Ancestors of the present-day Human Immunodeficiency Virus (HIV) have been battling it out with mammal immune systems since mammals first evolved
around 100 million years ago – about 85 million years earlier than previously thought, scientists now believe.
The remains of an ancient HIV-like virus have been discovered in the genome of the two-toed sloth by a team led by Oxford University scientists, Science Daily reported.
“Finding the fossilised remains of such a virus in this sloth is an amazing stroke of luck”, said researcher Aris Katzourakis. “Because this sloth is so 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.”
The researchers found evidence of “foamy viruses”, a kind of retrovirus that resembles the lentiviruses, such as HIV and simian retroviruses (SIVs) —as opposed to simple retroviruses found throughout the genomic fossil record.
“This study suggests the ancestors of complex retroviruses, such as HIV, may have been with us from the very beginnings of mammal evolution”, said Katzourakis.
Understanding this conflict can help experts decide which viruses that cross species are likely to cause pandemics — such as swine flu — and which, like bird flu cross this species barrier but never cause pandemics in mammals.
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