Vol 49, No 3 (2004)

According to research, the epidemic rise of influenza was preconditioned, during 2002-2003, in Russia by the circulation of influenza A(H1N1), A(H3N2) and В viruses. The Center of Influenza Ecology and Epidemiology undertook a study of 178 epidemic strains: 41 strains A(H1N1), 116 strains A(H3N2) and 21 strains of influenza В were among them. All strains were isolated in the MDCK cell culture. A simultaneous isolation in embryonated eggs as well as changing of the isolation system from MDCK to embryonated eggs were found to be effective only for influenza A(H1N1) viruses. According to the antigenic analysis, all A(H1N1) viruses were variants of the etalon A/New Caledonia/20/99. The A(H3N2) viral strains' population was heterogeneous by its antigenic properties: among its isolates, there were variants similar to the etaions of A/Moscow/10/99 and of A/Panama/200/99 as well as strains, which weakly reacted with sera of both above etaions; possibly the latter were close to the etalon of A/Fujian/411/02. All epidemic strains of influenza В virus belonged, according to the antigenic properties of hemagglutinin, to the virus group of B/Victoria/2/87-like and were antigenic variants of the etalon of B/Hong Kong/22/01. This confirmed that influenza В viruses with the antigenic hemagglutinin structure of the virus group of B/Victoria/ 2/87-like, which were not present in Russia for more than 10 years, reentered the active circulation. An analysis of antigenic properties of neuraminidases (NA) of the mentioned epidemic strains showed their different degrees of relationship with the NA etaions of both evolutionary groups, i.e. B/Victoria/2/87 and B/Yamagata/16/88-like. A study of paired sera obtained from patients showed a growth of antibodies to the etaions of influenza A(H1N1), A(H3N2) and В viruses of the season in question, which confirmed the virology data.

The receptor properties of Н1 and H2 influenza viruses (IV), isolated from duck, pig and man were studied by using the natural and synthetic sialoglycoconjugates. It was shown that viruses, isolated from different hosts, adapt themselves to the host cell receptors. The IV affinity was increasing to 6'sialy(N-acetyllactosamine) in proportion as amino acids (in positions 138,190,194 and 225), which are for avian IV, were increasingly replacing. Some of the porcine viruses display adaptation to the human receptor, i.e. 6'sialy (N-acety llactosamine), however, all tested porcine influenza viruses, belonging to different evolution branches, acquired even more affinity to sulphated and fucozyled derivatives of 3'sialy(N-acetyllactosamine) - (Neu5ACa2-3gALpi-4(fUCa1-3)(6-sulfo)GlcNAcp).

The paper contains a description of modern data on etiotropic therapy (chemotherapy) for widespread and socially-signific ant viral infections, like influenza, acute respiratory lesions, herpes-virus infections, hepatitis, AIDS and other extra dangerous viral infections. The survey focuses on the contribution of Russian researchers to creating antiviral chemopreparations.

Comprehensive virological, serological as well as genetic studies of the ecology of West Nile Virus (WNV) as well as of some other arboviruses were undertaken in different ecosystems in the territories of the Astrakhan Region and of the Kalmyk Republic The mam carriers (mosquitoes, ticks, birds and mammals) were defined as involved in the circulation of viruses within the natural and anthropogenic biocenosis. Phylogenetic examinations of isolated strains and samples, which were positive in RT-PCR, showed an absolute predominance of genotype I virus that was most closely related to American and Israeli strains. At the same time, epidemic strains had up to 6% of nucleotide differences versus the historic strains isolated in the same region 20-30 years ago. Besides, the circulation of genotype IV was discovered; it was characterized by a lower pathogenicity, which, possibly, ensures the shaping of a pronounced immune inteiiayer bearing no epidemic consequences. An analysis of the study results on the WNV ecology denotes the epicenter of the endemic territory located in the middle part of the Volga delta.

Primary genome structures of 3 variants of the NADC-8 North American virulent strain of porcine reproductive and respiratory syndrome virus (PRRSV) were compared for the purpose of detecting any potential genetic virulence determinants of genus Arterivirus. Apart from the virulent variant, we also investigated the attenuated variant, obtained after 251 passages in cell culture, and the intermediate variant isolated from a pig after a partial reversion of the attenuated virus. The attenuated variant genome acquired a 3-nucleotide deletion and 50 mutations versus its virulent precursor. A comparison of the attenuated and intermediary virus variants denoted 8 nucleotide mutations entailing substitutions of 6 amino acids in 3 open reading frames (ORF1a, ORF1b and ORF6). A 32-clone library was constructed in the pACYC177 plasm id vector, which comprised full-size copies of the genome of the NADC-8 attenuated variant strain (251), virus PPCC, for the purpose of experimentally verifying the functional role of the obtained mutations. Full-size analogues (+-chain of RNA) of the viral genome, comprising the CAP-structures and polyadenylated ones were obtained in vitro on the basis of the cloned DNA. Seven of the 8 analyzed clones of the viral genome were infected and their insertion into the MARC-145 cell resulted in obtaining of infectious PRRSVs. Four of the constructed recombinant viruses had delayed growth parameters, and 3 of them were similar to the parental strain. The described technology (inverse genetics) would make it possible to introduce changes into the viral genome in applied and fundamental research of Arteriviruses.