Atomic-resolution structure of a chimeric Powassan tick-borne flavivirus.

Powassan virus (POWV) is an emerging tick-borne flavivirus for which no vaccine or antiviral treatment exists. The incidence of human infections of POWV in North America has been increasing because of the expanding distribution of the tick vector that transmits POWV to humans. To mitigate the dangers of handling a risk group 3 human pathogen, a chimeric virus was constructed from the genetic backbone of a yellow fever virus vaccine strain 17D (YFV-17D) and the external structural proteins of POWV lineage II. The chimera had a comparable phenotype as POWV. The atomic resolution of yellow fever virus-Powassan virus chimera (yPOWV) structure was built without ambiguity, revealing surface glycans and lipid pocket factors. The similarity to other flavivirus structures and the phenotype similar to YFV-17D suggest that there could be future potential as a vaccine candidate.