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INTRODUCTION: Insectivores are newly recognized hantaviral reservoir worldwide. Four distinct shrew-borne hantaviruses (family Hantaviridae) have been identified in two regions located in southern and northern part of the Russian Far East, two genetic variants of Seewis virus (SWSV), Lena River virus (LENV), Kenkeme virus (KKMV) and Yakeshi virus (YKSV). Here, we describe geographic distribution of shrew-borne hantaviruses in southern part of the Russian Far East: Jewish Autonomous region, Khabarovsk Krai, Primorsky Krai and Sakhalin region. MATERIALS AND METHODS: Lung samples from shrews of genus Sorex, captured in the four regions of Far Eastern Russia, were examined for hantavirus RNA using reverse transcription polymerase chain reaction (RT-PCR). Phylogenetic analysis of the partial nucleotide sequences of viral genome was conducted using MEGA X software. RESULTS: New genetic variant of YKSV was identified in new reservoir host, long-clawed shrew (S. ungiuculatus) from Sakhalin Island. Genetic variant of SWSV, ARTV-Sc, has been found to circulate among S. caecutiens on the seacoast of Khabarovsk and Primorsky Krai. KKMV virus and second genetic variant of SWSV, ARTV-St, were found in S. roboratus and S. tundrensis, respectively from Jewish Autonomous region. CONCLUSION: Sorex-borne hantaviruses were found in all studied regions of Far Eastern Russia. Our results demonstrated co-evolution of SWSV, KKMV, and YKSV viruses throughout the geographic distribution of its hosts.

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Survival of viruses in the environment is a very important problem in epidemiology, especially for infections with indirect transmission. This work describes the results of the experimental study of adsorption and survival of the hantavirus on different environmental substrates (natural organic and inorganic sorbents). Bovine serum albumin (BSA) solution (5-10%) was effective in the hantavirus elution and phosphate-buffer saline (PBS) pH- 7,2 was optimal for elution of specific RNA. Potential survival of the infectious hantavirus on environmental substrates was observed within up to 14 days at +4°C.

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AIM: to provide the morphological characteristics of experimental Hantavirus infection under heat stress conditions to identify the possibilities of its modeling in resistant laboratory animals. MATERIAL AND METHODS: Experiments were carried out on outbred albino mice that were divided into 4 groups: 1) intact mice unexposed to heating; 2) those exposed to heating; 3) Hantavirus-infected animals unexposed to preheating; 4) those exposed to preheating. The animals in Groups 2-4 were long exposed to heat stress at a temperature of 30 °C for 3 hours during 3 days. Strain Aa 60343 (PM-79-95) of the Far East genovariant of Hantaan virus (the genus Hantavirus, family Bunyaviridae) from the collection of the G.P. Somov Research Institute of Epidemiology and Microbiology was used to induce infection. The animals in Groups 3 and 4 were intraperitoneally injected with 700 FFU of Hantavirus per mouse. Materials (lung, liver, kidney, and spleen) taken from Groups 2-4 animals were collected for histological examination on days 1, 3, 7 and 14 of observation. RESULTS: The intact albino mice in Group 1 showed no histopathological changes in the organs. After heat exposure, Group 2 animals were found to have an immunomorphological response in the interstitial tissues of the lung, liver and kidney in partial lymphoid hypoplasia of the spleen. There were no signs of inapparent infection in the presence of marked immunomorphological changes in the organs in Group 3 of hantavirus-infected animals unexposed to preheating. In Group 4, those exposed to preheating exhibited dystrophic and destructive changes in the target organs (lungs, kidneys) in the presence of immunodeficiency manifestations of manifestations that were more pronounced in dead animals. CONCLUSION: In an unresponsive model (adult albino mice), Hantavirus infection caused only obvious immunomorphological changes in the organs. Prolonged preheat stress in the hantavirus-infected animals promoted inapparent infection and morphological manifestations of induced secondary immunodeficiency that was responsible for the manifestation of an infectious process in some animals.

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This paper presents data on the detection of hantavirus in the excretory organs of Apodemus mice which are natural carriers of pathogenic hantaviral serotypes in the Primorye Region. Acute infection periods were detected in naturally infected rodents with the highest hantavirus dissemination to the environment in different phases of rodent population cycles. There was a relationship between the rise of morbidity and the seasonal manifestation of hemorrhagic fever with renal syndrome morbidity and activity of hantavirus reproduction in the murine excretory organs.

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A model of peritoneal macrophages was used to study the effect of fucoidans from brown seaweeds on the adsorption of Hantaan virus. Fucoidans were found to have antiviral activity, but to differ in the inhibition of hantavirus adsorption, which was associated with their structural features. The mechanism of their action is assumed to be shown via ligand-receptor interaction with certain cell membrane receptors and via blockage of hantavirus glycoproteins (G1 and G2), resulting in adsorption inhibition and preventing viral penetration into the macrophages.

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The paper presents the results of studying the time course of changes in antibodies of varying avidity in murine rodents. The presence of low-avidity antibodies is shown to reflect the status of acute infection in the rodent population and their active viral shedding. A relationship is shown between the detection of low-avidity antibodies in animals in spring and autumn and the rise of endemic hemorrhagic fever (EHF) morbidity. The findings demonstrate it possible to use data on the determination of antibodies of varying avidity in the population of murine rodents for the assessment of epizootic and epidemic processes.

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Results of epidemiologic, virologic, and serologic studies of enterovirus infections in Khabarovsk region from 1975 to 2006 were analyzed. Patterns of epidemic process of these infections were established: periodic change of dominating type of pathogen in the population; onset of the large epidemic peaks of incidence during emergence of circulation of new for the given area serotypes of enteroviruses; possibility of realization of several routes of virus transmission. Role of water factor in the progress of the epidemic process was revealed. Etiology of the large epidemic rise of aseptic meningitis incidence in Khabarovsk region in 2006 was established--the leading pathogens were ECHO viruses serotypes E6 and E30.

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The biopolymers extracted from sea hydrocoles were screened and a group of sulfated polysaccharides--fucoidans having a pronounced inhibitory effect on the adsorption of Hantaan virus in the cultured Vero E6 cells was identified. The mechanism of action of sulfated polysaccharides was realized through competitive carbohydrate-specific binding to cell membrane receptors and through ligand-receptor interaction and blocking of Hantaan virus glycoproteins (G1 and G2).

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The data about the incidence of hemorrhagic fever with renal syndrome (HFRS) among the servicemen stationed in HFRS endemic territories at Primorye Region are presented. The authors have shown the epidemiological significance of outbreaks, group and sporadic cases of HFRS especially in servicemen aged 18-20. During the outbreaks the maximal HFRS incidence is registered during 2 weeks after the first case. 104 HFRS cases were registered in the servicemen. Among them 77.8 +/- 3.0% were at the age of 18-20; 7.4 +/- 2.9% of these cases were lethal.

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Pulmonary tissues of red-grey voles, Clethrionomys rufocanus from Shkotovo District and Maritime Territory were investigated. rt-PCR was used to detect the hantavirus nt-222 M-segment genome and nt-403 mitochondrial DNA fragment. A new genetic variant of the PUUV virus named as "Shkotovo", that is different from other PUUV strains by 18-23%, was shown to be circulating in red-grey voles. A phylogenetic analysis denoted 2 PUUV subgroups with their rodent-host branching into C. graleolus and C. rufocanus.

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Data on the circulation of a new genetic variant of Seol virus, which was designated as "Vladivostok" (the name of the place where it was isolated)--VDV, were obtained, by using the antigenic and genetic analysis of hantavirus strains isolated from patients with hemorrhagic fever with renal syndrome (HFRS) and from brown rats, and described in the present paper. A complete identity of nucleotide sequences of the M-segment fragment of isolates obtained from HFRS patients and of those obtained from rats was demonstrated, which confirms the key role of brown rat as a source of infection.

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Monocytes/macrophages are one of the first cells subjected to the infectious effect of viruses. The present paper analyses for the first time the ultrastructural changes in macrophages caused by an agent of hemorrhagic fever with renal syndrome (HERS)--hantavirus (HV). After a local fusion with the host cell plasmalemma and its adsorption on the cell surface, the HV penetrates through the macrophage membrane. This process occurred without destruction of cell plasmalemma. HV viral particles were observe within the macrophage cytoplasm mostly on the smooth granular endoplasmic reticulum vesicles. Viroplasts were defined in macrophages after a 2 h incubation, with synthesis of viral nucleoproteins and primary covers being observed on the surface of viroplasts. Viral particles left macrophages in the process of budding on the phagocyte surface. Thereby HV, similar to other enveloped viruses, realizes entrance and egress from the target cell without damaging its plasmalemma. This accounts for the viral ability to reproduce in macrophages for a long time without any cytopathological effect. Consequently, in the absence of obvious destruction changes, mononuclear phagocytes can serve as a long-term storage of viruses, and thus being involved in HV dissemination during HERS.

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The kinetics of reaction between hemagglutinating antigens and immune sera to 10 hantavirus strains (7 isolated in the Primorye territory and 3 in other regions) was studied in the cross kinetic hemagglutination inhibition (KHAI) test. An A parameter is suggested for evaluation of the similarity and differences between the studied strains. This parameter helped detect antigenic differences between Hantaan and Seoul viruses and the inter-type differences between Hantaan-like strains. KHAI is more specific than HAI studies of antigenic relationships between strains of different hantavirus serotypes.

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The prevalence of Seoul virus in the Primorie territory is presented and its significance in the morbidity structure with regard to hemorrhagic fever with the renal syndrome (HLPS) is discussed. Epidemiological and clinical manifestations of HLPS caused by Seoul virus are described. The authors conclude that in the urban foci of HLPS it is associated mainly with Seoul virus, while in the rural foci, with Hantaan virus.

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Hemagglutinins of Hantaan virus strains isolated in Southern Far East of Russia from patients with hemorrhagic fever with the renal syndrome and from rodents, natural vectors of the virus, were studied in the cross kinetic hemagglutination inhibition test with immune sera to the studied strains. The strains differed by the functional activity index. Use of hemagglutinins of functionally active Hantaan strains in serologic studies notably improves the diagnostic efficacy of the hemagglutination test in Hantavirus infection.

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Four strains isolated from patients with hemorrhagic fever with the renal syndrome and from field mice, natural hosts of Hantavirus, were examined in order to choose a functionally active strain fit for the development of inactivated Hantavirus brain vaccine. Virulent strain PM-10508/89 isolated from mouse lungs was chosen. The strain was highly virulent for newborn mice and rats: 100% of infected mice aged up to 24 h and 75% of rats developed an acute lethal infection upon challenge. The incubation period of Hantavirus adapted to mouse brain was decreased from 19 to 7 days. The infective titer of the virus in brain suspension was 0.1 to 6.5 lg LD50/ml. The strain was highly immunogenic and possessed a high hemagglutinating activity.

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The data on the relationship between the epizootic process in the population of mice (the source of Hantavirus infection) and the seasonal manifestations of morbidity in hemorrhagic fever with renal syndrome (HFRS) in the southern region of the Russian Far East are presented. The asynchronous course of the epizootic process in the population of rodents causes irregularity in the spread of HFRS in the region and periodicity in the appearance of foci. Seasonal rises in HFRS morbidity coincide with the activity of the epizootic process in the population of mice: spring-summer rises with an increase in the number of infected rodents in the populations of large Japanese field mice and autumn-winter rises in voles.

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