Specific and Nonhepatotoxic Degradation of Nuclear Hepatitis B Virus cccDNA
Julie Lucifora1,2,*,
Yuchen Xia1,*,
Florian Reisinger1,
Ke Zhang1,
Daniela Stadler1,
Xiaoming Cheng1,
Martin F. Sprinzl1,3,
Herwig Koppensteiner1,
Zuzanna Makowska4,
Tassilo Volz5,
Caroline Remouchamps6,
Wen-Min Chou1,
Wolfgang E. Thasler7,
Norbert Hüser8,
David Durantel9,
T. Jake Liang10,
Carsten Münk11,
Markus H. Heim4,
Jeffrey L. Browning12,
Emmanuel Dejardin6,
Maura Dandri2,5,
Michael Schindler1,
Mathias Heikenwalder1,†‡,
Ulrike Protzer1,2,†‡
+ Author Affiliations
1Institute of Virology, Technische Universität München–Helmholtz Zentrum München, 81675 Munich, Germany.
2German Center for Infection Research (DZIF), Munich and Hamburg sites, Germany.
31st Medical Department, University Hospital Mainz, 55131 Mainz, Germany.
4Department of Biomedicine, University Hospital Basel, 4031 Basel, Switzerland.
5Department of Internal Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
6GIGA-Research Laboratory of Molecular Immunology and Signal Transduction, University of Liège, 4000 Liège, Belgium.
7Department of General, Visceral, Transplantation, Vascular and Thoracic Surgery, Grosshadern Hospital, Ludwig Maximilians University, 81377 Munich, Germany.
8Department of Surgery, University Hospital Rechts der Isar, Technische Universität München, 85748 Munich, Germany.
9INSERM U1052, CNRS UMR 5286, Cancer Research Center of Lyon, University of Lyon, LabEx DEVweCAN, 69007 Lyon, France.
10Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA.
11Clinic for Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich-Heine University, 40225 Düsseldorf, Germany.
12Department of Immunobiology, Biogen Idec, Cambridge, MA 02142, USA.
↵* These authors contributed equally to this work.
↵‡ These authors contributed equally to this work.
Abstract
Current antivirals can control but not eliminate hepatitis-B-virus (HBV), because HBV establishes a stable nuclear cccDNA. Interferon-α treatment can clear HBV but is limited by systemic side effects. Here, we describe how interferon-α can induce specific degradation of the nuclear viral DNA without hepatotoxicity and propose lymphotoxin-β-receptor activation as a therapeutic alternative. Interferon-α and lymphotoxin-β-receptor activation up-regulated APOBEC3A and 3B cytidine-deaminases, respectively, in HBV-infected cells, primary hepatocytes and human liver-needle biopsies. HBV-core protein mediated the interaction with nuclear cccDNA resulting in cytidine-deamination, apurinic/apyrimidinic site formation and finally cccDNA degradation that prevented HBV-reactivation. Genomic DNA was not affected. Thus, inducing nuclear deaminases - e.g., by lymphotoxin-β-receptor activation - allows development of new therapeutics that combined with existing antivirals may cure hepatitis B.
Received for publication 18 July 2013.
Accepted for publication 5 February 2014. 作者: StephenW 时间: 2014-2-21 11:33
Scientists from the Helmholtz Zentrum München and the Technische Universität München have discovered how the viral DNA of the hepatitis B virus (HBV) can be degraded in the cell nucleus of liver cells, consequently allowing the virus to be eliminated. Viruses such as HBV can persist by depositing their genetic information (DNA) in the cell nucleus, where the DNA is normally not degraded. This prevents antiviral drugs from eliminating these viruses. But the newly discovered mechanism could make this possible without damaging the infected cell in the liver. In the current issue of the prestigious journal Science, the scientists report that now new therapeutic possibilities are consequently opening up.
Although preventive vaccination is possible, the World Health Organization (WHO) reports that more than 240 million people around the world are currently suffering from a chronic hepatitis B infection. They face a high risk of developing liver cirrhosis or even liver cancer. In Germany alone, more than half a million people are affected. Although available antiviral medicines can control the hepatitis B virus, they cannot completely eliminate it. As a result, the HBV in the patient's liver is reactivated as soon as the treatment is discontinued.
This is due to virus DNA (cccDNA: covalently closed circular DNA) "hidden" in the cell nucleus. This virus DNA stores multiple copies of the virus in the nucleus of infected liver cells (hepatocytes) and in this way protects itself from destructive influences. The cccDNA serves as a template for the virus' own proteins and new viral genomes. An international team of scientists headed by Prof. Ulrike Protzer and Prof. Mathias Heikenwälder, Institute of Virology at the Helmholtz Zentrum München and the Technische Universität München, has now found a way to selectively attack and eliminate the viral genetic information in the cell nucleus of the liver cells without damaging the host cell in the process.
"The degradation of viral DNA in the cell nucleus that we describe represents an important mechanism in the defence against the virus", Protzer reports. "Moreover, for the first time, the results offer the possibility to develop a treatment that can heal hepatitis B."
The scientists have discovered that in addition to interferons (the immune system's defence agents), activation of the lymphotoxin β receptor in the host cell promotes certain proteins and supports their function in such a way that they chemically modulate and degrade viral cccDNA. This keeps the virus from reactivating, and also prevents the disease from breaking out again, even after the treatment has ended. On the other hand, the proteins do not influence the genetic information of the host cell itself, which here is the liver cell. "With the activation of the lymphotoxin β receptor, also combined with substances that are already available, we have a very promising new therapy concept available", Heikenwälder explains. 作者: StephenW 时间: 2014-2-22 11:52