Abstract
Both H5N1 and H7N9 subtype avian influenza viruses cause enormous economic losses and pose considerable threats to public health. Bivalent vaccines against both two subtypes are more effective in control of H5N1 and H7N9 viruses in poultry and novel egg-independent vaccines are needed. Herein, H5 and H7 virus like particle (VLP) were generated in a baculovirus expression system and a bivalent H5+H7 VLP vaccine candidate was prepared by combining these two antigens. Single immunization of the bivalent VLP or commercial inactivated vaccines elicited effective antibody immune responses, including hemagglutination inhibition, virus neutralizing and HA-specific IgG antibodies. All vaccinated birds survived lethal challenge with highly pathogenic H5N1 and H7N9 viruses. Furthermore, the bivalent VLP significantly reduced viral shedding and virus replication in chickens, which was comparable to that observed for the commercial inactivated vaccine. However, the bivalent VLP was better than the commercial vaccine in terms of alleviating pulmonary lesions caused by H7N9 virus infection in chickens. Therefore, our study suggests that the bivalent H5+H7 VLP vaccine candidate can serve as a critical alternative for the traditional egg-based inactivated vaccines against H5N1 and H7N9 avian influenza virus infection in poultry.
Highlights
H5N1 avian influenza virus (AIV) has been widely circulating in China and spread to more than 60 countries, and has caused huge economic losses to the poultry industry worldwide [1, 2]
These results showed that the H5+H7 trivalent (H5) and H7 virus like particle (VLP) were successfully assembled through baculovirus co-infection, which had similar morphology and size with the natural influenza virus particles
These findings suggest that: [1] the bivalent VLP could induce effective antibody response against H5 and H7 in chickens; and [2] Hemagglutination inhibition (HI) and Virus neutralizing (VN) titers elicited by the VLP vaccine were significantly lower than that induced by the commercial vaccine before the virus challenge
Summary
H5N1 avian influenza virus (AIV) has been widely circulating in China and spread to more than 60 countries, and has caused huge economic losses to the poultry industry worldwide [1, 2]. In addition to the serious threat to the poultry industry, H5N1 subtype AIV raises pandemic concerns. As of September 9, 2021, H5N1 AIV has infected 863 people and caused 456 deaths AIV, H7N9 AIV has a significant impact on poultry and human health. Later in 2017, highly pathogenic (HP) H7N9 AIV emerged, and caused severe human infection and disease outbreaks in poultry [4,5,6]. As of June 3, 2021, H7N9 AIV has infected 1,568 people and caused 616 deaths (http://www.fao.org/ag/againfo/programmes/en/empres/ H7N9/situation_update.html). Considering the dual threat to poultry and public health posed by H5N1 and H7N9 AIVs, a bivalent influenza vaccine is needed to prevent a potential pandemic caused by these two subtypes
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