Hepatitis B Support Group
Hepatitis B virus infection may either be acute (self-limited) or chronic (long-standing). Persons with self-limited infection clear the infection spontaneously within weeks to months. There are currently several treatments for chronic hepatitis B that can increase a person's chance of clearing the infection.
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Wednesday, March 19, 2014 | An Educational story
Scientists discover how viral DNA of HBV can be
degraded in cell nucleus
Published on February 24, 2014 at 4:57 AM
Scientists from the Helmholtz Zentrum Mnchen and the Technische Universitt Mnchen 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 Heikenwlder, Institute of Virology
at the Helmholtz Zentrum Mnchen and the Technische Universitt Mnchen, 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 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 receptor, also combined with substances that are already available, we have a very promising new
therapy concept available", Heikenwder explains.
In addition to the Helmholtz Zentrum Mchen and the Technische Universit Mchen (TUM), TUM's Klinikum
rechts der Isar and the Dseldorf, Hamburg, Mainz and Munich university hospitals also participated in the
publication. International partners from Belgium, France, Switzerland and the USA also contributed.
Source: German Center for Infection Research