Comparative analysis of European subtype tick-borne encephalitis virus strains isolated from patients from Eastern Siberia and Eastern and Northern Europe

Background. Isolation of strains from tick-borne encephalitis (TBE) patients proved that the European subtype tick-borne encephalitis virus (TBEV-Eur) in Siberia is involved in regional human infectious pathology and causes a clinical picture similar to Western TBE. However, a comparative analysis of the genomes of TBEV-Eur strains isolated from TBE patients in Eastern Siberia and Europe has not been carried out.
The aim. Genome comparative analysis and search for virulence determinants in TBEV-Eur strains isolated from patients in Eastern Siberia and Northern and Eastern Europe.
Materials and methods. In current work, TBEV-Eur strain 1G-98 from the collection of Scientific Сentre for Family Health and Human Reproduction Problems (GenBank Acc. No. KY069119) was used. The analysis also included all complete genome sequences of TBEV-Eur strains from patients submitted in GenBank database at the time the study began. Complete genome sequencing of strain 1G-98 was performed using the Sanger method. The virulence of the strain was assessed by intracerebral and subcutaneous infection of laboratory mice.
Results. It has been shown that, according to the coding region of the genomes, the level of differences between TBEV-Eur strains from Siberia does not exceed the previously established maximum for this subtype of 3.1 %. The strain 1G-98, isolated from the blood of TBE patient from the Irkutsk region demonstrated high cerebral and peripheral activity. In this strain, D67G mutation in E protein DII domain was revealed, which could potentially be associated with virulence, and a long deletion in the variable part of the 3’-noncoding genome region, comparable in length to the highly virulent strain Hypr from Europe was found.
Conclusions. For the first time, a comparative analysis of the genomes of TBEV-Eur strains from TBE patients from the Asian part of Russia and Europe was carried out showing their genetic similarity, and potential virulence determinants were identified. Key words: tick-borne encephalitis virus, European subtype, genome, amino acid sequence, virulence determinants

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