One probable reason why humans lack immunity to HIV is because they carry a version of a protein, which protects them against a long extinct virus said a team of researchers.
Findings of researchers at the Fred Hutchinson Cancer Research Centre in Seattle published in the journal Science have revealed that while non human primates such as macaus carry an antiviral protein called TRIM5-alpha which offers protection against HIV, the slightly altered version of the protein found in humans, offers no such protection. Instead what humans carry is a protein that offers protection against the extinct virus Pan troglodyte endogenous retrovirus, or PERV for short.
Expertspeak
According to virologist Micheal Emerman, who conducted the study with evolutionary biologist Harmit Malik and postgraduate student Shari Kaiser,
“About 4 million years ago, this virus was active and independently infecting all these (chimpanzees and gorillas) species, but not humans.”
In reconstructing what is being billed a fascinating story in evolutionary biology, the researchers recreated the retrovirus in the laboratory to demonstrate how it could infect cells. This reconstruction was made possible by picking on genetic instructions left by the now extinct virus in the genomes of chimps.
Like all retroviruses, PERV planted a copy of its genetic instructions in the genes of the cells it invaded. These instructions converted to DNA, are carried down through generations, undergoing many mutations in the interim. By counting the number of mutations in the genome of a modern chimp, the researchers were able to calculate how long ago the primates were infected.
The lab tests also revealed that cells carrying human TRIM5 could not be infected by the resurrected virus but those cells which carried the ape and old monkey TRIM5 were vulnerable.
One possibility expressed by the researchers is that the virus affected humans also but those who survived did so with an altered version of the protein which in turn compromised the human body’s natural resistance to HIV.
