Safety and immunogenicity of therapeutic DNA vaccine with antiviral drug in chronic HBV patients and its immunogenicity in mice

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.

Efficacy and safety of therapeutic vaccines for the treatment of chronic hepatitis B: A systematic review and meta-analysis of randomized controlled trials update

BACKGROUND

Most people diagnosed with chronic hepatitis B (CHB) need treatment to help reduce the risk of liver disease and limit disease transmission. Therapeutic vaccine (TV) candidates have been under study for their clinical effects on inducing HBV-specific host immune responses. This review aimed to systematically synthesize updated evidence on the efficacy and safety of TVs in patients with CHB.

METHODS

This systematic review was performed by searching different databases from January to February 2021. Completed randomized controlled trials that reported TVs' efficacy and/or safety for treating CHB compared with the standard of care (SOC) or placebo were included. Efficacy and safety estimates were reported as the logarithm of the odds ratio and risk differences, respectively. I2 > 50% was considered significant heterogeneity. Significant publication bias was considered when Egger's test P value < .10. The risk of bias was assessed using the Cochrane Risk of Bias tool. The GRADE methodology was used to assess the certainty of the evidence for each outcome.

RESULTS

Twenty-four articles with 2889 pooled samples were included. TVs made a significant difference in hepatitis B envelope antigen (HBeAg) SC (log OR = 0.76, P = .01) and (log OR = 0.40, P = .03) compared to placebo and combination therapy, respectively. HBeAg SC was significantly affected by TVs at the end of follow up (log OR = 0.49, P = .01), with significant HBsAg mean difference (MD = -0.62, P = .00). At the end of treatment, the TVs had no significant effect on HBV DNA negativity over the SOC (log OR = 0.62, P = .09) or placebo (log OR = -0.07, P = .91). TVs do not significantly affect the risk of serious adverse events (RD 0.02, 95% CI 0.00-0.04).

CONCLUSION

In patients with CHB, TVs had significant effects on HBeAg SC compared to the SOC or placebo. There was no significant difference between serious adverse events. TVs are promising treatment strategy to overcome CHB.

cccDNA epigenetic regulator as target for therapeutical vaccine development against hepatitis B

Chronic hepatitis B virus infection (CHB) remains a global health concern, with currently available antiviral therapies demonstrating limited effectiveness in preventing hepatocellular carcinoma (HCC) development. Two primary challenges in CHB treatment include the persistence of the minichromosome, covalently closed circular DNA (cccDNA) of the hepatitis B virus (HBV), and the failure of the host immune response to eliminate cccDNA. Recent findings indicate several host and HBV proteins involved in the epigenetic regulation of cccDNA, including HBV core protein (HBc) and HBV x protein (HBx). Both proteins might contribute to the stability of the cccDNA minichromosome and interact with viral and host proteins to support transcription. One potential avenue for CHB treatment involves the utilization of therapeutic vaccines. This paper explores HBV antigens suitable for epigenetic manipulation of cccDNA, elucidates their mechanisms of action, and evaluates their potential as key components of epigenetically-driven vaccines for CHB therapy. Molecular targeted agents with therapeutic vaccines offer a promising strategy for addressing CHB by targeting the virus and enhancing the host's immunological response. Despite challenges, the development of these vaccines provides new hope for CHB patients by emphasizing the need for HBV antigens that induce effective immune responses without causing T cell exhaustion.

HBV001: Phase I study evaluating the safety and immunogenicity of the therapeutic vaccine ChAdOx1-HBV

Background & Aims

Millions of people worldwide are infected chronically with HBV, which results in significant morbidity and mortality. Therapeutic vaccination is a strategy that aims to induce functional cure by restoring cellular immunity to HBV. Previously we have shown the candidate HBV immunotherapeutic vaccine ChAdOx1-HBV, encoding all major HBV antigens and a genetic adjuvant (shark invariant chain), is highly immunogenic in mice.

Methods

Here we report the results of HBV001, a first-in-human, phase I, non-randomised, dose-escalation trial of ChAdOx1-HBV assessed in healthy volunteers and patients with chronic HBV (CHB).

Results

Vaccination with a single dose of ChAdOx1-HBV was safe and well tolerated in both healthy and CHB cohorts. Vaccination induced high magnitude HBV-specific T cell responses against all major HBV antigens (core, polymerase, and surface) in healthy volunteers. Responses were detected but lower in patients with CHB. T cells generated by vaccination were cross-reactive between HBV C and D genotypes.

Conclusions

ChAdOx1-HBV is safe and immunogenic in healthy volunteers and patients with CHB. In further studies, ChAdOx1-HBV will be used in combination with other therapeutic strategies with an aim to overcome the attenuated immunogenicity in patients with CHB.

Impact and implications

Therapeutic vaccine ChAdOx1-HBV, a novel treatment for chronic hepatitis B infection (CHB), has been shown to be immunogenic in preclinical studies. In HBV001, a first-in-human phase I study, we show vaccination with ChAdOx1-HBV is safe and generates high magnitude T cell responses in healthy volunteers and lower levels of responses in patients with CHB. This is an important first step in the development of ChAdOx1-HBV as part of a wider therapeutic strategy to induce hepatitis B functional cure, and is of great interest to patients CHB and clinicians treating the condition.

Clinical Trials Registration

This study is registered at ClinicalTrials.gov (NCT04297917).

Hepatitis B Therapeutic Vaccine: A Patent Review

Viral hepatitis has long been underrated as a danger to global health. The UN only recently called for worldwide action to tackle viral hepatitis and lessen the disease burden in its "2030 Agenda for Sustainable Development". Hepatitis B virus (HBV), which causes liver cirrhosis and malignancy, is a main cause of death globally. This review analyses innovative HBV therapeutic vaccine candidates for which a patent was filed between January 2010 and March 2022 and presents future improvement techniques for vaccine efficacy. Although there is a preventative vaccine for HBV infection, over 3% of people worldwide have the disease on a long-term basis and can no longer benefit from it. Most people will have chronic HBV infection for the rest of their lives once it has been diagnosed. Moreover, only a small percentage of treated patients experience a functional cure with persistent hepatitis B surface antigen reduction. A significant proportion of deaths are caused by liver cirrhosis and hepatocellular cancer, which are both caused by chronic hepatitis B infection. Hence, there is an urgent need for novel medications due to the inadequacies of the current therapies.

Development of therapeutic vaccines for the treatment of diseases

Vaccines are one of the most effective medical interventions to combat newly emerging and re-emerging diseases. Prophylactic vaccines against rabies, measles, etc., have excellent effectiveness in preventing viral infection and associated diseases. However, the host immune response is unable to inhibit virus replication or eradicate established diseases in most infected people. Therapeutic vaccines, expressing specific endogenous or exogenous antigens, mainly induce or boost cell-mediated immunity via provoking cytotoxic T cells or elicit humoral immunity via activating B cells to produce specific antibodies. The ultimate aim of a therapeutic vaccine is to reshape the host immunity for eradicating a disease and establishing lasting memory. Therefore, therapeutic vaccines have been developed for the treatment of some infectious diseases and chronic noncommunicable diseases. Various technological strategies have been implemented for the development of therapeutic vaccines, including molecular-based vaccines (peptide/protein, DNA and mRNA vaccines), vector-based vaccines (bacterial vector vaccines, viral vector vaccines and yeast-based vaccines) and cell-based vaccines (dendritic cell vaccines and genetically modified cell vaccines) as well as combinatorial approaches. This review mainly summarizes therapeutic vaccine-induced immunity and describes the development and status of multiple types of therapeutic vaccines against infectious diseases, such as those caused by HPV, HBV, HIV, HCV, and SARS-CoV-2, and chronic noncommunicable diseases, including cancer, hypertension, Alzheimer's disease, amyotrophic lateral sclerosis, diabetes, and dyslipidemia, that have been evaluated in recent preclinical and clinical studies.

Hepatitis B functional cure and immune response

Hepatitis B virus (HBV) is a hepatotropic virus, which damage to hepatocytes is not direct, but through the immune system. HBV specific CD4+ T cells can induce HBV specific B cells and CD8+ T cells. HBV specific B cells produce antibodies to control HBV infection, while HBV specific CD8+ T cells destroy infected hepatocytes. One of the reasons for the chronicity of HBV infection is that it cannot effectively activate adoptive immunity and the function of virus specific immune cells is exhausted. Among them, virus antigens (including HBV surface antigen, e antigen, core antigen, etc.) can inhibit the function of immune cells and induce immune tolerance. Long term nucleos(t)ide analogues (NAs) treatment and inactive HBsAg carriers with low HBsAg level may "wake up" immune cells with abnormal function due to the decrease of viral antigen level in blood and liver, and the specific immune function of HBV will recover to a certain extent, thus becoming the "dominant population" for functional cure. In turn, the functional cure will further promote the recovery of HBV specific immune function, which is also the theoretical basis for complete cure of hepatitis B. In the future, the complete cure of chronic HBV infection must be the combination of three drugs: inhibiting virus replication, reducing surface antigen levels and specific immune regulation, among which specific immunotherapy is indispensable. Here we review the relationship, mechanism and clinical significance between the cure of hepatitis B and immune system.

Toward a complete cure for chronic hepatitis B: Novel therapeutic targets for hepatitis B virus

Hepatitis B virus (HBV) affects approximately 250 million patients worldwide, resulting in the progression to cirrhosis and hepatocellular carcinoma, which are serious public health problems. Although universal vaccination programs exist, they are only prophylactic and not curative. In the HBV life cycle, HBV forms covalently closed circular DNA (cccDNA), which is the viral minichromosome, in the nuclei of human hepatocytes and makes it difficult to achieve a complete cure with the current nucleos(t)ide analogs and interferon therapies. Current antiviral therapies rarely eliminate cccDNA; therefore, lifelong antiviral treatment is necessary. Recent trials for antiviral treatment of chronic hepatitis B have been focused on establishing a functional cure, defined by either the loss of hepatitis B surface antigen, undetectable serum HBV DNA levels, and/or seroconversion to hepatitis B surface antibody. Novel therapeutic targets and molecules are in the pipeline for early clinical trials aiming to cure HBV infection. The ideal strategy for achieving a long-lasting functional or complete cure might be using combination therapies targeting different steps of the HBV life cycle and immunomodulators. This review summarizes the current knowledge about novel treatments and combination treatments for a complete HBV cure.

Nucleic acid vaccines: A taboo broken and prospect for a hepatitis B virus cure

Although a prophylactic vaccine is available, hepatitis B virus (HBV) remains a major cause of liver-related morbidity and mortality. Current treatment options are improving clinical outcomes in chronic hepatitis B; however, true functional cure is currently the exception rather than the rule. Nucleic acid vaccines are among the emerging immunotherapies that aim to restore weakened immune function in chronically infected hosts. DNA vaccines in particular have shown promising results in vivo by reducing viral replication, breaking immune tolerance in a sustained manner, or even decimating the intranuclear covalently closed circular DNA reservoir, the hallmark of HBV treatment. Although DNA vaccines encoding surface antigens administered by conventional injection elicit HBV-specific T cell responses in humans, initial clinical trials failed to demonstrate additional therapeutic benefit when administered with nucleos(t)ide analogs. In an attempt to improve vaccine immunogenicity, several techniques have been used, including codon/promoter optimization, coadministration of cytokine adjuvants, plasmids engineered to express multiple HBV epitopes, or combinations with other immunomodulators. DNA vaccine delivery by electroporation is among the most efficient strategies to enhance the production of plasmid-derived antigens to stimulate a potent cellular and humoral anti-HBV response. Preliminary results suggest that DNA vaccination via electroporation efficiently invigorates both arms of adaptive immunity and suppresses serum HBV DNA. In contrast, the study of mRNA-based vaccines is limited to a few in vitro experiments in this area. Further studies are needed to clarify the prospects of nucleic acid vaccines for HBV cure.

Therapeutic vaccination for treatment of chronic hepatitis B

Chronic hepatitis B infection remains a serious global health threat, contributing to a large number of deaths through liver cirrhosis and hepatocellular carcinoma. Current treatment does not eradicate disease, and therefore new treatments are urgently needed. In acute hepatitis B virus (HBV) a strong immune response is necessary to clear the virus, but in chronic infection the immune response is weakened and dysfunctional. Therapeutic vaccination describes the process of inoculating individuals with a non‐infective form of viral antigen with the aim of inducing or boosting existing HBV‐specific immune responses, resulting in sustained control of HBV infection. In this review we outline the rationale for therapeutic vaccination in chronic HBV infection, discuss previous and ongoing trials of novel HBV therapeutic vaccine candidates and outline strategies to improve vaccine efficacy going forward.

Toward a new era of hepatitis B virus therapeutics: The pursuit of a functional cure

Hepatitis B virus (HBV) infection, although preventable by vaccination, remains a global health problem and a major cause of chronic liver disease. Although current treatment strategies suppress viral replication very efficiently, the optimal endpoint of hepatitis B surface antigen (HBsAg) clearance is rarely achieved. Moreover, the thorny problems of persistent chromatin-like covalently closed circular DNA and the presence of integrated HBV DNA in the host genome are ignored. Therefore, the scientific community has focused on developing innovative therapeutic approaches to achieve a functional cure of HBV, defined as undetectable HBV DNA and HBsAg loss over a limited treatment period. A deeper understanding of the HBV life cycle has led to the introduction of novel direct-acting antivirals that exert their function through multiple mechanisms, including inhibition of viral entry, transcriptional silencing, epigenetic manipulation, interference with capsid assembly, and disruption of HBsAg release. In parallel, another category of new drugs aims to restore dysregulated immune function in chronic hepatitis B accompanied by lethargic cellular and humoral responses. Stimulation of innate immunity by pattern-recognition receptor agonists leads to upregulation of antiviral cytokine expression and appears to contribute to HBV containment. Immune checkpoint inhibitors and adoptive transfer of genetically engineered T cells are breakthrough technologies currently being explored that may elicit potent HBV-specific T-cell responses. In addition, several clinical trials are attempting to clarify the role of therapeutic vaccination in this setting. Ultimately, it is increasingly recognized that elimination of HBV requires a treatment regimen based on a combination of multiple drugs. This review describes the rationale for progressive therapeutic interventions and discusses the latest findings in the field of HBV therapeutics.

Identification of novel hepatitis B virus therapeutic vaccine candidates derived from polymerase protein

Hepatitis B virus (HBV) infection is a worldwide health problem with high morbidity and mortality rates. The therapeutic vaccine is a promising method of treatment, and HBV polymerase plays a vital role in viral replication. Therefore, a therapeutic vaccine that binds to HBV DNA polymerase may control HBV infection. We predicted and selected epitopes of polymerase using online databases and analysis software. We then performed molecular docking and peptide binding assays to evaluate the binding energies and affinities between polymerase epitopes and the HLA-A0201 molecule. Finally, we induced T cells from the peripheral blood mononuclear cells (PBMCs) of healthy donors using each epitope and quantified the functions of epitope-specific T cells by IFN-γELISPOT assay, T2 cell cytotoxicity assay, HepG2.2.15 cell cytotoxicity assay and HBV gene expression assays. Four epitopes (RVTGGVFLV, GLLGFAAPF, LLDDEAGPL and YMDDVVLGA) had low binding energy and two epitopes (RVTGGVFLV and GLLGFAAPF) had a high binding affinity. The T cells stimulated by two epitopes (GLLGFAAPF and HLYSHPIIL) had a greater ability to induce immune response and suppress HBV. The HBV DNA polymerase epitopes identified in this study are promising targets for designing an epitope-based therapeutic vaccine against HBV.

Designing the next-generation therapeutic vaccines to cure chronic hepatitis B: focus on antigen presentation, vaccine properties and effect measures

In the mid‐90s, hepatitis B virus (HBV)‐directed immune responses were for the first time investigated in detail and revealed suboptimal T‐cell responses in chronic HBV patients. Based on these studies, therapeutic vaccination exploiting the antigen presentation capacity of dendritic cells to prime and/or boost HBV‐specific T‐cell responses was considered highly promising. Now, 25 years later, it has not yet delivered this promise. In this review, we summarise what has been clinically tested in terms of antigen targets and vaccine forms, how the immunological and therapeutic effects of these vaccines were assessed and what major clinical and immunological findings were reported. We combine the lessons learned from these trials with the most recent insights on HBV antigen presentation, T‐cell responses, vaccine composition, antiviral and immune‐modulatory drugs and disease biomarkers to derive novel opportunities for the next generation of therapeutic vaccines designed to cure chronic HBV either alone or in combination therapy.

Moving Fast Toward Hepatitis B Virus Elimination

Currently, there are two safe and effective therapeutic strategies for chronic hepatitis B treatment, namely, nucleoside analogs and interferon alpha (pegylated or non-pegylated). These treatments can control viral replication and improve survival; however, they do not eliminate the virus and therefore require long-term continued therapy. In addition, there are significant concerns about virus rebound on discontinuation of therapy and the development of fibrosis and hepatocellular carcinoma despite therapy. Therefore, the search for new, more effective, and safer antiviral agents that can cure hepatitis B virus (HBV) continues. Anti-HBV drug discovery and development is fundamentally impacted by our current understanding of HBV replication, disease physiopathology, and persistence of HBV covalently closed circular DNA (cccDNA). Several HBV replication targets are the basis for novel anti-HBV drug development strategies. Many of them are already in clinical trial phase 1 or 2, while others with promising results are still in preclinical stages. As research intensifies, potential HBV curative therapies and modalities in the pipeline are now on the horizon.

Metabolic regulation of the HBV-specific T cell function

Chronically HBV infected subjects are more than 260 million worldwide; cirrhosis and liver cancer represent possible outcomes which affect around 700,000 patients per year. Both innate and adaptive immune responses are necessary for viral control and both have been shown to be defective in chronic patients. Metabolic remodeling is an essential process in T cell biology, particularly for T cell activation, differentiation and survival. Cellular metabolism relies on the conversion of nutrients into energy to support intracellular processes, and to generate fundamental intermediate components for cell proliferation and growth. Adaptive immune responses are the central mechanisms for the resolution of primary human infections leading to the activation of pathogen-specific B and T cell functions. In chronic HBV infection the anti-viral immune response fails to contain the virus and leads to persistent hepatic tissue damage which may finally result in liver cirrhosis and cancer. This T cell failure is associated with metabolic alterations suggesting that control of nutrient uptake and intracellular utilization as well as correct regulation of intracellular metabolic pathways are strategic for T cell differentiation during persistent chronic infections. This review will discuss some of the main features of the T cell metabolic processes which are relevant to the generation of an efficient antiviral response, with specific focus on their clinical relevance in chronic HBV infection in the perspective of possible strategies to correct deregulated metabolic pathways underlying T cell dysfunction of chronic HBV patients.

New Approaches to the Treatment of Chronic Hepatitis B

The currently recommended treatment for chronic hepatitis B virus (HBV) infection achieves only viral suppression whilst on therapy, but rarely hepatitis B surface antigen (HBsAg) loss. The ultimate therapeutic endpoint is the combination of HBsAg loss, inhibition of new hepatocyte infection, elimination of the covalently closed circular DNA (cccDNA) pool, and restoration of immune function in order to achieve virus control. This review concentrates on new antiviral drugs that target different stages of the HBV life cycle (direct acting antivirals) and others that enhance both innate and adaptive immunity against HBV (immunotherapy). Drugs that block HBV hepatocyte entry, compounds that silence or deplete the cccDNA pool, others that affect core assembly, agents that degrade RNase-H, interfering RNA molecules, and nucleic acid polymers are likely interventions in the viral life cycle. In the immunotherapy category, molecules that activate the innate immune response such as Toll-like-receptors, Retinoic acid Inducible Gene-1 (RIG-1) and stimulator of interferon genes (STING) agonists or checkpoint inhibitors, and modulation of the adaptive immunity by therapeutic vaccines, vector-based vaccines, or adoptive transfer of genetically-engineered T cells aim towards the restoration of T cell function. Future therapeutic trends would likely be a combination of one or more of the aforementioned drugs that target the viral life cycle and at least one immunomodulator.

Antiviral therapy for the sexually transmitted viruses: recent updates on vaccine development

INTRODUCTION

The sexually transmitted infections (STIs) caused by viruses including human T cell leukemia virus type-1 (HTLV-1), human immunodeficiency virus-1 (HIV-1), human simplex virus-2 (HSV-2), hepatitis C virus (HCV), hepatitis B virus (HBV), and human papillomavirus (HPV) are major public health issues. These infections can cause cancer or result in long-term health problems. Due to high prevalence of STIs, a safe and effective vaccine is required to overcome these fatal viruses.

AREAS COVERED

This review includes a comprehensive overview of the literatures relevant to vaccine development against the sexually transmitted viruses (STVs) using PubMed and Sciencedirect electronic search engines. Herein, we discuss the efforts directed toward development of effective vaccines using different laboratory animal models including mice, guinea pig or non-human primates in preclinical trials, and human in clinical trials with different phases.

EXPERT OPINION

There is no effective FDA approved vaccine against the sexually transmitted viruses (STVs) except for HBV and HPV as prophylactic vaccines. Many attempts are underway to develop vaccines against these viruses. There are several approaches for improving prophylactic or therapeutic vaccines such as heterologous prime/boost immunization, delivery system, administration route, adjuvants, etc. In this line, further studies can be helpful for understanding the immunobiology of STVs in human. Moreover, development of more relevant animal models is a worthy goal to induce effective immune responses in humans.

Hepatitis B: Current Status of Therapy and Future Therapies

Despite the availability of a protective vaccine for over 3 decades, the number of persons with chronic hepatitis B virus (HBV) infection remains high. These persons are at risk for cirrhosis and hepatocellular carcinoma. Current treatment is effective at inhibiting viral replication and reducing complications of chronic HBV infection, but is not curative. There is a need for novel, finite therapy that can cure chronic HBV infection. Several agents are in early-phase development and can be broadly viewed as agents that target the virus directly or indirectly or the host immune response. This article highlights key developments in antiviral/immunomodulatory therapy, the rationale for these approaches, and possible therapeutic regimens.

Targeting Host Innate and Adaptive Immunity to Achieve the Functional Cure of Chronic Hepatitis B

Despite the availability of an effective preventive vaccine for hepatitis B virus (HBV) for over 38 years, chronic HBV (CHB) infection remains a global health burden with around 257 million patients. The ideal treatment goal for CHB infection would be to achieve complete cure; however, current therapies such as peg-interferon and nucleos(t)ide analogs are unable to achieve the functional cure, the newly set target for HBV chronic infection. Considering the fact functional cure has been accepted as an endpoint in the treatment of chronic hepatitis B by scientific committee, the development of alternative therapeutic strategies is urgently needed to functionally cure CHB infection. A promising target for future therapeutic strategies is immune modulation to restore dysfunctional HBV-specific immunity. In this review, we provide an overview of the progress in alternative therapeutic strategies, including immune-based therapeutic approaches that enhance host innate and adaptive immunity to achieve and increase the functional cure from CHB infection.

Therapeutic efficacy of hepatitis B virus vaccine in treatment of chronic HBV infections: A systematic review and meta-analysis

There is a need for improved treatment of patients with chronic hepatitis B (CHB). We reviewed the literature to explore the efficacy of HB vaccines alone or in combination therapy (CT) with antiviral drugs in CHB patients and to meta-analyze data from randomized controlled trials. We conducted a systematic search in ten databases. All studies investigating the efficacy of HBV vaccine in HBV infected patients were included with no restrictions. Among 1359 studies initially identified, 23 studies (n = 1956 patients) were included for the final analysis. CT showed a significant reduction of HBV DNA compared with analogue monotherapy (AM) at the 12-month follow-up period (odds ratio (OR) = 2.835, 95% confidence interval (CI) [1.275, 6.306], p = .011). Additionally, CT also remarkably induce HbsAg loss in comparison with AM (OR = 11.736, 95% CI [1.841, 74.794], p = .009). Our pooled data revealed no difference between treatment and control regarding alanine aminotransferase normalization, HBeAg seroconversion, and HBeAg disappearance. In addition, CT using vaccine and NAs resulted in a statistically significant higher incidence of adverse effects than AM. The therapeutic effects of combination therapy for patients with CHB were encouraging, but future studies need to investigate all possible treatment combinations and assess their cost-effectiveness.

Present and Future Therapies for Chronic Hepatitis B

Chronic hepatitis B (CHB) remains the leading cause of liver-related morbidity and mortality across the world. If left untreated, approximately one-third of these patients will progress to severe end-stage liver diseases including liver failure, cirrhosis, and hepatocellular carcinoma (HCC). High level of serum HBV DNA is strongly associated with the development of liver failure, cirrhosis, and HCC. Therefore, antiviral therapy is crucial for the clinical management of CHB. Current antiviral drugs including nucleoside/nucleotide analogues (NAs) and interferon-α (IFN-α) can suppress HBV replication and reduce the progression of liver disease, thus improving the long-term outcomes of CHB patients. This chapter will discuss the standard and optimization antiviral therapies in treatment-naïve and treatment-experienced patients, as well as in the special populations. The up-to-date advances in the development of new anti-HBV agents will be also discussed. With the combination of the current antiviral drugs and the newly developed antiviral agents targeting the different steps of the viral life cycle or the newly developed agents modulating the host immune responses, the ultimate eradication of HBV will be achieved in the future.

Nucleic acid vaccines for hepatitis B and C virus

Hepatitis B virus (HBV) and Hepatitis C virus (HCV) infections accounts for an important global health problem affecting over 250 million people all around the world. They can cause acute, transient and chronic infections in the human liver. Chronic infection of liver can lead to its failure or cancer. To deal with this problem, alternative approaches or strategies to inhibit these infections have already been started. DNA and mRNA-based vaccination will increase the efficacy and reduce toxicity in patients with Hepatitis B virus (HBV) and Hepatitis C virus (HCV) infections. Gene vaccines represent a promising alternative to conventional vaccine approaches because of their high potency, capacity for rapid development, low-cost manufacture and safe administration. MRNA-based vaccination is a method to elicit potent antigen-specific humoral and cell-mediated immune responses with a superior safety profile compared with DNA vaccines. Exploring the intricacies of these pathways can potentially help the researchers to explore newer vaccines. In this study, DNA and mRNA-based vaccination are introduced as an approach to treat Hepatitis B virus (HBV) and Hepatitis C virus (HCV) infections. DNA and mRNA-based vaccines as one of the most successful therapeutics are introduced and the clinical outcomes of their exploitation are explained.

Ex vivo Detection and Characterization of Hepatitis B Virus-Specific CD8+ T Cells in Patients Considered Immune Tolerant

In this study, we aimed to detect and characterize ex vivo virus-specific CD8⁺ T cells in patients with immune-tolerant hepatitis B virus (HBV) infection. We investigated a Korean chronic hepatitis B cohort composed of 15 patients in the immune-tolerant phase, 17 in the immune-active phase, and 13 under antiviral treatment. We performed enzyme-linked immunospot (ELISpot) assays ex vivo and intracellular cytokine staining after in vitro culture. We also performed ex vivo multimer staining assays and examined the expression of programmed death-1 (PD-1) and CD127 in pentamer-positive cells. Ex vivo ELISpot revealed that HBV-specific T cell function was weaker in immune-tolerant patients than in those under antiviral treatment. In vitro culture of peripheral blood mononuclear cells for 10 days revealed that HBV-specific CD8⁺ T cells produced interferon-γ in some immune-tolerant patients. We detected HBV-specific CD8⁺ T cells ex vivo (using the HBV core_18-27 pentamer) in patients from all three groups. The PD-1⁺ subset of pentamer⁺ CD8⁺ T cells was smaller ex vivo in the immune-tolerant phase than in the immune-active phase or under antiviral treatment. Interestingly, the proportion of PD-1⁺ CD8⁺ T cells in HBV-specific CD8⁺ T cells correlated with patient age when all enrolled patients were analyzed. Overall, HBV-specific CD8⁺ T cells are present in patients considered as immune-tolerant, although their ex vivo functionality is significantly weaker than that in patients under antiviral treatment (P < 0.05). Despite the high viral load, the proportion of PD-1 expression in HBV-specific CD8⁺ T cells is lower in the immune-tolerant phase than in other phases. Our results indicate appropriate stimulation may enhance the effector function of HBV-specific CD8⁺ T cells in patients considered as being in the immune-tolerant phase.

HBV Immune-Therapy: From Molecular Mechanisms to Clinical Applications

Chronic hepatitis B virus (HBV) infection represents a worldwide public health concern with approximately 250 million people chronically infected and at risk of developing liver cirrhosis and hepatocellular carcinoma. Nucleos(t)ide analogues (NUC) are the most widely used therapies for HBV infection, but they often require long-lasting administration to avoid the risk of HBV reactivation at withdrawal. Therefore, there is an urgent need to develop novel treatments to shorten the duration of NUC therapy by accelerating virus control, and to complement the effect of available anti-viral therapies. In chronic HBV infection, virus-specific T cells are functionally defective, and this exhaustion state is a key determinant of virus persistence. Reconstitution of an efficient anti-viral T cell response may thus represent a rational strategy to treat chronic HBV patients. In this perspective, the enhancement of adaptive immune responses by a checkpoint inhibitor blockade, specific T cell vaccines, lymphocyte metabolism targeting, and autologous T cell engineering, including chimeric antigen receptor (CAR) and TCR-redirected T cells, constitutes a promising immune modulatory approach for a therapeutic restoration of protective immunity. The advances of the emerging immune-based therapies in the setting of the HBV research field will be outlined.

Clearance of HBeAg and HBsAg of HBV in mice model by a recombinant HBV vaccine combined with GM-CSF and IFN-α as an effective therapeutic vaccine adjuvant

Chronic hepatitis B virus (CHB) infection is a significant public threat. Current interferon-α (IFN-α) based therapies and anti-viral drugs have failed to clear the infection in the majority of CHB patients and animal models. In our previous study, we established a combined protocol that employed a 3-day pretreatment with granulocyte-macrophage colony stimulating factor (GM-CSF) prior to a standard HBV vaccine. It achieved a 90% reduction of HBsAg level in the HBsAg transgenic mouse model. This protocol, while effective, remains too complex for clinical use. In this study, we formulated a new regimen by combining GM-CSF, IFN-α and a recombinant HBV vaccine (GM-CSF/IFN-α/VACCINE) into a single preparation and tested its efficacy in a HBV infection model. After four vaccinations, both serum HBeAg and HBsAg were cleared, accompanied by a 95% reduction of HBV⁺ hepatocytes and the presence of a large number of infiltrating CD8⁺ T cells in the liver. Mechanistically these robust responses were initiated by a vaccine-induced conversion of CCR2-dependent CD11b⁺Ly6C^hi monocytes into CD11b⁺CD11c⁺ DCs. This finding sheds light on the potential mechanism of action of the GM-CSF-based vaccine adjuvant and provides definable markers for clinical assessment during future testing of such highly potent vaccine protocols in HBV patients.

Effect of the hepatitis B virus S‑ecdCD40L vaccine therapy in HBV transgenic mice: A vaccine‑induced activation of antigen presenting dendritic cells

The classical hepatitis B virus (HBV) DNA vaccination plasmid only encodes for a single viral antigen, either the S or the PreS2/S antigen. Many strategies have been employed to improve the effect of these DNA vaccines. Our previous study identified that the fusion gene, HBV S‑ecd cluster of differentiation 40 ligand (CD40L), may promote the activation of dendritic cells (DCs) and enhance their function in vitro. In the current study, the effect of HBV S‑ecdCD40L vaccine therapy on liver DCs was investigated, and its therapeutic potential in HBV transgenic (HBV‑Tg) mice was evaluated. The eukaryotic expression plasmid, pcDNA3.1‑S‑ecdCD40L, was constructed by inserting the HBV S gene and mouse CD40L gene into the vector, pcDNA3.1 (+). HBV‑Tg mice were immunized with pcDNA3.1‑S‑ecdCD40L, pcDNA3.1‑S, pcDNA3.1 or PBS. Following this, immunophenotyping, cytokine production and T‑cell activation were analyzed in the CD11c‑enriched DC population obtained from the liver. Vaccine efficacy was further assessed by the detection of serological and biochemical parameters. When comparing with other control groups, DCs from HBV‑Tg mice immunized with pcDNA3.1‑S‑ecdCD40L exhibited increased expression of immunologically important cell molecules (CD86 and major histocompatibility complex class II), pro‑inflammatory cytokines (interleukin‑12), and enhanced capacity to promote allogeneic T‑cell proliferation. Furthermore, the HBV S‑ecdCD40L vaccine resulted in a significant inhibition of HBV DNA replication and downregulation of the hepatitis B virus surface antigen (HBsAg) in HBV‑Tg mice, without obvious liver injury. In conclusion, the HBV S‑ecdCD40L vaccine may be a feasible strategy for chronic HBV immunotherapy via promoting DC activation and function.

New treatments to reach functional cure: Rationale and challenges for emerging immune-based therapies

The landscape for chronic HBV therapy is rapidly evolving. The latest generation of antiviral drugs provide robust virus suppression with a high barrier to resistance that facilitates long-term treatment. However, low rates of HBsAg loss demonstrate that additional strategies are needed to consistency achieve a functional cure. The immune system can clear HBV and establish long-term control over the virus. Sufficiently boosting HBV immunity in chronic patients has been very difficult due to immune exhaustion, immune dysregulation, and inhibitory pathways suppressing the immune response. Therapeutic vaccines employing new technology, vectors and new immunomodulatory drugs that can elicit direct antiviral effects and cancel inhibitory mechanism may be able to overcome exhaustion. This review will discuss the justification for immunotherapy, lessons from previous trials and new vaccines/drugs in early stage clinical trials. The challenges of correlating immune responses induced by these drugs to clinical efficacy will also be addressed.

Treatment of hepatitis B virus with combination therapy now and in the future

Chronic Hepatitis B continues as a significant public health problem despite the availability of safe and effective antivirals and a highly effective protective vaccine. Current therapy, however rarely leads to cure and lifelong therapy is often required, contributing to poor uptake and ongoing morbidity. New insights into the hepatitis B viral life cycle and the host immune response have expanded the potential targets for drug therapies with interesting antiviral candidates and novel immunotherapeutic approaches in early stage development. Yet, HBV persistence is multifactorial - due to an intrahepatic reservoir and ongoing HBV-mediated immune dysregulation, making "cure" unlikely to be realized through even the most efficacious monotherapy. Building on the success seen in the treatment of hepatitis C (HCV) and human immunodeficiency virus (HIV), combination therapy may be an essential strategy to improve efficacy and decrease viral breakthrough. Combinations acting on immune and viral targets are particularly attractive. However, creating synergy while balancing efficacy and safety remains a clear challenge. Various approaches to combination therapy are reviewed, highlighting strengths and challenges of each potential strategy. Overall, combination therapies are attractive as the next step towards cure and are a key strategy for achieving treatment with finite durations and durable endpoints.

In Silico Analysis of Epitope-Based Vaccine Candidates against Hepatitis B Virus Polymerase Protein

Hepatitis B virus (HBV) infection has persisted as a major public health problem due to the lack of an effective treatment for those chronically infected. Therapeutic vaccination holds promise, and targeting HBV polymerase is pivotal for viral eradication. In this research, a computational approach was employed to predict suitable HBV polymerase targeting multi-peptides for vaccine candidate selection. We then performed in-depth computational analysis to evaluate the predicted epitopes’ immunogenicity, conservation, population coverage, and toxicity. Lastly, molecular docking and MHC-peptide complex stabilization assay were utilized to determine the binding energy and affinity of epitopes to the HLA-A0201 molecule. Criteria-based analysis provided four predicted epitopes, RVTGGVFLV, VSIPWTHKV, YMDDVVLGA and HLYSHPIIL. Assay results indicated the lowest binding energy and high affinity to the HLA-A0201 molecule for epitopes VSIPWTHKV and YMDDVVLGA and epitopes RVTGGVFLV and VSIPWTHKV, respectively. Regions 307 to 320 and 377 to 387 were considered to have the highest probability to be involved in B cell epitopes. The T cell and B cell epitopes identified in this study are promising targets for an epitope-focused, peptide-based HBV vaccine, and provide insight into HBV-induced immune response.

Research progress of therapeutic vaccines for treating chronic hepatitis B

Hepatitis B virus (HBV) is a member of Hepadnavirus family, which leads to chronic infection in around 5% of patients with a high risk of developing liver cirrhosis, liver failure, and hepatocellular carcinoma. ¹ Despite the availability of prophylactic vaccines against hepatitis B for over 3 decades, there are still more than 2 billion people have been infected and 240 million of them were chronic. Antiviral therapies currently used in the treatment of CHB (chronic hepatitis B) infection include peg-interferon, standard α-interferon and nucleos/tide analogs (NAs), but none of them can provide sustained control of viral replication. As an alternative strategy, therapeutic vaccines for CHB patients have been widely studied and showed some promising efficacies in dozens of preclinical and clinical trials. In this article, we review current research progress in several types of therapeutic vaccines for CHB treatment, including protein-based vaccines, DNA-based vaccines, live vector-based vaccines, peptide-based vaccines and cell-based therapies. These researches may provide some clues for developing new treatments in CHB infection.

Evolution in Our Understanding of Hepatitis B Virus Virology and Immunology

Hepatitis B virus (HBV) infection is a major global health challenge. HBV can cause significant morbidity and mortality by establishing acute and chronic hepatitis. Approximately 250 million people worldwide are chronically infected, and more than 2 billion people have been exposed to HBV. Since the discovery of HBV, the advances in our understanding of HBV virology and immunology have translated into effective vaccines and therapies for HBV infection. Although current therapies successfully suppress viral replication but rarely succeed in viral eradication, recent discoveries in HBV virology and immunology provide exciting rationales for novel treatment strategies aiming at HBV cure.

Research and Development of Hepatitis B Drugs: An Analysis Based on Technology Flows Measured by Patent Citations

Despite the existence of available therapies, the Hepatitis B virus infection continues to be one of the most serious threats to human health, especially in developing countries such as China and India. To shed light on the improvement of current therapies and development of novel anti-HBV drugs, we thoroughly investigated 212 US patents of anti-HBV drugs and analyzed the technology flow in research and development of anti-HBV drugs based on data from IMS LifeCycle databases. Moreover, utilizing the patent citation method, which is an effective indicator of technology flow, we constructed patent citation network models and performed network analysis in order to reveal the features of different technology clusters. As a result, we identified the stagnant status of anti-HBV drug development and pointed the way for development of domestic pharmaceuticals in developing countries. We also discussed about therapeutic vaccines as the potential next generation therapy for HBV infection. Lastly, we depicted the cooperation between entities and found that novel forms of cooperation added diversity to the conventional form of cooperation within the pharmaceutical industry. In summary, our study provides inspiring insights for investors, policy makers, researchers, and other readers interested in anti-HBV drug development.

N-Linked Glycosylation at an Appropriate Position in the Pre-S2 Domain Is Critical for Cellular and Humoral Immunity against Middle HBV Surface Antigen

Infection with hepatitis B virus (HBV) remains a worldwide health problem, and DNA-based vaccines against HBV have been tested for therapeutic applications. HBV possesses three envelope lipoproteins that are translated from a single reading-frame: large, middle, and small HBV surface antigens. Among these envelope proteins, the middle HBV surface antigen (MHBs) contains a constitutive N-linked glycosylation site at position 4 (Asn4) in the amino-terminal portion (MQWNSTTFHQ) of pre-S2 domain. Asn4 (shown in bold) is essential for secretion of viral particles and conserved among all serotypes of HBV, but its influence on the immunogenicity of MHBs remains unknown. Here, we constructed four MHBs genes carrying mutations, underlined, in the amino-terminal portion of pre-S2 domain. One mutant protein contains Q at position 4 (MQWQSTTFHQ). In addition, each of three mutant MHBs proteins contains a N-linked glycosylation site (N-X-S/T), relocated to position 5 (MQWQNTTFHQ), 6 (MQWQSNTSHQ) or 7 (MQWQSTNFTQ) in pre-S2 domain. The expression and immunogenic properties of mutant DNA vaccines were examined in 293T human renal epithelial cells and in BALB/c mice, respectively. We showed that Asn4 was critical for secretion and immunogenicity of MHBs. Moreover, the MHBs protein that carries a N-linked glycosylation site at position 5 or 7 retained the properties similar to wild-type MHBs. In contrast, the secretion-defective mutant protein carrying Asn at position 6 induced only marginal humoral and cellular immune responses in mice, despite the N-linked glycosylation. In conclusion, N-linked glycosylation at an appropriate position in pre-S2 domain is an essential requirement for DNA vaccine expressing MHBs.

Recent developments in antivirals against hepatitis B virus

Chronic hepatitis B virus (HBV) infection (CHB) is a major cause of cirrhosis and hepatocellular carcinoma (HCC). Although the availability of HBV vaccines effectively reduces the incidence of HBV infection, the healthcare burden from CHB remains high. Several antiviral agents, such as (pegylated-) interferon-α and nucleos(t)ide analogs are approved by US FDA for chronic HBV infection management. Entecavir (ETV) and tenofovir disoproxil fumarate (TDF) have been recommended as the first-line anti-HBV drugs for excellent viral suppression with a low risk of antiviral resistance, but the cost and need for essentially life-long treatment are considerable challenges. And none of these current treatments can eradicate the intracellular virus. Given these issues, there is still an unmet medical need for an efficient HBV cure. We summarize here the key developments of antivirals against hepatitis B virus, including HBV replication cycle inhibitors and host immune regulators.

Present and future therapies of hepatitis B: From discovery to cure

Hepatitis B virus (HBV) is a significant global pathogen, infecting more than 240 million people worldwide. While treatment for HBV has improved, HBV patients often require lifelong therapies and cure is still a challenging goal. Recent advances in technologies and pharmaceutical sciences have heralded a new horizon of innovative therapeutic approaches that are bringing us closer to the possibility of a functional cure of chronic HBV infection. In this article, we review the current state of science in HBV therapy and highlight new and exciting therapeutic strategies spurred by recent scientific advances. Some of these therapies have already entered into clinical phase, and we will likely see more of them moving along the development pipeline.

CONCLUSION

With growing interest in developing and efforts to develop more effective therapies for HBV, the challenging goal of a cure may be well within reach in the near future.

Progress and prospects of engineered sequence-specific DNA modulating technologies for the management of liver diseases

Liver diseases are one of the leading causes of mortality in the world. The hepatic illnesses, which include inherited metabolic disorders, hemophilias and viral hepatitides, are complex and currently difficult to treat. The maturation of gene therapy has heralded new avenues for developing effective intervention for these diseases. DNA modification using gene therapy is now possible and available technology may be exploited to achieve long term therapeutic benefit. The ability to edit DNA sequences specifically is of paramount importance to advance gene therapy for application to liver diseases. Recent development of technologies that allow for this has resulted in rapid advancement of gene therapy to treat several chronic illnesses. Improvements in application of derivatives of zinc finger proteins (ZFPs), transcription activator-like effectors (TALEs), homing endonucleases (HEs) and clustered regularly interspaced palindromic repeats (CRISPR) and CRISPR associated (Cas) systems have been particularly important. These sequence-specific technologies may be used to modify genes permanently and also to alter gene transcription for therapeutic purposes. This review describes progress in development of ZFPs, TALEs, HEs and CRISPR/Cas for application to treating liver diseases.

The infection efficiency and replication ability of circularized HBV DNA optimized the linear HBV DNA in vitro and in vivo

Studies on molecular mechanisms of the persist infection of hepatitis B virus have been hampered by a lack of a robust animal model. We successfully established a simple, versatile, and reproducible HBV persist infection model in vitro and in vivo with the circularized HBV DNA. The cells and mice were transfected or injected with circularized HBV DNA and pAAV/HBV1.2, respectively. At the indicated time, the cells, supernatants, serum samples, and liver tissues were collected for virological and serological detection. Both in vitro and in vivo, the circularized HBV DNA and pAAV/HBV1.2 could replicate and transcribe efficiently, but the infection effect of the former was superior to the latter (p < 0.05). The injection of circularized HBV genome DNA into the mice robustly supported HBV infection and approximately 80% of HBV infected mice established persistent infection for at least 10 weeks. This study demonstrated that the infection efficiency and replication ability of the circularized structure of HBV DNA overmatched that of the expression plasmid containing the linear structure of HBV DNA in vitro and in vivo. Meanwhile, this research results could provide useful tools and methodology for further study of pathogenic mechanisms and potential antiviral treatments of human chronic HBV infection in vitro and in vivo.

Therapeutic vaccination and immunomodulation in the treatment of chronic hepatitis B: preclinical studies in the woodchuck

Infection with hepatitis B virus (HBV) may lead to subclinical, acute or chronic hepatitis. In the prevaccination era, HBV infections were endemic due to frequent mother to child transmission in large regions of the world. However, there are still estimated 240 million chronic HBV carriers today and ca. 620,000 patients die per year due to HBV-related liver diseases. Recommended treatment of chronic hepatitis B with interferon-α and/or nucleos(t)ide analogues does not lead to satisfactory results. Induction of HBV-specific T cells by therapeutic vaccination or immunomodulation may be an innovative strategy to overcome virus persistence. Vaccination with commercially available HBV vaccines in patients with or without therapeutic reduction of viral load did not result in effective immune control of HBV infection, suggesting that combination of antiviral treatment with new formulations of therapeutic vaccines is needed. The woodchuck (Marmota monax) and its HBV-like woodchuck hepatitis virus are a useful preclinical animal model for developing new therapeutic approaches in chronic hepadnaviral infections. Several innovative approaches combining antiviral treatments using nucleos(t)ide analogues, with prime-boost vaccination using DNA vaccines, new hepadnaviral antigens or recombinant adenoviral vectors were tested in the woodchuck model. In this review, we summarize these encouraging results obtained with these therapeutic vaccines. In addition, we present potential innovations in immunostimulatory strategies by blocking the interaction of the inhibitory programmed death receptor 1 with its ligand in this animal model.

Treatment options beyond IFNα and NUCs for chronic HBV infection: expectations for tomorrow

Chronic hepatitis B virus (HBV) infection may progress to cirrhosis, hepatocellular carcinoma (HCC) and end-stage liver failure with time. Interruption of this process can only be achieved through effective antiviral treatment. This approach has so far involved the use of immunomodulators such as pegylated interferon alpha (Peg-IFNα) for a finite period of up to a year and nucleos-(t)ide analogues (NUCs) for treatment over much longer periods of time. The latter act by suppressing HBV replication at the level of DNA synthesis by inhibiting the viral reverse transcriptase/DNA polymerase and causing premature termination of DNA synthesis. The ideal treatment end point is loss of HBsAg in both HBeAg+ve and HBeAg-ve patients following monotherapy. This, however, is only achievable in a minority of patients. Secondary outcomes are durable HBeAg loss and seroconversion to anti-HBe, which occur in about 18-30% of HBeAg+ve patients depending on the antiviral used, and sustained suppression of HBV-DNA accompanied by biochemical normalization and histological improvement in non-HBeAg+ve seroconverting and HBeAg-ve patients. There is therefore a need for additional direct-acting antivirals (DAAs) targeting different stages of the life cycle of the virus, as well as immunotherapeutic approaches. Such developments may pave the way for their use either alone or more likely in combination in the fight against chronic HBV infection. Such drugs or approaches, which are currently undergoing preclinical or clinical testing, are the subject of this review.