Molecular genetic characteristics of tick-borne encephalitis virus

Flaviviruses from a tick-borne encephalitis virus (TBEV) complex circulate in about all the countries widely distributed in Northern Eurasia. Complete nucleotide sequences for genomes of different 15 tick-borne encephalitis viruses have been determined in the past years. Phylogenetic analyses of these sequences showed their significant genetic variability. Thus, the genetic differences in the genomes of TBEV strains are as high as 17.3%, but the differences in the amino acid sequences are 9%. These genetic differences permit determination of the time of divergence of the current TBEV genovariants from the common viral precursor in 1700 to 2100. Novel genetic variants of the Far-Eastern TBEV subtype, which are represented by Senzhang and Glubinnoe/2004 viruses, have been discovered in the pastyears. New variants of the same Far-Eastern subtype of TBEV, which are able to induce hemorrhagic tick-borne encephalitis, have been found in Western Siberia. The fact that there are considerable genetic differences in Turkish and Spanish sheep encephalitis viruses has been established within the European subtype of TBEV. The Siberian subtype of TBEV is genetically more uniform; however co-circulation of the Far-Eastern and Siberian subtypes of TBEV has been found in the natural TBEV foci of Siberia. This suggests that there may be at present a change in the genotypes of TBEV in different geographical regions.     

Molecular evolution of West Nile virus

Phylogenetic analysis and estimation of the rate of evolution of West Nile virus (WNV) were conducted. Sixty-eight nucleotide sequences of WNV E protein were used for the analysis. The rate of nucleotide substitution accumulation was 2.5 × 10^?4 substitutions per site per year. Phylogenetic analysis and estimation of WNV evolution time using molecular-clock methodology demonstrated that the WNV genotypes 1, 2, and 4 with an estimated time of divergence from the common precursor of approximately 2360, 2800, and 5950 years, respectively, circulate on the territory of the European part of Russia. The ratio of frequencies of nonsynonymous substitutions (dN) to synonymous substitutions (dS) can vary within 0.022–0.275 for certain WNV strains grouped according to geographical and/or phylogenetic traits. The highest values of dN/dS ratio were found for modern WNV isolates in Russia and in North America, which appeared in new natural biocenoses of these regions in the last 14 years. dN/dS estimation for WNV species shows that indices of intraspecific dN/dS variability can be used for detecting the presence of accelerated evolution of new WNV isolates. All this confirms the hypothesis that favorable conditions exist for wide distribution and rapid evolution of different WNV genotypes (that arose 2000–6000 years ago) in modern natural and climatic conditions.     

Outbreak of acute enterovirus intestinal infection in Sakhalin region in August 2010

The investigation of cases of acute intestinal infections in the Sakhalin region of Russia in August, 2010 is described. Epidemiological and molecular biological studies were conducted. After initial PCR screening and determining the nucleotide sequences of the positive samples the following enteroviruses were found: Coxsackie A2 - 42 samples (45%), Coxsackie A4--31 sample (34%), Enterovirus 71--6 samples (6,5%), Coxsackievirus B5--6 samples (6,5%), Coxsackie B3--4 samples (4%) and Coxsackie B1--4 samples (4%). The phylogenetic analysis of sequences showed that the closest analogues for the nucleotide sequences of these genotypes were previously identified in Japan, Korea and China in 2000-2010.