Viruses infect a wide range of plants and animals, and shows that they can even infect one another. If that seems surprising, no wonder: until a team of French researchers watched one virus invade another, hijacking its genetic machinery and making copies of its victim’s DNA, scientists didn’t even know this was possible.
The French team dubbed the virus’s virus Sputnik and called it a “virophage” to parallel “bacteriophage,” which is the name for a virus that infects bacteria. Sputnik is tiny, with only 18,000 genetic bases in its chromosome. Its victim, by contrast, is a large mamavirus that the scientists found in a Paris cooling tower, and contains about 1.2 million genetic bases. An infection by Sputnik sickens the mamavirus by interfering with its replication.
The discovery that even viruses can fall ill has reignited an old controversy—whether viruses are are actually alive or simply rogue bits of DNA that depend upon other organisms to reproduce. “There’s no doubt this is a living organism,” says Jean-Michel Claverie, a virologist at the the CNRS UPR laboratories in Marseilles, part of France’s basic-research agency. “The fact that it can get sick makes it more alive”.
And now that they know viruses can infect other viruses, the researchers say it could be possible to use virophages against the most harmful viruses, although they’re cautious about the idea. “It’s too early to say we could use Sputnik as a weapon against big viruses or to modify them,” says co-author Bernard La Scola, also at the University of the Mediterranean. “But phages are used to modify bacteria, so why not?”.