First complete genomic characterization of two tick-borne encephalitis virus isolates obtained from wild rodents in South Korea

Abstract

We determined for the first time the complete genome sequences of two Korean strains of the tick-borne encephalitis virus (TBEV), designated KrM 93 and KrM 213, isolated from the lung tissues of wild rodents in 2006. The genomes are 11,097 nucleotides (nt) in length and consist of a 132 nt 5'-noncoding region (NCR), a 10,245nt open reading frame (ORF) containing 10 viral protein-coding regions (3,415 amino acids), and a 720nt 3'-NCR. Compared with the 31 fully sequenced TBEV strains currently available, KrM 93 and KrM 213 show genomic nucleotide (and deduced amino acid) sequence divergences ranging from 1.8 (0.7) to 19.2 (26.6)% and 1.9 (0.8) to 19.3 (26.7)%, respectively. Phylogenetic and recombination analyses based on the complete genome sequence were performed to identify genetic variations and relationships between the TBEV strains. These showed that the Korean TBEV strains clustered with the Western subtype rather than with Far-Eastern or Siberian subtypes, and phylogenetic trees derived from capsid (C), envelope (E), nonstructural (NS) 4B and NS5 regions represented the same branching pattern shown by the complete genome-based tree. Although no recombination events were identified in these two Korean strains, 11 putative recombination events were identified within the NS5 regions or in the 3'-NCRs of TBEV strains in general. The results provide insight into the genetics of TBEV strains to understand the molecular epidemiology, genetic diversity, and evolution of TBEV.