3 december 2008

Lemur virus reveals HIV’s evolution

Madagascar's gray mouse lemur (Microcebus murinus)
The grey mouse lemur is expanding our knowledge of HIV's 'family tree'. Image: Alan Chapman.

The remains of an ancient HIV-like virus have been discovered in the genome of the Madagascan grey mouse lemur [Microcebus murinus] by a team led by Oxford University scientists.

The virus, called pSIVgml, is the first unambiguous example of a ‘missing link’ (a viral transitional form) between the simple lentiviruses, which can be caught by many animals, and HIV and simian retroviruses (SIVs) with their more complex genomes that only affect humans and other primates.

‘Because Madagascan lemurs have evolved in isolation for at least 14 million years this new discovery suggests that lentiviruses, a group which includes HIV and SIVs, have been infecting primates for at least this long,’ said Dr Aris Katzourakis from Oxford’s Department of Zoology and the Institute for Emergent Infections, James Martin 21st Century School, co-author of the report in this week’s PNAS.

it challenges our notions of how viruses such as HIV/AIDS might change and evolve

Dr Aris Katzourakis

‘It also suggests that primate lentiviruses are much more widespread than anyone previously thought and should be closely monitored for other viruses that could make the leap from infecting primates to infecting people,’ added Dr Katzourakis.

pSIVgml is unique amongst primate lentiviruses in that it is endogenous – it can be transmitted from generation to generation. Previously, in 2007, the Oxford-led team discovered the first endogenous lentivirus – RELIK – in the genome of the European rabbit.

‘Our work on pSIVgml and RELIK not only expands our knowledge of the ancient ‘family tree’ of HIV-like viruses,’ said Dr Katzourakis ‘it challenges our notions of how viruses such as HIV/AIDS might change and evolve – one of the biggest implications being that we can no longer say that HIV could not become endogenous in the future.’

Lentiviruses are associated with a range of diseases including immunodeficiency diseases such as HIV/AIDS in humans, and various malignancies and lymphatic and neurological conditions in primates, cats, and many hoofed mammals.

Apart from pSIVgml and RELIK all other known lentiviruses are exogenous – that is transmitted from host to host – instead of endogenous – passed on from generation to generation.

Dr Aris Katzourakis and Dr Oliver Pybus of the Department of Zoology led the research at Oxford alongside researchers from Imperial College London and Stanford University, California. Dr Katzourakis was supported by a James Martin Fellowship from Oxford’s James Martin 21st Century School.