[The properties of the particles formed in the reproduction of an acute in vitro infection with the tick-borne encephalitis virus adapted to H. plumbeum ticks]. / Svoistva chastits, formiruiushchikhsia pri vosproizvedenii ostroi infektsii in vitro virusom kleshchevogo éntsefalita, adaptirovannym k kleshcham H. plumbeum.

The properties of virions produced in pig embryo kidney (PEK) cells inoculated with tick-borne encephalitis (TBE) virus strain EK-328 which had been passaged in white mice and its variant obtained by passages of TBE in H. plumbeum ticks (clone 718/574 H. pl.17) were found to be different. The clone 718/574 H. pl17 virus particles had no hemagglutinating or precipitating activities, greater sedimentation and density heterogeneity in sucrose density gradient centrifugation, and differences in movements to electrodes in electrophoresis and immune electrophoresis. In mixed infection in PEK cultures with EK-328 strain and clone 718/574 H. pl17, the infective dose-dependent interference was observed which affected the infectious virus titre and the size of cathode antigen precipitate.

[Changes in the host-dependent characteristics of the tick-borne encephalitis virus during its adaptation to ticks and its readaptation to white mice]. / Izmenenie zavisimykh ot khoziaina kharakteristik virusa kleshchevogo éntsefalita pri ego adaptatsii k kleshcham i pereadaptatsiii k belym mysham.

Features of multiplication in pig embryo kidney (PEK) cells of a variant of tick-borne encephalitis (TBE) virus previously selected by passages in H. plumbeum ticks and changes in the properties of the variant upon its repassages in white mouse brains were studied. The tick-adapted TBE variant differed from the original strain in the following characteristics: a lower yield of infectious virus and physical virus particles, altered time-course of infectious virus release from the cell, the lack of virions moving towards cathode in rocket immunoelectrophoresis (RIEP), reduced hemagglutinating activity of the virus, small plaque size in PEK culture, reduced level of virus replication in white mouse brain at a high cytopathic activity of the virus, and low synthesis of virus particles moving towards anode in RIEP. The acquired characteristics were stable at the level of 3 passages in white mice. In the course of further readaptation to these animals the virus recovered its capacity for synthesis of "cathode" virions in PEK cell culture, differing from the original strain by a higher level of virus reproduction in mammalian cells, altered electrophoretic mobility of the structural virion protein V1, and plaque size.

[Action of tunicamycin on the infectivity and protein synthesis of the tick-borne encephalitis virus]. / Deistvie tunikamitsina na infektsionnost' i belkovyi sintez virusa kleshchevogo éntsefalita.

Tunicamycin added in concentrations of 0.5-1 microgram/ml into the maintenance medium with tick-borne encephalitis virus (TBE) propagated in PEK cell culture inhibited incorporation of labeled carbohydrates into glycoprotein V3 as well as into virus-specific proteins NV41/2, NV3, p22, p18, p13, and p12 and to a lower degree into proteins NV5 and NV4 irrespective of the time of its addition (immediately or 17 hours after virus adsorption on the cells). In the presence of tunicamycin, incorporation of radioactive amino acids into the intracellular virus-specific proteins was inhibited, and proteins with altered electrophoretic mobility appeared. Tunicamycin in doses of 0.5-1 microgram/ml added to the infected cells immediately after virus adsorption reduced the production of extracellular virus by 2 lg PFU/ml and of intracellular virus by 1 lg PFU/ml, but exerted no inhibitory effect on virus production when added 17 hours after infection. The results indicate that protein V3 and probably all other intracellular virus-specific proteins of TBE virus exist in PEK cells in N-glycosylated form, tunicamycin selectively inhibits the stage of glycosylation of virus-specific proteins, and glycosylation of proteins affects the infectious properties and virus release from the cell.

[Immunochemical characteristics of the antigens of a variant tick-borne encephalitis virus adapted to Hyalomma plumbeum ticks]. / Immunokhimicheskie kharakteristiki antigenov varianta virusa kleshchevogo éntsefalita, adaptirovannogo k kleshcham Hyalomma plumbeum.

A comparative study of immunochemical properties of a preparation of the virion antigen of a variant of tick-borne encephalitis (TBE) virus adapted to H. plumbeum ticks (clone 718/574) and the parental TBE strain revealed the following features: (1) immunoelectrodiffusion test revealed no immunoprecipitation rockets directed towards cathode in the clone 718/574 preparation; anodic precipitates differed in shape from those of the parental strain; (2) diffuse precipitation in agar showed a reaction of incomplete identity between the virion antigen of clone 718/574 and the parental strain antigen, the clone 718/574 antigen forming only one precipitation band in contrast to two precipitation bands of the parental strain; (3) immune electron microscopy demonstrated a peculiar nature of the halo-overlay by immunoglobulins of clone 718/574 virions differing from that of the parental strain.