Hepatitis B Virus Core Protein Research Articles

LncRNA MALAT1 promotes Erastin-induced ferroptosis in the HBV-infected diffuse large B-cell lymphoma.

In a retrospective analysis of clinical data from 587 DLBCL (diffuse large B-cell lymphoma) patients in China, 13.8% of cases were associated with HBV (hepatitis B virus) infection, leading to distinct clinical features and poorer prognosis. Moreover, HBV infection has a more pronounced impact on the survival of the GCB (germinal center B-cell-like) type DLBCL patients compared to the ABC (activated B-cell-like) type. In this study, we found that the expression of LncRNA MALAT1 (metastasis-associated lung adenocarcinoma transcript 1) was downregulated in the HBV-infected GCB-type DLBCL patients, and the HBV core protein (HBX) directly inhibited the MALAT1 expression in DLBCL cells. Notably, the overexpression of HBX could attenuate the Erastin-induced ferroptosis in the GCB-type DLBCLs, while MALAT1 re-expression restored sensitivity in the HBX-overexpressing DLBCLs in vitro and in vivo. Mechanistically, MALAT1 competitively hindered SFPQ (splicing factor proline and glutamine-rich) from effectively splicing the pre-mRNA of SLC7A11 (solute carrier family 7 member 11), due to a shared TTGGTCT motif, which impeded the SLC7A11 pre-mRNA maturation and hence diminished its negative regulation on ferroptosis. Together, our study identified HBX's role in inhibiting MALAT1 expression, promoting SFPQ-mediated splicing of SLC7A11 pre-mRNA, and reducing the GCB-type DLBCL sensitivity to Erastin-induced ferroptosis. Combined with the recent studies that ferroptosis may be involved in the occurrence and development of DLBCL, these findings explain our clinical data analysis that DLBCL patients with low expression of MALAT1 have poorer prognosis and shorter overall survival, and provide a valuable therapeutic target for the HBV-infected GCB-type DLBCL patients.

HBV shows different levels of adaptation to HLA class I-associated selection pressure correlating with markers of replication

Background & AimsImmune responses by CD8 T cells are essential for control of HBV replication. Although selection of escape mutations in CD8 T cell epitopes has been previously described in HBV infection, its overall influence on HBV sequence diversity and correlation with markers of HBV replication remain unclear. MethodsWhole-genome sequencing was applied to HBV isolates from 532 patients with chronic HBV infection and high-resolution HLA class I genotyping. Using a Bayesian model (HAMdetector) for Identification of HLA-associated mutational states (HAMs) the frequency and location of residues under CD8 T cell selection pressure were determined and the levels of adaptation of individual isolates were quantified. ResultsUsing previously published thresholds for the identification of HAMs, a total of 295 residues showed evidence of CD8 T cell escape, the majority of which were located in previously unidentified epitopes. Interestingly, HAMs were highly enriched in the HBV core protein compared to all other proteins. When individual HBV isolates were compared, different levels of adaptation to HLA class I immune pressure were noted. The level of adaptation increased with patient age and correlated with markers of replication, with low levels of adaptation in HBeAg-positive infection. Furthermore, the levels of adaptation negatively correlated with HBV viral load and HBsAg levels, consistent with high levels of HLA class I-associated selection pressure in patients with low replication level. ConclusionsHBV sequence diversity is shaped by HLA class I-associated selection pressure with the HBV core protein being a predominant target of selection. Importantly, different levels of adaptation to immune pressure were observed between HBV infection stages, which need to be considered in the context of T cell-based therapies. Impact and implicationsThe immune response mediated by CD8 T cells plays a critical role in controlling HBV infection and shows promise for therapeutic strategies aimed at achieving a functional cure. This study demonstrates that mutational escape within CD8 T cell epitopes is common in HBV and represents a key factor in the failure of immune control. Notably, the HBV core protein emerges as the primary target of CD8 T cell selection pressure. Additionally, the observed correlation between HBV adaptation levels and viral replication markers indicates that CD8 T cell immunity may influence transitions between phases of chronic HBV infection.

Conformationally Constrained Isoquinolinones as Orally Efficacious Hepatitis B Capsid Assembly Modulators.

Isoquinolinone-based HBV capsid assembly modulators that bind at the dimer:dimer interface of HBV core protein have been shown to suppress viral replication in chronic hepatitis B patients. Analysis of their binding mode by protein X-ray crystallography has identified a region of the small molecule where the application of a constraint can lock the preferred binding conformation and has allowed for further optimization of this class of compounds. Key analogues demonstrated single digit nM EC50 values in reducing HBV DNA in a HepDE19 cellular assay in addition to favorable ADME and pharmacokinetic properties, leading to a high degree of oral efficacy in a relevant in vivo hydrodynamic injection mouse model of HBV infection, with 12e effecting a 3 log10 decline in serum HBV DNA levels at a once daily dose of 1 mg/kg. Additionally, maintenance of activity was observed in clinically relevant HBV core protein variants T33N and I105T.

Towards Cell-Permeable Hepatitis B Virus Core Protein Variants as Potential Antiviral Agents.

Hepatitis B virus (HBV) infection remains a major health threat with limited treatment options. One of various new antiviral strategies is based on a fusion of Staphylococcus aureus nuclease (SN) with the capsid-forming HBV core protein (HBc), termed coreSN. Through co-assembly with wild-type HBc-subunits, the fusion protein is incorporated into HBV nucleocapsids, targeting the nuclease to the encapsidated viral genome. However, coreSN expression was based on transfection of a plasmid vector. Here, we explored whether introducing protein transduction domains (PTDs) into a fluorescent coreSN model could confer cell-penetrating properties for direct protein delivery into cells. Four PTDs were inserted into two different positions of the HBc sequence, comprising the amphiphilic translocation motif (TLM) derived from the HBV surface protein PreS2 domain and three basic PTDs derived from the Tat protein of human immunodeficiency virus-1 (HIV-1), namely Tat4, NP, and NS. To directly monitor the interaction with cells, the SN in coreSN was replaced with the green fluorescent protein (GFP). The fusion proteins were expressed in E. coli, and binding to and potential uptake by human cells was examined through flow cytometry and fluorescence microscopy. The data indicate PTD-dependent interactions with the cells, with evidence of uptake in particular for the basic PTDs. Uptake was enhanced by a triplicated Simian virus 40 (SV40) large T antigen nuclear localization signal (NLS). Interestingly, the basic C terminal domain of the HBV core protein was found to function as a novel PTD. Hence, further developing cell-permeable viral capsid protein fusions appears worthwhile.

Assessment of HBV variants and novel viral and immune biomarkers in chronic hepatitis B patients with metabolic dysfunction associated steatotic liver disease.

Co-existing chronic hepatitis B virus (CHB) infection and metabolic dysfunction associated steatotic liver disease (MASLD) can exert complex effects on hepatic metabolism, requiring mechanistic study. CHB participants were assessed for MASLD and the impact of hepatic steatosis/metabolic syndrome (MetS) on novel viral and immunological markers. In this prospective, cohort study, untreated CHB subjects were assessed for liver disease by non-invasive tests (i.e. FibroScan, controlled attenuation parameter, CAP). Subjects were tested for cytokines and IFN-γ ELISPOT assay to HBV Surface (S) and Core (C) proteins. Standard HBV serological, exploratory biomarkers and deep sequencing of HBV S and C genes were performed. In 53 subjects (median age 45 years [SD = 10.6], 35% F, 56% Asian, 20% Black, 3% White), 94% (50) HBeAg negative, 63% genotype B/C, mean HBV DNA 3.2 log10 IU/mL (SD = 1.8), quantitative HBsAg 2.9 log10 IU/mL (SD = 1.2) and HBV pgRNA 2.1 log10 copies/mL (SD = 1.3). In enrolled subjects, the mean ALT was 41.9 U/L (SD = 24.0), FibroScan was 5.7 kPa (SD = 1.9) and CAP was 306.4 dB/m (SD = 49.0). The mean BMI was 28.2 kg/m2 (SD = 4.2), 20% (11/53) had diabetes, 35% (19/53) dyslipidaemia and 24% (13/53) hypertension. Subjects with MetS and steatosis showed lower HBV markers (p < .01), higher HBV S diversity (p = .02) and greater frequency of HBV variants associated with host-anti-viral immune escape. Pro-inflammatory cytokine levels and HBV-specific cellular responses were higher in participants with hepatic steatosis. In CHB, MASLD/hepatic steatosis was associated with HBV variants and systemic immune responses potentially impacting liver disease progression despite low-level viraemia.

Colchicine-mediated selective autophagic degradation of HBV core proteins inhibits HBV replication and HBV-related hepatocellular carcinoma progression

The HBV core protein (HBc) is an important viral protein of HBV that plays an indispensable role in the lifecycle of HBV, including capsid assembly and transport, reverse transcription and virus release. In recent years, evidence has shown that HBc may be involved in the malignant progression of HCC. Thus, HBc is an attractive target for antiviral agents and provides a new strategy for the treatment of HBV-related HCC. Here, we identified a novel anti‐HBc compound—colchicine, an alkaloid compound—that promoted selective autophagic degradation of HBc through the AMPK/mTOR/ULK1 signalling pathway. We further confirmed that colchicine promoted the selective autophagy of HBc by enhancing the binding of HBc to the autophagy receptor p62. Finally, we evaluated the effects of colchicine on HBV replication and HBc-mediated HCC metastasis in vitro and in vivo. Our research indicated that the inhibitory effects of colchicine on HBV and HBV-related HCC depend on the selective autophagic degradation of HBc. Thus, colchicine is not only a promising therapeutic strategy for chronic hepatitis B but also a new treatment for HBV-related HCC.

Discovery of novel small molecules targeting hepatitis B virus core protein from marine natural products with HiBiT-based high-throughput screening

Due to the limitations of current anti-HBV therapies, the HBV core (HBc or HBcAg) protein assembly modulators (CpAMs) are believed to be potential anti-HBV agents. Therefore, discovering safe and efficient CpAMs is of great value. In this study, we established a HiBiT-based high-throughput screening system targeting HBc and screened novel CpAMs from an in-house marine chemicals library. A novel lead compound 8a, a derivative of the marine natural product naamidine J, has been successfully screened for potential anti-HBV activity. Bioactivity-driven synthesis was then conducted, and the structure‒activity relationship was analyzed, resulting in the discovery of the most effective compound 11a (IC50 = 0.24 μmol/L). Furthermore, 11a was found to significantly inhibit HBV replication in multiple cell models and exhibit a synergistic effect with tenofovir disoproxil fumarate (TDF) and IFNa2 in vitro for anti-HBV activity. Treatment with 11a in a hydrodynamic-injection mouse model demonstrated significant anti-HBV activity without apparent hepatotoxicity. These findings suggest that the naamidine J derivative 11a could be used as the HBV core protein assembly modulator to develop safe and effective anti-HBV therapies.

TCR-like bispecific antibodies toward eliminating infected hepatocytes in HBV mouse models

Therapeutics for eradicating hepatitis B virus (HBV) infection are still limited and current nucleos(t)ide analogs (NAs) and interferon are effective in controlling viral replication and improving liver health, but they cannot completely eradicate the hepatitis B virus and only a very small number of patients are cured of it. The TCR-like antibodies recognising viral peptides presented on human leukocyte antigens (HLA) provide possible tools for targeting and eliminating HBV-infected hepatocytes. Here, we generated three TCR-like antibodies targeting three different HLA-A2.1-presented peptides derived from HBV core and surface proteins. Bispecific antibodies (BsAbs) were developed by fusing variable fragments of these TCR-like mAbs with an anti-CD3ϵ antibody. Our data demonstrate that the BsAbs could act as T cell engagers, effectively redirecting and activating T cells to target HBV-infected hepatocytes in vitro and in vivo. In HBV-persistent mice expressing human HLA-A2.1, two infusions of BsAbs induced marked and sustained suppression in serum HBsAg levels and also reduced the numbers of HBV-positive hepatocytes. These findings highlighted the therapeutic potential of TCR-like BsAbs as a new strategy to cure hepatitis B.

Label-Free Tracking of Hepatitis B Virus Core Protein Capsid Assembly in Real-Time Using Protein Charge Transfer Spectra.

Hepatitis B virions are double-shelled particles, with a diameter of 40-42 nm, consisting of a nucleocapsid called the HBV core protein (HBV Cp). It is an ordered assembly of 90-120 homodimers arranged in an icosahedral symmetry. Both the full-length HBV Cp and the first-149 residue domain, HBV Cp149, can spontaneously assemble in vitro into capsids with 120 Cp dimers (T = 4) or 90 Cp dimers (T = 3), triggered by high ionic strength of 0.25-0.5 M NaCl. The assembly disassembly of HBV Cp149 capsids are generally studied by light scattering, size-exclusion chromatography, atomic force microscopy, transmission electron microscopy, and other high-end expensive techniques. Here, we report a simple, yet robust, label-free technique exploiting protein charge transfer spectra (ProCharTS) to monitor the capsid assembly in real-time. ProCharTS absorption in the near UV-visible region (250-800 nm) arises when photoinduced electron transfer occurs from HOMO of COO- in glutamate (donor) to LUMO of NH3+ in lysine or polypeptide backbone (acceptor) of the protein. Alternatively, it can also occur from polypeptide backbone (donor) to acceptor in arginine, histidine, or lysine cation. ProCharTS is observed profusely among proximal charge clusters in folded proteins. Here, we show that, ProCharTS absorption among growing HBV capsids is amplified when HBV Cp homodimers assemble, generating new contacts among charged residues in the dimer-dimer interface. We notice a time-dependent sigmoidal increase in ProCharTS absorbance and luminescence during capsid formation in comparison to pure dimers. Additionally, a combined approach of anisotropy-based fluorescence assay is reported, where an increased fluorescence anisotropy was observed in capsids as compared to native and unfolded dimers. We conclude that ProCharTS can serve as a sensitive label-free tool for rapid tracking of capsid assembly in real-time and characterize the assembled capsids from dimers.

Preclinical characterization of a novel potent core protein assembly modulator for the treatment of chronic hepatitis B viral infection

The hepatitis B virus (HBV) capsid or core protein is a promising drug target currently being investigated for potential curative therapies for chronic HBV infection. In this study, we performed extensive in vitro and in vivo characterization of a novel and potent HBV core protein assembly modulator (CpAM), CU15, for both anti-HBV activity and druggability properties. CU15 potently inhibited HBV DNA replication in in vitro HBV-infected HepG2.2.15 cells (EC50 of 8.6 nM), with a low serum shift. It was also effective in inhibiting HBV DNA and cccDNA formation in de novo HBV-infected primary human hepatocytes. Furthermore, CU15 was active across several HBV genotypes and across clinically relevant core protein variants. After oral administration to an in vivo HBV mouse model, CU15 significantly reduced plasma HBV DNA and RNA levels, at plasma exposure consistent with the estimated in vitro potency. In vitro, CU15 exhibited excellent passive permeability and relatively high metabolic stability in liver preparations across species (human > dog> rat). In vitro human liver microsomal studies suggest that the compound's major metabolic pathway is CYP3A-mediated oxidation. Consistent with the in vitro findings, CU15 is a compound with a low-to-moderate clearance and high oral bioavailability in rats and dogs. Based on the apparent in vitro–in vivo correlation observed, CU15 has the potential to exhibit low clearance and high oral bioavailability in humans. In addition, CU15 also showed low drug–drug interaction liability with an acceptable in vitro safety profile (IC50 > 10 µM).

Selective depletion of HBV-infected hepatocytes by class A capsid assembly modulators requires high levels of intrahepatic HBV core protein.

Capsid assembly mediated by hepatitis B virus (HBV) core protein (HBc) is an essential part of the HBV replication cycle, which is the target for different classes of capsid assembly modulators (CAMs). While both CAM-A ("aberrant") and CAM-E ("empty") disrupt nucleocapsid assembly and reduce extracellular HBV DNA, CAM-As can also reduce extracellular HBV surface antigen (HBsAg) by triggering apoptosis of HBV-infected cells in preclinical mouse models. However, there have not been substantial HBsAg declines in chronic hepatitis B (CHB) patients treated with CAM-As to date. To investigate this disconnect, we characterized the antiviral activity of tool CAM compounds in HBV-infected primary human hepatocytes (PHHs), as well as in HBV-infected human liver chimeric mice and mice transduced with adeno-associated virus-HBV. Mechanistic studies in HBV-infected PHH revealed that CAM-A, but not CAM-E, induced a dose-dependent aggregation of HBc in the nucleus which is negatively regulated by the ubiquitin-binding protein p62. We confirmed that CAM-A, but not CAM-E, induced HBc-positive cell death in both mouse models via induction of apoptotic and inflammatory pathways and demonstrated that the degree of HBV-positive cell loss was positively correlated with intrahepatic HBc levels. Importantly, we determined that there is a significantly lower level of HBc per hepatocyte in CHB patient liver biopsies than in either of the HBV mouse models. Taken together, these data confirm that CAM-As have a unique secondary mechanism with the potential to kill HBc-positive hepatocytes. However, this secondary mechanism appears to require higher intrahepatic HBc levels than is typically observed in CHB patients, thereby limiting the therapeutic potential.

TRPV4 promotes HBV replication and capsid assembly via methylation modification of H3K4 and HBc ubiquitin.

Hepatitis B virus (HBV) infection poses a significant burden on global public health. Unfortunately, current treatments cannot fully alleviate this burden as they have limited effect on the transcriptional activity of the tenacious covalently closed circular DNA (cccDNA) responsible for viral persistence. Consequently, the HBV life cycle should be further investigated to develop new anti-HBV pharmaceutical targets. Our previous study discovered that the host gene TMEM203 hinders HBV replication by participating in calcium ion regulation. The involvement of intracellular calcium in HBV replication has also been confirmed. In this study, we found that transient receptor potential vanilloid 4 (TRPV4) notably enhances HBV reproduction by investigating the effects of several calcium ion-related molecules on HBV replication. The in-depth study showed that TRPV4 promotes hepatitis B core/capsid protein (HBc) protein stability through the ubiquitination pathway and then promotes the nucleocapsid assembly. HBc binds to cccDNA and reduces the nucleosome spacing of the cccDNA-histones complex, which may regulate HBV transcription by altering the nucleosome arrangement of the HBV genome. Moreover, our results showed that TRPV4 promotes cccDNA-dependent transcription by accelerating the methylation modification of H3K4. In conclusion, TRPV4 could interact with HBV core protein and regulate HBV during transcription and replication. These data suggest that TRPV4 exerts multifaceted HBV-related synergistic factors and may serve as a therapeutic target for CHB.

Clinical implications of hepatitis B virus core antigen-mediated immunopathologic T cell responses in chronic hepatitis B.

Hepatitis B virus (HBV) infection significantly impacts Asian populations. The influences of continuous HBV antigen and inflammatory stimulation to T cells in chronic hepatitis B (CHB) remain unclear. In this study, we first conducted bioinformatics analysis to assess T-cell signaling pathways in CHB patients. In a Taiwanese cohort, we examined the phenotypic features of HBVcore -specific T cells and their correlation with clinical parameters. We used core protein overlapping peptides from the Taiwan prevalent genotype B HBV to investigate the antiviral response and the functional implication of HBV-specific T cells. In line with Taiwanese dominant HLA-alleles, we also evaluated ex vivo HBVcore -specific T cells by pMHC-tetramers targeting epitopes within HBV core protein. Compared to healthy subjects, we disclosed CD8 T cells from CHB patients had higher activation marker CD38 levels but showed an upregulation in the inhibitory receptor PD-1. Our parallel study showed HBV-specific CD8 T cells were more activated with greater PD-1 expression than CMV-specific subset and bulk CD8 T cells. Moreover, our longitudinal study demonstrated a correlation between the PD-1 fluctuation pattern of HBVcore -specific CD8 T cells and liver inflammation in CHB patients. Our research reveals the HBV core antigen-mediated immunopathologic profile of CD8 T cells in chronic HBV infection. Our findings suggest the PD-1 levels of HBVcore -specific CD8 T cells can be used as a valuable indicator of personal immune response for clinical application in hepatitis management.

Impact of DNA on interactions between core proteins of Hepatitis B virus-like particles comprising different C-terminals

Hepatitis B virus (HBV) virus-like particles (VLPs) are promising therapeutic agents derived from HBV core proteins (Cp). This study investigates the assembly dynamics of HBV VLPs, which is crucial for their potential as drug carriers or gene delivery systems. Coarse-grained molecular dynamics simulations explore the impact of C-terminal domain length (in the Cp ranging from Cp149 to wild-type Cp183) on Cp assembly and stability, particularly in the presence of DNA. Our findings reveal that the C-terminal nucleic acid binding region significantly influences Cp assembly and stability of trimers comprising Cp dimers. Shorter C-terminal domains (Cp164, Cp167) enhance stability and protein-protein interactions, while interactions between naturally occurring Cp183 are destabilized in the absence of DNA. Interestingly, DNA addition further stabilizes Cp assemblies, and this effect is influenced by the length of the nucleic acid binding region. Shorter C-terminal domains show less dependency on DNA content. This stabilization is attributed to electrostatic forces between positively charged C-terminal chains and negatively charged nucleic acids. Our study sheds light on the molecular mechanisms governing protein-protein and protein-DNA interactions in HBV VLP assembly, providing insights into Cp processability and informing the development of efficient gene therapy carriers using VLP technology.

SRPK2 Mediates HBV Core Protein Phosphorylation and Capsid Assembly via Docking Interaction.

Members of the serine-arginine protein kinase (SRPK) family, SRPK1 and SRPK2, phosphorylate the hepatitis B core protein (Cp) and are crucial for pregenomic RNA encapsidation during viral nucleocapsid assembly. Among them, SRPK2 exhibits higher kinase activity toward Cp. In this study, we identified Cp sites that are phosphorylated by SRPK2 and demonstrated that the kinase utilizes an SRPK-specific docking groove to interact with and regulate the phosphorylation of the C-terminal arginine rich domain of Cp. We determined that direct interaction between the docking groove of SRPK2 and unphosphorylated Cp inhibited premature viral capsid assembly in vitro, whereas the phosphorylation of the viral protein reactivated the process. Pull-down assays together with the new cryo-electron microscopy structure of the HBV capsid in complex with SRPK2 revealed that the kinases decorate the surface of the viral capsid by interacting with the C-terminal domain of Cp, underscoring the importance of the docking interaction in regulating capsid assembly and pregenome packaging. Moreover, SRPK2-knockout in HepG2 cells suppressed Cp phosphorylation, indicating that SRPK2 is an important cellular kinase for HBV life cycle.

Class A capsid assembly modulator apoptotic elimination of hepatocytes with high HBV core antigen level in vivo is dependent on de novo core protein translation.

Treatment with hepatitis B virus (HBV) capsid assembly modulators that induce the formation of aberrant HBV core protein structures (CAM-A) leads to programmed cell death, apoptosis, of HBV-infected hepatocytes and subsequent reduction of HBV antigens, which differentiates CAM-A from other CAMs. The effect is dependent on the de novo synthesis and high levels of core protein.

Hepatitis B virus RNAs co-opt ELAVL1 for stabilization and CRM1-dependent nuclear export.

Hepatitis B virus (HBV) chronically infects 296 million people worldwide, posing a major global health threat. Export of HBV RNAs from the nucleus to the cytoplasm is indispensable for viral protein translation and genome replication, however the mechanisms regulating this critical process remain largely elusive. Here, we identify a key host factor embryonic lethal, abnormal vision, Drosophila-like 1 (ELAVL1) that binds HBV RNAs and controls their nuclear export. Using an unbiased quantitative proteomics screen, we demonstrate direct binding of ELAVL1 to the HBV pregenomic RNA (pgRNA). ELAVL1 knockdown inhibits HBV RNAs posttranscriptional regulation and suppresses viral replication. Further mechanistic studies reveal ELAVL1 recruits the nuclear export receptor CRM1 through ANP32A and ANP32B to transport HBV RNAs to the cytoplasm via specific AU-rich elements, which can be targeted by a compound CMLD-2. Moreover, ELAVL1 protects HBV RNAs from DIS3+RRP6+ RNA exosome mediated nuclear RNA degradation. Notably, we find HBV core protein is dispensable for HBV RNA-CRM1 interaction and nuclear export. Our results unveil ELAVL1 as a crucial host factor that regulates HBV RNAs stability and trafficking. By orchestrating viral RNA nuclear export, ELAVL1 is indispensable for the HBV life cycle. Our study highlights a virus-host interaction that may be exploited as a new therapeutic target against chronic hepatitis B.

Synthesis of the full-length hepatitis B virus core protein and its capsid formation.

Chronic infection with hepatitis B virus (HBV) is a major cause of cirrhosis and liver cancer. Capsid assembly modulators can induce error-prone assembly of HBV core proteins to prevent the formation of infectious virions, representing promising candidates for treating chronic HBV infections. To explore novel capsid assembly modulators from unexplored mirror-image libraries of natural products, we have investigated the synthetic process of the HBV core protein for preparing the mirror-image target protein. In this report, the chemical synthesis of full-length HBV core protein (Cp183) containing an arginine-rich nucleic acid-binding domain at the C-terminus is presented. Sequential ligations using four peptide segments enabled the synthesis of Cp183 via convergent and C-to-N direction approaches. After refolding under appropriate conditions, followed by the addition of nucleic acid, the synthetic Cp183 assembled into capsid-like particles.

Regulation of Hepatitis B Virus Replication by Modulating Endoplasmic Reticulum Stress (ER-Stress).

Hepatitis B virus (HBV), resistant to several antiviral drugs due to viral genomic mutations, has been reported, which aggravates chronic infection and leads to hepatocellular carcinoma. Therefore, host cellular factors/signaling modulation might be an alternative way of treatment for drug-resistant HBV. Here, we investigated the viral protein expression, replication, and virion production using endoplasmic reticulum (ER) stress-modulating chemicals, tunicamycin (an ER-stress inducer), and salubrinal (an ER-stress inhibitor). We found that ER-stress could be induced by HBV replication in transfected HepG2 cells as well as by tunicamycin as demonstrated by dual luciferase assay. HBV intracellular core-associated DNA quantified by qPCR has been significantly increased by tunicamycin in transfected HepG2 cells. Inversely, intracellular core associated and extracellular particle DNA has been significantly decreased in a dose-dependent manner in salubrinal-treated HepG2 cells transfected with HBV-replicating plasmid pHBI. Similar results were found in stably HBV-expressing hepatoblastoma (HB611) cells treated with salubrinal. However, increased or decreased ER-stress by tunicamycin or salubrinal treatment, respectively, has been confirmed by expression analysis of grp78 using Western blot. In addition, Western blot results demonstrated that the expression of HBV core protein and large HBsAg is increased and decreased by tunicamycin and salubrinal, respectively. In conclusion, the sal-mediated inhibition of the HBV replication and virion production might be due to the simultaneous reduction of core and large HBsAg expression and maintaining the ER homeostasis. These results of HBV replication regulation by modulation of ER-stress dynamics would be useful for designing/identifying anti-HBV drugs targeting cellular signaling pathways.

Binding modes in ligand-docked hepatitis B virus core protein simulated by a Monte Carlo method

Hepatitis B virus core protein (HBV Cp) is closely involved in the viral assembly, nuclear functions, compartment for reverse transcription, and intra-cellular trafficking. Therefore, modulation of HBV Cp assembly is a promising method to control HBV infection in both preclinical and clinical studies. In this paper, two ligands of HAP18 and AT-130, as representations of heteroaryldihydropyrimidines and phenylpropenamides, have been chosen. Their Binding modes and conformations docking with the HBV Cp have been simulated by a Monte Carlo method. Strong polar contact in HAP18-bound and relatively weak interaction dominated by the Lennard-Jones potential in AT130-bound have been observed, respectively. Although different binding modes result in different assembly behaviors of HBV core protein, both of them strongly influence the quaternary structure of the Cp assembly, changing the spatial relationship between dimers, and inducing noninfective Cp misassembly. The simulation is expected to be helpful to get some insight into the antiviral mechanism of HBV Cp assembly modulation.