Retrovirology took a significant step forward in October 2010, when researchers managed to resurrect a long-dormant chimpanzee retrovirus, having identified its receptor. The discovery, as reported in Nature, could lead to humans understanding a great deal more about the way in which retroviruses work.
Endogenous viruses – those which have become incorporated into the host’s genome over time, are usually studied as part of the host’s DNA sequence. But virologists at New York’s Rockefeller University were effectively able to resurrect the CERV2 retrovirus, which had been dormant for around a million years.
CERV2 is important because not only have the researchers resurrected the virus, they have also worked out how it infects cells, and are working to find out how the chimpanzee host cells defended themselves. The hope is that by studying how ancient viruses were gradually assimilated into primates’ genetic code, scientists might be able to develop new ways of tackling contemporary viruses, such as HIV or any number of other types of virus.
The virus is present in chimpanzee DNA, but not in human DNA, suggesting that the infection took place after common ancestors of chimps and humans diverged, 5 or 6 million years ago. Human cells carry two proteins which fend off viruses when they enter cells, but it remained unclear why chimpanzees had been infected and why humans had not. The hope is that there is some incredibly interesting genetic reason which prevents human cells from being infected with this virus when chimpanzees are so vulnerable.
Other scientists have pointed out however that the true reason why chimpanzees ended up with a retrovirus dormant in their genome while humans avoided it might just be that the human race’s ancestors were never exposed to the virus. It’s been speculated that differences in chimp and human behaviour might have saved humans from infection (eg, not biting each other except in cases of extreme boredom).
But in studying the ways in which host’s defences built up a resistance to a long-dormant virus, the hope must be that we can develop ways to combat the deadly viruses which are plaguing populations in the 21st Century.
Certainly virologist Patric Jern from Sweden’s Uppsala University, feels that the Rokefeller team’s work points to a promising avenue of retrovirus research, and that we will see more examination of viruses which are effectively fossilised in host genomes, all with the aim of learning more about today’s active viruses by comparison.