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

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

As discussed in Section 3.2, improving M cells uptake is another strategy to enhance vaccine immunity. Effective mucosal immunity often correlates with the uptake of antigen by mucosal inductive tissues, such as NALT in the upper respiratory tract following intranasal immunization. Since M cells are responsible for antigen sampling on the mucosal surface for eventual antigen presentation to mucosal B and T cells, targeting of vaccines to M cells can be an effective method to achieve strong immune response. Particle size is an important parameter for M cell uptake. A number of studies have been conducted to identify the optimal particle size for cellular uptake of the mucosal system. Some studies suggest that particle size of less than 1 μm is optimal for oral vaccine delivery for Peyer's patch M cell uptake [131] [132] [133] . Another NALT nanoparticle uptake study also suggested that particles with sub-micron size are optimal for mucosal M cells uptake [134] . It is generally accepted that NALT M cells can uptake nanosized particles rapidly with no definite size range being established [135] . Apart from cellular uptake, particle size also affects the kinetics of lymphatic drainage. It appears that nanoparticles less than 200 nm are more readily transported by the draining lymph compared to larger particles [136] .