A novel therapeutic hepatitis B vaccine induces cellular and humoral immune responses and breaks tolerance in hepatitis B virus (HBV) transgenic mice

Forthcoming Developments in Models to Study the Hepatitis B Virus Replication Cycle, Pathogenesis, and Pharmacological Advancements

Hepatitis, liver cirrhosis, and hepatocellular carcinoma are all manifestations of chronic hepatitis B. Its pathogenesis and molecular mechanism remain mysterious. As medical science progresses, different models are being used to study the disease from the physiological and molecular levels. Animal models have played an unprecedented role in achieving in-depth knowledge of the disease while posing no risk of harming humans throughout the study. The scarcity of acceptable animal models has slowed progress in hepatitis B virus (HBV) research and preclinical testing of antiviral medicines since HBV has a narrow species tropism and exclusively infects humans and higher primates. The development of human chimeric mice was supported by a better understanding of the obstacles to interspecies transmission, which has substantially opened the way for HBV research in vivo and the evaluation of possible chronic hepatitis B therapeutics. Animal models are cumbersome to handle, not accessible, and expensive. Hence, it is herculean to investigate the HBV replication cycle in animal models. Therefore, it becomes essential to build a splendid in vitro cell culture system to demonstrate the mechanisms attained by the HBV for its multiplication and sustenance. We also addressed the advantages and caveats associated with different models in examining HBV.

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.

Multiple optimizations of recombinant plasmid for improving expression of Hepatitis B core antigen in Escherichia coli

Hepatitis B core antigen (HBcAg) can self-assemble into virus-like particles (VLPs) when expressed in Escherichia coli. We optimized the different of the expression plasmid pBV220, including the ribosome bind site (RBS), spacer region, promoter and replication origin (ori), as well as the hbc gene dosage, to enhance HBcAg transcription and translation in E. coli. The optimized construct with a customized RBS6, 6 nt spacer, T7 promoter and pUCori significantly increased the levels of HBc36GFP fusion protein to 3.4-folds compared to the control. Thereafter, we substituted hbc36gfp gene with different copies of the hbc gene and tested the effects of gene dosage on HBcAg expression. The HBcAg-VLPs yield obtained using an engineered strain with three copies of hbc was 842.1 ± 46.8 μg/mL, which was 2.2-folds higher compared to that in the control strain. Thus, our study provides a simple and effective strategy for improving HBcAg expression in E. coli. Since the HBcAg-VLPs are promising carriers for presenting foreign antigen epitopes, an in vitro expression system that can generate high levels of HBcAg-VLPs can serve as a promising tool for developing novel HBV vaccines and drugs.

Novel Therapies of Hepatitis B and D

Hepatitis B virus (HBV) infection is a global public health issue and is a major cause of cirrhosis and hepatocellular carcinoma (HCC). Hepatitis D virus (HDV) requires the hepatitis B surface antigen (HBsAg) to replicate. The eradication of HBV, therefore, can also cure HDV. The current therapies for chronic hepatitis B and D are suboptimal and cannot definitely cure the viruses. In order to achieve functional or complete cure of these infections, novel therapeutic agents that target the various sites of the viral replicative cycle are necessary. Furthermore, novel immunomodulatory agents are also essential to achieve viral clearance. Many of these new promising compounds such as entry inhibitors, covalently closed circular DNA (cccDNA) inhibitors, small interfering RNAs (siRNAs), capsid assembly modulators and nucleic acid polymers are in various stages of clinical developments. In this review article, we provided a comprehensive overview of the structure and lifecycle of HBV, the limitations of the current therapies and a summary of the novel therapeutic agents for both HDV and HBV infection.

Improving Therapeutic Vaccination against Hepatitis B-Insights from Preclinical Models of Immune Therapy against Persistent Hepatitis B Virus Infection

Chronic hepatitis B affects more than 250 million individuals worldwide, putting them at risk of developing liver cirrhosis and liver cancer. While antiviral immune responses are key to eliminating hepatitis B virus (HBV) infections, insufficient antiviral immunity characterized by failure to eliminate HBV-infected hepatocytes is associated with chronic hepatitis B. Prophylactic vaccination against hepatitis B successfully established protective immunity against infection with the hepatitis B virus and has been instrumental in controlling hepatitis B. However, prophylactic vaccination schemes have not been successful in mounting protective immunity to eliminate HBV infections in patients with chronic hepatitis B. Here, we discuss the current knowledge on the development and efficacy of therapeutic vaccination strategies against chronic hepatitis B with particular emphasis on the pathogenetic understanding of dysfunctional anti-viral immunity. We explore the development of additional immune stimulation measures within tissues, in particular activation of immunogenic myeloid cell populations, and their use for combination with therapeutic vaccination strategies to improve the efficacy of therapeutic vaccination against chronic hepatitis B.

Challenges and Prospects of Plant-Derived Oral Vaccines against Hepatitis B and C Viruses

Hepatitis B and C viruses chronically affect approximately 3.5% of the global population, causing more than 800,000 deaths yearly due to severe liver pathogenesis. Current HBV vaccines have significantly contributed to the reduction of chronic HBV infections, supporting the notion that virus eradication is a feasible public health objective in the near future. In contrast to HBV, a prophylactic vaccine against HCV infection is not available yet; however, intense research efforts within the last decade have significantly advanced the field and several vaccine candidates are shortlisted for clinical trials. A successful vaccine against an infectious disease of global importance must not only be efficient and safe, but also easy to produce, distribute, administer, and economically affordable to ensure appropriate coverage. Some of these requirements could be fulfilled by oral vaccines that could complement traditional immunization strategies. In this review, we discuss the potential of edible plant-based oral vaccines in assisting the worldwide fight against hepatitis B and C infections. We highlight the latest research efforts to reveal the potential of oral vaccines, discuss novel antigen designs and delivery strategies, as well as the limitations and controversies of oral administration that remain to be addressed to make this approach successful.

Treatments for HBV: A Glimpse into the Future

The hepatitis B virus is responsible for most of the chronic liver disease and liver cancer worldwide. As actual therapeutic strategies have had little success in eradicating the virus from hepatocytes, and as lifelong treatment is often required, new drugs targeting the various phases of the hepatitis B virus (HBV) lifecycle are currently under investigation. In this review, we provide an overview of potential future treatments for HBV.

A novel therapeutic HBV vaccine candidate induces strong polyfunctional cytotoxic T cell responses in mice

BACKGROUND & AIMS

Current standard-of-care suppresses HBV replication, but does not lead to a functional cure. Treatment aiming to cure chronic hepatitis B (CHB) is believed to require the induction of strong cellular immune responses, such as by therapeutic vaccination.

METHODS

We designed a therapeutic HBV vaccine candidate (YF17D/HBc-C) using yellow fever vaccine YF17D as a live-attenuated vector to express HBV core antigen (HBc). Its ability to induce potent cellular immune responses was assessed in a mouse model that supports flavivirus replication.

RESULTS

Following a HBc protein prime, a booster of YF17D/HBc-C was found to induce vigorous cytotoxic T cell responses. In a direct head-to-head comparison, these HBc-specific responses exceeded those elicited by adenovirus-vectored HBc. Target-specific T cells were not only more abundant, but also showed a higher degree of polyfunctionality, with HBc-specific CD8+ T cells producing interferon γ and tumour necrosis factor α in addition to granzyme B. This immune phenotype translated into a superior cytotoxic effector activity toward HBc-positive cells in YF17D/HBc-C vaccinated animals in vivo.

CONCLUSIONS

The results presented here show the potential of YF17D/HBc-C as a vaccine candidate to treat CHB, and warrant follow-up studies in preclinical animal models of HBV persistence in which other candidate vaccines have been unable to achieve a sustained virologic response.

LAY SUMMARY

Resolution of CHB requires the induction of strong cellular immune responses. We used the yellow fever vaccine as a vector for HBV antigens and show that it is capable of inducing high levels of HBV-specific T cells that produce multiple cytokines simultaneously and are cytotoxic in vivo.

The effect of chronic viral hepatitis on prognostic value of inflammatory biomarkers in hepatocellular carcinoma

BACKGROUND

Inflammation and the immune system significantly impact the development, progression, and treatment response of hepatocellular carcinoma (HCC). This retrospective study investigated the neutrophil-to-lymphocyte ratio (NLR) as a prognostic biomarker in Western patients with HCC in the setting of chronic viral hepatitis.

METHODS

Patients diagnosed with HCC from 2005 to 2016 were selected from a tertiary care institution. NLR was calculated within 30 days prior to treatment and dichotomized at the median. Kaplan-Meier overall survival (OS) curves and Cox hazard proportional models were utilized. Tumor and liver reserve parameters were included in multivariable analyses (MVA).

RESULTS

A total of 581 patients met inclusion criteria (median age 61.0 yr; 78.3% male; 66.3% Caucasian) with median OS = 34.9 mo. 371 patients (63.9%) had viral hepatitis, of which 350 had hepatitis C (94.3%). The low-NLR group (

CONCLUSIONS

Lower baseline NLR was associated with increased overall survival in HCC. Viral hepatitis serves as an effect modifier of NLR, attenuating its prognostic relevance in this hepatitis C-predominant population.

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Key Words

• carcinoma
• hepatitis C
• hepatocellular
• inflammation
• lymphocytes
• neutrophils

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MESH Headings

• Aged
• Carcinoma, Hepatocellular/blood
• Carcinoma, Hepatocellular/immunology
• Carcinoma, Hepatocellular/mortality
• Carcinoma, Hepatocellular/virology
• Female
• Hepatitis C, Chronic/blood
• Hepatitis C, Chronic/epidemiology
• Hepatitis C, Chronic/immunology
• Hepatitis C, Chronic/virology
• Humans
• Inflammation/blood
• Inflammation/diagnosis
• Inflammation/immunology
• Inflammation/virology
• Kaplan-Meier Estimate
• Liver Neoplasms/blood
• Liver Neoplasms/immunology
• Liver Neoplasms/mortality
• Liver Neoplasms/virology
• Lymphocyte Count
• Lymphocytes/immunology
• Male
• Middle Aged
• Neutrophils/immunology
• Prognosis
• Retrospective Studies
• Risk Factors

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Grants

• UL1 TR001863 NCATS NIH HHS
• CA160741 U.S. Department of Defense
• U.S. Department of Defense

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Affiliation(s)

Cortlandt M. Sellers Section of Interventional RadiologyDepartment of Radiology and Biomedical ImagingYale University School of MedicineNew HavenCTUSA Department of RadiologyBaylor College of MedicineHoustonTXUSA
Johannes Uhlig Section of Interventional RadiologyDepartment of Radiology and Biomedical ImagingYale University School of MedicineNew HavenCTUSA Department for Diagnostic and Interventional RadiologyUniversity Medical Center GoettingenGoettingenGermany
Johannes M. Ludwig Section of Interventional RadiologyDepartment of Radiology and Biomedical ImagingYale University School of MedicineNew HavenCTUSA Department of Diagnostic and Interventional Radiology and NeuroradiologyUniversity Hospital EssenUniversity of Duisburg‐EssenEssenGermany
Jeffrey S. Pollak Section of Interventional RadiologyDepartment of Radiology and Biomedical ImagingYale University School of MedicineNew HavenCTUSA
Tamar H. Taddei Section of Digestive DiseasesDepartment of Internal MedicineYale University School of MedicineNew HavenCTUSA
Stacey M. Stein Section of Medical OncologyDepartment of Internal MedicineYale University School of MedicineNew HavenCTUSA Yale Cancer CenterYale University School of MedicineNew HavenCTUSA
Joseph K. Lim Section of Digestive DiseasesDepartment of Internal MedicineYale University School of MedicineNew HavenCTUSA
Hyun S. Kim Section of Interventional RadiologyDepartment of Radiology and Biomedical ImagingYale University School of MedicineNew HavenCTUSA Section of Medical OncologyDepartment of Internal MedicineYale University School of MedicineNew HavenCTUSA Yale Cancer CenterYale University School of MedicineNew HavenCTUSA

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Animal Models for the Study of Hepatitis B Virus Pathobiology and Immunity: Past, Present, and Future

Hepatitis B virus (HBV) infection is a global public health problem that plagues approximately 240 million people. Chronic hepatitis B (CHB) often leads to liver inflammation and aberrant repair which results in diseases ranging from liver fibrosis, cirrhosis, to hepatocellular carcinoma. Despite its narrow species tropism, researchers have established various in vivo models for HBV or its related viruses which have provided a wealth of knowledge on viral lifecycle, pathogenesis, and immunity. Here we briefly revisit over five decades of endeavor in animal model development for HBV and summarize their advantages and limitations. We also suggest directions for further improvements that are crucial for elucidation of the viral immune-evasion strategies and for development of novel therapeutics for a functional cure.

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.

A hepatitis B virus transgenic mouse model with a conditional, recombinant, episomal genome

Background & Aims

Development of new and more effective therapies against hepatitis B virus (HBV) is limited by the lack of suitable small animal models. The HBV transgenic mouse model containing an integrated overlength 1.3-mer construct has yielded crucial insights, but this model unfortunately lacks covalently closed circular DNA (cccDNA), the episomal HBV transcriptional template, and cannot be cured given that HBV is integrated in every cell.

Methods

To solve these 2 problems, we generated a novel transgenic mouse (HBV1.1X), which generates an excisable circular HBV genome using Cre/LoxP technology. This model possesses a HBV1.1-mer cassette knocked into the ROSA26 locus and is designed for stable expression of viral proteins from birth, like the current HBV transgenic mouse model, before genomic excision with the introduction of Cre recombinase.

Results

We demonstrated induction of recombinant cccDNA (rcccDNA) formation via viral or transgenic Cre expression in HBV1.1X mice, and the ability to regulate HBsAg and HBc expression with Cre in mice. Tamoxifen-inducible Cre could markedly downregulate baseline HBsAg levels from the integrated HBV genome. To demonstrate clearance of HBV from HBV1.1X mice, we administered adenovirus expressing Cre, which permanently and significantly reduced HBsAg and core antigen levels in the murine liver via rcccDNA excision and a subsequent immune response.

Conclusions

The HBV1.1X model is the first Cre-regulatable HBV transgenic mouse model and should be of value to mimic chronic HBV infection, with neonatal expression and tolerance of HBV antigens, and on-demand modulation of HBV expression.

Lay summary

Hepatitis B virus (HBV) can only naturally infect humans and chimpanzees. Mouse models have been developed with the HBV genome integrated into mouse chromosomes, but this prevents mice from being cured. We developed a new transgenic mouse model that allows for HBV to be excised from mouse chromosomes to form a recombinant circular DNA molecule resembling the natural circular HBV genome. HBV expression could be reduced in these mice, enabling curative therapies to be tested in this new mouse model.

The Multiple Functions of B Cells in Chronic HBV Infection

Chronic hepatitis B virus (HBV) infection is one of the main causes of liver diseases, of which the natural history and clinical outcomes are associated with the role of B cells. As humoral immune cells, B cells play a critical role in the process of anti-HBV antibody production. In addition, some studies have also characterized other B cell subsets involved in antigen presentation and regulating the immune response beyond antibody secretion. However, not all B cell subsets play a positive role in the immune response to chronic HBV infection, and various B cell subsets jointly mediate persistent HBV infection, tolerance, and liver damage. Thus, we further sought to elucidate the multiple functions of B cells to gain novel insight into the understanding of chronic hepatitis B (CHB) pathogenesis. We also reviewed the current immunotherapies targeting B cells to explore novel therapeutic interventions for the treatment of chronic HBV infection.

AdrA as a Potential Immunomodulatory Candidate for STING-Mediated Antiviral Therapy That Required Both Type I IFN and TNF-α Production

Several dinucleotide cyclases, including cyclic GMP-AMP synthase, and their involvement in STING-mediated immunity have been extensively studied. In this study, we tested five bacterial diguanylate cyclases from the Gram-negative bacterium Salmonella Enteritidis, identifying AdrA as the most potent inducer of a STING-mediated IFN response. AdrA wild-type (wt) or its inactive version AdrA mutant (mut) were delivered by an adenovirus (Ad) vector. Dendritic cells obtained from wt mice and infected in vitro with Ad vector containing AdrA wt, but not mut, had increased activation markers and produced large amounts of several immunostimulatory cytokines. For dendritic cells derived from STING-deficient mice, no activation was detected. The potential antiviral activity of AdrA was addressed in hepatitis B virus (HBV)-transgenic and adenovirus-associated virus (AAV)-HBV mouse models. Viremia in serum of Ad AdrA wt-treated mice was reduced significantly compared with that in Ad AdrA mut-injected mice. The viral load in the liver at sacrifice was in line with this finding. To further elucidate the molecular mechanism(s) by which AdrA confers its antiviral function, the response in mice deficient in STING or its downstream effector molecules was analyzed. wt and IFN-αR (IFNAR)^-/- animals were additionally treated with anti-TNF-α (Enbrel). Interestingly, albeit less pronounced than in wt mice, in IFNAR^-/- and Enbrel-treated wt mice, a reduction of serum viremia was achieved-an observation that was lost in anti-TNF-α-treated IFNAR^-/- animals. No effect of AdrA wt was seen in STING-deficient animals. Thus, although STING is indispensable for the antiviral activity of AdrA, type I IFN and TNF-α are both required and act synergistically.

Pathogenesis of Viral Hepatitis-Induced Chronic Liver Disease: Role of Extracellular Vesicles

Extracellular vesicles are encapsulated lipid nanoparticles secreted by a variety of cell types in living organisms. They are known to carry proteins, metabolites, nucleic acids, and lipids as their cargoes and are important mediators of intercellular communication. The role of extracellular vesicles in chronic liver disease has been reported. Chronic liver disease such as viral hepatitis accounts for a significant mortality and morbidity burden worldwide. Hepatic fibrosis has been commonly associated with the chronic form of viral hepatitis, which results in end-stage liver disease, including cirrhosis, liver failure, and carcinoma in some patients. In this review, we discuss the potential role of extracellular vesicles in mediating communication between infectious agents (hepatitis B and C viruses) and host cells, and how these complex cell-cell interactions may facilitate the development of chronic liver disease. We will further discuss how understanding their biological mechanism of action might be beneficial for developing therapeutic strategies to treat chronic liver disease.

Immunological Analysis of the Hepatitis B Virus "a" Determinant Displayed on Chimeric Virus-Like Particles of Macrobrachium rosenbergii Nodavirus Capsid Protein Produced in Sf9 Cells

Chimeric virus-like particles (VLPs) have been widely exploited for various purposes including their use as vaccine candidates, particularly due to their ability to induce stronger immune responses than VLPs consisting of single viral proteins. In the present study, VLPs of the Macrobrachium rosenbergii nodavirus (MrNV) capsid protein (Nc) displaying the hepatitis B virus “a” determinant (aD) were produced in Spodoptera frugiperda (Sf9) insect cells. BALB/c mice immunised with the purified chimeric Nc-aD VLPs elicited a sustained titre of anti-aD antibody, which was significantly higher than that elicited by a commercially available hepatitis B vaccine and Escherichia coli-produced Nc-aD VLPs. Immunophenotyping showed that the Sf9-produced Nc-aD VLPs induced proliferation of cytotoxic T-lymphocytes and NK1.1 natural killer cells. Furthermore, enzyme-linked immunospot (ELISPOT)analysis showed the presence of antibody-secreting memory B cells in the mice splenocytes stimulated with the synthetic aD peptide. The significant humoral, natural killer cell and memory B cell immune responses induced by the Sf9-produced Nc-aD VLPs suggest that they present good prospects for use as a hepatitis B vaccine candidate.

The role of hepatitis B surface antibodies in HBV infection, disease and clearance

The clinical sequelae associated with chronic HBV infection is generally regarded as a consequence of an inadequate and inappropriate immune response to active viral replication, predominantly at the T-cell level. However, recent studies on hepatitis B surface antigen (HBsAg)-specific B cells and hepatitis B surface antibody (anti-HB) responses have identified their previously unrecognized role in the pathogenesis of chronic hepatitis B (CHB). These studies have also uncovered novel therapeutic approaches to more effectively target HBsAg loss and seroconversion, an important end point and regarded as a functional cure. Anti-HBs IgG has also been shown to have multiple direct acting antiviral roles with the Fab component directly blocking viral entry, and release while the Fc component has been linked to antibody dependent cellular cytotoxicity. Likewise, the HBsAg-specific B-cell dysfunctionality can be reversed providing new therapeutic opportunities to achieve functional cure in CHB.

Checkpoint Inhibitors and Therapeutic Vaccines for the Treatment of Chronic HBV Infection

Treatment of chronic hepatitis B virus (HBV) infection is highly effective in suppressing viral replication, but complete cure is rarely achieved. In recent years, substantial progress has been made in the development of immunotherapy to treat cancer. Applying these therapies to improve the management of chronic HBV infection is now being attempted, and has become an area of active research. Immunotherapy with vaccines and checkpoint inhibitors can boost T cell functions in vitro, and therefore may be used to reinvigorate the impaired HBV-specific T cell response. However, whether these approaches will suffice and restore antiviral T cell immunity to induce long-term HBV control remains an open question. Recent efforts have begun to describe the phenotype and function of HBV-specific T cells on the single epitope level. An improved understanding of differing T cell specificities and their contribution to HBV control will be instrumental for advancement of the field. In this review, we outline correlates of successful versus inadequate T cell responses to HBV, and discuss the rationale behind therapeutic vaccines and checkpoint inhibitors for the treatment of chronic HBV infection.

The incorporation of cationic property and immunopotentiator in poly (lactic acid) microparticles promoted the immune response against chronic hepatitis B

Biodegradable microparticles (MPs) as vaccine adjuvants have sparked the passion of researchers in recent decades. However, it is still a huge challenge to develop an efficient vaccine delivery system to reverse chronic hepatitis B (CHB). Herein, we integrated a physiochemical merit and an immunopotentiator property in poly (lactic acid) (PLA) MPs and verified the therapeutic effect on CHB model mice. We prepared uniform MPs with insertion of cationic lipid didodecyldimethylammonium bromide (DDAB), which endowed a physiochemical merit for MPs. Such a DDAB-PLA (DP) group raised the recruitment of immune cells to the injection site along with the secretion of chemokines and pro-inflammatory cytokines, promoting the activation of antigen-presenting cells (APCs). Further combination of stimulator of interferon genes (STING) agonist 5,6-dimethylxanthenone-4-acetic acid (DMXAA) (DP-D) elevated 5.8-fold higher interferon regulatory factor 7 (IRF-7) expression compared to that for DP group. The DP group showed preferred lysosome escape advantage, which was in line with the DMXAA release behavior and the intracellular target of DMXAA. In addition, DP-D vaccine augmented the IFN-γ secreting splenocytes and motivated Th1-biased antibodies in a more efficient way than that for the DP group. In the CHB model, the MPs based vaccines achieved 50% HBsAg seroconversion rate, and HBcAg in the liver also got a reduction. DP-D produced higher amount of memory T/B cells to confer protection in a sustained manner. Present work thus provided a promising strategy, via integrating a fine-tuned physiochemical property and an immunopotentiator virtue in the MPs, which synergistically reinforced both humoral and cellular immune responses against CHB.

Advances in Targeting the Innate and Adaptive Immune Systems to Cure Chronic Hepatitis B Virus Infection

“Functional cure” is being pursued as the ultimate endpoint of antiviral treatment in chronic hepatitis B (CHB), which is characterized by loss of HBsAg whether or not anti-HBs antibodies are present. “Functional cure” can be achieved in <10% of CHB patients with currently available therapeutic agents. The dysfunction of specific immune responses to hepatitis B virus (HBV) is considered the major cause of persistent HBV infection. Thus, modulating the host immune system to strengthen specific cellular immune reactions might help eliminate HBV. Strategies are needed to restore/enhance innate immunity and induce HBV-specific adaptive immune responses in a coordinated way. Immune and resident cells express pattern recognition receptors like TLRs and RIG I/MDA5, which play important roles in the induction of innate immunity through sensing of pathogen-associated molecular patterns (PAMPs) and bridging to adaptive immunity for pathogen-specific immune control. TLR/RIG I agonists activate innate immune responses and suppress HBV replication in vitro and in vivo, and are being investigated in clinical trials. On the other hand, HBV-specific immune responses could be induced by therapeutic vaccines, including protein (HBsAg/preS and HBcAg), DNA, and viral vector-based vaccines. More than 50 clinical trials have been performed to assess therapeutic vaccines in CHB treatment, some of which display potential effects. Most recently, using genetic editing technology to generate CAR-T or TCR-T, HBV-specific T cells have been produced to efficiently clear HBV. This review summarizes the progress in basic and clinical research investigating immunomodulatory strategies for curing chronic HBV infection, and critically discusses the rather disappointing results of current clinical trials and future strategies.

Parenteral-Oral Immunization with Plant-Derived HBcAg as a Potential Therapeutic Vaccine against Chronic Hepatitis B

Chronic hepatitis B (CHB) is the cause of severe liver damage, cirrhosis, and hepatocellular carcinoma for over 240 million people worldwide. Nowadays, several types of treatment are being investigated, including immunotherapy using hepatitis B core antigen (HBcAg) assembled into highly immunogenic capsid-like particles (CLPs). Immunogenicity of plant-produced and purified HBcAg, administered parenterally or intranasally, was previously reported. In this study, a novel parenteral-oral vaccination scheme is proposed using plant-derived HBcAg preparations. The antigen for injection was obtained via transient expression in Nicotiana benthamiana. HBcAg-producing transgenic lettuce was lyophilized and used as an orally delivered booster. The intracellular location of plant-produced HBcAg CLPs implies additional protection in the digestive tract during oral immunization. BALB/c mice were intramuscularly primed with 10 µg of the purified antigen and orally boosted twice with 5 or 200 ng of HBcAg. A long-lasting and significant systemic response after boosting with 200 ng HBcAg was induced, with anti-HBc titer of 25,000. Concomitantly, an insignificant mucosal response was observed, with an S-IgA titer of only 500. The profile of IgG isotypes indicates a predominant Th1 type of immune response, supplemented by Th2, after injection-oral vaccination. The results demonstrate that a low dose of parenteral-oral immunization with plant-derived HBcAg can elicit a specific and efficient response. This study presents a potential new pathway of CHB treatment.

[Generation of a novel HBeAg transgenic mice using CRISPR/Cas9 technique]

OBJECTIVE

To generate a new strain of HBeAg transgenic mice using CRISPR/Cas9 technique.

METHODS

Hepatitis B virus (HBV) HBeAg gene was cloned and inserted in the pliver-HBeAg expression frame at the site of Rosa26 gene using CRISPR/Cas9 and homologous recombination techniques to construct the pliver-HBeAg expression vector containing HBeAg gene. The linear DNA fragment containing HBeAg gene was obtained by enzyme digestion. Cas9 mRNA, gRNA and the donor vector were microinjected into fertilized eggs of C57BL/6J mice, which were then transplanted into the uterus of C57BL/6J female surrogate mice to obtain F0 generation mice. The F0 generation mice were identified by long fragment PCR to obtain F0 transgenic mice with HBeAg gene. The positive F0 generation mice were bred with wild-type C57BL/6J mice to produce the F1 mice, which were identified by PCR and sequencing. The positive F1 transgenic mice carrying HBeAg gene were backcrossed until the homozygous offspring transgenic mice were obtained. The genotypes of the offspring mice were identified. The expressions of HBeAg and HBeAb in the heterozygous and homozygous HBeAg transgenic mice were detected by automatic chemiluminescence immunoassay, immune colloidal gold technique and immunohistochemistry method.

RESULTS

A total of 56 F0 mice were obtained, and 2 of them carried homologous recombined HBeAg gene. Six positive F1 mice were obtained, from which 22 homozygous and 29 heterozygous F2 generation HBeAg transgenic mice were obtained. High concentration of HBeAg protein was detected in the peripheral blood of all the positive HBeAg transgenic mice without HBeAb expression. HBeAg expression was detected in the hepatocytes of HBeAg transgenic mice.

CONCLUSIONS

We obtained a new strain of HBeAg transgenic mice with stable expression of HBeAg in the hepatocytes and immune tolerance to HBeAg using CRISPR/Cas9 technique, which provide a new animal model for studying HBV.

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.

A Highly Attenuated Vesicular Stomatitis Virus-Based Vaccine Platform Controls Hepatitis B Virus Replication in Mouse Models of Hepatitis B

Therapeutic vaccines may be an important component of a treatment regimen for curing chronic hepatitis B virus (HBV) infection. We previously demonstrated that recombinant wild-type vesicular stomatitis virus (VSV) expressing the HBV middle surface glycoprotein (MHBs) elicits functional immune responses in mouse models of HBV replication. However, VSV has some undesirable pathogenic properties, and the use of this platform in humans requires further viral attenuation. We therefore generated a highly attenuated VSV that expresses MHBs and contains two attenuating mutations. This vector was evaluated for immunogenicity, pathogenesis, and anti-HBV function in mice. Compared to wild-type VSV, the highly attenuated virus displayed markedly reduced pathogenesis but induced similar MHBs-specific CD8⁺ T cell and antibody responses. The CD8⁺ T cell responses elicited by this vector in naive mice prevented HBV replication in animals that were later challenged by hydrodynamic injection or transduction with adeno-associated virus encoding the HBV genome (AAV-HBV). In mice in which persistent HBV replication was first established by AAV-HBV transduction, subsequent immunization with the attenuated VSV induced MHBs-specific CD8⁺ T cell responses that corresponded with reductions in serum and liver HBV antigens and nucleic acids. HBV control was associated with an increase in the frequency of intrahepatic HBV-specific CD8⁺ T cells and a transient elevation in serum alanine aminotransferase activity. The ability of VSV to induce a robust multispecific T cell response that controls HBV replication combined with the improved safety profile of the highly attenuated vector suggests that this platform offers a new approach for HBV therapeutic vaccination.IMPORTANCE A curative treatment for chronic hepatitis B must eliminate the virus from the liver, but current antiviral therapies typically fail to do so. Immune-mediated resolution of infection occurs in a small fraction of chronic HBV patients, which suggests the potential efficacy of therapeutic strategies that boost the patient's own immune response to the virus. We modified a safe form of VSV to express an immunogenic HBV protein and evaluated the efficacy of this vector in the prevention and treatment of HBV infection in mouse models. Our results show that this vector elicits HBV-specific immune responses that prevent the establishment of HBV infection and reduce viral proteins in the serum and viral DNA/RNA in the liver of mice with persistent HBV replication. These findings suggest that highly attenuated and safe virus-based vaccine platforms have the potential to be utilized for the development of an effective therapeutic vaccine against chronic HBV infection.

Cell and Animal Models for Studying Hepatitis B Virus Infection and Drug Development

Many cell culture and animal models have been used to study hepatitis B virus (HBV) replication and its effects in the liver; these have facilitated development of strategies to control and clear chronic HBV infection. We discuss the advantages and limitations of systems for studying HBV and developing antiviral agents, along with recent advances. New and improved model systems are needed. Cell culture systems should be convenient, support efficient HBV infection, and reproduce responses of hepatocytes in the human body. We also need animals that are fully permissive to HBV infection, convenient for study, and recapitulate human immune responses to HBV and effects in the liver. High-throughput screening technologies could facilitate drug development based on findings from cell and animal models.

Multiple doses of hepatitis B recombinant vaccine for chronic hepatitis B patients with low surface antigen levels: a pilot study

BACKGROUND

Seroclearance of hepatitis B surface antigen (HBsAg) has been rarely achieved in the treatment of chronic hepatitis B (CHB) patients. We administered HBsAg-based recombinant vaccine in patients with low HBsAg concentrations.

METHODS

Twenty hepatitis B e antigen-negative patients, with HBsAg < 1000 IU/ml, were enrolled. Vaccines were administered every 8 weeks for 48 weeks (seven doses). HBsAg levels and anti-HBs were assayed longitudinally until 48 weeks post-vaccination. HLA genotyping and cDNA microarray were performed to search for response predictors.

RESULTS

Nineteen patients completed the study. At the end of vaccination, HBsAg declined significantly (Δ = - 0.27 ± 0.49 log IU/ml, p = 0.0005). The annual decline rate was significantly greater than that of an age-, gender-, and baseline HBsAg-matched control group (Δ = - 0.18 ± 0.46 versus + 0.11 ± 0.42 log IU/ml/year; p = 0.0229). Two patients achieved HBsAg seroclearance. Fourteen had significant HBsAg decline (Δ = - 0.64 ± 0.88 log IU/ml). No significant adverse events occurred during the trial. cDNA microarray identified the top up- and down-regulated genes in responders as HLA-DQ and HLA-DMB, respectively. HLA genotyping identified HLA-DQB1*04, HLA-DRB1*04, and HLA-B*40 as predictors for non-response (p = 0.0499, 0.0152, and 0.0314, respectively).

CONCLUSIONS

In low-level HBsAg CHB patients, serial HBsAg-based vaccinations were safe, resulting in significant HBsAg decline. HLA gene expression and genotypes played a role in vaccine responsiveness (ClinicalTrials.gov Identifier: NCT01817725).

Hepatitis B Virus Adaptation to the CD8+ T Cell Response: Consequences for Host and Pathogen

Chronic viral hepatitis infections are a major public health concern, with an estimated 290 million individuals infected with hepatitis B virus (HBV) globally. This virus has been a passenger in human populations for >30,000 years, and remains highly prevalent in some settings. In order for this endemic pathogen to persist, viral adaptation to host immune responses is pre-requisite. Here, we focus on the interplay between HBV infection and the CD8+ T cell response. We present the evidence that CD8+ T cells play an important role in control of chronic HBV infection and that the selective pressure imposed on HBV through evasion of these immune responses can potentially influence viral diversity, chronicity, and the outcome of infection, and highlight where there are gaps in current knowledge. Understanding the nature and mechanisms of HBV evolution and persistence could shed light on differential disease outcomes, including cirrhosis and hepatocellular carcinoma, and help reach the goal of global HBV elimination by guiding the design of new strategies, including vaccines and therapeutics.

Nature of Host Immunity during Hepatitis B Virus Infection and designing Immune Therapy

Hepatitis B virus (HBV) infections represent one of the major public health problems in global context. More than 2 billion people in the world have been infected with this virus at some point of time in their life and millions are chronically infected, indicating that chronic HBV-infected subjects remain as a living source of HBV transmission. The public health impact of this is tremendous. Considerable numbers of chronic HBV-infected individuals would eventually develop progressive liver diseases and their complications like hepatic failure, liver cirrhosis (LC), and hepatocellular carcinoma (HCC). Epidemiological studies have suggested that about 0.6 to 1.2 million people die annually from HBV-related liver diseases. These figures about death due to HBV and sufferings from HBV-related diseases indicate a notion of medical emergencies about HBV. In addition to these, the impact of HBV on health care delivery system moves beyond these numbers of HBV-related patients and HB-related deaths. This is because significant insights have already been developed about epidemiology, virology, and pathogenesis of HBV. Also, an effective and widely used preventive vaccine is available against HBV. In addition to these, antiviral drugs against HBV have been developed from early 1980s and several such drugs are now available commercially in the open market around the worldwide. Unfortunately, the ongoing therapeutic regimens could not stand the test of time and new insights about HBV pathogenesis are required for the development of new, novel, and evidence-based therapies for chronic HBV infections.

How to cite this article: Akbar SMF, Al-Mahtab M, Khan SI. Nature of Host Immunity during Hepatitis B Virus Infection and designing Immune Therapy. Euroasian J Hepato-Gastroenterol 2018;8(1):42-46.

Viral hepatitis and liver cancer

Hepatitis B and C viruses are a global health problem causing acute and chronic infections that can lead to liver cirrhosis and hepatocellular carcinoma (HCC). These infections are the leading cause for HCC worldwide and are associated with significant mortality, accounting for more than 1.3 million deaths per year. Owing to its high incidence and resistance to treatment, liver cancer is the second leading cause of cancer-related death worldwide, with HCC representing approximately 90% of all primary liver cancer cases. The majority of viral-associated HCC cases develop in subjects with liver cirrhosis; however, hepatitis B virus infection can promote HCC development without prior end-stage liver disease. Thus, understanding the role of hepatitis B and C viral infections in HCC development is essential for the future design of treatments and therapies for this cancer. In this review, we summarize the current knowledge on hepatitis B and C virus hepatocarcinogenesis and highlight direct and indirect risk factors.

This article is part of the themed issue ‘Human oncogenic viruses’.

The Complex Interplay between Chronic Inflammation, the Microbiome, and Cancer: Understanding Disease Progression and What We Can Do to Prevent It

Cancer is a multifaceted condition, in which a senescent cell begins dividing in an irregular manner due to various factors such as DNA damage, growth factors and inflammation. Inflammation is not typically discussed as carcinogenic; however, a significant percentage of cancers arise from chronic microbial infections and damage brought on by chronic inflammation. A hallmark cancer-inducing microbe is Helicobacter pylori and its causation of peptic ulcers and potentially gastric cancer. This review discusses the recent developments in understanding microbes in health and disease and their potential role in the progression of cancer. To date, microbes can be linked to almost every cancer, including colon, pancreatic, gastric, and even prostate. We discuss the known mechanisms by which these microbes can induce cancer growth and development and how inflammatory cells may contribute to cancer progression. We also discuss new treatments that target the chronic inflammatory conditions and their associated cancers, and the impact microbes have on treatment success. Finally, we examine common dietary misconceptions in relation to microbes and cancer and how to avoid getting caught up in the misinterpretation and over inflation of the results.

Hepatocytic expression of human sodium-taurocholate cotransporting polypeptide enables hepatitis B virus infection of macaques

Hepatitis B virus (HBV) is a major global health concern, and the development of curative therapeutics is urgently needed. Such efforts are impeded by the lack of a physiologically relevant, pre-clinical animal model of HBV infection. Here, we report that expression of the HBV entry receptor, human sodium-taurocholate cotransporting polypeptide (hNTCP), on macaque primary hepatocytes facilitates HBV infection in vitro, where all replicative intermediates including covalently closed circular DNA (cccDNA) are present. Furthermore, viral vector-mediated expression of hNTCP on hepatocytes in vivo renders rhesus macaques permissive to HBV infection. These in vivo macaque HBV infections are characterized by longitudinal HBV DNA in serum, and detection of HBV DNA, RNA, and HBV core antigen (HBcAg) in hepatocytes. Together, these results show that expressing hNTCP on macaque hepatocytes renders them susceptible to HBV infection, thereby establishing a physiologically relevant model of HBV infection to study immune clearance and test therapeutic and curative approaches.

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.

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.

Therapeutic vaccination for chronic hepatitis B

A therapeutic vaccine is meant to activate the patient's immune system to fight and finally control or ideally eliminate an already established infectious pathogen. Whereas the success of prophylactic vaccination is based on rapid antibody-mediated neutralization of an invading pathogen, control and elimination of persistent viruses such as hepatitis, herpes or papilloma viruses requires multi-specific and polyfunctional effector T cell responses. These are ideally directed against continuously expressed viral antigens to keep the pathogen in check. Activation of a humoral immune response in order to lower viral antigen load and to limit virus spread, however, confers an additional benefit. Therapeutic vaccines are under development for a number of chronic infections and require an intelligent vaccine design. Hepatitis B virus (HBV) infection may serve as a prime example since a spontaneous, immune-mediated recovery of chronic hepatitis B and an elimination of the virus is possible even if it is observed only in very rare cases. In this review, we summarize the current knowledge and potential improvements of therapeutic vaccines for chronic hepatitis B.

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.

Hepatitis B immunopathogenesis and immunotherapy

Worldwide there are over 248 million chronic carriers of HBV of whom about a third eventually develop severe HBV-related complications. Due to the major limitations of current therapeutic approaches, the development of more effective strategies to improve therapeutic outcomes in chronic hepatitis B (CHB) patients seems crucial. Immune activation plays a critical role in spontaneous viral control; therefore, new modalities based on stimulation of the innate and adaptive immune responses could result in the resolution of infection and are promising approaches. Here, we summarize the HBV immunopathogenesis, and discuss the encouraging results obtained from the promising immune-based innovations, such as therapeutic vaccination, cytokine therapy, cell-based therapies and blocking inhibitory receptors, as current and future immunotherapeutic interventions.

Immuno-potentiating pathway of HBsAg-HBIG immunogenic complex visualized

Chronic viral hepatitis B (CHB) is a major global health problem. A therapeutic vaccine for CHB comprised of yeast-derived recombinant HBsAg-anti-HBs immunogenic complexes (YIC) has been devloped by us. A series of clinical trials has shown its therapeutic efficacy in decreasing HBV viral load and converting serum HBeAg-positive to anti-HBe-positive status in a subpopulation of CHB patients. Herein, we present a study of the immuno-potentiating mechanisms of YIC revealed by live-cell imaging technology. We studied internalization and dissociation of YIC in cells in vitro, and antigen presentation and T cell stimulation in mice. We found that after YIC was internalized via the Fcγ receptors (FcγR) of antigen presenting cells, it was subsequently transferred through early and late endosomal into lysosomal compartments. The dissociation of YIC was mainly observed in the late endosome. Furthermore when YIC were injected into mice, the populations of IFN-γ- and TNF-α-producing CD8+ and CD4+ T cells were higher in the YIC group than in controls receiving antigen or antibody alone. These observations supplement the known mechanisms of YIC action as a therapeutic vaccine for CHB.

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.

Complementary Effects of Interleukin-15 and Alpha Interferon Induce Immunity in Hepatitis B Virus Transgenic Mice

In chronic hepatitis B (CHB), failure to control hepatitis B virus (HBV) is associated with T cell dysfunction. HBV transgenic mice mirror many features of the human disease, including T cell unresponsiveness, and thus represent an appropriate model in which to test novel therapeutic strategies. To date, the tolerant state of CD8⁺ T cells in these animals could be altered only by strong immunogens or by immunization with HBV antigen-pulsed dendritic cells; however, the effectors induced were unable to suppress viral gene expression or replication. Because of the known stimulatory properties of alpha interferon (IFN-α) and interleukin-15 (IL-15), this study explored the therapeutic potential of liver-directed gene transfer of these cytokines in a murine model of CHB using adeno-associated virus (AAV) delivery. This combination not only resulted in a reduction in the viral load in the liver and the induction of an antibody response but also gave rise to functional and specific CD8⁺ immunity. Furthermore, when splenic and intrahepatic lymphocytes from IFN-α- and IL-15-treated animals were transferred to new HBV carriers, partial antiviral immunity was achieved. In contrast to previous observations made using either cytokine alone, markedly attenuated PD-L1 induction in hepatic tissue was observed upon coadministration. An initial study with CHB patient samples also gave promising results. Hence, we demonstrated synergy between two stimulating cytokines, IL-15 and IFN-α, which, given together, constitute a potent approach to significantly enhance the CD8⁺ T cell response in a state of immune hyporesponsiveness. Such an approach may be useful for treating chronic viral infections and neoplastic conditions.

IMPORTANCE With 350 million people affected worldwide and 600,000 annual deaths due to HBV-induced liver cirrhosis and/or hepatocellular carcinoma, chronic hepatitis B (CHB) is a major health problem. However, current treatment options are costly and not very effective and/or need to be administered for life. The unprecedented efficacy of the strategy described in our paper may offer an alternative and is relevant for a broad spectrum of readers because of its clear translational importance to other chronic viral infections in which a hyporesponsive antigen-specific T cell repertoire prevents clearance of the pathogen.

Immune therapy for hepatitis B

Although several antiviral drugs are now available for treatment of patients with chronic hepatitis B (CHB), sustained off-treatment clinical responses and containment of CHB-related complications are not achieved in majority of CHB patients by antiviral therapy. In addition, use of these drugs is endowed with substantial long term risk of viral resistance and drug toxicity. The infinite treatment regimens of antiviral drugs for CHB patients are also costly and usually unbearable by most patients of developing and resource-constrained countries. Taken together, there is a pressing need to develop new and innovative therapeutic approaches for CHB patients. Immune therapy seems to be an alternate therapeutic approach for CHB patients because impaired or distorted or diminished immune responses have been detected in most of these patients. Also, investigators have shown that restoration or induction of proper types of immune responses may have therapeutic implications in CHB. Various immunomodulatory agents have been used to treat patients with CHB around the world and the outcomes of these clinical trials show that the properties of immune modulators and nature and designing of immune therapeutic regimens seem to be highly relevant in the context of treatment of CHB patients. In this review, the general properties and specific features of immune therapy for CHB have been discussed for developing the guidelines of effective regimens of immune therapy for CHB.

Experimental in vitro and in vivo models for the study of human hepatitis B virus infection

Chronic infection with the hepatitis B virus (HBV) affects an estimate of 240 million people worldwide despite the availability of a preventive vaccine. Medication to repress viral replication is available but a cure is rarely achieved. The narrow species and tissue tropism of the virus and the lack of reliable in vitro models and laboratory animals susceptible to HBV infection, have limited research progress in the past. As a result, several aspects of the HBV life cycle as well as the network of virus host interactions occurring during the infection are not yet understood. Only recently, the identification of the functional cellular receptor enabling HBV entry has opened new possibilities to establish innovative infection systems. Regarding the in vivo models of HBV infection, the classical reference was the chimpanzee. However, because of the strongly restricted use of great apes for HBV research, major efforts have focused on the development of mouse models of HBV replication and infection such as the generation of humanized mice. This review summarizes the animal and cell culture based models currently available for the study of HBV biology. We will discuss the benefits and caveats of each model and present a selection of the most important findings that have been retrieved from the respective systems.

Fibronectin EDA and CpG synergize to enhance antigen-specific Th1 and cytotoxic responses

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FNIII 11-EDA and CpG synergize in vitro to enhance activation of dendritic cells.

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Immunization with both adjuvants induces a potent antigen-specific Th1 response in vivo.

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Co-adjuvanted OVA mediates regression of E.G7-OVA tumors through CTL response.

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Co-adjuvanted HBsAg induces seroconversion and clearance of circulating virus in HBV-Tg mice.

Subunit vaccines, employing purified protein antigens rather than intact pathogens, require the addition of adjuvants for enhanced immunogenicity with a correct balance between strong activation of the immune system and low toxicity. Here we show that the endogenous (i.e., autologous) non-toxic TLR4 agonist extra domain A type III repeat of fibronectin (FNIII EDA) can synergize with the exogenous (i.e., bacterial), toxic-at-high-dose, TLR9 agonist CpG to induce efficient cellular immune responses while keeping the dose of CpG low. The efficacy of the combined TLR agonists, even at half-doses, led to stronger dendritic cell activation, enhanced cytotoxic T lymphocyte activation as well as stronger humoral response, compared to the individual agonists given at full doses. Immune cells induced after vaccination with the co-adjuvanted formulation could mediate tumor regression in an E.G7-OVA tumor model, and eradicate circulating hepatitis B virus (HBV) in a transgenic HBV model. Together, these results show that endogenous TLR agonists, such as variants of FNIII EDA, can synergize with exogenous TLR ligands, such as CpG, and strongly enhance cellular immune responses, while improving their safety profile.

Clearing Persistent Extracellular Antigen of Hepatitis B Virus: An Immunomodulatory Strategy To Reverse Tolerance for an Effective Therapeutic Vaccination

Development of therapeutic vaccines/strategies to control chronic hepatitis B virus (HBV) infection has been challenging because of HBV-induced tolerance. In this study, we explored strategies for breaking tolerance and restoring the immune response to the HBV surface Ag in tolerant mice. We demonstrated that immune tolerance status is attributed to the level and duration of circulating HBsAg in HBV carrier models. Removal of circulating HBsAg by a monoclonal anti-HBsAg Ab in tolerant mice could gradually reduce tolerance and reestablish B cell and CD4(+) T cell responses to subsequent Engerix-B vaccination, producing protective IgG. Furthermore, HBsAg-specific CD8(+) T cells induced by the addition of a TLR agonist resulted in clearance of HBV in both serum and liver. Thus, generation of protective immunity can be achieved by clearing extracellular viral Ag with neutralizing Abs followed by vaccination.

Asian-Pacific clinical practice guidelines on the management of hepatitis B: a 2015 update

Worldwide, some 240 million people have chronic hepatitis B virus (HBV), with the highest rates of infection in Africa and Asia. Our understanding of the natural history of HBV infection and the potential for therapy of the resultant disease is continuously improving. New data have become available since the previous APASL guidelines for management of HBV infection were published in 2012. The objective of this manuscript is to update the recommendations for the optimal management of chronic HBV infection. The 2015 guidelines were developed by a panel of Asian experts chosen by the APASL. The clinical practice guidelines are based on evidence from existing publications or, if evidence was unavailable, on the experts' personal experience and opinion after deliberations. Manuscripts and abstracts of important meetings published through January 2015 have been evaluated. This guideline covers the full spectrum of care of patients infected with hepatitis B, including new terminology, natural history, screening, vaccination, counseling, diagnosis, assessment of the stage of liver disease, the indications, timing, choice and duration of single or combination of antiviral drugs, screening for HCC, management in special situations like childhood, pregnancy, coinfections, renal impairment and pre- and post-liver transplant, and policy guidelines. However, areas of uncertainty still exist, and clinicians, patients, and public health authorities must therefore continue to make choices on the basis of the evolving evidence. The final clinical practice guidelines and recommendations are presented here, along with the relevant background information.

Chlamydia trachomatis: Protective Adaptive Responses and Prospects for a Vaccine

Chlamydia trachomatis is the most common cause of sexually transmitted bacterial infection globally. These infections translate to a significant public health burden, particularly women's healthcare costs due to serious disease sequelae such as pelvic inflammatory disease (PID), tubal factor infertility, chronic pelvic pain, and ectopic pregnancy. There is no evidence that natural immunity can provide complete, long-term protection necessary to prevent chronic pathology, making human vaccine development critical. Vaccine design will require careful consideration of protective versus pathological host-response mechanisms in concert with elucidation of optimal antigens and adjuvants. Evidence suggests that a Th1 response, facilitated by IFN-γ-producing CD4 T cells, will be instrumental in generating long-term, sterilizing immunity. Although the role of antibodies is not completely understood, they have exhibited a protective effect by enhancing chlamydial clearance. Future work will require investigation of broadly neutralizing antibodies and antibody-augmented cellular immunity to successfully design a vaccine that potently elicits both arms of the immune response. Sterilizing immunity is the ultimate goal. However, vaccine-induced partial immunity that prevents upper genital tract infection and inflammation would be cost-effective compared to current screening and treatment strategies. In this chapter, we examine evidence from animal and human studies demonstrating protective adaptive immune responses to Chlamydia and discuss future challenges and prospects for vaccine development.

AIC649 Induces a Bi-Phasic Treatment Response in the Woodchuck Model of Chronic Hepatitis B

AIC649 has been shown to directly address the antigen presenting cell arm of the host immune defense leading to a regulated cytokine release and activation of T cell responses. In the present study we analyzed the antiviral efficacy of AIC649 as well as its potential to induce functional cure in animal models for chronic hepatitis B. Hepatitis B virus transgenic mice and chronically woodchuck hepatitis virus (WHV) infected woodchucks were treated with AIC649, respectively. In the mouse system AIC649 decreased the hepatitis B virus titer as effective as the “gold standard”, Tenofovir. Interestingly, AIC649-treated chronically WHV infected woodchucks displayed a bi-phasic pattern of response: The marker for functional cure—hepatitis surface antigen—first increased but subsequently decreased even after cessation of treatment to significantly reduced levels. We hypothesize that the observed bi-phasic response pattern to AIC649 treatment reflects a physiologically “concerted”, reconstituted immune response against WHV and therefore may indicate a potential for inducing functional cure in HBV-infected patients.

Dendritic cells pulsed with Hsp70 and HBxAg induce specific antitumor immune responses in hepatitis B virus-associated hepatocellular carcinoma

Previous studies have drawn attention to dendritic cell (DC) vaccines; particularly the application of the tumor-associated antigen-targeted DC vaccine. The present study analyzed DCs derived from a normal individual and pulsed the cells with heat shock protein 70 peptide (Hsp70) and/or hepatitis B virus x antigen (HBxAg), a hepatocellular carcinoma (HCC)-associated antigen. It was then investigated whether this method of vaccination induced strong therapeutic antitumor immunity. The results revealed that the Hsp70/HBxAg complex-activated phenotype improves the functional maturation of DCs compared with using Hsp70 or HBxAg alone. Compared with either Hsp70 or HBxAg alone, matured DCs pulsed with the Hsp70/HBxAg complex stimulated a high level of autologous T-cell proliferation and induced HCC-specific cytotoxic T lymphocytes, which specifically killed HCC cells through a major histocompatibility complex class I mechanism. These results indicated that a vaccination therapy using DCs co-pulsed with the Hsp70/HBxAg complex is an effective strategy for immunotherapy and may offer a useful approach to protect against HCC.

Hepatitis B virus therapy: What’s the future holding for us?

Hepatitis B is one of the leading causes of liver cancer worldwide and unfortunately the number of people affected with hepatitis B virus (HBV) infection is still on the rise. Although the HBV has been known to cause fatal illness since decades but the population effected by this lethal virus have still only a few options for its management. The major treatment strategies include interferons and nucleos(t)ide analogues. These agents have so far produced unsatisfactory results in terms of complete virus eradication. Interferons cannot be used for long term therapy because of their potential side effects. Prolong treatment with nucleos(t)ide analogues has also been reported to cause serious side effects besides the increasing resistance by the virus. The need for new innovative solutions for treatment of HBV has been realized by global research institutes and pharmaceutical industry. Present review focuses in detail on the new ideas that are being transformed into therapeutic tools for use as future therapies in HBV infection. Modern drug designing and screening methods have made the drug discovery process shorter and more reliable. HBV therapeutics will take a new turn in coming years owing to these intelligent drug designing and screening methods. Future therapy of HBV is aiming to include the use of vaccines (both prophylactic and therapeutic), immunomodulators such as antibodies, non-nucleoside antivirals such as RNAi and inhibitors of viral life cycle.