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

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

Tuberculosis (TB) is a bacterial infectious disease caused by Mycobacterium tuberculosis which is transmitted by respiratory aerosols. TB has become a major public health problem that threatens the progress made in TB care and control in the world. The only TB vaccine currently available is an attenuated strain of Mycobacterium bovis, Bacillus Calmette-Guérin (BCG), developed in the 1920s. However, its efficacy against adult pulmonary TB remains controversial [74] . With the emergence of drug-resistant TB and increasing rates of HIV/AIDS and TB co-infection, a new effective TB vaccine is urgently in need. Effective protective immunity to Mycobacterium tuberculosis requires cell-mediated immune responses, including both CD4 + and CD8 + T cells [75] [76] [77] . Since DNA vaccines have the ability to induce strong cellular immunity, it has become an attractive vaccine approach against TB. The first two studies that reported promising protective effect with DNA vaccine against tuberculosis were conducted in mice using plasmid DNA encoding antigen 85A (Ag85A) of Mycobacterium tuberculosis [78] and the 65 kDa heat-shock protein of Mycobacterium leprae (hsp65) [79] . Other different antigens such as Ag85B ESAT-6, IL-23, MPT64, PstS-3 and other fusion proteins have also been explored as DNA vaccines against tuberculosis [80] [81] [82] [83] [84] [85] . Most of these DNA vaccines encode mycobacterial proteins that are either secreted in mycobacterial culture filtrate or exposed on the mycobacterial cell-wall surface.