Some antiviral drugs could make diseases worse

Some antiviral drugs can make viruses stronger instead of killing them, a new study claims.

Researchers from the University of Texas at Austin insist that in some cases medications that cause viruses to die off by forcing their nucleic acid to mutate rapidly might actually strengthen them, making the patient's condition worse.
 
As part of the study, scientists tested the model of viral evolution at high mutation rates by growing a DNA virus in the presence of a mutagenic agent.

Generally, virus are not able to handle the high mutation rates and hence die off.

But, in this case the virus actually increased its fitness at elevated mutation rates.

Scientists found molecular evidence that rapid mutations had two effects.

The first effect of most mutations killed or weakened the virus, while the second effect of some mutations, helped the virus adapt and thrive.

They reached the conclusion that if the mutation rate is not high enough, the treatment can accidentally lead to well-adapted "super viruses."

Jim Bull, PhD, a researcher from the Institute for Cellular and Molecular Biology at the University of Texas at Austin, said: "This work questions whether the practice of 'lethal mutagenesis' of viruses works as predicted.

"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."

Also, Mark Johnston, editor-in-chief of the journal GENETICS, said: "This study should raise more than a few eyebrows over this approach to stopping viruses.

"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, knowing that it is possible is a big help in preventing what could be a very big problem."

The study has been published in the January 2010 issue of the journal GENETICS.