Adenoviral delivery of recombinant hepatitis B virus expressing foreign antigenic epitopes for immunotherapy of persistent viral infection

Studying T Cell Responses to Hepatotropic Viruses in the Liver Microenvironment

T cells play an important role in the clearance of hepatotropic viruses but may also cause liver injury and contribute to disease progression in chronic hepatitis B and C virus infections which affect millions of people worldwide. The liver provides a unique microenvironment of immunological tolerance and hepatic immune regulation can modulate the functional properties of T cell subsets and influence the outcome of a virus infection. Extensive research over the last years has advanced our understanding of hepatic conventional CD4+ and CD8+ T cells and unconventional T cell subsets and their functions in the liver environment during acute and chronic viral infections. The recent development of new small animal models and technological advances should further increase our knowledge of hepatic immunological mechanisms. Here we provide an overview of the existing models to study hepatic T cells and review the current knowledge about the distinct roles of heterogeneous T cell populations during acute and chronic viral hepatitis.

DNA Engineering and Hepatitis B Virus Replication

Recombinant DNA technology is a vital method in human hepatitis B virus (HBV), producing reporter viruses or vectors for gene transferring. Researchers have engineered several genes into the HBV genome for different purposes; however, a systematic analysis of recombinant strategy is lacking. Here, using a 500-bp deletion strategy, we scanned the HBV genome and identified two regions, region I (from nt 2,118 to 2,814) and region II (from nt 99 to 1,198), suitable for engineering. Ten exogenous genes, including puromycin N-acetyl transferase gene (Pac), blasticidin S deaminase gene (BSD), Neomycin-resistance gene (Neo), Gaussia luciferase (Gluc), NanoLuc (Nluc), copGFP, mCherry, UnaG, eGFP, and tTA1, were inserted into these two regions and fused into the open reading frames of hepatitis B core protein (HBC) and hepatitis B surface protein (HBS) via T2A peptide. Recombination of 9 of the 10 genes at region 99-1198 and 5 of the 10 genes at region 2118-2814 supported the formation of relaxed circular (RC) DNA. HBV DNA and HBV RNA assays implied that exogenous genes potentially abrogate RC DNA by inducing the formation of adverse secondary structures. This hypothesis was supported because sequence optimization of the UnaG gene based on HBC sequence rescued RC DNA formation. Findings from this study provide an informative basis and a valuable method for further constructing and optimizing recombinant HBV and imply that DNA sequence might be intrinsically a potential source of selective pressure in the evolution of HBV.

Animal Models of Hepatitis B Virus Infection-Success, Challenges, and Future Directions

Chronic hepatitis B virus (HBV) infection affects more than 250 million people worldwide, which greatly increases the risk for terminal liver diseases, such as liver cirrhosis and hepatocellular carcinoma (HCC). Even though current approved antiviral therapies, including pegylated type I interferon (IFN) and nucleos(t)ide analogs, can effectively suppress viremia, HBV infection is rarely cured. Since HBV exhibits a narrow species tropism and robustly infects only humans and higher primates, progress in HBV research and preclinical testing of antiviral drugs has been hampered by the scarcity of suitable animal models. Fortunately, a series of surrogate animal models have been developed for the study of HBV. An increased understanding of the barriers towards interspecies transmission has aided in the development of human chimeric mice and has greatly paved the way for HBV research in vivo, and for evaluating potential therapies of chronic hepatitis B. In this review, we summarize the currently available animal models for research of HBV and HBV-related hepadnaviruses, and we discuss challenges and future directions for improvement.

Advanced Therapeutics, Vaccinations, and Precision Medicine in the Treatment and Management of Chronic Hepatitis B Viral Infections; Where Are We and Where Are We Going?

The management of chronic hepatitis B virus (CHB) infection is an area of massive unmet clinical need worldwide. In spite of the development of powerful nucleoside/nucleotide analogue (NUC) drugs, and the widespread use of immune stimulators such as interferon-alpha (IFNα) or PEGylated interferon-alpha (PEG-IFNα), substantial improvements in CHB standards of care are still required. We believe that the future for CHB treatment now rests with advanced therapeutics, vaccination, and precision medicine, if all are to bring under control this most resilient of virus infections. In spite of a plethora of active drug treatments, anti-viral vaccinations and diagnostic techniques, the management of CHB infection remains unresolved. The reason for this is the very complexity of the virus replication cycle itself, giving rise to multiple potential targets for therapeutic intervention some of which remain very intractable indeed. Our review is focused on discussing the potential impact that advanced therapeutics, vaccinations and precision medicine could have on the future management of CHB infection. We demonstrate that advanced therapeutic approaches for the treatment of CHB, in the form of gene and immune therapies, together with modern vaccination strategies, are now emerging rapidly to tackle the limitations of current therapeutic approaches to CHB treatment in clinic. In addition, precision medicine approaches are now gathering pace too, starting with personalized medicine. On the basis of this, we argue that the time has now come to accelerate the design and creation of precision therapeutic approaches (PTAs) for CHB treatment that are based on advanced diagnostic tools and nanomedicine, and which could maximize CHB disease detection, treatment, and monitoring in ways that could genuinely eliminate CHB infection altogether.

Total saponins extracted from Abrus cantoniensis Hance suppress hepatitis B virus replication in vitro and in rAAV8-1.3HBV transfected mice

ETHNOPHARMACOLOGICAL RELEVANCE

Hepatitis B, an infectious disease caused by hepatitis B virus (HBV), is still a serious problem affecting global public health. Abrus cantoniensis Hance (AC), a traditional Chinese medicinal herb, has been used as a folk medicine for treating hepatitis in China from ancient times. However, its active ingredients are still unclear.

AIM OF STUDY

Our previous study indicated that saponins extracted from AC (ACS) were the active anti-HBV ingredients in AC. This study aimed to further investigate the anti-HBV effect of ACS in vitro and in vivo.

MATERIALS AND METHODS

HepG2.2.15 cells which consecutively produce HBV DNA and HBV antigens were used for in vitro test, and C57BL/6 mice infected by a recombinant adeno-associated virus 8 vector carrying 1.3 copies of HBV genome (rAAV8-HBV1.3) were used for in vivo test. The histopathological changes and the immune indices were evaluated in mice model. Genechip was conducted to identify genes and pathways regulated by ACS in HepG2.2.15 cells.

RESULTS

In this study, we confirmed that ACS treatment prominently inhibited production of HBV DNA, Hepatitis Be Antigen (HBeAg), and Hepatitis B surface antigen (HBsAg) in HepG2.2.15 cells. ACS treatment also decreased serum HBsAg, HBeAg, and HBV DNA level in rAAV8-1.3HBV transfected mice, which is in accordance with the in vitro results. Moreover, HBV infection-induced liver inflammation was significantly relieved by ACS, which could be observed in H&E staining and immunohistochemistry of HBcAg. ACS treatment elevated IFN-γ level in mice serum and increased CD4⁺ T cell percentage in splenocytes. KEGG pathway analysis showed that phenylalanine metabolism pathway and tyrosine metabolism pathway were greatly regulated by ACS treatment.

CONCLUSION

ACS exerted potent inhibitory effects on HBV replication both in vivo and in vitro, which may provide basis for its potential clinical usage.

A dendritic cell receptor-targeted chimeric immunotherapeutic protein (C-HBV) for the treatment of chronic hepatitis B

In chronic Hepatitis B Virus (HBV) infections HBV-specific T cells are functionally impaired. Immunotherapy may restore HBV-specific T cell responses essential for sustained disease remission off-treatment and induction of a functional cure. Chimigen® Molecules are fusion proteins of antigen(s) with the Fc fragment of a xenotypic antibody designed to target specific receptors on dendritic cells (DCs). Here we describe the production and pre-clinical evaluation of Chimigen® HBV (C-HBV), containing HBV PreS1 and PreS2 peptide fragments, HBV core and murine Fc, produced in insect cells. C-HBV binding to immature DCs and internalization by endocytosis was FcγRII (CD32) and mannose receptor (CD206) dependent and led to increased MHC I and MHC II surface expression. Upon exposure of human T cells isolated from HBV un-infected healthy and chronically HBV-infected donors to C-HBV-pulsed mature DCs ex vivo, C-HBV induced vigorous T cell proliferation and enhanced expression of IFN-γ, TNF-α, perforin and granzyme B in both CD4⁺ and CD8⁺ T cell subsets. Re-stimulation of C-HBV-activated T cells from chronically infected donors with HBV PreS1/PreS2 and core overlapping peptides induced IFN-γ production in both CD4⁺ and CD8⁺ populations. C-HBV-activation of peripheral blood mononuclear cells (PBMCs) from chronically HBV-infected patients stimulated granzyme B production by CD4⁺CD25^- T responder (Tresp) cells, accompanied by an increase in Annexin V staining on CD4⁺CD25⁺ T regulatory (Treg) cell phenotype, consistent with apoptosis. The observed HBV-specific cellular responses induced by C-HBV ex vivo suggest that C-HBV is a promising immunotherapeutic candidate for the treatment of chronic HBV infections.

Efficient genome replication of hepatitis B virus using adenovirus vector: a compact pregenomic RNA-expression unit

The complicated replication mechanisms of hepatitis B virus (HBV) have impeded HBV studies and anti-HBV therapy development as well. Herein we report efficient genome replication of HBV applying adenovirus vectors (AdVs) showing high transduction efficiency. Even in primary hepatocytes derived from humanized mice the transduction efficiencies using AdVs were 450-fold higher compared than those using plasmids. By using an expression unit consisting of the CMV promoter, 1.03-copy HBV genome and foreign poly(A) signal, we successfully generated an improved AdV (HBV103-AdV) that efficiently provided 58 times more pregenomic RNA than previously reported AdVs. The HBV103-AdV-mediated HBV replication was easily and precisely detected using quantitative real-time PCR in primary hepatocytes as well as in HepG2 cells. Notably, when the AdV containing replication-defective HBV genome of 1.14 copy was transduced, we observed that HBV DNA-containing circular molecules (pseudo-ccc DNA) were produced, which were probably generated through homologous recombination. However, the replication-defective HBV103-AdV hardly yielded the pseudo-ccc, probably because the repeated sequences are vey short. Additionally, the efficacies of entecavir and lamivudine were quantitatively evaluated using this system at only 4 days postinfection with HBV103-AdVs. Therefore, this system offers high production of HBV genome replication and thus could become used widely.

Engineering Hepadnaviruses as Reporter-Expressing Vectors: Recent Progress and Future Perspectives

The Hepadnaviridae family of small, enveloped DNA viruses are characterized by a strict host range and hepatocyte tropism. The prototype hepatitis B virus (HBV) is a major human pathogen and constitutes a public health problem, especially in high-incidence areas. Reporter-expressing recombinant viruses are powerful tools in both studies of basic virology and development of antiviral therapeutics. In addition, the highly restricted tropism of HBV for human hepatocytes makes it an ideal tool for hepatocyte-targeting in vivo applications such as liver-specific gene delivery. However, compact genome organization and complex replication mechanisms of hepadnaviruses have made it difficult to engineer replication-competent recombinant viruses that express biologically-relevant cargo genes. This review analyzes difficulties associated with recombinant hepadnavirus vector development, summarizes and compares the progress made in this field both historically and recently, and discusses future perspectives regarding both vector design and application.

CRISPR/Cas9 nickase-mediated disruption of hepatitis B virus open reading frame S and X

Current antiviral therapies cannot cure hepatitis B virus (HBV) infection; successful HBV eradication would require inactivation of the viral genome, which primarily persists in host cells as episomal covalently closed circular DNA (cccDNA) and, to a lesser extent, as chromosomally integrated sequences. However, novel designer enzymes, such as the CRISPR/Cas9 RNA-guided nuclease system, provide technologies for developing advanced therapy strategies that could directly attack the HBV genome. For therapeutic application in humans, such designer nucleases should recognize various HBV genotypes and cause minimal off-target effects. Here, we identified cross-genotype conserved HBV sequences in the S and X region of the HBV genome that were targeted for specific and effective cleavage by a Cas9 nickase. This approach disrupted not only episomal cccDNA and chromosomally integrated HBV target sites in reporter cell lines, but also HBV replication in chronically and de novo infected hepatoma cell lines. Our data demonstrate the feasibility of using the CRISPR/Cas9 nickase system for novel therapy strategies aiming to cure HBV infection.