Passage-attenuated Powassan virus LI9P protects mice from lethal LI9 challenge and links envelope residue D308 to neurovirulence.

Unlabelled: Powassan virus (POWV) is an emergent tick-borne flavivirus that causes lethal encephalitic disease and chronic neurologic deficits in surviving patients. POWV-LI9 is a tick-derived isolate that causes neurovirulent disease and age-dependent lethality in mice. Serial passage of VeroE6 cells infected with LI9 resulted in eight amino acid changes in a POWV strain LI9P.