D. Hayasaka et al., Distribution and characterization of tick-borne encephalitis viruses from Siberia and far-eastern Asia, J GEN VIROL, 82, 2001, pp. 1319-1328
In this study, tick-borne encephalitis (TBE) viruses from Siberia and far-e
astern Asia were characterized in order to determine virus subtype distribu
tion. TEE viruses were isolated from ticks (Ixodes persulcatus) collected i
n the far-eastern (Khabarovsk and Vladivostok) and Siberian (Irkutsk) regio
ns of Russia in 1999. Phylogenetic analysis showed that isolates formed dis
tinct clusters of far-eastern and Siberian subtypes, There was also a minor
difference in antigenicity between the Irkutsk isolates and other TEE viru
s strains, as demonstrated by the reactivity of monoclonal antibodies. Amin
o acid alignments of the E gene showed that the Irkutsk isolates had a sing
le amino acid change at position 234 (Q or H); this amino acid position is
considered to be a 'signature' of Siberian subtype TEE viruses. Strains iso
lated in Irkutsk also exhibited equivalent or somewhat higher virulence in
mice compared with far-eastern TEE virus isolates. All viruses isolated in
this study (i.e. far-east Asian and Siberian isolates) have 3 ' non-coding
regions (NCRs) of almost the same length, which contrasts with the various
sizes of 3 ' NCRs of other TEE viruses strains reported previously. The dat
a presented in this study show that the 3 ' NCR is uniform among TEE viruse
s isolated from Siberia and far-eastern Asia and that the 3 ' NCR is essent
ial for TEE virus growth in tick and/or rodent host cells.