Some 90 percent of people are infected with the herpes simplex virus type 1 that causes cold sores, but a much smaller percentage actually get the sores. Jürgen Haas from the University of Edinburgh and Ludwig-Maximilians University Munich and his colleagues report in PLOS Pathogens that those who experience effects of infection typically have a SNP in the IFN-λ3, or IL28B, promoter.
Using both a yeast two-hybrid and an RNAi screen, Haas and his team uncovered a number of host factors that influence HSV-1 infection. One factor, Med23, appears to induce an antiviral response through type III interferons like IFN-λ. This indicated to the researchers that mutations in IFN-λ may affect control of HSV-1 infections. They then found a correlation between that IFN-λ3 promoter SNP and severity of recurrent HSV-1-related cold sores.
HSV-1 infection can lead to other maladies, including meningitis and encephalitis, and Haas tells the New York Times that his team's finding may inform treatment of those conditions. "In cold sores you can use acyclovir," he says to the Times, "but the same virus also causes more severe infections of the brain, the eyes, and the genital tract." In those instances when the commonly used acyclovir isn't effective, Haas says that a treatment involving IL28B could be a possibility.