14 DAY TRIAL // According to new scientific evidence, it would appear that the retroviruses from which the Human Immunodeficiency Virus (HIV) evolved have been plaguing the animal world since 100 million years ago. The new time frame is about 85 million years 'older' than first thought, which brings into focus the need to reassess the pathogen's evolution over the millennia. The preserved remains of a two-toed sloth recently revealed one of the HIV precursors, suggesting that immune systems in many species had been battling this class of viruses for a while, ScienceDaily reveals.
“Finding the fossilized remains of such a virus in this sloth is an amazing stroke of luck. 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,” Oxford University Department of Zoology expert Dr. Aris Katzourakis says. He also has an appointment in the James Martin 21st Century School, at the Institute for Emergent Infections. Details of the amazing research will be presented in this week's issue of the top journal Science, the team says.
HIV and the simian retroviruses (SIV) are a particular kind of retroviruses known as lentiviruses. Their precursor is not a lentivirus per se, but a “foamy virus,” a class of viral agents that has a lot in common with the complex structure of its more dangerous cousins. The new sloth fossil is also extremely important because it provides the first ever evidence of pathogens other than retroviruses infecting animal species so far back in history.
“In previous work we had found evidence for similar viruses in the genomes of rabbits and lemurs but 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,” Katzourakis adds.
The historical evolution of retroviruses is of paramount importance in understanding the dangers they pose to different species. That is to say, some agents, like foamy viruses, can cross the species barrier, but only a select few can trigger a pandemic in a new species they infect. Additionally, more research on HIV precursors could yield new approaches to handling the virus itself, and maybe even developing more advanced treatments for AIDS.