Deep mutational scanning of hepatitis B virus reveals a mechanism for cis-preferential reverse transcription.

Hepatitis B virus (HBV) is a small double-stranded DNA virus that chronically infects 296 million people. Over half of its compact genome encodes proteins in two overlapping reading frames, and during evolution, multiple selective pressures can act on shared nucleotides. This study combines an RNA-based HBV cell culture system with deep mutational scanning (DMS) to uncouple cis- and trans-acting sequence requirements in the HBV genome. The results support a leaky ribosome scanning model for polymerase translation, provide a fitness map of the HBV polymerase at single-nucleotide resolution, and identify conserved prolines adjacent to the HBV polymerase termination codon that stall ribosomes. Further experiments indicated that stalled ribosomes tether the nascent polymerase to its template RNA, ensuring cis-preferential RNA packaging and reverse transcription of the HBV genome.

Therapeutic potential of co-signaling receptor modulation in hepatitis B.

Reversing CD8+ T cell dysfunction is crucial in treating chronic hepatitis B virus (HBV) infection, yet specific molecular targets remain unclear. Our study analyzed co-signaling receptors during hepatocellular priming and traced the trajectory and fate of dysfunctional HBV-specific CD8+ T cells. Early on, these cells upregulate PD-1, CTLA-4, LAG-3, OX40, 4-1BB, and ICOS. While blocking co-inhibitory receptors had minimal effect, activating 4-1BB and OX40 converted them into antiviral effectors. Prolonged stimulation led to a self-renewing, long-lived, heterogeneous population with a unique transcriptional profile. This includes dysfunctional progenitor/stem-like (TSL) cells and two distinct dysfunctional tissue-resident memory (TRM) populations. While 4-1BB expression is ubiquitously maintained, OX40 expression is limited to TSL. In chronic settings, only 4-1BB stimulation conferred antiviral activity. In HBeAg+ chronic patients, 4-1BB activation showed the highest potential to rejuvenate dysfunctional CD8+ T cells. Targeting all dysfunctional T cells, rather than only stem-like precursors, holds promise for treating chronic HBV infection.

Identification of a Kupffer cell subset capable of reverting the T cell dysfunction induced by hepatocellular priming.

Kupffer cells (KCs) are highly abundant, intravascular, liver-resident macrophages known for their scavenger and phagocytic functions. KCs can also present antigens to CD8+ T cells and promote either tolerance or effector differentiation, but the mechanisms underlying these discrepant outcomes are poorly understood. Here, we used a mouse model of hepatitis B virus (HBV) infection, in which HBV-specific naive CD8+ T cells recognizing hepatocellular antigens are driven into a state of immune dysfunction, to identify a subset of KCs (referred to as KC2) that cross-presents hepatocellular antigens upon interleukin-2 (IL-2) administration, thus improving the antiviral function of T cells. Removing MHC-I from all KCs, including KC2, or selectively depleting KC2 impaired the capacity of IL-2 to revert the T cell dysfunction induced by intrahepatic priming. In summary, by sensing IL-2 and cross-presenting hepatocellular antigens, KC2 overcome the tolerogenic potential of the hepatic microenvironment, suggesting new strategies for boosting hepatic T cell immunity.

The hepatitis B virus receptor.

Hepatitis B virus (HBV) infection affects 240 million people worldwide. A liver-specific bile acid transporter named the sodium taurocholate cotransporting polypeptide (NTCP) has been identified as the cellular receptor for HBV and its satellite, the hepatitis D virus (HDV). NTCP likely acts as a major determinant for the liver tropism and species specificity of HBV and HDV at the entry level. NTCP-mediated HBV entry interferes with bile acid transport in cell cultures and has been linked with alterations in bile acid and cholesterol metabolism in vivo. The human liver carcinoma cell line HepG2, complemented with NTCP, now provides a valuable platform for studying the basic biology of the viruses and developing treatments for HBV infection. This review summarizes critical findings regarding NTCP's role as a viral receptor for HBV and HDV and discusses important questions that remain unanswered.

Immune checkpoint inhibitors in infectious disease.

Following success in cancer immunotherapy, immune checkpoint blockade is emerging as an exciting potential treatment for some infectious diseases, specifically two chronic viral infections, HIV and hepatitis B. Here, we will discuss the function of immune checkpoints, their role in infectious disease pathology, and the ability of immune checkpoint blockade to reinvigorate the immune response. We focus on blockade of programmed cell death 1 (PD-1) to induce durable immune-mediated control of HIV, given that anti-PD-1 can restore function to exhausted HIV-specific T cells and also reverse HIV latency, a long-lived form of viral infection. We highlight several key studies and future directions of research in relation to anti-PD-1 and HIV persistence from our group, including the impact of immune checkpoint blockade on the establishment (AIDS, 2018, 32, 1491), maintenance (PLoS Pathog, 2016, 12, e1005761; J Infect Dis, 2017, 215, 911; Cell Rep Med, 2022, 3, 100766) and reversal of HIV latency (Nat Commun, 2019, 10, 814; J Immunol, 2020, 204, 1242), enhancement of HIV-specific T cell function (J Immunol, 2022, 208, 54; iScience, 2023, 26, 108165), and investigating the effects of anti-PD-1 and anti-CTLA-4 in vivo in people with HIV on ART with cancer (Sci Transl Med, 2022, 14, eabl3836; AIDS, 2021, 35, 1631; Clin Infect Dis, 2021, 73, e1973). Our future work will focus on the impact of anti-PD-1 in vivo in people with HIV on ART without cancer and potential combinations of anti-PD-1 with other interventions, including therapeutic vaccines or antibodies and less toxic immune checkpoint blockers.

Joint host-pathogen genomic analysis identifies hepatitis B virus mutations associated with human NTCP and HLA class I variation.

Evolutionary changes in the hepatitis B virus (HBV) genome could reflect its adaptation to host-induced selective pressure. Leveraging paired human exome and ultra-deep HBV genome-sequencing data from 567 affected individuals with chronic hepatitis B, we comprehensively searched for the signatures of this evolutionary process by conducting "genome-to-genome" association tests between all human genetic variants and viral mutations. We identified significant associations between an East Asian-specific missense variant in the gene encoding the HBV entry receptor NTCP (rs2296651, NTCP S267F) and mutations within the receptor-binding region of HBV preS1. Through in silico modeling and in vitro preS1-NTCP binding assays, we observed that the associated HBV mutations are in proximity to the NTCP variant when bound and together partially increase binding affinity to NTCP S267F. Furthermore, we identified significant associations between HLA-A variation and viral mutations in HLA-A-restricted T cell epitopes. We used in silico binding prediction tools to evaluate the impact of the associated HBV mutations on HLA presentation and observed that mutations that result in weaker binding affinities to their cognate HLA alleles were enriched. Overall, our results suggest the emergence of HBV escape mutations that might alter the interaction between HBV PreS1 and its cellular receptor NTCP during viral entry into hepatocytes and confirm the role of HLA class I restriction in inducing HBV epitope variations.

Epitranscriptomic cytidine methylation of the hepatitis B viral RNA is essential for viral reverse transcription and particle production.

Epitranscriptomic RNA modifications have emerged as important regulators of the fate and function of viral RNAs. One prominent modification, the cytidine methylation 5-methylcytidine (m5C), is found on the RNA of HIV-1, where m5C enhances the translation of HIV-1 RNA. However, whether m5C functionally enhances the RNA of other pathogenic viruses remains elusive. Here, we surveyed a panel of commonly found RNA modifications on the RNA of hepatitis B virus (HBV) and found that HBV RNA is enriched with m5C as well as ten other modifications, at stoichiometries much higher than host messenger RNA (mRNA). Intriguingly, m5C is mostly found on the epsilon hairpin, an RNA element required for viral RNA encapsidation and reverse transcription, with these m5C mainly deposited by the cellular methyltransferase NSUN2. Loss of m5C from HBV RNA due to NSUN2 depletion resulted in a partial decrease in viral core protein (HBc) production, accompanied by a near-complete loss of the reverse transcribed viral DNA. Similarly, mutations introduced to remove the methylated cytidines resulted in a loss of HBc production and reverse transcription. Furthermore, pharmacological disruption of m5C deposition led to a significant decrease in HBV replication. Thus, our data indicate m5C methylations as a critical mediator of the epsilon elements' function in HBV virion production and reverse transcription, suggesting the therapeutic potential of targeting the m5C methyltransfer process on HBV epsilon as an antiviral strategy.

Generation and characterization of mature hepatocyte organoids for liver metabolic studies.

Hepatocyte organoids (HOs) generated in vitro are powerful tools for liver regeneration. However, previously reported HOs have mostly been fetal in nature with low expression levels of metabolic genes characteristic of adult liver functions, hampering their application in studies of metabolic regulation and therapeutic testing for liver disorders. Here, we report development of novel culture conditions that combine optimized levels of triiodothyronine (T3) with the removal of growth factors to enable successful generation of mature hepatocyte organoids (MHOs) of both mouse and human origin with metabolic functions characteristic of adult livers. We show that the MHOs can be used to study various metabolic functions including bile and urea production, zonal metabolic gene expression, and metabolic alterations in both alcoholic liver disease and non-alcoholic fatty liver disease, as well as hepatocyte proliferation, injury and cell fate changes. Notably, MHOs derived from human fetal hepatocytes also show improved hepatitis B virus infection. Therefore, these MHOs provide a powerful in vitro model for studies of human liver physiology and diseases. The human MHOs are potentially also a robust research tool for therapeutic development.

An hepatitis B and D virus infection model using human pluripotent stem cell-derived hepatocytes.

Current culture systems available for studying hepatitis D virus (HDV) are suboptimal. In this study, we demonstrate that hepatocyte-like cells (HLCs) derived from human pluripotent stem cells (hPSCs) are fully permissive to HDV infection across various tested genotypes. When co-infected with the helper hepatitis B virus (HBV) or transduced to express the HBV envelope protein HBsAg, HLCs effectively release infectious progeny virions. We also show that HBsAg-expressing HLCs support the extracellular spread of HDV, thus providing a valuable platform for testing available anti-HDV regimens. By challenging the cells along the differentiation with HDV infection, we have identified CD63 as a potential HDV co-entry factor that was rate-limiting for HDV infection in immature hepatocytes. Given their renewable source and the potential to derive hPSCs from individual patients, we propose HLCs as a promising model for investigating HDV biology. Our findings offer new insights into HDV infection and expand the repertoire of research tools available for the development of therapeutic interventions.

Oxygen-dependent histone lysine demethylase 4 restricts hepatitis B virus replication.

Mammalian cells have evolved strategies to regulate gene expression when oxygen is limited. Hypoxia-inducible factors (HIF) are the major transcriptional regulators of host gene expression. We previously reported that HIFs bind and activate hepatitis B virus (HBV) DNA transcription under low oxygen conditions; however, the global cellular response to low oxygen is mediated by a family of oxygenases that work in concert with HIFs. Recent studies have identified a role for chromatin modifiers in sensing cellular oxygen and orchestrating transcriptional responses, but their role in the HBV life cycle is as yet undefined. We demonstrated that histone lysine demethylase 4 (KDM4) can restrict HBV, and pharmacological or oxygen-mediated inhibition of the demethylase increases viral RNAs derived from both episomal and integrated copies of the viral genome. Sequencing studies demonstrated that KDM4 is a major regulator of the hepatic transcriptome, which defines hepatocellular permissivity to HBV infection. We propose a model where HBV exploits cellular oxygen sensors to replicate and persist in the liver. Understanding oxygen-dependent pathways that regulate HBV infection will facilitate the development of physiologically relevant cell-based models that support efficient HBV replication.

Intrahepatic plasma cells, but not atypical memory B cells, associate with clinical phases of chronic hepatitis B.

Studies have traditionally focused on the role of T cells in chronic hepatitis B (CHB), but recent evidence supports a role for B cells. The enrichment of so-called atypical memory (AtM) B cells, which show reduced signaling and impaired differentiation, is believed to be a characteristic feature of CHB, potentially contributing to the observed dysfunctional anti-HBsAg B-cell responses. Our study, involving 62 CHB patients across clinical phases, identified AtM B cells expressing IFNLR1 and interferon-stimulated genes. Contrary to previous reports, we found relatively low frequencies of AtM B cells in the liver, comparable to peripheral blood. However, liver plasma cell frequencies were significantly higher, particularly during phases with elevated viral loads and liver enzyme levels. Liver plasma cells exhibited signs of active proliferation, especially in the immune active phase. Our findings suggest a potential role for plasma cells, alongside potential implications and consequences of local proliferation, within the livers of CHB patients. While the significance of AtM B cells remains uncertain, further investigation is warranted to determine their responsiveness to interferons and their role in CHB.

The in vitro replication phenotype of hepatitis B virus (HBV) splice variants Sp3 and Sp9 and their impact on wild-type HBV replication.

Prior to nuclear export, the hepatitis B virus (HBV) pregenomic RNA may be spliced by the host cell spliceosome to form shorter RNA sequences known as splice variants. Due to deletions in the open reading frames, splice variants may encode novel fusion proteins. Although not essential for HBV replication, the role of splice variants and their novel fusion proteins largely remains unknown. Some splice variants and their encoded novel fusion proteins have been shown to impair or promote wild-type HBV replication in vitro, and although splice variants Sp3 and Sp9 are two of the most common splice variants identified to date, their in vitro replication phenotype and their impact on wild-type HBV replication are unclear. Here, we utilize greater than genome-length Sp3 and Sp9 constructs to investigate their replication phenotype in vitro, and their impact on wild-type HBV replication. We show that Sp3 and Sp9 were incapable of autonomous replication, which was rescued by providing the polymerase and core proteins in trans. Furthermore, we showed that Sp3 had no impact on wild-type HBV replication, whereas Sp9 strongly reduced wild-type HBV replication in co-transfection experiments. Knocking out Sp9 novel precore-surface and core-surface fusion protein partially restored replication, suggesting that these proteins contributed to suppression of wild-type HBV replication, providing further insights into factors regulating HBV replication in vitro. IMPORTANCE: The role of hepatitis B virus (HBV) splice variants in HBV replication and pathogenesis currently remains largely unknown. However, HBV splice variants have been associated with the development of hepatocellular carcinoma, suggesting a role in HBV pathogenesis. Several in vitro co-transfection studies have shown that different splice variants have varying impacts on wild-type HBV replication, perhaps contributing to viral persistence. Furthermore, all splice variants are predicted to produce novel fusion proteins. Sp1 hepatitis B splice protein contributes to liver disease progression and apoptosis; however, the function of other HBV splice variant novel fusion proteins remains largely unknown. We show that Sp9 markedly impairs HBV replication in a cell culture co-transfection model, mediated by expression of Sp9 novel fusion proteins. In contrast, Sp3 had no effect on wild-type HBV replication. Together, these studies provide further insights into viral factors contributing to regulation of HBV replication.

SARS-CoV-2 nsp13 suppresses hepatitis B virus replication by targeting cccDNA transcription.

SARS-CoV-2 nonstructural protein 13 (nsp13) has been shown to selectively suppress the transcription of episomal DNA while sparing chromosomal DNA. Hepatitis B Virus (HBV) harbors covalently closed circular DNA (cccDNA), a form of viral episomal DNA found within infected hepatocyte nuclei. The persistence of cccDNA is the major cause of chronic HBV infection. In this study, we investigated the impact of SARS-CoV-2 nsp13 on HBV replication, particularly in the context of cccDNA. Our findings demonstrate that nsp13 effectively hinders HBV replication by suppressing the transcription of HBV cccDNA, both in vitro and in vivo. Additionally, we observed that SARS-CoV-2 nsp13 binds to HBV cccDNA and its NTPase and helicase activities contribute significantly to inhibiting HBV replication. Furthermore, our screening identified the interaction between nsp13 and structural maintenance of chromosomes 4, opening new avenues for future mechanistic inquiries. This study presents the evidence suggesting the potential utilization of SARS-CoV-2 nsp13 as a strategy to impede HBV replication by specifically targeting cccDNA. These findings provide a proof of concept for exploring nsp13 as a prospective approach in combating HBV infection. IMPORTANCE: To effectively combat hepatitis B virus (HBV), it is imperative to develop potent antiviral medications targeting covalently closed circular DNA (cccDNA). Our investigation aimed to assess the impact of SARS-CoV-2 nsp13 on HBV replication across diverse HBV models, confirming its ability to significantly reduce several HBV replication markers. Additionally, our identification of the interaction between nsp13 and SMC4 opens the door for further mechanistic exploration. This marks a paradigm shift in our approach to HBV antiviral therapy, introducing an entirely novel perspective. Our findings propose a novel strategy for developing anti-HBV drugs that specifically target HBV cccDNA.

The impact of HBx protein on mitochondrial dynamics and associated signaling pathways strongly depends on the hepatitis B virus genotype.

Chronic hepatitis B virus (HBV) infections are strongly associated with liver cirrhosis, inflammation, and hepatocellular carcinoma. In this context, the viral HBx protein is considered as a major factor influencing HBV-associated pathogenesis through deregulation of multiple cellular signaling pathways and is therefore a potential target for prognostic and therapeutic applications. However, HBV-associated pathogenesis differs significantly between genotypes, with the relevant factors and in particular the contribution of the genetic diversity of HBx being largely unknown. To address this question, we studied the specific genotype-dependent impact of HBx on cellular signaling pathways, focusing in particular on morphological and functional parameters of mitochondria. To exclusively investigate the impact of HBx of different genotypes on integrity and function of mitochondria in the absence of additional viral factors, we overexpressed HBx in Huh7 or HepG2 cells. Key signaling pathways were profiled by kinome analysis and correlated with expression levels of mitochondrial and pathogenic markers. Conclusively, HBx of genotypes A and G caused strong disruption of mitochondrial morphology alongside an induction of PTEN-induced putative kinase 1/Parkin-mediated mitophagy. These effects were only moderately dysregulated by genotypes B and E, whereas genotypes C and D exhibit an intermediate effect in this regard. Accordingly, changes in mitochondrial membrane potential and elevated reactive oxygen species production were associated with the HBx-mediated dysfunction among different genotypes. Also, genotype-related differences in mitophagy induction were identified and indicated that HBx-mediated changes in the mitochondria morphology and function strongly depend on the genotype. This indicates a relevant role of HBx in the process of genotype-dependent liver pathogenesis of HBV infections and reveals underlying mechanisms.IMPORTANCEThe hepatitis B virus is the main cause of chronic liver disease worldwide and differs in terms of pathogenesis and clinical outcome among the different genotypes. Furthermore, the viral HBx protein is a known factor in the progression of liver injury by inducing aberrant mitochondrial structures and functions. Consequently, the selective removal of dysfunctional mitochondria is essential to maintain overall cellular homeostasis and cell survival. Consistent with the intergenotypic difference of HBV, our data reveal significant differences regarding the impact of HBx of different genotypes on mitochondrial dynamic and function and thereby on radical oxygen stress levels within the cell. We subsequently observed that the induction of mitophagy differs significantly across the heterogenetic HBx proteins. Therefore, this study provides evidence that HBx-mediated changes in the mitochondria dynamics and functionality strongly depend on the genotype of HBx. This highlights an important contribution of HBx in the process of genotype-dependent liver pathogenesis.

Tripartite motif-containing protein 21 is involved in IFN-γ-induced suppression of hepatitis B virus by regulating hepatocyte nuclear factors.

The antiviral role of the tripartite motif-containing (TRIM) protein family , a member of the E3-ubiquitin ligase family, has recently been actively studied. Hepatitis B virus (HBV) infection is a major contributor to liver diseases; however, the host factors regulated by cytokine-inducible TRIM21 to suppress HBV remain unclear. In this study, we showed the antiviral efficacy of TRIM21 against HBV in hepatoma cell lines, primary human hepatocytes isolated from patient liver tissues, and mouse model. Using TRIM21 knock-out cells, we confirmed that the antiviral effects of interferon-gamma, which suppress HBV replication, are diminished when TRIM21 is deficient. Northern blot analysis confirmed a reduction of HBV RNA levels by TRIM21. Using Luciferase reporter assay, we also discovered that TRIM21 decreases the activity of HBV enhancers, which play a crucial role in covalently closed circular DNA transcription. The participation of the RING domain and PRY-SPRY domain in the anti-HBV effect of TRIM21 was demonstrated through experiments using deletion mutants. We identified a novel interaction between TRIM21 and hepatocyte nuclear factor 4α (HNF4α) through co-immunoprecipitation assay. More specifically, ubiquitination assay revealed that TRIM21 promotes ubiquitin-mediated proteasomal degradation of HNF4α. HNF1α transcription is down-regulated as a result of the degradation of HNF4α, an activator for the HNF1α promoter. Therefore, the reduction of key HBV enhancer activators, HNF4α and HNF1α, by TRIM21 resulted in a decline in HBV transcription, ultimately leading to the inhibition of HBV replication.IMPORTANCEDespite extensive research efforts, a definitive cure for chronic hepatitis B remains elusive, emphasizing the persistent importance of this viral infection as a substantial public health concern. Although the risks associated with hepatitis B virus (HBV) infection are well known, host factors capable of suppressing HBV are largely uncharacterized. This study elucidates that tripartite motif-containing protein 21 (TRIM21) suppresses HBV transcription and consequently inhibits HBV replication by downregulating the hepatocyte nuclear factors, which are host factors associated with the HBV enhancers. Our findings demonstrate a novel anti-HBV mechanism of TRIM21 in interferon-gamma-induced anti-HBV activity. These findings may contribute to new strategies to block HBV.

Foxa deficiency restricts hepatitis B virus biosynthesis through epigenic silencing.

In the hepatis B virus (HBV) transgenic mouse model of chronic infection, the forkhead box protein A/hepatocyte nuclear factor 3 (Foxa/HNF3) family of pioneer transcription factors are required to support postnatal viral demethylation and subsequent HBV transcription and replication. Liver-specific Foxa-deficient mice with hepatic expression of only Foxa3 do not support HBV replication but display biliary epithelial hyperplasia with bridging fibrosis. However, liver-specific Foxa-deficient mice with hepatic expression of only Foxa1 or Foxa2 also successfully restrict viral transcription and replication but display only minimal alterations in liver physiology. These observations suggest that the level of Foxa activity, rather than the combination of specific Foxa genes, is a key determinant of HBV biosynthesis. Together, these findings suggest that targeting Foxa activity could lead to HBV DNA methylation and transcriptional inactivation, resulting in the resolution of chronic HBV infections that are responsible for approximately one million deaths annually worldwide. IMPORTANCE: The current absence of curative therapies capable of resolving chronic hepatis B virus (HBV) infection is a major clinical problem associated with considerable morbidity and mortality. The small viral genome limits molecular targets for drug development, suggesting that the identification of cellular factors essential for HBV biosynthesis may represent alternative targets for therapeutic intervention. Genetic Foxa deficiency in the neonatal liver of HBV transgenic mice leads to the transcriptional silencing of viral DNA by CpG methylation without affecting viability or displaying an obvious phenotype. Therefore, limiting liver Foxa activity therapeutically may lead to the methylation of viral covalently closed circular DNA (cccDNA), resulting in its transcriptional silencing and ultimately the resolution of chronic HBV infection.

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.

Capsid assembly is critical in the hepatitis B virus (HBV) life cycle, mediated by the viral core protein. Capsid assembly is the target for new anti-viral therapeutics known as capsid assembly modulators (CAMs) of which the CAM-aberrant (CAM-A) class induces aberrant shaped core protein structures and leads to hepatocyte cell death. This study aimed to identify the mechanism of action of CAM-A modulators leading to HBV-infected hepatocyte elimination where CAM-A-mediated hepatitis B surface antigen (HBsAg) reduction was evaluated in a stable HBV replicating cell line and in AAV-HBV-transduced C57BL/6, C57BL/6 SCID, and HBV-infected chimeric mice with humanized livers. Results showed that in vivo treatment with CAM-A modulators induced pronounced reductions in hepatitis B e antigen (HBeAg) and HBsAg, associated with a transient alanine amino transferase (ALT) increase. Both HBsAg and HBeAg reductions and ALT increase were delayed in C57BL/6 SCID and chimeric mice, suggesting that adaptive immune responses may indirectly contribute. However, CD8+ T cell depletion in transduced wild-type mice did not impact antigen reduction, indicating that CD8+ T cell responses are not essential. Transient ALT elevation in AAV-HBV-transduced mice coincided with a transient increase in endoplasmic reticulum stress and apoptosis markers, followed by detection of a proliferation marker. Microarray data revealed antigen presentation pathway (major histocompatibility complex class I molecules) upregulation, overlapping with the apoptosis. Combination treatment with HBV-specific siRNA demonstrated that CAM-A-mediated HBsAg reduction is dependent on de novo core protein translation. To conclude, CAM-A treatment eradicates HBV-infected hepatocytes with high core protein levels through the induction of apoptosis, which can be a promising approach as part of a regimen to achieve functional cure. IMPORTANCE: 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.

Ten-eleven translocation (Tet) methylcytosine dioxygenase-dependent viral DNA demethylation mediates in vivo hepatitis B virus (HBV) biosynthesis.

Liver-specific ten-eleven translocation (Tet) methylcytosine dioxygenases 2 and 3 (Tet2 plus Tet3)-deficient hepatitis B virus (HBV) transgenic mice fail to support viral biosynthesis. The levels of viral transcription and replication intermediates are dramatically reduced. Hepatitis B core antigen is only observed in a very limited number of pericentral hepatocytes in a pattern that is similar to glutamate-ammonia ligase (Glul), a ß-catenin target gene. HBV transcript abundance in adult Tet-deficient mice resembles that observed in wild-type neonatal mice. Furthermore, the RNA levels of several ß-catenin target genes including Glul, Lhpp, Notun, Oat, Slc1a2, and Tbx3 in Tet-deficient mice were also similar to that observed in wild-type neonatal mice. As HBV transcription is regulated by ß-catenin, these findings support the suggestion that neonatal Tet deficiency might limit ß-catenin target gene expression, limiting viral biosynthesis. Additionally, HBV transgene DNA displays increased 5-methylcytosine (5mC) frequency at CpG sequences consistent with neonatal Tet deficiency being responsible for decreased developmental viral DNA demethylation mediated by 5mC oxidation to 5-hydroxymethylcytosine, a process that might be responsible for the reduction in cellular ß-catenin target gene expression and viral transcription and replication.IMPORTANCEChronic hepatitis B virus (HBV) infection causes significant worldwide morbidity and mortality. There are no curative therapies available to resolve chronic HBV infections, and the small viral genome limits molecular targets for drug development. An alternative approach to drug development is to target cellular genes essential for HBV biosynthesis. In the liver, ten-eleven translocation (Tet) genes encode cellular enzymes that are not essential for postnatal mouse development but represent essential activities for viral DNA demethylation and transcription. Consequently, Tet inhibitors may potentially be developed into therapeutic agents capable of inducing and/or maintaining HBV covalently closed circular DNA methylation, resulting in transcriptional silencing and the resolution of chronic viral infection.

Small hepatitis B virus surface antigen (SHBs) induces dyslipidemia by suppressing apolipoprotein-AII expression through ER stress-mediated modulation of HNF4α and C/EBPγ.

Persistent infection with hepatitis B virus (HBV) often leads to disruptions in lipid metabolism. Apolipoprotein AII (apoAII) plays a crucial role in lipid metabolism and is implicated in various metabolic disorders. However, whether HBV could regulate apoAII and contribute to HBV-related dyslipidemia and the underlying mechanism remain unclear. This study revealed significant reductions in apoAII expression in HBV-expressing cell lines, the serum, and liver tissues of HBV-transgenic mice. The impact of HBV on apoAII is related to small hepatitis B virus surface antigen (SHBs). Overexpression of SHBs decreased apoAII levels in SHBs-expressing hepatoma cells, transgenic mice, and the serum of HBV-infected patients, whereas suppression of SHBs increased apoAII expression. Mechanistic investigations demonstrated that SHBs repressed the apoAII promoter activity through a HNF4α- and C/EBPγ-dependent manner; SHBs simultaneously upregulated C/EBPγ and downregulated HNF4α by inhibiting the PI3K/AKT signaling pathway through activating endoplasmic reticulum (ER) stress. Serum lipid profile assessments revealed notable decreases in high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), and triglycerides (TG) in SHBs-transgenic mice compared to control mice. However, concurrent overexpression of apoAII in these mice effectively counteracted these reductions in lipid levels. In HBV patients, SHBs levels were negatively correlated with serum levels of HDL-C, LDL-C, TC, and TG, whereas apoAII levels positively correlated with lipid content. This study underscores that SHBs contributes to dyslipidemia by suppressing the PI3K/AKT pathway via inducing ER stress, leading to altered expression of HNF4α and C/EBPγ, and subsequently reducing apoAII expression.IMPORTANCEThe significance of this study lies in its comprehensive examination of how the hepatitis B virus (HBV), specifically through its small hepatitis B virus surface antigen (SHBs), impacts lipid metabolism-a key aspect often disrupted by chronic HBV infection. By elucidating the role of SHBs in regulating apolipoprotein AII (apoAII), a critical player in lipid processes and associated metabolic disorders, this research provides insights into the molecular pathways contributing to HBV-related dyslipidemia. Discovering that SHBs downregulates apoAII through mechanisms involving the repression of the apoAII promoter via HNF4α and C/EBPγ, and the modulation of the PI3K/AKT signaling pathway via endoplasmic reticulum (ER) stress, adds critical knowledge to HBV pathogenesis. The research also shows an inverse correlation between SHBs expression and key lipid markers in HBV-infected individuals, suggesting that apoAII overexpression could counteract the lipid-altering effects of SHBs, offering new avenues for understanding and managing the metabolic implications of HBV infection.

HBV-infected hepatocellular carcinoma can be robustly classified into three clinically relevant subgroups by a novel analytical protocol.

Liver cancer is the third leading cause of cancer-related death worldwide, and hepatocellular carcinoma (HCC) accounts for a relatively large proportion of all primary liver malignancies. Among the several known risk factors, hepatitis B virus (HBV) infection is one of the important causes of HCC. In this study, we demonstrated that the HBV-infected HCC patients could be robustly classified into three clinically relevant subgroups, i.e. Cluster1, Cluster2 and Cluster3, based on consistent differentially expressed mRNAs and proteins, which showed better generalization. The proposed three subgroups showed different molecular characteristics, immune microenvironment and prognostic survival characteristics. The Cluster1 subgroup had near-normal levels of metabolism-related proteins, low proliferation activity and good immune infiltration, which were associated with its good liver function, smaller tumor size, good prognosis, low alpha-fetoprotein (AFP) levels and lower clinical stage. In contrast, the Cluster3 subgroup had the lowest levels of metabolism-related proteins, which corresponded with its severe liver dysfunction. Also, high proliferation activity and poor immune microenvironment in Cluster3 subgroup were associated with its poor prognosis, larger tumor size, high AFP levels, high incidence of tumor thrombus and higher clinical stage. The characteristics of the Cluster2 subgroup were between the Cluster1 and Cluster3 groups. In addition, MCM2-7, RFC2-5, MSH2, MSH6, SMC2, SMC4, NCPAG and TOP2A proteins were significantly upregulated in the Cluster3 subgroup. Meanwhile, abnormally high phosphorylation levels of these proteins were associated with high levels of DNA repair, telomere maintenance and proliferative features. Therefore, these proteins could be identified as potential diagnostic and prognostic markers. In general, our research provided a novel analytical protocol and insights for the robust classification, treatment and prevention of HBV-infected HCC.