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Twenty-six patients with hemorrhagic fever with renal syndrome (HFRS) were revealed as a result of serological examination of 582 patients with fever living around Sochi town. Etiologic role of Dobrava virus subtype as the cause of HFRS was assessed by immunofluorescent and ELISA assays, and neutralization test. The principal host of this virus and source of infection for humans is Caucasian forest mouse Apodemus ponticus. HFRS morbidity was sporadic and not dependent from patients' occupation and season. Comparative analysis of clinical and laboratory data from HFRS cases caused by DOB/Sochi and DOB/Lipetsk subspecies, as well as Puumala virus showed higher proportion of severe forms of disease in patients with HFRS from Sochi.

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A total of 5149 small mammals belonging to 16 species were collected from the Lipetsk, Voronezh, and Belgorod regions (40 administrative districts) in 2003-2004 and examined by ELISA and IFA to detect hantavirus antigen and antibodies in the lung tissues. Hantavirus circulation was revealed in 13 species, the highest hantavirus activity being detected in field (Apodemus agrarius) and small wood (A. (S) uralensis) mice (Dobrava-Belgrad virus), bank (Clethrionomis glareolus) (Puumala virus) and common (Microtus arvalis) (Tula virus) voles. These species were frequently found to have their untypical hantaviruses, which was most commonly observed in small wood mice. It is suggested that the small wood mouse is likely to take a certain part in maintaining the circulation of Dobrava-Belgrad virus.

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A natural focus of hantavirus infection was detected and examined during the studies conducted in 2000-2002 around the Sochi (the western spurs of the Great Caucasus Ridge, which descended to the Black Sea (the Krasnodar Territory of Russia). At least 4 rodent species, such as Microtus majori, A. (S.) ponticus, A. agrarius, A. (S.) ciscaucasicus, were shown to participate in the circulation of hantaviruses. A comparative analysis of the nucleotide sequences of genomic S- and M-segments of hantaviruses has provided evidence that 13 viral RNA isolates from the A. (S.) ciscaucasicus belong to the Dobrava/Belgrade virus clade; however the RNA isolate from the Microtus majori belong to the Tula virus clade.

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55697 Ixodidae ticks of 35 species, belonging to 7 genera, were collected in Guinea in 1981-1983. Virological study of 29410 ticks was performed by intracerebral infection of newborn white mice. 49 viral strains were isolated. Authors identified 38 strains of the 8 following arboviruses: Dugbe, Bhanja, CGL-Congo (ecologically connected with ticks), blue tongue virus of sheep and Abadine (association with ticks was found for the first time), Kindia and Forekarya (the new viruses). Serological screening of cattle (by means of agar diffuse precipitation reaction) has demonstrated a wide distribution of isolated viruses in Guinea. Most active circulation was that of Abadine virus. Its peak was observed in the humid season, the period of Amblyomma variegatum imago domination on cattle, this tick being the main source and vector of the virus, as experimentally confirmed.

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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.

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For the first time in the study of epizootology of hemorrhagic fever with the renal syndrome (HFRS) in wild animals data are presented indicating certain relationship between true infection rate of bank voles with HFRS virus and the content of the circulating antigen of HFRS virus and antibody to this virus in these animals. Different age groups of animal populations were shown to have different intensity of immunity: it was more marked in animals of older age groups, and less in young animals. On the contrary, live virus was most frequently found in young animals. It has been shown that for successful isolation of the virus from bank voles it is necessary to take into consideration the characteristics of acute infection in rodents: the presence of HFRS virus antigen in their lung tissue and the lack of antibody to the virus in the blood.

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Four strains of hemorrhagic fever with renal syndrome (HFRS) virus were isolated from the lungs of Cl. glareolus caught in natural foci of HFRS in the European USSR. Preliminary experiments using enzyme-immunoassay (EIA) established the appurtenance of HFRS antigen in lung suspensions to the "western" serotype. Four strains were isolated in Vero-E6 cell culture after several blind passages and identified as the "western" serotype of HFRS virus. One stram originally isolated in Wistar rats and passaged in them 4 times and then adapted to Vero-E6 cells showed a closer antigenic relationship with the "eastern" HFRS virus serotype.

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The necessary conditions of solid-phase radioimmunoassay (SPRIA) have been developed for the detection of arenavirus antigens (Junin, Machupo, Tacaribe, Amapari, and LCM). The sensitivity of SPRIA is higher than that of the complement fixation test more than 100-fold. The antigens could be detected by this method in various materials.

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The possibility of using ELISA for the detection of arenavirus antigens in different organs of infected newborn white mice as well as in the culture fluids of arenavirus-infected cell cultures was demonstrated. The sensitivity of ELISA in antigen detection 100-200 times exceeds that of the CFT, and the time of antigen detection after inoculation of animals or cell cultures is much shorter. The use of ELISA block for the detection and titration of virus-specific antibody also demonstrated high sensitivity of this method as compared with the CFT.

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Conditions for ELISA by using IgG linked with horseradish peroxidase have been developed for the detection of 6 arenaviruses (Machupo, Junin, Tacaribe, Amapari, LCM and Tamiami). This method allows the detection of arenavirus antigens in various materials; organs and blood in affected animals and infected cell culture fluids. It shows higher sensitivity and allows an earlier detection of virus-specific antigens as compared with the CF test.

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IgG to Tamiami virus is covalently bound to metaaminobenzylcellulose by nitrogen coupling. An immune sorbent was prepared and used to treat the virus soluble antigen (SA); a protein responsible for the serological properties of SA was isolated. Electrophoretic analysis in polyacrylamide gel showed this protein to be a nucleocapsid protein of the virion.

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Soluble antigens of 6 arenaviruses (Tacaribe, Tamiami, LCM, Amapari, Machupo, and Junin) were isolated by gel chromatography in servachromium A-2. It was shown that practically the entire antigenic activity of the original virus-containing preparations in complement-fixation (CFT) and agar gel diffuse precipitation (AGDP) tests was due to the presence of soluble antigens in them. Antigenic relationships of the isolated soluble antigens were studied. Physicochemical characteristics of the soluble antigens were determined: buoyant density in cesium chloride solution, sedimentation properties, and sensitivity to RNase. The experimental results suggest that the soluble antigens are fragments of virion nucleocapsids.

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Virological and serological studies of an epidemic disease in Bulgaria, 1975, were carried out. Epidemiologically, clinically and pathomorphologically, the disease simulated almost all known forms of poliomyelitis, acute stem encephalitis, encephalomyocarditis and aseptic meningitis. The studies completely rules out the participation of polioviruses and provided comprehensive evidence for the etiological role of a peculiar enterovirus subsequently identified as enterovirus (EV) type 71 known in the literature since 1974. Altogether, in 1975 and 1976 from 65 cases of poliomyelitis-like disease (PLD) 92 strains of EV71 were isolated, including 37 strains from the brain and medulla, 1 from the cerebrospinal fluid, 10 from mesenterial lymph nodes and tonsils and 44 from faeces. In addition, in 282 convalescent cases of the disease, diagnostic seroconversion or high titers of antibody to this virus were demonstrated. The most successful virus isolation was achieved by inoculation of green monkey kidney cell cultures and newborn white mice. Bulgarian strains of enterovirus 71 regularly caused paralysis in monkeys and morphological poliomyelitis-like lesions in their CNS, and paralysis and myositis with Zenker necrosis in newborn white mice, cotton rats, Syrian hamsters, and 3-week-old cotton rats. The diseased rodents had much more virus in their mucles than in brains.

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In the present report some general physicochemical properties and RNA characteristics of strain 258 of enterovirus (EV) 71, isolated in 1975 from cases of poliomyelitis-like disease in Bulgaria (1), are described. It is concluded, that the features of the virus are consistent with the previous identification, based on biological studies, of this virus strain as a member of enterovirus subgroup of picornaviridae family.

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