Molecular-genetic and ultrastructural characteristics of 'Candidatus Ehrlichia khabarensis', a new member of the Ehrlichia genus.

Recently, a new Ehrlichia genetic variant, Ehrlichia sp. Khabarovsk, was identified in tissue samples of small mammals captured in the Russian Far East. To further characterize Ehrlichia sp. Khabarovsk, tissue homogenate from a naturally infected gray red-backed vole (Myodes rufocanus) was passaged three times in newborn laboratory mice. Using nested PCR Ehrlichia sp. Khabarovsk DNA was detected in tissue samples from infected mice at 1-4 weeks post inoculation. Electron microscopic examination revealed morulae containing gram-negative bacterial cells in monocytes of mouse spleen and liver. The size and ultrastructure of these cells corresponded to those described previously and allowed us to identify the bacteria as Ehrlichia sp. The comparison of ehrlichial 16S rRNA, groEL and gltA genes and putative GroEL and GltA amino acid sequences has demonstrated that Ehrlichia sp. Khabarovsk, like Ehrlichia ruminantium, is more distant from all other Ehrlichia species than these species are between themselves. Phylogenetic analysis has shown that Ehrlichia sp. Khabarovsk belongs to the clade formed by Ehrlichia spp. but clusters separately from other Ehrlichia species and genetic variants. These data indicate that Ehrlichia sp. Khabarovsk can be considered as a new candidate species. We propose to designate it as 'Candidatus Ehrlichia khabarensis' according to the territory where this species was found.

[Trends in the spread of pandemic influenza A(H1N1) swl in the Far East in 2009].

The paper describes the trend in the spread of pandemic influenza A(H1N1) swl virus in the Far East, which started in this region 2-3 months later than that in the European part of Russia. By mid-October seasonal epidemic influenza was practically displaced by pandemic one.

[Microorganism "Montezuma" of the order Rickettsiales: the potential causative agent of tick-borne disease in the Far East of Russia]. / Mikroorganizm "Montezuma" iz poriadka Rickettsiales: potentsial'nyi vozbuditel' kleshchevogo transmissivnogo zabolevaniia na Dal'nem Vostoke Rossii.

A new microorganism, tentatively named "Montezuma" was detected in ticks and in specimens (blood, bioptic specimens of the primary affect) taken from patients with an acute fever disease, etiologically linked with the bites of Ixodes ticks in the Far East of the Russian Federation. After sequencing the products of the amplification of DNA isolated from ticks with wide-spectrum primers new primers were developed, highly specific to the unusual sequence thus obtained. The study revealed that ticks of the species Ixodes persulcatus (97%) and Haemophysalis concinnae (5%) contained DNA of this microorganism. The same DNA was detected in materials taken from the patients. The phylogenetic analysis of the gene showed that this organism formed an independent and well defined branch within the order Rickettsiales. The nearest homology (89%) was observed with recently detected endosymbiotes Acanthamoeba. The similarity with their relatives from the families Rickettsiaceae and Anaplasmataceae of the order Rickettsiales was within 81-86%, which made it possible to infer the existence of, probably, only a new genus, but also a family. The isolated DNA belonged, supposedly, to the new microoganism which caused a tick-borne disease in humans, transmitted through bites of Ixodes ticks, and was, supposedly, widely spread in the southern area of the Khabarovsk Territory.

[The first case of granulocytic ehrlichiosis in the Far East of the Russian Federation]. / Pervyi sluchai granulotsitarnogo érlikhioza na dal'nem Vostoke Rossiiskoi Federatsii.

A serological survey of a patient admitted to the Clinic of Infectious Diseases, Far-East State Medical University, for suspected North Asian tick-borne rickettsiosis (NATBR) revealed antibodies in the increasing titers to Ehrlichia phagocytophila and no antibodies to other causative agents of natural and focal infections in the Far East. The disease presented with significant intoxication and maculopapular eruption. This disease differed from the standard NATBR in that there was neither primary affect at the site of pathogen entry, regional lymphadenitis, nor involvement of the liver in the pathological process (elevated levels of AIAT, AsAT, pigment metabolic disturbance), and that there was a steady-state tendency to leukopenia.

[Adaptive property of hantaviruses during their isolation from cultured VERO-E6 cells in relation to the type of the ecological host]. / Adaptatsionnaia sposobnost' khantavirusov pri izoliatsii na kul'ture kletok VERO-E6 v zavisimosti ot vida ékologicheskogo khoziaina.

As a result of virological studies, 185 lung tissue specimens from 4 rodent species caught near Khabarovsk were isolated and fixed in the passages of cultured Vero-6 cells of 68 hantavirus strains. The capacity of the strains to adapt to the cells was assessed by using the adaptive index involving the mean rates of successful isolation, its duration, hantavirus antigen titer in the material used for infection. The strains of hantavirus serotypes were noted for the highest adaptive properties, which are ecologically associated with rodents of the family Mus, such as field and East-Asiatic mice. Lower adaptive capacities were established for the strains of hantavirus serotypes, which are ecologically related to rodents of the family Cricetidae, such as large and large-toothed redback voles. The differences found in the adaptive capacities of hantavirus strains cultured in Vero-E6 cells reflect the degree of specialization of some hantavirus serotypes to particular host rodent species during their long-term coevolution.

[Perfection of methodical approaches to designing vaccines against tick-borne encephalitis]. / Sovershenstvovanie metodicheskikh podkhodov k konstruirovaniiu vaktsiny protiv kleshchevogo éntsefalita.

The protective properties of experimental vaccine against tick-borne encephalitis (TBE) were studied. The vaccine was prepared by conjugating colloid gold with soluble TBE antigen. The protective properties of experimental and commercial vaccines were compared by the mean survival time and protection coefficients after one and three vaccinations of mice infected in doses of 100,000 and 10,000 LD50. In animals immunized with experimental vaccine the protection coefficient and mean survival time were, respectively, 1.3-1.5 times and 10-30% higher than in mice immunized with commercial vaccine. Assessment of the therapeutic activity of antibodies induced by the experimental and commercial vaccines after 1 and 3 immunizations showed the mean survival time to be 1.2-1.7 times longer in animals injected antibodies from mice immunized with the experimental vaccine.

[Area and natural reservoirs of hemorrhagic fever virus with kidney syndrome in the Far East of the USSR]. / Areal i prirodnye rezervuary virusa gemorragicheskoi likhoradki s pochechnym sindromom na dal'nem vostoke SSSR.

Lungs of 9127 small mammals of 17 species trapped in Khabarovsk region, Magadan, Amur, and Sakhalin regions in 1982-1987 were examined, among them 11 species are reservoirs of HFRS virus. Most frequently infected are striped field mice and Japanese field mice, red voles and large-toothed red-backed voles which are the dominant species of the appropriate landscape formations. Circulation of two HFRS virus serotypes among small mammals was demonstrated. The main epidemiological role belongs to the striped field mouse in HFRS foci of the meadow-field type, and to Asiatic field mouse in forest foci in the territories examined.

[Characteristics of the epidemic process in enterovirus infections in relation to the study of a serous meningitis outbreak]. / O nekotorykh zakonomernostiakh épidemicheskogo protsessa énterovirusnykh infektsii v sviazi s izucheniem vspyshki seroznogo meningita.

The etiological investigation of an epidemic outbreak of aseptic meningitis occuring in 1978 in Khabarovsk was performed. The leading etiological agent was found to be ECHO-4 virus. Some of the cases were associated with ECHO-20 and Coxsackie B1 viruses. Investigation of the herd immunity to these viruses in the urban population showed that before the outbreak the immune portion to ECHO-4 and ECHO-20 viruses was low, particularly in children and youngsters. This might be due to the fact that active circulation of these viruses and outbreaks of diseases associated with them had occurred 13--15 years before. The immune portion to enteroviruses in different towns of the Far East was shown to be uneven. The results of investigations of the epidemic outbreak and herd immunity permit to consider it to be a typical manifestation of the cyclic circulation of enteroviruses in the territory and in time.