[Variants of the immunoreactivity and infectious process in bank vole (Myodes glareolus) experimentally infected with the hantavirus Puumala (PUUV)].

As a result of a longitudinal study of the Puumala hantavirus (PUUV) in the experimentally infected bank voles (Myodes glareolus), we revealed three groups of the voles differing in the immunoreactivity and viral antigen concentration in the organs. The close correlation between these parameters suggested the existence of various mechanisms of the hantavirus persistence in the host.

[The epidemiological, epizootological, and etiological characteristics of the 2006-2007 outbreak of hemorrhagic fever with renal syndrome in the Tambov Region].

The findings suggest that there are natural foci of hantavirus infection in the Tambov Region. There is evidence that Dobrava/Belgrade hantavirus (DOB-Aa) was a leading etiological agent in the outbreak of the disease in the winter of 2006-2007. Epidemiological analysis showed that the outbreak of hemorrhagic fever with renal syndrome (HFRS) afflicted the region during November to April, by reaching its peak in January (52.2%). Among the patients with HFRS, rural dwellers were 91%. People were infected with the virus mainly by taking care of domestic animals (97.2%). The reservoir of the virus and the source of its human infection in the outbreak was a field mouse, its western subspecies Apodemus agrarius agrarius, which was absolutely dominated among all the virus carriers.

[Hantavirus infection in bank voles in the natural reservoir. Part 1. Characteristics of an infection process in bank voles]. / Khantavirusnaia infektsiia u ryzhikh polevok v prirodnom ochage. Soobshchenie 1. Osobennosti infektsionnogo protsessa v organizme polevok.

The specific features of hantavirus infection in naturally infected bank voles (Clethrionomys glareolus), the principal host of hantavirus of the serotype Puumala, were studied during long-term observation of individually marked animals in the active focus of hemorrhagic fever with renal syndrome (HFRS) in the south of Udmurtia. The infection time in the bank voles was defined by paired serum seroconversion tests. In the natural focus, hantavirus was shown to cause asymptomatic persistent infection in the bank voles with the body's peak accumulation of the virus and its environmental discharge within the first month of infection. In this period the animals present the greatest epidemic and epizootic hazards. Hantavirus infection has no negative impact on the viability of bank voles.

[Viral infectious and chromosome aberrations in Bank Vole from natural and laboratory populations]. / Virusnye infektsii i khromosomnye narusheniia u Ryzhei polevki iz prirodnykh i laboratornykh populiatsii.

The frequency of chromosome damage was studied in the carriers of virus of the hemorrhagic fever with renal syndrome (Puumala virus) and in noninfected animals from two laboratory colonies and two natural populations of bank vole. In the laboratory colony, where Puumala virus persisted for three years, multiaberrant ("rogue") cells were found in the bone marrow; the mean frequencies of both structural and numeral chromosome abnormalities were significantly enhanced. In the other laboratory colony, no Puumala virus was detected during all 30 years of its existence, but the mean frequencies of structural chromosome damage were increased to the same degree probably due to the prolonged breeding under laboratory conditions, which resulted in suppression of immunity and DNA repair. The voles from the natural populations were more resistant to the clastogenic viral effect, but they also had multiaberrant cells which served as indicators of viral infection. The data obtained support the hypothesis that viral infections increase mutation rate, contributing thereby to the evolution process.

Dynamics of Puumala hantavirus infection in naturally infected bank voles (Clethrinomys glareolus).

Specific features of hantavirus infection in bank vole (Clethrionomys glareolus) were studied in the endemic area of hemorrhagic fever with renal syndrome (HFRS) in the foothills of the Ural mountains, using long-term observations on living animals by the capture-mark-recapture (CMR) method. The results demonstrated that the infection naturally circulating in the voles is chronic (lasting for up to 15 months) and asymptomatic, with a peak of Puumala virus accumulation and release from the organism during the first month after infection. It was shown that the bank vole population includes young animals with maternal immunity, which remain resistant to the Puumala virus infection for 3-3.5 months. The infection rate in voles depended on the age and sexual maturity of animals. The greatest proportion of seropositive animals was observed among overwintered males. Seroconversion in voles was more frequent during the period of high reproductive activity.

Genetic variation of wild Puumala viruses within the serotype, local rodent populations and individual animal.

Reverse transcriptase polymerase chain reaction cloning and sequencing were used to determine the range of S gene/N protein variability in wild Puumala virus (PUU) strains and to study phylogenetic relationships between two groups of strains which originated from Finland and from European Russia. Analyses of the nucleotide and predicted amino acid sequences showed: (1) all PUU strains shared a common ancient ancestor; and (2) the more recent ancestors were different for the Finnish branch and the Russian branch of PUU strains. A cluster of amino acid substitutions in the N protein of Finnish strains was found; this cluster was located within a highly variable region of the molecule carrying B-cell epitopes (Vapalahti et al., J. Med. Virol., 1995, in press). Different levels of S gene/N protein diversity of PUU were revealed supporting the view of geographical clustering of genetic variants. Puumala virus from individual voles was found to be a complex mixture of closely related variants-quasispecies. The ratio of non-silent to silent nucleotide mutations registered in the S genes/N proteins of PUU quasispecies was 4- to 16-fold higher than that in Puumala virus strains, resulting in a more wide range of quasispecies N protein sequence diversity.

Tula virus: a newly detected hantavirus carried by European common voles.

A novel hantavirus has been discovered in European common voles, Microtus arvalis and Microtus rossiaemeridionalis. According to sequencing data for the genomic RNA S segment and nucleocapsid protein and data obtained by immunoblotting with a panel of monoclonal antibodies, the virus, designated Tula virus, is a distinct novel member of the genus Hantavirus. Phylogenetic analyses of Tula virus indicate that it is most closely related to Prospect Hill, Puumala, and Muerto Canyon viruses. The results support the view that the evolution of hantaviruses follows that of their primary carriers. Comparison of strains circulating within a local rodent population revealed a genetic drift via accumulation of base substitutions and deletions or insertions. The Tula virus population from individual animals is represented by quasispecies, indicating the potential for rapid evolution of the agent.

Sequences of wild Puumala virus genes show a correlation of genetic variation with geographic origin of the strains.

An experimental scheme was developed for direct sequence analysis of Puumala virus-containing specimens from wild rodents (Clethrionomys glareolus). Total RNA isolated from rodent lung tissues was reverse-transcribed in the presence of a universal 11 nucleotide primer complementary to all three viral RNA segments followed by amplification in a PCR with gene-specific primers. A full-length PCR product of approximately 1800 bp from the S segment encoding the viral nucleoprotein and a product of approximately 900 bp from the M segment (encoding the C-terminal two-thirds of the G2 protein and including the 3' non-coding region) of Puumala virus (from C. glareolus trapped in Udmurtia) were prepared and sequenced. No pronounced differences to Vero cell-grown viruses were seen. The Udmurtia/894Cg/91 strain was more closely related to the Bashkiria/CG18-20/84 strain than to the Finnish prototype strain of Puumala virus, Sotkamo/V-2969/81. Thus there is a correlation with the geographic origin of the three strains. The results indicate the occurrence of genetic drift and different selection pressures leading to (i) clustering of mutations, (ii) a lower frequency of nucleotide substitutions in the coding than in the 3' noncoding regions and (iii) a higher frequency of amino acid substitutions in G2 than in the N protein.

IgG avidity assay for estimation of the time after onset of hantavirus infection in colonized and wild bank voles.

An immunoglobulin G avidity assay was used to determine recent and past hantavirus infection in bank voles (Clethrionomys glareolus). Sera of experimentally infected bank voles were studied at different time intervals. The avidity of specific IgG increased over time after infection. This experimental data were used to estimate the time after onset of hantavirus infection in naturally infected bank voles caught in an endemic area. The possibility to discriminate between recently infected animals and animals infected some time ago is important since the proportion of recently infected bank voles represents the intensity of the epizootic which in turn correlates to the risk of humans to contract the disease.

[The disposition of natural foci of hemorrhagic fever with renal syndrome in different landscape areas of Tyumen Province]. / Razmeshchenie prirodnykh ochagov gemorragicheskoi likhoradki s pochechnym sindromom v razlichnykh landshaftnykh zonakh Tiumenskoi oblasti.

Lungs of 3159 animals of the forest complex from 90 areas of 30 administrative districts of Tyumen Province were examined by enzyme immunoassays for antigen of hemorrhagic fever with renal syndrome (HFRS) during 5 years, 1985-1989. The antigen of HERS virus was detected in the lungs of mammals of 8 species: Clethrionomys glareolus and Cl. rutilus, Siberian and Arctic lemmings (first findings in the world), M. oeconomus, field mouse, common and pygmy shrews. Nearly all the findings refer to the subzone of southern taiga and adjacent areas of subtaiga subzone where Cl. glareolus is the main reservoir of infection and Cl. rutilus an additional one. In the tundra zone, Siberian lemming is the main reservoir of infection and Arctic lemming an additional one. No natural foci of HFRS were found in forest steppe and forest tundra zones. In the subzone of the northern and middle taiga, the antigen was found only on 4 occasions: 3 in common shrews and one in Cl. glareolus (near the town of Khanty-Mansisk). An irregular annual infection rate with HFRS virus was observed in Cl. glareolus as well as its decline from spring to autumn. It cannot be ruled out that lemmings are carriers of a distinct HFRS virus serotype.

[Cases of hemorrhagic fever with renal syndrome in Amur Province associated with the rat serotype of the virus]. / Zabolevaniia gemorragicheskoi likhoradki s pochechnym sindromom v Amurskoi obl., sviazannye s krysinym serotipom virusa.

To carry out serodiagnosis and to determine the serotype of the virus causing hemorrhagic fever with the renal syndrome (HFRS), paired sera obtained from 28 HFRS patients, 42 persons with a history of HFRS (1-17 years after convalescence), and 268 serum samples from healthy persons residing at the areas with the natural foci of this infection have been studied by indirect immunofluorescence techniques at the territory of the Amur Province. This study has demonstrated for the first time that, alongside the diseases caused by HFRS virus of serotype Apodemus, HFRS viruses of serotype Rattus and an unidentified serotype serve as the source of infection for the population of the Amur region. The leading role of serotype Rattus in HFRS has been confirmed by the detection of antibodies mainly to this serotype in serum samples taken from convalescents after HFRS and from the healthy population of the areas with the foci of HFRS virus infection.

[Detection of foci of hemorrhagic fever with renal syndrome in the Estonian SSR]. / Obnaruzhenie ochagov gemorragicheskoi likhoradki s pochechnym sindromom v Estonskoi SSR.

Examination by the enzyme-immunoassay of organs of 10 small mammal species trapped in different landscape zones of the Estonian SSR revealed the presence of HFRS virus antigen in organs of bank voles and field mice. Radioimmunoassay studies of serum specimens from donors demonstrated the presence of antibody to HFRS virus in 2.54% of those examined.

Features of circulation of hemorrhagic fever with renal syndrome (HFRS) virus among small mammals in the European U.S.S.R.

The use of indirect fluorescent antibody testing (IFAT) and enzyme linked immunosorbant assay (ELISA) procedures allowed the hemorrhagic fever with renal syndrome (HFRS) virus antigen to be detected not only in the known reservoir host, Clethrionomys glareolus, but also in 7 other species of small mammals in European foci of the U.S.S.R. Marked viscerotropism of HFRS virus and the participation of brown fat in maintaining the infection in rodents were demonstrated. The frequency of detection of circulating antigen and antibody to HFRS virus in rodents is indicative of the high level of activity of the virus in its epizootic foci.

Adaptation to laboratory and wild animals of the haemorrhagic fever with renal syndrome virus present in the foci of European U.S.S.R. Brief report.

Four strains of haemorrhagic fever with renal syndrome virus (HFRSV) from rodents or patients in European U.S.S.R. foci of HFRS were isolated in laboratory bred C. glareolus. The sensitivity of these animals to HFRSV was compared with that of five other laboratory and wild animals.

[Demonstration of the virus of hemorrhagic fever with renal syndrome in the organs of rodents from natural foci of the infection in the USSR and the serodiagnosis of the diseases]. / Indikatsiia virusa gemorragicheskoi likhoradki s pochechnym sindromom v organakh gryzunov iz prirodnykh ochagov infektsii v SSSR i serodiagnostika zabolevanii.

An indirect fluorescent antibody test (IFAT) and an enzyme-immunological test (ELISA) were used for the detection of HFRS virus in organs of rodents from HFRS foci in the USSR. The virus was found in 115 out of 1120 bank voles, 9 out of 92 redbacked voles, and 2 field voles examined. Spontaneous infection-rate of bank voles in population varied from 1.3 to 100% correlating with the epidemiological situation in foci. IFAT and ELISA were successfully used for serodiagnosis of HFRS. Examinations of 335 paired sera from 157 patients by the IFAT demonstrated seroconversion. Retrospective diagnosis and diagnosis of subclinical forms of the disease were also made.