First 'virophage' could take the fight to viruses - health - 06 August 2008 - New Scientist
http://www.newscientist.com/article/dn14480-first-virophage-could-take-the-fight-to-viruses.html 'virophage' could take the fight to viruses 18:00 06 August 2008 by Nic Fleming A newly discovered type of virus that spreads at the expense of other viruses, could be used to combat viral infections, say researchers. Didier Raoult and colleagues from the University of the Mediterranean, France, say that the virus, called Sputnik, spreads by hijacking the replication machinery of the mamavirus - itself a new strain of the giant mimivirus. The team says Sputnik is the first member of a new class they call "virophages" because of similarities with bacteriophages or phages - viruses that infect bacteria - and is the first time a virus has been seen to propagate at the expense of a viral host. Research into phage therapy during the early 20th century was largely abandoned following the discovery of antibiotics. Virus weapon? Not only does Sputnik cut the spread of mamavirus in amoeba, Raoult's analysis also shows it has looted genes from other viruses. This could help researchers understand the genetic evolution of harmful viruses, and potentially, use virophages to destroy them. However, the team is cautious. "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?" Sputnik resembles satellite viruses - such as the one that causes hepatitis D. These can only replicate in and infect their host if another virus is present. A key difference, though, is that Sputnik significantly reduces the viral load of the other virus. "What is interesting here is that Sputnik is doing this at the expense of the bigger virus," says Robin Weiss, of University College London. However Geoffrey Smith, a virologist at Imperial College London, says this may not be surprising since both viruses are dependent upon the host cell for metabolites and will compete for them. He adds: "Bacteriophages replicate only in bacteria and that's all they need, so the use of the phrase 'virophage' is inappropriate." Journal reference: Nature (DOI: 10.1038/nature07218)
