[Tick-borne encephalitis virus as an amplifier of the metamorphosis of Ixodes ricinus (Acari: Ixodidae) tick nymphs under long-day photoperiodic conditions].

The metamorphosis of tick-borne encephalitis virus (TBEV)-induced I. ricinus nymphs under long-day photoperiodic conditions (18 light hours and 6 darkness hours) occurs more rapidly than in uninfected specimens. The infected nymphs begin to develop to the imagoes 25-33 days earlier than do uninfected ones. The first imagoes from the infected nymphs emerge on day 24 after saturation whereas those from the uninfected nymphs appear on day 43. The interval from nymphal saturation to imago development in 50% specimens is 27.7 +/- 2.0 and 52.2 +/- 0.7 days, respectively. Reasons for geographical differences in the intensity of amplification of the metamorphosis of saturated I. nicinus nymphs are discussed in the paper.

[Demonstration of the tick-borne encephalitis virus by a solid-phase immunoenzyme method in materials from natural foci]. / Indikatsiia virusa kleshchevogo éntsefalita tverdofaznym immunofermentnym metodom v materialakh prirodnykh ochagov.

Large-scale examinations of specimens from natural foci of tick-borne encephalitis (TBE) demonstrated that sensitivity of solid-phase enzyme immunoassay (EIA) in detecting TBE virus antigen was as high as that of the fluorescent antibody technique. The EIA takes less time and may be used for examinations of specimens after a preliminary passage in cell cultures. The EIA was also shown to be highly effective in the detection of TBE virus antigen in the cerebral tissue of patients post mortem and in the confirmation of the clinical diagnosis.

[Multi-year observations of the humoral immunity status of patients with tick-borne encephalitis in 3 endemic regions]. / Mnogoletnie nabliudeniia za sostoianiem gumoral'nogo immuniteta u bol'nykh kleshchevym éntsefalitom v trekh éndemichnykh regionakh.

Analysis of the results of the laboratory diagnosis of tick-borne encephalitis (TBE) by HI test over many years proved a statistically significant decrease by the 80's in the intensity of humoral immunity in the subjects with a history of tick-borne encephalitis in Kemerovo Province, Udmurtia and Latvia. A decrease in antihemagglutinin levels in the blood of convalescents after TBE was detected in endemic foci located in different geographical regions differing by epidemiological parameters; it did not depend on the portion of infected ticks and ratio of the clinical forms of the disease in a focus. Parallel tests by HI of the diagnostic value of several antigens of TBE virus strains isolated from different sources in different regions with sera from TBE patients revealed no differences among them. The antigenic activity of the strains in HI test did not depend on the source and region of isolation (Kemerovo Province, Udmurtia and Latvia).

[Biological properties of tick-borne encephalitis strains isolated in different parts of its geographic range]. / Izuchenie biologicheskikh svoistv shtammov virusa kleshchevogo éntsefalita, vydelennykh v raznykh chastiakh ego areala.

A comparative study of over 200 tick-borne encephalitis (TBE) virus strains isolated from patients and ticks in different regions varying in the proportion of severe clinical forms of TBE was carried out. The strains were tested for their pathogenicity for white mice, cytopathic and plaque-forming properties as well as for the interferon-inducing capacity in SPEV cells. All the strains were found to be highly neurovirulent for mice, to produce plaques with diameters varying form less than 1 to 10 mm, and to induce interferon production in SPEV cell. Among the TBE virus strains isolated in the Baltic republics and Vologda region there occurred strains causing complete destruction of SPEV cells at later intervals than the prototype strains. No association of the examined properties of TBE virus strains with the region of isolation or with the clinical forms of human disease was established.

[A comparison of the protective properties of preparations of the virion and nonvirion ("soluble") antigens of the tick-borne encephalitis virus]. / Sopostavlenie protektivnykh svoistv preparatov virionnogo i nevirionnogo ("rastvorimogo") antigenov virusa kleshchevogo éntsefalita.

A comparative assessment of the protective properties of virion (VA) and nonvirion ("soluble") (NA) antigens of tick-borne encephalitis virus prepared as inactivated samples close in their parameters to vaccine preparations was carried out. The NA in the preparations free from VA or containing only trace, nonprotective amounts of it, was shown to have significantly lower protective properties than VA and exerted no booster effect on the protective activity when added to VA preparations.

[Immunoenzyme method in the diagnosis of tick-borne encephalitis]. / Immunofermentnyi metod v diagnostike kleshchevogo éntsefalita.

Data are presented on the use of direct and indirect enzyme-immunoassay (EIA) in the study of tick-borne encephalitis (TBE) virus. EIA has been shown to be considerably more effective than the conventional CFT and HI tests exceeding them in sensitivity by 50-150 times both in studies of the antigenic activity of various preparations and in examinations of human sera. The possibility of testing various antigenic substrates makes EIA a universal method suitable for numerous studies. The high sensitivity of the method is useful for antigenic differentiation of viruses and strains within the TBE complex. The EIA may be used satisfactorily for early diagnosis of TBE and study of seroconversion in vaccines.

GAG-binding variants of tick-borne encephalitis virus.

Previously different authors described various flavivirus mutants with high affinity to cell glycosaminoglycans and low neuroinvasiveness in mice that were obtained consequently passages in cell cultures or in ticks. In present study the analysis of TBEV isolates has shown existence of GAG-binding variants in natural virus population. Affinity to GAG has been evaluated by sorption on heparin-Sepharose. GAG-binding phenotype corresponds to such virus properties, like small plaque phenotype in PEK cells, absence of hemagglutination at pH 6.4, and low neuroinvasiveness in mice. Mutations increasing charge of E protein were necessary but not sufficient for acquisition of GAG-binding phenotype. Molecular modeling and molecular dynamics simulation have shown that the flexibility of E protein molecule could bear influence on the phenotypic manifestation of substitutions increasing charge of the virions.