RNA Polymerase Mutation Stabilizes Live Virus Vaccines

To establish stable, attenuated mutant strains that could be used for vaccination without danger of back mutation reestablishing full viral pathogenicity, the investigators introduced mutations into the RNA-dependent RNA polymerase.

They reported in the July 1, 2016, issue of The Journal of Biological Chemistry that they had exchanged a phenylalanine molecule in the RNA polymerase with tryptophan. The tryptophan residue caused the polymerase to make fewer mutations, and this reduced the ability of the virus to replicate and cause disease. Back mutations prevented the virus from replicating at all, resulting in its elimination from the host organism.

"We think it is going to work, but we have to show that it will," said senior author Dr. Olve Peersen, professor of biochemistry and molecular biology at Colorado State University. "Trying to outsmart Mother Nature is pretty daunting, especially in these viruses. There are ways that things happen you never anticipate, and the virus finds a way to survive."

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