HBV/HDV Coinfection: A Challenge for Therapeutics

Current perspectives of viral hepatitis

Viral hepatitis represents a major danger to public health, and is a globally leading cause of death. The five liver-specific viruses: Hepatitis A virus, hepatitis B virus, hepatitis C virus, hepatitis D virus, and hepatitis E virus, each have their own unique epidemiology, structural biology, transmission, endemic patterns, risk of liver complications, and response to antiviral therapies. There remain few options for treatment, in spite of the increasing prevalence of viral-hepatitis-caused liver disease. Furthermore, chronic viral hepatitis is a leading worldwide cause of both liver-related morbidity and mortality, even though effective treatments are available that could reduce or prevent most patients' complications. In 2016, the World Health Organization released its plan to eliminate viral hepatitis as a public health threat by the year 2030, along with a discussion of current gaps and prospects for both regional and global eradication of viral hepatitis. Today, treatment is sufficiently able to prevent the disease from reaching advanced phases. However, future therapies must be extremely safe, and should ideally limit the period of treatment necessary. A better understanding of pathogenesis will prove beneficial in the development of potential treatment strategies targeting infections by viral hepatitis. This review aims to summarize the current state of knowledge on each type of viral hepatitis, together with major innovations.

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.

HepG2BD: A Novel and Versatile Cell Line with Inducible HDV Replication and Constitutive HBV Expression

Individuals chronically infected with hepatitis B virus (HBV) and hepatitis Delta virus (HDV) present an increased risk of developing cirrhosis and hepatocellular carcinoma in comparison to HBV mono-infected individuals. Although HDV only replicates in individuals coinfected or superinfected with HBV, there is currently no in vitro model that can stably express both viruses simultaneously, mimicking the chronic infections seen in HBV/HDV patients. Here, we present the HepG2BD cell line as a novel in vitro culture system for long-term replication of HBV and HDV. HepG2BD cells derive from HepG2.2.15 cells in which a 2 kb HDV cDNA sequence was inserted into the adeno-associated virus safe harbor integration site 1 (AAVS1) using CRISPR-Cas9. A Tet-Off promoter was placed 5' of the genomic HDV sequence for reliable initiation/repression of viral replication and secretion. HBV and HDV replication were then thoroughly characterized. Of note, non-dividing cells adopt a hepatocyte-like morphology associated with an increased production of both HDV and HBV virions. Finally, HDV seems to negatively interfere with HBV in this model system. Altogether, HepG2BD cells will be instrumental to evaluate, in vitro, the fundamental HBV-HDV interplay during simultaneous chronic replication as well as for antivirals screening targeting both viruses.

Aborted infection of human sodium taurocholate cotransporting polypeptide (hNTCP) expressing woodchuck hepatocytes with hepatitis B virus (HBV)

Due to the limited host range of HBV, research progress has been hindered by the absence of a suitable animal model. The natural history of woodchuck hepatitis virus (WHV) infection in woodchuck closely mirrors that of HBV infection in human, making this species a promising candidate for establishing both in vivo and in vitro HBV infection models. Therefore, this animal may be a valuable species to evaluate HBV vaccines and anti-HBV drugs. A significant milestone in HBV and hepatitis D virus (HDV) infection is the discovery of sodium taurocholate cotransporting polypeptide (NTCP) as the functional receptor. In an effort to enhance susceptibility to HBV infection, we introduced hNTCP into the woodchuck hepatocytes by multiple approaches including transduction of vLentivirus-hNTCP in woodchuck hepatocytes, transfection of p-lentivirus-hNTCP-eGFP plasmids into these cells, as well as transduction of vAdenovirus-hNTCP-eGFP. Encouragingly, our findings demonstrated the successful introduction of hNTCP into woodchuck hepatocytes. However, it was observed that these hNTCP-expressing hepatocytes were only susceptible to HDV infection but not HBV. This suggests the presence of additional crucial factors mediating early-stage HBV infection that are subject to stringent species-specific restrictions.

Performance of Hepatitis Delta Virus (HDV) RNA Testing for the Diagnosis of Active HDV Infection: Systematic Review and Meta-analysis

Background and Aims

Hepatitis delta virus (HDV) is a defective virus and causes severe liver disease. Several HDV RNA assays have been developed, however the diagnostic efficacy remains unclear.This systematic review and meta-analysis aims to evaluate the diagnostic accuracy of HDV RNA assays to aid in the diagnosis of active hepatitis D.

Methods

The PubMed, Embase, and Cochrane Library databases were systematically searched from the beginning to June 31, 2022. Information on the characteristics of the literature and data on sensitivity, specificity, and area under curve (AUC) of the receiver operating characteristic (ROC) were extracted. Stata 14.0 was used for meta-analysis of the combined sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio.

Results

A total of 10 studies were included in the meta-analysis. The summary sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio of HDV RNA assays for HDV diagnosis were 0.92 (95% CI: 0.87-0.95), 0.90 (95% CI: 0.86-0.93), 7.74 (95% CI: 5.31-11.29), 0.10 (95% CI: 0.06-0.18) and 99.90 (95% CI: 47.08-211.99), respectively. The AUC of the pooled ROC curve was 0.95 (95% CI: 0.92-0.96).

Conclusions

The results show that HDV RNA assays had high diagnostic performance. However, that is limited by the number and quality of studies. Standard protocols for the development of assays by manufacturers and larger studies on the use of the assays are needed.

HERACLIS-HDV cohort for the factors of underdiagnosis and prevalence of hepatitis D virus infection in HBsAg-positive patients

BACKGROUND AND AIMS

Hepatitis D virus (HDV) underdiagnosis remains common. We assessed the HDV screening and prevalence rates in HBsAg-positive patients seen at tertiary liver centres throughout Greece as well as factors affecting HDV diagnosis.

METHODS

All adult HBsAg-positive patients seen within the last 5 years were included. Non-screened patients who visited or could be recalled to the clinics over a 6-month period were prospectively tested for anti-HDV.

RESULTS

Of 5079 HBsAg-positive patients, 53% had anti-HDV screening (41% before and 12% after study initiation). Pre-study (8%-88%) and total screening rates (14%-100%) varied widely among centres. Screening rates were associated with older age, known risk group, elevated ALT, centre location and size and period of first visit. Anti-HDV prevalence was 5.8% without significant difference in patients screened before (6.1%) or after study initiation (4.7%, p = 0.240). Anti-HDV positivity was associated with younger age, parenteral drug use, born abroad, advanced liver disease and centre location. Overall, HDV RNA detectability rate was 71.6% being more frequent in anti-HDV-positive patients with elevated ALT, advanced liver disease and hepatitis B therapy.

CONCLUSIONS

Anti-HDV screening rates and recall capabilities vary widely among Greek liver clinics being higher in HBsAg-positive patients of known risk group with active/advanced liver disease seen at smaller centres, while non-medical factors are also important. Anti-HDV prevalence varies throughout Greece being higher in patients born abroad with younger age, parenteral drug use and advanced liver disease. Viremia is more frequently but not exclusively detected in anti-HDV-positive patients with elevated ALT and advanced liver disease.

GCRV NS38 counteracts SVCV proliferation by intracellular antagonization during co-infection

Viral co-infection has been found in animals; however, the mechanisms of co-infection are unclear. The abundance and diversity of viruses in water make fish highly susceptible to co-infection. Here, we reported a co-infection in fish, which resulted in reduced host lethality and illustrated the intracellular molecular mechanism of viral co-infection. The spring viremia of carp virus (SVCV) is a highly lethal virus that infects Cyprinidae, such as zebrafish. The mortality of SVCV infection was significantly reduced when co-infected with the grass carp reovirus (GCRV). The severity of tissue damage and viral proliferation of SVCV was also reduced in co-infection with GCRV. The transcriptome bioinformatics analysis demonstrated that the effect on the host transcripts in response to SVCV infection was significantly reduced in co-infection. After excluding the extracellular interactions of these two viruses, the intracellular mechanisms were studied. We found that the GCRV NS38 remarkably decreased SVCV infection and viral proliferation. The interaction between GCRV NS38 and SVCV nucleoprotein (N) and phosphoprotein (P) proteins was identified, and NS38 downregulated both N and P proteins. Further analysis demonstrated that the N protein was degraded by NS38 indispensable of the autophagy receptor, sequestosome 1 (p62). Meanwhile, K63-linked ubiquitination of the P protein was reduced by NS38, leading to ubiquitinated degradation of the P protein. These results reveal that the intracellular viral protein interactions are a crucial mechanism of co-infection and influence the host pathology and expand our understanding in intracellular viral interactions co-infection.

Sequence diversity of hepatitis D virus in Mongolia

Introduction

The Hepatitis Delta Virus (HDV) is a defective, single-stranded RNA virusoid encoding for a single protein, the Hepatitis Delta Antigen (HDAg), which requires the hepatitis B virus (HBV) envelope protein (HBsAg) for its transmission. Currently, hepatitis D is the most aggressive form of viral hepatitis and treatment options are limited. Worldwide 12 million people are chronically infected with HDV being at high risk for progression to cirrhosis and development of liver cancer.

Objectives

Although it is well established that Mongolia is the country with the highest prevalence of HDV infections, the information on the molecular epidemiology and factors contributing to HDV sequence diversity are largely unclear. The aim of the study was to characterize the sequence diversity of HDV in rural areas from Mongolia and to determine the extent of HLA class I-associated selection pressure.

Patients and methods

From the HepMongolia cohort from rural areas in Mongolia, 451 HBsAg-positive individuals were selected and anti-HDV, HDV-RNA and the sequence of the large HDAg was determined. For all individuals the HLA class I locus was genotyped. Residues under selection pressure in the presence of individual HLA class I types were identified with the recently published analysis tool HAMdetector.

Results

Of 431 HBsAg positive patients, 281 were anti-HDV positive (65%), and HDV-RNA could be detected in 207 of 281 (74%) of patients. The complete large HDAg was successfully sequenced from 131 samples. Phylogenetic analysis revealed that all Mongolian HDV isolates belong to genotype 1, however, they separate into several different clusters without clear regional association. In turn, from phylogeny there is strong evidence for recent local transmission events. Importantly, we found multiple residues with strong support for HLA class I-associated selection pressure consistent with a functional CD8⁺ T cell response directed against HDV.

Conclusion

HDV isolates from Mongolia are highly diverse. The molecular epidemiology suggests circulation of multiple subtypes and provides evidence for ongoing recent transmissions.

A changing landscape: Tracking and analysis of the international HDV epidemiology 1999-2020

The international epidemiology of Hepatitis Delta Virus (HDV) is challenging to accurately estimate due to limited active surveillance for this rare infectious disease. Prior HDV epidemiological studies have relied on meta-analysis of aggregated and static datasets. These limitations restrict the capacity to actively detect low-level and/or geographically dispersed changes in the incidence of HDV diagnoses. This study was designed to provide a resource to track and analyze the international HDV epidemiology. Datasets analyzed collectively consisted of >700,000 HBV and >9,000 HDV reported cases ranging between 1999-2020. Datasets mined from government publications were identified for Argentina, Australia, Austria, Brazil, Bulgaria, Canada, Finland, Germany, Macao, Netherlands, New Zealand, Norway, Sweden, Taiwan, Thailand, United Kingdom, and United States. Time series analyses, including Mann-Kendall (MK) trend test, Bayesian Information Criterion (BIC), and hierarchal clustering, were performed to characterize trends in the HDV timelines. An aggregated prevalence of 2,560 HDV/HBV100,000 cases (95% CI 180-4940) or 2.56% HDV/HBV cases was identified, ranging from 0.26% in Canada to 20% in the United States. Structural breaks in the timeline of HDV incidence were identified in 2002, 2012, and 2017, with a significant increase occurring between 2013-2017. Significant increasing trends in reported HDV and HBV cases were observed in 47% and 24% of datasets, respectively. Analyses of the HDV incidence timeline identified four distinct temporal clusters, including Cluster I (Macao, Taiwan), Cluster II (Argentina, Brazil, Germany, Thailand), Cluster III (Bulgaria, Netherlands, New Zealand, United Kingdom, United States) and Cluster IV (Australia, Austria, Canada, Finland, Norway, Sweden). Tracking of HDV and HBV cases on an international scale is essential in defining the global impact of viral hepatitis. Significant disruptions of HDV and HBV epidemiology have been identified. Increased surveillance of HDV is warranted to further define the etiology of the recent breakpoints in the international HDV incidence.

Specific Binding and Endocytosis of Liposomes to HEK293T Cells via Myrisoylated Pre-S1 Peptide Bound to Sodium Taurocholate Cotransporting Polypeptide

(1) Background: Sodium taurocholate cotransporting polypeptide (NTCP) functions as a key receptor for the hepatitis B virus (HBV) infection. Analyzing HBV and NTCP interaction is an important issue not only for basic research but also for the development of anti-HBV therapeutics. We developed here a novel model system to analyze the interaction of NTCP with liposomes instead of HBV. (2) Methods: Liposomal binding and endocytosis through NTCP in HEK293T cells were achieved by serial treatments of HEL293T cells transiently expressing NTCP-green fluorescence protein (GFP) fusion protein with a synthetic biotinylated pre-S1 peptide (Myr47-Bio) and streptavidin (SA) complex (i.e., Myr47-Bio+SA) followed by biotinylated liposomes. By this procedure, binding of [biotinylated liposomes]-[Myr47-Bio+SA]-[NTCP-GFP] was formed. (3) Results: Using this model system, we found that liposomal binding to NTCP on the cell surface via Myr47-Bio+SA was far more efficient than that to scavenger receptor class B type 1 (SR-B1). Furthermore, liposomes bound to cell surface NTCP via Myr47-Bio+SA were endocytosed into cells after cells were cultured at 37 °C. However, this endocytosis was suppressed by 4 °C or cytochalasin B treatment. (4) Conclusions: This model system will be useful for not only analyzing HBV entry mechanisms but also screening substances to prevent HBV infection.

Innate Immunity, Inflammation, and Intervention in HBV Infection

Hepatitis B virus (HBV) infection is still one of the most dangerous viral illnesses. HBV infects around 257 million individuals worldwide. Hepatitis B in many individuals ultimately develops hepatocellular carcinoma (HCC), which is the sixth most common cancer and the third leading cause of cancer-related deaths worldwide. The innate immunity acts as the first line of defense against HBV infection through activating antiviral genes. Along with the immune responses, pro-inflammatory cytokines are triggered to enhance the antiviral responses, but this may result in acute or chronic liver inflammation, especially when the clearance of virus is unsuccessful. To a degree, the host innate immune and inflammatory responses dominate the HBV infection and liver pathogenesis. Thus, it is crucial to figure out the signaling pathways involved in the activation of antiviral factors and inflammatory cytokines. Here, we review the interplay between HBV and the signal pathways that mediates innate immune responses and inflammation. In addition, we summarize current therapeutic strategies for HBV infection via modulating innate immunity or inflammation. Characterizing the mechanisms that underlie these HBV-host interplays might provide new approaches for the cure of chronic HBV infection.

Digital Droplet PCR for Detection and Quantitation of Hepatitis Delta Virus

INTRODUCTION

Hepatitis delta virus (HDV) far exceeds our expected level. There remains a lack of reliable quantitative assays for HDV RNA detection. We sought to develop a new method based on digital droplet polymerase chain reaction (ddPCR) for HDV quantitative detection.

METHODS

With plasmid (pMD19T) containing HDV full genome, we determined the method for ddPCR-based HDV RNA quantification. To compare various assays for HDV detection, 30 cases diagnosed with hepatitis D and 14 controls were examined using enzyme-linked immunosorbent assay, reverse-transcriptase PCR (RT-PCR), and ddPCR. A total of 728 hepatitis B virus-related patients, including 182 patients with chronic hepatitis B, 182 with liver cirrhosis, 182 with hepatocellular carcinoma, and 182 with liver failure, were screened for HDV infection.

RESULTS

The detection limit of ddPCR for HDV is significantly low, with lower limit of detection and lower limit of quantitation of 0.29 IU/mL (95% confidence interval: 1.93 × 10-3-1.22 IU/mL) and 8.76 IU/mL (95% confidence interval: 1.83-1.03 × 106 IU/mL), respectively. Among the 44 samples, the enzyme-linked immunosorbent assay detected 30 cases positive, ddPCR reported 24 samples, and RT-PCR reported 10 samples positive for HDV RNA. Moreover, the positive rates of anti-HDV were 1.1%, 3.3%, 2.7%, and 7.1% in patients with chronic hepatitis B, liver cirrhosis, hepatocellular carcinoma, and liver failure, respectively; the detection rates of RT-PCR in HDV RNA were 0%, 16.67%, 15.4%, and 20%, respectively. However, the detection rates of ddPCR were 0%, 33.33%, 30.77%, and 60%, respectively.

DISCUSSION

We establish a high sensitivity and specificity quantitative HDV RNA detection method based on ddPCR. Hepatitis B virus-related end-stage liver diseases, especially liver failure, are associated with a remarkably high rate of HDV infection.

Innovative Therapies Targeting the Virus and the Host for Treating Chronic Hepatitis B Virus Infection: From Bench to Bedside

Chronic hepatitis B (CHB) is a highly complicated pathological process in which the disease is initiated by the hepatitis B virus (HBV); however, host immune responses are primarily responsible for variable extents of liver damage. If the patients with CHB remain untreated, many CHB patients will eventually develop complications like cirrhosis of the liver (LC) and hepatocellular carcinoma (HCC). In 2019, an estimated 882,000 patients died due to HBV-related complications worldwide. Accordingly, several drugs with antiviral properties have been used to treat CHB patients during the last four decades. However, the treatment outcome is not satisfactory because viral suppression is not usually related to the containment of progressive liver damage. Although proper reconstruction of host immunity is essential in CHB patients, as of today, there is no acceptable immune therapeutic protocol for them. These realities have exposed new, novel, and innovative therapeutic regimens for the management of CHB patients. This review will update the scope and limitation of the different innovative antiviral and immune therapeutic approaches for restoring effective host immunity and containing the virus in CHB patients to block progression to LC and HCC.

Molecular epidemiology and clinical characteristics of hepatitis D virus infection in Canada

Background & Aims

HDV affects 4.5–13% of chronic hepatitis B (CHB) patients globally, yet the prevalence of HDV infection in Canada is unknown. To investigate the prevalence, genotype, demographics, and clinical characteristics of HDV in Canada, we conducted a retrospective analysis of (1) HDV antibody and RNA positivity among referred specimens, and (2) a cross-sectional subset study of 135 HDV seropositive +/-RNA (HDV+) patients compared with 5,132 HBV mono-infected patients in the Canadian HBV Network.

Methods

Anti-HDV IgG-positive specimens collected between 2012 and 2019 were RNA tested and the genotype determined. Patients enrolled in the Canadian HBV Network were >18 years of age and HBsAg-positive. Clinical data collected included risk factors, demographics, comorbidities, treatment, fibrosis assessment, and hepatic complications.

Results

Of the referred patients, 338/7,080 (4.8%, 95% CI 4.3–5.3) were HDV seropositive, with 219/338 RNA-positive (64.8%, 95% CI 59.6–69.7). The HDV+ cohort were more likely to be born in Canada, to be White or Black/African/Caribbean than Asian, and reporting high-risk behaviours, compared with HBV mono-infected patients. Cirrhosis, complications of end-stage liver disease, and liver transplantation were significantly more frequent in the HDV+ cohort. HDV viraemia was significantly associated with elevated liver transaminases and cirrhosis. Five HDV genotypes were observed among referred patients but no association between genotype and clinical outcome was detected within the HDV+ cohort.

Conclusions

Nearly 5% of the Canadian HBV referral population is HDV seropositive. HDV infection is highly associated with risk behaviours and both domestic and foreign-born patients with CHB. HDV was significantly associated with progressive liver disease highlighting the need for increased screening and surveillance of HDV in Canada.

Lay summary

Evidence of HDV infection was observed in approximately 5% of Canadians who were infected with HBV referred to medical specialists. HDV-positive patients were more likely to be male, born in Canada, or White or Black/African/Caribbean compared to Asian, and to have reported high-risk activities such as injection or intranasal drug use or high-risk sexual contact compared with patients infected with only HBV. Patients infected with HDV were also more likely to suffer severe liver disease, including liver cancer, compared with HBV mono-infected patients.

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There was ∼5% HDV seroprevalence in Canadian HBsAg-positive referred patients.

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HDV genotypes 1, 2, and 5–7 were observed in referred patients.

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HDV+ patients were more likely to be born in Canada, White or Black/African/Caribbean.

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HDV was highly associated with high-risk activities (sexual and intravenous drug use).

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HDV+ patients were more likely diagnosed with cirrhosis or liver cancer.

Binding of Hepatitis B Virus Pre-S1 Domain-Derived Synthetic Myristoylated Peptide to Scavenger Receptor Class B Type 1 with Differential Properties from Sodium Taurocholate Cotransporting Polypeptide

(1) Background: The myristoylated pre-S1 peptide (Myr47) synthesized to mimic pre-S1 domain (2-48) in large (L) surface protein of hepatitis B virus (HBV) prevents HBV infection to hepatocytes by binding to sodium taurocholate cotransporting polypeptide (NTCP). We previously demonstrated that yeast-derived nanoparticles containing L protein (bio-nanocapsules: BNCs) bind scavenger receptor class B type 1 (SR-B1). In this study, we examined the binding of Mry47 to SR-B1. (2) Methods: The binding and endocytosis of fluorescence-labeled Myr47 to SR-B1 (and its mutants)-green fluorescence protein (GFP) fusion proteins expressed in HEK293T cells were analyzed using flow cytometry and laser scanning microscopy (LSM). Various ligand-binding properties were compared between SR-B1-GFP and NTCP-GFP. Furthermore, the binding of biotinylated Myr47 to SR-B1-GFP expressed on HEK293T cells was analyzed via pull-down assays using a crosslinker and streptavidin-conjugated beads. (3) Conclusions: SR-B1 bound not only Myr47 but also its myristoylated analog and BNCs, but failed to bind a peptide without myristoylation. However, NTCP only bound Myr47 among the ligands tested. Studies using SR-B1 mutants suggested that both BNCs and Myr47 bind to similar sites of SR-B1. Crosslinking studies indicated that Myr47 binds preferentially SR-B1 multimer than monomer in both HEK293T and HepG2 cells.

Present and future management of viral hepatitis

Viral hepatitis can result in important morbidity and mortality, with its impact on health conditioned by the specific type of hepatitis, the geographical region of presentation and the development and access to new drugs, among other factors. Most acute presentation forms are self-limiting and may even go unnoticed, with just a small percentage of cases leading to acute liver failure that may necessitate transplantation or even cause the death of the patient. However, when they become chronic, as in the case of hepatitis B virus and C virus, unless they are diagnosed and treated adequately they may have severe consequences, like cirrhosis or hepatocarcinoma. Understanding of the mechanisms of transmission, the pathogenesis, the presence of vaccinations and the development over recent years of new highly-efficient, potent drugs have meant that we are now faced with a new scenario in the management of viral hepatitis, particularly hepatitis B virus and hepatitis C virus. The spectacular advances in hepatitis C virus treatment have led the World Health Organization to propose the objective of its eradication by 2030. The key aspect to achieving this goal is to ensure that these treatments reach all the more vulnerable population groups, in whom the different types of viral hepatitis have a high prevalence and constitute a niche that may perpetuate infection and hinder its eradication. Accordingly, micro-elimination programs assume special relevance at the present time.

Hepatitis B virus/hepatitis D virus epidemiology: Changes over time and possible future influence of the SARS-CoV-2 pandemic

Hepatitis D virus (HDV) is a defective liver-tropic virus that needs the helper function of hepatitis B virus (HBV) to infect humans and replicate. HDV is transmitted sexually or by a parenteral route, in co-infection with HBV or by super-infection in HBV chronic carriers. HDV infection causes acute hepatitis that may progress to a fulminant form (7%-14% by super-infection and 2%-3% by HBV/HDV co-infection) or to chronic hepatitis (90% by HDV super-infection and 2%-5% by HBV/HDV co-infection), frequently and rapidly progressing to cirrhosis or hepatocellular carcinoma (HCC). Peg-interferon alfa the only recommended therapy, clears HDV in only 10%-20% of cases and, consequently, new treatment strategies are being explored. HDV endemicity progressively decreased over the 50 years from the identification of the virus, due to improved population lifestyles and economic levels, to the use of HBV nuclei(t)side analogues to suppress HBV replication and to the application of universal HBV vaccination programs. Further changes are expected during the severe acute respiratory syndrome coronavirus-2 pandemic, unfortunately towards increased endemicity due to the focus of healthcare towards coronavirus disease 2019 and the consequently lower possibility of screening and access to treatments, lower care for patients with severe liver diseases and a reduced impulse to the HBV vaccination policy.

Review of Lambda Interferons in Hepatitis B Virus Infection: Outcomes and Therapeutic Strategies

Hepatitis B virus (HBV) chronically infects over 250 million people worldwide and causes nearly 1 million deaths per year due to cirrhosis and liver cancer. Approved treatments for chronic infection include injectable type-I interferons and nucleos(t)ide reverse transcriptase inhibitors. A small minority of patients achieve seroclearance after treatment with type-I interferons, defined as sustained absence of detectable HBV DNA and surface antigen (HBsAg) antigenemia. However, type-I interferons cause significant side effects, are costly, must be administered for months, and most patients have viral rebound or non-response. Nucleos(t)ide reverse transcriptase inhibitors reduce HBV viral load and improve liver-related outcomes, but do not lower HBsAg levels or impart seroclearance. Thus, new therapeutics are urgently needed. Lambda interferons (IFNLs) have been tested as an alternative strategy to stimulate host antiviral pathways to treat HBV infection. IFNLs comprise an evolutionarily conserved innate immune pathway and have cell-type specific activity on hepatocytes, other epithelial cells found at mucosal surfaces, and some immune cells due to restricted cellular expression of the IFNL receptor. This article will review work that examined expression of IFNLs during acute and chronic HBV infection, the impact of IFNLs on HBV replication in vitro and in vivo, the association of polymorphisms in IFNL genes with clinical outcomes, and the therapeutic evaluation of IFNLs for the treatment of chronic HBV infection.

Investigating the prevalence and clinical effects of hepatitis delta viral infection in Taiwan

PURPOSE

To clarify and investigate the prevalence and clinical impact of hepatitis D virus (HDV) infection in Taiwan's communities.

METHODS

HDV infection in patients with chronic hepatitis B viral (HBV) infection was examined using an anti-HDV antibody in Yonghe Cardinal Tien Hospital (YCTH), a district hospital in Taiwan. Clinical characteristics of anti-HDV-positive and anti-HDV-negative patients were collected and compared. These characteristics were also compared with the data collected from a medical center. Continuous variables and confounding factor adjustments were compared using the analysis of covariance method, whereas categorical variables were compared using the logistic regression method.

RESULTS

A total of 346 patients with chronic HBV infection were assessed from 2018 to 2019. Among them, 4 (1.15%) were positive for anti-HDV. The clinical, virological, and biochemical characteristics were similar between anti-HDV-positive and anti-HDV-negative groups. None of the four patients was positive for serum HDV RNA. Another 18 anti-HDV-positive patients were identified from National Taiwan University Hospital (NTUH). The clinical, virological, and biochemical characteristics of anti-HDV-positive patients from YCTH and NTUH were also similar.

CONCLUSION

The prevalence of HDV and the serum HDV RNA-positive rate were low in district hospitals in Taiwan. Coexisting HDV infection did not influence the clinical manifestation of patients with chronic HBV infection in Taiwan. However, because the number of HDV RNA cases was very small, our findings may not be conclusive. Besides, since the sensitivity of current anti-HDV kit is not 100%, more sensitive methods are needed to achieve reliable prevalence data.

Human hepatitis D virus-specific T cell epitopes

HDV is a small, defective RNA virus that requires the HBsAg of HBV for its assembly, release, and transmission. Chronic HBV/HDV infection often has a severe clinical outcome and is difficult to treat. The important role of a robust virus-specific T cell response for natural viral control has been established for many other chronic viral infections, but the exact role of the T cell response in the control and progression of chronic HDV infection is far less clear. Several recent studies have characterised HDV-specific CD4+ and CD8+ T cell responses on a peptide level. This review comprehensively summarises all HDV-specific T cell epitopes described to date and describes our current knowledge of the role of T cells in HDV infection. While we now have better tools to study the adaptive anti-HDV-specific T cell response, further efforts are needed to define the HLA restriction of additional HDV-specific T cell epitopes, establish additional HDV-specific MHC tetramers, understand the degree of cross HDV genotype reactivity of individual epitopes and understand the correlation of the HBV- and HDV-specific T cell response, as well as the breadth and specificity of the intrahepatic HDV-specific T cell response.

Current status of hepatitis delta

Hepatitis D virus (HDV) infection in patients chronically infected with hepatitis B virus (HBV) causes the most severe form of chronic viral hepatitis and continues to represent a major health problem. The latest data show that the global prevalence is much higher than previously considered. Therefore, screening with the detection of anti-HDV antibodies is mandatory for all chronic HBV patients. In spite of the severity of liver disease, the only recommended treatment today is pegylated interferon-alpha, which has limited efficacy. Novel host-targeting molecules are now under investigation. The current phase 2 clinical trials include pegylated interferon-lambda, bulevirtide, lonafarnib, and REP-2139. This review focuses on the current status of epidemiology, diagnosis, and treatment of HDV infection.

Molecular Phylogenetics of Hepatitis D Virus in New Zealand and the Implications for Pacific Island Countries

Hepatitis delta virus (HDV) is considered a satellite virus that requires hepatitis B virus surface antigen for infectivity. HDV is endemic in some Pacific Island (PI) countries, including Kiribati and Nauru, with a unique genotype 1, "Pacific clade." The aims of this study were to determine the HDV genotypes in New Zealand and investigate the link of strains to other PI countries and the rest of the world through phylogenetics. Sequencing and phylogenetic analyses were performed on 16 HDV-positive serum samples from 14 individuals collected between 2009 and 2014 at Auckland Hospital. Thirteen of 14 strains were confirmed as genotype 1 and 1 was genotype 5. Eleven of the 13 genotype 1 strains clustered with the Pacific clade. These were isolated from subjects born in Samoa, Kiribati, Tuvalu, and Niue. Another genotype 1 strain isolated from a Maori health-care worker clustered most closely with a European strain. There was an African genotype 1 and genotype 5 from African-born subjects with HIV coinfection. This study supports the probable transmission of HDV Pacific clade around the PI from Micronesia to Polynesia. The data also confirm the need to screen hepatitis B surface antigen-positive individuals for HDV.

Characteristics of Hepatitis B and D Co-infection: A Descriptive Study

: About 5% of cases with chronic hepatitis B virus (HBV) are co-infected with hepatitis D virus (HDV), and this co-infection possesses a high risk for hepatocellular carcinoma (HCC) and cirrhosis. We aimed to evaluate the epidemiological and histopathological characteristics ‎and response to treatment in patients with HBV and HDV co-infection in a hepatitis clinic in Tehran, Iran. In this study, 80 patients were enrolled and evaluated for age, sex, degree of liver fibrosis, virologic status, and response rate. The incidence of co-infection of hepatitis B and D was 4.9% (80/1,631 HBV-infected cases) in our clinic. Thirty-seven (46.25%) patients had liver cirrhosis, and four (5%) patients had HCC. Besides, HDV Ribonucleic Acid (RNA) polymerase chain reaction (PCR) was positive for 31 (38.75 %) patients. Among 30 patients, 14 (46.6%) completed interferon therapy (for equal to or more than 48 weeks) and had a response with undetectable HDV RNA PCR after treatment. According to our results, for cirrhotic patients in HBV/HDV co-infection that was about 46%, it seems that the early detection of HDV antibody (Ab) plays a significant role in the prevention of progressive liver failure, and treatment with interferon can help these patients by improving the prognosis.

Effectiveness of pegylated interferon monotherapy in the treatment of chronic hepatitis D virus infection: A meta-analysis

Chronic HDV infection often is associated with aggressive form of liver disease, compared to chronic HBV mono-infection. However, chronic HDV treatment is challenging because currently there is no approved regimen for affected patients. While standard interferon with/without nucleos(t)ide analogues were reported to be inferior to pegylated interferon (peginterferon) as HDV treatment according to few randomized clinical trials. This meta-analysis will summarize the results of studies on the effectiveness of peginterferon as HDV treatment regimen. An electronic search was performed using PubMed, Cochrane Library, Research Gate, and Medline databases. Studies involving patients who received peginterferon therapy for at least 48 weeks and followed up for 24 weeks post-therapy were included. All analyses were conducted using Review Manager 5.3 designed for Cochrane Reviews. The primary efficacy endpoint was virological response (VR) or HDV-RNA negativity at the end of the follow-up period, whereas secondary efficacy endpoints were biochemical response (BR) or ALT normalization and HBsAg clearance with seroconversion to anti-HBs at the end of follow-up period. Data were abstracted from 13 relevant studies with a total of 475 patients who were treated with peginterferon alpha-2a or -2b. At the end of 24-week post-treatment the pooled VR was achieved in 29% of patients with 95% CI [24%; 34%], BR was reached in 33% of patients [95% CI 27%; 40%] and HBsAg clearance with seroconversion to anti-HBs was achieved in 1% of patients with 95% CI [-0.02; 0.05]. In conclusion, this study showed that peginterferon has limited effectiveness in HDV treatment, since only one-third of chronic HDV patients achieved viral clearance and normalized ALT levels. Morever, HBsAg clearance with seroconversion to anti-HBs has been rarely observed among chronic HDV patients.

Hepatitis B and D in the Pacific Islands of Kiribati

BACKGROUND

Historical reports indicate that hepatitis B and hepatitis D are highly endemic in the Pacific Island of Kiribati but current levels are unknown.

OBJECTIVES

To determine current prevalence of HBV and HDV in Kiribati, characterize the strains in both mono-infection and co-infection and assess individuals for antiviral therapy.

STUDY DESIGN

Sera obtained from 219 patients were screened for HBsAg, HBeAg, HBV DNA, anti-HD, and HDV RNA. 61 HBV isolates were sequenced for genotype, phylogenetic analysis and detection of pre-core and basal core promoter mutations. 82 HDV isolates were also sequenced.

RESULTS

55.7 % HBsAg positive samples had antibodies to HDV and 73.2 % had detectable HDV RNA, indicating that 40.8 % HBsAg-positive individuals had current HBV/HDV co-infection. There were 42 co-infected males and 40 females; the youngest individual was a 4 year-old boy. HBV isolates were genotype D4, and HDV strains formed a distinct Pacific clade of genotype 1. Undetectable HBV DNA loads were statistically more frequent in the co-infected sub-population (p < 0.0001). Basal core promoter and pre-core mutations were present in both mono and co-infection.

CONCLUSION

Kiribati has one of the highest HBV/HDV co-infection rates in the world. The epidemiology of co-infection in this population was unusual with males and females equally represented and the presence of co-infection in a 4 year old child suggesting neonatal or early horizontal transmission, which is extremely rare. Coinfection with HDV resulted in statistically significant suppression of HBV DNA levels. The HDV strain identified in Kiribati was unique to the Pacific Islands.

Hepatitis delta virus interacts with splicing factor SF3B155 and alters pre-mRNA splicing of cell cycle control genes

Hepatitis delta virus (HDV) is the agent responsible for the most severe form of human viral hepatitis. The HDV genome consists of a single-stranded circular RNA molecule that encodes for one single protein, the delta antigen. Given its simplicity, HDV must make use of several host cellular proteins to accomplish its life cycle processes, including transcription, replication, post-transcriptional, and post-translational modifications. Consequently, identification of the interactions established between HDV components and host proteins assumes a pivotal interest in the search of novel therapeutic targets. Here, we used the yeast three-hybrid system to screen a human liver cDNA library to identify host proteins that interact with the HDV genomic RNA. One of the identified proteins corresponded to the splicing factor SF3B155, a component of the U2snRNP complex that is essential for the early recognition of 3' splice sites in the pre-mRNAs of human genes. We show that the interaction between the HDV genomic RNA and SF3B155 occurs in vivo and that the expression of HDV promotes changes in splicing of human genes whose alternative splicing is SF3B155-dependent. We further show that expression of HDV triggers alterations in several constitutive and alternative splicing events in the tumor suppressor RBM5 transcript, with consequent reduction of its protein levels. This is the first description that HDV expression promotes changes in the splicing of human genes, and we suggest that the HDV-induced alternative splicing changes, through SF3B155 sequester, may contribute for the early progression to hepatocellular carcinoma characteristic of HDV-infected patients.

Hepatitis B Virus: Advances in Prevention, Diagnosis, and Therapy

Currently, despite the use of a preventive vaccine for several decades as well as the use of effective and well-tolerated viral suppressive medications since 1998, approximately 250 million people remain infected with the virus that causes hepatitis B worldwide. Hepatitis C virus (HCV) and hepatitis B virus (HBV) are the leading causes of liver cancer and overall mortality globally, surpassing malaria and tuberculosis. Linkage to care is estimated to be very poor both in developing countries and in high-income countries, such as the United States, countries in Western Europe, and Japan. In the United States, by CDC estimates, only one-third of HBV-infected patients or less are aware of their infection. Some reasons for these low rates of surveillance, diagnosis, and treatment include the asymptomatic nature of chronic hepatitis B until the very late stages, a lack of curative therapy with a finite treatment duration, a complex natural history, and a lack of knowledge about the disease by both care providers and patients. In the last 5 years, more attention has been focused on the important topics of HBV screening, diagnosis of HBV infection, and appropriate linkage to care. There have also been rapid clinical developments toward a functional cure of HBV infection, with novel compounds currently being in various phases of progress. Despite this knowledge, many of the professional organizations provide guidelines focused only on specific questions related to the treatment of HBV infection. This focus leaves a gap for care providers on the other HBV-related issues, which include HBV's epidemiological profile, its natural history, how it interacts with other viral hepatitis diseases, treatments, and the areas that still need to be addressed in order to achieve HBV elimination by 2030. Thus, to fill these gaps and provide a more comprehensive and relevant document to regions worldwide, we have taken a global approach by using the findings of global experts on HBV as well as citing major guidelines and their various approaches to addressing HBV and its disease burden.

Advances in Targeting the Innate and Adaptive Immune Systems to Cure Chronic Hepatitis B Virus Infection

“Functional cure” is being pursued as the ultimate endpoint of antiviral treatment in chronic hepatitis B (CHB), which is characterized by loss of HBsAg whether or not anti-HBs antibodies are present. “Functional cure” can be achieved in <10% of CHB patients with currently available therapeutic agents. The dysfunction of specific immune responses to hepatitis B virus (HBV) is considered the major cause of persistent HBV infection. Thus, modulating the host immune system to strengthen specific cellular immune reactions might help eliminate HBV. Strategies are needed to restore/enhance innate immunity and induce HBV-specific adaptive immune responses in a coordinated way. Immune and resident cells express pattern recognition receptors like TLRs and RIG I/MDA5, which play important roles in the induction of innate immunity through sensing of pathogen-associated molecular patterns (PAMPs) and bridging to adaptive immunity for pathogen-specific immune control. TLR/RIG I agonists activate innate immune responses and suppress HBV replication in vitro and in vivo, and are being investigated in clinical trials. On the other hand, HBV-specific immune responses could be induced by therapeutic vaccines, including protein (HBsAg/preS and HBcAg), DNA, and viral vector-based vaccines. More than 50 clinical trials have been performed to assess therapeutic vaccines in CHB treatment, some of which display potential effects. Most recently, using genetic editing technology to generate CAR-T or TCR-T, HBV-specific T cells have been produced to efficiently clear HBV. This review summarizes the progress in basic and clinical research investigating immunomodulatory strategies for curing chronic HBV infection, and critically discusses the rather disappointing results of current clinical trials and future strategies.

Epitranscriptomic marks: Emerging modulators of RNA virus gene expression

Epitranscriptomics, the study of posttranscriptional chemical moieties placed on RNA, has blossomed in recent years. This is due in part to the emergence of high‐throughput detection methods as well as the burst of discoveries showing biological function of select chemical marks. RNA modifications have been shown to affect RNA structure, localization, and functions such as alternative splicing, stabilizing transcripts, nuclear export, cap‐dependent and cap‐independent translation, microRNA biogenesis and binding, RNA degradation, and immune regulation. As such, the deposition of chemical marks on RNA has the unique capability to spatially and temporally regulate gene expression. The goal of this article is to present the exciting convergence of the epitranscriptomic and virology fields, specifically the deposition and biological impact of N7‐methylguanosine, ribose 2′‐O‐methylation, pseudouridine, inosine, N6‐methyladenosine, and 5‐methylcytosine epitranscriptomic marks on gene expression of RNA viruses.

This article is categorized under:

RNA in Disease and Development > RNA in Disease

RNA Interactions with Proteins and Other Molecules > Protein–RNA Interactions: Functional Implications