Sequence analysis and genetic classification of tick-borne encephalitis viruses from Europe and Asia.

TLDR

The epidemiology of tick‑borne encephalitis virus was investigated by comparative sequence analysis of strains isolated in endemic areas of Europe and Asia. Phylogenetic relationships were inferred from nucleotide and amino‑acid sequences of the envelope protein of 16 newly sequenced strains and nine previously published ones. Three distinct genetic lineages—European, Far Eastern, and Siberian—were identified, with subtype‑specific signature amino acids mapped to the envelope protein structure, and intra‑subtype variation was low (≤2.2%) while inter‑subtype differences reached 5.6%, comparable to other flaviviruses.

Abstract

The epidemiology of tick-borne encephalitis virus was investigated by comparative sequence analysis of virus strains isolated in endemic areas of Europe and Asia. Phylogenetic relationships were determined from the nucleotide and amino acid sequences of the major envelope (E) protein of 16 newly sequenced strains and nine previously published sequences. Three genetic lineages could be clearly distinguished, corresponding to a European, a Far Eastern and a Siberian subtype. Amino acids characteristic for each of the subtypes ('signature' amino a cids) were identified and their location in the atomic structure of protein E was determined. The degree of variation between strains within subtypes was low and exhibited a maximum of only 2.2% at the amino acid level. A maximum difference of 5.6% was found between the three subtypes, which is in the range of variation reported for other flaviviruses.