Mucoadhesive chitosan-catechol as an efficient vaccine delivery system for intranasal immunization.

The mucosal barrier and scavenging effect of the mucosal layer are two main obstacles in inducing mucosal immunization. To overcome these obstacles, we synthesized a bio-inspired mucoadhesive material, chitosan-catechol (ChiC), for surface modification of inactive porcine epidemic diarrhea virus (PEDV). Studies have revealed that PEDV particles can be facilely and mildly modified by Chi-C forming Chi-C-PEDV nanoparticles (Chic-Ps) through the covalent and electrostatic bond, which effectively prolongs the retention time of PEDV in the nasal mucosa. The cell co-culture model demonstrated that Chic-Ps exhibit enhanced recruitment of dendritic cells via the secretion of stimulating chemokine CCL20 and improving antigen permeability by disruption the distribution of ZO-1 protein in epithelial cells. Additionally, the flow cytometry (FCM) analysis revealed that Chic-Ps facilitate trafficking to lymph nodes and induce stronger cellular and humoral immune responses compared to unmodified PEDV. Notably, Chic-Ps induced a higher level of PEDV neutralizing antibody was induced by Chic-Ps in the nasal washes, as confirmed by a plaque reduction neutralization test. These results demonstrate that Chi-C is a promising nasal delivery system for vaccines. Proof of principle was obtained for inactivated PEDV, but similar delivery mechanisms could be applied in other vaccines when intranasal administration is needed.