HIV virus almost half a billion years old: study

Retroviruses, family of viruses that includes HIV, are almost half a billion years old and have been with animal hosts through the evolutionary transition from sea to land, according to a new Oxford study.
The research will help us understand more about the continuing 'arms race' between viruses and their hosts, researchers said.
"Very little has been known about the ancient origin of retroviruses, partly because of the absence of geological fossil records," said Aris Katzourakis from Oxford University in the UK.
"Retroviruses are broadly distributed among vertebrates and can also transmit between hosts, leading to novel diseases such as HIV, and they have been shown to be capable of leaping between distantly related hosts such as birds and mammals," said Katzourakis.

"However until now, it was thought that retroviruses were relative newcomers - possibly as recent as 100 million years in age," Katzourakis added.
"Our new research shows that retroviruses are at least 450 million years old, if not older, and that they must have originated together with, if not before, their vertebrate hosts in the early Paleozoic era," he said.

They would have been present in our vertebrate ancestors prior to the colonisation of land and have accompanied their hosts throughout this transition from sea to land, all the way up until the present day," researchers said.
Retroviruses are a family of viruses that includes the HIV virus responsible for the AIDS pandemic. They can also cause cancers and immunodeficiencies in a range of animals.

The 'retro' part of their name comes from the fact they are made of RNA, which they can convert into DNA and insert into their host genome - the opposite direction to the normal flow of information in a cell.
This property means that they can occasionally be inherited as endogenous retroviruses - retroviruses with an internal origin, forming a virtual genomic fossil record that can be used to look back into their evolutionary history.
This research used genome sequences from endogenous retroviruses that resemble the 'foamy' viruses - a group of viruses that tend to diverge alongside their hosts.

Foamy viruses are widespread in mammals and in this study the researchers unearthed genomic fossils for foamy-like retroviruses in highly diverse hosts, including ray-finned fish and amphibians in which they had not previously been found.
The study appears in the journal Nature Communications.