Dose-Dependent Effect of DNA Vaccine pVAX-H5 Encoding a Modified Hemagglutinin of Influenza A (H5N8) and Its Cross-Reactivity Against A (H5N1) Influenza Viruses of Clade 2.3.4.4b.

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 are known to cause infections in mammals, posing a potential pandemic threat. Due to the ongoing evolution and change in the dominant strains of H5 clade 2.3.4.4b, it is important to investigate the cross-reactivity of vaccines in use and under development against clade 2.3.4.4b viruses. In this study, the immunogenicity of the previously developed DNA vaccine encoding a modified hemagglutinin of the influenza 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 a microneutralization assay against the strains A/chicken/Astrakhan/321-05/2020 (H5N8), A/chicken/Komi/24-4V/2023 (H5N1), and A/chicken/Khabarovsk/24-1V/2022 (H5N1) showed the formation of cross-neutralizing antibodies. Moreover, the study of protective properties showed that the DNA vaccine protected animals from mortality after infection with A/chicken/Khabarovsk/24-1V/2022 (H5N1) virus.