Vol 48, No 2 (2003)

Complete S-segment nucleotide sequences of genomic RNA were determined for two Crimea-Congo hemorrhagic fever (CCHF) virus strains, i.e. LEIV 10145 Uz isolated from ticks in Uzbekistan, 1985, and LEIV 29223 Stv isolated from a patient in Stavropol region, 2000. It was established that the S-segment length is 1672 and 1674 nucleotides. Therefore, the initiating codon (for methionine) is located at positions 56-58; the length of translation frames for the nucleocapsid protein is 482 amino acid residues. Distinctions in the length of S-segment, as compared to other strains, are related only with the 5 ' and 3 ' non-coding regions. A comparison of the nucleotide and amino-acid sequences of S-segments of genome of the mentioned strains with the early published data showed that the CCHF virus strain isolated in Uzbekistan is mostly close to strains isolated in China, and that the strain isolated in Stavropol region forms, jointly with Drozdov strain isolated in the Astrakhan region, a separate branch in the phylogenetic tree.

The antigenic structure of influenza A NP protein was studied by using a panel of 12 monoclonal antibodies (mAbs). A group of strains of influenza-A virus with the known NP amino acid sequence was analyzed by radioimmunoprecipitation with a subsequent analysis of the immune complexes by electrophoresis in polyacrylamide gel. The examined group of strains comprised pairs of closely related variants like A/USSR/90/77 and A/Brazil/1/ 78 as well as A/Puerto Rico/8/34 (Mount Sinai variant) and A Puerto Rico/8/34 Cambridge 1 variant). The results made it possible to identify position 353 as a part of antigenic site. The combined results of radioimmunoprecipitation and immunoblotting suggest that the mentioned site is recognized by mAb IVE8 as a linear epitope and by mAb as a confirmation epitope. Amino acids in positions 196 and/or 290 are involved in the formation of another antigenic site. The N-terminal part of NP, removed in the course of protein processing, is not involved in the differentiation of avian and human strains by mAb 315. None of the mAbs used in our study recognized the N-terminal part of NP as a linear epitope.

The influenza neuraminidase (NA) possesses, both in vivo and in vitro, the anticoagulant and fibrinolytic activity. A computerized comparative analysis of the influenza NA viruses, type A, showed nine regions of amino-acid sequences compatible with the tissue activator of human plasminogen. The mentioned regions are highly conservative for each NA subtype irrespective of a source or a year, when an influenza strain was isolated. The role of NA in pathogenesis of influenza infection is under consideration.

The specific features of the humoral and local immune responses to influenza vaccines were comparatively studied in people of different age groups. A total of 79 elderly people (aged 67-89) and 80 young people (aged 18-27) were immunized according to one of the four schemes: live cold-adapted reassortant trivalent influenza vaccine (LIV), administered intranasally; inactivated split trivalent influenza vaccine (IIV), administered parenterally; a combination of both above vaccines; and placebo. IIV was found, as compared to LIV, to stimulate more effectively the production of circulating antihaemagglutinins as well as of IgG,-, Ig1-, and Ig3-AT in young persons, while LIV has advantages before IIV in stimulating the synthesis of these immunoglobulins in the elderly. LIV has advantages before IIV in stimulating the synthesis of secretory IgA-AT irrespective of an age of the immunized persons. The combined immunization of the elderly by both vaccines increases the quantitative parameters of the humoral and local responses up to the level of intensity observed in young people. The obtained data are indicative of the possibility of correcting the immune response in the high-risk elderly in respect to influenza infection.

Stability infectivity of viral vaccines against Newcastle disease (ND) from strains La-Sota and Bor-74 VGNKI, prepared by using the method of granulation and spray-coating in fluidizated bed, was studied during the storage of vaccines at different temperatures. The infectious activity of the vaccines was found to remain stable for 6 months at 4 and 8 °C and for 2 weeks at (25 ± 1) °C. An analysis of the findings showed that an improved content of the preparation contributed to an essentially increased ND virus thermal stability in the granulated lactose-containing vaccine.

Four morbillivirus strains were isolated from the Baikal seals Phoca sibirica. The antigen difference between these strains was studied using ELISA with different immune sera and monoclonal antibodies. The assay data indicated three different antigen variants of morbillivirus. The four strains were found to circulate over the Baikal seal population during epizootic.