The scientific basis of combination therapy for chronic hepatitis B functional cure

Functional cure of chronic hepatitis B (CHB) — or hepatitis B surface antigen (HBsAg) loss after 24 weeks off therapy — is now the goal of treatment, but is rarely achieved with current therapy. Understanding the hepatitis B virus (HBV) life cycle and immunological defects that lead to persistence can identify targets for novel therapy. Broadly, treatments fall into three categories: those that reduce viral replication, those that reduce antigen load and immunotherapies. Profound viral suppression alone does not achieve quantitative (q)HBsAg reduction or HBsAg loss. Combining nucleos(t)ide analogues and immunotherapy reduces qHBsAg levels and induces HBsAg loss in some patients, particularly those with low baseline qHBsAg levels. Even agents that are specifically designed to reduce viral antigen load might not be able to achieve sustained HBsAg loss when used alone. Thus, rationale exists for the use of combinations of all three therapy types. Monitoring during therapy is important not just to predict HBsAg loss but also to understand mechanisms of HBsAg loss using viral and immunological biomarkers, and in selected cases intrahepatic sampling. We consider various paths to functional cure of CHB and the need to individualize treatment of this heterogeneous infection until a therapeutic avenue for all patients with CHB is available

Superinfection and cure of infected cells as mechanisms for hepatitis C virus adaptation and persistence

Copyright © 2018 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).RNA viruses exist as a genetically diverse quasispecies with extraordinary ability to adapt to abrupt changes in the host environment. However, the molecular mechanisms that contribute to their rapid adaptation and persistence in vivo are not well studied. Here, we probe hepatitis C virus (HCV) persistence by analyzing clinical samples taken from subjects who were treated with a second-generation HCV protease inhibitor. Frequent longitudinal viral load determinations and large-scale single-genome sequence analyses revealed rapid antiviral resistance development, and surprisingly, dynamic turnover of dominant drug-resistant mutant populations long after treatment cessation. We fitted mathematical models to both the viral load and the viral sequencing data, and the results provided strong support for the critical roles that superinfection and cure of infected cells play in facilitating the rapid turnover and persistence of viral populations. More broadly, our results highlight the importance of considering viral dynamics and competition at the intracellular level in understanding rapid viral adaptation. Thus, we propose a theoretical framework integrating viral and molecular mechanisms to explain rapid viral evolution, resistance, and persistence despite antiviral treatment and host immune responses.info:eu-repo/semantics/publishedVersio

Development of an mRNA Vaccination Strategy for the Prevention and Treatment of HBV Infection

A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science (MSc) by dissertation in Haematology and Molecular MedicinePersistent HBV infection carries an elevated risk of developing cirrhosis and hepatocellular carcinoma (HCC). Infection is preventable by immunisation with a recombinant protein vaccine encompassing the major surface antigen (HBsAg) of Hepatitis B virus (HBV). The vaccine is globally administered resulting in a notable decrease in global carrier rates. However, some recipients (5-10%) remain as hypo- or non-responders associated with minimal to no protective antibody levels. HBV-specific DNA-vaccines have demonstrated potential for induction of potent antibody responses and target-specific activation of cellular immunity with purported application in chronic HBV infection (CHB) treatment. Furthermore, in situ production of HBsAg allows for inclusion of neutralising and cross-specific preS epitopes absent from the current vaccine. Immunisation with mRNA accompanies a superior safety profile and offers several other advantages over DNA, but no such vaccine targeting HBV exists. To develop an anti-HBV mRNA-based vaccine, vectors engineered for mRNA production were constructed. From the production vectors, LHBs (large HBsAg) and SHBs (small or major HBsAg) mRNA was synthesised by in vitro transcription using phage T7 polymerase, and translated in transfected cells to produce detectable LHBs and SHBs. SHBs was readily secreted while LHBs was retained intracellularly. This investigation constitutes a preliminary step towards the preclinical development of an anti-HBV mRNA-based prophylactic and therapeutic vaccine formulation and has provided proof-of-principle that LHBs encompassing preS epitopes is expressible in situ from synthetic mRNA transcripts. Further developments will include modification of the mRNA synthesis protocol to comply with GMP regulations and functional testing of the vaccine candidate in appropriate animal models. Keywords: HBV, HCC, HBsAg, preS, DNA-vaccines, CHB, mRNA-based vaccineGR201

Restoring, releasing or replacing adaptive immunity in chronic hepatitis B

Multiple new therapeutic approaches are currently being developed to achieve sustained, off-treatment suppression of HBV, a persistent hepatotropic infection that kills ~2,000 people a day. A fundamental therapeutic goal is the restoration of robust HBV-specific adaptive immune responses that are able to maintain prolonged immunosurveillance of residual infection. Here, we provide insight into key components of successful T cell and B cell responses to HBV, discussing the importance of different specificities and effector functions, local intrahepatic immunity and pathogenic potential. We focus on the parallels and interactions between T cell and B cell responses, highlighting emerging areas for future investigation. We review the potential for different immunotherapies in development to restore or release endogenous adaptive immunity by direct or indirect approaches, including limitations and risks. Finally, we consider an alternative HBV treatment strategy of replacing failed endogenous immunity with infusions of highly targeted T cells or antibodies

Treatments for hbv: A glimpse into the future

The hepatitis B virus is responsible for most of the chronic liver disease and liver cancer worldwide. As actual therapeutic strategies have had little success in eradicating the virus from hepatocytes, and as lifelong treatment is often required, new drugs targeting the various phases of the hepatitis B virus (HBV) lifecycle are currently under investigation. In this review, we provide an overview of potential future treatments for HBV

Discovering Drugable Immune Targets in Gastrointestinal & Hepatic Disease

Discovering Drugable Immune Targetsin Gastrointestinal & Hepatic Diseas

How Current Direct-Acting Antiviral and Novel Cell Culture Systems for HCV are Shaping Therapy and Molecular Diagnosis of Chronic HCV Infection

We have entered a new era of hepatitis C virus (HCV) therapy in which elimination of infection and disease is a real possibility. HCV cell culture models were instrumental for identification of therapeutic targets, testing candidate drugs, and profiling of therapeutic strategies. Here we describe current and novel methods of cell culture systems for HCV that are allowing investigation of HCV life cycle and virus-host interaction required for replication and propagation. The development of protocols to grow infectious virus in culture and generate hepatocyte cell lines from specific individuals hold great promise to investigate the mechanisms exploited by the virus to spread the infection and the host factors critical for HCV replication and propagation, or resistance to infection. Since host factors are presumably conserved and equally interacting with different HCV isolates and genotypes, the development of drugs targeting host factors essential for virus replication holds great promises in further increasing treatment efficacy. Refocusing of therapeutic goals also impacted in vitro diagnosis. The primary goal of anti-HCV therapy is to achieve a sustained virologic response (SVR) defined as " undetectable" HCV RNA genome in the serum or plasma at 12 to 24 weeks following the end of treatment. Use of direct antiviral agents has substantially changed the threshold of the viral load used to define SVR and led to a reassessment, as discussed herein, of result interpretation and requirements of clinically-approved, quantitative molecular assays

New treatments for chronic hepatitis C

Treatments for chronic hepatitis C has evolved significantly in the past 15 years. The standard of care (SOC) is peginterferon alfa-2a/-2b with ribavirin for 48 weeks or 24 weeks in patients infected with HCV genotype 1 or 2/3, respectively. The treatment duration can be individualized based on the baseline viral load and the speed of the virologic response during treatment. However, current therapies are associated with side effects, complications, and poor patient tolerability. Therefore, there is an urgent need to identify better strategies for treating this disease. An improved sustained virologic response (SVR) can be achieved with new HCV-specific inhibitors against NS3/4A and NS5B polymerases. Recent trials have found SVR rates in patients with HCV genotype 1 infection of 61~68% and 67~75% for combining the SOC with the protease inhibitors telaprevir and boceprevir, respectively. Several new HCV-specific inhibitors such as protease inhibitors and nucleoside and non-nucleoside polymerase inhibitors as well as non-HCV-specific compounds with anti-HCV activity are currently in clinical evaluation. In this review we discuss these new treatments for chronic hepatitis C