Hepatitis B viruses (HBV) are major pathogen accounting for 1 million deaths per year world-wide. The death toll comes from chronic infections, which lead to liver cirrhosis and liver failure and from liver cell carcinoma. HBV contains a partially double-stranded DNA, which is found inside the viral capsid, which is surrounded by the viral surface proteins. HBV infection is very efficient and replication occurs via reverse transcription of so-called pregenomic RNA, which is transcribed from a nuclear double stranded DNA. This nuclear DNA is stable and is not affected by current therapies, which target production of new virions. During infection, HBV has to transport its genome from the cell periphery into the nucleus also requiring that virus’s DNA becomes released from the capsids. As the capsid is required for transport of the genome to the nucleus, genome release must be coordinated and must occur at the end of the transport process through the cytoplasm. Despite of the importance for establishing and maintaining infection, very little is known about the driving forces and interactions leading to genome nor about the fate of the nuclear DNA. We analyze the underlying molecular interactions using methods from cell biology including time-lapse microscopy for better understanding the bottlenecks of the transport and subsequent repair processes, which convert virion’s partially double-stranded DNA to nuclear double stranded DNA.
Adeno-associated viruses (AAV) are not associated with any disease. They serve as platforms in gene therapy and there are currently two treatments of genetic diseases based on AAVs: Zolgensma™ is used against spinal muscular atrophy and Glybera™ against lipoprotein lipase deficiency. AAVs also replicate via nuclear DNA and – similarly to HBV - the genome has to be transported through the cytoplasm into the nucleus, which requires distinct transport steps mediated via the viral capsid. However, in contrast to HBV, AAVs are very inefficient and the intracellular transport steps appear to be rate-limiting. Our research on the molecular mechanisms of HBV transport and genome release are thus complemented with AAVs but with the aim of increasing efficiency.