Introduction. Influenza is a socially considerable infection annually causing profound damage to the populational health and economy. Vaccination is the most effective way to manage influenza and its complications. There are various vaccines against influenza, but their common drawback is the narrow specificity, need for annual virus strain renewal, not always good immunogenicity and effectiveness. In this regard, a close attention is paid to developing universal influenza vaccines aimed to induce cross-reactive factors of the immune response to the most conserved parts of viral proteins. Antibodies against neuraminidase (NA) are able to provide heterosubtypic protection, which is important due to potential threat from influenza viruses, with differed hemagglutinin and neuraminidase compared to the currently circulating viruses. The present study is aimed to search for new and analyze previously predicted linear NA B-cell epitopes, conserved among all subtypes of influenza A virus.Results. there were found out eight conserved linear B-cell epitopes were located around the neuraminidase active site, three of which (MNPNQKIITIGS, ILRTQESEC, and DNWKGSNRP) were synthesized de novo, conjugated with bovine serum albumin to be further used for mouse immunization. Serum IgG antibodies were detected by ELISA in immunized mice. Antibodies specifically bind to various influenza A viruses containing NA subtypes N1, N2, N3, and N9. Immunization with NA peptides provided no protection from profound weight loss after infection with lethal H1N1 influenza virus. However, all immunized mice survived during the observation period, while in control group survival rate was as low as 28.6%. Assessing the viral load in the lungs of mice infected with the H1N1 virus did not reveal differences in titers either on day 4 or 8 post-infection. Nevertheless, the protective effect lacked upon challenge with lethal H7N9 influenza virus: mortality, weight loss, and lung virus titers were comparable both in immunized and control mice.Conclusions. The data obtained uncovered cross-reactivity in anti-NA antibodies induced by immunization with NA peptides as well as protective efficacy against infection caused by the H1N1, but not H7N9 virus. Thus, these data are promising and indicate that linear B-cell NA epitopes can be used for design of epitope-directed influenza vaccines, but a deeper and full examination of specificity for conserved NA epitopes as well as optimized immunization schemes are necessary to achieve higher protective efficacy.
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