Researchers have found evidence of ancient human viruses in the DNA of modern humans.
A research team looked at the genetic data of Neanderthals and Denisovans (another human relative) and compared it to DNA information taken from modern-day cancer patients, a University of Oxford news release reported.
The researchers noticed Neanderthals and Denisovans carried viruses present in modern genetics, indicating the "bugs" originated over half a million years ago.
Approximately eight percent of human DNA is made up of "endogenous retroviruses" (ERVs), which are leftover virus sequences that can be passed down through uncountable generations. These virus remnants are grouped into the 90 percent of human DNA that researchers are yet to find the function of; called "junk DNA."
"I wouldn't write it off as "junk" just because we don't know what it does yet," Doctor Gkikas Magiorkinis, an MRC Fellow at Oxford University's Department of Zoology. "Under certain circumstances, two 'junk' viruses can combine to cause disease - we've seen this many times in animals already. ERVs have been shown to cause cancer when activated by bacteria in mice with weakened immune systems."
The researchers hope to look into these viruses (which are members of the HML2 family) and find ancient links to cancer and HIV.
"How HIV patients respond to HML2 is related to how fast a patient will progress to AIDS, so there is clearly a connection there," Doctor Magiorkinis, said. 'HIV patients are also at much higher risk of developing cancer, for reasons that are poorly-understood. It is possible that some of the risk factors are genetic, and may be shared with HML2. They also become reactivated in cancer and HIV infection, so might prove useful as a therapy target in the future."
The team hopes to find a link between these viruses and an increased risk of developing cancer, and if they are still active in the body.
"Using modern DNA sequencing of 300 patients, we should be able to see how widespread these viruses are in the modern population. We would expect viruses with no negative effects to have spread throughout most of the modern population, as there would be no evolutionary pressure against it. If we find that these viruses are less common than expected, this may indicate that the viruses have been inactivated by chance or that they increase mortality, for example through increased cancer risk," Doctor Robert Belshaw, formerly of Oxford University and now a lecturer at Plymouth University, who led the research, said.
"Last year, this research wouldn't have been possible. There were some huge technological breakthroughs made this summer, and I expect we'll see even greater advances in 2014. Within the next [five] years, we should be able to say for sure whether these ancient viruses play a role in modern human diseases," he said.
