Animal models for the study of HBV replication and its variants

Toll-Like Receptor Response to Hepatitis B Virus Infection and Potential of TLR Agonists as Immunomodulators for Treating Chronic Hepatitis B: An Overview

Chronic hepatitis B virus (HBV) infection remains a major global health problem. The immunopathology of the disease, especially the interplay between HBV and host innate immunity, is poorly understood. Moreover, inconsistent literature on HBV and host innate immunity has led to controversies. However, recently, there has been an increase in the number of studies that have highlighted the link between innate immune responses, including Toll-like receptors (TLRs), and chronic HBV infection. TLRs are the key sensing molecules that detect pathogen-associated molecular patterns and regulate the induction of pro- and anti-inflammatory cytokines, thereby shaping the adaptive immunity. The suppression of TLR response has been reported in patients with chronic hepatitis B (CHB), as well as in other models, including tree shrews, suggesting an association of TLR response in HBV chronicity. Additionally, TLR agonists have been reported to improve the host innate immune response against HBV infection, highlighting the potential of these agonists as immunomodulators for enhancing CHB treatment. In this study, we discuss the current understanding of host innate immune responses during HBV infection, particularly focusing on the TLR response and TLR agonists as immunomodulators.

Animal and Organoid Models of Liver Fibrosis

Liver fibrosis refers to the process underlying the development of chronic liver diseases, wherein liver cells are repeatedly destroyed and regenerated, which leads to an excessive deposition and abnormal distribution of the extracellular matrix such as collagen, glycoprotein and proteoglycan in the liver. Liver fibrosis thus constitutes the pathological repair response of the liver to chronic injury. Hepatic fibrosis is a key step in the progression of chronic liver disease to cirrhosis and an important factor affecting the prognosis of chronic liver disease. Further development of liver fibrosis may lead to structural disorders of the liver, nodular regeneration of hepatocytes and the formation of cirrhosis. Hepatic fibrosis is histologically reversible if treated aggressively during this period, but when fibrosis progresses to the stage of cirrhosis, reversal is very difficult, resulting in a poor prognosis. There are many causes of liver fibrosis, including liver injury caused by drugs, viral hepatitis, alcoholic liver, fatty liver and autoimmune disease. The mechanism underlying hepatic fibrosis differs among etiologies. The establishment of an appropriate animal model of liver fibrosis is not only an important basis for the in-depth study of the pathogenesis of liver fibrosis but also an important means for clinical experts to select drugs for the prevention and treatment of liver fibrosis. The present study focused on the modeling methods and fibrosis characteristics of different animal models of liver fibrosis, such as a chemical-induced liver fibrosis model, autoimmune liver fibrosis model, cholestatic liver fibrosis model, alcoholic liver fibrosis model and non-alcoholic liver fibrosis model. In addition, we also summarize the research and application prospects concerning new organoids in liver fibrosis models proposed in recent years. A suitable animal model of liver fibrosis and organoid fibrosis model that closely resemble the physiological state of the human body will provide bases for the in-depth study of the pathogenesis of liver fibrosis and the development of therapeutic drugs.

Unimpaired immunogenicity of yeast-expressed hepatitis B surface antigen stored at elevated temperatures

Global adoption of hepatitis B virus (HBV) vaccines has greatly reduced new HBV infections. Current HBV vaccines are liquid suspensions containing recombinant hepatitis B surface antigen (HBsAg) particles mixed with aluminum phosphate or aluminum hydroxide. Refrigeration (2-8°C) as recommended for vaccine transport and storage may be unachievable in certain HBV-prevalent developing countries or regions. In this study, we stored yeast-expressed HBsAg and aluminum hydroxide separately at the standard (4°C) and elevated temperature (25, 37, or 45°C) for 14, 23, and 30 days, then mixed them and used the mixture to vaccinate mice with a prime-boost program. The antisera from all the vaccinated mice successfully inhibited HBV infection of HepG2 cells stably expressing HBV receptor sodium taurocholate cotransporting polypeptide. Furthermore, no serum HBsAg was detected in vaccinated mice on Day 1 post-hydrodynamic injection (HDI) of an HBV replicon plasmid and onwards, accompanied with an increasing anti-HBsAg antibody (HBsAb) level. In contrast, serum HBsAg in phosphate-buffered saline (PBS)-injected mice peaked on Day 4 post-HDI and was cleared on Day 14 post-HDI, which coincided with appearance of HBsAb on Day 7 post-HDI, suggesting a typical HBV acute infection process. HBV DNA peaked on Day 4 post-HDI in vaccinated mice, its level significantly lower than that in PBS-injected mice on Day 7 post-HDI, and showed a higher clearance rate. Taken together, we conclude that storing recombinant HBsAg at 25, 37, or 45°C for 14-30 days does not impair its immunogenicity in mice.

Transcriptome Analysis and Comparison of Marmota monax and Marmota himalayana

The Eastern woodchuck (Marmota monax) is a classical animal model for studying hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC) in humans. Recently, we found that Marmota himalayana, an Asian animal species closely related to Marmota monax, is susceptible to woodchuck hepatitis virus (WHV) infection and can be used as a new mammalian model for HBV infection. However, the lack of genomic sequence information of both Marmota models strongly limited their application breadth and depth. To address this major obstacle of the Marmota models, we utilized Illumina RNA-Seq technology to sequence the cDNA libraries of liver and spleen samples of two Marmota monax and four Marmota himalayana. In total, over 13 billion nucleotide bases were sequenced and approximately 1.5 billion clean reads were obtained. Following assembly, 106,496 consensus sequences of Marmota monax and 78,483 consensus sequences of Marmota himalayana were detected. For functional annotation, in total 73,603 Unigenes of Marmota monax and 78,483 Unigenes of Marmota himalayana were identified using different databases (NR, NT, Swiss-Prot, KEGG, COG, GO). The Unigenes were aligned by blastx to protein databases to decide the coding DNA sequences (CDS) and in total 41,247 CDS of Marmota monax and 34,033 CDS of Marmota himalayana were predicted. The single nucleotide polymorphisms (SNPs) and the simple sequence repeats (SSRs) were also analyzed for all Unigenes obtained. Moreover, a large-scale transcriptome comparison was performed and revealed a high similarity in transcriptome sequences between the two marmota species. Our study provides an extensive amount of novel sequence information for Marmota monax and Marmota himalayana. This information may serve as a valuable genomics resource for further molecular, developmental and comparative evolutionary studies, as well as for the identification and characterization of functional genes that are involved in WHV infection and HCC development in the woodchuck model.

The hepatitis B virus ribonuclease H as a drug target

Chronic hepatitis B virus (HBV) infection is a leading cause of hepatitis, liver failure, and hepatocellular carcinoma. An outstanding vaccine is available; however, the number of infections remains high. Current anti-HBV treatments with interferon α and nucleos(t)ide analogs clear the infection in only a small minority of patients, and either induce serious side-effects or are of very long duration. HBV is a small, enveloped DNA virus that replicates by reverse transcription via an RNA intermediate. The HBV ribonuclease H (RNaseH) is essential for viral replication, but it has not been exploited as a drug target. Recent low-throughput screening of compound classes with anti-Human Immunodeficiency Virus RNaseH activity led to identification of HBV RNaseH inhibitors in three different chemical families that block HBV replication. These inhibitors are promising candidates for development into new anti-HBV drugs. The RNaseH inhibitors may help improve treatment efficacy enough to clear the virus from the liver when used in combination with existing anti-HBV drugs and/or with other novel inhibitors under development. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B."

Anti-HBV activity of the different extracts from Phyllanthus rheedei Wight in cell culture based assay systems

ETHNOPHARMACOLOGICAL RELEVANCE

Phyllanthusrheedei Wight is a plant used by Muthuvan tribes of Kerala for treating liver related diseases.

MATERIALS AND METHODS

The different extracts of Phyllanthus rheedei were analysed on cell lines were viz, PLC/PRF, Hep3B, FLCII10 and HepG2215 for its anti-HBV property. The analysis was done through ELISA, SQRT-PCR and immuno blotting. The most active extract was then divided in to fractions using HPTLC and the most active fraction was further identified.

RESULTS

From the screening experiments it was shown that the ethanol extract of this plant has the maximum activity in lowering the viral markers like HBsAg, HBV Core and HBV X protein and whole virions with comparatively lesser cytotoxicity. The dose responses of this particular extract were further established.

CONCLUSIONS

This study concluded that the ethanol extract of Phyllanthusrheedei is very much effective in preventing the multiplication of HBV at the cellular level. This study scientifically validated the tribal claim of the use of this plant for severe liver disorders.

Targeted delivery of siRNA against hepatitis B virus by preS1 peptide molecular ligand

AIM

For chronic hepatitis B virus (HBV) infection, the effects of current therapies are limited. RNA interference of virus-specific genes has emerged as a potential antiviral mechanism. However, a suitable delivery vector is still to be developed. We studied a novel vector transferring siRNA targeting hepatic cells in vivo and in vitro in order to find a new way to cure HBV-related live diseases.

METHODS

The preS1-9Arg ligand was used to deliver siRNA to HepG2 and to HepG2 2.2.15 cells. To validate the antiviral efficacy in vivo, a HBV viremic animal model was established by s.c. inoculation of HepG2 2.2.15 tumor cells in nude mice. The minimal retardation effect on the migration of siRNA was detected by gel electrophoresis to confirm the combination and the optimal ratio. Hepatitis B surface antigen (HBsAg) levels were detected by semiquantitatively enzyme-linked immunosorbent assay RNA levels were quantified with quantitative real-time polymerase chain reaction and protein levels were determined with immunoblots and immunohistochemistry.

RESULTS

PreS1-9Arg peptide strongly combined and transferred siRNA into HepG2 cells. PreS1-9Arg-siRNA molecular conjugate effectively reduced the production of HBsAg and HBV DNA without liver toxicity in vitro and in vivo.

CONCLUSION

The results indicated that preS1-9Arg may be a potential novel vector to deliver siRNA targeting liver cells.

Mouse models of hepatitis B virus infection comprising host-virus immunologic interactions

Hepatitis B virus (HBV) infection is one of the most prevalent infectious diseases associated with various human liver diseases, including acute, fulminant and chronic hepatitis; liver cirrhosis; and hepatocellular carcinoma. Despite the availability of an HBV vaccine and the development of antiviral therapies, there are still more than 350 million chronically infected people worldwide, approximately 5% of the world population. To understand the virus biology and pathogenesis in HBV-infected patients, several animal models have been developed to mimic hepatic HBV infection and the immune response against HBV, but the narrow host range of HBV infection and lack of a full immune response spectrum in animal models remain significant limitations. Accumulating evidence obtained from studies using a variety of mouse models that recapitulate hepatic HBV infection provides several clues for understanding host-virus immunologic interactions during HBV infection, whereas the determinants of the immune response required for HBV clearance are poorly defined. Therefore, adequate mouse models are urgently needed to elucidate the mechanism of HBV elimination and identify novel targets for antiviral therapies.

Virus associated malignancies: the role of viral hepatitis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading fatal cancer worldwide and its incidence continues to increase. Chronic viral hepatitis involving either hepatitis B virus (HBV) or hepatitis C virus (HCV) infection is the leading etiology for HCC, making HCC prevention a major goal of antiviral therapy. While recent clinical observations and translational research have enhanced our understanding of the molecular mechanisms driving the initiation and progression of HCC, much remains unknown. Current data indicates that HCC tumors are highly complex and heterogeneous resulting from the aberrant function of multiple molecular pathways. This complex biology is responsible, at least in part, for the absence of highly efficient target-directed therapies for this deadly cancer. Additionally, the direct or indirect effect of HBV and HCV infection on the development of HCC is still a contentious issue. Thus, the question remains whether viral hepatitis-associated HCC stems from virus-specific factors, and/or from a general mechanism involving inflammation and tissue regeneration. In this review we summarize general mechanisms implicated in HCC, emphasizing data generated by new technologies available today. We also highlight specific pathways by which HBV and HCV could be involved in HCC pathogenesis. However, improvements to current in vitro and in vivo systems for both viruses will be needed to rigorously define the temporal sequence and specific pathway dysregulations that drive the strong clinical link between chronic hepatitis virus infection and HCC.

Development and application of a universal Taqman real-time PCR for quantitation of duck hepatitis B virus DNA

To develop a quantitative assay for universal detection of duck hepatitis B virus (DHBV) DNA, a Taqman real-time fluorescent quantitative polymerase chain reaction (FQ-PCR) assay was developed using primers and probes based on genomic sequences located at nucleotide 241-414 of the DHBV Core region which possesses the highest homology among the 44 DHBV genomes available in Genbank. The DHBV Core gene cloned in pGEM-T was used to generate DHBV DNA standard. The assay had a lowest detection limit of 10(3) copies/ml and a good linear standard curve (Y=-3.989X+49.086, r(2)=0.9993) over a wide range of input DHBV DNA (10(3) to 10(10) copies/ml). The standard deviation of intra- and inter-assay was 0.01-0.06 and 0.05-0.16, respectively, and the coefficient of variation was 1.3-1.8%. The specificity of the assay was validated using duck hepatitis virus type 1, hepatitis B virus, and E. coli DNA. Comparison of ABI 7300 and Bio-Rad iQ5 PCR instruments yielded highly consistent results. The assay showed a positive rate of 63.8% (51/80) DHBV DNA in peripheral blood and liver tissue from ducks from Xi'an, China. The FQ-PCR developed is highly sensitive, specific, reproducible and versatile, and may be used to universally detect DHBV DNA of different DHBV strains.

Interferon-lambda3 (IFN-λ3) and its cognate receptor subunits in tree shrews (Tupaia belangeri): genomic sequence retrieval, molecular identification and expression analysis

Type III IFNs (IFN-λs) constitute a new subfamily with antiviral activities by signaling through a unique receptor complex composed of IFN-λs receptor 1 (IFNλR1) and interleukin-10 receptor 2 (IL10R2). As tree shrews (Tupaia belangeri) have shown susceptiblility to several human viruses, they are a potentially important model for analyzing viral infection. However, little is known about their IFN-λs system. We used the tree shrew genome to retrieve IFN-λs and their receptor contig sequences by BLASTN and BLASTZ algorithms, and GenScan was used to scan transcripts from the putative contig sequences. RT-PCR and bioinformatic methods were then used to clone and characterize the IFN-λs system. Due to its highest identity with human IFN-λ3, we opted to define one intact IFN-λ gene, tsIFN-λ3, as well as its two receptor subunits, tsIFNλR1 and tsIL10R2. Additionally, our results showed that tsIFN-λ3 contained many features conserved in IFN-λ3 genes from other mammals, including conserved signal peptide cleavage and glycosylation sites, and several residues responsible for binding to the type III IFNR. We also found six transcript variants in the receptors: three in tsIFNλR1, wherein different extracellular regions exist in three transmembrane proteins, resulting in different affinities with IFN-λs; and three more variants in tsIL10R2, encoding one transmembrane and two soluble proteins. Based on tissue distribution in the liver, heart, brain, lung, intestine, kidney, spleen, and stomach, we found that IFN-λs receptor complex was expressed in a variety of organs although the expression level differed markedly between them. As the first study to find transcript variants in IL-10R2, our study offers novel insights that may have important implications for the role of IFN-λs in tree shrews’ susceptibility with a variety of human viruses, bolstering the arguments for using tree shrews as an animal model in the study of human viral infections.

Animal models of chronic liver diseases

Chronic liver diseases are frequent and potentially life threatening for humans. The underlying etiologies are diverse, ranging from viral infections, autoimmune disorders, and intoxications (including alcohol abuse) to imbalanced diets. Although at early stages of disease the liver regenerates in the absence of the insult, advanced stages cannot be healed and may require organ transplantation. A better understanding of underlying mechanisms is mandatory for the design of new drugs to be used in clinic. Therefore, rodent models are being developed to mimic human liver disease. However, no model to date can completely recapitulate the "corresponding" human disorder. Limiting factors are the time frame required in humans to establish a certain liver disease and the fact that rodents possess a distinct immune system compared with humans and have different metabolic rates affecting liver homeostasis. These features account for the difficulties in developing adequate rodent models for studying disease progression and for testing new pharmaceuticals to be translated into the clinic. Nevertheless, traditional and new promising animal models that mimic certain attributes of chronic liver diseases are established and being used to deepen our understanding in the underlying mechanisms of distinct liver diseases. This review aims at providing a comprehensive overview of recent advances in animal models recapitulating different features and etiologies of human liver diseases.

The HepaRG cell line: a valuable in vitro tool for hepatitis virus infection studies

Hepatitis virus infections, mainly hepatitis B virus (HBV) and hepatitis C virus (HCV) infections, constitute a major problem for public health since they have a worldwide distribution and because they are associated with hepatocellular carcinoma and death. Current anti-HBV vaccines seem to be effective in the majority of people. However, an important issue waiting to be tackled nowadays is how to cure patients with chronic hepatitis B. Moreover, no vaccine is available today for the prevention of HCV infection. Therefore, the use of adequate in vitro infection systems is a prerequisite for the molecular understanding of the infection events of these viruses, which could result in the development of novel powerful therapeutics. In this respect, the HepaRG cell line exhibits a hepatocyte-like morphology and displays drug metabolism capacity similar to that of primary hepatocytes. HepaRG cells have yet been proven to be a useful tool in the study of viral infections, particularly for deciphering the mechanism of HBV entry into hepatocytes.

An ex vivo perfusion system emulating in vivo conditions in noncirrhotic and cirrhotic human liver

Various models are used for investigating human liver diseases and testing new drugs. However, data generated in such models have only limited relevance for in vivo conditions in humans. We present here an ex vivo perfusion system using human liver samples that enables the characterization of parameters in a functionally intact tissue context. Resected samples of noncirrhotic liver (NC; n = 10) and cirrhotic liver (CL; n = 12) were perfused for 6-h periods. General and liver-specific parameters (glucose, lactate, oxygen, albumin, urea, and bile acids), liver enzymes (aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, glutamate dehydrogenase, and γ-glutamyl transferase), overall (M65) and apoptotic (M30) cell-death markers, and indicators of phase-I/phase-II biotransformations were analyzed. The measurement readings closely resembled (patho)physiological characteristics in patients with NC and CL. Mean courses of glucose levels reflected the CLs' reduced glycogen storage capability. Furthermore, CL samples exhibited significantly stronger increases in lactate, bile acids, and the M30/M65 ratio than NC specimens. Likewise, NC samples exhibited more rapid phase-I transformations of phenacetin, midazolam, and diclofenac and phase-I to phase-II turnover rates of the respective intermediates than CL tissue. Collectively, these findings reveal the better hepatic functionality in NC. Perfusion of human liver tissue with this system emulates in vivo conditions and clearly discriminates between noncirrhotic and cirrhotic tissue. This highly reliable device for investigating basic hepatic functionality and testing safety/toxicity, pharmacokinetics/pharmacodynamics and efficacies of novel therapeutic modalities promises to generate superior data compared with those obtained via existing economic perfusion systems.

Hepatitis B precore protein: pathogenic potential and therapeutic promise

Hepatitis B virus (HBV), a small and economically packaged double-stranded DNA virus, represents an enormous global health care burden. In spite of an effective vaccine, HBV is endemic in many countries. Chronic hepatitis B (CHB) results in the development of significant clinical outcomes such as liver disease and hepatocellular carcinoma (HCC), which are associated with high mortality rates. HBV is a non-cytopathic virus, with the host's immune response responsible for the associated liver damage. Indeed, HBV appears to be a master of manipulating and modulating the immune response to achieve persistent and chronic infection. The HBV precore protein or hepatitis B e antigen (HBeAg) is a key viral protein involved in these processes, for instance though the down-regulation of the innate immune response. The development of new therapies that target viral proteins, such as HBeAg, which regulates of the immune system, may offer a new wave of potential therapeutics to circumvent progression to CHB and liver disease.

Experimental models and therapeutic approaches for HBV

Liver disease associated to persistent infection with the hepatitis B virus (HBV) continues to be a major health problem of global impact. In spite of the existence of an effective vaccine, approximately 360 million people are chronically infected worldwide, who are at high risk of developing liver cirrhosis and hepatocellular carcinoma. Although current therapeutic regimens can efficiently suppress viral replication, the unique replication strategies employed by HBV permit the virus to persist within the infected hepatocytes. As a consequence, relapse of viral activity is commonly observed after cessation of treatment with polymerase inhibitors. The narrow host range of HBV has hindered progresses in understanding specific steps of HBV replication and the development of more effective therapeutic strategies aiming at achieving sustained viral control and, eventually, virus eradication. This review will focus on summarizing recent advances obtained with well-established and more innovative experimental models, giving emphasis on the strength of the different systems as tools for elucidating distinct aspects of HBV persistence and for the development of new therapeutic approaches.

Animal model for study of human hepatitis viruses

Human hepatitis B virus (HBV) and hepatitis C virus (HCV) infect only chimpanzees and humans. Analysis of both viruses has long been hampered by the absence of a small animal model. The recent development of human hepatocyte chimeric mice has enabled us to carry out studies on viral replication and cellular changes induced by replication of human hepatitis viruses. Various therapeutic agents have also been tested using this model. In the present review, we summarize published studies using chimeric mice and discuss the merits and shortcomings of this model.

Hepatitis B virus replication in primary macaque hepatocytes: crossing the species barrier toward a new small primate model

The development of new anti-hepatitis B virus (HBV) therapies, especially immunotherapeutic approaches, has been limited by the lack of a primate model more accessible than chimpanzees. We have previously demonstrated that sylvanus and cynomolgus macaques are susceptible to in vivo HBV infection after intrahepatic HBV DNA inoculation. In this study, we evaluated the susceptibility of primary macaque hepatocytes (PMHs) to HBV infection with a highly efficient HBV genome-mediated transfer system via a recombinant baculovirus (Bac-HBV). Freshly prepared PMHs, isolated from macaque liver tissue by collagenase perfusion, were transduced with Bac-HBV, and intermediates of replication were followed for 9 days post-transduction. Evidence of HBV replication (hepatitis B surface antigen secretion, viral DNA, RNA, and covalently closed circular DNA) was detected from day 1 to day 9 post-transduction. HBV markers were dose-dependent and still detectable at a multiplicity of infection of 10. Importantly, transduced PMHs secreted all typical forms of HBV particles, as evidenced by a cesium chloride gradient as well as transmission electron microscopy. Furthermore, the Toll-like receptor 9 (TLR9) ligand was used to stimulate freshly prepared macaque peripheral blood mononuclear cells to generate TLR9-induced cytokines. We then demonstrated the antiviral effects of both TLR9-induced cytokines and nucleoside analogue (lamivudine) on HBV replication in transduced PMHs.

CONCLUSION

Baculovirus-mediated genome transfer initiated a full HBV replication cycle in PMHs; thus highlighted both the baculovirus efficiency in crossing the species barrier and macaque susceptibility to HBV infection. Moreover, our results demonstrate the relevance of thus system for antiviral compound evaluations with either nucleoside analogues or inhibitory cytokines. Cynomolgus macaques are readily available, are immunologically closely related to humans, and may therefore represent a promising model for the development of new immunotherapeutic strategies.

Application of hepatitis B virus replication mouse model

AIM: To evaluate the value of the hepatitis B virus (HBV) replication mouse model with regard to several aspects of the study of HBV biology.

METHODS: To evaluate the HBV replication mouse model in detecting the efficacy of anti-HBV agents, the interferon inducer polyinosinic-polytidylin acid (polyIC) and nucleotide analogues adefovir and entecavir were administered to mice injected with wild type pHBV4.1, and the inhibiting effect of these agents on HBV DNA replication was evaluated. To identify the model’s value in a replication ability study of HBV drug-resistant mutants and a HBx-minus mutant, telbivudine resistance mutants (rtM204I, ayw subtype), adefovir resistance mutants (rtA181V + rtN236T, ayw subtype) and HBx-minus mutants were injected respectively, and their corresponding HBV DNA replication intermediates in mouse liver were assessed.

RESULTS: Compared with the wild type HBV replication mouse model without antiviral agent treatment, the HBV DNA replication intermediates of the polyIC-treated group were decreased 1-fold; while in the entecavir- and adefovir-treated groups, the levels of HBV DNA replication intermediates were inhibited 13.6-fold and 1.4-fold, respectively. For the mouse models injected with telbivudine resistance mutant, adefovir resistance mutant and HBx-minus mutant, HBV DNA replication intermediates could still be detected, but the levels of HBV DNA replication intermediates of these mutants decreased 4.5-fold, 5.6-fold and 2.9-fold respectively, compared with the mouse model with wild type HBV plasmid.

CONCLUSION: The HBV replication mouse model we established was a useful and convenient tool to detect the efficacy of antiviral agents and to study the replication ability of HBV mutants in vivo.

Immunization of guinea pigs with novel hepatitis B antigen as nanoparticle aggregate powders administered by the pulmonary route

Novel nanoparticle-aggregate formulations containing recombinant hepatitis B surface antigen (rHBsAg) were administered to the lungs of guinea pigs and antibodies generated to this antigen evaluated. Preparations of dry powders of: (a) rHBsAg encapsulated within poly(lactic-co-glycolic acid) (PLGA)/polyethylene glycol (PEG) nanoparticles (antigen nanoparticles, AgN(SD)), (b) rHBsAg in a physical mixture with blank PLGA/PEG nanoparticles (antigen nanoparticle admixture (AgNA(SD)), and (c) rHBsAg encapsulated in PLGA/PEG nanoparticles plus free rHBsAg (antigen nanoparticles and free antigen), were generated by spray drying with leucine. Control groups consisted of alum with adsorbed rHBsAg (AlumAg); reconstituted suspensions of spray-dried rHBsAg-loaded PLGA/PEG nanoparticles with leucine; and rHBsAg-loaded PLGA/PEG nanoparticles (AgN). Control preparations were administered by intramuscular injection; AgN was also spray instilled into the lungs. The IgG titers were measured in the serum for 24 weeks after the initial immunization; IgA titers were measured in the bronchio-alveolar lavage fluid. While the highest titer of serum IgG antibody was observed in guinea pigs immunized with AlumAg administered by the IM route, animals immunized with powder formulations via the pulmonary route exhibited high IgA titers. In addition, guinea pigs immunized with AgNA(SD) via the pulmonary route exhibited IgG titers above 1,000 mIU/ml in the serum (IgG titers above 10 mIU/ml is considered protective). Thus, the disadvantages observed with the existing hepatitis B vaccine administered by the parenteral route may be overcome by administering them as novel dry powders to the lungs. In addition, these powders have the advantage of eliciting a high mucosal immune response in the lungs without traditional adjuvants.

Establishment of a novel cell model of hepatitis B virus infection

AIM: To establish a hybrid cell line (by fusing HepG2 cells with primary human hepatocytes) that can be infected by hepatitis B virus (HBV) and be serially subcultured in vitro, and to evaluate the infection ability of HBV in this hybrid cell line.

METHODS: Normal human hepatocytes were isolated and cultured. Primary human hepatocytes were then fused with HGPRT-deficient HepG2 cells (induced with ethyl methanesulfonate). The hybrid cells were identified by the trypsin G-banding method. After the hybrid cells and normal HepG2 cells were infected with serum-derived HBV virions, intracellular and secreted HBV DNA as well as intracellular HBV cccDNA (covalent closed circle DNA) were detected by nested polymerase chain reaction (PCR). HBcAg in infected cells was analyzed by indirect immunofluorescence. HBsAg and HBeAg in the supernatants of infected cells were identified by electrochemiluminescence.

RESULTS: A hybrid cell line was established successfully by fusing HepG2 cells with primary human hepatocytes. This hybrid cell line could be subcultured in vitro. Karyotype analysis showed that the modal chromosome number of hybrid cells was 99. HBV DNA was detected consistently in both hybrid cells and their culture medium 4 days post-infection. HBV cccDNA was detected consistently 3 days post-infection. HBcAg, HBsAg and HBeAg were also detected consistently 4 days post-infection. In contrast, negative results were obtained in control HepG2 cells infected with HBV virions.

CONCLUSION: A new hybrid cell line that can be used for establishing an in vitro cell model of HBV infection is established successfully. This new hybrid cell line inherits the characteristics of both HepG2 cells and primary human hepatocytes.

Prevalence of a virus similar to human hepatitis B virus in swine

Background

The objective of this study is to established evidence of the existence of a novel member of the hepadnavirus family endemic in swine. Temporarily this virus was designated as swine hepatitis B virus (SHBV). This SHBV can be detected by using human hepatitis B virus diagnostic kits including ELISA, immunohistochemical staining, and transmission electron microscopy (TEM). Also seroprevalence of pig farms in Beijing, China, and pathological features of SHBV infection was determined.

Results

Screened result shows that overall prevalence of HBsAg was 24.8%, closed to that of anti-HBsAg, whereas HBeAg and anti-HBe were barely detectable. The distribution of HBsAg and HBcAg was examined by immunohistochemistry of liver samples. Typical hepatitis pathological change, such as spotty parenchymal cell degeneration, necrosis of hepatocytes and proliferation of fibrous connective tissue were observed during histopathological analysis. Analysis of HBsAg-positive serum with TEM revealed two morphologic forms, 20 nm and 40 nm sized particles, similar to small spherical and Danes particles of HBV. Observation of the ultrastructure of the liver also found HBV-like particles in the nucleus of hepatocytes.

Conclusion

Our research result implies that SHBV could be a causative agent of swine. The discovery of SHBV will unveil novel evolutionary aspects of hepatitis and provides new information for further hepadnavirus research.

Cell therapy for the diseased liver: from stem cell biology to novel models for hepatotropic human pathogens

It has long been known that hepatocytes possess the potential to replicate through many cell generations because regeneration can be achieved in rodents after serial two-thirds hepatectomy. It has taken considerable time and effort to harness this potential, with liver regeneration models involving hepatocyte transplantation developing over the past 15 years. This review will describe the experiments that have established the models and methodology for liver repopulation, and the use of cells other than adult hepatocytes in liver repopulation, including hepatic cell lines and hematopoietic, cord blood, hepatic and embryonic stem cells. Emphasis will be placed on the characteristics of the models and how they can influence the outcome of the experiments. Finally, an account of the development of murine models that are competent to accept human hepatocytes is provided. In these models, liver deficiencies are induced in immunodeficient mice, where healthy human cells have a selective advantage. These mice with humanized livers provide a powerful new experimental tool for the study of human hepatotropic pathogens.

Mouse models in liver cancer research: A review of current literature

Primary liver cancer remains one of the most lethal malignancies worldwide. Due to differences in prevalence of etiological factors the incidence of primary liver cancer varies among the world, with a peak in East-Asia. As this disease is still lethal in most of the cases, research has to be done to improve our understanding of the disease, offering insights for possible treatment options. For this purpose, animal models are widely used, especially mouse models. In this review, we describe the different types of mouse models used in liver cancer research, with emphasis on genetically engineered mice used in this field. We focus on hepatocellular carcinoma (HCC), as this is by far the most common type of primary liver cancer, accounting for 70%-85% of cases.

Nuclear factor kappa B and hepatitis viruses

BACKGROUND

Hepatitis can be caused by a number of viruses, which have similar clinical manifestations and render infected individuals at high risk of death from cirrhosis and liver cancer. Current therapies for hepatitis have limited effects and unsatisfactory patient outcomes. Nuclear factor kappa B (NF-kappaB) is critical for immune and inflammatory responses. During its lifetime the cell demands specific and highly regulated control of NF-kappaB activity.

OBJECTIVE

To develop novel strategies to overcome various hepatitides and related liver cancer with NF-kappaB as the key point.

METHODS

All aspects of NF-kappaB control with regard to hepatitis are covered.

RESULTS/CONCLUSION

NF-kappaB plays an important role in the process of hepatitis and is hypothesized to be an anti-cancer factor in the subsequent inflammation-associated hepatocarcinogenesis.

The Anti-hepatitis B Virus Activity of Boehmeria nivea Extract in HBV-viremia SCID Mice

Boehmeria nivea extract (BNE) is widely used in southern Taiwan as a folk medicine for hepato-protection and hepatitis treatment. In previous studies, we demonstrated that BNE could reduce the supernatant hepatitis B virus (HBV) DNA in HBV-producing HepG2 2.2.15 cells. In the present study, we established an animal model of HBV viremia and used it to validate the efficacy of BNE in vivo. In this animal model, serum HBV DNA and HBsAg were elevated in accordance with tumor growth. To evaluate the anti-HBV activity of BNE, HBV-viremia mice were built up after one subcutaneous inoculation of HepG2 2.2.15 tumor cells in severe combined immunodeficiency mice over 13 days. The levels of serum HBV DNA were elevated around 10(5)-10(6) copies per milliliter. Both oral and intraperitoneal administration of BNE were effective at inhibiting the production of HBsAg and HBV DNA, whereas tumor growth was not affected by all test articles. Intraperitoneal administration of BNE appeared to have greater potential to inhibit serum HBV DNA levels compared with oral administration under the same dosage. Notably, reduced natural killer cell activity was also observed after high dosage of BNE administration, and this correlated with reduced serum HBV DNA. In conclusion, BNE exhibited potential anti-HBV activity in an animal model of HBV viremia.

Pathogenesis of hepatitis B virus infection

Infection with hepatitis B virus (HBV) leads to a wide spectrum of clinical presentations ranging from an asymptomatic carrier state to self-limited acute or fulminant hepatitis to chronic hepatitis with progression to cirrhosis and hepatocellular carcinoma. Infection with HBV is one of the most common viral diseases affecting man. Both viral factors as well as the host immune response have been implicated in the pathogenesis and clinical outcome of HBV infection. In this review, we will discuss the impact of virus-host interactions for the pathogenesis of HBV infection and liver disease. These interactions include the relevance of naturally occurring viral variants for clinical disease, the role of virus-induced apoptosis for HBV-induced liver cell injury and the impact of antiviral immune responses for outcome of infection.