Media

All viruses ‘are potential stowaways in our DNA’

19 November 2010

‘Fossil viruses’ preserved inside the DNA of mammals and insects suggest that all viruses, including relatives of HIV and Ebola, could potentially be ‘stowaways’ transmitted from generation to generation for millions of years, according to new research.

A team from Oxford University and the Aaron Diamond AIDS Research Center built on earlier work at Oxford that discovered the fossilised remains of an ancient HIV-like virus in the genomes of animals including sloths, lemurs and rabbits.

The team’s new research, reported in this week’s PLoS Genetics, shows that many more different types of viruses are endogenous – capable of being transmitted from generation to generation – with ‘fossil viruses’ turning up in the genomes of creatures as different as mosquitoes, wallabies, and humans.

‘Many of these viruses, such as the ancestors of Ebola, are far more ancient and spread across many more animal groups than anyone ever suspected,’ said Dr Aris Katzourakis of Oxford University’s Department of Zoology, an author of the report. ‘We’ve demonstrated that viruses have been integrating within animal genomes for at least 100 million years.’

‘We’ve also shown that, in some cases, viral genes have been domesticated by their hosts, and put to use by the hosts for their own purposes, demonstrating that captured viral sequences may have played a larger than expected role in animal evolution.’

Understanding the historical conflict between viruses and animal immune systems could lead to new approaches to combating existing viruses such as HIV and Ebola. It could also help scientists to decide which viruses that cross species are likely to cause dangerous pandemics in the future.

‘These viruses represent the tip of the iceberg of endogenous viral diversity,’ said Dr Katzourakis. ‘We have discovered a large and diverse set of virus sequences preserved in animal genomes, which together include representatives of all known viral groups. This demonstrates a potential for endogenisation for any virus, and illustrates that viral fossil records may be uncovered for many elusive viral groups.’

For more information contact Dr Aris Katzourakis on mobile +44 (0)7922 162006 or email aris.katzourakis@zoo.ox.ac.uk

Alternatively contact the University of Oxford Press Office on +44 (0)1865 283877 or email press.office@admin.ox.ac.uk

Notes for editors

  • A report of the research, ‘Endogenous viral elements in animal genomes’ by Dr Aris Katzourakis of Oxford University and Robert J. Gifford of the Aaron Diamond AIDS Research Center, New York, is published in PLoS Genetics on 18 November 2010.
  • One of the more surprising results that came out of the human genome sequencing project was that our genomes contain more retroviruses than they contain genes that encode for proteins. The presence of these retroviral sequences can be explained by the fact that retroviruses integrate into chromosomal DNA as part of their normal replication cycle. Occasional integrations into germ-line cells lead to these viruses being transmitted to offspring, forming a ‘fossil record’ of ancient retroviruses, in many ways analogous to the paleontological fossil record.
  •  Viral fossils identified include the filoviruses (relatives of the Zaire Ebola virus that causes extreme haemorrhaging and death) and Bunyaviruses (also related to highly pathogenic viruses). The team also found numerous viruses related to mammalian viruses in the genomes of insect vectors (ticks, mosquitoes).