MUC5AC and infection: Cationic nanocarriers like PEI can prolong nasal residence time of antigens through electrostatic interactions between positively and negatively charged mucin groups.45 Moreover, PEI adjuvant can promote antigen uptake by and promote the maturation of antigen-presenting cells due to its particle properties.32 Thus, intranasal immunization with PEI-adjuvanted vaccines can elicit stronger and faster innate and adaptive immune responses than natural infection.