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

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

Influenza is caused by orthomyxoviruses which are RNA viruses that affect mainly the upper respiratory tract. In recent years, zoonotic or variant influenza has become a serious threat to human health, including the avian influenza virus H5N1 and H9N2, and the swine influenza virus H1N1 and H3N2. Although these animal viruses are distinct from human influenza viruses and do not usually transmit between humans, they may still occasionally infect humans and cause severe pneumonia and even death. Furthermore, if such a virus acquired the capacity to spread easily among people, it could start an epidemic or even a pandemic [92, 93] . To protect the populations from influenza infection, highly effective, broad-spectrum influenza vaccines that could be prepared rapidly are in demand. Current influenza vaccines mainly target the induction of antibodies against the viral glycoproteins, particularly surface glycoproteins hemagglutinin (HA) and neuraminidase (NA). Antibodies to HA neutralize the infectivity of the virus while antibodies to NA prevent the release of the virus from the infected cells. Apart from surface glycoproteins, internal proteins such as nucleoprotein (NP) and matrix protein (M1), as well as the ion channel protein (M2), which are highly conserved between and within different subtypes, have also become very attractive target antigens for vaccines to provide broad, cross-strain protection [94, 95] .