15 January 2010

Antiviral drugs could create "super viruses"

by Kate Melville

Recent widespread flu scares have seen a clamor for antiviral medications, but researchers from the University of Texas at Austin (UT) have raised serious concerns about stopping viral infections in this way. According to their research, appearing in the journal GENETICS, medications that kill viruses by forcing their nucleic acid to mutate rapidly might actually, in some instances, cause them to emerge from the process stronger and even more virulent.

"This work questions whether the practice of 'lethal mutagenesis' of viruses works as predicted," said UT researcher Jim Bull. "It remains to be seen whether an elevated mutation rate that does not cause rapid viral extinction enhances treatment or may instead thwart treatment by enhancing viral evolution."

The researchers tested the model of viral evolution at high mutation rates by growing a DNA virus in the presence of a mutagenic agent. The current accepted model predicted that the virus would not be able to handle the high mutation rates and would eventually die off. However, this model was proved false, as the virus actually increased its fitness at elevated mutation rates.

The scientists found molecular evidence that the rapid mutations had two effects. The first effect of most mutations, which was expected, was that they killed or weakened the virus. The second effect of some mutations, however, was that they actually helped the virus adapt and thrive. Although the researchers did not question that extremely high mutation will lead to viral extinction on the whole, this discovery raises the specter that forcing viruses to undergo rapid mutations could, if the mutation rate is not high enough, accidentally lead to well-adapted "super viruses."

"This study should raise more than a few eyebrows over this approach to stopping viruses," noted Mark Johnston, Editor of GENETICS, "because the last thing anyone wants to do is make a bad situation worse. More work must be done to determine the actual likelihood of this approach yielding a super virus."

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Source: Genetics Society of America