Abstract
The heterologous prime-boost immunization is able to increase the humoral and cellular immune response and elicit a more effective and broad antibody response in the development of influenza vaccine. In this study, we used the DNA vector encoding the full-length HA protein and the VLPs) to develop the DNA prime-VLP boost immunization regiment against highly pathogenic H5N1 viruses. The VLPs comprising HA, NA, M1 and M2 of influenza viruses were obtained by baculovirus coexpression system in insect cells. The immunological and structural analyses suggested that the humoral immune responses were skewed toward reacting against the immunodominant epitopes located in variable regions of the HA. We further constructed the H5N1 DNA vaccines by “masking” or “dampening” the HA variable regions to promote reactions to subdominant epitopes located in more evolutionarily conserved domains. The H5N1 immunorefocusing DNA vaccine could be evaluated by heterologous prime-boost immunization and induced cross-neutralizing antibodies against various clades of highly pathogenic H5N1 viruses. The results may provide useful information for the further development of an effective influenza virus vaccine.