Recombinant influenza H9N2 virus with a substitution of H3 hemagglutinin transmembrane domain showed enhanced immunogenicity in mice and chicken.

In recent years, avian influenza virus H9N2 undergoing antigenic drift represents a threat to poultry farming as well as public health. Current vaccines are restricted to inactivated vaccine strains and their related variants. In this study, a recombinant H9N2 (H9N2-TM) strain with a replaced H3 hemagglutinin (HA) transmembrane (TM) domain was generated. Virus assembly and viral protein composition were not affected by the transmembrane domain replacement. Further, the recombinant TM-replaced H9N2-TM virus could provide better inter-clade protection in both mice and chickens against H9N2, suggesting that the H3-TM-replacement could be considered as a strategy to develop efficient subtype-specific H9N2 influenza vaccines.