[Specific determination of flaviviruses by molecular hybridization with synthetic deoxyoligonucleotide probes]. / Spetsificheskoe opredelenie flavivirusov metodom molekuliarnoi gibridizatsii s sinteticheskimi dezoksioligonukleotidnymi zondami.

Molecular probes were designed for the purpose of specific determination of flavioviruses transmitted by the ticks of tick-borne encephalitis (TBE) and Omsk hemorrhagic fever (OHV) as well as by mosquitoes of Japanese encephalitis (JE), North Nile (NN), Murrey Valley encephalitis (MVE), Saint-Lois encephalitis (SLE), dengue 1-4 and of yellow fever (YF). The probes are synthetic deoxyoligonucleotides with the 18-20 long basis and complementary for the RNA fragments defined by computer analysis. The thus obtained probes, which specifically hybridize themselves with the sets of the TBE virus or of the OHV virus and do not hybridize themselves with other TBE viruses' sets. Group-specific probes for YE and dengue viruses as well as virus-specific probes, which are able to detect each of the above viruses without any cross effects, were suggested for indexing and identifying the flaviviruses transmitted by mosquitoes.

[The Hydrachnidae water mites of southwestern Siberia in relation to their participation in arbovirus circulation]. / Vodianye kleshchi Hydrachnidae iuga Zapadnoi Sibiri v sviazi s ikh uchastiem v tsirkuliatsii arbovirusov.

The phenomenon of Hydrachnidae association with the tick-borne encephalitic viruses complex has been found out during the study of the role of the Hydrachnidae in the arboviruses circulation. We investigated the fauna, studied the quantity variation and trophic relations of these arthropods and blood-sucking Diptera. It was revealed no trophic relations between blood-sucking Diptera and mite species, where TBE strains were isolated from. On the basis of faunistic and virological study we suppose, that Hydroacarinae got an infection with the virus in the nymphal and imago stages, as well as larvae of mosquitos. Authors also note, that trophic relations between blood-sucking Diptera and chiggers (Trombidiidae) may be important in the arboviruses ecology.

[Influence of host-effect on strain variability of tick-borne encephalitis virus]. / K voprosu o vliianii host-éffekta na shtammovuiu izmenchivost' virusa kleshchevogo éntsefalita.

The organism of arthropods and warm-blooded vertebrates as a habitat of a virus determines the population genetic structure of tick-borne encephalitis (TBE) virus strains. The pattern of hybridization by variable zones of TBE genomes gradually changes in the course of intracerebral passages of the virus in newborn white mice. During intracelomal passages in Ixodidae hybridization alters as early as during the first passage, both for variable and (in individual cases) conservative zones. Ixodid ticks should be regarded as a mechanism maintaining the heterogeneity of virus communities (strains and populations). Vertebrates and communities of dugout arthropods appear to be the mechanism reducing the effect of ecologic isolation of TBE strains.

[Genomic changes in strains of the tick-borne encephalitis virus as a result of passages in mice]. / Izmenenie genomov shtammov virusa kleshchevogo éntsefalita v rezul'tate passazhei na myshakh.

Changes in genomes of TBE strains isolated from various sources at early stages of laboratory adaptation to white mice brain were demonstrated by molecular hybridization of nucleic acids with synthetic oligonucleotide probes, complementary RNA sites of reference TBE strains Sofyin and Neudorf. Of the 4 TBE strains passed 6 times through white mice brain in only 1 the level of RNA hybridization with 2 oligonucleotide probes was found changed, whereas in all the 3 tested strains the level of RNA hybridization with 1-2 oligonucleotide probes complementary to strain Sofyin was increased after 7-16 passages in the same system. The most noticeable changes in the genome were detected during readaptation to white mice of a TBE variant selected in passages on H. marginatum marginatum ticks.

[The genetic characteristics of the Vergina serotype of the tick-borne encephalitis virus and its pathogenetic traits]. / Genetichskaia kharakteristika serotipa Vergina virusa kleshchevogo éntsefalita i osobennosti ego patogennosti.

The Greek Vergina strain of tick-borne encephalitis (TBE) virus was studied in comparison with 7 other strains by molecular hybridization of nucleic acids and by clinicomorphological markers of pathogenicity for monkeys and Syrian hamsters. By the genetical features the Vergina strain differed from the eastern and western TBE subtypes but was found to be similar to the strains of other subtypes of the Urals-Siberian, east-Siberian (Aina-1448) and Central Asian antigenic variant. This group of strains hybridized with cDNA at 65 degrees C only in the absence of 50% formamide, reacted with probe 1115 complementary to protein E gene, with 1-3 probes complementary to the conservative region of the genome but did not react with the probes corresponding to the variable regions of the genome. The Vergina strain is close to TBE genotype III. The Vergina strain was found to be virulent inducing subacute meningoencephalomyelitis which developed slowly and was accompanied by less marked morphological lesions in the cerebral cortex than those induced by the eastern subtype. The Vergina strain was demonstrated to persist in the brain, liver, spleen, and lymph node tissues.

[The specific reactivity of cDNA and deoxyoligonucleotide probes, complementary to the tick-borne encephalitis virus genome, with the RNA of strains of different geographical origins]. / Spetsificheskaia reaktivnost' kDNK- i dezoksioligonukleotidnykh zondov, komplementarnykh genomu virusa kleshchevogo éntsefalita, s RNK shtammov razlichnogo geograficheskogo proiskhozhdeniia.

Hybridization experiments with RNA of 143 tick-borne encephalitis (TBE) virus strains isolated in different parts of the distribution area were used to study the reactivity of kDNA- and a set of 10 synthetic deoxyoligonucleotide probes. The kDNA probe under certain conditions was shown to hybridize with RNA of all the strains under study, and under other (strict) hybridization conditions did so selectively with a small number of strains. The capacity of oligonucleotide probes for hybridization with RNA of TBE virus strains varied from 12% to 100%. The differences in the hybridization activity of kDNA- and oligonucleotide probes complementary to the genomes of the Sophyin strain (Far-Eastern subtype) and Neudorffle strain (Western subtype) with TBE virus strains were used for differentiation of the strains into six genetic variants. Comparison of the reactivity of molecular probes in experiments with RNA of TBE virus strains and viruses of the TBE complex showed that the differences of the strains belonging to different genetic variants from the prototype Sophyin strain were comparable to those of some members of the TBE complex, with the exception of Powassan virus. These data attest to the necessity of further studies dealing with specification of the taxonomy of TBE complex viruses.

[The geographical distribution of genetic variants of the tick-borne encephalitis virus]. / Geograficheskoe rasprostranenie geneticheskikh variantov virusa kleshchevogo éntsefalita.

Geographic distribution of 185 tick-borne encephalitis (TBE) virus strains isolated in 8 physico-geographic areas and classified into six genetic variants was analysed. The strains of genetic variant I homologous to the Sophyin prototype strain were found to occur predominantly in the Far East and also frequently found in Western and North-Western parts of the East European plain. The vast territories from lake Baikal in the East to Ukraine in the West harbor mostly the strains significantly different from the Far-Eastern Sophyin strain. Hybridization experiments with oligonucleotide probes specific for the Neudorffle strain showed that the strains genetically similar to the virus of central European encephalitis occurred also in Eastern Europe and Western Siberia. It is concluded that a relationship exists between genetic types of TBE virus and their geographic origin.

[The characteristics of the relationships of arthropods of the refuge complex with the causative agents of transmissible viral infections in bird rookeries]. / Osobennosti sviazei chlenistonogikh ubezhishchnogo kompleksa s vozbuditeliami transmissivnykh virusnykh infektsii v kolonial'nykh poseleniiakh ptits.

The isolation of viruses of tick-borne encephalitis, West Nile fever, and Omsk hemorrhagic fever from arthropods of nests of colonial birds (rook, sand martin, tree sparrow, Laridae) in different zones of West Siberia (from tundra to steppe) has been analyzed. The role of gamasid mites, hematophages and saprophages, characteristic inhabitants of nests of colonial birds, and of the tick Ixodes lividus in connection with their biology, coadaptation with hosts, microclimatic nest conditions, etc. has been evaluated. It has been concluded that the whole nest community of arthropods in a nest rather than one infected individual has to be regarded as an infective unit in colonies.

[The typing of tick-borne encephalitis virus strains by the soluble antigen]. / Tipirovanie shtammov virusa kleshchevogo éntsefalita po rastvorimomu antigenu.

Sucrose-acetone-treated antigens (SAA) and soluble antigens (SA) prepared from them by treatment with 8 M urea for eight TBE virus strains isolated in different parts of the virus distribution area were studied in cross CFT with immune ascitic fluids (IAF) for these strains as well as for OHF and Powassan viruses. With SAA, the difference in titres with homologous and heterologous IAFs, as a rule, did not exceed twofold, whereas with SA was 32-fold. It was also noted that in the homologous system the titre of SA decreased not more than 4-fold as compared with that of the initial SAA while in the heterologous system it declined from 4- to 16-fold or more. The level of antigenic relationship of strains was expressed by the formula HAg = SA titre/SA titre X 100%. It was shown that at HAg greater than or equal to 25% the strains used for antigen and antibody generation were closely related and at HAg less than or equal to 6.25% belonged to different subtypes. The analysis of the data suggested the existence of a fourth, "Urals-Siberian" antigenic variant of TBE virus. Using the developed criteria, the 20 strains under study (with one exception) were alloted into one of the four antigenic variants or qualified as intermediate.

[Comparison of 3 express-methods of detection of tick-borne encephalitis virus]. / Sravnenie trekh ékspress-metodov indikatsii virusa kleshchevogo éntsefalita.

Comparative studies of the diagnostic value of three express methods for detection of tick-borne encephalitis virus in ticks (fluorescent antibody technique (FAT) enzyme immunoassay (EIA), and molecular hybridization of nucleic acids) and the traditional method (bioassay in white mice) showed all the three express methods to be rapid, specific, sensitive, and useful for large-scale epidemiological surveys. Notable was the high effectiveness of the method of nucleic acids hybridization which was not inferior to bioassays in suckling mice and exceeded FAT and EIA. The results of the latter seem to be affected by antigenic variations among tick-borne encephalitis virus strains.