Discovery of a more than 82 million years old hepatitis B virus
Scientists of Münster University were able to detect prehistoric hepatitis B viruses in bird genomes / Publication in "Nature Communications"
The liver inflammation hepatitis B comprises 350 million chronic illnesses and is one of the most prevalent virus infections worldwide – and the ancestors of this virus existed for more than 82 million years.
Artistic size comparison of hepatitis B viruses and human lymphocytes
This was discovered by a group of scientists around Dr. Alexander Suh at the Institute of Experimental Pathology at the University of Münster, as they were able to detect prehistoric hepatitis B viruses in bird genomes. The renowned scientific journal “Nature Communications” published the team’s findings in its current issue.
The researchers’ study – which is part of the project “Phylogeny of Birds” funded by the German Science Foundation (DFG) – permits unprecedented insights into the early evolution of hepatitis B viruses of birds and mammals. “Viruses themselves do not leave behind fossils that would provide insights into their past”, notes Dr. Alexander Suh on the rationale of the Münster research group’s work. Instead, together with the group leader Dr. Jürgen Schmitz, and Dr. Jan Ole Kriegs from the LWL-State Museum of Natural History of the Westphalia-Lippe Regional Association (LWL), Suh decided to look for genomic remnants of paleoviral sequences in the DNA of host organisms, such as birds.
As insertions of viral sequences in the genome of a host change relatively slowly, it is possible to study viral DNA sequences that are many millions of years old, as noted by Dr. Jürgen Schmitz: “The prehistorical viral DNA becomes frozen in its original state at the time of insertion into the host genome and thus remains discernible as such until present – thus, we refer to these sequences as molecular fossils", says Schmitz.
This procedure for the analysis of molecular fossils permits the reconstruction of the early evolution of viruses. Suh and his colleagues were able to comprehensively demonstrate this on the example of prehistoric insertions of hepatitis B viruses in bird genomes. “A sensational finding was a nearly complete virus genome that has been preserved for more than 82 million years as a molecular fossil”, describes Suh. This molecular fossil thus stems from the Late Mesozoic – a geological period where dinosaurs still roamed on earth.
The researchers’ findings imply that mammalian hepatitis B viruses probably originated via a bird–mammal host switch. “Furthermore, our results indicate that the oncogenic X gene of human hepatitis B viruses emerged relatively late in the evolution of this virus family”, reports Suh. Hence, the Münster researchers’ sensational finding does not only provide insights into a millions of years old type of avian hepatitis B, but also into the extant characteristics of this very prevalent virus infection in humans.
Dr. Thomas Bauer
Dekanat der Medizinischen Fakultät
der Westfälischen Wilhelms-Universität Münster
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Suh, A., Brosius, J., Schmitz, J., Kriegs, J. O. (2013) The genome of a Mesozoic paleovirus reveals the evolution of hepatitis B viruses. Nature Communications, http://dx.doi.org/10.1038/ncomms2798
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