A viral twist: Replacing certain genetic fragments in poliovirus might hold promise Credit: Dr. Dennis Kunkel

Languages abound with synonyms, and people often show preferences for one word over another. Some say 'smart' and others 'sharp' or 'intelligent', but they all mean the same thing. Viruses also have a penchant for certain synonyms, and exploiting these preferences could potentially lead to a new generation of vaccines.

The genetic code consists of three-letter words called codons that specify the amino acids used to build proteins. Typically, more than one codon encodes the same amino acid; for example, GCU, GCC, GCA and GCG are all 'synonymous' codons that represent the amino acid alanine.

Researchers have previously engineered weaker versions of the poliovirus by replacing the virus's favorite codons with its least favorite synonyms (J. Virol. 80, 3259–3272; 2006). The disliked codons seem to act as speed bumps, slowing the rate at which the virus translates its genetic code into protein and makes copies of itself.

A team of computer scientists and molecular biologists from Stony Brook University in New York has now used a similar approach to design weakened versions of poliovirus that seem to act as vaccine (Science 320, 1784–1787; 2008). When injected into mice, the engineered viruses helped the animals develop immunity against a normally lethal dose of regular poliovirus.

“We're very interested in trying this in other viruses,” says study co-author Steffen Mueller, noting that the approach could potentially be safer and faster than that used for current live vaccine production, which typically requires hazardous starting material (the pathogenic virus).