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

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

DCs express a large number of surface receptors such as C-type lectin receptors (CLRs) and TLRs, which are engaged in the recognition of pathogens. It has been reported that targeting antigens to receptors on DCs can significantly enhance immune responses [119] . These receptors could be exploited for DNA vaccine targeting with the aid of antibodies or natural ligands. In particular, CLRs are endocytic receptors which recognize carbohydrate structures that resemble pathogen cell-wall components. They are responsible for internalizing pathogens. One of the most commonly studied receptors for vaccine targeting is the DC C-type lectin receptor 205 (DEC-205) which is specifically expressed on DCs. However, ligands for DEC-205 have yet to be identified. Several studies have demonstrated the employment of anti-DEC-205 antibodies to achieve DC targeting for DNA vaccines, including intranasal immunization [120] [121] [122] . Another identified DC-specific target is C-type lectin domain family 9 member A (CLEC9A). Activation of CLEC9A leads to the stimulation of antibody production [123] . Alternatively, DCs could be targeted by using the natural ligands to the mannose receptors [124] . However, the effectiveness of these targeting components in mucosal vaccines remains to be investigated.