A team led by Oxford University scientists, including Dr Aris Katzourakis, Research Fellow at the Institute for Emerging Infections, has found evidence that the retroviruses which gave rise to HIV have been battling it out with mammal immune systems since mammals first evolved around 100 million years ago.
The remains of an ancient HIV-like virus were discovered in the genome of the two-toed sloth, suggesting that these retroviruses existed about 85 million years earlier than previously thought. Because this sloth is so geographically and genetically isolated its genome gives us a window into the ancient past of mammals, their immune systems, and the types of viruses they had to contend with. This new research suggests that the ancestors of complex retroviruses, such as HIV, may have been with us from the very beginnings of mammal evolution.
Understanding the historical conflict between complex viruses and mammal immune systems could lead to new approaches to combating existing retroviruses, such as HIV. It can also help scientists to decide which viruses that cross species are likely to cause dangerous pandemics – such as swine flu – and which, like bird flu and foamy viruses, cross this species barrier but then never cause pandemics in new mammal populations.
The paper: "Macroevolution of Complex Retroviruses" is published in this week's Science.