DNA vaccine encoding a modified hemagglutinin of influenza A/H5N8 virus protects mice from infection with a lethal dose of influenza A/H5N1 virus

Highly pathogenic avian influenza (HPAI) H5 clade 2.3.4.4b viruses are widespread in wild and domestic birds, causing severe economic damage to the global poultry industry. Moreover, viruses of this clade can adapt to mammals, posing a potential pandemic threat. With the constant evolution and change of dominant strains of H5 clade 2.3.4.4b, it is important to investigate the cross-reactivity of available and developing vaccine preparations. In this study, the immuno-genicity of the previously developed DNA vaccine encoding a modified hemagglutinin of influ-enza A/turkey/Stavropol/320-01/2020 (H5N8) virus, administered by jet injection at doses of 1, 10, 50, 100 and 200 μg, was investigated. The highest titer of specific to recombinant hemagglutinin antibodies was detected in the group of animals injected with 100 µg of DNA vaccine. The cross-reactivity study of sera of animals immunized with 100 µg of DNA vaccine in microneutralization assay against strains A/chicken/Astrakhan/321-05/2020 (H5N8), A/chicken/Komi/24-4V/2023 (H5N1), A/chicken/Khabarovsk/24-1V/2022 (H5N1) and A/chicken/Voronezh/193-1V/2024 (H5N1) showed the formation of cross-neutralizing antibodies. Moreover, the study of protective properties showed that the DNA vaccine prevented morbidity and mortality of animals after infection with both homologous strain A/Astrakhan/3212/2020 (H5N8) and heterologous strain A/chicken/Khabarovsk/24-1V/2022 (H5N1).