New perspectives on the hepatitis B virus life cycle in the human liver

The Complex Role of HBeAg and Its Precursors in the Pathway to Hepatocellular Carcinoma

Hepatitis B virus (HBV) is one of the seven known human oncogenic viruses and has adapted to coexist with a single host for prolonged periods, requiring continuous manipulation of immunity and cell fate decisions. The persistence of HBV infection is associated with the pathogenesis of hepatocellular carcinoma, and various HBV proteins have been implicated in promoting this persistence. The precursor of hepatitis e antigen (HBeAg), is translated from the precore/core region and is post-translationally modified to yield HBeAg, which is secreted in the serum. HBeAg is a non-particulate protein of HBV and can act as both a tolerogen and an immunogen. HBeAg can protect hepatocytes from apoptosis by interfering with host signalling pathways and acting as a decoy to the immune response. By evading the immune response and interfering with apoptosis, HBeAg has the potential to contribute to the hepatocarcinogenic potential of HBV. In particular, this review summarises the various signalling pathways through which HBeAg and its precursors can promote hepatocarcinogenesis via the various hallmarks of cancer.

Hepatitis B and Hepatitis D Viruses: A Comprehensive Update with an Immunological Focus

Hepatitis B virus (HBV) and hepatitis delta virus (HDV) are highly prevalent viruses estimated to infect approximately 300 million people and 12-72 million people worldwide, respectively. HDV requires the HBV envelope to establish a successful infection. Concurrent infection with HBV and HDV can result in more severe disease outcomes than infection with HBV alone. These viruses can cause significant hepatic disease, including cirrhosis, fulminant hepatitis, and hepatocellular carcinoma, and represent a significant cause of global mortality. Therefore, a thorough understanding of these viruses and the immune response they generate is essential to enhance disease management. This review includes an overview of the HBV and HDV viruses, including life cycle, structure, natural course of infection, and histopathology. A discussion of the interplay between HDV RNA and HBV DNA during chronic infection is also included. It then discusses characteristics of the immune response with a focus on reactions to the antigenic hepatitis B surface antigen, including small, middle, and large surface antigens. This paper also reviews characteristics of the immune response to the hepatitis D antigen (including small and large antigens), the only protein expressed by hepatitis D. Lastly, we conclude with a discussion of recent therapeutic advances pertaining to these viruses.

Viral hepatitis: A narrative review of hepatitis A–E

Viral hepatitis continues to be a major health concern leading to hepatic decompensation ranging from acute hepatitis to cirrhosis and hepatocellular carcinoma. The hepatic and extrahepatic manifestations are not only debilitating but also associated with a significant economic burden. Over the last two decades, the field of virology has made significant breakthroughs leading to a better understanding of the pathophysiology of viral hepatitis, which in turn has led to new therapeutic options. The advent of direct-acting antiviral agents changed the landscape of hepatitis C virus (HCV) therapy, and new drugs are in the pipeline for chronic hepatitis B virus (HBV) treatment. There has also been a significant emphasis on screening and surveillance programs, widespread availability of vaccines, and linkage of care. Despite these efforts, significant gaps persist in care, and there is a pressing need for increased collaboration and teamwork across the globe to achieve a reduction of disease burden and elimination of HBV and HCV.

HIV Infection Predisposes to Increased Chances of HBV Infection: Current Understanding of the Mechanisms Favoring HBV Infection at Each Clinical Stage of HIV Infection

Human immunodeficiency virus (HIV) selectively targets and destroys the infection-fighting CD4+ T-lymphocytes of the human immune system, and has a life cycle that encompasses binding to certain cells, fusion to that cell, reverse transcription of its genome, integration of its genome into the host cell DNA, replication of the HIV genome, assembly of the HIV virion, and budding and subsequent release of free HIV virions. Once a host is infected with HIV, the host’s ability to competently orchestrate effective and efficient immune responses against various microorganisms, such as viral infections, is significantly disrupted. Without modern antiretroviral therapy (ART), HIV is likely to gradually destroy the cellular immune system, and thus the initial HIV infection will inexorably evolve into acquired immunodeficiency syndrome (AIDS). Generally, HIV infection in a patient has an acute phase, a chronic phase, and an AIDS phase. During these three clinical stages, patients are found with relatively specific levels of viral RNA, develop rather distinctive immune conditions, and display unique clinical manifestations. Convergent research evidence has shown that hepatitis B virus (HBV) co-infection, a common cause of chronic liver disease, is fairly common in HIV-infected individuals. HBV invasion of the liver can be facilitated by HIV infection at each clinical stage of the infection due to a number of contributing factors, including having identical transmission routes, immunological suppression, gut microbiota dysbiosis, poor vaccination immune response to hepatitis B immunization, and drug hepatotoxicity. However, there remains a paucity of research investigation which critically describes the influence of the different HIV clinical stages and their consequences which tend to favor HBV entrenchment in the liver. Herein, we review advances in the understanding of the mechanisms favoring HBV infection at each clinical stage of HIV infection, thus paving the way toward development of potential strategies to reduce the prevalence of HBV co-infection in the HIV-infected population.

Imaging of Hepatitis B Virus Nucleic Acids: Current Advances and Challenges

Hepatitis B virus infections are the main reason for hepatocellular carcinoma development. Current treatment reduces the viral load but rarely leads to virus elimination. Despite its medical importance, little is known about infection dynamics on the cellular level not at least due to technical obstacles. Regardless of infections leading to extreme viral loads, which may reach 10¹⁰ virions per mL serum, hepatitis B viruses are of low abundance and productivity in individual cells. Imaging of the infections in cells is thus a particular challenge especially for cccDNA that exists only in a few copies. The review describes the significance of microscopical approaches on genome and transcript detection for understanding hepatitis B virus infections, implications for understanding treatment outcomes, and recent microscopical approaches, which have not been applied in HBV research.

Evaluation of the in situ assay for HBV DNA: An observational real-world study in chronic hepatitis B

The visualization of intrahepatic hepatitis B virus (HBV) DNA by in situ hybridization (ISH) has uncovered some interesting aspects of HBV life cycle at the single-cell level. In the current study, we intend to evaluate the reliability and robustness of this assay in the real-world clinical scenario and its relationship with currently available clinical biomarkers in chronic hepatitis B (CHB) patients.In this cross-sectional study, 94 CHB patients and 10 patients with non-HBV related liver diseases were enrolled. Liver biopsies and routine histopathology analysis were performed. Intrahepatic HBV DNA and viral antigens (HBsAg and HBcAg) were detected by ISH and immunohistochemistry (IHC), respectively. The basic biochemical and virological parameters such as alanine transaminase, serum HBV DNA, and serum HBsAg were measured.The HBV DNA-ISH assay showed 55.8% (53/94 cases) positive rate in CHB patients, no false positive was found in non-HBV related hepatitis. The IHC of HBsAg and HBcAg showed a positive rate of 94.7% (89/94 cases) and 19.5% (17/87 cases), respectively. Quantification of HBV DNA-ISH signal showed a significant correlation with serum HBV DNA (rs = 0.6223, P < .0001). In addition, the staining pattern of HBV DNA in situ in the context of collagen deposition informed the histopathological progression of chronic liver disease.The application of this ISH assay in evaluating intrahepatic viral replication in real-world CHB patients showed favorable performance. It can be a complementation to conventional liver histopathology examination and IHC detection of viral antigens. This methodology provides an intuitive assessment of virological and pathological state of CHB patients, and further supports clinical diagnosis and management.

Minicircle DNA vector expressing interferon-lambda-3 inhibits hepatitis B virus replication and expression in hepatocyte-derived cell line

BACKGROUND

Interferon-alpha (IFNα) is a first-line treatment option for chronic hepatitis B virus (HBV) infection, but the severe systemic side-effects limited its clinical application. Interferon-lambda (IFNλ) with comparable antiviral activity and less toxic side-effects is thought to be a good alternative interferon to IFNα. Additionally, the gene vector mediated sustainably expression of therapeutic product in the target cells/tissue may overcome the shortcomings resulted from the short half-life of IFNs.

RESULTS

We constructed a liver-specific IFNλ3-expressing minicircle (MC) vector under the control of a hepatocyte-specific ApoE promoter (MC.IFNλ3) and investigated its anti-HBV activity in a HBV-expressing hepatocyte-derived cell model (HepG2.2.15). As expected, the MC.IFNλ3 vector capable of expressing IFNλ3 in the recipient hepatocytes has demonstrated robust anti-HBV activity, in terms of suppressing viral antigen expression and viral DNA replication, via activation the interferon-stimulated gene (ISG) expression in HepG2.2.15 cells.

CONCLUSIONS

Given the MC vector can be easily delivered into liver, the liver-targeted IFN gene-transfer (MC.IFNλ3), instead of systemic administrating IFN repeatedly, provides a promising concept for the treatment of chronic HBV infection.

Multifactorial heterogeneity of virus-specific T cells and association with the progression of human chronic hepatitis B infection

Associations between chronic antigen stimulation, T cell dysfunction, and the expression of various inhibitory receptors are well characterized in several mouse and human systems. During chronic hepatitis B virus (HBV) infection (CHB), T cell responses are blunted with low frequencies of virus-specific T cells observed, making these parameters difficult to study. Here, using mass cytometry and a highly multiplexed combinatorial peptide–major histocompatibility complex (pMHC) tetramer strategy that allows for the detection of rare antigen-specific T cells, we simultaneously probed 484 unique HLA-A*1101–restricted epitopes spanning the entire HBV genome on T cells from patients at various stages of CHB. Numerous HBV-specific T cell populations were detected, validated, and profiled. T cells specific for two epitopes (HBVpol387and HBVcore169) displayed differing and complex heterogeneities that were associated with the disease progression, and the expression of inhibitory receptors on these cells was not linearly related with their extent of T cell dysfunction. For HBVcore169-specific CD8+T cells, we found cellular markers associated with long-term memory, polyfunctionality, and the presence of several previously unidentified public TCR clones that correlated with viral control. Using high-dimensional trajectory analysis of these cellular phenotypes, a pseudo-time metric was constructed that fit with the status of viral infection in corresponding patients. This was validated in a longitudinal cohort of patients undergoing antiviral therapy. Our study uncovers complex relationships of inhibitory receptors between the profiles of antigen-specific T cells and the status of CHB with implications for new strategies of therapeutic intervention.

Microbial Agents as Putative Inducers of B Cell Lymphoma in Sjögren's Syndrome through an Impaired Epigenetic Control: The State-of-The-Art

Introduction

Understanding the mechanisms underlying the pathogenesis of Sjögren's syndrome (SS) is crucially important in order to be able to discriminate the steps that lead to B cell transformation and promptly identify the patients at risk of lymphomagenesis. The aim of this narrative review is to describe the evidence concerning the role that infections or dysbiosis plays in the epigenetic control of gene expression in SS patients and their possible involvement in B cell lymphomagenesis.

Materials and Methods

We searched the PubMed and Google Scholar databases and selected a total of 92 articles published during the last 25 years that describe experimental and clinical studies of the potential associations of microbiota and epigenetic aberrations with the risk of B cell lymphoma in SS patients.

Results and Discussion

The genetic background of SS patients is characterized by the hyperexpression of genes that are mainly involved in regulating the innate and adaptive immune responses and oncogenesis. In addition, salivary gland epithelial cells and lymphocytes both have an altered epigenetic background that enhances the activation of proinflammatory and survival pathways. Dysbiosis or chronic latent infections may tune the immune response and modify the cell epigenetic machinery in such a way as to give B lymphocytes an activated or transformed phenotype. It is also worth noting that transposable integrated retroelements may participate in the pathogenesis of SS and B cell lymphomagenesis by inducing DNA breaks, modulating cell gene expression, or generating aberrant transcripts that chronically stimulate the immune system.

Conclusions

Microorganisms may epigenetically modify target cells and induce their transcriptome to generate an activated or transformed phenotype. The occurrence of lymphoma in more than 15% of SS patients may be the end result of a combination of genetics, epigenetics, and dysbiosis or latent infections.

Clinical Implications of Hepatitis B Virus RNA and Covalently Closed Circular DNA in Monitoring Patients with Chronic Hepatitis B Today with a Gaze into the Future: The Field Is Unprepared for a Sterilizing Cure

. Chronic hepatitis B virus (HBV) infection has long remained a critical global health issue. Covalently closed circular DNA (cccDNA) is a persistent form of the HBV genome that maintains HBV chronicity. Decades of extensive research resulted in the two therapeutic options currently available: nucleot(s)ide analogs and interferon (IFN) therapy. A plethora of reliable markers to monitor HBV patients has been established, including the recently discovered encapsidated pregenomic RNA in serum, which can be used to determine treatment end-points and to predict the susceptibility of patients to IFN. Additionally, HBV RNA splice variants and cccDNA and its epigenetic modifications are associated with the clinical course and risks of hepatocellular carcinoma (HCC) and liver fibrosis. However, new antivirals, including CRISPR/Cas9, APOBEC-mediated degradation of cccDNA, and T-cell therapies aim at completely eliminating HBV, and it is clear that the diagnostic arsenal for defining the long-awaited sterilizing cure is missing. In this review, we discuss the currently available tools for detecting and measuring HBV RNAs and cccDNA, as well as the state-of-the-art in clinical implications of these markers, and debate needs and goals within the context of the sterilizing cure that is soon to come.

Host and viral factors associated with serum hepatitis B virus RNA levels among patients in need for treatment

Hepatitis B virus (HBV) RNA in serum is a novel biomarker for intrahepatic HBV replication and treatment response. For its proper use, it is essential to identify factors influencing serum HBV RNA level. Using a rapid amplification of complimentary DNA (cDNA) ends (RACE) PCR technique (lower limit of detection [LLD], 800 copies/mL [c/mL]), serum HBV RNA levels were measured in samples of 488 untreated individuals with chronic HBV infection who were eligible to treatment according to currently used recommendations. We explored the association of serum levels of HBV RNA with patient- and virus-associated factors. HBV genotype distribution was 21/10/20/46/3% for A/B/C/D/other. Mean HBV RNA serum level was 5.9 (1.6) log₁₀ c/mL (hepatitis B e antigen [HBeAg]-positive chronic hepatitis B [CHB], 6.5 [1.2] log c/mL; HBeAg-negative CHB, 4.1 [1.2] log c/mL; P < 0.001). By multivariable linear regression, factors associated with lower HBV RNA level were HBeAg negativity (β = -0.69; P < 0.001), HBV genotypes A (β = -0.13; P = 0.002), B (β = -0.07; P = 0.049), and C (β = -0.61; P < 0.001) in comparison to D, and presence of HBV basal core promoter mutation either alone (β = -0.14; P = 0.001) or in combination with precore mutation (β = -0.22; P < 0.001). Higher serum alanine aminotransferase (ALT) was associated with higher HBV RNA (β = 0.23; P < 0.001). HBV RNA correlated strongly with HBV DNA (HBeAg-pos, r = 0.72; P < 0.001; HBeAg-neg, r = 0.78; P < 0.001) and moderately with quantitative hepatitis B surface antigen (qHBsAg; HBeAg-pos, r = 0.54; P < 0.001; HBeAg-neg, r = 0.19; P = 0.04) and quantitative hepatitis B surface antigen (qHBeAg; r = 0.41; P < 0.001).

CONCLUSION

In this multiethnic cohort of 488 untreated individuals with CHB, factors associated with serum HBV RNA level were HBeAg status, serum ALT, HBV genotype, and presence of basal core promotor mutations. For the future use of serum HBV RNA as a clinical marker, it seems mandatory to take these factors into consideration. (Hepatology 2018).

HIV-hepatitis B virus coinfection: epidemiology, pathogenesis, and treatment

: HIV infection has a significant impact on the natural history of chronic hepatitis B virus (HBV) infection, with increased levels of HBV DNA, accelerated progression of liver disease and increased liver-associated mortality compared with HBV monoinfection. Widespread uptake and early initiation of HBV-active antiretroviral therapy has substantially improved the natural history of HIV-HBV coinfection but the prevalence of liver disease remains elevated in this population. In this paper, we review recent studies examining the natural history and pathogenesis of liver disease and seroconversion in HIV-HBV coinfection in the era of HBV-active antiretroviral therapy and the effects of HIV directly on liver disease. We also review novel therapeutics for the management of HBV with a particular emphasis on clinical strategies being developed for an HBV cure and an HIV cure and their impact on HIV-HBV coinfected individuals.

Review article: novel therapies for hepatitis B virus cure - advances and perspectives

BACKGROUND

Current anti-viral therapies, interferon and nucleos(t)ide analogues, have been proven to reduce the progression of chronic hepatitis B (CHB). However, covalently closed circular DNA (cccDNA) of hepatitis B virus (HBV) persists, resulting in viral relapse after the discontinuation of treatment.

AIM

To discuss and review novel therapies for chronic hepatitis B infection.

METHODS

Recent published studies which searched from PubMed were comprehensive reviewed. The key words include chronic hepatitis B, hepatitis B virus cure, covalently closed circular DNA, direct acting anti-virals and host targeting agents.

RESULTS

Several novel agents through viral and host targets approaches are under investigations towards functional cure of HBV. On the one hand, direct acting anti-virals targeting virus itself, such as HBV new polymerase inhibitor, entry inhibitor, engineered site-specific nucleases and RNA interference, could inhibit amplification of cccDNA as well as intrahepatic HBV infection and eliminate or silence cccDNA transcription. Inhibitors of HBV nucleocapsid assembly suppress capsid formation and prevent synthesis of HBV DNA. On the other hand, host targeting agents (HTA) include lymphotoxin-β receptor agonist, toll-like receptor agonist, immune checkpoint inhibitors and adenovirus-based therapeutic vaccine. Through enhancing innate and adaptive immune responses, these agents could induce noncytolytic destruction of cccDNA or attack HBV-infected hepatocytes.

CONCLUSION

With these promising approaches, we hope to reach global hepatitis B virus control in the middle of this century.