Hepatitis B Virus Gene Research Articles

The potential of HBV cure: an overview of CRISPR-mediated HBV gene disruption.

Hepatitis B virus (HBV) infection is a common cause of liver disease worldwide. The current antiviral treatment using nucleotide analogues (NAs) can only suppress de novo HBV replication but cannot eliminate chronic HBV infection due to the persistence of covalently closed circular (ccc) DNA that sustains viral replication. The CRISPR/Cas9 system is a novel genome-editing tool that enables precise gene disruption and inactivation. With high efficiency and simplicity, the CRISPR/Cas9 system has been utilized in multiple studies to disrupt the HBV genome specifically, eliciting varying anti-HBV effects both in vitro and in vivo. Additionally, multi-locus gene targeting has shown enhanced antiviral activity, paving the way for combination therapy to disrupt and inactivate HBV cccDNA as well as integrated HBV DNA. Despite its promising antiviral effects, this technology faces several challenges that need to be overcome before its clinical application, i.e., off-target effects and in vivo drug delivery. As such, there is a need for improvement in CRISPR/Cas9 efficiency, specificity, versatility, and delivery. Here, we critically review the recent literature describing the tools employed in designing guide RNAs (gRNAs) targeting HBV genomes, the vehicles used for expressing and delivering CRISPR/Cas9 components, the models used for evaluating CRISPR-mediated HBV gene disruption, the methods used for assessing antiviral and off-target effects induced by CRISPR/Cas9-mediated HBV gene disruption, and the prospects of future directions and challenges in leveraging this HBV gene-editing approach, to advance the HBV treatment toward a clinical cure.

Interrelationships among MTHFR gene polymorphisms, MTRR gene polymorphisms, and HBV gene BCP 1762/1764 mutations with disease progression in Chronic hepatitis B virus infection patients

Objective Chronic hepatitis B virus (HBV) infection is a major disease that seriously affects the health of patients. In this paper, the relationship among MTHFR gene polymorphism, MTRR gene polymorphism and 1762/1764 mutation in the BCP region of HBV gene with disease progression in chronic HBV patients was studied. Methods A total of 144 chronic HBV infection patients from January 2021 to June 2022 in the Third People’s Hospital of Zigong City, were included as the study subjects. These patients were divided into hepatitis B primary liver cancer patients group (PLC) in 51 cases, Non-primary liver cancer patients group (Non-PLC) in 93 cases, Non-PLC is also divided into chronic hepatitis B virus carriers (CHC) in 49 cases, hepatitis B Live cirrhosis(LC) in 44 cases. MTHFR (C677T), MTRR (A66G) and MTHFR (A1298C) genes polymorphisms were detected by PCR-dissolution curve. The level of HBV-DNA was quantified by real-time PCR, and the 1762/1764 mutation site in the BCP region of the HBV gene were detected by ARMS-PCR. Data were statistically analyzed using the SPSS statistical software. Results The proportion of HBV mutations in BCP region 1762/1764 in PLC group was 82.4%, which was higher than that in LC group (63.6%) and CHC group (51.0%), and the differences were statistically significant (p < 0.05). There were no significant differences in the distribution of MTHFR C677T, MTHFR A1298C and MTRR A66G polymorphisms among CHC, LC and PLC (p > 0.05). The polymorphism distribution of MTHFR C677T, MTRR A66G and MTHFR A1298C genes in patients with chronic hepatitis B virus infection at different stages (CHC, LC and PLC) showed no gender or age differences between and within groups (p > 0.05). Among the patients with MTHFR 677CT + TT, MTRR 66AG + GG and MTHFR 1298AA genotype, the proportion of HBV mutation in BCP region 1762/1764 in PLC group was higher than that in CHC group and LC group, and the differences were statistically significant (p < 0.05). Folate levels in the PLC group were lower than those in the non-PLC group (CHC and LC patients), and the difference was statistically significant compared with the CHC group (p < 0.05). In different MTHFR C677T and MTRR A66G genotypes, the serum GGT activity were statistically significant between mutant PLC and mutant Non-PLC (p < 0.05). Conclusion MTHFR C677T, MTRR A66G and MTHFR A1298C gene polymorphisms distribution have no gender and age differences in chronic hepatitis B virus infection patients. The mutation of HBV gene BCP region 1762/1764 may be associated with the occurrence and development of liver cancer in patients with chronic HBV infection. Single difference of MTHFR C677T, MTHFR A1298C and MTRR A66G gene polymorphisms may have little effect on the disease progression in patients with chronic HBV infection. MTHFR 677CT + TT, MTRR 66AG + GG and MTHFR 1298AA genotype combined with HBV gene BCP region 1762/1764 mutation may be closely related to the occurrence and development of hepatitis B liver cancer.

Interferon-stimulated gene (ISG12a) suppresses hepatitis B virus replication in Huh 7 cells line

Hepatitis B virus (HBV) and its associated chronic liver disease pose a significant health hazard. Chronic HBV infection is a major contributor to the development of liver cirrhosis, liver fibrosis, and liver cancer. This study focused on ISG12a and its inhibitory effect in Huh7 cells on HBV gene expression and replication. The mammalian hepatoma cells Huh7 were transfected with the pHBV1.3 vector (pCAGGS) or HA-tagged ISG12a to determine the overexpression, to test this hypothesis further, we did knockdown or silencing by transducing Huh7 cells with lentiviruses containing shRNAs targeting ISG12a or scramble control shRNA (shControl). The expression of ISG12a was evaluated through western blot analysis. The HBsAg and HBeAg secretion in the Huh7 cells’ culture media was examined using an ELISA test. The qRT-PCR confirmed the mRNA and 3.5 mRNA Kb of ISG12a. The HBV total RNA was extracted and evaluated through a Northern blot. The isolated DNA was detected through qPCR. Additionally, a mechanistic study of enhancer II (EnhII/Cp) was examined through luciferase reporter testing. Our research findings indicate that ISG12a, an interferon-stimulated gene (ISG), plays a crucial role in suppressing the replication and gene expression of HBV. According to our study using the Huh7 cell system, overexpression of ISG12a resulted in a notable reduction in HBV protein levels as well as intracellular core-associated DNA and RNA levels. On the other hand, silencing ISG12a in Huh7 cells resulted in increased HBV RNA transcripts, DNA, and secreted proteins, indicating that ISG12a plays a role in suppressing HBV replication. Additionally, the research revealed that ISG12a inhibits the function of the EnhII/Cp promoter, which results in reduced HBV gene expression. The EnhII/Cp promoter is involved in regulating HBV gene expression, and the study showed that ISG12a restricts its activity. ISG12a may have a regulatory role in controlling the expression of HBV genes. These findings highlight the importance of ISG12a in HBV gene expression and provide valuable insights for understanding its antiviral function.

Establishment of a Cleavage-Based Single-Plasmid Dual-Luciferase Surrogate Reporter for the Cleavage Efficiency Evaluation of CRISPR-Cas12a Systems and Its Primary Application.

CRISPR-Cas technology is a widely utilized gene-editing tool that involves gRNA-guided sequence recognition and Cas nuclease-mediated cleavage. The design and evaluation of gRNA are essential for enhancing CRISPR/Cas editing efficiency. Various assays such as single-strand annealing, in vitro cleavage, and T7 endonuclease I (T7EI) are commonly used to assess gRNA-mediated Cas protein cleavage activity. In this study, a firefly luciferase and Renilla luciferase co-expressed and a cleavage-based single-plasmid dual-luciferase surrogate reporter was built to evaluate the gRNA-mediated Cas12a cleavage efficiency. The cleavage activities of CRISPR-Cas12a can be quantitatively determined by the recovery degree of firefly luciferase activity. The cleavage efficiency of CRISPR-Cas12a can be quantitatively measured by the recovery of firefly luciferase activity. By using this system, the cleavage efficiency of CRISPR-Cas12a on hepatitis B virus (HBV)/D expression plasmid was evaluated, revealing a negative correlation between gRNA cleavage efficiency and HBV gene expression measured using an enzyme-linked immunosorbent assay. This simple, efficient, and quantifiable system only requires the dual-luciferase vector and CRISPR-Cas12a vector, making it a valuable tool for selecting effective gRNAs for gene editing.

Low Prevalence of Anti-HBc Antibody and Lack of HBV DNA Among HBsAg-Negative Blood Donors in Iran: A Cross-sectional Study and Review of Literature.

Occult hepatitis B infection (OBI) refers to the presence of hepatitis B virus (HBV) DNA in the serum or liver of individuals who tested negative for HBV surface antigen (HBsAg). This study aimed to determine seropositivity for antibodies against HBV core antigen (anti-HBc) and the frequency of OBI among the HBsAg non-reactive blood donors in Mashhad, northeastern Iran. In this cross-sectional study, serum samples of HBsAg-negative blood donors were examined for anti-HBc during June and August 2018. Anti-HBc-positive samples were tested for antibodies against HBsAg (anti-HBs), and those with negative results were classified as isolated anti-HBc cases. The presence of HBV DNA in the C, S, and X gene regions was assessed by a qualitative real-time polymerase chain reaction method in all HBsAg-negative samples. OBI subjects were detected by the presence of at least one HBV genomic region. Of 540 HBsAg-negative donors, 29 (5.4%; 95% confidence interval: 3.6-7.6%) showed seroreactivity for anti-HBc, of whom 18 individuals were also seropositive for anti-HBs. All donors showed negative results for all three HBV genes regardless of their serum anti-HBc status. Based on our findings, we suggest routine screening of Iranian blood donation volunteers for serum anti-HBc and anti-HBs but not HBV DNA.

The lack of HBsAg secretion does neither facilitate induction of antiviral T cell responses nor Hepatitis B Virus clearance in mice

Immune tolerance to the hepatitis B virus (HBV) is crucial for developing chronic hepatitis B, and the HBV surface antigen (HBsAg) produced and secreted in high amounts is regarded as a key contributor. HBsAg is expressed in HBV-infected hepatocytes and those carrying an HBV integration. Whether either HBsAg secretion or the high antigen amount expressed in the liver determines its immunomodulatory properties, however, remains unclear. We, therefore, developed a novel HBV animal model that allowed us to study the role of secreted HBsAg. We introduced a previously described HBs mutation, C65S, abolishing HBsAg secretion into a replication-competent 1.3-overlength HBV genome and used adeno-associated virus vectors to deliver it to the mouse liver. The AAV-HBV established a carrier state of wildtype and C65S mutant HBV, respectively. We investigated antiviral B- and T-cell immunity in the HBV-carrier mice after therapeutic vaccination. Moreover, we compared the effect of a lacking HBsAg secretion with that of an antiviral siRNA. While missing HBsAg secretion allowed for higher levels of detectable anti-HBs antibodies after therapeutic vaccination, it did neither affect antiviral T-cell responses nor intrahepatic HBV gene expression, irrespective of the starting level. A treatment with HBV siRNA restricting viral antigen expression within hepatocytes, however, improved the antiviral efficacy of therapeutic vaccination, irrespective of the ability of HBV to secrete HBsAg. Our data indicate that clearing HBsAg from blood cannot significantly impact HBV persistence or T-cell immunity. This indicates that a restriction of hepatic viral antigen expression will be required to break HBV immunotolerance.

A mutual regulatory loop between transcription factor Yin Yang 1 and hepatitis B virus replication influences chronic hepatitis B

Hepatitis B virus (HBV) infections pose a major threat to human health. HBV can upregulate the expression of the transcription factor Yin Yang 1 (YY1) in in vitro cytological experiments, suggesting an association between YY1 and HBV infection. However, data on YY1 expression in chronic hepatitis B (CHB) patients are lacking. In this study, we aimed to assess the correlation between YY1 expression and HBV infection. We detected serum YY1 levels in 420 patients with chronic HBV infection, 30 patients with chronic hepatitis C virus infection, and 32 healthy controls using an enzyme-linked immunosorbent assay. The correlation between YY1 levels and clinical parameters was analyzed. Meanwhile, the changes of YY1 before and after interferon or entecavir treatment were analyzed. YY1 levels in the liver tissues were detected using immunofluorescence staining. The expression of YY1 in HBV-expressing cells was detected through western blotting. Meanwhile, we explored the effects of YY1 on HBV replication and gene expression. We found that YY1 was highly expressed in the serum and liver tissues of CHB patients. Serum YY1 levels positively correlated with HBV DNA and hepatitis B surface antigen (HBsAg). Additionally, HBV DNA levels increased but HBsAg levels decreased after HBV-expressing cells overexpress YY1. In conclusion, our study demonstrates that YY1 plays an important role in HBV replication and gene expression, providing a potential target for the treatment of CHB.

Mechanisms of Hepatitis B Virus cccDNA and Minichromosome Formation and HBV Gene Transcription.

Hepatitis B virus (HBV) is the etiologic agent of chronic hepatitis B, which puts at least 300 million patients at risk of developing fibrosis, cirrhosis, and hepatocellular carcinoma. HBV is a partially double-stranded DNA virus of the Hepadnaviridae family. While HBV was discovered more than 50 years ago, many aspects of its replicative cycle remain incompletely understood. Central to HBV persistence is the formation of covalently closed circular DNA (cccDNA) from the incoming relaxed circular DNA (rcDNA) genome. cccDNA persists as a chromatinized minichromosome and is the major template for HBV gene transcription. Here, we review how cccDNA and the viral minichromosome are formed and how viral gene transcription is regulated and highlight open questions in this area of research.

Hepatitis B virus genotypes associated with pregnant women in Northern Thailand

BackgroundMother-to-child transmission of hepatitis B virus (HBV) is the major route of transmission causing persistent infection. The prevalence of HBV infection and HBV genotypes found in different geographical areas varies from country to country. Therefore, this study was conducted to identify the HBV genotypes in HBV-infected pregnant women in Northern Thailand. MethodsStored blood samples that were collected from 145 HBsAg-positive pregnant women who gave birth at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand from 2017 to 2020 were analyzed. The partial nucleotide sequence of the S gene of HBV was amplified by nested PCR and sequenced. All sequences were analyzed phylogenetically together with the reference strains to define the HBV genotypes. ResultsA total of 31 blood samples from 145 HBsAg-positive pregnant women were positive for HBV by nested PCR. The detected HBV strains were identified as presumptive subgenotypes C1 (77.4%; 24/31), B9 (9.7%; 3/31), C2 (3.2%; 1/31), B2 (3.2%; 1/31), B4 (3.2%; 1/31), and presumptive B4/C2 recombinant subgenotype (3.2%; 1/31). ConclusionsThe findings revealed that presumptive subgenotype C1 was the most common subgenotype circulating in pregnant women in Northern Thailand and accounted for 77.4% of cases, followed by presumptive subgenotypes B9, C2, B2, and B4. Furthermore, this study reported, for the first time in Thailand, the HBV genotypes and presumptive subgenotypes, particularly subgenotype B9 circulating in pregnant women.

Molecular Investigation of Occult Hepatitis B Virus Infection Among Patients with Liver Cancers

Background: Hepatitis B virus (HBV) is still the leading cause of hepatocellular carcinoma (HCC). HBV could persist in the low replicate state that is defines as occult hepatitis B virus infection (OBI). Recently, OBI has been defined important in the development and/or exacerbation of HCC and other liver diseases. Objectives: This study tried to determine the frequency of OBI among liver tumor samples. Methods: This cross-sectional study was performed among patients with HCC and intrahepatic cholangiocarcinoma (iCCA) in hospitals affiliated with Iran University of Medical Sciences. Liver tumor samples (Fresh frozen and formalin fixed paraffin embedded) were processed for isolation of DNA and then subjected to molecular assays, including PCR examinations of HBV genes (S, X, and C), determination of viral loads, detection of HBV-cccDNA, phylogenetic analysis, and assessment of mutations in HBsAg and RT regions. Results: In total, there were 93 participants, including HCC (n = 60), iCCA (n = 33); among which, 15% were detected positive for OBI. The OBI among HCC and iCCA were 18.3% and 9.1%, respectively. The mean intrahepatic viral load was 1.3 × 105 ± 1.4 × 102 copies/µl, and 5 had detectable cccDNA. The OBI subjects belonged to the HBV genotype D and subgenotype D1. In the HBsAg protein, T45N (33.3%) and P105A (25%) were the most prevalent mutations. N53K (33.3%), Y54H (25%), L80I (33.3%), and A113G (25%) were missense mutations that were observed in the RT domain. Conclusions: HBV-DNA was detected among liver tumor samples with negative HBsAg status. The results of viral load and cccDNA tests are important in identification and prognosis of liver diseases. It’s needed more precise molecular and cohort studies to clarify the functions of OBI in liver diseases.

Clinical application value of hepatitis B virus basal core promoter 1762/1764 and GGTII and GGT in patients with HBV-DNA-positive primary liver cancer.

Hepatitis B virus (HBV) is closely related to the occurrence and development of primary liver cancer (PLC). The early diagnosis of PLC is difficult. The study explored the clinical application value of the HBV gene basal core promoter (BCP) region 1762/1764 combined with gamma-glutamyl transpeptidase (GGT) and its isozyme II (GGTII) in PLC. From June 2017 to June 2021, 145 hepatitis B surface antigen-positive and HBV DNA-positive patients were enrolled in the Third People Hospital of Zigong. Of them, 67 were chronic hepatitis B (CHB) patients, 30 were liver cirrhosis patients, and 48 were patients with hepatitis B-associated PLC. The HBV BCP 1762/1764 mutation was detected through the amplification refractory mutation system fluorescence PCR method, and GGTII was detected using the double-antibody sandwich method. The results showed that the serum GGT activity, GGTII level, aspartate aminotransferase (AST) activity, AST/alanine aminotransferase (ALT) ratio, GGT/ALT ratio, and GGT/AST ratio were significantly different between the PLC and CHB groups. Statistically significant differences in serum GGT activity, AST activity, and GGT/ALT ratio were observed between the PLC and LC groups. The BCP 1762/1764 mutation rate between the PLC and CHB groups was statistically significant. The GGTII level in the early PLC (stage I + II) group and the advanced PLC (stage III + IV) group was higher than that in the N-PLC group. Serum GGT activity in the early PLC and advanced PLC groups was higher than that in the N-PLC group. The area under the curve of the receiver operator characteristic curve of GGT and GGTII for diagnosing PLC was 0.775 (95% confidence interval [CI] [0.697, 0.854]) and 0.608 (95% CI [0.512, 0.704]), respectively. The area under curve of GGT and GGTII for diagnosing early PLC was 0.732 (95% CI [0.620, 0.845]) and 0.579 (95% CI [0.452, 0.706]), respectively. HBV gene BCP 1762/1764 mutation, GGT, and GGTII may be related to PLC occurrence. The HBV gene BCP region 1762/1764 combined with GGT has certain clinical diagnostic values for PLC and early PLC. However, GGTII is not a good indicator of early PLC and is more relevant to advanced PLC.

MiR-HCC2 suppresses hepatitis B virus replication by inhibiting the activity of the enhancer I/X promoter.

miR-HCC2 has been reported to markedly promote the growth, metastasis, and stemness of hepatocellular carcinoma (HCC) cells in vitro and in vivo. Deep sequencing showed that miR-HCC2 was significantly upregulated in hepatitis B virus (HBV)-positive (HBV+) HCC tissue samples compared with HBV-negative (HBV-) HCC tissue samples. miR-HCC2 expression was further evaluated in HCC tissues and cells, and the expression of miR-HCC2 was found to be significantly higher in HBV+ HCC tissues and cells than in HBV- HCC tissues and cells, suggesting that high miR-HCC2 expression could be induced by HBV infection. To explore the relationship between miR-HCC2 and HBV, we investigated the effect of miR-HCC2 on HBV antigen expression, transcription, and replication. We found that miR-HCC2 was involved in the negative feedback regulation of HBV replication. Further mechanistic studies revealed that miR-HCC2 suppressed HBV replication by inhibiting the activity of the enhancer I/Xpromoter. Our study demonstrates the effect of the inhibition of miR-HCC2 on HBV gene expression and replication, which can help to illustrate the complex regulatory network involving host miRNAs and HBV.

Diagnostic Performance of Precore Protein 22 Kilodalton Levels of HBV DNA in Chronic Hepatitis B Patients

Hepatitis B Virus (HBV) infection causes inflammation of the liver, which has a high prevalence in both Indonesia and the world. Serum HBV deoxyribonucleic acid (DNA) is important in determining the initiation therapy for Chronic Hepatitis B (CHB) patients. However, it has several limitations. Precore protein 22 kilodalton (p22cr) is synthesized from the HBV gene in hepatocytes, representing covalently closed circle (ccc) DNA. This study aimed to analyze the diagnostic performance of p22cr levels on HBV DNA in CHB patients. An observational analytic study with a cross-sectional approach was conducted on 83 CHB patients who were examined at the Clinical Pathology Laboratory of Dr. Moewardi General Academic Hospital in December 2020. Blood plasma samples were taken for HBV DNA and p22cr examination by using Polymerase Chain Reaction (PCR) and Enzyme-Linked Immunosorbent Assay (ELISA), respectively. The cut-off level of p22cr was determined by the Receiver Operating Curve (ROC) with the widest area Under the Curve (AUC). Sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV), Positive Likelihood Ratio (PLR), Negative Likelihood Ratio (NLR), and accuracy were calculated for the diagnostic performance of p22cr. The cut-off point of p22cr on HBV DNA &gt; 20,000 IU/mL was 7.440 ng/mL with AUC 0.693 (p=0.003). The diagnostic performance of p22cr levels on HBV DNA obtained 44.44% sensitivity, 82.98% specificity, 66.67% PPV, 66.10% NPV, 2.61 PLR, 0.67 NLR, and 66.27% accuracy. P22cr level has a good specificity so it can be an alternative examination of HBV DNA in making decisions on therapy in patients with chronic hepatitis B. Further research needs to be done using HBcrAg and excluding elderly patients.

Deficiency of SCAP inhibits HBV pathogenesis via activation of the interferon signaling pathway

Hepatitis B virus (HBV) infects the liver and is a major risk factor for liver cirrhosis and hepatocellular carcinoma. Approaches for an effective cure are thwarted by limited knowledge of virus-host interactions. Herein, we identified SCAP as a novel host factor that regulates HBV gene expression. SCAP, sterol regulatory element-binding protein (SREBP) cleavage-activating protein, is an integral membrane protein located in the endoplasmic reticulum. The protein plays a central role in controlling lipid synthesis and uptake by cells. We found that gene silencing of SCAP significantly inhibited HBV replication; furthermore, knockdown of SREBP2 but not SREBP1, the downstream effectors of SCAP, reduced HBs antigen production from HBV infected primary hepatocytes. We also demonstrated that knockdown of SCAP resulted in activation of interferons (IFNs) and IFN stimulated genes (ISGs). Conversely, ectopic expression of SREBP2 in SCAP-deficient cells restored expression of IFNs and ISGs. Importantly, expression of SREBP2 restored HBV production in SCAP knockdown cells, suggesting that SCAP participates in HBV replication through an effect on IFN production via its downstream effector SREBP2. This observation was further confirmed by blocking IFN signaling by an anti-IFN antibody, which restored HBV infection in SCAP-deficient cells. This led to the conclusion that SCAP regulates the IFN pathway through SREBP, thereby affecting the HBV lifecycle. This is the first study to reveal the involvement of SCAP in regulation of HBV infection. These results may facilitate development of new antiviral strategies against HBV.

Fibroblast Growth Factor 11 Inhibits Hepatitis B Virus Gene Expression Through FXRα Suppression

Fibroblast growth factor 11 (FGF11) is a member of the intracellular FGF family, which shows different signal transmission compared with other FGF superfamily members. The molecular function of FGF11 is not clearly understood. In this study, we identified the inhibitory effect of FGF11 on hepatitis B virus (HBV) gene expression through transcriptional suppression. FGF11 decreased the mRNA and protein expression of HBV genes in liver cells. While the nuclear receptor FXRα1 increased HBV promoter transactivation, FGF11 decreased the FXRα-mediated gene induction of the HBV promoter by the FXRα agonist. Reduced endogenous levels of FXRα by siRNA and the dominant negative mutant protein (aa 1–187 without ligand binding domain) of FXRα expression indicated that HBV gene suppression by FGF11 is dependent on FXRα inhibition. In addition, FGF11 interacts with FXRα protein and reduces FXRα protein stability. These results indicate that FGF11 inhibits HBV replicative expression through the liver cell-specific transcription factor, FXRα, and suppresses HBV promoter activity. Our findings may contribute to the establishment of better regimens for the treatment of chronic HBV infections by including FGF11 to alter the bile acid mediated FXR pathway.

Synthetic gRNA/Cas9 ribonucleoprotein targeting HBV DNA inhibits viral replication.

The presence of hepatitis B virus (HBV) covalently closed circular (ccc) DNA (cccDNA), which serves as a template for viral replication and integration of HBV DNA into the host cell genome, sustains liver pathogenesis and constitutes an intractable barrier to the eradication of chronic HBV infection. The current antiviral therapy for HBV infection, using nucleos(t)ide analogues (NAs), can suppress HBV replication but cannot eliminate integrated HBV DNA and episomal cccDNA. Clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 is a powerful genetic tool that can edit integrated HBV DNA and minichromosomal cccDNA for gene therapy, but its expression and delivery require a viral vector, which poses safety concerns for therapeutic applications in humans. In the present study, we used synthetic guide RNA (gRNA)/Cas9-ribonucleoprotein (RNP) as a nonviral formulation to develop a novel CRISPR/Cas9-mediated gene therapy for eradicating HBV infection. We designed a series of gRNAs targeting multiple specific HBV genes and tested their antiviral efficacy and cytotoxicity in different HBV cellular models. Transfection of stably HBV-infected human hepatoma cell line HepG2.2.15 with HBV-specific gRNA/Cas9 RNPs resulted in a substantial reduction in HBV transcripts. Specifically, gRNA5 and/or gRNA9 RNPs significantly reduced HBV cccDNA, total HBV DNA, pregenomic RNA, and HBV antigen (HBsAg, HBeAg) levels. T7 endonuclease 1 (T7E1) cleavage assay and DNA sequencing confirmed specific HBV gene cleavage and mutations at or around the gRNA target sites. Notably, this gene-editing system did not alter cellular viability or proliferation in the treated cells. Because of their rapid DNA cleavage capability, low off-target effects, low risk of insertional mutagenesis, and readiness for use in clinical application, these results suggest that synthetic gRNA/Cas9 RNP-based gene-editing can be utilized as a promising therapeutic drug for eradicating chronic HBV infection.

Pre- and Post-Transcriptional Control of HBV Gene Expression: The Road Traveled towards the New Paradigm of HBx, Its Isoforms, and Their Diverse Functions.

Hepatitis B virus (HBV) is an enveloped DNA human virus belonging to the Hepadnaviridae family. Perhaps its main distinguishable characteristic is the replication of its genome through a reverse transcription process. The HBV circular genome encodes only four overlapping reading frames, encoding for the main canonical proteins named core, P, surface, and X (or HBx protein). However, pre- and post-transcriptional gene regulation diversifies the full HBV proteome into diverse isoform proteins. In line with this, hepatitis B virus X protein (HBx) is a viral multifunctional and regulatory protein of 16.5 kDa, whose canonical reading frame presents two phylogenetically conserved internal in-frame translational initiation codons, and which results as well in the expression of two divergent N-terminal smaller isoforms of 8.6 and 5.8 kDa, during translation. The canonical HBx, as well as the smaller isoform proteins, displays different roles during viral replication and subcellular localizations. In this article, we reviewed the different mechanisms of pre- and post-transcriptional regulation of protein expression that take place during viral replication. We also investigated all the past and recent evidence about HBV HBx gene regulation and its divergent N-terminal isoform proteins. Evidence has been collected for over 30 years. The accumulated evidence simply strengthens the concept of a new paradigm of the canonical HBx, and its smaller divergent N-terminal isoform proteins, not only during viral replication, but also throughout cell pathogenesis.

A spatiotemporally controlled recombinant cccDNA mouse model for studying HBV and developing drugs against the virus

Covalently closed circular (ccc) DNA is the template for hepatitis B virus (HBV) replication. The lack of small animal models for characterizing chronic HBV infection has hampered research progress in HBV pathogenesis and drug development. Here, we generated a spatiotemporally controlled recombinant cccDNA (rcccDNA) mouse model by combining Cre/loxP-mediated DNA recombination with the liver-specific “Tet-on/Cre” system. The mouse model harbors three transgenes: a single copy of the HBV genome (integrated at the Rosa26 locus, RHBV), H11-albumin-rtTA (spatiotemporal conditional module), and (tetO)7-Cre (tetracycline response element), and is named as RHTC mouse. By supplying the RHTC mice with doxycycline (DOX)-containing drinking water for two days, the animals generate rcccDNA in hepatocytes, and the rcccDNA supports active HBV gene expression and can maintain HBV viremia persistence for over 60 weeks. Persistent HBV gene expression induces intrahepatic inflammation, fibrosis, and dysplastic pathology, which closely mirrors the disease progression in clinical patients. Bepirovirsen, an antisense oligonucleotide (ASO) targeting all HBV RNA species, showed dose-dependent antiviral effects in the RHTC mouse model. The spatiotemporally controlled rcccDNA mouse is convenient and reliable, providing versatile small animal model for studying cccDNA-centric HBV biology as well as evaluating antiviral therapeutics.

Inhibition of HBV replication by EVA1A via enhancing cellular degradation of HBV components and its potential therapeutic application

Hepatitis B virus (HBV) DNA is much higher during HBeAg-positive chronic HBV infection (EP-CBI) than during HBeAg-negative chronic HBV infection (EN-CBI), although the necroinflammation in liver is minimal and the adaptive immune response is similar in both phases. We previously reported that mRNA levels of EVA1A were higher in EN-CBI patients. In this study, we aimed to investigate whether EVA1A inhibits HBV gene expression and examine the underlying mechanisms. The available cell models for HBV replication and model HBV mice were used to investigate how EVA1A regulates HBV replication and the antiviral activity based on gene therapy. The signaling pathway was determined through RNA sequencing analysis. The results demonstrated that EVA1A can inhibit HBV gene expression in vitro and in vivo. In particular, EVA1A overexpression resulted in accelerated HBV RNA degradation and activation of the PI3K-Akt-mTOR pathway, two processes that directly and indirectly inhibiting HBV gene expression. EVA1A is a promising candidate for treating chronic hepatitis B (CHB). In conclusion, EVA1A is a new host restriction factor that regulates the HBV life cycle via a nonimmune process.

Mitochondrial HIGD1A inhibits hepatitis B virus transcription and replication through the cellular PNKD-NF-κB-NR2F1 nexus.

Hepatitis B Virus (HBV) replication has been reported to be restricted by the intrahepatic host restriction factors and antiviral signaling pathways. The intracellular mechanisms underlying the significant viremia difference among different phases of the natural history chronic HBV infection remain elusive. We herein report that the hypoxia-induced gene domain protein-1a (HIGD1A) was highly expressed in the liver of inactive HBV carriers with low viremia. Ectopic expression of HIGD1A in hepatocyte-derived cells significantly inhibited HBV transcription and replication in a dose-dependent manner, while silence of HIGD1A promoted HBV gene expression and replication. Similar results were also observed in both de novo HBV-infected cell culture model and HBV persistence mouse model. Mechanistically, HIGD1A is located on the mitochondrial inner membrane and activates nuclear factor kappa B (NF-κB) signaling pathway through binding to paroxysmal nonkinesigenic dyskinesia (PNKD), which further enhances the expression of a transcription factor NR2F1 to inhibit HBV transcription and replication. Consistently, knockdown of PNKD or NR2F1 and blockage of NF-κB signaling pathway abrogated the inhibitory effect of HIGD1A on HBV replication. Mitochondrial HIGD1A exploits the PNKD-NF-κB-NR2F1 nexus to act as a host restriction factor of HBV infection. Our study thus shed new lights on the regulation of HBV by hypoxia-related genes and related antiviral strategies.