International Symposium: Control or eradication of viral hepatitis B and C
Barcelona, 30 y 31 de mayo de 2013
Barcelona, May 30-31, 2013
Inicio
- Hepatitis C virus life cycle, Volker Lohmann
- Burden of viral hepatitis in Europe and World-Wide, Heiner Wedemeyer
- Immune Response to HBV and HCV, Kyong-Mi Chang
- Present and future treatment of HCV using Direct Antiviral Agents (DAAs), Rafael Esteban Mur
- New insights into HCV replication: potential antiviral targets, Charles Rice
- Animal models to study HBV/HDV infections, Maura Dandri
- Variability and challenges to eradicate HBV, Fabien Zoulim
- Anti-HCV treatment in Liver transplanted patients, Xavier Forns Bernhardt
- Anti-HBV and HCV treatments in HIV coinfected patients, Javier García Samaniego Rey
- Antiviral resistance mutations to anti-HCV treatments and long-term persistence, Christoph Sarrazin
- Challenges of ultra-deep pyrosequencing to study clinical relevant minority mutants, Niko Beerenwinke
- The interplay between mutagenesis and inhibition. Novel strategies of antiviral therapy, Esteban Domingo Solans
Hepatitis C virus life cycle, Volker Lohmann
Hepatitis C virus infections cause severe liver disease and are a major global health burden. Accessibility of in vitro models and cell culture systems allowed a detailed understanding of several steps of the viral replication cycle in molecular detail. HCV enters the cell by a well defined set of receptors and entry factors, the positive strand RNA genome is released into the cytoplasm and drives translation of a polyprotein, which is processed by cellular and viral proteases. The viral nonstructural proteins then induce membrane alterations harboring the sites of viral RNA replication. Viral RNA synthesis and the formation of the viral replication sites involve a concerted action of viral nonstructural proteins and host factors like microRNA-122, cyclophilin A, and PI4KIIIα. Almost all antivirals approved for therapy or in late clinical development target polyprotein processing or viral and host proteins involved in RNA synthesis. The presentation will therefore particularly focus on our current understanding of the distinct steps involved in viral RNA replication and summarize our current knowledge on the mode of action of some of the inhibitors interfering with these processes.
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Burden of viral hepatitis in Europe and World-Wide, Heiner Wedemeyer
Viral hepatitis is a major global health burden. An estimated 500 Million individuals are carriers of a hepatitis virus and up to 1 Million deaths each year are caused by virus-induced end-stage liver disease or hepatocellular carcinoma. In addition, acute liver failure is not uncommon. E.g., 70.000 patients die each year from acute hepatitis E.
Overall, hepatitis B is the most prevalent chronic hepatitis virus infection with about 350 Million HBsAg carriers. Importantly, it is estimated that 15-20 Million patients are co-infected with hepatitis delta virus (HDV). HDV is considered the most severe form of chronic viral hepatitis. The global disease burden caused by HCV is still increasing and may peak during this century.
Fortunately, novel infection with HBV and HCV did significantly decline during the last 20 years. HBV vaccination is recommended by most (but not all!) countries. HCV infection is mainly present in drug user populations but medical procedures are still a main reason of new HCV infection. Few prophylactic HCV vaccine programs are ongoing but it will be challenging to prove efficacy. An HEV vaccine has been licensed in China in 2012. It is not clear yet when and if this vaccine will become available in other countries.
There are several challenges to reduce the disease burden caused by viral hepatitis. Access to screening and treatment must be ensured but hepatitis virus infections frequently affect special populations such as drug user, migrant populations, prisoner or individuals coinfected with other pathogens. Even though promising new therapies will become available in the near future it is currently unclear if the new drugs will reach all patients at need in resource-limited settings.
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Immune Response to HBV and HCV, Kyong-Mi Chang
HBV and HCV are both hepatotropic viruses that can persist and cause progressive liver disease, including cirrhosis and hepatocellular carcinoma. The outcome of viral infection is defined by the interplay between the virus and host immune defense. Both HBV and HCV have multiple mechanisms to evade or subvert innate cellular immune pathways with a delayed onset of adaptive immune response. While T cells play a key role in viral clearance and protective immunity, both HBV and HCV persists with the induction of multiple extrinsic and intrinsic T cell regulatory mechanisms including Tregs, regulatory cytokines (e.g. IL-10) and inhibitory costimulatory pathways (e.g. PD-1, CTLA-4, Tim-3). These regulatory factors may be induced by ongoing viral replication and inflammation, thereby limiting severe liver damage, but also inhibiting effective virus control and ultimately contributing to chronic liver damage. Viral persistence (particularly for HCV) is further associated with the induction of viral variants that escape B and T cell recognition, that challenges the development of effective HCV vaccine. The natural history and therapeutic outcomes of HBV and HCV infection are influenced by the underlying host immunogenetics (e.g. IL28 polymorphism, HLA type) although their precise mechanisms remains to be fully defined. This presentation will provide an update of host immune responses and their regulation in HBV and HCV infection, relevant for their natural history and therapy.
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Present and future treatment of HCV using Direct Antiviral Agents (DAAs), Rafael Esteban Mur
Hepatitis C virus (HCV) chronically infects 2,3 % of the world population and 2,5% of the Spanish population. Current standard treatment (“standard of care”, SOC) with pegylated interferon (peg-IFN) and ribavirin (RBV) eradicates infection in about 50% of HCV infected patients, but the associated side effects limit its effectiveness in many cases.
The recent development of small molecule compounds that directly inhibit the viral life cycle represents a major milestone for the treatment of chronic hepatitis C virus (HCV) infection. These new drugs that are collectively termed direct-acting antivirals (DAA) mainly include a range of inhibitors of the non-structural (NS) 3/4A protease, NS5B polymerase and NS5A protein. Two NS3/4A protease inhibitors (boceprevir and telaprevir) in combination with pegIFN+RBV have been approved by the FDA and EMEA, for the treatment of chronic HCV genotype 1 infection and cure rates could be increased by 20-30%. However, the majority of DAAs (more than 60) are still in early clinical development.
Significant improvements on SVR rates have been achieved in ongoing trials using combinations of DAAs with or without peg-IFN and/or RBV, and in some cases using exclusively, oral treatment regimens. This will opens the possibility to include into therapy, difficult-to-treat patients.
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New insights into HCV replication: potential antiviral targets, Charles Rice
An estimated 200 million people have been infected with hepatitis C virus (HCV) with a majority unable to clear the virus. Chronic HCV infection can lead to cirrhosis, hepatocellular carcinoma, and end-stage liver disease. It is generally believed that disease results at least in part from immune mediated inflammation. Since HCV’s discovery in 1989 significant progress has been made in establishing experimental systems and unraveling the details of the virus lifecycle. Examples include infectious molecular clones, RNA replicons and a robust cell culture system based on an HCV isolate from a rare case of acute fulminant hepatitis. Definition of the human factors required for HCV entry and blunting innate immune response pathways has led to the development of a mouse model that supports HCV entry, replication and virus production. Together these tools have increased our understanding of the HCV lifecycle and revealed numerous targets for therapeutic intervention. In 2011, two direct acting antivirals targeting the HCV serine protease were approved in combination with the previous standard of care, pegylated type I interferon and ribavirin. Even for the most difficult to treat HCV genotype (genotype I), more that 70% of patients can now be successfully treated. The future is even brighter with wealth of compounds in the pipeline against both virus and host targets, raising hopes for an all-oral interferon-free regimen with broad genotype coverage, minimal side-effects and a high cure rate.
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Animal models to study HBV/HDV infections, Maura Dandri
The obvious limitations imposed by the use of high primates and the necessity to perform infection studies with small well-characterized animals led to the development of human liver chimeric mice, such as the uPA/SCID mice. In this system, transgene-induced hepatocyte damage creates the space and the regenerative stimulus needed for transplanted hepatocytes to reconstitute the disease mouse liver, while the absence of adaptive immune responses enables xenogenic engraftment. Humanized mice have shown to remain susceptible to infection with HBV, HCV and HDV. Upon infection establishment, mice invariably become chronically infected and allow preclinical evaluation of compounds targeting any step of the viral life-cycle. We previously demonstrated the in vivo capacity of entry inhibitors derived from the large envelope protein of HBV to prevent de novo HBV and HDV infection, as well as HBV spreading post infection. Moreover, by transplanting HBV-infected hepatocytes isolated from chimeric mice into new uPA/SCID recipients we could investigate the impact of hepatocyte proliferation on cccDNA stability. The drastic cccDNA reduction induced by cell division in the absence of antiviral agents underscores a weak point in HBV persistence.
Within the mouse liver, human hepatocytes maintain a functional innate immune system and respond to stimuli induced by exogenously applied cytokines. By administering conventional human IFN-α we found that HBV inhibited the enhancement of various interferon stimulated genes (ISGs) and STAT nuclear accumulation, although IFN-α could induce temporary suppression of HBV replication by mediating epigenetic repression of the cccDNA minichromosome. Notably, sustained human hepatocyte responsiveness could be induced upon administration of the longer-acting peg-IFNα, which led to substantial viral antigen decline within the first 12 weeks of treatment, thus suggesting that the involvement of host´s immune components may not be required to trigger early HBsAg decline in IFN-treated patients. Using humanized mice we recently studied the antiviral state of the human hepatocytes in the setting of chronic HBV/HDV co-infection compared to HBV mono-infection. Establishment of HDV infection was accompanied by a remarkable induction of human ISGs, while HBV mono-infection led to only moderate ISG elevations. Interestingly, enhancement of human-specific cytokine (i.e. TGF-ß, IFN-λ) was predominantly found in HBV/HDV infected mice. These studies suggest that elevated pre-treatment ISG and interferon levels may directly contribute to liver damage and inflammation, providing a rationale for the more severe course of HDV-associated liver disease. Such antiviral state induction might also explain the lower levels of HBV activity frequently found in co-infected hepatocytes.
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Variability and challenges to eradicate HBV, Fabien Zoulim
HBV mainly infect hepatocytes. It replicates its DNA genome via a reverse transcriptase phase. The persistence of viral covalently closed circular (ccc) DNA, the viral minichromosome, in the nucleus of infected cells is responsible for the chronicity of the infection at the level of a single cell. Because of its long half-life, long-term administration of nucleos(t)ide analogues (NUC) is necessary to prevent relapses of viral replication. However, because of the error rate of the viral polymerase and the spontaneous viral genome variability, antiviral therapy may be associated with the selection of drug resistant mutants. The advent of novel NUCs with a high barrier to resistance has limited the risk of antiviral drug resistance. It is now possible to achieve viral suppression in the majority of infected patients. The main challenge is to develop new treatment strategies toward a cure of the infection with a clearance of HBsAg and/or cccDNA. HBsAg clearance is obtained in only 10% of patients treated with NUCs or Interferon alpha. Several approaches are being evaluated in experimental models. The clearance of cccDNA might require hepatocyte turn over induced by immune cell killing, leading to equal or unequal dilution of cccDNA through hepatocyte mitosis. The destruction of cccDNA may also be induced by the induction of several cell signalling pathways leading to degradation by nucleases. If cccDNA cannot be eliminated, its silencing can be another objective by interfering with its epigenetic control with drugs altering the acetylation/methylation status of histones or via the induction of cytokines, including interferon alpha. In that respect, the restoration of innate responses that are repressed by HBV represent another interesting concept. Studies investigating the effect of TLR agonists on the intrahepatic innate responses and the reshaping of adaptive T cell responses are ongoing in experimental models. Immunomodulatory approaches based on therapeutic vaccine activation of specific CD4+ and CD8+ T cell responses might also represent a complement to NUC based therapy. These new developments should also help designing early treatment intervention strategies to prevent the development of hepatocellular carcinoma.
References
Zoulim F, Locarnini S. Hepatitis B virus resistance to nucleos(t)ide analogues.Gastroenterology. 2009 Nov;137(5):1593-608
Zoulim F, Luangsay S, Durantel D. Targeting Innate Immunity: A New Step in the Development of Combination Therapy for Chronic Hepatitis B. Gastroenterology 2013, in press
Zoulim F, Testoni B, Lebossé F. Kinetics of intrahepatic cccDNA and serum HBsAg during antiviral therapy for chronic hepatitis B - Lessons from experimental and clinical studies. Clinical Gastroenterology and Hepatology, 2013 in press.
Belloni L, Allweiss L, Guerrieri F, Pediconi N, Volz T, Pollicino T, Petersen J, Raimondo G, Dandri M, Levrero M. IFN-α inhibits HBV transcription and replication in cell culture and in humanized mice by targeting the epigenetic regulation of the nuclear cccDNA minichromosome. J Clin Invest. 2012 Feb 1;122(2):529-37.
Zoulim F, Mason WS. Reasons to consider earlier treatment of chronic HBV infections. Gut 2012;61:333-336.
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Anti-HCV treatment in Liver transplanted patients, Xavier Forns Bernhardt
Liver transplantation(LTx) is the only alternativefor patients withend-stage liver cirrhosisorhepatocellularcarcinoma. Hepatitis B andC(particularlyC) are the most common causeofcirrhosis and liver cancerin our environment andtherefore thefirst indication of LTx. Since the introductionofanti-HBVimmunoglobulinandespecially neworal antivirals, the recurrence ofpost-transplant HBVis no longera problemand patients havean excellent prognosis. Conversely,post-transplant HCVis the leading causeof liver graft lossin the long termand representsa real problem forthe majority oftransplant programs. Among the strategieswe haveto prevent this infectionin the graftincludeantiviraltreatmenton the waiting list(only inpatientswith compensated cirrhosis) and treatment in the post-transplant (whenliver damagehas occurred). These strategiesachieve HCV cure infectioninone third ofpatients.However,it is likely thatin the next years prevention orcure of HCV infection will be achieved ina much larger proportionof cases usingdirectantiviral agents (DAAs)that providegreater efficiency,tolerance and safety.
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Anti-HBV and HCV treatments in HIV coinfected patients, Javier García Samaniego Rey
Coinfection with hepatitis B virus (HBV) is common in patients with human immunodeficiency virus (HIV) infection because both agents share the same routes of transmission. Chronic hepatitis B virus (HBV) infection is recognised in nearly 10% of HIV infected patients. Co-infected individuals show an accelerated course of HBV-associated liver disease with faster progression to cirrhosis. The indications for HBV therapy are the same as in HIV-negative patients, based on HBV DNA levels, serum ALT levels and histological lesions, irrespective of the CD4 cell count. Thus, most co-infected patients should be simultaneously treated for both HIV and HBV. Tenofovir combined with emtricitabine or lamivudine plus a third agent active against HIV is a good strategy in this scenario. In a small number of patients with CD4 count >500/ml, chronic hepatitis B can be treated before the institution of anti-retroviral therapy; pegylated interferon (mostly for HBe-positive patients), adefovir and telbivudine, which are not proven to be active against HIV, should be the therapeutic alternatives. Lamivudine, entecavir and tenofovir have activity against both HIV and HBV and are contraindicated as single agents for hepatitis B in co-infected patients because of the risk of developing HIV resistance.
Chronic hepatitis C is a leading cause of morbidity and mortality in HIV population. The prevalence of HIV/HCV coinfection is very high among intravenous drug users. Thus, chronic liver disease due to HCV infection is a major public health problem. Therapy with pegylated interferon alfa plus ribavirin has a limited efficacy in coinfected patients. The recent approval of the first direct acting antivirals (DAAs), telaprevir and boceprevir, in combination with PegIFN/RBV for the treatment of HCV genotype 1 infection has significantly increased the rate of sustained virological response in both monoinfected and coinfected patients. These HCV treatment regimens represent a “new paradigm” for care of HCV disease and may lead to higher rates of HCV eradication in HIV/HCV-coinfection setting. However, the new concerns include the adequate management of serious adverse effects (particularly anemia), adherence and drug-drug interactions with antiretroviral agents.
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Antiviral resistance mutations to anti-HCV treatments and long-term persistence, Christoph Sarrazin
HCV replicates with a short half-life and high viral turn-over. The non-proof-reading HCV NS5B RNA-dependent RNA-polymerase hereby generates a large number of closely related but different viral isolates (termed quasispecies). HCV NS3/4A protease inhibitors Boceprevir and Telaprevir have been approved for treatment of chronic hepatitis C genotype 1 infected patients. Both, compounds showed a medium to strong antiviral activity in phase 1 clinical studies but cannot be used as monotherapies because of a rapid selection of pre-existent resistant variants followed by viral break-through.