The doses of plasmid backbone plays a major role in determining the HBV clearance in hydrodynamic injection mouse model

Hepatitis B: Model Systems and Therapeutic Approaches

Hepatitis B virus (HBV) infection is a major global health issue and ranks among the top causes of liver cirrhosis and hepatocellular carcinoma. Although current antiviral medications, including nucleot(s)ide analogs and interferons, could inhibit the replication of HBV and alleviate the disease, HBV cannot be fully eradicated. The development of cellular and animal models for HBV infection plays an important role in exploring effective anti-HBV medicine. During the past decades, advancements in several cell culture systems, such as HepG2.2.15, HepAD38, HepaRG, hepatocyte-like cells, and primary human hepatocytes, have propelled the research in inhibiting HBV replication and expression and thus enriched our comprehension of the viral life cycle and enhancing antiviral drug evaluation efficacy. Mouse models, in particular, have emerged as the most extensively studied HBV animal models. Additionally, the present landscape of HBV therapeutics research now encompasses a comprehensive assessment of the virus's life cycle, targeting numerous facets and employing a variety of immunomodulatory approaches, including entry inhibitors, strategies aimed at cccDNA, RNA interference technologies, toll-like receptor agonists, and, notably, traditional Chinese medicine (TCM). This review describes the attributes and limitations of existing HBV model systems and surveys novel advancements in HBV treatment modalities, which will offer deeper insights toward discovering potentially efficacious pharmaceutical interventions.

MDSC-targeted liposomal all-trans retinoic acid suppresses mMdscs and improves immunotherapy in HBV infection

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) are evolving as a prominent determinant in cancer occurrence and development and are functionally found to suppress T cells in cancer. Not much research is done regarding its involvement in viral infections. This research was designed to investigate the role of MDSCs in hepatitis B virus (HBV) infection and how targeting these cells with our novel all-trans retinoic acid encapsulated liposomal formulation could improve immunotherapy in C57BL/6 mice.

METHODS

Ten micrograms (10 μg) of plasmid adeno-associated virus (pAAV/HBV 1.2, genotype A) was injected hydrodynamically via the tail vein of C57BL/6 mice. An all-trans retinoic acid encapsulated liposomal formulation (L-ATRA) with sustained release properties was used in combination with tenofovir disoproxil fumarate (TDF), a nucleotide analog reverse transcriptase inhibitor (nRTI) to treat the HBV infection. The L-ATRA formulation was given at a dose of 5 mg/kg intravenously (IV) twice a week. The TDF was given orally at 30 mg/kg daily.

RESULTS

Our results revealed that L-ATRA suppresses MDSCs in HBV infected mice and enhanced T-cell proliferation in vitro. In vivo studies showed higher and improved immunotherapeutic effect in mice that received L-ATRA and TDF concurrently in comparison with the groups that received monotherapy. Lower HBV DNA copies, lower concentrations of HBsAg and HBeAg, lower levels of ALT and AST and less liver damage were seen in the mice that received the combination therapy of L-ATRA + TDF.

CONCLUSIONS

In effect, targeting MDSCs with the combination of L-ATRA and TDF effectively reduced mMDSC and improved immunotherapy in the HBV infected mice. Targeting MDSCs could provide a breakthrough in the fight against hepatitis B virus infection.

High-pressure Hydrodynamic Injection as a Method of Establishing Hepatitis B Virus Infection in Mice

Among several existing mouse models for hepatitis B virus (HBV) infection, the high-pressure hydrodynamic injection (HDI) method is frequently used in HBV research due to its economic advantages and ease of implementation. The use of the HDI method is influenced by factors such as mouse genetic background, age, sex, and the type of HBV plasmid used. This overview provides a multidimensional analysis and comparison of various factors that influence the effectiveness of the HBV mouse model established through HDI. The goal is to provide a summary of information for researchers who create HBV models in mice.

Antibiotic-induced gut bacteria depletion has no effect on HBV replication in HBV immune tolerance mouse model

Commensal microbiota is closely related to Hepatitis B virus (HBV) infection. Gut bacteria maturation accelerates HBV immune clearance in hydrodynamic injection (HDI) HBV mouse model. However, the effect of gut bacteria on HBV replication in recombinant adeno-associated virus (AAV)-HBV mouse model with immune tolerance remains obscure. We aim to investigate its role on HBV replication in AAV-HBV mouse model. C57BL/6 mice were administrated with broad-spectrum antibiotic mixtures (ABX) to deplete gut bacteria and intravenously injected with AAV-HBV to establish persistent HBV replication. Gut microbiota community was analyzed by fecal qPCR assay and 16S ribosomal RNA (rRNA) gene sequencing. HBV replication markers in blood and liver were determined by ELISA, qPCR assay and Western blot at indicated time points. Immune response in AAV-HBV mouse model was activated through HDI of HBV plasmid or poly(I:C) and then detected by quantifying the percentage of IFN-γ⁺/CD8⁺ T cells in the spleen via flow cytometry as well as the splenic IFN-γ mRNA level via qPCR assay. We found that antibiotic exposure remarkably decreased gut bacteria abundance and diversity. Antibiotic treatment failed to alter the levels of serological HBV antigens, intrahepatic HBV RNA transcripts and HBc protein in AAV-HBV mouse model, but contributed to HBsAg increase after breaking of immune tolerance. Overall, our data uncovered that antibiotic-induced gut bacteria depletion has no effect on HBV replication in immune tolerant AAV-HBV mouse model, providing new thoughts for elucidating the correlation between gut bacteria dysbiosis by antibiotic abuse and clinical chronic HBV infection.

In Vivo Mouse Models for Hepatitis B Virus Infection and Their Application

Despite the availability of effective vaccination, hepatitis B virus (HBV) infection continues to be a major challenge worldwide. Research efforts are ongoing to find an effective cure for the estimated 250 million people chronically infected by HBV in recent years. The exceptionally limited host spectrum of HBV has limited the research progress. Thus, different HBV mouse models have been developed and used for studies on infection, immune responses, pathogenesis, and antiviral therapies. However, these mouse models have great limitations as no spread of HBV infection occurs in the mouse liver and no or only very mild hepatitis is present. Thus, the suitability of these mouse models for a given issue and the interpretation of the results need to be critically assessed. This review summarizes the currently available mouse models for HBV research, including hydrodynamic injection, viral vector-mediated transfection, recombinant covalently closed circular DNA (rc-cccDNA), transgenic, and liver humanized mouse models. We systematically discuss the characteristics of each model, with the main focus on hydrodynamic injection mouse model. The usefulness and limitations of each mouse model are discussed based on the published studies. This review summarizes the facts for considerations of the use and suitability of mouse model in future HBV studies.

Modeling Hepatotropic Viral Infections: Cells vs. Animals

The lack of an appropriate platform for a better understanding of the molecular basis of hepatitis viruses and the absence of reliable models to identify novel therapeutic agents for a targeted treatment are the two major obstacles for launching efficient clinical protocols in different types of viral hepatitis. Viruses are obligate intracellular parasites, and the development of model systems for efficient viral replication is necessary for basic and applied studies. Viral hepatitis is a major health issue and a leading cause of morbidity and mortality. Despite the extensive efforts that have been made on fundamental and translational research, traditional models are not effective in representing this viral infection in a laboratory. In this review, we discuss in vitro cell-based models and in vivo animal models, with their strengths and weaknesses. In addition, the most important findings that have been retrieved from each model are described.

NK cells contribute to hepatic CD8+ T cell failure in hepatitis B virus-carrier mice after alcohol consumption

Despite the fact that both Hepatitis B virus (HBV) infection and excessive alcohol consumption represent health problems worldwide, the mechanism by which alcohol affected the progression of HBV-associated liver disease are not completely understood. Therefore, we studied how alcohol affects the development of HBV infection and the role of T cells and NK cells in the antiviral response. Mononuclear cells (MNCs) derived from HBV-carrier mice and wild type (WT) mice were characterized for phenotype by flow cytometry, HBV antigen and gene expression were detected by Radio Immunoassay (RIA), immunohistochemistry and quantitative real-time (qRT)-PCR. Metabolomics changes were detected in mice liver tissue based on ultra high performance liquid tandem chromatography quadrupole time of flight mass spectrometry (UHPLC-QTOFMS). The mice after ethanol consumption shows higher levels of HBV surface Ag (HBsAg), HBV core antigen (HBcAg) and HBV 3.5 kb RNA expression, and a lower level of CD8⁺ T cells during HBV persistence, with an increased lymphocyte activation gene-3 (LAG-3) expression on CD8⁺ T cell. In addition, the energy metabolism was downregulated and the oxidative stress was upregulated in the liver tissue. Furthermore, NK cells depletion results in a lower levels of HBV surface Ag (HBsAg) and HBV 3.5 kb RNA expression, and a higher level of CD8⁺ T cells with reduced expression of LAG-3. In conclusion, alcohol abuse induces CD8⁺ T cells failure after acute HBV infection, but depletion of NK cells could retore CD8⁺ T cell activity. Moreover, downregulation of energy metabolism and upregulation of oxidative stress may also contribute to CD8⁺ T cell failure.