Nucleotide sequencing and serological evidence that the recently recognized deer tick virus is a genotype of Powassan virus

Deer tick virus (DTV) is a recently recognized North American virus isolate d from Ixodes dammini ticks. Nucleotide sequencing of fragments of structur al and non-structural protein genes suggested that this virus was most clos ely related to the tick-borne flavivirus Powassan (POW), which causes poten tially fatal encephalitis in humans. To determine whether DTV represents a new and distinct member of the Flavivirus genus of the family Flaviviridae, we sequenced the structural protein genes and 5 ' and 3 ' non-coding regio ns of this virus. In addition, we compared the reactivity of DTV and POW in hemagglutination inhibition tests with a panel of polyclonal and monoclona l antisera, and performed cross-neutralization experiments using anti-DTV a ntisera. Nucleotide sequencing revealed a high degree of homology between D TV and POW at both nucleotide (> 80% homology) and amino acid (> 90% homolo gy) levels, and the two viruses were indistinguishable in serological assay s and mouse neuroinvasiveness. On the basis of these results, we suggest th at DTV should be classified as a genotype of POW virus. (C) 2001 Elsevier S cience B.V. All rights reserved.