[Genetic diversity of the tick-borne encephalitis virus in Ixodes persulcatus ticks in northeastern European Russia].

The genetic diversity of the tick-borne encephalitis virus (TBEV) in the PCR-positive Taiga ticks collected in the Republic of Komi in 2010 was evaluated. The analyses of nucleotide sequences of the 5'-NCR fragments of viral genome from ticks had shown that 13 isolates of TBEV from 16 sequencing variants were represented by the highly pathogenic Far Eastern genotype of the TBEV and only 3 isolates were identified as the Siberian genotype of TBEV. The nucleotide sequences of 5'-NCR of viral genome strongly varied variable in individual ticks. Variability for the A1 element has been observed in all the tested samples, and for elements C1, B2, CS B--in more than 50%. A2 element and ATG codon of the 5'-NCR remained completely conservative. Computer simulation of conformations of the 5'-NCR of TBEV genome demonstrated the possibility of significant changes of the spatial structure of the 5'-NCR of viral genome in individual taiga ticks. The obtained data confirm the hypothesis that the variability in the 5'-NCR of TBEV genome can be crucial for efficient replication of TBEV in different hosts.

[Influence of mutation L,D-carboxypeptidase-coding gene on dynamics of Listeria infection].

AIM: To study the progress of infection caused by mutant Listeria monocytogenes with deletion of Imo0028 gene coding L,D-carboxypeptidase (protein involved in metabolism of peptidoglycan). MATERIALS AND METHODS: Deletion of Imo0028 gene was performed with site-specific mutagenesis method using wild-type strain EGDe. Virulence was studied on mice of BALB/c line. RESULTS: Strain GIMd0028 with deletion of Imo0028 gene did not differ from parent strain on in vitro growth rate, cytotoxicity and production of listeriolysin O and phospholipase PlcA pathogenicity factors. Effective LD50 for wild-type strain EGDe was 1x10(4) CFU/ mouse and 2x10(5) CFU/mouse for intravenous and intraperitoneal inoculation respectively. Deaths of animals were observed after 3 - 7 days. LD50 for mutant strain GIMd0028 was 1x10(5) CFU/mouse for intravenous inoculation. It was not possible to determine LD50 for intraperitoneal inoculation, and infection progressed atypically slowly. For example, deaths of animals were observed during 22 days (time of experiment) starting from day 4 when strain GIMd0028 in dose 10(6) CFU/mouse was used for inoculation. In average, death of 1 - 2 mice out of 75 inoculated was observed. Presence of L. monocytogenes was confirmed by its isolation from liver and brain of dead mice. CONCLUSION: Disruption of function of Imo0028 gene coding L,D-carboxypeptidase protein, which takes part in metabolism of peptidoglycan, changes dynamics of listeriosis.

[Differentiantion of Listeria monocytogenes strains isolated in the Far East and European part of Russia on the basis of polymorphism of genes encoding invasion factors].

Forty Listeria monocytogenes isolates obtained in European and Far East regions of Russia were differentiated on the basis of polymorphism of 5 markergenes. Total length of concatemers obtained after sequencing of internal fragments of genes inlA, inlB, inlC, inlE and prs was 3029 b.p. Comparative analysis of concatemers' sequences revealed 237 variable nucleotides. Totally, 25 sequence types were revealed, and isolates from European and Far East regions belonged to different types. On the dendrogram isolates split on 2 clusters, which correspond to early described phylogenetic lines of L. monocytogenes specie. Isolates obtained in European and Far East regions formed independent subclusters within main clusters. Fifteen clinical isolates of L. monocytogenes belonged to 7 different types. Analysis of epidemiologic data on time and place of isolates obtaining suggested that isolates of the same sequence type are epidemiologically related and might represent one strain; index of discrimination for proposed typing method was calculated as 0.982.