Interferon-γ and Tumor Necrosis Factor-α Produced by T Cells Reduce the HBV Persistence Form, cccDNA, Without Cytolysis

Molecular epidemiology of hepatitis B virus (HBV) in Ethiopia: A review article

Hepatitis B virus (HBV) belongs to the family Hepadnaviridae and is the smallest human DNA virus, with a genome that is only 3200 nucleotides long. The absence of proofreading function in HBV reverse transcriptase provides a wide range of genetic variants for targeted outgrowth at different stages of infection. A number of sub genotypes and ten HBV genotypes (A through J) have been identified through analyses of the divergence of HBV genomic sequences. Numerous clinical outcomes, including the emergence of chronicity, the course of the disease, the effectiveness of treatment, and the response to vaccination, have been related to differences in genotype between HBV isolates. There are just seven studies that have been done in Ethiopia that examine the molecular epidemiology of HBV. Moreover, these studies haven't been compiled and reviewed yet. In this review, we looked at the genetic diversity and molecular epidemiology of HBV, the relationship between HBV genotypes and clinical outcomes, the immunopathogenesis of HBV, and finally the molecular epidemiology of HBV in Ethiopia. PubMed, Embase, and Google Scholar search engines were used to find relevant articles for the review. By using HBV genotyping, clinicians can better tailor vaccination decisions and antiviral therapy for patients with chronic hepatitis B who are more likely to experience the disease's progression.

Association between autoimmune liver diseases and chronic hepatitis B: A multivariable Mendelian randomization study in European population

BACKGROUND

Observational studies have indicated a link between autoimmune liver diseases (AILD) and chronic hepatitis B (CHB) through observational studies. The association between AILD and CHB remains indeterminate.

METHODS

A two-sample Mendelian randomization (MR) analysis was conducted to scrutinize the causal nexus between AILD and CHB utilizing summary statistics derived from extensive genome-wide association studies (GWASs) in European populations. The primary statistical methodology employed was the inverse variance-weighted (IVW) method to deduce the causal connection of AILD on CHB. This study incorporated primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and autoimmune hepatitis (AIH) as subtypes of AILD. Additionally, we conducted a multivariable MR (MVMR) analysis to account for the potential confounding effects of smoking, alcohol consumption, body mass index (BMI), and some autoimmune diseases.

RESULTS

Our MR investigation encompassed a cohort of 725,816 individuals. The MR analysis revealed that genetically predicted PSC significantly correlated with a reduced risk of CHB (IVW OR = 0.857; 95%CI: 0.770-0.953, P = 0.005). Conversely, the reverse MR analysis suggested that genetic susceptibility to PSC might not modify the risk of CHB (IVW OR = 1.004; 95% CI: 0.958-1.053, P = 0.866). Genetically proxied PBC and AIH exhibited no discernible causal association with CHB in the MR analysis using the IVW method (P = 0.583; P = 0.425). The MVMR analysis still indicated a decreased risk of CHB associated with PSC (OR = 0.853, P = 0.003).

CONCLUSION

Our study elucidates a causal relationship between PSC and a diminished risk of CHB.

An allosteric inhibitor of sirtuin 2 blocks hepatitis B virus covalently closed circular DNA establishment and its transcriptional activity

296 million people worldwide are predisposed to developing severe end-stage liver diseases due to chronic hepatitis B virus (HBV) infection. HBV forms covalently closed circular DNA (cccDNA) molecules that persist as episomal DNA in the nucleus of infected hepatocytes and drive viral replication. Occasionally, the HBV genome becomes integrated into host chromosomal DNA, a process that is believed to significantly contribute to circulating HBsAg levels and HCC development. Neither cccDNA accumulation nor expression from integrated HBV DNA are directly targeted by current antiviral treatments. In this study, we investigated the antiviral properties of a newly described allosteric modulator, FLS-359, that targets sirtuin 2 (SIRT2), an NAD+-dependent deacylase. Our results demonstrate that SIRT2 modulation by FLS-359 and by other tool compounds inhibits cccDNA synthesis following de novo infection of primary human hepatocytes and HepG2 (C3A)-NTCP cells, and FLS-359 substantially reduces cccDNA recycling in HepAD38 cells. While pre-existing cccDNA is not eradicated by short-term treatment with FLS-359, its transcriptional activity is substantially impaired, likely through inhibition of viral promoter activities. Consistent with the inhibition of viral transcription, HBsAg production by HepG2.2.15 cells, which contain integrated HBV genomes, is also suppressed by FLS-359. Our study provides further insights on SIRT2 regulation of HBV infection and supports the development of potent SIRT2 inhibitors as HBV antivirals.

Intracellular Host Restriction of Hepatitis B Virus Replication

The hepatitis B virus (HBV) infects hepatocytes and hijacks host cellular mechanisms for its replication. Host proteins can be frontline effectors of the cell's defense and restrict viral replication by impeding multiple steps during its intracellular lifecycle. This review summarizes many of the well-described restriction factors, their mechanisms of restriction, and counteractive measures of HBV, with a special focus on viral transcription. We discuss some of the limitations and knowledge gaps about the restriction factors, highlighting how these factors may be harnessed to facilitate therapeutic strategies against HBV.

Polysaccharide of Atractylodes macrocephala Koidz alleviates LPS-induced proliferation, differentiation inhibition and excessive apoptosis in chicken embryonic myogenic cells

BACKGROUND

Lipopolysaccharide (LPS) can induce systemic inflammation and affect the growth and development of poultry. As a kind of traditional Chinese medicine, polysaccharide of Atractylodes macrocephala Koidz (PAMK) can effectively improve the growth performance of animals and improve the immunity of animal bodies.

OBJECTIVES

The purpose of this study was to investigate the effects of PAMK on LPS-induced inflammatory response, proliferation, differentiation and apoptosis of chicken embryonic myogenic cells.

METHODS

We used chicken embryonic myogenic cells as a model by detecting EdU/MYHC immunofluorescence, the expression of inflammation, proliferation, differentiation-related genes and proteins and the number of apoptotic cells in the condition of adding LPS, PAMK, belnacasan (an inhibitor of Caspase1) or their combinations.

RESULTS

The results showed that LPS stimulation increased the expression of inflammatory factors, inhibited proliferation and differentiation, and excessive apoptosis in chicken embryonic myogenic cells, and PAMK alleviated these adverse effects induced by LPS. After the addition of belnacasan (inhibitor of Caspase1), apoptosis in myogenic cells was inhibited, and therefore, the number of apoptotic cells and the expression of pro-apoptotic genes Caspase1 and Caspase3 were increased. In addition, belnacasan inhibited the increased expression of inflammatory factors, inhibited proliferation, differentiation and excessive apoptosis in chicken embryonic myogenic cells induced by LPS.

CONCLUSIONS

This study provides a theoretical basis for further exploring the mechanism of action of PAMK and exogenous LPS on chicken embryonic myogenic cells and lays the foundation for the development and application of green feed additives in animal husbandry industry.

Early application of IFNγ mediated the persistence of HBV in an HBV mouse model

The antiviral activity of interferon gamma (IFNγ) against hepatitis B virus (HBV) was demonstrated both in vivo and in vitro in a previous study. IFNγ can suppress HBV replication by accelerating the decay of replication-competent nucleocapsids of HBV. However, in this study, we found that the direct application of the mouse IFNγ (mIFNγ) expression plasmid to the liver of an HBV hydrodynamic injection (HI) mouse model led to the persistence of HBV, as indicated by sustained HBsAg and HBeAg levels in the serum as well as an increased percentage of the HBsAg positive mice, whereas the level of HBV DNA in the serum and the expression of HBcAg in the liver were inhibited at the early stage after HI. Meanwhile, we found that the productions of both HBcAb and HBsAb were suppressed after the application of mIFNγ. In addition, we found that HBV could be effectively inhibited in mice immunized with HBsAg expression plasmid before the application of mIFNγ. Furthermore, mIFNγ showed antiviral effect and promoted the production of HBsAb when the mice subjected to the core-null HBV plasmid. These results indicate that the application of mIFNγ in the HBV HI mouse model, the mice showed defective HBcAg-specific immunity that impeded the production of HBcAb and HBsAb, finally allowing the persistence of the virus. Moreover, IFNγ-induced negative immune regulatory factors also play an important role in virus persistence.

Antiviral Therapy of Chronic Hepatitis B Virus between Present and Future

Background/Objectives: The objective of this study was to analyze the results of clinical trials regarding long-term antiviral therapies in chronic hepatitis with HBV to compare current therapeutic protocols and to analyze the results of preliminary studies with new antiviral therapies for HBV. Methods: Clinical studies and meta-analyses from PubMed, Google Scholar, and Research Gate from 2011 to 2024 were analyzed on patients undergoing chronic antiviral therapy for HBV, and a retrospective observational study performed in our clinic on a group of 76 patients undergoing chronic therapy with entecavir was presented. Also, a summary of the results of preliminary studies with various innovative antiviral molecules for HBV was performed. Results: The results of extensive clinical trials reveal that current therapies for chronic HBV are well tolerated and maintain good viral suppression if the patient is adherent to therapy. Innovative therapies aim to eliminate HBsAg and, thus, significantly shorten the duration of treatment, and the preliminary results of the studies are promising. Conclusions: Being an asymptomatic condition that requires life-long therapy, adherence to therapy is a real problem. Also, the risk of decompensation of liver cirrhosis and adenocarcinoma remains important in these patients. Future research is needed to perfect some antiviral therapy schemes that shorten the treatment period but also decrease the rate of progression towards decompensated cirrhosis and liver adenocarcinoma.

A Dual-domain Engineered Antibody for Efficient HBV Suppression and Immune Responses Restoration

Chronic hepatitis B (CHB) remains a major public health concern because of the inefficiency of currently approved therapies in clearing the hepatitis B surface antigen (HBsAg). Antibody-based regimens have demonstrated potency regarding virus neutralization and HBsAg clearance. However, high dosages or frequent dosing are required for virologic control. In this study, a dual-domain-engineered anti-hepatitis B virus (HBV) therapeutic antibody 73-DY is developed that exhibits significantly improved efficacy regarding both serum and intrahepatic viral clearance. In HBV-tolerant mice, administration of a single dose of 73-DY at 2 mg kg-1 is sufficient to reduce serum HBsAg by over 3 log10 IU mL-1 and suppress HBsAg to < 100 IU mL-1 for two weeks, demonstrating a dose-lowering advantage of at least tenfold. Furthermore, 10 mg kg-1 of 73-DY sustainably suppressed serum viral levels to undetectable levels for ≈ 2 weeks. Molecular analyses indicate that the improved efficacy exhibited by 73-DY is attributable to the synergy between fragment antigen binding (Fab) and fragment crystallizable (Fc) engineering, which conferred sustained viral suppression and robust viral eradication, respectively. Long-term immunotherapy with reverse chimeric 73-DY facilitated the restoration of anti-HBV immune responses. This study provides a foundation for the development of next-generation antibody-based CHB therapies.

Elimination of the hepatitis B virus: A goal, a challenge

The hepatitis B elimination is a goal proposed by the WHO to be achieved by 2030 through the adoption of synergistic measures for the prevention and chronic HBV infection treatment. Complete cure is characterized by the HBV elimination from the body and is the goal of the chronic hepatitis B treatment, which once achieved, will enable the hepatitis B elimination. This, today, has been a scientific challenge. The difficulty in achieving a complete cure is due to the indefinite maintenance of a covalently closed episomal circular DNA (cccDNA) reservoir and the maintenance and persistence of an insufficient and dysfunctional immune response in chronically infected patients. Among the measures adopted to eliminate hepatitis B, two have the potential to directly interfere with the virus cycle, but with limited effect on HBV control. These are conventional vaccines-blocking transmission and antiviral therapy-inhibiting replication. Vaccines, despite their effectiveness in protecting against horizontal transmission and preventing mother-to-child vertical transmission, have no effect on chronic infection or potential to eliminate the virus. Treatment with antivirals suppresses viral replication, but has no curative effect, as it has no action against cccDNA. Therapeutic vaccines comprise an additional approach in the chronic infection treatment, however, they have only a modest effect on the immune system, enhancing it temporarily. This manuscript aims to address (1) the cccDNA persistence in the hepatocyte nucleus and the immune response dysfunction in chronically infected individuals as two primary factors that have hampered the treatment and HBV elimination from the human body; (2) the limitations of antiviral therapy and therapeutic vaccines, as strategies to control hepatitis B; and (3) the possibly promising therapeutic approaches for the complete cure and elimination of hepatitis B.

A therapeutic hepatitis B mRNA vaccine with strong immunogenicity and persistent virological suppression

Here we report on the development and comprehensive evaluations of an mRNA vaccine for chronic hepatitis B (CHB) treatment. In two different HBV carrier mouse models generated by viral vector-mediated HBV transfection (pAAV-HBV1.2 and rAAV8-HBV1.3), this vaccine demonstrates sufficient and persistent virological suppression, and robust immunogenicity in terms of induction of strong innate immune activation, high-level virus-specific antibodies, memory B cells and T cells. mRNA platform therefore holds prospects for therapeutic vaccine development to combat CHB.

Cytokines Expression Compared to the Determinants of Cellular Apoptosis Prominently Attributes to the Deleterious Effects of 'A' Determinant Surface Gene Mutations in HBV Transfected Hepatoma Cell Line

BACKGROUND

Previous studies have explored the role of AKT protein in anti-apoptotic/proliferative activities. However, there has been a lack of information regarding the role of Akt in association with cytokines expression in HBV-related (wild type HBV and HBV with mutations of 'a' determinant region) studies either in the case of HBV infection or in transfected hepatoma cells. The present study tries to determine the role of Akt and cytokines expression in the presence of small surface gene mutants in the hepatoma cell line.

METHODS

Mutations of 'a' determinant region, viz. sA128V and sG145R, were created in wild-type pHBV1.3 by site-directed mutagenesis and transfected in hepatoma cell line. Secretory levels of HBsAg in the wild type as well as in both the mutants were analyzed by ELISA. Apoptotic analysis of transfected cells was studied by flow cytometry. Expression analysis of Akt and cytokines (TNF-alpha, IL-6, and IFN-gamma) was done by qPCR.

RESULTS

The presence of significantly more alive cells in sG145R than sA128V transfected cells may be due to the up-regulation of the Akt gene expression. Cytokines expression was nearly similar between sA128V and wild-type pHBV1.3 transfected cells. Presence of sG145R showed dramatically high cytokines expression than sA128V and wild-type pHBV1.3.

CONCLUSION

Cytokines expression predominantly contributes to the detrimental effects associated with the 'a' determinant region mutations particularly sG145R mutant. It may also be inferred that mechanisms associated with cellular apoptosis apparently do not play any major role to assign the 'a' determinant small surface gene mutation(s) for their pathological outcome.

Mechanism of interferon alpha therapy for chronic hepatitis B and potential approaches to improve its therapeutic efficacy

Hepatitis B virus (HBV) chronically infects 296 million people worldwide and causes more than 820,000 deaths annually due to cirrhosis and hepatocellular carcinoma. Current standard-of-care medications for chronic hepatitis B (CHB) include nucleos(t)ide analogue (NA) viral DNA polymerase inhibitors and pegylated interferon alpha (PEG-IFN-α). NAs can efficiently suppress viral replication and improve liver pathology, but not eliminate or inactivate HBV covalently closed circular DNA (cccDNA). CCC DNA is the most stable HBV replication intermediate that exists as a minichromosome in the nucleus of infected hepatocyte to transcribe viral RNA and support viral protein translation and genome replication. Consequentially, a finite duration of NA therapy rarely achieves a sustained off-treatment suppression of viral replication and life-long NA treatment is most likely required. On the contrary, PEG-IFN-α has the benefit of finite treatment duration and achieves HBsAg seroclearance, the indication of durable immune control of HBV replication and functional cure of CHB, in approximately 5% of treated patients. However, the low antiviral efficacy and poor tolerability limit its use. Understanding how IFN-α suppresses HBV replication and regulates antiviral immune responses will help rational optimization of IFN therapy and development of novel immune modulators to improve the rate of functional cure. This review article highlights mechanistic insight on IFN control of HBV infection and recent progress in development of novel IFN regimens, small molecule IFN mimetics and combination therapy of PEG-IFN-α with new direct-acting antivirals and therapeutic vaccines to facilitate the functional cure of CHB.

A small molecule iCDM-34 identified by in silico screening suppresses HBV DNA through activation of aryl hydrocarbon receptor

IFN-alpha have been reported to suppress hepatitis B virus (HBV) cccDNA via APOBEC3 cytidine deaminase activity through interferon signaling. To develop a novel anti-HBV drug for a functional cure, we performed in silico screening of the binding compounds fitting the steric structure of the IFN-alpha-binding pocket in IFNAR2. We identified 37 compounds and named them in silico cccDNA modulator (iCDM)-1-37. We found that iCDM-34, a new small molecule with a pyrazole moiety, showed anti-HCV and anti-HBV activities. We measured the anti-HBV activity of iCDM-34 dependent on or independent of entecavir (ETV). iCDM-34 suppressed HBV DNA, pgRNA, HBsAg, and HBeAg, and also clearly exhibited additive inhibitory effects on the suppression of HBV DNA with ETV. We confirmed metabolic stability of iCDM-34 was stable in human liver microsomal fraction. Furthermore, anti-HBV activity in human hepatocyte-chimeric mice revealed that iCDM-34 was not effective as a single reagent, but when combined with ETV, it suppressed HBV DNA compared to ETV alone. Phosphoproteome and Western blotting analysis showed that iCDM-34 did not activate IFN-signaling. The transcriptome analysis of interferon-stimulated genes revealed no increase in expression, whereas downstream factors of aryl hydrocarbon receptor (AhR) showed increased levels of the expression. CDK1/2 and phospho-SAMHD1 levels decreased under iCDM-34 treatment. In addition, AhR knockdown inhibited anti-HCV activity of iCDM-34 in HCV replicon cells. These results suggest that iCDM-34 decreases the phosphorylation of SAMHD1 through CDK1/2, and suppresses HCV replicon RNA, HBV DNA, and pgRNA formation.

Comparative effectiveness of tenofovir versus entecavir in patients with hepatitis B virus-related cirrhosis in Taiwan: a retrospective cohort study

Background: Tenofovir and entecavir demonstrated substantial effectiveness in the reversion of fibrosis and reversed cirrhosis in patients with hepatitis B virus (HBV)-related cirrhosis. However, there has not been a definitive conclusion regarding the association between entecavir and tenofovir on the risk of cirrhosis-related complications. Therefore, this study aimed to investigate the comparative effectiveness between tenofovir and entecavir in HBV-related cirrhosis patients. Methods: This was a retrospective study using Taiwan's Health Insurance Research Database. We enrolled newly diagnosed HBV-related cirrhosis patients who initiated entecavir and tenofovir between 2011 and 2019. Treatment groups were determined by the initial HBV antiviral medication prescribed. The primary composite outcome was the development of hepatocellular carcinoma (HCC), death from any causes, and liver transplantation. The secondary outcomes included all the individual components of the primary outcome. The incidence rate was calculated for each outcome for both treatment groups using the Fine-Gray subdistribution hazard models. Propensity score adjustment was used to balance treatment groups. Results: A total of 7,316 propensity score-matched treatment-naïve patients and 3,524 propensity score-matched treatment-experienced patients were included. Within treatment-naïve patients, those receiving tenofovir showed significantly lower hazards of developing the composite outcome (HR, 0.79; p < 0.0001), hepatocellular carcinoma (HR, 0.86; p = 0.027), mortality (HR, 0.75; p < 0.0001), and liver transplantation (HR, 0.70; p = 0.0189) than those receiving entecavir. As for treatment-experienced patients, tenofovir was associated with a significantly lower risk of the composite outcome (HR, 0.82; p = 0.0033) and hepatocellular carcinoma (HR, 0.60; p < 0.0001), but it did not show a significantly different risk of all-cause mortality (HR, 0.93; p = 0.3374) or liver transplantation (HR, 1.17; p = 0.5112) compared to entecavir. Conclusion: Tenofovir presented a significantly lower incidence of cirrhosis-related complications than entecavir in patients with hepatitis B virus-related cirrhosis. However, no statistically significant difference in death and liver transplantation was seen in treatment-experienced patients.

Current Status and Challenges in Anti-Hepatitis B Virus Agents Based on Inactivation/Inhibition or Elimination of Hepatitis B Virus Covalently Closed Circular DNA

There has been over half a century since the discovery of hepatitis B virus (HBV) to now, but approximately 300 million patients with chronic hepatitis B (CHB) still live in the world, resulting in about one million deaths every year. Although currently approved antivirals (e.g., nucleoside analogues) are effective at reducing HBV replication, they have almost no impact on the existing HBV covalently closed circular DNA (cccDNA) reservoir. HBV cccDNA is a critical obstacle to the complete elimination of the virus via antiviral therapy. The true cure of HBV infection requires the eradication of viral cccDNA from HBV-infected cells; thus, the development of new agents directly or indirectly targeting HBV cccDNA is urgently needed due to the limitations of current available drugs against HBV infection. In this regard, it is the major focus of current anti-HBV research worldwide via different mechanisms to either inactivate/inhibit (functional cure) or eliminate (complete cure) HBV cccDNA. Therefore, this review discussed and summarized recent advances and challenges in efforts to inactivate/silence or eliminate viral cccDNA using anti-HBV agents from different sources, such as small molecules (including epigenetic drugs) and polypeptides/proteins, and siRNA or gene-editing approaches targeting/attenuating HBV cccDNA via different mechanisms, as well as future directions that may be considered in efforts to truly cure chronic HBV infection. In conclusion, no breakthrough has been made yet in attenuating HBV cccDNA, although a number of candidates have advanced into the phase of clinical trials. Furthermore, the overwhelming majority of the candidates function to indirectly target HBV cccDNA. No outstanding candidate directly targets HBV cccDNA. Relatively speaking, CCC_R08 and nitazoxanide may be some of the most promising agents to clear HBV infection in small molecule compounds. Additionally, CRISPR-Cas9 systems can directly target HBV cccDNA for decay and demonstrate significant anti-HBV activity. Consequently, gene-editing approaches targeting HBV cccDNA may be one of the most promising means to achieve the core goal of anti-HBV therapeutic strategies. In short, more basic studies on HBV infection need to be carried out to overcome these challenges.

Activation of AIM2 by hepatitis B virus results in antiviral immunity that suppresses hepatitis C virus during coinfection

IMPORTANCE

Clinical data suggest that Hepatitis C virus (HCV) levels are generally lower in Hepatitis B virus (HBV) co-infected patients, but the mechanism is unknown. Here, we show that HBV, but not HCV, activated absent in melanoma-2. This in turn results in inflammasome-mediated cleavage of pro-IL-18, leading to an innate immune activation cascade that results in increased interferon-γ, suppressing both viruses.

Hepatitis B surface antigen reduction is associated with hepatitis B core-specific CD8+ T cell quality

Despite treatment, hepatitis B surface antigen (HBsAg) persists in patients with chronic hepatitis B (CHB), suggesting the likely presence of the virus in the body. CD8+ T cell responses are essential for managing viral replication, but their effect on HBsAg levels remains unclear. We studied the traits of activated CD8+ T cells and HBV-specific CD8+ T cells in the blood of CHB patients undergoing nucleos(t)ide analog (NUC) therapy. For the transcriptome profiling of activated CD8+ T cells in peripheral blood mononuclear cells (PBMCs), CD69+ CD8+ T cells were sorted from six donors, and single-cell RNA sequencing (scRNA-seq) analysis was performed. To detect HBV-specific CD8+ T cells, we stimulated PBMCs from 26 donors with overlapping peptides covering the HBs, HBcore, and HBpol regions of genotype A/B/C viruses, cultured for 10 days, and analyzed via multicolor flow cytometry. scRNA-seq data revealed that CD8+ T cell clusters harboring the transcripts involved in the cytolytic functions were frequently observed in donors with high HBsAg levels. Polyfunctional analysis of HBV-specific CD8+ T cells utilized by IFN-γ/TNFα/CD107A/CD137 revealed that HBcore-specific cells exhibited greater polyfunctionality, suggesting that the quality of HBV-specific CD8+ T cells varies among antigens. Moreover, a subset of HBcore-specific CD8+ T cells with lower cytolytic potential was inversely correlated with HBsAg level. Our results revealed a stimulant-dependent qualitative difference in HBV-specific CD8+ T cells in patients with CHB undergoing NUC therapy. Hence, the induction of HBcore-specific CD8+ T cells with lower cytolytic potential could be a new target for reducing HBsAg levels.

IFN-γ: A Crucial Player in the Fight Against HBV Infection?

About 0.8 million people die because of hepatitis B virus (HBV) infection each year. In around 5% of infected adults, the immune system is ineffective in countering HBV infection, leading to chronic hepatitis B (CHB). CHB is associated with hepatocellular carcinoma, which can lead to patient death. Unfortunately, although current treatments against CHB allow control of HBV infection, they are unable to achieve complete eradication of the virus. Cytokines of the IFN family represent part of the innate immune system and are key players in virus elimination. IFN secretion induces the expression of interferon stimulated genes, producing proteins that have antiviral properties and that are essential to cell-autonomous immunity. IFN-α is commonly used as a therapeutic approach for CHB. In addition, IFN-γ has been identified as the main IFN family member responsible for HBV eradication during acute infection. In this review, we summarize the key evidence gained from cellular or animal models of HBV replication or infection concerning the potential anti-HBV roles of IFN-γ with a particular focus on some IFN-γ-inducible genes.

APOBEC3 activity promotes the survival and evolution of drug-tolerant persister cells during acquired resistance to EGFR inhibitors in lung cancer

APOBEC mutagenesis is one of the most common endogenous sources of mutations in human cancer and is a major source of genetic intratumor heterogeneity. High levels of APOBEC mutagenesis are associated with poor prognosis and aggressive disease across diverse cancers, but the mechanistic and functional impacts of APOBEC mutagenesis on tumor evolution and therapy resistance remain relatively unexplored. To address this, we investigated the contribution of APOBEC mutagenesis to acquired therapy resistance in a model of EGFR-mutant non-small cell lung cancer. We find that inhibition of EGFR in lung cancer cells leads to a rapid and pronounced induction of APOBEC3 expression and activity. Functionally, APOBEC expression promotes the survival of drug-tolerant persister cells (DTPs) following EGFR inhibition. Constitutive expression of APOBEC3B alters the evolutionary trajectory of acquired resistance to the EGFR inhibitor gefitinib, making it more likely that resistance arises through de novo acquisition of the T790M gatekeeper mutation and squamous transdifferentiation during the DTP state. APOBEC3B expression is associated with increased expression of the squamous cell transcription factor ΔNp63 and squamous cell transdifferentiation in gefitinib-resistant cells. Knockout of ΔNp63 in gefitinibresistant cells reduces the expression of the p63 target genes IL1a/b and sensitizes these cells to the thirdgeneration EGFR inhibitor osimertinib. These results suggest that APOBEC activity promotes acquired resistance by facilitating evolution and transdifferentiation in DTPs, and suggest that approaches to target ΔNp63 in gefitinib-resistant lung cancers may have therapeutic benefit.

Immune response and treatment targets of chronic hepatitis B virus infection: innate and adaptive immunity

Chronic hepatitis B virus (HBV) infection is a major global public health risk that threatens human life and health, although the number of vaccinated people has increased. The clinical outcome of HBV infection depends on the complex interplay between viral replication and the host immune response. Innate immunity plays an important role in the early stages of the disease but retains no long-term immune memory. However, HBV evades detection by the host innate immune system through stealth. Therefore, adaptive immunity involving T and B cells is crucial for controlling and clearing HBV infections that lead to liver inflammation and damage. The persistence of HBV leads to immune tolerance owing to immune cell dysfunction, T cell exhaustion, and an increase in suppressor cells and cytokines. Although significant progress has been made in HBV treatment in recent years, the balance between immune tolerance, immune activation, inflammation, and fibrosis in chronic hepatitis B remains unknown, making a functional cure difficult to achieve. Therefore, this review focuses on the important cells involved in the innate and adaptive immunity of chronic hepatitis B that target the host immune system and identifies treatment strategies.

Transient and tunable CRISPRa regulation of APOBEC/AID genes for targeting hepatitis B virus

APOBEC/AID cytidine deaminases play an important role in innate immunity and antiviral defenses and were shown to suppress hepatitis B virus (HBV) replication by deaminating and destroying the major form of HBV genome, covalently closed circular DNA (cccDNA), without toxicity to the infected cells. However, developing anti-HBV therapeutics based on APOBEC/AID is complicated by the lack of tools for activating and controlling their expression. Here, we developed a CRISPR-activation-based approach (CRISPRa) to induce APOBEC/AID transient overexpression (>4-800,000-fold increase in mRNA levels). Using this new strategy, we were able to control APOBEC/AID expression and monitor their effects on HBV replication, mutation, and cellular toxicity. CRISPRa prominently reduced HBV replication (∼90%-99% decline of viral intermediates), deaminated and destroyed cccDNA, but induced mutagenesis in cancer-related genes. By coupling CRISPRa with attenuated sgRNA technology, we demonstrate that APOBEC/AID activation can be precisely controlled, eliminating off-site mutagenesis in virus-containing cells while preserving prominent antiviral activity. This study untangles the differences in the effects of physiologically expressed APOBEC/AID on HBV replication and cellular genome, provides insights into the molecular mechanisms of HBV cccDNA mutagenesis, repair, and degradation, and, finally, presents a strategy for a tunable control of APOBEC/AID expression and for suppressing HBV replication without toxicity.

Discovery of a first-in-class orally available HBV cccDNA inhibitor

BACKGROUND & AIMS

The persistence of covalently closed circular DNA (cccDNA) in infected hepatocytes is the major barrier preventing viral eradication with existing therapies in patients with chronic hepatitis B. Therapeutic agents that can eliminate cccDNA are urgently needed to achieve viral eradication and thus HBV cure.

METHODS

A phenotypic assay with HBV-infected primary human hepatocytes (PHHs) was employed to screen for novel cccDNA inhibitors. A HBVcircle mouse model and a uPA-SCID (urokinase-type plasminogen activator-severe combined immunodeficiency) humanized liver mouse model were used to evaluate the anti-HBV efficacy of the discovered cccDNA inhibitors.

RESULTS

Potent and dose-dependent reductions in extracellular HBV DNA, HBsAg, and HBeAg levels were achieved upon the initiation of ccc_R08 treatment two days after the HBV infection of PHHs. More importantly, the level of cccDNA was specifically reduced by ccc_R08, while it did not obviously affect mitochondrial DNA. Additionally, ccc_R08 showed no significant cytotoxicity in PHHs or in multiple proliferating cell lines. The twice daily oral administration of ccc_R08 to HBVcircle model mice, which contained surrogate cccDNA molecules, significantly decreased the serum levels of HBV DNA and antigens, and these effects were sustained during the off-treatment follow-up period. Moreover, at the end of follow-up, the levels of surrogate cccDNA molecules in the livers of ccc_R08-treated HBVcircle mice were reduced to below the lower limit of quantification.

CONCLUSIONS

We have discovered a small-molecule cccDNA inhibitor that reduces HBV cccDNA levels. cccDNA inhibitors potentially represent a new approach to completely cure patients chronically infected with HBV.

IMPACT AND IMPLICATIONS

Covalently closed circular DNA (cccDNA) persistence in HBV-infected hepatocytes is the root cause of chronic hepatitis B. We discovered a novel small-molecule cccDNA inhibitor that can specifically reduce cccDNA levels in HBV-infected hepatocytes. This type of molecule could offer a new approach to completely cure patients chronically infected with HBV.

Serum cytokine profiles predict outcomes of chronic hepatitis B patients discontinuing entecavir or tenofovir therapy

BACKGROUND/PURPOSE

Distinct hepatitis relapse has been observed after discontinuing entecavir (ETV) or tenofovir disoproxil fumarate (TDF) therapy in chronic hepatitis B (CHB) patients. End-of-therapy (EOT) serum cytokines were compared and used for outcome prediction.

METHODS

A total of 80 non-cirrhotic CHB patients in a tertiary medical center in Taiwan who discontinued ETV (n = 51) or TDF (n = 29) therapy after fulfilling the APASL guidelines were prospectively enrolled. Serum cytokines were measured at EOT and 3rd month afterwards. Multivariable analysis was performed to predict virological relapse (VR, HBV DNA >2000 IU/mL), clinical relapse (CR, VR and alanine aminotransferase > 2-fold upper limit of normal) and hepatitis B surface antigen (HBsAg) seroclearance.

RESULTS

Compared with TDF group, ETV stoppers had greater interleukin 5 (IL-5), IL-12 p70, IL-13, IL-17 A and tumor necrosis factor alpha (TNF-alpha) (all P < 0.05) at EOT. Older age, TDF use, higher EOT HBsAg and IL-18 (Hazard ratio [HR], 1.01; 95% CI, 1.00-1.02) levels at EOT predicted VR, while older age, higher EOT HBsAg and IL-7 (HR, 1.25; 95% CI, 1.00-1.56) levels predicted CR. In TDF stoppers, higher IL-7 (HR, 1.29; 95% CI, 1.05-1.60) and IL-18 (HR, 1.02; 95% CI, 1.00-1.04) levels predicted VR, while IL-7 (HR, 1.34; 95% CI, 1.08-1.65) and interferon-gamma (IFN-gamma) (HR, 1.08; 95% CI, 1.02-1.14) levels predicted CR. A lower EOT HBsAg level was associated with HBsAg seroclearance.

CONCLUSION

Distinct cytokine profiles were observed after stopping ETV or TDF. Higher EOT IL-7, IL-18, and IFN-gamma could be probable predictors for VR and CR in patients discontinuing NA therapies.

Therapies against chronic hepatitis B infections: The times they are a-changin', but the changing is slow!

PREAMBULAR NOTA BENE

As a tribute to Dr Mike Bray, the following review of literature willbe mainly based on published data andconcepts, but will also contain my personal views, and in this respect could be more considered as a bioassay. Even though a cost-effective and excellent prophylactic vaccine exists since many years to protect against hepatitis B virus (HBV) infection, academic-researcher/drug-developers/stakeholders are still busy with the R&D of novel therapies that could eventually have an impact on its worldwide incidence. The Taiwanese experience have univocally demonstrated the effectiveness of constrained national HBV prophylactic vaccination programs to prevent the most dramatic HBV-induced end-stage liver disease, which is hepatocellular carcinoma; but yet the number of individuals chronically infected with the virus, for whom the existing prophylactic vaccine is no longer useful, remains high, with around 300 million individuals around the globe. In this review/bioassay, recent findings and novel concepts on prospective therapies against HBV infections will be discussed; yet it does not have the pretention to be exhaustive, as "pure immunotherapeutic concepts" will be mainly let aside (or referred to other reviews) due to a lack of expertise of this writer, but also due to the lack of, or incremental, positive results in clinical trials as-off today with these approaches.

Alpha-kinase 1 (ALPK1) agonist DF-006 demonstrates potent efficacy in mouse and primary human hepatocyte (PHH) models of hepatitis B

BACKGROUND AND AIMS

In the treatment of chronic hepatitis B (CHB) infection, stimulation of innate immunity may lead to hepatitis B virus (HBV) cure. Alpha-kinase 1 (ALPK1) is a pattern recognition receptor (PRR) that activates the NF-κB pathway and stimulates innate immunity. Here we characterized the preclinical anti-HBV efficacy of DF-006, an orally active agonist of ALPK1 currently in clinical development for CHB.

APPROACH AND RESULTS

In adeno-associated virus (AAV)-HBV mouse models and primary human hepatocytes (PHHs) infected with HBV, we evaluated the antiviral efficacy of DF-006. In the mouse models, DF-006 rapidly reduced serum HBV DNA, hepatitis B surface antigen, and hepatitis B e antigen levels using doses as low as 0.08 μg/kg, 1 μg/kg, and 5 μg/kg, respectively. DF-006 in combination with the HBV nucleoside reverse transcriptase inhibitor, entecavir, further reduced HBV DNA. Antiviral efficacy in mice was associated with an increase in immune cell infiltration and decrease of hepatitis B core antigen, encapsidated pregenomic RNA, and covalently closed circular DNA in liver. At subnanomolar concentrations, DF-006 also showed anti-HBV efficacy in PHH with significant reductions of HBV DNA. Following dosing with DF-006, there was upregulation of NF-κB-targeted genes that are involved in innate immunity.

CONCLUSION

DF-006 was efficacious in mouse and PHH models of HBV without any indications of overt toxicity. In mice, DF-006 localized primarily to the liver where it potently activated innate immunity. The transcriptional response in mouse liver provides insights into mechanisms that mediate anti-HBV efficacy by DF-006.

Activation of distinct antiviral T-cell immunity: A comparison of bi- and trispecific T-cell engager antibodies with a chimeric antigen receptor targeting HBV envelope proteins

Despite the availability of an effective prophylactic vaccine, 820,000 people die annually of hepatitis B virus (HBV)-related liver disease according to WHO. Since current antiviral therapies do not provide a curative treatment for the 296 million HBV carriers around the globe, novel strategies to cure HBV are urgently needed. A promising approach is the redirection of T cells towards HBV-infected hepatocytes employing chimeric antigen receptors or T-cell engager antibodies. We recently described the effective redirection of T cells employing a second-generation chimeric antigen receptor directed against the envelope protein of hepatitis B virus on the surface of infected cells (S-CAR) as well as bispecific antibodies that engage CD3 or CD28 on T cells employing the identical HBV envelope protein (HBVenv) binder. In this study, we added a trispecific antibody comprising all three moieties to the tool-box. Cytotoxic and non-cytolytic antiviral activities of these bi- and trispecific T-cell engager antibodies were assessed in co-cultures of human PBMC with HBV-positive hepatoma cells, and compared to that of S-CAR-grafted T cells. Activation of T cells via the S-CAR or by either a combination of the CD3- and CD28-targeting bispecific antibodies or the trispecific antibody allowed for specific elimination of HBV-positive target cells. While S-CAR-grafted effector T cells displayed faster killing kinetics, combinatory treatment with the bispecific antibodies or single treatment with the trispecific antibody was associated with a more pronounced cytokine release. Clearance of viral antigens and elimination of the HBV persistence form, the covalently closed circular (ccc) DNA, through cytolytic as well as cytokine-mediated activity was observed in all three settings with the combination of bispecific antibodies showing the strongest non-cytolytic, cytokine-mediated antiviral effect. Taken together, we demonstrate that bi- and trispecific T-cell engager antibodies can serve as a potent, off-the-shelf alternative to S-CAR-grafted T cells to cure HBV.

Hepatitis B Virus Core Protein Is Not Required for Covalently Closed Circular DNA Transcriptional Regulation

Hepatitis B virus (HBV) infection is a major health burden worldwide, and currently there is no cure. The persistence of HBV covalently closed circular DNA (cccDNA) is the major obstacle for antiviral trement. HBV core protein (HBc) has emerged as a promising antiviral target, as it plays important roles in critical steps of the viral life cycle. However, whether HBc could regulate HBV cccDNA transcription remains under debate. In this study, different approaches were used to address this question. In synthesized HBV cccDNA and HBVcircle transfection assays, lack of HBc showed no effect on transcription of HBV RNA as well as HBV surface antigen (HBsAg) production in a hepatoma cell line and primary human hepatocytes. Reconstitution of HBc did not alter the expression of cccDNA-derived HBV markers. Similar results were obtained from an in vivo mouse model harboring cccDNA. Chromatin immunoprecipitation (ChIP) or ChIP sequencing assays revealed transcription regulation of HBc-deficient cccDNA chromatin similar to that of wild-type cccDNA. Furthermore, treatment with capsid assembly modulators (CAMs) dramatically reduced extracellular HBV DNA but could not alter viral RNA and HBsAg. Our results demonstrate that HBc neither affects histone modifications and transcription factor binding of cccDNA nor directly influences cccDNA transcription. Although CAMs could reduce HBc binding to cccDNA, they do not suppress cccDNA transcriptional activity. Thus, therapeutics targeting capsid or HBc should not be expected to sufficiently reduce cccDNA transcription. IMPORTANCE Hepatitis B virus (HBV) core protein (HBc) has emerged as a promising antiviral target. However, whether HBc can regulate HBV covalently closed circular DNA (cccDNA) transcription remains elusive. This study illustrated that HBc has no effect on epigenetic regulation of cccDNA, and it does not participate in cccDNA transcription. Given that HBc is dispensable for cccDNA transcription, novel cccDNA-targeting therapeutics are needed for an HBV cure.

Robust antiviral responses in severe hepatitis flare persist after early retreatment cessation and lead toward hepatitis B surface antigen loss: A proof-of-concept study

AIM

Hepatitis B flare has been interpreted as result of immune response against upsurging hepatitis B virus (HBV) and its antigen(s) that may lead to HBV decline/clearance spontaneously. It has been speculated that antiviral therapy could halt the effective immune response with viral persistent as a consequence. A proof-of-concept study was conducted to investigate this issue.

METHODS

Serial biochemical, quantitative hepatitis B surface antigen (HBsAg), interferon-γ (IFN-γ) and tumor-necrosis factor-α (TNF-α) assays were performed in four patients with severe hepatitis flare who had achieved precipitous HBsAg decline within 4 weeks of antiviral therapy.

RESULTS

TNF-α and IFN-γ were found to be elevated in parallel to upsurging HBV DNA and HBsAg levels in all patients. Higher levels of TNF-α and IFN-γ and levels relative to qHBsAg were observed during and after early termination of therapy within 4 weeks in two patients and were followed by further HBsAg decline to <5 IU/ml and even achieved HBsAg loss in one patient. The patient who had stopped therapy on day 44 showed minimal HBsAg decline afterward and the patient who continued therapy showed a 10-fold rebound of qHBsAg from its nadir. The subsequent IFN-γ and TNF-α activity of these two patients was minimal.

CONCLUSIONS

The results suggest that patients with severe hepatitis flare who achieved precipitous HBsAg decline may have robust immune response to clear the virus, and early termination of antiviral therapy may allow the protective immune response to continue and accelerate HBV decline toward HBsAg loss.

Non-cytotoxic functions of CD8 T cells: “repentance of a serial killer”

Cytotoxic CD8 T cells (CTLs) are classically described as the “serial killers” of the immune system, where they play a pivotal role in protective immunity against a wide spectrum of pathogens and tumors. Ironically, they are critical drivers of transplant rejection and autoimmune diseases, a scenario very similar to the famous novel “The strange case of Dr. Jekyll and Mr. Hyde”. Until recently, it has not been well-appreciated whether CTLs can also acquire non-cytotoxic functions in health and disease. Several investigations into this question revealed their non-cytotoxic functions through interactions with various immune and non-immune cells. In this review, we will establish a new classification for CD8 T cell functions including cytotoxic and non-cytotoxic. Further, we will discuss this novel concept and speculate on how these functions could contribute to homeostasis of the immune system as well as immunological responses in transplantation, cancer, and autoimmune diseases.

Analyzing the gene regulatory network in hepatitis B patients by single-cell ATAC sequencing

OBJECTIVE

This study aims to provide a new perspective of determining the pathophysiology of chronic hepatitis B (CHB) development by analyzing the gene regulatory network in CHB patients using single-cell ATAC sequencing.

BACKGROUND

Hepatitis B virus (HBV)-related liver disease induces liver damage by hepatic immune and inflammatory responses. The exact mechanism is unknown. As such, there is an urgent need to address this problem and study the relationship between aberrant peripheral blood mononuclear cell (PBMC) immune response and progression of liver disease.

METHOD

The sequencing of the chromatin accessibility of 8016 cells from the whole venous blood of normal control (NC) individuals and CHB patients was performed through assay for transposase-accessible chromatin in single-cell sequencing (ScATAC-seq). Unsupervised clustering and annotation analyses were performed by Signac (version 1.7.0) and Seurat clustering to identify different cell types. Then, TF motif enrichment analysis and differentially expressed peak analysis were performed to identify cell-type-specific candidate open chromatins related to CHB.

RESULT

We identified 12 leukocytic clusters corresponding to five cell types. The specific cell types associated with CHB were found to be located in B-0 and T-3. We have drawn the regulatory network of the hepatitis B signal pathway composed of genes linked to the differentially expressed peaks of these two CHB disease-specific cell types. Further, we profoundly explored the potential mechanisms of B-0-associated TF motif IRF2 and T-3-associated TF motif FOXC2 in the occurrence of CHB.

CONCLUSION

We have drawn a systematic and distinguishing gene regulatory network of CHB-related PBMCs. Key Points • Peripheral blood mononuclear cells were robustly clustered based on their types without using antibodies. • We draw a systematic and distinctive gene regulatory network of CHB-related PBMC through ScATAC-seq.

Getting to HBV cure: The promising paths forward

Chronic HBV infection is a global public health burden estimated to impact nearly 300 million persons worldwide. Despite the advent of potent antiviral agents that effectively suppress viral replication, HBV cure remains difficult to achieve because of the persistence of covalently closed circular DNA (cccDNA), HBV-DNA integration into the host genome, and impaired immune response. Indefinite treatment is necessary for most patients to maintain level of viral suppression. The success of direct-acting antivirals (DAAs) for hepatitis C treatment has rejuvenated the search for a cure for chronic hepatitis B (CHB), though an HBV cure likely requires an additional layer: immunomodulators for restoration of robust immune responses. DAAs such as entry inhibitors, capsid assembly modulators, inhibitors of subviral particle release, cccDNA silencers, and RNA interference molecules have reached clinical development. Immunomodulators, namely innate immunomodulators (Toll-like receptor agonists), therapeutic vaccines, checkpoint inhibitors, and monoclonal antibodies, are also progressing toward clinical development. The future of the HBV cure possibly lies in triple combination therapies with concerted action on replication inhibition, antigen reduction, and immune stimulation. Many obstacles remain, such as overcoming translational failures, choosing the right endpoint using the right biomarkers, and leveraging current treatments in combination regimens to enhance response rates. This review gives an overview of the current therapies for CHB, HBV biomarkers used to evaluate treatment response, and development of DAAs and immune-targeting drugs and discusses the limitations and unanswered questions on the journey to an HBV cure.

Novel therapeutic strategies for Chronic Hepatitis B

The last few years have seen a resurgence of activity in the hepatitis B drug pipeline, with many compounds in various stages of development. This review aims to provide a comprehensive overview of the latest advances in therapeutics for chronic hepatitis B (CHB). We will discuss the broad spectrum of direct-acting antivirals in clinical development, including capsids inhibitors, siRNA, HBsAg and polymerase inhibitors. In addition, host-targeted therapies (HTT) will be extensively reviewed, focusing on the latest progress in immunotherapeutics such as toll-like receptors and RIG-1 agonists, therapeutic vaccines and immune checkpoints modulators. A growing number of HTT in pre-clinical development directly target the key to HBV persistence, namely the covalently closed circular DNA (cccDNA) and hold great promise for HBV cure. This exciting area of HBV research will be highlighted, and molecules such as cyclophilins inhibitors, APOBEC3 deaminases and epigenetic modifiers will be discussed.

Model to predict on-treatment restoration of functional HBV-specific CD8+ cell response foresees off-treatment HBV control in eAg-negative chronic hepatitis B

BACKGROUND

Hepatitis B virus (HBV)-specific CD8⁺ cell response restoration during nucleos(t)ide analogue (NUC) treatment could lead to off-treatment HBV control in e-antigen-negative chronic hepatitis B (CHBe(-)).

AIM

To predict this response with variables involved in T-cell exhaustion for use as a treatment stopping tool.

METHODS

In NUC-treated CHBe(-) patients, we considered a functional response in cases with HBV-specific CD8⁺ cells against core and polymerase HBV epitopes able to proliferate and secrete type I cytokines after antigen encounter. We performed a logistic regression model (LRM) to predict the likelihood of developing this response, based on patient age (subrogate of infection length), HBsAg level, NUC therapy starting point and duration (antigenic pressure). We discontinued treatment and assessed HBV DNA dynamics, HBsAg decline and loss during off-treatment follow-up according to LRM likelihood.

RESULTS

We developed an LRM that predicted the presence of a proliferative type I cytokine-secreting CD8⁺ cell response, which correlated positively with treatment duration and negatively with treatment initiation after the age of 40 years and with age adjusted by HBsAg level. We observed a positive correlation between LRM probability and intensity of proliferation, number of epitopes with the functional proliferating response and type I cytokine secretion level. Off-treatment, HBsAg loss, HBsAg decline >50% and HBV control were more frequent in the group with >90% LRM probability.

CONCLUSIONS

Short-term low-level antigen exposure and early long-term NUC treatment influence the restoration of a functional HBV-specific CD8⁺ cell response. Based on these predictors, a high likelihood of detecting this response at treatment withdrawal is associated with off-treatment HBV control and HBsAg decline and loss.

IFN-α inhibits HBV transcription and replication by promoting HDAC3-mediated de-2-hydroxyisobutyrylation of histone H4K8 on HBV cccDNA minichromosome in liver

The epigenetic modification of hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) plays a crucial role in cccDNA transcription and viral persistence. Interferon-α (IFN-α) is a pivotal agent against HBV cccDNA. However, the mechanism by which IFN-α modulates the epigenetic regulation of cccDNA remains poorly understood. In this study, we report that IFN-α2b enhances the histone deacetylase 3 (HDAC3)-mediated de-2-hydroxyisobutyrylation of histone H4 lysine 8 (H4K8) on HBV cccDNA minichromosome to restrict the cccDNA transcription in liver. By screening acetyltransferases and deacetylases, we identified that HDAC3 was an effective restrictor of HBV transcription and replication. Moreover, we found that HDAC3 was able to mediate the de-2-hydroxyisobutyrylation of H4K8 in HBV-expressing hepatoma cells. Then, the 2-hydroxyisobutyrylation of histone H4K8 (H4K8hib) was identified on the HBV cccDNA minichromosome, promoting the HBV transcription and replication. The H4K8hib was regulated by HDAC3 depending on its deacetylase domain in the system. The low level of HDAC3 and high level of H4K8hib were observed in the liver tissues from HBV-infected human liver-chimeric mice. The levels of H4K8hib on HBV cccDNA minichromosome were significantly elevated in the liver biopsy specimens from clinical hepatitis B patients, which was consistent with the high transcriptional activity of cccDNA. Strikingly, IFN-α2b effectively facilitated the histone H4K8 de-2-hydroxyisobutyrylation mediated by HDAC3 on the HBV cccDNA minichromosome in primary human hepatocytes and hepatoma cells, leading to the inhibition of HBV transcription and replication. Our finding provides new insights into the mechanism by which IFN-α modulates the epigenetic regulation of HBV cccDNA minichromosome.

Kinetics in HBsAg after Stopping Entecavir or Tenofovir in Patients with Virological Relapse but Not Clinical Relapse

This study investigated the kinetics in HBsAg and the HBsAg loss rate after entecavir or tenofovir disoproxil fumarate (TDF) cessation in patients with chronic hepatitis B (CHB) who achieved virological suppression after virological relapse without clinical relapse. A total 504 HBeAg-negative, non-cirrhotic patients who previously received entecavir or TDF with post-treatment and who were followed up for at least 30 months were included. Of the 504 patients, 128 achieved sustained virological suppression (Group I), and 81 experienced virological relapse without clinical relapse. Of the 81 patients, 52 had intermittent or persistent HBV DNA > 2000 IU/mL (Group II), and 29 achieved persistent virological suppression (HBV DNA < 2000 IU/mL) for at least 1.5 years (Group III) after virological relapse. A generalized estimating equations analysis showed that Groups I and III experienced larger off-treatment HBsAg declines than Group II (both, p < 0.001). The post-treatment HBsAg declines of Group I and Group III were similar (p = 0.414). A multivariate analysis showed that there were no differences in the HBsAg change and HBsAg decline (p = 0.920 and 0.886, respectively) or HBsAg loss rate (p = 0.192) between Group I and Group III. The patients who achieved persistent viral suppression after HBV relapse without clinical relapse have a similar decline in HBsAg and the HBsAg loss rate as the sustained responders.

HBV covalently closed circular DNA minichromosomes in distinct epigenetic transcriptional states differ in their vulnerability to damage

BACKGROUND AND AIMS

HBV covalently closed circular DNA (cccDNA) is a major obstacle for a cure of chronic hepatitis B. Accumulating evidence suggests that epigenetic modifications regulate the transcriptional activity of cccDNA minichromosomes. However, it remains unclear how the epigenetic state of cccDNA affects its stability.

APPROACHES AND RESULTS

By using HBV infection cell models and in vitro and in vivo recombinant cccDNA (rcccDNA) and HBVcircle models, the reduction rate of HBV cccDNA and the efficacy of apolipoprotein B mRNA editing enzyme catalytic subunit 3A (APOBEC3A)-mediated and CRISPR/CRISPR-associated 9 (Cas9)-mediated cccDNA targeting were compared between cccDNAs with distinct transcriptional activities. Interferon-α treatment and hepatitis B x protein (HBx) deletion were applied as two strategies for cccDNA repression. Chromatin immunoprecipitation and micrococcal nuclease assays were performed to determine the epigenetic pattern of cccDNA. HBV cccDNA levels remained stable in nondividing hepatocytes; however, they were significantly reduced during cell division, and the reduction rate was similar between cccDNAs in transcriptionally active and transcriptionally repressed states. Strikingly, HBV rcccDNA without HBx expression exhibited a significantly longer persistence in mice. The cccDNA with low transcriptional activity exhibited an epigenetically inactive pattern and was more difficult to access by APOBEC3A and engineered CRISPR-Cas9. The epigenetic regulator activating cccDNA increased its vulnerability to APOBEC3A.

CONCLUSIONS

HBV cccDNA minichromosomes in distinct epigenetic transcriptional states showed a similar reduction rate during cell division but significantly differed in their accessibility and vulnerability to targeted nucleases and antiviral agents. Epigenetic sensitization of cccDNA makes it more susceptible to damage and may potentially contribute to an HBV cure.

Activities of endogenous APOBEC3s and uracil-DNA-glycosylase affect the hypermutation frequency of hepatitis B virus cccDNA

The covalently closed circular DNA (cccDNA) of hepatitis B virus (HBV) plays a key role in the persistence of viral infection. We have previously shown that overexpression of an antiviral factor APOBEC3G (A3G) induces hypermutation in duck HBV (DHBV) cccDNA, whereas uracil-DNA-glycosylase (UNG) reduces these mutations. In this study, using cell-culture systems, we examined whether endogenous A3s and UNG affect HBV cccDNA mutation frequency. IFNγ stimulation induced a significant increase in endogenous A3G expression and cccDNA hypermutation. UNG inhibition enhanced the IFNγ-mediated hypermutation frequency. Transfection of reconstructed cccDNA revealed that this enhanced hypermutation caused a reduction in viral replication. These results suggest that the balance of endogenous A3s and UNG activities affects HBV cccDNA mutation and replication competency.

Follow-Up of 108 Patients with Chronic Hepatitis B Virus Infection Treated with Polyethylene Glycol-Conjugated Derivatives of Interferon-Alpha and Monitoring of Off-Treatment Virological Relapse

BACKGROUND This single center study, which enrolled 108 patients with chronic hepatitis B virus infection treated with pegylated interferon-alpha (PEG-IFN-alpha), aimed to follow up and monitor off-treatment responses, including virological relapse, and analyze predictors of long-term efficacy of the PEG-IFN-alpha regimen. MATERIAL AND METHODS In total, 108 hepatitis B e antigen (HBeAg)-positive patients with chronic hepatitis B who had completed the PEG-IFN-alpha regimen and achieved virological suppression were enrolled. The patients were followed up for 5 years to monitor off-treatment responses. Twenty-eight relevant factors, including the history of antiviral therapy and HBeAg seroconversion, were analyzed using the Cox proportional hazards regression model. RESULTS The cumulative rates of virological suppression were 75.70%, 68.68%, 65.25%, 63.91%, and 63.91% at 1, 2, 3, 4, and 5 years of the follow-up period, respectively. Compared with the rates of virological suppression, the cumulative rates of clinical suppression were 88.41%, 79.83%, 78.59%, 75.65%, and 75.65%, respectively, for the 5 years. Alanine aminotransferase (ALT) normalization at 24 weeks after off-therapy (relative risk [RR]=3.430, P=0.013) was a potential predictor for sustained virological suppression, and the history of anti-viral therapy (RR=0.164, P=0.004), quantitative value of hepatitis B virus surface antigen (HBsAg) at 48 weeks of anti-viral therapy (RR=2.697, P=0.039), and ALT normalization at 24 weeks after off-therapy (RR=5.467, P=0.004) were potential predictors for sustained clinical suppression. CONCLUSIONS Our results suggested that increased HBsAg levels at 48 weeks and normalization of ALT at 24 weeks after off-therapy might be predictive factors for long-term treatment efficacy.[color=red] [/color].

Natural antibody IgG levels are associated with HBeAg-positivity and seroconversion in chronic hepatitis B patients treated with entecavir

B1 cell-derived natural antibodies are non-specific polyreactive antibodies and can activate the complement pathway leading to lysis of enveloped virus particles before activation of the adaptive immune response. We investigated the relationship between natural antibody levels and treatment outcomes of 126 treatment-naïve chronic hepatitis B (CHB) patients, who underwent entecavir (ETV) treatment. Serum IgG1-3 and complement C3 levels were significantly higher in HBeAg-positive patients. In pre-treatment, IgG1 (odd ratios [OR] 2.3, p < 0.0001), IgG2 (OR 9.8, p < 0.0001), IgG3 (OR 7.4, p < 0.0001), and C3 (OR 7.2, p < 0.0001) were associated with HBeAg-positive patients. At baseline, IgG2 (OR 10.2, p = 0.025), IgG4, (OR 3.4, p = 0.026), and complement C1q (OR 5.0, p = 0.0068) were associated with seroconverters. Post-treatment levels of IgG1-4 and C3/C1q were also associated with HBeAg-positive patients and seroconverters. High levels of IgG2-4 and C1q were observed in seroconverters but not in virological responders. Thus, high pretreatment and post-treatment levels of natural antibody IgG1-4, complement C3, and/or C1q were significantly associated with HBeAg-positivity and HBeAg seroconverters in CHB patients with ETV treatment. These results suggest that the presence of preexisting host immunity against chronic hepatitis B is closely related to outcome of ETV treatment.

Innate and Adaptive Immunopathogeneses in Viral Hepatitis; Crucial Determinants of Hepatocellular Carcinoma

Viral hepatitis B (HBV) and hepatitis C (HCV) infections remain the most common risk factors for the development of hepatocellular carcinoma (HCC), and their heterogeneous distribution influences the global prevalence of this common type of liver cancer. Typical hepatitis infection elicits various immune responses within the liver microenvironment, and viral persistence induces chronic liver inflammation and carcinogenesis. HBV is directly mutagenic but can also cause low-grade liver inflammation characterized by episodes of intermittent high-grade liver inflammation, liver fibrosis, and cirrhosis, which can progress to decompensated liver disease and HCC. Equally, the absence of key innate and adaptive immune responses in chronic HCV infection dampens viral eradication and induces an exhausted and immunosuppressive liver niche that favors HCC development and progression. The objectives of this review are to (i) discuss the epidemiological pattern of HBV and HCV infections, (ii) understand the host immune response to acute and chronic viral hepatitis, and (iii) explore the link between this diseased immune environment and the development and progression of HCC in preclinical models and HCC patients.

Interaction between the Hepatitis B Virus and Cellular FLIP Variants in Viral Replication and the Innate Immune System

During viral evolution and adaptation, many viruses have utilized host cellular factors and machinery as their partners. HBx, as a multifunctional viral protein encoded by the hepatitis B virus (HBV), promotes HBV replication and greatly contributes to the development of HBV-associated hepatocellular carcinoma (HCC). HBx interacts with several host factors in order to regulate HBV replication and evolve carcinogenesis. The cellular FADD-like IL-1β-converting enzyme (FLICE)-like inhibitory protein (c-FLIP) is a major factor that functions in a variety of cellular pathways and specifically in apoptosis. It has been shown that the interaction between HBx and c-FLIP determines HBV fate. In this review, we provide a comprehensive and detailed overview of the interplay between c-FLIP and HBV in various environmental circumstances. We describe strategies adapted by HBV to establish its chronic infection. We also summarize the conventional roles of c-FLIP and highlight the functional outcome of the interaction between c-FLIP and HBV or other viruses in viral replication and the innate immune system.

Regulatory function of interferon-inducible 44-like for hepatitis B virus covalently closed circular DNA in primary human hepatocytes

AIM

Curing hepatitis B virus (HBV) infection requires elimination of covalently closed circular DNA (cccDNA). Interferon (IFN)-γ has noncytolytic antiviral potential; however, elimination of cccDNA could not be achieved. To enhance the regulatory effect, we comprehensively analyzed the host factors associated with cccDNA amplification and IFN-γ and IFN-α effects using an in vitro HBV infection system showing various transcription levels.

METHODS

Primary human hepatocytes were infected with HBV using genomic plasmids carrying the basic core promoter mutation A1762T/G1764A and/or the precore mutation G1896A and treated with IFN-γ and IFN-α. Comprehensive and functional studies involving microarray and small interfering RNA analysis revealed the host factors related to cccDNA regulation.

RESULTS

The HBV infection system reproduced the HBV life cycle and showed various propagation levels. Microarray analysis revealed 53 genes correlated with the cccDNA levels. Of the 53 genes, expression of IFN-induced protein 44-like (IFI44L) was significantly upregulated by IFN-γ and IFN-α. The anti-HBV effect of IFI44L is exerted regardless of IFN-γ or IFN-α by inhibiting the activation of nuclear factor-κB and signal transducer and activator of transcription 1 pathways.

CONCLUSIONS

Using the in vitro HBV infection system, an IFN-inducible molecule, IFI44L, associated with cccDNA amplification, was identified. These results suggest an innovative molecular strategy for the regulation of HBV cccDNA by controlling a novel host factor, IFI44L.

Hepatitis B Flare in Hepatitis B e Antigen-Negative Patients: A Complicated Cascade of Innate and Adaptive Immune Responses

Chronic hepatitis B virus (HBV) infection is a dynamic process involving interactions among HBV, hepatocytes, and the host immune system. The natural course of chronic hepatitis B (CHB) is divided into four chronological phases, including the hepatitis B e antigen (HBeAg)-positive and HBeAg-negative phases. During HBV flare, alanine aminotransferase (ALT) levels abruptly rise to >5× the upper limit of normal; this is thought to occur due to the immune response against an upsurge in serum HBV DNA and antigen levels. Hepatitis flares may occur spontaneously, during or after antiviral therapy, or upon immunosuppression or chemotherapy in both HBeAg-positive and HBeAg-negative patients. The clinical spectrum of HBV flares varies from asymptomatic to hepatic decompensation or failure. HBeAg seroconversion with ≥ 1 year of consolidation therapy is accepted as an endpoint of oral antiviral therapy in HBeAg-positive patients, but recommendations for treating HBeAg-negative patients differ. Thus, the management of HBeAg-negative patients has attracted increasing interest. In the current review, we summarize various types of HBV flares and the associated complex cascade of innate and adaptive immune responses, with a focus on HBeAg-negative CHB patients. Hopefully, this review will provide insight into immunopathogenesis to improve the management of HBV flares in HBeAg-negative CHB patients.

Immunobiology and pathogenesis of hepatitis B virus infection

Hepatitis B virus (HBV) is a non-cytopathic, hepatotropic virus with the potential to cause a persistent infection, ultimately leading to cirrhosis and hepatocellular carcinoma. Over the past four decades, the basic principles of HBV gene expression and replication as well as the viral and host determinants governing infection outcome have been largely uncovered. Whereas HBV appears to induce little or no innate immune activation, the adaptive immune response mediates both viral clearance as well as liver disease. Here, we review our current knowledge on the immunobiology and pathogenesis of HBV infection, focusing in particular on the role of CD8⁺ T cells and on several recent breakthroughs that challenge current dogmas. For example, we now trust that HBV integration into the host genome often serves as a relevant source of hepatitis B surface antigen (HBsAg) expression during chronic infection, possibly triggering dysfunctional T cell responses and favouring detrimental immunopathology. Further, the unique haemodynamics and anatomy of the liver - and the changes they frequently endure during disease progression to liver fibrosis and cirrhosis - profoundly influence T cell priming, differentiation and function. We also discuss why therapeutic approaches that limit the intrahepatic inflammatory processes triggered by HBV-specific T cells might be surprisingly beneficial for patients with chronic infection.

A Novel Mouse Model Harboring Hepatitis B Virus Covalently Closed Circular DNA

BACKGROUND AND AIMS

The persistence of viral covalently closed circular DNA (cccDNA) is the major obstacle for antiviral treatment against hepatitis B virus (HBV). Basic and translational studies are largely hampered due to the lack of feasible small animal models to support HBV cccDNA formation. The aim of this study is to establish a novel mouse model harboring cccDNA.

METHODS

An adeno-associated virus (AAV) vector carrying a replication-deficient HBV1.04-fold genome (AAV-HBV1.04) was constructed. The linear HBV genome starts from nucleotide 403 and ends at 538, which results in the splitting of HBV surface and polymerase genes. Different HBV replication markers were evaluated for AAV-HBV1.04 plasmid-transfected cells, the AAV-HBV1.04 viral vector-transduced cells, and mice injected with the AAV-HBV1.04 viral vector.

RESULTS

Compared with the previously reported AAV-HBV1.2 construct, direct transfection of AAV-HBV1.04 plasmid failed to produce hepatitis B surface antigen and progeny virus. Interestingly, AAV-HBV1.04 viral vector transduction could result in the formation of cccDNA and the production of all HBV replication markers in vitro and in vivo. The formation of cccDNA could be blocked by ATR (ataxia-telangiectasia and Rad3-related protein) inhibitors but not HBV reverse transcription inhibitor or capsid inhibitors. The AAV-HBV1.04 mouse supported long-term HBV replication and responded to antiviral treatments.

CONCLUSIONS

This AAV-HBV1.04 mouse model can support HBV cccDNA formation through ATR-mediated DNA damage response. The de novo formed cccDNA but not the parental AAV vector can lead to the production of hepatitis B surface antigen and HBV progeny. This model will provide a unique platform for studying HBV cccDNA and developing novel antivirals against HBV infection.

Characterization of a library of 20 HBV-specific MHC class II-restricted T cell receptors

CD4⁺ T cells play an important role in the immune response against cancer and infectious diseases. However, mechanistic details of their helper function in hepatitis B virus (HBV) infection in particular, or their advantage for adoptive T cell therapy remain poorly understood as experimental and therapeutic tools are missing. Therefore, we identified, cloned, and characterized a comprehensive library of 20 MHC class II-restricted HBV-specific T cell receptors (TCRs) from donors with acute or resolved HBV infection. The TCRs were restricted by nine different MHC II molecules and specific for eight different epitopes derived from intracellularly processed HBV envelope, core, and polymerase proteins. Retroviral transduction resulted in a robust expression of all TCRs on primary T cells. A high functional avidity was measured for all TCRs specific for epitopes S17, S21, S36, and P774 (half-maximal effective concentration [EC₅₀] <10 nM), or C61 and preS9 (EC₅₀ <100 nM). Eight TCRs recognized peptide variants of HBV genotypes A to D. Both CD4⁺ and CD8⁺ T cells transduced with the MHC II-restricted TCRs were polyfunctional, producing interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, and granzyme B (GrzB), and killed peptide-loaded target cells. Our set of MHC class II-restricted TCRs represents an important tool for elucidating CD4⁺ T cell help in viral infection with potential benefit for T cell therapy.

Roles of APOBEC3 in hepatitis B virus (HBV) infection and hepatocarcinogenesis

APOBEC3 (A3) cytidine deaminases inhibit hepatitis B virus (HBV) infection and play vital roles in maintaining a variety of biochemical processes, including the regulation of protein expression and innate immunity. Emerging evidence indicates that the deaminated deoxycytidine biochemical activity of A3 proteins in single-stranded DNA makes them a double-edged sword. These enzymes can cause cellular genetic mutations at replication forks or within transcription bubbles, depending on the physiological state of the cell and the phase of the cell cycle. Under pathological conditions, aberrant expression of A3 genes with improper deaminase activity regulation may threaten genomic stability and eventually lead to cancer development. This review attempted to summarize the antiviral activities and underlying mechanisms of A3 editing enzymes in HBV infections. Moreover, the correlations between A3 genes and hepatocarcinogenesis were also elucidated.

T-cell engager antibodies enable T cells to control HBV infection and to target HBsAg-positive hepatoma in mice

BACKGROUND & AIMS

Current antiviral therapies control but rarely eliminate HBV, leaving chronic HBV carriers at risk of developing hepatocellular carcinoma (HCC). Lacking or dysfunctional virus-specific adaptive immunity prevents control of HBV and allows the virus to persist. Restoring antiviral T-cell immunity could lead to HBV elimination and cure of chronically infected patients.

METHODS

We constructed bispecific T-cell engager antibodies that are designed to induce antiviral immunity through simultaneous binding of HBV envelope proteins (HBVenv) on infected hepatocytes and CD3 or CD28 on T cells. T-cell engager antibodies were employed in co-cultures with healthy donor lymphocytes and HBV-infected target cells. Activation of the T-cell response was determined by detection of pro-inflammatory cytokines, effector function (by cytotoxicity) and antiviral effects. To study in vivo efficacy, immune-deficient mice were transplanted with HBVenv-positive and -negative hepatoma cells.

RESULTS

The 2 T-cell engager antibodies synergistically activated T cells to become polyfunctional effectors that in turn elicited potent antiviral effects by killing infected cells and in addition controlled HBV via non-cytolytic, cytokine-mediated antiviral mechanisms. In vivo in mice, the antibodies attracted T cells specifically to the tumors expressing HBVenv resulting in T-cell activation, tumor infiltration and reduction of tumor burden.

CONCLUSION

This study demonstrates that the administration of HBVenv-targeting T-cell engager antibodies facilitates a robust T-cell redirection towards HBV-positive target cells and provides a feasible and promising approach for the treatment of chronic viral hepatitis and HBV-associated HCC.

LAY SUMMARY

T-cell engager antibodies are an interesting, novel therapeutic tool to restore immunity in patients with chronic hepatitis B. As bispecific antibodies, they bind envelope proteins on the surface of the hepatitis B virus (HBV) and CD3 or CD28 on T cells. This way, they induce a potent antiviral and cytotoxic T-cell response that leads to the elimination of HBV-positive cells. These bispecific T-cell engager antibodies are exciting therapeutic candidates for chronic hepatitis B and HBV-associated hepatocellular carcinoma.