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

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

In recent years, DNA vaccines have attracted considerable attention as an alternative vaccination method against infectious diseases, with the potential to provide broad immune responses similar to the live-attenuated vaccines without the risk associated with the replicating micro-organisms. DNA vaccine approach relies on the in situ production of target antigens. Plasmid DNA encoding antigenic proteins is delivered to the appropriate tissues in the body, leading to the expression of the desired antigens, eliciting specific immunogenic responses and thereby inducing immune protection against the pathogens. Since the host cells are responsible for antigen production, the natural glycosylation and folding of the protein are warranted. Plasmid DNA encoding different bacterial and viral antigens have been tested for their immunogenicity and protective efficacy in vivo, confirming their clinical potential [1] [2] [3] [4] . In addition, DNA vaccines offer several distinct advantages over conventional vaccines. The double helical structure of DNA is simple and stable at high temperature, allowing easy storage and transportation. Large-scale manufacture of DNA vaccines is convenient and relatively cheap. It only requires standard cloning of antigen coding sequence into plasmid vectors, avoiding the complex procedures of repeated culture and inactivation of infectious pathogens, or the purification of recombinant proteins. Apart from their advantageous physicochemical properties, DNA vaccines have the ability to generate the cellular immunity in addition to the humoral immunity. They are also highly flexible, encoding several types of genes including viral and bacterial antigens, as well as immunological proteins. The advantages of DNA vaccines compared to conventional vaccines are summarized in Table 1 .