Hepatitis B surface antigen levels and sequences of natural hepatitis B virus variants influence the assembly and secretion of hepatitis d virus. J Virol. 2008;82:2250-2264. [PMID: 18094179 DOI: 10.1128/jvi.02155-07]

Risk factors associated with hepatitis D virus infection and preventive strategies in Mongolia

BACKGROUND

Hepatitis D virus (HDV) infection is highly prevalent in Mongolia. We aimed to identify the risk factors associated with HDV infection, propose preventive strategies, and evaluate the outcomes of a 3-year collaborative project between Taiwan and Mongolia.

METHODS

In 2016 and 2018, we conducted onsite visits to Mongolia. Mongolian investigators collected questionnaires focusing on risk factors, demographic characteristics, and serum samples for acute HDV infections. Furthermore, 19 Mongolian seed teachers participated in a 1-week workshop on infection control in Taiwan. Subsequently, these seed teachers trained more than 400 medical personnel in Mongolia. To assess secular changes in acute HDV infection, we reviewed the registration data from the National Center for Communicable Disease (NCCD) in Mongolia between 2011 and 2021.

RESULTS

Among the 194 Mongolian patients, 108 had dual infection with hepatitis B virus (HBV) and HDV, while 86 had acute hepatitis B (AHB). Patients with HBV/HDV dual infections were older (28.6 vs 25.5 years, p = 0.030) and had lower rates of positive hepatitis B e antigen in their sera, lower rates of serum HBV DNA exceeding 2000 IU/mL, and higher rates of having received dental treatment (59.4% vs 40.5%, p = 0.014) and injection therapy (64.2% vs 44.0%, p = 0.009) compared with those with AHB. Analysis of NCCD data revealed that new HDV infection cases were more prevalent between 2011 and 2015 (111.20 ± 29.79 cases/y) and decreased to 54.67 ± 27.34 cases/y between 2016 and 2021 ( p = 0.010).

CONCLUSION

Dental treatment and injections were associated with a higher risk of acute HDV infections in Mongolia. Through collaborative efforts, the incidence rate of HDV infection has declined in recent years.

Clinical Implications of HBV PreS/S Mutations and the Effects of PreS2 Deletion on Mitochondria, Liver Fibrosis, and Cancer Development

BACKGROUND AND AIMS

PreS mutants of HBV have been reported to be associated with HCC. We conducted a longitudinal study of the role of HBV preS mutations in the development of HCC, particularly in patients with chronic hepatitis B (CHB) having low HBV DNA or alanine aminotransferase (ALT) levels, and investigated the effects of secretion-defective preS2 deletion mutant (preS2ΔMT) on hepatocyte damage in vitro and liver fibrosis in vivo.

APPROACH AND RESULTS

Association of preS mutations with HCC in 343 patients with CHB was evaluated by a retrospective case-control follow-up study. Effects of preS2ΔMT on HBsAg retention, endoplasmic reticulum (ER) stress, calcium accumulation, mitochondrial dysfunction, and liver fibrosis were examined. Multivariate analysis revealed a significant association of preS mutations with HCC (HR, 3.210; 95% CI, 1.072-9.613; P = 0.037) including cases with low HBV DNA or ALT levels (HR, 2.790; 95% CI, 1.133-6.873; P = 0.026). Antiviral therapy reduced HCC risk, including cases with preS mutations. PreS2ΔMT expression promoted HBsAg retention in the ER and unfolded protein response (UPR). Transmission electron microscopic examination, MitoTracker staining, real-time ATP assay, and calcium staining of preS2ΔMT-expressing cells revealed aberrant ER and mitochondrial ultrastructure, reduction of mitochondrial membrane potential and ATP production, and calcium overload. Serum HBV secretion levels were ~100-fold lower in preS2ΔMT-infected humanized Fah-/-/ Rag2-/-/Il2rg-/- triple knockout mice than in wild-type HBV-infected mice. PreS2ΔMT-infected mice displayed up-regulation of UPR and caspase-3 and enhanced liver fibrosis.

CONCLUSIONS

PreS mutations were significantly associated with HCC development in patients with CHB, including those with low HBV DNA or ALT levels. Antiviral therapy reduced HCC occurrence in patients with CHB, including those with preS mutations. Intracellular accumulation of mutated HBsAg induced or promoted ER stress, calcium overload, mitochondrial dysfunction, impaired energy metabolism, liver fibrosis, and HCC.

Hepatitis delta virus: From infection to new therapeutic strategies

The hepatitis delta virus (HDV) is a small RNA virus that encodes a single protein and which requires the hepatitis B virus (HBV)-encoded hepatitis B surface antigen (HBsAg) for its assembly and transmission. HBV/HDV co-infections exist worldwide and show a higher prevalence among selected groups of HBV-infected populations, specifically intravenous drug users, practitioners of high-risk sexual behaviours, and patients with cirrhosis and hepatocellular carcinoma. The chronic form of HDV-related hepatitis is usually severe and rapidly progressive. Patterns of the viral infection itself, including the status of co-infection or super-infection, virus genotypes (both for HBV and HDV), and persistence of the virus’ replication, influence the outcome of the accompanying and manifested liver disease. Unfortunately, disease severity is burdened by the lack of an effective cure for either virus type. For decades, the main treatment option has been interferon, administered as mono-therapy or in combination with nucleos(t)ide analogues. While its efficacy has been reported for different doses, durations and courses, only a minority of patients achieve a sustained response, which is the foundation of eventual improvement in related liver fibrosis. The need for an efficient therapeutic alternative remains. Research efforts towards this end have led to new treatment options that target specific steps in the HDV life cycle; the most promising among these are myrcludex B, which inhibits virus entry into hepatocytes, lonafarnib, which inhibits farnesylation of the viral-encoded L-HDAg large hepatitis D antigen, and REP-2139, which interferes with HBsAg release and assembly.

First molecular epidemiological study of hepatitis B and D in individuals infected with human T-lymphotropic virus 1/2 from Argentina

Human T-lymphotropic virus 1/2 (HTLV-1/2), hepatitis B virus (HBV), and hepatitis D virus (HDV) share transmission routes. Argentina shows low prevalence of HTLV-1/2, HBV, and HDV infections; however, this situation may vary according to the geographic region and group studied. The aim of this study was to estimate the prevalence of HBV and HDV infections and detect both viral genotypes in HTLV-1/2 individuals from Argentina. A total of 202 HTLV-1/2 confirmed samples (blood donors [BD] and individuals with risk factors for HTLV-1/2 [RF]) were tested for HBsAg and total anti-HBc by enzyme-linked immunosorbent assay. All reactive samples for some HBV markers were analyzed for HBV DNA characterization and HDV serological and molecular analysis. Total prevalence was 1.5% for HBsAg and 6.4% for anti-HBc. Prevalence was 23.1% for anti-HDV in all HBV-reactive samples. No significant difference was observed for HBV and HDV prevalence within HTLV subtypes. The population study showed that prevalence of anti-HBc was higher in the RF than in the BD population, with no significant differences between them. The HBsAg marker and anti-HDV were only found in RF, showing significant differences when compared to BD. Regarding molecular detection, one sample amplified for HBV DNA and none for HDV RNA. HBV sequence was classified as subgenotype F1b. New and updated background on serological markers of HBV and HDV infection in patients with HTLV-1/2 was provided.

The evolution and clinical impact of hepatitis B virus genome diversity

The global burden of hepatitis B virus (HBV) is enormous, with 257 million persons chronically infected, resulting in more than 880,000 deaths per year worldwide. HBV exists as nine different genotypes, which differ in disease progression, natural history and response to therapy. HBV is an ancient virus, with the latest reports greatly expanding the host range of the Hepadnaviridae (to include fish and reptiles) and casting new light on the origins and evolution of this viral family. Although there is an effective preventive vaccine, there is no cure for chronic hepatitis B, largely owing to the persistence of a viral minichromosome that is not targeted by current therapies. HBV persistence is also facilitated through aberrant host immune responses, possibly due to the diverse intra-host viral populations that can respond to host-mounted and therapeutic selection pressures. This Review summarizes current knowledge on the influence of HBV diversity on disease progression and treatment response and the potential effect on new HBV therapies in the pipeline. The mechanisms by which HBV diversity can occur both within the individual host and at a population level are also discussed.

Molecular epidemiology and clinical characteristics of hepatitis delta virus (HDV) infected patients with elevated transaminases in Shanghai, China

BACKGROUND

Patients coinfected with HBV and hepatitis D virus (HDV) have a greater risk of HCC and cirrhosis. The current study was undertaken to assess HDV genotype distribution and determine clinical characteristics of hepatitis delta virus (HDV) among HBsAg positive individuals in Shanghai.

METHOD

This retrospective study involved 225 serum samples from HBsAg positive hospitalized patients from October 2010 to April 2013. HDV-specific RT-nested PCR was used to amplify HDV RNA. HDV genotypes were characterized by Next-generation sequencing (NGS), followed by phylogenetic analyses. HDV/HBV co-infected patients and HBV mono-infected patients were compared clinically and virologically.

RESULTS

Out of the 225 HBsAg-positive serum samples with elevated transaminases, HDV-RNA was identified in 11 (4.9%) patients. The HBV loads in the HDV positive group were significantly lower than the HDV negative HBV-infected patients. The aminotransferase enzymes were significantly higher in HDV/HBV co-infected compared to HDV negative patients (P < 0.05). Phylogenetic analyses indicated that HDV-2 genotype being the predominant genotype, other HDV genotypes were not observed. HDV/HBV patients were significantly associated with a rather unfavourable clinical outcome.

CONCLUSION

In summary, the prevalence of HDV infection in patients with elevated transaminases is not low and the predominance of HDV genotype 2 infection in Shanghai. This finding helps us to better understand the correlation of HDV/HBV co-infection. Moreover, Next-generation sequencing (NGS) technologies provide a rapid, precise method for generating HDV genomes to define infecting genotypes.

Statin inhibits large hepatitis delta antigen-Smad3 -twist-mediated epithelial-to-mesenchymal transition and hepatitis D virus secretion

Background

Hepatitis D virus (HDV) infection may induce fulminant hepatitis in chronic hepatitis B patients (CHB) or rapid progression of CHB to cirrhosis or hepatocellular carcinoma. There is no effective treatment for HDV infection. HDV encodes small delta antigens (S-HDAg) and large delta antigens (L-HDAg). S-HDAg is essential for HDV replication. Prenylated L-HDAg plays a key role in HDV assembly. Previous studies indicate that L-HDAg transactivates transforming growth factor beta (TGF-β) and induces epithelial-mesenchymal transition (EMT), possibly leading to liver fibrosis. However, the mechanism is unclear.

Methods

The mechanisms of the activation of Twist promoter by L-HDAg were investigated by luciferase reporter assay, chromatin immunoprecipitation, and co-immunoprecipitation analysis. ELISA and Western blotting were used to analyze L-HDAg prenylation, TGF-β secretion, expression of EMT markers, and to evaluate efficacy of statins for HDV treatment.

Results

We found that L-HDAg activated Twist expression, TGF-β expression and consequently induced EMT, based on its interaction with Smad3 on Twist promoter. The treatment of statin, a prenylation inhibitor, resulted in reduction of Twist promoter activity, TGF-β expression, and EMT, and reduces the release of HDV virions into the culture medium.

Conclusions

We demonstrate that L-HDAg activates EMT via Twist and TGF-β activation. Treatment with statins suppressed Twist expression, and TGF-β secretion, leading to downregulation of EMT. Our findings clarify the mechanism of HDV-induced EMT, and provide a basis for possible novel therapeutic strategies against HDV infection.

Current knowledge on Hepatitis Delta Virus replication

Hepatitis B Virus (HBV) that infects liver parenchymal cells is responsible for severe liver diseases and co-infection with Hepatitis Delta Virus (HDV) leads to the most aggressive form of viral hepatitis. Even tough being different for their viral genome (relaxed circular partially double stranded DNA for HBV and circular RNA for HDV), HBV and HDV are both maintained as episomes in the nucleus of infected cells and use the cellular machinery for the transcription of their viral RNAs. We propose here an update on the current knowledge on HDV replication cycle that may eventually help to identify new antiviral targets.

A systematic genotype and subgenotype re-ranking of hepatitis B virus under a novel classification standard

Background and aim

It is commonly noticed that chaotic and inefficient subgenotyping are universally used academically and clinically, a standardized HBV genotype/subgenotype classification criterion is urgently acquired. Sequence similarity, which was commonly used for the last three decades, should be upgraded by phylogenetic analysis in genotyping of recombinant-free HBV strains.

Methods

In this study, 4,429 HBV whole-genome sequences were employed to reconstruct the phylogeny of HBV using Bayesian inference. After excluding recombinant sequences, calculating partitioned evolutionary models, excluding recombinant sequences, reconstructing phylogenetic trees, and performing a correlation analysis of genetic distances, geographical distribution and serotypes, we systematically redefined the genotypes and subgenotypes of HBV.

Results

Compared to previous taxonomy, fourteen subgenotypes (A5-A7; B5-B9; C2-C4, C7; and D6-D7) were revised in the new standard. Now the HBV is divided into ten genotypes (A-J) and 24 subgenotypes (A1-A3; B1-B5; C1-C6; D1-D6; and F1-F4).

Conclusion

Our robust genotype/subgenotype new taxonomy has objectively re-molded the current shape of HBV classification. We believe that all future hepatitis B related researches or diagnosis will be benefited under the new HBV genotyping/subgenotyping standards.

The oncogenic role of hepatitis delta virus in hepatocellular carcinoma

Hepatitis delta virus (HDV) is a small defective virus that needs hepatitis B virus (HBV) to replicate and propagate. HDV infection affects 20-40 million people worldwide and pegylated interferon (PegIFN) is the only recommended therapy. There is limited data on the contribution of HDV infection to HBV-related liver disease or liver cancer. Evidence from retrospective and cohort studies suggests that HBV/HDV coinfection accelerates progression to cirrhosis and is associated with an increased risk of hepatocellular carcinoma (HCC) development compared to HBV monoinfection. Although the life cycle of HDV is relatively well known, there is only ancillary information on the molecular mechanisms that can drive specific HDV-related oncogenesis. No thorough reports on the specific landscape of mutations or molecular classes of HDV-related HCC have been published. This information could be critical to better understand the uniqueness, if any, of HDV-related HCC and help identify novel targetable mutations. Herein, we review the evidence supporting an oncogenic role of HDV, the main reported mechanisms of HDV involvement and their impact on HCC development.

A comprehensive bioinformatic analysis of hepatitis D virus full-length genomes

In association with hepatitis B virus (HBV), hepatitis delta virus (HDV) is a subviral agent that may promote severe acute and chronic forms of liver disease. Based on the percentage of nucleotide identity of the genome, HDV was initially classified into three genotypes. However, since 2006, the original classification has been further expanded into eight clades/genotypes. The intergenotype divergence may be as high as 35%-40% over the entire RNA genome, whereas sequence heterogeneity among the isolates of a given genotype is <20%; furthermore, HDV recombinants have been clearly demonstrated. The genetic diversity of HDV is related to the geographic origin of the isolates. This study shows the first comprehensive bioinformatic analysis of the complete available set of HDV sequences, using both nucleotide and protein phylogenies (based on an evolutionary model selection, gamma distribution estimation, tree inference and phylogenetic distance estimation), protein composition analysis and comparison (based on the presence of invariant residues, molecular signatures, amino acid frequencies and mono- and di-amino acid compositional distances), as well as amino acid changes in sequence evolution. Taking into account the congruent and consistent results of both nucleotide and amino acid analyses of GenBank available sequences (recorded as of January, 2017), we propose that the eight hepatitis D virus genotypes may be grouped into three large genogroups fully supported by their shared characteristics.

Molecular characterization of hepatitis B virus in Bangladesh reveals a highly recombinant population

The natural history and treatment outcome of hepatitis B viruses (HBV) infection is largely dependent on genotype, subgenotype, and the presence or absence of virulence associated mutations. We have studied the prevalence of genotype and subgenotype as well as virulence and drug resistance associated mutations and prevalence of recombinant among HBV from Bangladesh. A prospective cross-sectional study was conducted among treatment naïve chronic HBV patients attending at Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh for HBV viral load assessment between June and August 2015. Systematical selected 50% of HBV DNA positive patients (every second patient) were enrolled. Biochemical and serological markers for HBV infection and whole genome sequencing (WGS) was performed on virus positive sample. Genotype, subgenotype, virulence, nucleos(t)ide analogue (NA) resistance (NAr) mutations, and the prevalence of recombinant isolates were determined. Among 114 HBV DNA positive patients, 57 were enrolled in the study and 53 HBV WGS were generated for downstream analysis. Overall, 38% (22/57) and 62% (35/57) of patients had acute and chronic HBV infections, respectively. The prevalence of genotypes A, C, and D was 18.9% (10/53), 45.3% (24/53), and 35.8% (19/53), respectively. Among genotype A, C and D isolates subgenotype A1 (90%; 9/10), C1 (87.5%; 21/24) and D2 (78.9%; 15/19) predominates. The acute infection, virulence associated mutations, and viral load was higher in the genotype D isolates. Evidence of recombination was identified in 22.6% (12/53) of the HBV isolates including 20.0% (2/10), and 16.7% (4/24) and 31.6% (6/19) of genotype A, C and D isolates, respectively. The prevalence of recombination was higher in chronic HVB patients (32.2%; 10/31 versus 9.1%; 2/22); p<0.05. NAr mutations were identified in 47.2% (25/53) of the isolates including 33.9% novel mutations (18/53). HBV genotype C and D predominated in this population in Bangladesh; a comparatively high prevalence of recombinant HBV are circulating in this setting.

Genetic diversity and worldwide distribution of the deltavirus genus: A study of 2,152 clinical strains

Hepatitis delta virus (HDV) is responsible for the most severe form of acute and chronic viral hepatitis. We previously proposed that the Deltavirus genus is composed of eight major clades. However, few sequences were available to confirm this classification. Moreover, little is known about the structural and functional consequences of HDV variability. One practical consequence is the failure of most quantification assays to properly detect or quantify plasmatic HDV RNA. Between 2001 and 2014, 2,152 HDV strains were prospectively collected and genotyped in our reference laboratory by means of nucleotide sequencing and extensive phylogenetic analyses of a 400-nucleotide region of the genome (R0) from nucleotides 889 to 1289 encompassing the 3' end of the delta protein-coding gene. In addition, the full-length genome sequence was generated for 116 strains selected from the different clusters, allowing for in-depth characterization of the HDV genotypes and subgenotypes. This study confirms that the HDV genus is composed of eight genotypes (HDV-1 to HDV-8) defined by an intergenotype similarity >85% or >80%, according to the partial or full-length genome sequence, respectively. Furthermore, genotypes can be segregated into two to four subgenotypes, characterized by an intersubgenotype similarity >90% (>84% for HDV-1) over the whole genome sequence. Systematic analysis of genome and protein sequences revealed highly conserved functional nucleotide and amino acid motifs and positions across all (sub)genotypes, indicating strong conservatory constraints on the structure and function of the genome and the protein.

CONCLUSION

This study provides insight into the genetic diversity of HDV and a clear view of its geographical localization and allows speculation as to the worldwide spread of the virus, very likely from an initial African origin. (Hepatology 2017;66:1826-1841).

Identification of Novel A2/C2 Inter-Genotype Recombinants of Hepatitis B Virus from a Korean Chronic Patient Co-Infected with Both Genotype A2 and C2

Nearly all cases of Hepatitis B virus (HBV) infections in South Korea have the C2 genotype. Here, we have identified a chronically infected patient who was co-infected with HBV of both the A2 and C2 genotypes by screening 135 Korean chronically infected patients using direct sequencing protocols targeting the 1032-bp polymerase reverse transcriptase (RT) region. Further polymerase chain reaction (PCR)-cloning analysis (22 clones) of the RT showed that this patient had genotype C2 (12 clones), genotype A2 (six clones) and A2/C2 inter-genotype HBV recombinants (four clones). BootScan analysis showed that three of the four recombinants have different types of recombination breakpoints in both the RT and overlapping hepatitis B surface antigen (HBsAg) region. Given the significance of HBsAg as a diagnostic or vaccination target against HBV infection, clinical implications of these identified recombinants should be studied in the future. To our knowledge, this is the first report on A2/C2 inter-genotype HBV recombinants.

Transmission of hepatitis D virus between spouses: A longitudinal study of the first reported Canadian case

In chronic hepatitis B (CHB), hepatitis D virus (HDV) superinfection can lead to acute liver failure. The incidence of HDV superinfection is unknown, but is often detected in immigrants from HDV endemic countries. In this report, we characterize long-term clinical and virological outcomes in a hepatitis B virus (HBV) infected carrier before and after HDV superinfection, acquired from their spouse having HBV/HDV co-infection. A 38 year-old Mongolian male with CHB on anti-HBV therapy developed acute liver failure following HDV superinfection. Although he recovered, avoiding the need for liver transplant, HDV serological and molecular markers of infection persisted for the subsequent 16-month follow-up period, suggesting the development of CHB/HDV co-infection. The source of his HDV was from his wife of 10 years, a 34-year old Mongolian female known to have inactive CHB/HDV co-infection but who was not on anti-HBV therapy. Phylogenetic analysis of the complete HDV genome from the couple showed >99% similarity, with post-transmission longitudinal sequence revealing specific nucleotide substitutions between both spouse’s HDV genome sequences. This study highlights the ongoing risk of HDV superinfection due to long-term co-habitation or sexual transmission in CHB patients. The fact that transmission occurred after almost a decade of marriage may be due to host immune or environmental factors that created a more favorable condition for transmission.

Antiviral therapy of hepatitis delta virus infection - progress and challenges towards cure

Hepatitis B-/D-virus co-infection causes the most severe form of viral hepatitis, frequently leading to liver cirrhosis, hepatic decompensation and consecutive liver-related mortality. Treatment options for hepatitis delta are limited. The only recommended therapy is pegylated interferon alpha which leads to virological responses in about 25-30% of patients. However, interferon therapy is associated with frequent side-effects and late HDV RNA relapses have been described during long-term follow even in patients who were HDV RNA negative 24 weeks after the end of therapy. Thus, alternative treatment options are urgently needed. Clinical studies have been performed exploring prenylation inhibitors, viral entry inhibitors and nucleic acid polymers to block particle release. We here summarize the progress and challenges towards cure of HDV infection.

The adventure of delta

The hepatitis D virus (HDV) is unique in animal virology. It has a circular RNA genome that is the smallest of human viruses, requires the HBsAg capsid of the hepatitis B virus to assembly into infectious virions, parasitizes the transcriptional machinery of the host by hijacking cellular RNA polymerases to replicate its RNA genome and is replicated by a rolling circle mechanism unknown to mammalian cells. Hepatitis D is ubiquitous but prevalence varies throughout the world. It is the most severe form of chronic viral liver disorder; carriers of HBsAg superinfected by the HDV are the major victims and the reservoir of the infection. In the last 20 years vaccination against the hepatitis B virus (HBV) has decreased the circulation of HDV in industrialized countries; nevertheless hepatitis D is returning to Western Europe through immigration from HDV endemic areas. Hepatitis D is being rediscovered in the developing world. It has a significant medical impact on areas of Africa, Asia and South America where the partner HBV is not controlled; Pakistan and Mongolia appear to be worldwide the areas with the highest prevalence of the disease. A major obstacle in treatment is that the virus has no replicative function of its own to be targeted by antivirals. Peg-Interferon remains the mainstay of treatment. New strategies are explored to prevent entry of the virion into hepatocytes by blocking the cellular HBsAg receptor or preventing the prenylation process of the large-delta antigen necessary for the assembly of the HDV particle.

Hepatitis B and Delta Virus: Advances on Studies about Interactions between the Two Viruses and the Infected Hepatocyte

The mechanisms determining persistence of hepatitis B virus (HBV) infection and long-term pathogenesis of HBV-associated liver disease appear to be multifactorial. Although viral replication can be efficiently suppressed by the antiviral treatments currently available, viral clearance is generally not achieved since HBV has developed unique replication strategies, enabling persistence of its genome within the infected hepatocytes. Moreover, no direct antiviral therapy exists for the more than 15 million people worldwide that are also coinfected with the hepatitis delta virus (HDV), a defective virus that needs the HBV envelope proteins for propagation. The limited availability of robust HBV and HDV infection systems has hindered the understanding of the complex network of virus-virus and virus-host interactions that are established in the course of infection and slowed down progress in drug development. Since chronic HBV/HDV coinfection leads to the most severe form of chronic viral hepatitis, elucidation of the molecular mechanisms regulating virus-host interplay and pathogenesis are urgently needed. This article summarizes the current knowledge regarding the interactions among HBV, HDV, and the infected target cell and discusses the dependence of HDV on HBV activity and possible future therapeutic approaches.

Hepatitis B virus intergenotypic recombinants worldwide: An overview

Novel variants generated by recombination events between different hepatitis B virus (HBV) genotypes have been increasingly documented worldwide, and the role of recombination in the evolutionary history of HBV is of significant research interest. In the present study, large-scale data retrieval and analysis on HBV intergenotypic recombinant genomes were performed. The geographical distribution of HBV recombinants as well as the molecular processes involved in recombination were examined. After review of published data, a total of 436 complete HBV sequences, previously identified as recombinants, were included in the recombination detection analysis. About 60% of HBV recombinants were B/C (n=179) and C/D (n=83) hybrids. A/B/C, A/C, A/C/G, A/D, A/E, A/G, B/C/U (U=unknown genotype), C/F, C/G, C/J, D/E, D/F, and F/G hybrids were additionally identified. HBV intergenotypic sequences were reported in almost all geographical regions with similar circulation patterns as their original genotypes, indicating the potential for spreading in a wide range of human populations and developing their own epidemiology. Recombination breakpoints were non-randomly distributed in the genome, and specific favored sites detected, such as within nt 1700-2000 and 2100-2300 regions, which displayed a statistically significant difference in comparison with the remaining genome. Elucidation of the effects of recombination events on the evolutionary history of HBV is critical to understand current and future evolution trends.

Changing hepatitis D virus epidemiology in a hepatitis B virus endemic area with a national vaccination program

The emergence of hepatitis D virus (HDV) infection in the era of widespread HBV vaccination has not been described before. We aimed to investigate the changing epidemiology of HDV infection among high- and low-risk populations after an outbreak of human immunodeficiency virus (HIV) infection among injection drug users (IDUs) in Taiwan. A prospective, multicenter, cohort study of 2,562 hepatitis B surface antigen (HBsAg)-positive individuals was conducted to determine the prevalence, genotype, and risk factors of HDV infection from 2001 through 2012. The prevalence rates of HDV infection were 74.9%, 43.9%, 11.4%, 11.1%, and 4.4% among HIV-infected IDUs, HIV-uninfected IDUs, HIV-infected men who have sex with men, HIV-infected heterosexuals, and the general population of HBsAg-positive subjects, respectively. A significant increase in the trend of HDV prevalence from 38.5% to 89.8% was observed in HIV-infected IDUs (odds ratio = 3.06; 95% confidence interval: 1.68-5.56; P = 0.0002). In multivariate analysis, injection drug use, hepatitis C virus infection, HIV infection, serum HBsAg level ≧250 IU/mL, duration of drug use, and older age were significant factors associated with HDV infection. HDV genotype IV (72.2%) was the prevalent genotype circulating among IDUs, whereas genotype II was predominant in the non-IDU populations (73.3%). In the HIV cohort born after 1987 who were HBsAg negative, over half (52.9%) had antibody to hepatitis B surface antigen antibody levels of <10 mIU/mL and there was a significantly higher HBsAg seroprevalence in the HIV cohort, compared to the control group (8.1% vs. 0.0%; P = 0.02).

CONCLUSION

In the era of HBV vaccination, IDUs and HIV-infected individuals have emerged as high-risk groups and a reservoir for HDV infection. Effective strategies are needed to curb the reemerging epidemic of HDV infection in these high-risk groups.

Hepatitis D virus infection, replication and cross-talk with the hepatitis B virus

Viral hepatitis remains a worldwide public health problem. The hepatitis D virus (HDV) must either coinfect or superinfect with the hepatitis B virus (HBV). HDV contains a small RNA genome (approximately 1.7 kb) with a single open reading frame (ORF) and requires HBV supplying surface antigens (HBsAgs) to assemble a new HDV virion. During HDV replication, two isoforms of a delta antigen, a small delta antigen (SDAg) and a large delta antigen (LDAg), are produced from the same ORF of the HDV genome. The SDAg is required for HDV replication, whereas the interaction of LDAg with HBsAgs is crucial for packaging of HDV RNA. Various clinical outcomes of HBV/HDV dual infection have been reported, but the molecular interaction between HBV and HDV is poorly understood, especially regarding how HBV and HDV compete with HBsAgs for assembling virions. In this paper, we review the role of endoplasmic reticulum stress induced by HBsAgs and the molecular pathway involved in their promotion of LDAg nuclear export. Because the nuclear sublocalization and export of LDAg is regulated by posttranslational modifications (PTMs), including acetylation, phosphorylation, and isoprenylation, we also summarize the relationship among HBsAg-induced endoplasmic reticulum stress signaling, LDAg PTMs, and nuclear export mechanisms in this review.

Coinfection of hepatitis B and hepatitis delta virus in Belgium: a multicenter BASL study. Prospective epidemiology and comparison with HBV mono-infection

Epidemiological data on hepatitis delta virus (HDV) infection in Belgium are lacking. A multicenter questionnaire-based registry on HDV infection was collated between March 1, 2008 and February 28, 2009. It consisted of patients coinfected with hepatitis B virus (HBV) and HDV. The data samples were compared to those of a concurrent registry on HBV infection. Prospective data of patients with HBV-HDV coinfection were collected. Active HBV replication is defined as HBeAg positivity or HBV DNA > 2,000 IU/ml. Forty-four patients from 15 centers were registered. A comparison of 29 patients infected with HDV (registered in the concurrent HBV registry) was made against 785 HBV mono-infected patients. The seroprevalence of patients coinfected with HBV and HDV in Belgium is reported to be 3.7% (29/785), consisting solely of the HBV-HDV coinfected patients in the HBV registry. This rises to 5.5% (44/800) if all patients infected with HDV from the two registries combined are included. The patients coinfected with HBV and HDV had higher (P < 0.05) ALT values and more advanced liver disease (Metavir score ≥F2), but had less active HBV replication and lower HBV DNA titers when compared with the patients infected only with HBV. Additionally, the majority of HBV-HDV coinfected patient was male, and 13.6% (6/44) of the patients that were coinfected HBV and HDV were also infected with HCV. In conclusion, this study provided much needed epidemiological data on the current state of HDV infection in Belgium.

Chronic hepatitis D at a standstill: where do we go from here?

Immigration is fuelling a new reservoir of hepatitis D virus (HDV) in Europe, and hepatitis D still represents an important medical problem in the USA. The disease continues to be a major medical scourge in the developing world, in particular in countries such as Pakistan, Mongolia and Mauritania. New therapeutic strategies are being developed to disrupt interactions between HDV and its viral partner HBV, or with the host. Blocking or modifying the hepatitis B surface antigen (HBsAg) might interfere with the uptake or release of the hepatitis D virion; interference with host-mediated post-translational changes of proteins that are crucial to the HDV life cycle, such as prenylation, is another potential therapeutic option. At present, however, the only realistic option is to optimize IFN-α therapy. As eradication of HBsAg is the ultimate end point of therapy, long-term interferon administration might be required, raising an issue of tolerance in patients. Treatment with IFN-λ is a potential alternative approach to IFN-α; treatment of hepatitis C with this cytokine seems to cause fewer adverse effects than IFN-α and, therefore, might be more suitable for long-term treatment of HDV.

Antiviral activity of chemical compound isolated from Artemisia morrisonensis against hepatitis B virus in vitro

The compound p-hydroxyacetophenone (PHAP) isolated from Artemisia morrisonensis was found to have potential anti-HBV effects in HepG2 2.2.15 cells. We clarified its antiviral mode further and HBV-transfected Huh7 cells were used as the platform. During viral gene expression, treatment with PHAP had no apparent effects on the viral precore/pregenomic RNA. However, the 2.4-kb preS RNA of viral surface gene increased significantly relative to the 2.1-kb S RNA with PHAP. Promoter activity analysis demonstrated that PHAP had a potent effect on augmenting the viral preS promoter activity. The subsequent increase in the large surface protein and induce endoplasmic reticular (ER) stress has been reported previously. Interestingly, PHAP specifically reduced ER stress related GRP78 RNA/protein levels, but not those of GRP94, in treated Huh7 cells while PHAP also led to the significant intracellular accumulation of virus. Moreover, treatment with the ER chaperone inducer thapsigargin relieved the inhibitory effect of PHAP based on the supernatant HBV DNA levels of HBV-expressed cells. In conclusion, this study suggests that the mechanism of HBV inhibition by PHAP might involve the regulation of viral surface gene expression and block virion secretion by interference with the ER stress signaling pathway.

Hepatitis D virus isolates with low replication and epithelial-mesenchymal transition-inducing activity are associated with disease remission

Clearance of hepatitis D virus (HDV) viremia leads to disease remission. Large hepatitis delta antigen (L-HDAg) has been reported to activate transforming growth factor β, which may induce epithelial-mesenchymal transition (EMT) and fibrogenesis. This study analyzed serum HDV RNA "quasispecies" in HDV-infected patients at two stages of infection: before and after alanine aminotransferase (ALT) elevations. Included in the study were four patients who went into remission after ALT elevation and three patients who did not go into remission and progressed to cirrhosis or hepatocellular carcinoma. Full-length HDV cDNA clones were obtained from the most abundant HDV RNA species at the pre- and post-ALT elevation stages. Using an in vitro model consisting of Huh-7 cells transfected with cloned HDV cDNAs, the pre- or post-ALT elevation dominant HDV RNA species were characterized for (i) their replication capacity by measuring HDV RNA and HDAg levels in transfected cells and (ii) their capacity to induce EMT by measuring the levels of the mesenchymal-cell-specific protein vimentin, the EMT regulators twist and snail, and the epithelial-cell-specific protein E-cadherin. Results show that in patients in remission, the post-ALT elevation dominant HDV RNA species had a lower replication capacity in vitro and lower EMT activity than their pre-ALT elevation counterparts. This was not true of patients who did not go into remission. The expression of L-HDAg, but not small HDAg, increased the expression of the EMT-related proteins. It is concluded that in chronically infected patients, HDV quasispecies with a low replication capacity and low EMT activity are associated with disease remission.

Identification of novel inter-genotypic recombinants of human hepatitis B viruses by large-scale phylogenetic analysis

Recombination plays an important role in the evolutionary history of Hepatitis B virus (HBV). We performed a phylogenetic analysis of 3403 full-length HBV genome sequences isolated from humans to define the genotype. The genome sequences were divided into 13 sub-datasets, each approximately 250 bp in length. Genotype designations obtained from the sub-datasets that differed from the genotype defined by the whole genome were assigned as putative recombinants. Our results showed that 3379 out of 3403 sequences belonged to the previously described and putative genotypes A to J respectively, with 315 sequences defined in this analysis. The remaining 24 viruses had sequence divergence of less than 8% with both genotypes B and C and were provisionally assigned genotype "BC". 1047 out of 3403 sequences were identified to be putative recombinants, of which 72 were identified to be novel recombinants. Notably, all viruses of the herein described genotype "BC" were identified to be B/C recombinants.

Hepatitis delta virus

Hepatitis delta virus (HDV) is a small, defective RNA virus that can infect only individuals who have hepatitis B virus (HBV); worldwide more than 15 million people are co-infected. There are eight reported genotypes of HDV with unexplained variations in their geographical distribution and pathogenicity. The hepatitis D virion is composed of a coat of HBV envelope proteins surrounding the nucleocapsid, which consists of a single-stranded, circular RNA genome complexed with delta antigen, the viral protein. HDV is clinically important because although it suppresses HBV replication, it causes severe liver disease with rapid progression to cirrhosis and hepatic decompensation. The range of clinical presentation is wide, varying from mild disease to fulminant liver failure. The prevalence of HDV is declining in some endemic areas but increasing in northern and central Europe because of immigration. Treatment of HDV is with pegylated interferon alfa; however, response rates are poor. Increased understanding of the molecular virology of HDV will identify novel therapeutic targets for this most severe form of chronic viral hepatitis.

Replicative and transcriptional activities of hepatitis B virus in patients coinfected with hepatitis B and hepatitis delta viruses

Hepatitis B virus (HBV) and hepatitis delta virus (HDV) interplay was investigated by examining liver and serum samples from 21 coinfected and 22 HBV-monoinfected patients with chronic liver disease. Different real-time PCR assays were applied to evaluate intrahepatic amounts of HBV DNA, covalently closed circular DNA (cccDNA), pregenomic RNA (pgRNA), pre-S/S RNAs, and HDV RNA. Besides HBV DNA and HDV RNA levels, HBsAg concentrations in the sera were also determined. HDV-coinfected cases showed significantly lower median levels of serum HBV DNA (-5 log), intrahepatic relaxed-circular DNA (-2 log), and cccDNA (-2 log) than those of HBV-monoinfected cases. Interestingly, pgRNA and pre-S/S RNA amounts were significantly lower (both -1 log) in HDV-positive patients, whereas serum HBsAg concentrations were comparable between the two patient groups. Pre-S/S RNA and HBsAg amounts per cccDNA molecule were higher in HDV-positive patients (3-fold and 1 log, respectively), showing that HBV replication was reduced, whereas synthesis of envelope proteins was not specifically decreased. The ratios of cccDNA to intracellular total HBV DNA showed a larger proportion of cccDNA molecules in HDV-positive cases. For these patients, both intrahepatic and serum HDV RNA amounts were associated with cccDNA but not with HBsAg or HBV DNA levels. Finally, HBV genomes with large deletions in the basal core promoter/precore region were detected in 5/21 HDV-positive patients but in no HDV-negative patients and were associated with lower viremia levels. These findings provide significant information about the interference exerted by HDV on HBV replication and transcription activities in the human liver.

Virological and clinical characteristics of delta hepatitis in Central Europe

Hepatitis D virus (HDV) or delta hepatitis has mainly been studied in Asian and Mediterranean cohorts, but data on virological and clinical characteristics of HDV-infected Central and Northern European patients are limited. We investigated virological patterns, as well as biochemical and clinical features of liver disease in 258 HDV infected patients recruited over a period of 15 years at Hannover Medical School. Virological parameters were compared to 2083 anti-HDV negative hepatitis B surface antigen (HBsAg) positive individuals. In this cohort, (i) HDV infection was associated with both suppressed hepatitis B virus (HBV) and hepatitis C virus (HCV) replication, (ii) the suppression of HBV-DNA and HCV-RNA was not related to HDV-RNA replication, (iii) mean HBsAg levels did not significantly differ between HBV-monoinfected patients and individuals with delta hepatitis, (iv) HCV coinfection was rather frequent as about one third of our delta hepatitis patients tested anti-HCV positive, however, without being associated with more advanced liver disease, (v) delta hepatitis patients presented in a high frequency with an advanced stage of liver disease, and (vi) the course of delta hepatitis did not differ between Turkish-born, Eastern European (EE)-born and German-born patients. In summary, in this cohort of patients which is the largest so far Central European single centre group of delta hepatitis patients, we confirm the presence of frequently severe disease and describe novel virological profiles which require consideration in the management of this difficult to treat group of patients.

Pro-205 of large hepatitis delta antigen and Pro-62 of major hepatitis B surface antigen influence the assembly of different genotypes of hepatitis D virus

Hepatitis B surface antigen (HBsAg) is essential for the assembly and infection of hepatitis D virus (HDV). The assembly efficiency of genotype 1 HDV is higher than that of genotype 2, whilst the P62L substitution of major HBsAg further compromises the assembly of genotype 2 and 4 HDV. This study investigated the influence of proline residues in the carboxyl end of the large hepatitis delta antigen (HDAg-L) on the assembly of HDV of different genotypes. Expression vectors containing the HDAg-L gene or full-length HDV genome of genotype 1, 2 or 4 were co-transfected with plasmids expressing HBsAg proteins that bore either proline or leucine residues at position 62. Of the eight HDV genotypes, only genotype 1 has Pro-205 in HDAg-L, whereas genotypes 2 and 4 have Arg-205. The Arg-205 to Pro-205 substitution in HDV-2 and -4 markedly increased the assembly efficiencies of HDAg-L and whole HDV genomes, even in the presence of HBsAg with Leu-62. In contrast, secretion of genotype 1 HDV or HDAg-L was reduced significantly when arginine or alanine replaced Pro-205. When HBsAg contained Pro-62, the influence of Pro-205 on assembly decreased. In conclusion, both Pro-205 of the HDAg-L and Pro-62 of the major HBsAg play critical roles in the assembly of HDV of different genotypes. The presence of Pro-205 in genotype 1 HDV may account for its higher assembly efficiencies and wider distribution.

Increased ATP generation in the host cell is required for efficient vaccinia virus production

To search for cellular genes up-regulated by vaccinia virus (VV) infection, differential display-reverse transcription-polymerase chain reaction (ddRT-PCR) assays were used to examine the expression of mRNAs from mock-infected and VV-infected HeLa cells. Two mitochondrial genes for proteins that are part of the electron transport chain that generates ATP, ND4 and CO II, were up-regulated after VV infection. Up-regulation of ND4 level by VV infection was confirmed by Western blotting analysis. Up-regulation of ND4 was reduced by the MAPK inhibitor, apigenin, which has been demonstrated elsewhere to inhibit VV replication. The induction of ND4 expression occurred after viral DNA replication since ara C, an inhibitor of poxviral DNA replication, could block this induction. ATP production was increased in the host cells after VV infection. Moreover, 4.5 μM oligomycin, an inhibitor of ATP production, reduced the ATP level 13 hr after virus infection to that of mock-infected cells and inhibited viral protein expression and virus production, suggesting that increased ATP production is required for efficient VV production. Our results further suggest that induction of ND4 expression is through a Bcl-2 independent pathway.

Hepatitis B virus and hepatitis delta virus genotypes in outbreaks of fulminant hepatitis (Labrea black fever) in the western Brazilian Amazon region

The genotypes of hepatitis B (HBV) and delta (HDV) viruses circulating among fulminant hepatitis cases from the western Amazon Basin of Brazil were characterized in this study. HBV and HDV isolates were obtained from liver samples from 14 patients who developed fulminant hepatitis and died during 1978-1989. HBV DNA and HDV RNA were detected in all samples. Phylogenetic analyses of HDV sequences showed that they all clustered with previously characterized sequences of HDV genotype 3 (HDV-3). HBV genotypes F, A and D were found in 50.0, 28.6 and 21.4 % of cases, respectively. These results confirm the predominance of HDV-3 in South America and its association with the severe form of hepatitis, and the finding of the co-infection of HDV-3 with different genotypes of HBV suggests that the association between HDV-3 and HBV-F is not necessarily causally related to a more severe clinical course of infection.

Hepatitis D: thirty years after

The key to the discovery of the Hepatitis D Virus (HDV) was the description in Turin, Italy in the mid-1970s of the delta antigen and antibody in carriers of the hepatitis B surface antigen. The new antigen was first thought to be a marker of the Hepatitis B Virus (HBV) and in view of its intricate true nature, it would have possibly died away as another odd antigenic subtype of HBV, like many that were described in the 1970s. Fortunately, instead, a collaboration started in 1978 between the Turin group, and the National Institute of Health and Georgetown University in the US. With American facilities and expertise this collaboration led just a year later, in 1979, to the unfolding of an unexpected and amazing chapter in virology. Experiments in chimpanzees demonstrated that the delta antigen was not a component of the HBV but of a separate defective virus requiring HBV for its infection; it was named the hepatitis D virus to conform to the nomenclature of hepatitis viruses and classified within the genus Deltavirus. The animal experiments were also seminal in proposing to future clinical interpretation, the paradigm of a pathogenic infection (hepatitis D), that could develop only in HBV-infected patients, was mainly transmitted by superinfection of HDV on chronic HBV carriers and had the ability to strongly inhibit the helper HBV. The discovery of the HDV has driven three directions of further research: (1) The understanding of the replicative and infectious mechanisms of the HDV. (2) The assessment of its epidemiological and medical impact. (3) The search for a therapy for chronic hepatitis D (CHD). This review summarizes the progress achieved in each field of research in the thirty years that have passed since the discovery of HDV.