Intranasal DNA Vaccine for Protection against Respiratory Infectious Diseases: The Delivery Perspectives

Xu, Yingying; Yuen, Pak-Wai; Lam, Jenny Ka-Wing

Coronaviruses (CoV) are potentially lethal pathogens, characterized by the presence of spike proteins on the viral surface. Two new strains, severe acute respiratory syndrome CoV (SARS-CoV) and Middle East respiratory syndrome CoV (MERS-CoV), have been identified. Both of them could cause acute respiratory distress syndrome (ARDS) and are associated with high mortality rates [86] . CoV vaccines have historically exhibited poor capacity for cross-protection [87] , the development of safe, broad spectrum and effective vaccines that can be rapidly made available during an emerging epidemic is required. Currently, there are no approved vaccines for human CoV infections, and most of the studies have focused on the SARS-CoV. Spike and nucleocapsid proteins, which are the immunodominant CoV proteins, are the antigens of interest for vaccine development [88, 89] . DNA vaccines that encode nucleocapsid protein induced strong cell-mediated immunity but are not protective after high titer of viral challenge [90, 91] . In addition, nucleocapsid DNA vaccine could induce delayed-type hypersensitivity even in the absence of an antibody response. This effect was not observed with spike protein DNA vaccines.