Mechanism of Hepatitis B Virus Persistence in Hepatocytes and Its Carcinogenic Potential

Hepatitis B Virus Infection: A Mini Review

Hepatitis B and C viruses (HBV and HCV) are the leading causes of end-stage liver disease worldwide. Although there is a potent vaccine against HBV, many new infections are recorded annually, especially in poorly resourced places which have lax vaccination policies. Again, as HBV has no cure and chronic infection is lifelong, vaccines cannot help those already infected. Studies to thoroughly understand the HBV biology and pathogenesis are limited, leaving much yet to be understood about the genomic features and their role in establishing and maintaining infection. The current knowledge of the impact on disease progression and response to treatment, especially in hyperendemic regions, is inadequate. This calls for in-depth studies on viral biology, mainly for the purposes of coming up with better management strategies for infected people and more effective preventative measures for others. This information could also point us in the direction of a cure. Here, we discuss the progress made in understanding the genomic basis of viral activities leading to the complex interplay of the virus and the host, which determines the outcome of HBV infection as well as the impact of coinfections.

Harnessing CRISPR technology for viral therapeutics and vaccines: from preclinical studies to clinical applications

The CRISPR/Cas system, identified as a type of bacterial adaptive immune system, have attracted significant attention due to its remarkable ability to precisely detect and eliminate foreign genetic material and nucleic acids. Expanding upon these inherent capabilities, recent investigations have unveiled the potential of reprogrammed CRISPR/Cas 9, 12, and 13 systems for treating viral infections associated with human diseases, specifically targeting DNA and RNA viruses, respectively. Of particular interest is the RNA virus responsible for the recent global outbreak of coronavirus disease 2019 (COVID-19), which presents a substantial public health risk, coupled with limited efficacy of current prophylactic and therapeutic techniques. In this regard, the utilization of CRISPR/Cas technology offers a promising gene editing approach to overcome the limitations of conventional methods in managing viral infections. This comprehensive review provides an overview of the latest CRISPR/Cas-based therapeutic and vaccine strategies employed to combat human viral infections. Additionally, we discuss significant challenges and offer insights into the future prospects of this cutting-edge gene editing technology.

Human Leukocyte Antigen Polymorphism HLA-A*24:02 is Associated with Acute Liver Disease in HBV-Infected Han Chinese Adults

BACKGROUND

Whether polymorphic Human Leukocyte Antigen (HLA)-A, HLA-B and HLA-DRB1 alleles were associated with acute liver disease after hepatitis B virus (HBV) infections was investigated.

METHODS

In this study, from initially 100 participants in each group, HLA-A, HLA-B and HLA-DRB1 sequences were available from 86 acute hepatitis B (AHB) patients and from 84 HBV-resistant individuals (controls), using sequencing-based typing allele groups and alleles that exhibited differences in distribution between the case and control groups were subjected to chi-squared and logistic regression analyses to identify those associated with AHB. A dose response analysis was also performed on the effect of HLA-A*24:02 allele number on acute liver disease following HBV infection.

RESULTS

The frequency distribution of HLA-B and HLA-DRB1 alleles in the control group were in Hardy-Weinberg Equilibrium (P > .05). HLA-A*24:02 (χ2 = 6.949, P = .008) occurred most frequently in the AHB and HLA-DRB1*12:02 (χ2 = 7.768, P = .005) in the control group. With adjustment for sex, the logistic regression model showed that the HLA-A*24:02 allele was significantly associated with AHB liver injury (P = .0326, OR = 2.270, 95% CI: 1.070-4.816), whereas the other HLA-A, HLA-B, and HLA-DRB1 alleles were not (P > .05). A linear response was observed for the association between HLA-A*24:02 allele number and acute liver disease after HBV infections (χ2 = 4.428, P = .025).

CONCLUSION

The HLA-A*24:02 allele may influence the severity of the cellular response to HBV infection, increasing the elimination of HBV-infected hepatocytes. The HLA-A*24:02 allele may be a potential screening marker for identifying people or regional populations in China at higher risk of acute liver disease following HBV infection.

Systemic lupus erythematosus is associated with lower risk of hepatitis B virus infection: A multivariable Mendelian randomization study in East Asian population

The relationship between systemic lupus erythematosus (SLE) and hepatitis B virus (HBV) infection is still unclear. We conducted a two-sample Mendelian randomization (MR) analysis using summary statistics from genome-wide association studies for SLE and HBV infection in individuals of East Asian ancestry. The inverse-variance weighted (IVW) method, weighted median (WM) method, and MR-Egger method were used to estimate the causal effect of SLE on HBV infection. Additionally, we performed a multivariable MR analysis adjusting for the effects of body mass index and rheumatoid arthritis. This MR study included a total of 225 106 individuals of East Asian ancestry, comprising 5616 cases and 219 490 controls. The IVW method (OR: 0.79, p = 3.34E-08) and the WM method (OR: 0.79, p = 9.09E-06) revealed a causal relationship between genetically predicted SLE and a low risk of HBV infection. The multivariable MR analysis still suggested a low risk of HBV infection associated with SLE (OR: 0.83, p = 2.89E-06). Our MR analysis supports a causal relationship between SLE and a low risk of HBV infection in individuals of East Asian ancestry.

Cell Culture Systems for Studying Hepatitis B and Hepatitis D Virus Infections

The hepatitis B virus (HBV) and hepatitis D virus (HDV) infections cause liver disease, including hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). HBV infection remains a major global health problem. In 2019, 296 million people were living with chronic hepatitis B and about 5% of them were co-infected with HDV. In vitro cell culture systems are instrumental in the development of therapeutic targets. Cell culture systems contribute to identifying molecular mechanisms for HBV and HDV propagation, finding drug targets for antiviral therapies, and testing antiviral agents. Current HBV therapeutics, such as nucleoside analogs, effectively suppress viral replication but are not curative. Additionally, no effective treatment for HDV infection is currently available. Therefore, there is an urgent need to develop therapies to treat both viral infections. A robust in vitro cell culture system supporting HBV and HDV infections (HBV/HDV) is a critical prerequisite to studying HBV/HDV pathogenesis, the complete life cycle of HBV/HDV infections, and consequently identifying new therapeutics. However, the lack of an efficient cell culture system hampers the development of novel antiviral strategies for HBV/HDV infections. In vitro cell culture models have evolved with significant improvements over several decades. Recently, the development of the HepG2-NTCP sec+ cell line, expressing the sodium taurocholate co-transporting polypeptide receptor (NTCP) and self-assembling co-cultured primary human hepatocytes (SACC-PHHs) has opened new perspectives for a better understanding of HBV and HDV lifecycles and the development of specific antiviral drug targets against HBV/HDV infections. We address various cell culture systems along with different cell lines and how these cell culture systems can be used to provide better tools for HBV and HDV studies.

Hepatitis B virus-induced hepatocellular carcinoma: a persistent global problem

Hepatitis B virus (HBV) infections are highly prevalent globally, representing a serious public health problem. The diverse modes of transmission and the burden of the chronic carrier population pose challenges to the effective management of HBV. Vaccination is the most effective preventive measure available in the current scenario. Still, HBV is one of the significant health issues in various parts of the globe due to non-response to vaccines, the high number of concealed carriers, and the lack of access and awareness. Universal vaccination programs must be scaled up in neonates, especially in the developing parts of the world, to prevent new HBV infections. Novel treatments like combinational therapy, gene silencing, and new antivirals must be available for effective management. The prolonged infection of HBV, direct and indirect, can promote the growth of hepatocellular carcinoma (HCC). The present review emphasizes the problems and probable solutions for better managing HBV infections, causal risk factors of HCC, and mechanisms of HCC.

Map of thrombogenesis in viral infections and viral-driven tumours

Viruses are pathogenic agents responsible for approximately 10% of all human cancers and significantly contribute to the global cancer burden. Until now, eight viruses have been associated with the development of a broad range of malignancies, including solid and haematological tumours. Besides triggering and promoting oncogenesis, viral infections often go hand-in-hand with haemostatic changes, representing a potential risk factor for venous thromboembolism (VTE). Conversely, VTE is a cardiovascular condition that is particularly common among oncological patients, with a detrimental impact on patient prognosis. Despite an association between viral infections and coagulopathies, it is unclear whether viral-driven tumours have a different incidence and prognosis pattern of thromboembolism compared to non-viral-induced tumours. Thus, this review aims to analyse the existing evidence concerning the association of viruses and viral tumours with the occurrence of VTE. Except for hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infection, which are associated with a high risk of VTE, little evidence exists concerning the thrombogenic potential associated with oncoviruses. As for tumours that can be induced by oncoviruses, four levels of VTE risk are observed, with hepatocellular carcinoma (HCC) and gastric carcinoma (GC) associated with the highest risk and nasopharyngeal carcinoma (NPC) associated with the lowest risk. Unfortunately, the incidence of cancer-related VTE according to tumour aetiology is unknown. Given the negative impact of VTE in oncological patients, research is required to better understand the mechanisms underlying blood hypercoagulability in viral-driven tumours to improve VTE management and prognosis assessment in patients diagnosed with these tumours.

Activation of distinct antiviral T-cell immunity: A comparison of bi- and trispecific T-cell engager antibodies with a chimeric antigen receptor targeting HBV envelope proteins

Despite the availability of an effective prophylactic vaccine, 820,000 people die annually of hepatitis B virus (HBV)-related liver disease according to WHO. Since current antiviral therapies do not provide a curative treatment for the 296 million HBV carriers around the globe, novel strategies to cure HBV are urgently needed. A promising approach is the redirection of T cells towards HBV-infected hepatocytes employing chimeric antigen receptors or T-cell engager antibodies. We recently described the effective redirection of T cells employing a second-generation chimeric antigen receptor directed against the envelope protein of hepatitis B virus on the surface of infected cells (S-CAR) as well as bispecific antibodies that engage CD3 or CD28 on T cells employing the identical HBV envelope protein (HBVenv) binder. In this study, we added a trispecific antibody comprising all three moieties to the tool-box. Cytotoxic and non-cytolytic antiviral activities of these bi- and trispecific T-cell engager antibodies were assessed in co-cultures of human PBMC with HBV-positive hepatoma cells, and compared to that of S-CAR-grafted T cells. Activation of T cells via the S-CAR or by either a combination of the CD3- and CD28-targeting bispecific antibodies or the trispecific antibody allowed for specific elimination of HBV-positive target cells. While S-CAR-grafted effector T cells displayed faster killing kinetics, combinatory treatment with the bispecific antibodies or single treatment with the trispecific antibody was associated with a more pronounced cytokine release. Clearance of viral antigens and elimination of the HBV persistence form, the covalently closed circular (ccc) DNA, through cytolytic as well as cytokine-mediated activity was observed in all three settings with the combination of bispecific antibodies showing the strongest non-cytolytic, cytokine-mediated antiviral effect. Taken together, we demonstrate that bi- and trispecific T-cell engager antibodies can serve as a potent, off-the-shelf alternative to S-CAR-grafted T cells to cure HBV.

Current treatment of chronic hepatitis B: Clinical aspects and future directions

Hepatitis B virus (HBV) infection is a public health threat worldwide, and there is no direct treatment yet available. In the event of infection, patients may present liver cirrhosis and cancer, which threaten the patients’ health globally, especially in the Asia-Pacific region and China. In 2019, Chinese hepatopathologists updated the 2015 Guidelines for the Prevention and Treatment of Chronic Hepatitis B as the clinical reference. The other versions formulated by the American Association for the Study of Liver Diseases (2018 AASLD guidelines) (AASLD, 2018), European Association for the Study of the Liver (2017 EASL guidelines) (EASL, 2017), and Asian-Pacific Association for the Study of the Liver (2015 APASL guidelines) (APASL, 2015) also provide clinical guidance. However, there are still some issues that need to be addressed. In the present study, the following aspects will be introduced successively: (1) Who should be treated in the general population according to the guidelines; (2) Treatment of specific populations infected with HBV; (3) Controversial issues in clinical practice; (4) Perspective.

In Vivo Bioluminescence Imaging of HBV Replicating Hepatocytes Allows for the Monitoring of Anti-Viral Immunity

Immunity against hepatitis B virus (HBV) infection is complex and not entirely understood so far, including the decisive factors leading to the development of chronic hepatitis B. This lack of a mechanistic understanding of HBV-specific immunity is also caused by a limited number of suitable animal models. Here, we describe the generation of a recombinant adenovirus expressing an HBV 1.3-overlength genome linked to luciferase (Ad-HBV-Luc) allowing for precise analysis of the quantity of infected hepatocytes. This enables sensitive and close-meshed monitoring of HBV-specific CD8 T cells and the onset of anti-viral immunity in mice. A high dose of Ad-HBV-Luc developed into chronic hepatitis B accompanied by dysfunctional CD8 T cells characterized by high expression of PD1 and TOX and low expression of KLRG1 and GzmB. In contrast, a low dose of Ad-HBV-Luc infection resulted in acute hepatitis with CD8 T cell-mediated elimination of HBV-replicating hepatocytes associated with elevated sALT levels and increased numbers of cytotoxic HBV-specific CD8 T cells. Thus, the infectious dose was a critical factor to induce either acute self-limited or chronic HBV infection in mice. Taken together, the new Ad-HBV-Luc vector will allow for highly sensitive and time-resolved analysis of HBV-specific immune responses during acute and chronic infection.

Controversies in Treating Chronic HBV: The Role of PEG-interferon-alfa

Pegylated interferon-alpha therapy is one of the first-line chronic hepatitis B treatment. Finite treatment duration, absence of drug resistance, delayed response, and higher hepatitis B surface antigen loss than nucleos(t)ides analog therapy are the advantages of pegylated interferon-alpha treatment. Common side effects and subcutaneous injections requirement limit its use. Identifying patients likely to respond to pegylated interferon-alpha and optimizing treatment is reasonable. Motivating patients to complete the 48-week treatment is necessary. Treatment is stopped or switched to other treatment strategies in patients with stopping rule criteria. Combination therapy with nucleos(t)ides analog may improve response, but remains controversial.

Emerging Hepatotropic Viruses in Cats: A Brief Review

The possible role of viruses in feline liver disease has long remained neglected. However, in 2018, an analogue of human hepatitis B virus was identified in cats. Moreover, antibodies for human hepatitis E have been detected consistently at various prevalence rates in cats. Although the correlation between these viruses and the liver injury in cats must be clarified, hepatotropic viruses might represent an increasing risk for feline and public health.

A short overview of CRISPR-Cas technology and its application in viral disease control

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) together with CRISPR-associated (Cas) proteins have catalysed a revolution in genetic engineering. Native CRISPR-Cas systems exist in many bacteria and archaea where they provide an adaptive immune response through sequence-specific degradation of an invading pathogen's genome. This system has been reconfigured for use in genome editing, drug development, gene expression regulation, diagnostics, the prevention and treatment of cancers, and the treatment of genetic and infectious diseases. In recent years, CRISPR-Cas systems have been used in the diagnosis and control of viral diseases, for example, CRISPR-Cas12/13 coupled with new amplification techniques to improve the specificity of sequence-specific fluorescent probe detection. Importantly, CRISPR applications are both sensitive and specific and usually only require commonly available lab equipment. Unlike the canonical Cas9 which is guided to double-stranded DNA sites of interest, Cas13 systems target RNA sequences and thus can be employed in strategies directed against RNA viruses or for transcriptional silencing. Many challenges remain for these approach, including issues with specificity and the requirement for better mammalian delivery systems. In this review, we summarize the applications of CRISPR-Cas systems in controlling mammalian viral infections. Following necessary improvements, it is expected that CRISPR-Cas systems will be used effectively for such applications in the future.

Comprehensive Analysis of CDCAs Methylation and Immune Infiltrates in Hepatocellular Carcinoma

Background

As essential components of cycle growth, the cell division cycle-associated family genes (CDCAs) have crucial roles in tumor development and progression, especially in hepatocellular carcinoma (HCC). However, due to the tumor heterogeneity of HCC, little is known about the methylation variability of CDCAs in mediating phenotypic changes (e.g., immune infiltrates) in HCC. Presently, we aim to comprehensively explore the expression and prognosis of CDCAs methylation with regard to immune infiltrates of HCC.

Methods

We first identified the correlating differentially expressed genes (co-DEGs) among 19 different types of cancer cohorts (a total of 7,783 patients) and then constructed the weighted gene co-expressed and co-methylated networks. Applying the clustering analysis, significant modules of DEGs including CDCAs were selected and their functional bioinformatics analyses were performed. Besides, using DiseaseMeth and TIMER, the correlation between the methylation levels of CDCAs and tumor immune infiltrates was also analyzed. In final, to assess the influence of CDCAs methylation on clinical prognosis, Kaplan-Meier and Cox regression analysis were carried out.

Result

A total of 473 co-DEGs are successfully identified, while seven genes of CDCAs (CDCA1–3 and CDCA5–8) have significant over-expression in HCC. Co-expressed and co-methylated networks reveal the strong positive correlations in mRNA expression and methylation levels of CDCAs. Besides, the biological enrichment analysis of CDCAs demonstrates that they are significantly related to the immune function regulation of infiltrating immune cells in HCC. Also, the methylation analysis of CDCAs depicts the strong association with the tumor immunogenicity, i.e., low-methylation of CDCA1, CDCA2, and CDCA8 dramatically reduced the immune infiltrate levels of T cells and cytotoxic lymphocytes. Additionally, CDCA1–6 and CDCA8 with low-methylation levels significantly deteriorate the overall survival of patients in HCC.

Conclusions

The co-expressed and co-methylated gene networks of CDCAs show a powerful association with immune function regulation. And the methylation levels of CDCAs suggesting the prognostic value and infiltrating immune differences could be a novel and predictive biomarker for the response of immunotherapy.

Deciphering Tumor Heterogeneity in Hepatocellular Carcinoma (HCC)-Multi-Omic and Singulomic Approaches

Tumor heterogeneity, a key hallmark of hepatocellular carcinomas (HCCs), poses a significant challenge to developing effective therapies or predicting clinical outcomes in HCC. Recent advances in next-generation sequencing-based multi-omic and single cell analysis technologies have enabled us to develop high-resolution atlases of tumors and pull back the curtain on tumor heterogeneity. By combining multiregion targeting sampling strategies with deep sequencing of the genome, transcriptome, epigenome, and proteome, several studies have revealed novel mechanistic insights into tumor initiation and progression in HCC. Advances in multiparametric immune cell profiling have facilitated a deeper dive into the biological complexity of HCC, which is crucial in this era of immunotherapy. Moreover, studies using liquid biopsy have demonstrated their potential to circumvent the need for tissue sampling to investigate heterogeneity. In this review, we discuss how multi-omic and single-cell sequencing technologies have advanced our understanding of tumor heterogeneity in HCC.

cccDNA Maintenance in Chronic Hepatitis B - Targeting the Matrix of Viral Replication

Chronic hepatitis B is a numerically important cause of cirrhosis and hepatocellular carcinoma, despite an effective prophylactic vaccine and well-tolerated and effective oral antivirals. Both the incapacity of the immune system to clear hepatitis B virus (HBV) infection and the unique replication strategies adopted by HBV are considered key determinants of HBV chronicity. In this regard, the formation of the HBV DNA minichromosome, the covalently closed circular DNA (cccDNA), in the nucleus of infected hepatocytes, is essential not only for the production of all viral proteins but also for HBV persistence even after long-term antiviral therapy. Licensed polymerase inhibitors target the HBV reverse transcriptase activity, control the disease with long-term therapy but fail to eliminate the cccDNA. Consequently, the production of viral RNAs and proteins, including the hepatitis B surface antigen (HBsAg), is not abolished. Novel therapeutic efforts that are in the pipeline for early clinical trials explore novel targets and molecules. Such therapeutic efforts focus on achieving a functional cure, which is defined by the loss of HBsAg and undetectable HBV DNA levels in serum. Since a true cure of HBV infection requires the elimination of the cccDNA from infected cells, comprehension of the mechanisms implicated in cccDNA biogenesis, regulation and stability appears necessary to achieve HBV eradication. In this review, we will summarize the state of knowledge on cccDNA metabolism, focusing on insights suggesting potential weak points of the cccDNA that may be key for the development of therapeutic approaches and design of clinical trials aiming at lowering cccDNA loads and activity.

The potential role of HLA-G in the pathogenesis of HBV infection: Immunosuppressive or immunoprotective?

The non-classical human leukocyte antigens (HLA)-G could be generally considered as a potent tolerogenic molecule, which modulates immune responses. HLA-G due to the immunosuppressive properties may play an important role in the pathogenesis of infections related to the liver. HLA-G may display two distinct activities in the pathological conditions so that it could be protective in the autoimmune and inflammatory diseases or could be suppressive of the immune system in the infections or cancers. HLA-G might be used as a novel therapeutic target for liver diseases in the future. Indeed, new therapeutic agents targeting HLA-G expression or antibodies which block HLA-G activity are being developed and tested. However, further consideration of the HLA-G function in liver disease is required. This review aims to summarize the role of HLA-G in the liver of patients with HBV infection.

Epigenetic modulation in chronic hepatitis B virus infection

The human hepatitis B virus (HBV) is a small-enveloped DNA virus causing acute and chronic hepatitis. Despite the existence of an effective prophylactic vaccine and the strong capacity of approved antiviral drugs to suppress viral replication, chronic HBV infection (CHB) continues to be a major health burden worldwide. Both the inability of the immune system to resolve CHB and the unique replication strategy employed by HBV, which forms a stable viral covalently closed circular DNA (cccDNA) minichromosome in the hepatocyte nucleus, enable infection persistence. Knowledge of the complex network of interactions that HBV engages with its host is still limited but accumulating evidence indicates that epigenetic modifications occurring both on the cccDNA and on the host genome in the course of infection are essential to modulate viral activity and likely contribute to pathogenesis and cancer development. Thus, a deeper understanding of epigenetic regulatory processes may open new venues to control and eventually cure CHB. This review summarizes major findings in HBV epigenetic research, focusing on the epigenetic mechanisms regulating cccDNA activity and the modifications determined in infected host cells and tumor liver tissues.

Cell Culture Models and Animal Models for HBV Study

Highly representative and relevant cell and mouse models are required for HBV study, including uncovering its lifecycle, investigation of the viral-host interaction, and development and evaluation of the novel antiviral therapy. During the past 40 years, both HBV cell culture models and animal models have evolved over several generations, each with significant improvement for specific purposes. In one aspect, HBV cell culture models experienced the original noninfection model including HBV plasmid DNA transfection and HBV genome integrated stable cells such as HepG2.2.15 which constitutively produces HBV virus and HepAD38 cells and its derivatives which drug-regulated HBV production. As for HBV infection models, HepaRG cells once dominated the HBV infection field for over a decade, but its complicated and labor-extensive cell differentiation procedures discouraged primary researchers from stepping in the field. The identification of human NTCP as HBV receptor evoked great enthusiasm of the whole HBV field, and its readily adaptive characteristic makes it popular in many HBV laboratories. Recombinant cccDNA (rc-cccDNA) emerged recently aiming to tackle the very basic question of how to eventually eradicate cccDNA without HBV real virus infection. In the other aspect, HBV transgenic mouse was firstly generated in the 1990s, which was helpful to decipher HBV production in vivo. However, the HBV transgenic mice were naturally immune tolerant to HBV viral products. Subsequently, a series of nonintegrated HBV mouse models were generated through plasmid hydrodynamic tail vein injection and viral vector-mediated delivery approaches, and HBV full life cycle was incomplete as cccDNA was not formed from HBV relaxed circular DNA (rcDNA). Human NTCP transgenic mouse still could not support productive HBV infection, and humanized mouse liver with human hepatocytes which supported whole HBV life cycle still dominates HBV infection in vivo, a value but expensive model until now. Other methods to empower mouse to carry HBV cccDNA were also exploited. In this chapter, we summarized the advantages and disadvantages of each model historically and provided protocols for HBV infection in HepG2-NTCP cells, HBV rc-cccDNA transfection in HepG2 cells, and HBV infection in NRG-Fah-/- liver humanized mouse.

A Broad Application of CRISPR Cas9 in Infectious Diseases of Central Nervous System

Virus-induced diseases or neurological complications are huge socio-economic burden to human health globally. The complexity of viral-mediated CNS pathology is exacerbated by reemergence of new pathogenic neurotropic viruses of high public relevance. Although the central nervous system is considered as an immune privileged organ and is mainly protected by barrier system, there are a vast majority of neurotropic viruses capable of gaining access and cause diseases. Despite continued growth of the patient population and a number of treatment strategies, there is no successful viral specific therapy available for viral induced CNS diseases. Therefore, there is an urgent need for a clear alternative treatment strategy that can effectively target neurotropic viruses of DNA or RNA genome. To address this need, rapidly growing gene editing technology based on CRISPR/Cas9, provides unprecedented control over viral genome editing and will be an effective, highly specific and versatile tool for targeting CNS viral infection. In this review, we discuss the application of this system to control CNS viral infection and associated neurological disorders and future prospects. Graphical Abstract CRISPR/Cas9 technology as agent control over CNS viral infection.

Evans Blue Inhibits HBV Replication Through a Dual Antiviral Mechanism by Targeting Virus Binding and Capsid Assembly

Chronic hepatitis B (CHB) is a global health problem caused by human hepatitis B virus (HBV). Current treatment with interferons and nucleos(t)ide analogs (NAs) can cause population tolerance and drug resistance. Therefore, new antiviral drugs, especially those targeting host factors, are urgently needed. Here, we identified Evans blue as a new HBV inhibitor by screening an FDA drug library using Huh7D^hNTCP cells and confirmed the antiviral activity in primary human hepatocytes and human sodium taurocholate cotransporting polypeptide (hNTCP)-transfected porcine primary hepatocytes. Our efficacy study showed that Evans blue has an IC₅₀ of 2 μM against HBV infection in Huh7D^hNTCP cells, and no apparent toxicity at up to 1000 μM. The IC₅₀ of Evans blue against HBV in primary human hepatocytes was approximately 5 μM. Mechanism studies revealed that Evans blue has a dual anti-HBV effect. It inhibits both the binding of viral preS1 to host cells through the host factor NTCP and the virus capsid assembly by targeting the host factor BK channel. The K_D of the direct interaction between Evans blue and NTCP is 8.82E-8 M. Evans blue can suppress capsid assembly at micromolar concentrations by reducing the cytosolic calcium ion concentration. Since the antiviral effects on HBV binding and assembly are both achieved through targeting host factors, Evans blue inhibits the infection of nucleos(t)ide analog drug-resistant HBV strains in Huh7D^hNTCP cells. Taken together, our results suggest that Evans blue may be a promising anti-HBV drug candidate in the classes of both entry and assembly inhibitors.

A Novel Hepadnavirus is Associated with Chronic Hepatitis and Hepatocellular Carcinoma in Cats

In 2015, over 850,000 people died from chronic hepatitis and hepatocellular carcinoma (HCC) caused by hepatitis B virus (HBV). A novel hepatitis B-like virus has recently been identified in domestic cats. The pathogenic potential of domestic cat hepadnavirus (DCH), for which 6.5% to 10.8% of pet cats are viremic, is unknown. We evaluated stored formalin-fixed, paraffin-embedded biopsies of diseased and normal feline liver for the presence of DCH using PCR and in situ hybridization (ISH). DCH was detected in 43% (6/14) of chronic hepatitis cases and 28% (8/29) of HCCs, whereas cholangitis (n = 6), biliary carcinoma (n = 18) and normal liver (n = 15) all tested negative for DCH. Furthermore, in DCH-associated cases, the histologic features of inflammation and neoplasia, and the viral distribution on ISH were strikingly similar to those seen with HBV-associated disease. Several histological features common in human HBV-associated hepatitis, including piecemeal necrosis and apoptotic bodies, were identified in DCH-positive cases of chronic hepatitis. In two cases of HCC examined, the proliferation index in regions that were ISH-positive was higher than in ISH-negative regions. The intracellular distribution of virus in both hepatitis and HCC demonstrated that viral nucleic acid is present in both nuclear and cytoplasmic forms. Collectively, these findings demonstrate a compelling association between DCH and some cases of chronic hepatitis and hepatocellular carcinoma in the cat that mirrors features of HBV-associated hepatopathies. Future investigations of viral epidemiology and natural history are needed to establish the impact of DCH on feline health.

TPX2 silencing exerts anti‑tumor effects on hepatocellular carcinoma by regulating the PI3K/AKT signaling pathway

Hepatocellular carcinoma (HCC) is one of the primary causes of cancer-associated deaths worldwide. Current treatment methods include surgical resection, chemotherapy and radiotherapy; however the curative rate remains low, thus novel treatments are required. The aim of the present study was to investigate the role of targeting protein for Xenopus kinesin-like protein 2 (TPX2) in the growth of HCC and its underlying molecular mechanism. Immunohistochemistry staining, reverse transcription-quantitative (RT-q)PCR and western blotting were used to detect the expression of TPX2 mRNA and protein in liver cancer tissue samples, adjacent normal liver tissue samples, and the HCC cell lines Huh7, Hep3B, PLC/PRF/5 and MHCC97-H. The recombinant plasmid pMagic4.1-shRNA-TPX2 was constructed and transfected into Huh7 and Hep3B HCC cells to silence TPX2 expression. The proliferation, apoptosis, migration and invasion of Huh7 cells and Hep3B cells were evaluated before and after TPX2 silencing. The mRNA and protein expression levels of multiple signaling pathway-associated genes were detected by RT-qPCR and western blotting. The expression levels of TPX2 mRNA and protein were significantly higher in HCC tissue samples compared with adjacent normal liver tissue sample. TPX2 mRNA and protein expression levels were detected in the different HCC cell lines. The recombinant plasmid pMagic4.1-shRNA-TPX2 was successfully transfected into Huh7 and Hep3B cells, resulting in TPX2 silencing. TPX2 knockdown significantly reduced cell proliferation, cell migration and cell invasion of Huh7 and Hep3B cells, whilst also increasing the rate of apoptosis in these cells. Following TPX2 silencing, the expression levels of PI3K, phospho-AKT, Bcl-2, c-Myc and Cyclin D1 were significantly decreased, whereas the expression levels of P21 and P27 were significantly increased. In conclusion, TPX2 may suppress the growth of HCC by regulating the PI3K/AKT signaling pathway and thus, TPX2 may be a potential target for the treatment of liver cancer.

Drugs in the Pipeline for HBV

Chronic hepatitis B remains a significant cause of morbidity and mortality worldwide. Most hepatitis B virus (HBV)-infected individuals are neither diagnosed nor treated. In those treated, nucleos(t)ide polymerase inhibitors persistently suppress viremia to the limits of quantitation; however, few achieve a "functional cure," defined as sustained off-treatment loss of detectable serum HBV DNA with or without loss of hepatitis B surface antigen. The low cure rate has been attributed to an inability to eliminate the viral reservoir of covalently closed circular DNA from hepatocytes. This review focuses on the diverse therapeutic approaches currently under development that may contribute to the goal of HBV cure.

Stem Cell-Derived Hepatocyte-Like Cells as Model for Viral Hepatitis Research

Viral hepatitis, the leading cause of liver diseases worldwide, is induced upon infection with hepatotropic viruses, including hepatitis A, B, C, D, and E virus. Due to their obligate intracellular lifestyles, culture systems for efficient viral replication are vital. Although basic and translational research on viral hepatitis has been performed for many years, conventional hepatocellular culture systems are not optimal. These studies have greatly benefited from recent efforts on improving cell culture models for virus replication and infection studies. Here we summarize the use of human stem cell-derived hepatocyte-like cells for hepatotropic virus infection studies, including the dissection of virus-host interactions and virus-induced pathogenesis as well as the identification and validation of novel antiviral agents.

Will Infant Hepatitis B Immunization Protect Adults?

Globally, infant hepatitis B virus (HBV) immunization programs are markedly reducing the rate of chronic HBV infections among children <5 years of age. Desirable improvements include increased birth dose coverage and better prevention of perinatal HBV transmission. Follow-up studies show that by the teenage years most of those immunized as infants have lost circulating anti-HBs antibody and some fail to respond to challenge HBV vaccination, implying loss of protection from infection. With high exposure to HBV, such individuals can develop breakthrough HBV infection but this rarely leads to chronic infection, the main goal of prevention programs. While longer-term follow-up studies into adulthood are needed, current evidence does not support a need for booster immunization of otherwise healthy teens or young adults.

HBV T1719G mutation reduced HBV replication through mutant Enh II and HBx protein in vitro

It was repeatedly reported that the hepatitis B virus (HBV) T1719G mutation was very common and related to progression and malignancy of liver disease. However, its effect on viral replication efficiency remains unclear. In this study, we aimed to evaluate the function and mechanisms of the T1719G mutation on viral replication capacity. Wild-type and T1719G mutation-bearing HBV1.2× plasmids were transfected into Huh7 and HepG2 cells, respectively, and HBV total RNA, 3.5 kb RNA and supernatant HBV DNA were assessed using real-time PCR, hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) levels were measured by time-resolved fluoroimmunoassay. In order to assess Enh II activity and the binding capacity of HNF3β to Enh II sequence, dual-luciferase assay and Chromatin immunoprecipitation (ChIP)-PCR were employed, respectively. Simultaneously, the HBx or HBx-mut (T1719G) plasmid was co-transfected to evaluate the effect of HBx on viral replication. Our results showed that the T1719G mutation impaired viral replication efficacy compared with the wild type both by reducing Enh II activity and binding capacity of HNF3β with Enh II. And such reduction caused by T1719G mutation could be rescued by HBx protein. Our results show that the T1719G mutation decreases HBV viral replication capacity possibly by mutant HBx protein and altered Enh II activity.

The Role of Promyelocytic Leukemia Protein in Steatosis-Associated Hepatic Tumors Related to Chronic Hepatitis B virus Infection

The persistence of hepatitis B surface antigen (HBsAg) is a risk factor for the development of steatosis-associated tumors in chronic hepatitis B virus (HBV) infection, yet little is known about the metabolic link with this factor. We correlated HBV-related pathogenesis in genetically engineered mice and human carriers with metabolic proteomics and lipogenic gene expression profiles. The immunohistochemistry showed that the promyelocytic leukemia protein (PML, a tumor suppressor involved in genome maintenance and fatty acid oxidation), being inversely influenced by the dynamic HBsAg levels from acute phase to seroclearance, appeared as a lipo-metabolic switch linking HBsAg-induced steatosis (lipogenesis) to HBsAg-lost fat-burning hepatocarcinogenesis (lipolysis). Knockdown of PML in HBsAg-transgenic mice predisposed to obesity and drove early steatosis-specific liver tumorigenesis. Proteome analysis revealed that the signaling pathways corresponding to energy metabolism and its regulators were frequently altered by suppression or depletion of PML in the HBsAg-transgenic mice, mainly including oxidative phosphorylation and fatty acid metabolism. Expression profiling further identified upregulation of stearoyl-CoA desaturase 1 (Scd1) and epigenetic methylation of NDUFA13 in the mitochondrial respiratory chain and the cell cycle inhibitor CDKN1c in concordance to the increased severity of lipodystrophy and neoplasia in the livers of HBsAg-transgenic mice with PML insufficiency. The defect in lipolysis in PML-deficient HBsAg-transgenic mice made the HBsAg-induced adipose-like liver tumors vulnerable to synthetic lethality from toxic saturated fat accumulation with a Scd1 inhibitor. Our findings provide mechanistic insights into the evolution of steatosis-associated hepatic tumors driven by reciprocal interactions of HBsAg and PML, and a potential utility of lipid metabolic reprogramming as a treatment target.

The Role of Infected Cell Proliferation in the Clearance of Acute HBV Infection in Humans

Around 90-95% of hepatitis B virus (HBV) infected adults do not progress to the chronic phase and, instead, recover naturally. The strengths of the cytolytic and non-cytolytic immune responses are key players that decide the fate of acute HBV infection. In addition, it has been hypothesized that proliferation of infected cells resulting in uninfected progeny and/or cytokine-mediated degradation of covalently closed circular DNA (cccDNA) leading to the cure of infected cells are two major mechanisms assisting the adaptive immune response in the clearance of acute HBV infection in humans. We employed fitting of mathematical models to human acute infection data together with physiological constraints to investigate the role of these hypothesized mechanisms in the clearance of infection. Results suggest that cellular proliferation of infected cells resulting in two uninfected cells is required to minimize the destruction of the liver during the clearance of acute HBV infection. In contrast, we find that a cytokine-mediated cure of infected cells alone is insufficient to clear acute HBV infection. In conclusion, our modeling indicates that HBV clearance without lethal loss of liver mass is associated with the production of two uninfected cells upon proliferation of an infected cell.

Interleukin-34 inhibits hepatitis B virus replication in vitro and in vivo

Background

The hepatitis B virus (HBV) infection could activate the immune system and induce extensive inflammatory response. As the most important inflammatory factor, interleukins are critical for anti-viral immunity. Here we investigated whether interleukin-34 (IL-34) play a role in HBV infection.

Methodology/Principal findings

In this study, we first found that both serum IL-34 and IL-34 mRNA in PBMCs in chronic HBV patients was significantly decreased compared to the healthy controls. Furthermore, both IL-34 protein and mRNA levels were declined hepatoma cells expressing HBV. In addition, the clinical parameters analysis found that serum IL-34 was significantly associated with HBV DNA (P = 0.0066), ALT (P = 0.0327), AST (P = 0.0435), TB (P = 0.0406), DB (P = 0.0368) and AFP (P = 0.0225). Correlation analysis also found that serum IL-34 negatively correlated with HBV DNA copies, ALT and AST. In vitro studies found that IL-34 treatment in HepAD38 and HepG2.2.15 cells markedly inhibited HBV DNA, total RNA, 3.5kb mRNA and HBc protein. In vivo studies further demonstrated IL-34 treatment in HBV transgenic mice exhibited greater inhibition on HBV DNA, total RNA, 3.5kb mRNA and HBc protein, suggesting the effect to IL-34 on HBV is likely due to host innate or adaptive immune response.

Conclusions/Significance

Our study identified a novel interleukin, IL-34, which has anti-viral activity in HBV replication in hepatocytes in vitro and in vivo. These data suggest a rationale for the use of IL-34 in the HBV treatment.