Thursday, October 29

Ancient viruses buried in our DNA may reawaken and cause illness

New Scientist Default Image

Brian Larossa

STRANGE fevers and unusual infections are common among the people with HIV who come to Avindra Nath’s clinic for treatment. But when one young man showed up in 2005 struggling to move his arms and legs, Nath was baffled. Although the man had been diagnosed with HIV a few years earlier, his new symptoms matched those of amyotrophic lateral sclerosis (ALS), also known as motor neuron disease. In an attempt to get his HIV under control, Nath convinced him to start taking antiretroviral drugs. Much to everyone’s surprise, his ALS symptoms improved too.

ALS is caused by progressive deterioration and death of the nerve cells that control voluntary movement. What triggers this destruction is unclear, but recovery is rare. Puzzled, Nath, who ran an immunology clinic at Johns Hopkins University in Baltimore, began searching the medical literature. There he found other people with HIV and ALS whose ALS symptoms improved with antiretrovirals – drugs that stop viruses replicating. Could this neurological condition be triggered by a dormant virus hiding in our DNA, brought back to life by HIV?

This question doesn’t only hover over ALS. Increasingly, we are waking up to the possibility that conditions including multiple sclerosis (MS), schizophrenia and even type 1 diabetes may in some cases be triggered by ancient viruses buried in our genomes. Under certain circumstances, they revive and start producing mutated versions of themselves, triggering the immune system to attack and destroy neighbouring tissues.

“It’s a wild new theory of disease,” says Cedric Feschotte, a molecular biologist at Cornell University in New York. And already it is pointing the way to new treatments. …