H4 influenza viruses have been isolated from birds across the world. In recent years, an H4 influenza virus
infection has been confirmed in pigs. Pigs play an important role in the transmission of influenza viruses to human hosts. Therefore, it is important to develop a new
vaccine in the case of an H4 influenza virus
infection in humans, considering that this virus has a different antigenicity from seasonal
human influenza viruses. In this study, after selecting
vaccine candidate strains based on their antigenic relation to one of the pig isolates, A/swine/Missouri/A01727926/2015 (H4N6) (MO/15), an inactivated whole-particle
vaccine was prepared from A/swan/Hokkaido/481102/2017 (H4N6). This
vaccine showed high immunogenicity in mice, and the antibody induced by the
vaccine showed high cross-reactivity to the MO/15 virus. This
vaccine induced sufficient
neutralizing antibodies and mitigated the effects of an MO/15
infection in a mouse model. This study is the first to suggest that an inactivated whole-particle
vaccine prepared from an influenza virus isolated from wild birds is an effective countermeasure in case of a future
influenza pandemic caused by the H4 influenza virus.