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

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

Intranasal vaccination has been investigated for over a decade. The majority of currently available vaccines are administered by intramuscular, subcutaneous or intradermal injection. Although these parenteral routes of administration are effective in inducing systemic immune responses, they are ineffective in inducing local immunity at mucosal sites. As many as 70% of pathogens infect human through the mucosal surfaces [55] . Mucosal vaccination could provide better protection than injectable vaccines against infectious diseases by inducing both systemic and mucosal immunity [56, 57] . Since the strongest immune response is usually induced at the vaccination site and the adjacent mucosal sites, intranasal immunization is able to elicit protective immune response effectively in the lungs and the upper respiratory tract [58] . Nasal mucosa appears to be an appropriate site of vaccine administration against respiratory infectious diseases, not only because the nasal cavity is the first site of contact with inhaled macromolecules and a common site of infection by respiratory pathogens, it can also stimulate respiratory mucosal immunity by interacting with the NALT. Current, licensed intranasal vaccines include FluMist ® , a live-attenuated vaccine that targets influenza types A and B [59] ; and NASOVAC ® , a live-attenuated vaccine that targets H1N1 influenza virus [60] . Apart from live-attenuated vaccine, intranasal route of administration is also favorable to protein-based vaccination, as evidenced by many studies including the intranasal pneumococcal protein immunization against pneumonia [61] , and a recent study on the intranasal respiratory syncytial virus (RSV) vaccine based on a recombinant fusion protein [62] . With the success of intranasal live-attenuated virus vaccine and the promising effect of protein-based vaccine, it is highly plausible that DNA vaccines can adopt the same delivery route to achieve efficient immunization.