Molecular-genetic characteristics of the tick-borne encephalitis virus pathogenicity of far eastern subtype

The aim of the work: Using the data of genome-wide sequencing of tick-borne encephalitis virus strains of the Far Eastern population, reveal the peculiarities of the moleculargenetic characteristics and their relationship with the pathogenicity of the agent.

Materials and methods. A full-genomic characteristic of 63 TBEV strains isolated in the Far East and registered in GeneBank wos given. A pathohistological study of the central nervous system of monkeys infected with the highly virulent strains Sofjin and Khabarovsk-17 TBEV was conducted.

Results. All strains are assigned to the Far Eastern subtype of TBEV and are located in three clusters, the territorial attachment of individual strains groups is noted. In the cluster of Sofjin-like strains, independent groups were identified, isolated in the territories of Primorsky Krai only, and separate groups – only in northern focal territories (Khabarovsk Krai). The cluster Senzhang-like strains are represented by strains of different clusters, isolated in China and throughout the Far East. The Oshima-like cluster of strains, except for strains from Japan, consists of strains isolated only in the south of the Far East (in Primorsky Krai). The incubation period of the disease in experimental animals was shorter when infected with the Sofjin strain (3–5 days) than when infected with the Khabarovsk-17 strain (7 days or more). The strain-specific differences in the severity of morphological changes in the central nervous system were revealed. For primorsky TBEV strains, a higher degree of neuroinvasiveness was characteristed with a more rapid development of severe manifestations of neuroinfection, compared to khabarovsky strains.

Findings: 1) based on full-genome sequencing and phylogenetic analysis of 63 TBEV strains, three main clusters were distinguished: Sofjin-, Senzhang- and Oshima-like; 2) in these clusters, territorial attachment of TBEV strains groups with a certain molecular genetic characteristic was established; 3) in primorsky TBEV strains, genetically determined advantages in the degree of neuroinvasiveness have been revealed, which provide them with the ability to more quickly overcome the blood-brain barrier compared to khabarovsky strains.

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