Redox-Responsive Biodegradable Polycation Poly(amido amine) Used As Intranasal Vaccine Delivery Systems

Polycations such as polyethylenimine and chitosan have been widely used as mucosal vaccine delivery systems due to their permeation enhancement effect. Preferably, environmentally responding biodegradable polycations would be better carrier materials for mucosal vaccine delivery. Disulfide bond-based redox-sensitive polycations could respond to the higher intracellular glutathione concentration and degrade in the cytoplasm via the breakage of the disulfide bonds, which are particularly suitable for antigen delivery. In this work, we evaluated the potential of redox-sensitive, biodegradable polycation poly(amido amine) (PAA) as mucosal vaccine carriers. From the primary studies with ovalbumin used as a model protein antigen, it is found that PAA could complex with and encapsulate protein antigen via electrostatic attraction, enhance the cellular uptake of antigen by dendritic cell line DC2.4, prolong antigen residence in nasal cavity, and promote antigen permeation into nasal submucosal layer. Further, Balb/c mice were intranasally immunized with PAA-delivered recombinant hemagglutinin (HA) antigen protein of H7N9 influenza virus. The PAA/HA formulations induced significantly more potent systemic IgG response and mucosal IgA response, higher splenocyte proliferation activity, higher secretion levels of cytokines IFN-γ and IL-4 by splenocytes, more memory CD4⁺ and CD8⁺ T cells, and more DCs expressing MHC II molecule. From the results, the redox-responsive polycation PAA as vaccine carriers helped elicit more potent cellular and humoral immune responses. Particularly, PAA induced much higher cellular immune response compared with previously reported carrier materials. The intelligent PAA could be developed as efficient mucosal vaccine delivery systems for clinical applications.