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

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

Delivery is one of the major barriers to DNA vaccine. Administration of naked DNA is usually inefficient with only a small fraction of DNA being taken up by the cells and subsequently expressed [112] . This is because DNA is a negatively charged, hydrophilic macromolecule; it is incapable of crossing the biological membrane unassisted. Therefore, a safe and efficient DNA delivery system is sometimes employed as adjuvant to facilitate efficient cellular uptake of DNA vaccines, promote DNA release inside the cells, induce high level of antigen expression and hence immune responses. Physical method such as gene gun, also known as the particle-mediated epidermal delivery, has been studied to deliver DNA to the skin [101, [113] [114] [115] . Gold beads coated with DNA vaccines are discharged directly into the cytoplasm and nuclei of skin cells. This method of delivery has enjoyed some success, but is not applicable for intranasal administration. Considerable efforts have been made to improve the efficacy by developing effective DNA delivery systems for intranasal vaccines. Formulation of DNA vaccines in synthetic non-viral vectors such as polymeric nano-/micro-particles and liposomes has been reported to increase the uptake of plasmid DNA by cells, increasing immunogenicity in animal models and humans. Additional adjuvants may also be used to further improve the immunogenicity of these delivery systems.