A highly virulent strain (Hypr) of tick-borne encephalitis virus (TBEV) was serially subcultured in the mammalian porcine kidney stable (PS) and Ixodes ricinus tick (IRE/CTVM19) cell lines, producing three viral variants. These variants exhibited distinct plaque sizes and virulence in a mouse model. Comparing the full-genome sequences of all variants, several nucleotide changes were identified in different genomic regions. Furthermore, different sequential variants were revealed to co-exist within one sample as quasispecies. Interestingly, the above-mentioned nucleotide changes found within the whole genome sequences of the new variants were present alongside the nucleotide sequence of the parental strain, which was represented as a minority quasispecies. These observations further imply that TBEV exists as a heterogeneous population that contains virus variants pre-adapted to reproduction in different environments, probably enabling virus survival in ticks and mammals.

Department of Virology Veterinary Research Institute 62100 Brno Czech Republic

Faculty of Science University of South Bohemia in České Budějovice 37005 České Budějovice Czech Republic

Institute of Infection Veterinary and Ecological Sciences University of Liverpool Liverpool L3 5RF UK

Institute of Parasitology Biology Centre of the Czech Academy of Sciences 370 05 České Budějovice Czech Republic

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Evaluation of two artificial infection methods of live ticks as tools for studying interactions between tick-borne viruses and their tick vectors

History of Arbovirus Research in the Czech Republic