Hepatitis Delta Virus: Replication Strategy and Upcoming Therapeutic Options for a Neglected Human Pathogen

An hepatitis B and D virus infection model using human pluripotent stem cell-derived hepatocytes

Current culture systems available for studying hepatitis D virus (HDV) are suboptimal. In this study, we demonstrate that hepatocyte-like cells (HLCs) derived from human pluripotent stem cells (hPSCs) are fully permissive to HDV infection across various tested genotypes. When co-infected with the helper hepatitis B virus (HBV) or transduced to express the HBV envelope protein HBsAg, HLCs effectively release infectious progeny virions. We also show that HBsAg-expressing HLCs support the extracellular spread of HDV, thus providing a valuable platform for testing available anti-HDV regimens. By challenging the cells along the differentiation with HDV infection, we have identified CD63 as a potential HDV co-entry factor that was rate-limiting for HDV infection in immature hepatocytes. Given their renewable source and the potential to derive hPSCs from individual patients, we propose HLCs as a promising model for investigating HDV biology. Our findings offer new insights into HDV infection and expand the repertoire of research tools available for the development of therapeutic interventions.

In vitro cell culture models to study hepatitis B and D virus infection

Chronic infection with the hepatitis B virus (HBV) and hepatitis D virus (HDV) can cause a major global health burden. Current medication regimens can repress viral replication and help to control disease progression, but a complete cure is hardly achieved due to the difficulties to eradicate viral templates (cccDNA and integrates). To develop novel curative antiviral therapies for HBV/HDV infection, it is vital to precisely understand the details of the molecular biology of both viruses and the virus-host interactions. One important prerequisite for gaining this aim is the availability of suitable in vitro models that support HBV/HDV infection, replicate both viruses via their authentic template and allow to adequately study host cell responses. The discovery of sodium taurocholate cotransporting polypeptide (NTCP) receptor as the most crucial host factor promoted HBV/HDV research to a new era. Recently, the structure of human NTCP was solved, gaining a deeper understanding of HBV recognition as the bona fide receptor. After decades of continuous efforts, new progress has been achieved in the development of cell culture models supporting HBV/HDV study. This review summarizes the cell culture models currently available, discusses the advantages and disadvantages of each model, and highlights their future applications in HBV and HDV research.

Trends and spatial distribution of Hepatitis D in the North of Brazil, 2009-2018: an ecological study

OBJECTIVE

To analyze the annual incidence of hepatitis D cases in both Brazil and the Brazilian Northern region between 2009 and 2018.

METHODS

This was an ecological study of hepatitis cases notified on the Notifiable Health Conditions Information System (SINAN), analyzed by sex, age groups, and Northern region states. Temporal trend analysis was performed using the Prais-Winsten method to estimate incident rate annual percent change (APC).

RESULTS

In the period studied, 2,710 cases were reported in Brazil, 74.5% of them in the Northern region and 71.5% in Amazonas, Acre and Rondonia alone. APC showed a downward trend in Brazil as a whole (-21.6% - 95%CI -3.8;-36.2%), in the Northern region (-28.5% - 95%CI -5.2;-46.1%,), in Amazonas (-34.1% - 95%CI -0.8;-56.2%) and in Acre (-37.6% - 95%CI -18.0;-52.6%). Cases decreased in age groups below 40 years old.

CONCLUSION

There was a downward trend in incidence in the Western Amazon, impacting incidence in Brazil as a whole. This fall was led by younger people, probably due to hepatitis B vaccination.

Analyses of viral genomes for G-quadruplex forming sequences reveal their correlation with the type of infection

G-quadruplexes contribute to the regulation of key molecular processes. Their utilization for antiviral therapy is an emerging field of contemporary research. Here we present comprehensive analyses of the presence and localization of putative G-quadruplex forming sequences (PQS) in all viral genomes currently available in the NCBI database (including subviral agents). The G4Hunter algorithm was applied to a pool of 11,000 accessible viral genomes representing 350 Mbp in total. PQS frequencies differ across evolutionary groups of viruses, and are enriched in repeats, replication origins, 5'UTRs and 3'UTRs. Importantly, PQS presence and localization is connected to viral lifecycles and corresponds to the type of viral infection rather than to nucleic acid type; while viruses routinely causing persistent infections in Metazoa hosts are enriched for PQS, viruses causing acute infections are significantly depleted for PQS. The unique localization of PQS identifies the importance of G-quadruplex-based regulation of viral replication and life cycle, providing a tool for potential therapeutic targeting.

Forty-Five Years after the Discovery of the Hepatitis D Virus: Where Do We Stand?

The discovery of the Australia Antigen in the mid-1960s led, in a few years, to the identification of the virus of Hepatitis B [...].

New insights into HDV persistence: The role of interferon response and implications for upcoming novel therapies

Chronic hepatitis D (CHD), a global health problem, manifests as the most severe form of viral hepatitis. The causative agent, HDV, is the smallest known human virus; it replicates its circular single-stranded RNA genome in the nucleus of hepatocytes. HDV requires HBV-encoded envelope proteins for dissemination and de novo cell entry. However, HDV can also spread through cell division. Following entry into hepatocytes, replicative intermediates of HDV RNA are sensed by the pattern recognition receptor MDA5 (melanoma differentiation antigen 5) resulting in interferon (IFN)-β/λ induction. This IFN response strongly suppresses cell division-mediated spread of HDV genomes, however, it only marginally affects HDV RNA replication in already infected, resting hepatocytes. Monotherapy with IFN-α/λ shows efficacy but rarely results in HDV clearance. Recent molecular insights into key determinants of HDV persistence and the accelerated development of specifically acting antivirals that interfere with the replication cycle have revealed promising new therapeutic perspectives. In this review, we briefly summarise our knowledge on replication/persistence of HDV, the newly discovered HDV-like agents, and the interplay of HDV with the IFN response and its consequences for persistence. Finally, we discuss the possible role of IFNs in combination with upcoming therapies aimed at HDV cure.

Interplay between Hepatitis D Virus and the Interferon Response

Chronic hepatitis D (CHD) is the most severe form of viral hepatitis, with rapid progression of liver-related diseases and high rates of development of hepatocellular carcinoma. The causative agent, hepatitis D virus (HDV), contains a small (approximately 1.7 kb) highly self-pairing single-strand circular RNA genome that assembles with the HDV antigen to form a ribonucleoprotein (RNP) complex. HDV depends on hepatitis B virus (HBV) envelope proteins for envelopment and de novo hepatocyte entry; however, its intracellular RNA replication is autonomous. In addition, HDV can amplify HBV independently through cell division. Cellular innate immune responses, mainly interferon (IFN) response, are crucial for controlling invading viruses, while viruses counteract these responses to favor their propagation. In contrast to HBV, HDV activates profound IFN response through the melanoma differentiation antigen 5 (MDA5) pathway. This cellular response efficiently suppresses cell-division-mediated HDV spread and, to some extent, early stages of HDV de novo infection, but only marginally impairs RNA replication in resting hepatocytes. In this review, we summarize the current knowledge on HDV structure, replication, and persistence and subsequently focus on the interplay between HDV and IFN response, including IFN activation, sensing, antiviral effects, and viral countermeasures. Finally, we discuss crosstalk with HBV.

Host transcriptome-guided drug repurposing for COVID-19 treatment: a meta-analysis based approach

BACKGROUND

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been declared a pandemic by the World Health Organization, and the identification of effective therapeutic strategy is a need of the hour to combat SARS-CoV-2 infection. In this scenario, the drug repurposing approach is widely used for the rapid identification of potential drugs against SARS-CoV-2, considering viral and host factors.

METHODS

We adopted a host transcriptome-based drug repurposing strategy utilizing the publicly available high throughput gene expression data on SARS-CoV-2 and other respiratory infection viruses. Based on the consistency in expression status of host factors in different cell types and previous evidence reported in the literature, pro-viral factors of SARS-CoV-2 identified and subject to drug repurposing analysis based on DrugBank and Connectivity Map (CMap) using the web tool, CLUE.

RESULTS

The upregulated pro-viral factors such as TYMP, PTGS2, C1S, CFB, IFI44, XAF1, CXCL2, and CXCL3 were identified in early infection models of SARS-CoV-2. By further analysis of the drug-perturbed expression profiles in the connectivity map, 27 drugs that can reverse the expression of pro-viral factors were identified, and importantly, twelve of them reported to have anti-viral activity. The direct inhibition of the PTGS2 gene product can be considered as another therapeutic strategy for SARS-CoV-2 infection and could suggest six approved PTGS2 inhibitor drugs for the treatment of COVID-19. The computational study could propose candidate repurposable drugs against COVID-19, and further experimental studies are required for validation.

HDVdb: A Comprehensive Hepatitis D Virus Database

Hepatitis D virus (HDV) causes the most severe form of viral hepatitis, which may rapidly progress to liver cirrhosis and hepatocellular carcinoma (HCC). It has been estimated that 15-20 million people worldwide are suffering from the chronic HDV infection. Currently, no effective therapies are available to treat acute or chronic HDV infection. The remarkable sequence variability of the HDV genome, particularly within the hypervariable region has resulted in the provisional classification of eight major genotypes and various subtypes. We have developed a specialized database, HDVdb (http://hdvdb.bio.wzw.tum.de/), which contains a collection of partial and complete HDV genomic sequences obtained from the GenBank and from our own patient cohort. HDVdb enables the researchers to investigate the genetic variability of all available HDV sequences, correlation of genotypes to epidemiology and pathogenesis. Additionally, it will contribute in understanding the drug resistant mutations and develop effective vaccines against HDV infection. The database can be accessed through a web interface that allows for static and dynamic queries and offers integrated generic and specialized sequence analysis tools, such as annotation, genotyping, primer prediction, and phylogenetic analyses.

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.

High rates of cirrhosis and severe clinical events in patients with HBV/HDV co-infection: longitudinal analysis of a German cohort

Background

Chronic hepatitis delta virus (HDV) infection causes severe liver disease which often leads to cirrhosis and hepatocellular carcinoma (HCC). Aim of this study was to establish the disease severity and prognostic factors for disease outcome by analysing frequencies of clinical events and their correlation with baseline virological and biochemical parameters as well as interferon and nucleos(t)ide analogue treatment choice.

Methods

We studied a single-centre cohort of 49 anti-HDAg-positive patients with HBsAg persistence for at least 6 months. Virological and biochemical parameters, interferon and nucleos(t)ide analogue treatment choice as well as clinical events during follow-up were analysed by retrospective chart review (mean follow-up time 3 years, range 0.25–7.67 years).

Results

Severe clinical events occurred in 11/49 hepatitis D patients, including HCC (8/49), death (8/49) or liver transplantation (2/49). HCCs only occurred secondary to liver cirrhosis and their event rates in this cohort of hepatitis D patients did not differ from a matched HBV mono-infected cohort with comparable frequency of liver cirrhosis. A stepwise multivariate logistic regression revealed low platelet count (p = 0. 0290) and older age (p = 0.0337) correlating most strongly with overall clinical events, while serum HDV RNA positivity at baseline did not correlate with any clinical outcome. Interferon-free but not nucleos(t)ide analogue-free patient care correlated with the occurrence of HCC at logistic regression, although only 3/18 interferon-treated patients demonstrated repeatedly negative HDV PCR results post therapy.

Conclusions

Our data indicate that progressive liver disease at baseline plays a major role as predictive factor for overall clinical outcome of hepatitis D patients. In particular, HCC risk may not be underestimated in hepatitis D virus RNA negative hepatitis D patients with advanced liver fibrosis.

Strategies to eliminate HBV infection: an update

Chronic hepatitis B (CHB) is a widespread global infection and a leading cause of hepatocellular carcinoma and liver failure. Current approaches to treat CHB involve the suppression of viral replication with either interferon or nucleos(t)ide analog therapy, but neither of these approaches can reliably induce viral eradication, immunologic control or long-lived viral suppression in the absence of continued therapy. In this update, we explore the major obstacles of CHB cure and review new therapeutic strategies and drug candidates.

Phylodynamic and Phylogeographic Analysis of Hepatitis Delta Virus Genotype 3 Isolated in South America

The hepatitis delta virus (HDV) is a globally distributed agent, and its genetic variability allows for it to be organized into eight genotypes with different geographic distributions. In South America, genotype 3 (HDV-3) is frequently isolated and responsible for the most severe form of infection. The objective of this study was to evaluate the evolutionary and epidemiological dynamics of HDV-3 over the years and to describe its distribution throughout this continent in an evolutionary perspective. While using Bayesian analysis, with strains being deposited in the Nucleotide database, the most recent common ancestor was dated back to 1964 and phylogenetic analysis indicated that the dispersion may have started in Brazil, spreading to Venezuela and then to Colombia, respectively. Exponential growth in the effective number of infections was observed between the 1950s and 1970s, years after the first report of the presence of HDV on the continent, during the Labrea Black Fever outbreak, which showed that the virus continued to spread, increasing the number of cases decades after the first reports. Subsequently, the analysis showed a decrease in the epidemiological levels of HDV, which was probably due to the implantation of the vaccine against its helper virus, hepatitis B virus, and serological screening methods implemented in the blood banks.

Excellent safety and effectiveness of high-dose myrcludex-B monotherapy administered for 48 weeks in HDV-related compensated cirrhosis: A case report of 3 patients

Short-term administration of the entry inhibitor myrcludex-B (MyrB) has been shown to be safe and effective in phase II studies in patients coinfected with hepatitis B virus (HBV) and hepatitis delta virus (HDV). However, its effectiveness and safety are unknown during long-term and high-dose treatment of patients with compensated cirrhosis in real-life settings. Herein, we describe the first 3 European patients with HDV-related compensated cirrhosis who were treated with MyrB 10 mg/day for 48 weeks as a compassionate therapy. Liver function tests, bile acids, and virological markers were monitored every 4 weeks. HBV/HDV-specific T cell quantity (up to 48 and 36 weeks) and HBV RNA levels were also assessed in 2 cases. During MyrB treatment, HDV RNA levels progressively declined from 4.4 and 5.6 logs IU/ml to undetectability in 2 cases, and from 6.8 log copies/ml to 500 copies/ml for the other patient. Alanine aminotransferase normalised after 20, 12 and 28 weeks, respectively. A significant improvement in features of portal hypertension, liver function tests and alpha-fetoprotein levels were documented in 2 cases. In the male patient with histological and clinical stigmata of autoimmune hepatitis, IgG and immunoglobulins rapidly normalised. No significant changes in HBV surface antigen levels and circulating HBV/HDV-specific T cells were demonstrated; HBV DNA and HBV RNA levels remained undetectable throughout the study period. MyrB was well tolerated; patients remained fully asymptomatic despite a significant increase of bile acids. In conclusion, this report shows excellent safety and effectiveness of a 48-week course of MyrB 10 mg/day, combined with tenofovir disoproxil fumarate, for the treatment of HDV-related compensated cirrhosis.

Prevalence of hepatitis delta infections among HBs-antigen-positive inhabitants of southeastern and northwestern parts of Poland

Hepatitis delta (HDV) virus still poses a serious health problem worldwide. Being a satellite particle, it may complete its life cycle only in the presence of HBs antigen produced by hepatitis B virus (HBV). According to epidemiological data, about 5% of HBs antigen carriers are infected with this virus, which equates to approximately 15-20 million individuals worldwide. Although the infection with both HBV and HDV viruses is considered to be the worst form of viral hepatitis, the only approved treatment, with pegylated interferon α, is not satisfactory. Thus effective and safe therapy is still lacking, which stands in contrast to the latest development in therapeutic areas of HBV and hepatitis C virus (HCV) infections. As the exact data on prevalence of this infection in some countries as well as natural history of this disease are still incomplete, further studies are warranted. Polish investigations on this field are very scarce and at most dating from the 1990s. This publication makes another attempt to broaden our knowledge of this temporarily forgotten but still ongoing and complex problem.

Infectious Disease Transmission in Solid Organ Transplantation: Donor Evaluation, Recipient Risk, and Outcomes of Transmission

In 2016, the Transplantation Society of Australia and New Zealand, with the support of the Australian Government Organ and Tissue authority, commissioned a literature review on the topic of infectious disease transmission from deceased donors to recipients of solid organ transplants. The purpose of this review was to synthesize evidence on transmission risks, diagnostic test characteristics, and recipient management to inform best-practice clinical guidelines. The final review, presented as a special supplement in Transplantation Direct, collates case reports of transmission events and other peer-reviewed literature, and summarizes current (as of June 2017) international guidelines on donor screening and recipient management. Of particular interest at the time of writing was how to maximize utilization of donors at increased risk for transmission of human immunodeficiency virus, hepatitis C virus, and hepatitis B virus, given the recent developments, including the availability of direct-acting antivirals for hepatitis C virus and improvements in donor screening technologies. The review also covers emerging risks associated with recent epidemics (eg, Zika virus) and the risk of transmission of nonendemic pathogens related to donor travel history or country of origin. Lastly, the implications for recipient consent of expanded utilization of donors at increased risk of blood-borne viral disease transmission are considered.

Upregulation of HBV transcription by sodium taurocholate cotransporting polypeptide at the postentry step is inhibited by the entry inhibitor Myrcludex B

Sodium taurocholate cotransporting polypeptide (NTCP) is a functional receptor for hepatitis B virus (HBV) entry. However, little is known regarding whether NTCP is involved in regulating the postentry steps of the HBV life cycle. Here, we found that NTCP expression upregulated HBV transcription at the postentry step and that the NTCP-targeting entry inhibitor Myrcludex B (MyrB) effectively suppressed HBV transcription both in an HBV in vitro infection system and in mice hydrodynamically injected with an HBV expression plasmid. Mechanistically, NTCP upregulated HBV transcription via farnesoid X receptor α (FxRα)-mediated activation of the HBV EN2/core promoter at the postentry step in a manner that was dependent on the bile acid (BA)-transport function of NTCP, which was blocked by MyrB. Our findings uncover a novel role for NTCP in the HBV life cycle and provide a reference for the use of novel NTCP-targeting entry inhibitors to suppress HBV infection and replication.

[Hepatitis delta virus replication and the role of the small hepatitis delta protein S-HDAg]

Hepatitis delta virus (HDV) is a mammalian defective virus. Its genome is a small single-stranded circular RNA of approximately 1,680 nucleotides. To spread, HDV relies on hepatitis B virus envelope proteins that are needed for viral particle assembly and egress. Severe clinical features of HBV-HDV infection include acute fulminant hepatitis and chronic liver fibrosis leading to cirrhosis and hepatocellular carcinoma. One uniqueness of HDV relies on its genome similarity to viroids, small plant infectious uncoated RNAs. Devoid of viral replicase activity, HDV has to use host DNA-dependant RNA Pol II to replicate its genomic RNA. Thus, one can ask how does this replication occur? We describe first here the major steps of the viral RNA transcription and replication and then we detail the role of the Small HD protein in these processes, especially with regard to the Pol II recruitment.

Screening for hepatitis D and PEG-Interferon over Tenofovir enhance general hepatitis control efforts in Brazil

Background

Hepatitis D virus (HDV), which requires the presence of hepatitis B virus (HBV), is a deadly yet neglected disease that rapidly leads to liver cancer and disease-induced mortality. This co-dependence creates complex transmission dynamics that make it difficult to predict the efficacy of interventions aimed at HBV and/or HDV control in endemic regions, such as certain municipalities of Brazil, where up to 65% of HBV-infected persons are co-infected.

Methodology

We created a mathematical model that captures the joint transmission dynamics of HBV and HDV, incorporating mother-to-child, sexual and household transmission. With an aim to minimize the number of total infections and disease-induced mortality in 2027, we then determined optimal strategies for Brazil and its sub-regions under a constrained budget, which was dynamically allocated among HBV and HDV screening, HBV and HDV treatment, HBV newborn and adult vaccination, and awareness programs. Three treatment options were considered, namely: Tenofovir, PEGylated-Interferon, and nucleic acid polymers (NAP).

Results

The additional cost of HDV screening and the use of a more expensive PEGylated-Interferon are offset by not wasting resources on treating co-infected persons with Tenofovir. The introductory price of NAP treatment must be less than $16,000 per course to become competitive with Tenofovir and PEGylated-Interferon in Brazil.

Conclusion

Additional screening for HDV is beneficial, even in a low HBV and HDV endemic regions of Brazil. We recommend PEGylated-Interferon, wherever possible, for both HBV and HDV. If PEGylated-Interferon is not available in abundance, PEGylated-Interferon for co-infections and 4-year Tenofovir treatment for mono-infections is recommended.

Molecular epidemiology of hepatitis delta and hepatitis B viruses circulating in two major provinces (East and North-West) of Pakistan

OBJECTIVES

HBV and HDV are major public health problems with millions affected globally and Pakistan accounts for a significant proportion of the global Hepatitis burden. This cross sectional study was designed to assess the general epidemiological and virological features of HBV and HDV in the Punjab and Khyber Pakhtunkhawa (KP) provinces of Pakistan.

METHODS

A total of 1890 HBV patients from March 2016 to May 2017 were recruited in the study and the presence of HDV was retrospectively evaluated in all participants. Most participants were young adults (from 21 to 30 years). Genotyping was based on PCR amplification using primers specific for HBV genotypes A-F, and HDV. 405 nucleotide fragments of HDV were sequenced. MEGA was used for phylogenetic analysis.

RESULTS

Overall prevalence of HBV was 14.08% (266/1890). Higher prevalence was observed in males (66.85%) as compared to females (33.15%). Co-infection of HDV was found in 39 (14.66%) patients. HBV genotype-D was prevalent in dual infections followed by HDV/A (p < 0.05).While HDV genotype 1 was predominant in all HBV positive samples. Compared to Punjab, coinfection was higher in KP (14.3% versus15.2%; p < 0.05).

CONCLUSION

The prevalence of HBV and HDV is high in Pakistan. The description of HBV and HDV genotypes circulating in East and North-West Pakistan can contribute to a better understanding of their relevance in regional epidemics. These infections are highly endemic in the KP, where their control is confounded by its vast territorial dimension with small, hard-to-reach municipalities and diverse ethnic populations.

Current and Future Management of Chronic Hepatitis D

Hepatitis D virus (HDV) is a defective RNA virus that requires the hepatitis B surface antigen (HBsAg) of the hepatitis B virus (HBV) for its assembly, release, and transmission. HDV is highly pathogenic, causing the least common, but most severe, form of chronic viral hepatitis at all ages. Although significant advances have been made in the treatment of chronic viral hepatitis, targeting HDV remains a major challenge because of the unconventional nature of this virus and the severity of its disease. The virus contains a ribonucleoprotein complex formed by the RNA genome with a single structural protein, delta antigen (HDAg), which exists in 2 forms (small and large HDAg) and is coated by HBsAg. Farnesylation of the large HDAg is essential for anchoring the ribonucleoprotein to HBsAg for the assembly of virion particles. HDV enters into hepatocytes by using the HBV receptor, the sodium taurocholate cotransporting polypeptide (NTCP). Unlike other RNA viruses, HDV does not encode its own polymerase but exploits the host RNA polymerase II for replication. Thus, in contrast to HBV and hepatitis C virus, which possess virus-specific enzymes that can be targeted by specific inhibitors, the lack of a virus-specific polymerase makes HDV a particularly challenging therapeutic target. Treatment of hepatitis D remains unsatisfactory, and interferon-α has been the only approved drug over the past 30 years. This article examines the unconventional nature of HDV, the current management of chronic hepatitis D, and how new insights from the HDV life cycle have led to the development of 3 novel classes of drugs (NTCP receptor inhibitors, farnesyltransferase inhibitors, and nucleic acid polymers) that are currently under clinical evaluation.

Reactivation of hepatitis B after liver transplantation: Current knowledge, molecular mechanisms and implications in management

Chronic hepatitis B (CHB) is a major global health problem affecting an estimated 350 million people with more than 786000 individuals dying annually due to complications, such as cirrhosis, liver failure and hepatocellular carcinoma (HCC). Liver transplantation (LT) is considered gold standard for treatment of hepatitis B virus (HBV)-related liver failure and HCC. However, post-transplant viral reactivation can be detrimental to allograft function, leading to poor survival. Prophylaxis with high-dose hepatitis B immunoglobulin (HBIG) and anti-viral drugs have achieved remarkable progress in LT by suppressing viral replication and improving long-term survival. The combination of lamivudine (LAM) plus HBIG has been for many years the most widely used. However, life-long HBIG use is both cumbersome and costly, whereas long-term use of LAM results in resistant virus. Recently, in an effort to develop HBIG-free protocols, high potency nucleos(t)ide analogues, such as Entecavir or Tenofovir, have been tried either as monotherapy or in combination with low-dose HBIG with excellent results. Current focus is on novel antiviral targets, especially for covalently closed circular DNA (cccDNA), in an effort to eradicate HBV infection instead of viral suppression. However, there are several other molecular mechanisms through which HBV may reactivate and need equal attention. The purpose of this review is to address post-LT HBV reactivation, its risk factors, underlying molecular mechanisms, and recent advancements and future of anti-viral therapy.

Development and performance of prototype serologic and molecular tests for hepatitis delta infection

Worldwide, an estimated 5% of hepatitis B virus (HBV) infected people are coinfected with hepatitis delta virus (HDV). HDV infection leads to increased mortality over HBV mono-infection, yet HDV diagnostics are not widely available. Prototype molecular (RNA) and serologic (IgG) assays were developed for high-throughput testing on the Abbott m2000 and ARCHITECT systems, respectively. RNA detection was achieved through amplification of a ribozyme region target, with a limit of detection of 5 IU/ml. The prototype serology assay (IgG) was developed using peptides derived from HDV large antigen (HDAg), and linear epitopes were further identified by peptide scan. Specificity of an HBV negative population was 100% for both assays. A panel of 145 HBsAg positive samples from Cameroon with unknown HDV status was tested using both assays: 16 (11.0%) had detectable HDV RNA, and 23 (15.7%) were sero-positive including the 16 HDV RNA positive samples. Additionally, an archival serial bleed panel from an HDV superinfected chimpanzee was tested with both prototypes; data was consistent with historic testing data using a commercial total anti-Delta test. Overall, the two prototype assays provide sensitive and specific methods for HDV detection using high throughput automated platforms, allowing opportunity for improved diagnosis of HDV infected patients.