The tick-borne encephalitis virus (TBEV) is transmitted by ixodes ticks and cause severe neuroinfections in human.
The regions endemic for the TBEV are expanding, and the prevalence of tick-borne encephalitis (TBE) is also rising. This disease is notifiable in Russia since 1944. Since September 2012, TBE is notifiable in the European Union.
According to the official classification, TBEV as a species is subdivided into three diversified and epidemiologicaly important subtypes, namely the Far East, the Siberian and the European. These subtypes correspond to three genotypes designated in the same way: (1) the Far East with the prototype strain Sofjin); (2) the Western with the prototype strain Neudoerfl; and (3) Siberian or Ural-Siberian with the prototype strain Vasilchenko.
Several other genetic variants of TBEV have been also found. They include genotypes 4 (represented by the only strain 178-79 from Eastern Siberia) and 5 (a group of strains analogous to the strain 886-84, which have been isolatedin Russia and Mongolia), as well as a recently discovered Himalayan group (two whole-genome isolates). These findings, regardless of what they mean for the epidemiology of TBE, highlight the necessity to reconsider the accepted classification of TBE.
The goal of the present study is to assess the genetic variability of TBEV markers and find genotype-specific markers based on the analysis of the materials available from the international database (GenBank).
Comparison of polypeptide structures of strains and isolates of viral RNA of TBEV from different sources in Europe and Asia allowed us to find genotype-specific combinations of amino acid substitutions.
All nucleotide sequences deposited so far fall into one of the described genetic groups.The natural sources of TBE located in Russia contain the highest genetic diversity of TBE. Five out of six known genetic groups of this virus were found here.
Strains Buzuuchuk from Kyrgyzstan and 178-79 from Russia (Eastern Siberia) possess unique genomic structures.
The Buzuuchuk strain from Kyrgyzstan turned out to be an untypical representative of genotype 3, as it does not follow the differentiation into three subclusters (the Baltic branch and subgenotypes Vasilchenko and Zausaev from the Siberian branch).
The strain 178-79 is the only known representative of the proposed genotype 4. The unusual structure of its genome is probably the combination of loci characteristic for the major TBEV genotypes.
In 1987, after graduation from the Irkutsk State University, Tatiana Demina was directed to the laboratory of genosystematics in the Limnological Institute, where she as a research assistant studied the methods of molecular biology and participated in the expeditions on Lake Baikal.
Starting from 1991, she worked as a scientific fellow in the laboratory of viral genetics in the Irkutsk Research Institute of Epidemiology and Microbiology.
In 1999, she defended the Cand. Sci. (PhD) thesis entitled ‘Characteristic of the genetic variability of tick-borne encephalitis virus strains based on homology analysis of regions of the viral genome.’
From 2003 to February 2011, she continued the experimental studies of the TBEV genomes.
In 2013, she defended the D. Sci. dissertation entitled ‘The issues of genotyping and genetic variability of tick-borne encephalitis virus.’
Starting from September 2013, she taught a lecture course entitled ‘Veterinary microbiology’ as a visiting professor at one of the departments of the School of Biotechnology and Veterinary medicine at the Irkutsk State Agrarian Academy. Since 2013, she holds a permanent professor position at one of the departments of the School of Biotechnology and Veterinary medicine at the Irkutsk State Agrarian University.