An Ancient Virus Was Just Thawed and Used to Infect a Plant

Genetic information from a 700-year-old virus was just resurrected from frozen Canadian caribou poop and used to infect a plant, making scientists realize that viruses can remain, well, virulent for a really long time.

The virus, eloquently called ancient caribou feces associated virus (aCFV), was discovered in a Canadian ice patch. Because it has remained frozen for so long, the virus's DNA was still in pretty good shape and was easily disassociated from the caribou DNA.

Eric Delwart, a researcher at the Blood Systems Research Institute in San Francisco, thought that the virus could still potentially be used to infect plants, as it did in antiquity, so he made clones of the virus and introduced it to a tobacco plant in the lab. Turns out that, yes, indeed, the DNA was still in good enough shape to infect it.

"We demonstrate that genetic material from ancient viruses associated with caribou fecal matter was cryogenically preserved for at least seven centuries and that the cloned DNA genome of one of these viruses replicated and spread systemically in an extant plant," Delwart wrote in a study published in Proceedings of the National Academy of Sciences.

The team used cloned DNA instead of the original virus itself for experimental purposes; Delwart suggests in the paper that old frozen viruses themselves may remain infectious for centuries.

This isn't the first time a really old virus has been brought back to life. Earlier this year, French researchers found a 30,000 year old Russian virus that was frozen in permafrost and brought it back to life. They suspected it was still virulent, but didn't actually use it to infect anything.

Delwart's finding raises the question: Why are we playing around with ancient viruses, anyway? He suggests that if we study the origins of certain viruses, we'll be better prepared to respond to ancient viruses if they do happen to become unfrozen and infectious. And, with climate change, that's certainly a possibility.

"As climate change accelerates the melting of arctic ice, it is possible that ancient viral particles and the associated nucleic acids could be released into the environment," he wrote. "If such virions are infectious, their release could contribute to the diversity of circulating viruses."

In this case, aCFV infected a tobacco plant, but didn't appear to cause any outward symptoms of disease. To prove that the plant was infected, Delwart sequenced the genomes of newly-grown leaves on the plant and was able to detect and isolate the viral DNA, which had replicated inside of the plant.

He suggested that there were no symptoms in the plant because tobacco wasn't the virus's original host, and that we currently don't really know what plants aCFV originally infected. We really don't know a lot about ancient viruses at all, but, well, now we know that in certain cases, they can remain infectious.