Features of Reproduction of Tick-Borne Encephalitis Virus in a New Cell Line of the Siberian Bat Myotis sibiricus (Kastschenko, 1905)

Background. Tick-borne encephalitis virus (TBEV) in nature exists due to the constant circulation between vertebrate animals and tick viruses. To study the characteristics of reproduction of TBEV in the cells of vertebrate hosts of various species, it is necessary to simulate infection in the cell lines of both natural and accidental hosts of TBEV.

Aim. To study the possibility of reproduction of TBEV in the cell line of the kidney of Siberian bat Myotis sibiricus (Kastschenko, 1905) – an accidental host of the virus.

Materials and methods. The cell line of Siberian bat M. sibiricus was established by serial passages of primary culture of kidney cells. The SPEV line porcine kidney cells were used as reference. Cells were infected with a strain of TBEV of the Siberian subtype 92M and both cells and cell culture fluids were sampled every 2 hours during first 24 hours post infection. In addition, the samples were collected daily up to 5 days post infection. Evaluation of the amount of intracellular RNA of TBEV of positive polarity (+RNA) was performed  using quantitative real-time PCR. The concentration of infectious TBEV was evaluated using the method of titration TBEV on plaque forming units.

Results. The continuous cell line, designated as MdbK, was established from the kidney cell suspension of M. sibiricus and was used for experiments after 20 serial passages. MdbK cells were able to support the replication of TBEV RNA and production of infectious virus was also possible. The concentration of intracellular RNA had reached 9.1 lg copies/μl by day 3 post infection, whereas highest titer of infectious TBEV in cell culture fluid had comprised 5,5 PFU/ml and was detected by day 4. The concentration of intracellular RNA and the virus infectivity in MdbK cell line was significantly lower than in convenient SPEV line porcine kidney cell.

Conclusions. The results suggest the low fitness of TBEV to the intracellular environment of an accidental host. 

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