Pathogens in Ixodes persulcatus and Ixodes ricinus ticks (Acari, Ixodidae) in Karelia (Russia).

Ixodid ticks (Acarina, Ixodidae) are vectors of dangerous human infections. The main tick species that determine the epidemiological situation for tick-borne diseases in northern Europe are Ixodes ricinus and Ixodes persulcatus. In recent years, significant changes in the number and distribution of these species have been observed, accompanied by an expansion of the sympatric range. This work summarizes the data of long-term studies carried out in Karelia since 2007 on the infection of I. persulcatus and I. ricinus ticks with various pathogens, including new viruses with unclear pathogenic potential. As a result, tick-borne encephalitis virus (TBEV, Siberian genotype), Alongshan virus, several representatives of the family Phenuiviridae, Borrelia afzelii, Borrelia garinii, Ehrlichia muris, Candidatus Rickettsia tarasevichiae and Candidatus Lariskella arthropodarum were identified. Data were obtained on the geographical and temporal variability of tick infection rates with these main pathogens. The average infection rates of I. persulcatus with TBEV and Borrelia burgdorferi sensu lato were 4.4% and 23.4% and those of I. ricinus were 1.1% and 11.9%, respectively. We did not find a correlation between the infection rate of ticks with TBEV, B. burgdorferi s.l. and Ehrlichia muris/chaffeensis with the sex of the vector. In general, the peculiarities of the epidemiological situation in Karelia are determined by the wide distribution and high abundance of I. persulcatus ticks and by their relatively high infection rate with TBEV and B. burgdorferi s.l. in most of the territory, including the periphery of the range.

[Change in the antigenic structure of surface glycoprotein E of tick-borne encephalitis virus during its adaptation to ticks and mammals].

Enzyme immunoassay and immunoprecipitation test of viral proteins, by applying a tick-borne encephalitis (TBE) viral protein E monoclonal antibody kit, have shown that TBE adaptation to ticks and mammals may cause a considerable change in the antigenic structure of surface glycoprotein E, by involving different antigenic domains, including a neutralizing epitope that seems to participate at the early stages of interaction of virions with the cell membrane.

[Residual neurovirulence of the chimera of Langat and Denge-4 flaviviruses in intracerebral infection of monkeys].

The residual neurovirulence of the previously obtained chimeric virus Tp21/DEN4, containing the RNA region encoding the pre M and E structural enzymes, strain Tp21, virus Langat, and the remaining part of the genome from the Denge 4 virus, was studied in experiments with monkeys Cercopithecus aethiops involving the intracerebral administration of the virus. The tick-borne encephalitis virus, strain Absettarov, was used as positive control. A comparative analysis of the experimental and published data showed the chimeric virus to be less virulent by its degree of morphological affection in the CNS zones, its spread into the CNS and by a percentage share of animals with viremia versus the Tp21 parent strain and Elantsev strain of the Langat virus.

[Virus-specific proteins of Crimean-Congo hemorrhagic fever]. / Virusspetsificheskie belki virusa Krymskoi-Kongo gemorragicheskoi likhoradki.

A variant of Asian strain Hodzha of Crimean-Congo hemorrhagic fever (Hodzha-A), adapted to Vero-E6 culture and yielding high harvest in it, was used for analysis of the synthesis of virus-specific proteins and protein composition of virions. Major virus-specific proteins with mol. weights 110, 83, 78, 55, 57, and 45 kD and minor low-molecular-weight proteins of 42, 36, 23, and 21 kD were detected by immunoprecipitation with hyperimmune ascitic fluid and polyacrylamide gel electrophoresis in infected cell lysates. N-type glycosylation of gp83 and gp78 was shown using tunicamicin. Viral proteins with mol. weights of 83, 78, 55, 57, and 45 kD were detected in infected cell culture fluid and in purified virion preparations after ultracentrifugation in sucrose density gradient. Two proteins with mol. weights 55-57 and about 180 kD were detected in purified nucleocapside preparations.

[Change in Na+,K+-ATPase activity during reproduction of the tick-borne encephalitis virus in SPEV cell culture]. / Izmenenie aktivnosti Na+,K+-ATPasy pri reproduktsii virusa kleshchevogo éntsefalita v kul'ture kletok SPEV.

Changes in the activity of Na(+),K(+)-ATPase during infection of SPEV cells with tick-borne encephalitis (TBE) virus were studied in preparations of cell membranes and directly in the culture and the effect of this enzyme activity on the penetration of TBE virus in the cells and production of virus-specific proteins investigated. The highest activity of the enzyme was observed directly after challenge and during the 5th and 6th hours of infection, whereas the lowest was recorded during the second and third hours and 24 h postinfection. A similar decrease in the activity of this ATPase was observed in the brain cells of infected mice. Ouabain and low (0 degree C) temperature prevented the virus penetration in the cells, which indicates that this process is energy-dependent. Inhibition of Na(+),K(+)-ATPase led to a drop in the production of virus-specific protein.

[Adaptation of Crimean-Congo hemorrhagic fever virus to culture in Vero-E6 cells]. / Adaptatsiia virusa Krymskoi-Kongolezskoi gemorragicheskoi likhoradki k kul'ture kletok Vero-E6.

Adaptation of the Crimean-Congo hemorrhagic fever (CCHF) virus to continuous culturing in Vero-E6 cells was studied by coculturing of infected and intact cells. Adapted strain Hoja-A exerted a complete cytocidal effect and was characterized by a high level of virus accumulation in the early period of the infection. The resultant strain survived through more than 80 passages and retained the newly acquired properties; lyophilized, it can be stored for a long time. Availability of such a strain opens new vistas in studies of the CCHF agent.