachment to cells but did not affect intracellular HBV replication. Exophillic acid appears to target the host cells to reduce their susceptibility to viral attachment rather than acting on the viral particles. We found that exophillic acid interacted with the HBV receptor, sodium taurocholate cotransporting polypeptide (NTCP). Exophillic acid impaired the uptake of bile acid, the original function of NTCP. Consistent with our hypothesis that it affects NTCP, exophillic acid inhibited infection with HBV and hepatitis D virus (HDV), but not that of hepatitis C virus. Moreover, exophillic acid showed a pan-genotypic anti-HBV effect. We thus identified the anti-HBV/HDV activity of exophillic acid and revealed its mode of action. Exophillic acid is expected to be a potential new lead compound for the development of antiviral agents.

Analysis of the Physicochemical Properties, Replication and Pathophysiology of a Massively Glycosylated Hepatitis B Virus HBsAg Escape Mutant

Mutations in HBsAg, the surface antigen of the hepatitis B virus (HBV), might affect the serum HBV DNA level of HBV-infected patients, since the reverse transcriptase (RT) domain of HBV polymerase overlaps with the HBsAg-coding region. We previously identified a diagnostic escape mutant (W3S) HBV that produces massively glycosylated HBsAg. In this study, we constructed an HBV-producing vector that expresses W3S HBs (pHB-W3S) along with a wild-type HBV-producing plasmid (pHB-WT) in order to analyze the physicochemical properties, replication, and antiviral drug response of the mutant. Transfection of either pHB-WT or W3S into HepG2 cells yielded similar CsCl density profiles and eAg expression, as did transfection of a glycosylation defective mutant, pHB-W3S (N146G), in which a glycosylation site at the 146aa asparagine (N) site of HBs was mutated to glycine (G). Virion secretion, however, seemed to be severely impaired in cases of pHB-W3S and pHB-W3S (N146G), compared with pHB-WT, as determined by qPCR and Southern blot analysis. Furthermore, inhibition of glycosylation using tunicamycin^TM on wild-type HBV production also reduced the virion secretion. These results suggested that the HBV core and Dane particle could be formed either by massively glycosylated or glycosylation-defective HBsAg, but reduced and/or almost completely blocked the virion secretion efficiency, indicating that balanced glycosylation of HBsAg is required for efficient release of HBV, and mutations inducing an imbalanced glycosylation of HBs would cause the virion to become stuck in the cells, which might be associated with various pathogeneses due to HBV infection.

The enhancement role of Matrigel on HBV infection in HepG2-NTCP cells

The hepatoma cell lines stably expressing sodium taurocholate cotransporting polypeptide (NTCP), the receptor of hepatitis B virus (HBV) infection, serve as important infection models for studying viral biology and drug discovery. However, the efficiency of infection greatly varies. In this study, we studied the effects and potential mechanisms of Matrigel® hESC-qualified (M-hq), a biological basement membrane matrix commonly used in cell culture, on promotion HBV in vitro infection in HepG2-NTCP cells. For the first time, our findings demonstrate that M-hq could enhance the infection efficiency of cell culture-derived HBV with no impact on the cell viability, the HBV transcription and response to antiviral treatments. The infection enhancement is reproducible and is suggested to occur at HBV attachment step. Our study suggests that this novel system is applicable for studying HBV biology and new drugs.

Inhibitory effect of a novel thiazolidinedione derivative on hepatitis B virus entry

The development of novel antivirals to treat hepatitis B virus (HBV) infection is still needed because currently available drugs do not completely eradicate chronic HBV in some patients. Recently, troglitazone and ciglitazone, classified among the compounds including the thiazolidinedione (TZD) moiety, were found to inhibit HBV infection, but these compounds are not clinically available. In this study, we synthesized 11 TZD derivatives, compounds 1-11, and examined the effect of each compound on HBV infection in HepG2 cells expressing NTCP (HepG2/NTCP cells). Among the derivatives, (Z)-5-((4'-(naphthalen-1-yl)-[1,1'-biphenyl]-4-yl)methylene)thiazolidine-2,4-dione (compound 6) showed the highest antiviral activity, with an IC₅₀ value of 0.3 μM and a selectivity index (SI) of 85, but compound 6 did not affect HCV infection. Treatment with compound 6 inhibited HBV infection in primary human hepatocytes (PHHs) but did not inhibit viral replication in HepG2.2.15 cells or HBV DNA-transfected Huh7 cells. Moreover, treatment with compound 6 significantly impaired hepatitis delta virus (HDV) infection and inhibited a step in HBV particle internalization but did not inhibit attachment of the preS1 lipopeptide or viral particles to the cell surface. These findings suggest that compound 6 interferes with HBV infection via inhibition of the internalization process.

Strategy, Progress, and Challenges of Drug Repurposing for Efficient Antiviral Discovery

Emerging or re-emerging viruses are still major threats to public health. Prophylactic vaccines represent the most effective way to prevent virus infection; however, antivirals are more promising for those viruses against which vaccines are not effective enough or contemporarily unavailable. Because of the slow pace of novel antiviral discovery, the high disuse rates, and the substantial cost, repurposing of the well-characterized therapeutics, either approved or under investigation, is becoming an attractive strategy to identify the new directions to treat virus infections. In this review, we described recent progress in identifying broad-spectrum antivirals through drug repurposing. We defined the two major categories of the repurposed antivirals, direct-acting repurposed antivirals (DARA) and host-targeting repurposed antivirals (HTRA). Under each category, we summarized repurposed antivirals with potential broad-spectrum activity against a variety of viruses and discussed the possible mechanisms of action. Finally, we proposed the potential investigative directions of drug repurposing.

Design of Dimeric Bile Acid Derivatives as Potent and Selective Human NTCP Inhibitors

Dimeric bile acid derivatives (DBADs) were developed and tested for their anti-HBV and anti-HDV activities as sodium taurocholate cotransporting polypeptide (NTCP) inhibitors. DBADs exhibited strong and persistent potency of NTCP inhibition, whereas diverse linkers and constitutions showed distinct inhibition features. Motif aa157-165 on NTCP was shown to be a possible binding site of DBADs; therefore, we determined DBADs' selectivity among NTCPs from different species. A cyclized DBAD scaffold DBA-41 exhibited a high affinity to human NTCP (hNTCP). Intraperitoneal administration of DBA-41 to hNTCP-tg mice induced serum total bile acid elevation. DBA-41 may serve as a biological tool to study NTCP physiological function.

Multidose evaluation of 6,710 drug repurposing library identifies potent SARS-CoV-2 infection inhibitors In Vitro and In Vivo

The SARS-CoV-2 pandemic has caused widespread illness, loss of life, and socioeconomic disruption that is unlikely to resolve until vaccines are widely adopted, and effective therapeutic treatments become established. Here, a well curated and annotated library of 6710 clinical and preclinical molecules, covering diverse chemical scaffolds and known host targets was evaluated for inhibition of SARS-CoV-2 infection in multiple infection models. Multi-concentration, high-content immunocytofluorescence-based screening identified 172 strongly active small molecules, including 52 with submicromolar potencies. The active molecules were extensively triaged by in vitro mechanistic assays, including human primary cell models of infection and the most promising, obatoclax, was tested for in vivo efficacy. Structural and mechanistic classification of compounds revealed known and novel chemotypes and potential host targets involved in each step of the virus replication cycle including BET proteins, microtubule function, mTOR, ER kinases, protein synthesis and ion channel function. In the mouse disease model obatoclax effectively reduced lung virus load by 10-fold. Overall, this work provides an important, publicly accessible, foundation for development of novel treatments for COVID-19, establishes human primary cell-based pharmacological models for evaluation of therapeutics and identifies new insights into SARS-CoV-2 infection mechanisms.

Significance

A bioinformatically rich library of pharmacologically active small molecules with diverse chemical scaffolds and including known host targets were used to identify hundreds of SARS-CoV-2 replication inhibitors using in vitro, ex vivo, and in vivo models. Extending our previous work, unbiased screening demonstrated a propensity for compounds targeting host proteins that interact with virus proteins. Representatives from multiple chemical classes revealed differences in cell susceptibility, suggesting distinct dependencies on host factors and one, Obatoclax, showed 90% reduction of lung virus loads in the mouse disease model. Our findings and integrated analytical approaches will have important implications for future drug screening and how therapies are developed against SARS-CoV-2 and other viruses.

Establishment of a Cell Culture Model Permissive for Infection by Hepatitis B and C Viruses

Compared with each monoinfection, coinfection with hepatitis B virus (HBV) and hepatitis C virus (HCV) is well known to increase the risks of developing liver cirrhosis and hepatocellular carcinoma. However, the mechanism by which HBV/HCV coinfection is established in hepatocytes is not well understood. Common cell culture models for coinfection are required to examine viral propagation. In this study, we aimed to establish a cell line permissive for both HBV and HCV infection. We first prepared a HepG2 cell line expressing sodium taurocholate cotransporting polypeptide, an HBV receptor, and then selected a cell line highly permissive for HBV infection, G2/NT18-B. After transduction with a lentivirus-encoding microRNA-122, the cell line harboring the highest level of replicon RNA was selected and then treated with anti-HCV compounds to eliminate the replicon RNA. The resulting cured cell line was transduced with a plasmid-encoding CD81. The cell line permissive for HCV infection was cloned and then designated the G2BC-C2 cell line, which exhibited permissiveness for HBV and HCV propagation. JAK inhibitor I potentiated the HCV superinfection of HBV-infected cells, and fluorescence-activated cell-sorting analysis indicated that HBV/HCV double-positive cells accounted for approximately 30% of the coinfected cells. Among several host genes tested, cyclooxygenase-2 showed synergistic induction by coinfection compared with each monoinfection. Conclusion: These data indicate that our in vitro HBV/HCV coinfection system provides an easy-to-use platform for the study of host and viral responses against coinfection and the development of antiviral agents targeting HBV and HCV.

Thiol-ene enabled preparation of S-lipidated anti-HBV peptides

Despite significant efforts made towards treatments for Hepatitis B virus (HBV), a long-term curative treatment has thus far eluded scientists. Recently, the Sodium Taurocholate Co-Transporting Polypeptide (NTCP) receptor has been identified as the entry pathway of HBV into hepatocytes. Myrcludex B, an N-terminally myristoylated 47-mer peptide mimic of the preS1 domain of the Hepatitis B virion, was identified as a potent protein-protein interaction (PPI) inhibitor blocking HBV fusion (IC50 = 140 pM). Herein we report an optimised chemical synthesis of Myrcludex B and a series of novel analogues. Employing a small modification to the Cysteine Lipidation of a Peptide or Amino acid (CLipPA) thiol-ene reaction, a library of S-lipidated Myrcludex B and truncated (21-mer) analogues were prepared, providing novel chemical space to probe for the discovery of novel anti-HBV peptides. The S-lipidated analogues showed an equivalent or a slight decrease (∼2-fold) in binding effectiveness to NTCP expressing hepatocytes compared to Myrcludex B. Three S-lipidated analogues were highly potent HBV inhibitors (IC50 0.97-3.32 nM). These results demonstrate that incorporation of heteroatoms into the lipid 'anchor' is tolerated by this antiviral scaffold and to the best of our knowledge constitutes the first report of potent S-lipidated antiviral peptides. Interestingly, despite only moderate reductions in binding effectiveness, truncated analogues possessed dramatically reduced inhibitory activity thus providing new insights into the structure activity relationship of these hitherto unreported antiviral S-lipopeptides.

Establishment of a novel hepatitis B virus culture system using immortalized human hepatocytes

Recent development of hepatitis B virus (HBV) culture systems has made it possible to analyze the almost all steps of the viral life cycle. However, the reproducibility of interaction between HBV and host cells seemed inaccurate in those systems because of utilization of cancer cell lines with a difference from hepatocytes in the majority of cases. In this study, in order to resolve this point, a novel HBV culture system using non-cancer-derived immortalized human hepatocytes derived cell lines, producing exogenous human sodium taurocholate cotransporting polypeptide, was developed. One of the cell clones, E/NtG8 cells, was permissive to both blood-borne HBV (HBVbb) and culture-derived recombinant HBV when cultured in the three-dimensional condition. Furthermore, the production of infectious HBV particles, which showed the similar physicochemical properties to HBVbb, was observed for about a month after HBVbb infection in this system, suggesting that it may reproduce whole steps of the HBV lifecycle under the condition analogous to human liver cells infected with HBV. This system seemed to contribute not only to find novel interactions between HBV and host cells but also to understand mechanism of HBV pathogenesis.

ADAR1 Stimulation by IFN-α Downregulates the Expression of MAVS via RNA Editing to Regulate the Anti-HBV Response

The partial response of chronic hepatitis B virus (CHB) patients to interferon-α (IFN-α) therapy remains elusive, which requires a better understanding of the involved molecular mechanism. In our study, bioinformatics analysis was applied to relate IFN-α regulated candidate genes and RNA editing sites by RNA sequencing. Mitochondrial antiviral signaling protein (MAVS) antiviral effect was confirmed in HepG2.2.15 cells and in two mouse models. The associations between polymorphisms in MAVS gene and response to IFN-α therapy were confirmed in CHB patients. We found that IFN-α downregulates MAVS via RNA editing that was mediated by adenosine deaminase acting on RNA (ADAR1). ADAR1 inhibited MAVS expression via a human antigen R (HuR)-mediated post-transcriptional regulation. MAVS exerted an antiviral activity and reduced the level of hepatitis B virus (HBV) markers in vitro and in vivo. IFN-α antiviral effects were significantly enhanced by MAVS co-transfection. Hepatitis B core protein (HBc) interacted with SP1 to inhibit the promoter activity of MAVS that regulates its expression. CHB patients with a rs3746662A allele had higher MAVS expression and thus were more responsive to IFN-α treatment. In this work, we demonstrated that the decrease of MAVS expression is mediated by the IFN-α-ADAR1 axis. This study also highlighted the potential for the clinical application of MAVS in combination with IFN-α for the treatment of HBV infection.

Transglycosylation toward naringenin-7-O-glucoside using an N180H mutant of Coprinopsis cinerea endo-β-N-acetylglucosaminidase

Flavonoids are generally glycosylated, and the glycan moieties of flavonoid glycosides are known to greatly affect their physicochemical and biological properties. Thus, the development of a variety of tools for glycan remodeling of flavonoid glycosides is highly desired. An endo-β-N-acetylglucosaminidase mutant Endo-CC N180H, which is developed as an excellent chemoenzymatic tool for creating sialylglycoproteins, was employed for the glycosylation of flavonoids. Endo-CC N180H transferred the sialyl biantennary glycans from the sialylglyco peptide to pNP-GlcNAc and narigenin-7-O-glucoside. The kinetic parameters of Endo-CC N180H towards SGP and pNP-GlcNAc were determined. Flavonoid glucosides harboring a 1,3-diol structure in the glucose moieties acted as substrates of Endo-CC N180H. We proposed that the sialyl biantennary glycan transfer to the flavonoid by Endo-CC N180H could pave the way for the improvement of the inherent biological functions of the flavonoids and creation of novel flavonoid glycoside derivatives for future human health benefits including foods and drugs.

A systematic review on use of aminoquinolines for the therapeutic management of COVID-19: Efficacy, safety and clinical trials

Recent global outbreak of the pandemic caused by coronavirus (COVID-19) emphasizes the urgent need for novel antiviral therapeutics. It can be supplemented by utilization of efficient and validated drug discovery approaches such as drug repurposing/repositioning. The well reported and clinically used anti-malarial aminoquinoline drugs (chloroquine and hydroxychloroquine) have shown potential to be repurposed to control the present pandemic by inhibition of COVID-19. The review elaborates the mechanism of action, safety (side effects, adverse effects, toxicity) and details of clinical trials for chloroquine and hydroxychloroquine to benefit the clinicians, medicinal chemist, pharmacologist actively involved in controlling the pandemic and to provide therapeutics for the treatment of COVID-19 infection.

Hepatitis C virus infection suppresses hepatitis B virus replication via the RIG-I-like helicase pathway

Mechanisms of hepatitis B virus (HBV) reactivation after hepatitis C virus (HCV) elimination by direct-acting antiviral (DAA) treatment in HBV/HCV-co-infected patients remain unclear. We examined RIG-I-like helicase (RLH) pathway activation by HBV mono-infection, HCV mono-infection or HBV/HCV co-infection and interference between HBV and HCV in primary human hepatocytes. Interference between HBV and HCV and HBV reactivation after DAA treatment in humanized-liver mice were assessed. HCV infection activated RLH pathway, as evidenced by RIG-I, ISG15 and ISG56 expression induction; HBV caused only RIG-I induction in vitro. RLH activation was also found in HBV/HCV-co-infected cells, and HBV replication were suppressed in HBV/HCV-co-infected than in HBV-mono-infected cells. siRNA-mediated double knockdown of ISG15 and ISG56 increased HBV replication in HBV/HCV-co-infected cells. HCV infection activated RLH pathway and suppressed HBV replication in humanized-liver mice. Subsequent elimination of HCV by DAA administration downregulated RLH pathway and upregulated HBV replication in mice. RLH pathway was activated in livers of chronic hepatitis C patients compared to those of chronic hepatitis B or non-B, non-C patients. The RLH pathway activation was downregulated by HCV elimination. In conclusion, HCV infection activated RLH pathway and suppressed HBV replication in human hepatocytes. HCV elimination upregulated HBV replication, probably through RLH pathway downregulation.

The MOV10 helicase restricts hepatitis B virus replication by inhibiting viral reverse transcription

Interferons inhibit viruses by inducing antiviral protein expression. One of the interferon-induced antiviral proteins, human Moloney leukemia virus 10 (MOV10), a superfamily 1 RNA helicase, has been shown to inhibit retroviruses and several RNA viruses. However, it remains undetermined whether MOV10 also inhibits DNA viruses, including hepatitis B virus (HBV). Here, we report that MOV10 dramatically reduces the levels of intracellular HBV DNA, resulting in significant inhibition of both the HBV experimental strain and the clinical isolates. Mechanistic experiments revealed that MOV10 interacts with HBV RNA and blocks the early step of viral reverse transcription, thereby impairing viral DNA synthesis, without affecting viral gene expression and pregenomic RNA encapsidation. Moreover, mutation of the helicase domain of MOV10 caused loss of binding to HBV RNA and of the anti-HBV activity. Together, our results indicate that MOV10 restricts HBV replication, insights that may open new avenues to the development of anti-HBV therapeutics.

Bardoxolone methyl as a novel potent antiviral agent against hepatitis B and C viruses in human hepatocyte cell culture systems

Antiviral drugs against hepatitis B virus (HBV) relieve symptoms experienced by patients with hepatitis; however, these drugs cannot eliminate HBV infection from all patients completely. On the other hand, direct antiviral agents (DAAs) against hepatitis C virus (HCV) can achieve near-complete elimination of HCV infection. However, recent reports have claimed that DAAs pose a risk for HBV reactivation among patients with HBV and HCV co-infection. This suggests that an effective anti-viral strategy for both HBV and HCV would be extremely useful. We hypothesized that an activator of nuclear factor-erythroid factor 2 (Nrf2) could be a candidate, because heme oxygenase-1 (HO-1), a product of the Nrf2-target gene, was shown to be related to suppression of genome replication in both HBV and HCV. In this study, the potential of bardoxolone methyl (BARD), an Nrf2 activator, was examined in cell culture systems against HBV and HCV. We investigated that BARD had a suppressive effect on the production of extracellular HBV DNA in several HBV culture systems. In addition, BARD treatment reduced the levels of intracellular HBV pregenome RNA (pgRNA), a transcript from the HBV genome and a template of HBV genome replication. HCV genome replication was also suppressed in HCV subgenomic replicon-bearing cells by BARD treatment. BARD might be a novel treatment for patients with HBV and HCV co-infection.

Hepatic spheroids used as an in vitro model to study malaria relapse

Hypnozoites are the liver stage non-dividing form of the malaria parasite that are responsible for relapse and acts as a natural reservoir for human malaria Plasmodium vivax and P. ovale as well as a phylogenetically related simian malaria P. cynomolgi. Our understanding of hypnozoite biology remains limited due to the technical challenge of requiring the use of primary hepatocytes and the lack of robust and predictive in vitro models. In this study, we developed a malaria liver stage model using 3D spheroid-cultured primary hepatocytes. The infection of primary hepatocytes in suspension led to increased infectivity of both P. cynomolgi and P. vivax infections. We demonstrated that this hepatic spheroid model was capable of maintaining long term viability, hepatocyte specific functions and cell polarity which enhanced permissiveness and thus, permitting for the complete development of both P. cynomolgi and P. vivax liver stage parasites in the infected spheroids. The model described here was able to capture the full liver stage cycle starting with sporozoites and ending in the release of hepatic merozoites capable of invading simian erythrocytes in vitro. Finally, we showed that this system can be used for compound screening to discriminate between causal prophylactic and cidal antimalarials activity in vitro for relapsing malaria.

Drug repurposing for new, efficient, broad spectrum antivirals

Emerging viruses are a major threat to human health. Recent outbreaks have emphasized the urgent need for new antiviral treatments. For several pathogenic viruses, considerable efforts have focused on vaccine development. However, during epidemics infected individuals need to be treated urgently. High-throughput screening of clinically tested compounds provides a rapid means to identify undiscovered, antiviral functions for well-characterized therapeutics. Repurposed drugs can bypass part of the early cost and time needed for validation and authorization. In this review we describe recent efforts to find broad spectrum antivirals through drug repurposing. We have chosen several candidates and propose strategies to understand their mechanism of action and to determine how resistance to antivirals develops in infected cells.

A Bimolecular Multicellular Complementation System for the Detection of Syncytium Formation: A New Methodology for the Identification of Nipah Virus Entry Inhibitors

Fusion of viral and cellular membranes is a key step during the viral life cycle. Enveloped viruses trigger this process by means of specialized viral proteins expressed on their surface, the so-called viral fusion proteins. There are multiple assays to analyze the viral entry including those that focus on the cell-cell fusion induced by some viral proteins. These methods often rely on the identification of multinucleated cells (syncytium) as a result of cell membrane fusions. In this manuscript, we describe a novel methodology for the study of cell-cell fusion. Our approach, named Bimolecular Multicellular Complementation (BiMuC), provides an adjustable platform to qualitatively and quantitatively investigate the formation of a syncytium. Furthermore, we demonstrated that our procedure meets the requirements of a drug discovery approach and performed a proof of concept small molecule high-throughput screening to identify compounds that could block the entry of the emerging Nipah virus.

Cell and Animal Models for Studying Hepatitis B Virus Infection and Drug Development

Many cell culture and animal models have been used to study hepatitis B virus (HBV) replication and its effects in the liver; these have facilitated development of strategies to control and clear chronic HBV infection. We discuss the advantages and limitations of systems for studying HBV and developing antiviral agents, along with recent advances. New and improved model systems are needed. Cell culture systems should be convenient, support efficient HBV infection, and reproduce responses of hepatocytes in the human body. We also need animals that are fully permissive to HBV infection, convenient for study, and recapitulate human immune responses to HBV and effects in the liver. High-throughput screening technologies could facilitate drug development based on findings from cell and animal models.

The susceptibility of human hepatoma-derived oval-like cells to hepatitis B virus infection

Human hepatocytes are a primary site of infection and replication of the hepatitis B virus (HBV). It is tempting to conclude that tissue specificity is controlled via virus-hepatocyte specific interactions at various steps during the viral lifecycle. However, the molecular mechanisms underlying hepatotropism of HBV are not fully clear. To address this issue, this study aims to identify hepatic factors that contribute to the regulation of the lifecycles of hepatitis viruses- especially HBV- and to clarify their regulatory mechanisms. We established oval-like cell lines (Hdo cells) by introducing a set of reprogramming factors (OCT3/4, SOX2, KLF4, LIN28, and NANOG) into human hepatoma HuH7 cells that are susceptible to HBV. Hdo cells exhibit a bi-directional differentiation potential. We found that Hdo cells maintained support for the replication of HBV but not of HCV. The level of particle-associated HBV DNA secreted into the culture medium was higher in the Hdo cells. Still, the HBs antigen level was lower than in parental HuH7 cells, suggesting that the regulation of HBV gene expression was affected by the reprogramming of HuH7 cells. A microarray analysis determined that the expression of host factors was largely comparable among of HuH7 and Hdo cells. In contrast, Hdo cells lost their susceptibility to HCV infection and to replication of the viral subgenome replicon RNA. Our results suggest that epigenetic reprogramming of human hepatoma cells potentially changes their permissivity to HBV. Furthermore, Hdo cells can be used as powerful tools to identify cellular determinants that change their expression during reprogramming or hepatic differentiation.

N-Linked Glycosylation Is Not Essential for Sodium Taurocholate Cotransporting Polypeptide To Mediate Hepatitis B Virus Infection In Vitro

Sodium taurocholate cotransporting polypeptide (NTCP) has been identified as a hepatitis B virus (HBV) receptor, and its overexpression in HepG2 cell lines leads to efficient secretion of hepatitis B e antigen (HBeAg) following challenge with a large dose of cell culture-derived HBV (cHBV) particles. However, NTCP-reconstituted HepG2 cells are inefficiently infected by patient serum-derived HBV (sHBV) and release very little hepatitis B surface antigen (HBsAg) following cHBV infection, unlike differentiated HepaRG cells, which are naturally susceptible to both cHBV and sHBV particles. Here, we investigated whether NTCP could explain the different behaviors of the two cell types. Endogenous NTCP protein from differentiated HepaRG cells was unglycosylated despite wild-type coding sequence. HepaRG cells stably transfected with an epitope-tagged NTCP expression construct displayed higher sHBV but not cHBV susceptibility than cells transfected with the null mutant. Tagged NTCP introduced to both HepG2 and HepaRG cells was glycosylated, with N5 and N11 being sites of N-linked glycosylation. Mutating N5, N11, or both did not alter cell surface availability of NTCP or its subcellular localization, with both the singly glycosylated and nonglycosylated forms still capable of mediating cHBV infection in HepG2 cells. In conclusion, nonglycosylated NTCP is expressed by differentiated HepaRG cells and capable of mediating cHBV infection in HepG2 cells, but it cannot explain differential susceptibility of HepaRG and HepG2/NTCP cells to cHBV versus sHBV infection and different HBsAg/HBeAg ratios following cHBV infection. The responsible host factor(s) remains to be identified.IMPORTANCE HBV can infect differentiated HepaRG cells and also HepG2 cells overexpressing NTCP, the currently accepted HBV receptor. However, HepG2/NTCP cells remain poorly susceptible to patient serum-derived HBV particles and release very little hepatitis B surface antigen following infection by cell culture-derived HBV. We found differentiated HepaRG cells expressed nonglycosylated NTCP despite a wild-type coding sequence. NTCP introduced to HepG2 cells was glycosylated at two N-linked glycosylation sites, but mutating either or both sites failed to prevent infection by cell culture-derived HBV or to confer susceptibility to serum-derived HBV. Overexpressing NTCP in HepRG cells did not increase infection by cell culture-derived HBV or distort the ratio between the two viral antigens. These findings suggest that host factors unique to HepaRG cells are required for efficient infection by serum-derived HBV, and factors other than NTCP contribute to balanced viral antigen production following infection by cell culture-derived HBV.

Screening of microRNAs for a repressor of hepatitis B virus replication

BACKGROUND

Hepatitis B virus (HBV) infection is a leading cause of persistent liver diseases, cirrhosis and hepatocellular carcinoma (HCC) worldwide. Since deregulation of microRNA (miRNA) expression by HBV infection contributes to enhanced viral replication and pathogenesis, modulation of miRNA activity can be a novel therapeutic approach towards HBV eradication. As the effects of the vast majority of miRNAs on HBV replication have not been empirically investigated, here, we aim to identify novel therapeutic targets that have a strong antiviral effect on HBV.

METHODS

HepG2-hNTCP-C4 cells were infected with HBV, and then were individually transfected with the library mimics of 2048 miRNAs. To assess the amount of intracellular and extracellular DNA and HBsAg, qPCR and ELISA were performed respectively.

RESULTS

From miRNA library screening, we identified 39 miRNAs as candidate repressors of HBV replication. Among them, 9 miRNAs, including miR-204, strongly decreased both HBV DNA and HBsAg in culture supernatant of HepG2-hNTCP-C4 cells. Furthermore, we also showed that inhibition of Rab22a, one of the targets of miR-204, also suppressed intracellular and extracellular HBV DNA expression in HepG2.2.15.7 cells.

CONCLUSIONS

Our findings contribute to the understanding of the roles of miRNAs underlying HBV replication and show the possibility of developing a novel strategy for miRNA-mediated HBV treatment.

Association of the S267F variant on NTCP gene and treatment response to pegylated interferon in patients with chronic hepatitis B: a multicentre study

BACKGROUND

Sodium taurocholate co-transporting polypeptide (NTCP) is a cell receptor for HBV. The S267F variant on the NTCP gene is inversely associated with the chronicity of HBV infection, progression to cirrhosis and hepatocellular carcinoma in East Asian populations. The aim of this study was to determine whether the S267F variant was associated with response to pegylated interferon (PEG-IFN) in patients with chronic HBV infection.

METHODS

A total of 257 patients with chronic HBV, treated with PEG-IFN for 48 weeks, were identified from 13 tertiary hospitals included in the hepatitis B database of the Thai Association for the Study of the Liver (THASL).

RESULTS

Of these, 202 patients were infected with HBV genotype C (84.9%); 146 patients were hepatitis B e antigen (HBeAg)-positive (56.8%). Genotypic frequencies of the S267F polymorphism were 85.2%, 14.8% and 0% for the GG, GA and AA genotypes, respectively. S267F GA was associated with sustained alanine aminotransferase (ALT) normalization (OR = 3.25, 95% CI 1.23, 8.61; P=0.02) in HBeAg-positive patients. Patients with S267F variant tended to have more virological response, sustained response with hepatitis B surface antigen (HBsAg) loss at 24 weeks following PEG-IFN treatment. There was no association between the S267F variant and improved patient outcomes in HBeAg-negative patients.

CONCLUSIONS

The S267F variant on the NTCP gene is independently associated with sustained normalization of ALT following treatment with PEG-IFN in patients with HBV infection who are HBeAg-positive. The findings of this study provide additional support for the clinical significance of the S267F variant of NTCP beyond HBV entry.

Novel insights into bat influenza A viruses

In 2012 and 2013, influenza virus genome sequences of two new influenza A virus (IAV) subtypes were discovered in bat specimens, but further characterization was largely impeded by the lack of infectious virus. With the identification of highly susceptible cell lines, reconstitution of infectious bat IAV by reverse genetics recently succeeded and allowed a first insight into the life cycle of these viruses. Although there is a certain degree of functional compatibility between bat and conventional influenza A virus proteins, there are striking differences, including receptor usage, polarity of infection and reassortment potential.

Hepatitis B virus prevents excessive viral production via reduction of cell death-inducing DFF45-like effectors

The relationship between hepatitis B virus (HBV) infection and lipid accumulation remains largely unknown. In this study, we investigated the effect of HBV propagation on lipid droplet growth in HBV-infected cells and HBV-producing cell lines, HepG2.2.15 and HBV-inducible Hep38.7-Tet. The amount of intracellular triglycerides was significantly reduced in HBV-infected and HBV-producing cells compared with HBV-lacking control cells. Electron and immunofluorescent microscopic analyses showed that the average size of a single lipid droplet (LD) was significantly less in the HBV-infected and HBV-producing cells than in the HBV-lacking control cells. Cell death-inducing DFF45-like effectors (CIDEs) B and C (CIDEB and CIDEC), which are involved in LD expansion for the improvement of lipid storage, were expressed at a significantly lower level in HBV-infected or HBV-producing cells than in HBV-lacking control cells, while CIDEA was not detected in those cells regardless of HBV production. The activity of the CIDEB and CIDEC gene promoters was impaired in HBV-infected or HBV-producing cells compared to HBV-lacking control cells, while CIDEs potentiated HBV core promoter activity. The amount of HNF4α, that can promote the transcription of CIDEB was significantly lower in HBV-producing cells than in HBV-lacking control cells. Knockout of CIDEB or CIDEC significantly reduced the amount of supernatant HBV DNA, intracellular viral RNA and nucleocapsid-associated viral DNA, while the expression of CIDEB or CIDEC recovered HBV production in CIDEB- or CIDEC-knockout cells. These results suggest that HBV regulates its own viral replication via CIDEB and CIDEC.

Cholesterol attenuates cytoprotective effects of phosphatidylcholine against bile salts

Bile salts have potent detergent properties and damaging effects on cell membranes, leading to liver injury. However, the molecular mechanisms for the protection of hepatocytes against bile salts are not fully understood. In this study, we demonstrated that the cytotoxicity of nine human major bile salts to HepG2 cells and primary human hepatocytes was prevented by phosphatidylcholine (PC). In contrast, cholesterol had no direct cytotoxic effects but suppressed the cytoprotective effects of PC. PC reduced the cell-association of bile salt, which was reversed by cholesterol. Light scattering measurements and gel filtration chromatography revealed that cholesterol within bile salt/PC dispersions decreased mixed micelles but increased vesicles, bile salt simple micelles and monomers. These results suggest that cholesterol attenuates the cytoprotective effects of PC against bile salts by facilitating the formation of bile salt simple micelles and monomers. Therefore, biliary PC and cholesterol may play different roles in the pathogenesis of bile salt-induced liver injury.

Establishment of a human hepatocellular cell line capable of maintaining long-term replication of hepatitis B virus

Hepatitis B virus (HBV) is a virus whose replication cycle cannot be completely reproduced using cultured cell lines. Here, we report an engineered cell line capable of supporting the complete HBV life cycle. We generated HepG2 cells over-expressing the HBV entry receptor human NTCP (sodium taurocholate cotransporting polypeptide), and defective in RIG-I (retinoic acid-inducible gene-I)-like receptor signaling, by knocking down the IPS-1 (IFNβ-promoter stimulator-1) adaptor molecule. The resultant NtG20.i7 cells were susceptible to HBV, and its replication was detectable at 14 days post-infection and persisted for at least 35 days with a gradual increase of HBV core expression. The cells produced infectious HBV in the culture supernatant, and the addition of preS1 peptide myr47-WT, which blocks HBV entry, impaired the persistence of the infection. These findings suggest that the persistence of the infection was maintained by continuous release of infectious HBV virions and their re-infection. This system is useful for expanding our basic understanding of the HBV replication cycle and for screening of anti-HBV chemicals.

Synthetically derived bat influenza A-like viruses reveal a cell type- but not species-specific tropism

Two novel influenza A-like viral genome sequences have recently been identified in Central and South American fruit bats and provisionally designated "HL17NL10" and "HL18NL11." All efforts to isolate infectious virus from bats or to generate these viruses by reverse genetics have failed to date. Recombinant vesicular stomatitis virus (VSV) encoding the hemagglutinin-like envelope glycoproteins HL17 or HL18 in place of the VSV glycoprotein were generated to identify cell lines that are susceptible to bat influenza A-like virus entry. More than 30 cell lines derived from various species were screened but only a few cell lines were found to be susceptible, including Madin-Darby canine kidney type II (MDCK II) cells. The identification of cell lines susceptible to VSV chimeras allowed us to recover recombinant HL17NL10 and HL18NL11 viruses from synthetic DNA. Both influenza A-like viruses established a productive infection in MDCK II cells; however, HL18NL11 replicated more efficiently than HL17NL10 in this cell line. Unlike conventional influenza A viruses, bat influenza A-like viruses started the infection preferentially at the basolateral membrane of polarized MDCK II cells; however, similar to conventional influenza A viruses, bat influenza A-like viruses were released primarily from the apical site. The ability of HL18NL11 or HL17NL10 viruses to infect canine and human cells might reflect a zoonotic potential of these recently identified bat viruses.

Inhibitory effect of CDK9 inhibitor FIT-039 on hepatitis B virus propagation

Current therapies for hepatitis B virus (HBV) cannot completely eliminate the HBV genome because of the stable population of covalently closed circular DNA (cccDNA) and so on. FIT-039, which is a cyclin-dependent kinase (CDK) 9 inhibitor, is known to suppress the replication of several DNA viruses including HSV, HPV and human adenovirus. In this study, we investigated the antiviral effect of FIT-039 on HBV infection. HepG2 cells expressing human sodium taurocholate cotransporting polypeptide (HepG2/NTCP cells) were infected with HBV in the presence of FIT-039. FIT-039 dose-dependently reduced intracellular viral RNA, nucleocapsid-associated viral DNA, and supernatant viral antigens without cytotoxicity in the infected cells (IC50 = 0.33 μM, CC50 > 50 μM). The antiviral activity of FIT-039 was prominent at an early phase of viral infection, although the compound did not inhibit preS1-binding to HepG2/NTCP cells. FIT-039 reduced cccDNA in HBV-replicating or HBV-infected cells. Furthermore, the antiviral activity of entecavir was significantly enhanced by the combination with FIT-039 in the chimeric mice having human hepatocytes infected with HBV. None of the mice had significant drug-related body weight or serum human-albumin concentration changes. These data suggest that CDK9 inhibitor FIT-039 is a promising antiviral candidate for HBV infection.

Cellular uptake of hepatitis B virus envelope L particles is independent of sodium taurocholate cotransporting polypeptide, but dependent on heparan sulfate proteoglycan

Sodium taurocholate cotransporting polypeptide (NTCP) was recently discovered as a hepatitis B virus (HBV) receptor, however, the detailed mechanism of HBV entry is not yet fully understood. We investigated the cellular entry pathway of HBV using recombinant HBV surface antigen L protein particles (bio-nanocapsules, BNCs). After the modification of L protein in BNCs with myristoyl group, myristoylated BNCs (Myr-BNCs) were found to bind to NTCP in vitro, and inhibit in vitro HBV infection competitively, suggesting that Myr-BNCs share NTCP-dependent infection machinery with HBV. Nevertheless, the cellular entry rates of Myr-BNCs and plasma-derived HBV surface antigen (HBsAg) particles were the same as those of BNCs in NTCP-overexpressing HepG2 cells. Moreover, the cellular entry of these particles was mainly driven by heparan sulfate proteoglycan-mediated endocytosis regardless of NTCP expression. Taken together, cell-surface NTCP may not be involved in the cellular uptake of HBV, while presumably intracellular NTCP plays a critical role.

Human induced pluripotent stem cell-derived hepatic cell lines as a new model for host interaction with hepatitis B virus

Hepatitis B virus (HBV) is not eradicated by current antiviral therapies due to persistence of HBV covalently closed circular DNA (cccDNA) in host cells, and thus development of novel culture models for productive HBV infection is urgently needed, which will allow the study of HBV cccDNA eradication. To meet this need, we developed culture models of HBV infection using human induced pluripotent stem cell-derived hepatocyte lineages, including immature proliferating hepatic progenitor-like cell lines (iPS-HPCs) and differentiated hepatocyte-like cells (iPS-Heps). These cells were susceptible to HBV infection, produced HBV particles, and maintained innate immune responses. The infection efficiency of HBV in iPS-HPCs predominantly depended on the expression levels of sodium taurocholate cotransporting polypeptide (NTCP), and was low relative to iPS-Heps: however, long-term culture of iPS-Heps was difficult. To provide a model for HBV persistence, iPS-HPCs overexpressing NTCP were established. The long-term persistence of HBV cccDNA was detected in iPS-HPCs overexpressing NTCP, and depended on the inhibition of the Janus-kinase signaling pathway. In conclusion, this study provides evidence that iPS-derived hepatic cell lines can be utilized for novel HBV culture models with genetic variation to investigate the interactions between HBV and host cells and the development of anti-HBV strategies.

Hepatocyte Factor JMJD5 Regulates Hepatitis B Virus Replication through Interaction with HBx

Hepatitis B virus (HBV) is a causative agent for chronic liver diseases such as hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). HBx protein encoded by the HBV genome plays crucial roles not only in pathogenesis but also in replication of HBV. Although HBx has been shown to bind to a number of host proteins, the molecular mechanisms by which HBx regulates HBV replication are largely unknown. In this study, we identified jumonji C-domain-containing 5 (JMJD5) as a novel binding partner of HBx interacting in the cytoplasm. DNA microarray analysis revealed that JMJD5-knockout (JMJD5KO) Huh7 cells exhibited a significant reduction in the expression of transcriptional factors involved in hepatocyte differentiation, such as HNF4A, CEBPA, and FOXA3. We found that hydroxylase activity of JMJD5 participates in the regulation of these transcriptional factors. Moreover, JMJD5KO Huh7 cells exhibited a severe reduction in HBV replication, and complementation of HBx expression failed to rescue replication of a mutant HBV deficient in HBx, suggesting that JMJD5 participates in HBV replication through an interaction with HBx. We also found that replacing Gly(135) with Glu in JMJD5 abrogates binding with HBx and replication of HBV. Moreover, the hydroxylase activity of JMJD5 was crucial for HBV replication. Collectively, these results suggest that direct interaction of JMJD5 with HBx facilitates HBV replication through the hydroxylase activity of JMJD5.

IMPORTANCE

HBx protein encoded by hepatitis B virus (HBV) plays important roles in pathogenesis and replication of HBV. We identified jumonji C-domain-containing 5 (JMJD5) as a novel binding partner to HBx. JMJD5 was shown to regulate several transcriptional factors to maintain hepatocyte function. Although HBx had been shown to support HBV replication, deficiency of JMJD5 abolished contribution of HBx in HBV replication, suggesting that HBx-mediated HBV replication is largely dependent on JMJD5. We showed that hydroxylase activity of JMJD5 in the C terminus region is crucial for expression of HNF4A and replication of HBV. Furthermore, a mutant JMJD5 with Gly(135) replaced by Glu failed to interact with HBx and to rescue the replication of HBV in JMJD5-knockout cells. Taken together, our data suggest that interaction of JMJD5 with HBx facilitates HBV replication through the hydroxylase activity of JMJD5.