Certain (RNA) viruses that copy their genome too accurately are less infectious than normal viruses, researchers report online this week in Nature. This proves that viruses need to make a certain number of mistakes when copying their genome. Raul Andino and colleagues also show that the infectiousness of a virus is not determined by a single strain. Instead, a virus exists in its host as a group of related sequences or variants. These variants cooperate and need a certain degree of diversity to adapt to different conditions in the infected host, the researchers say.
The team isolated a poliovirus that makes more exact copies of its genome than normal viruses, and found that it was less virulent in infected mice. When the researchers used a chemical to reintroduce errors in the poliovirus genome, the original virulence of the virus was restored.
These results have implications for the development of antiviral drugs that introduce errors into the genome. Such drugs work because too many errors in a virus genome are just as bad as too few. However, viruses resistant to this type of drug typically make too few errors to start with. On the basis of their research, the authors suggest that such drug-resistant viruses would be less virulent and therefore more susceptible to other types of antiviral drugs then normal viruses.
Raul Andino (University of California at San Francisco, CA, USA)
Abstract available online.
(C) Nature press release.
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