Polyethyleneimine/fucoidan polyplexes as vaccine carriers for enhanced antigen loading and dendritic cell activation

Vaccination is one of the most effective strategies for preventing infectious diseases. Recently, most research has centered on the development of protein subunit vaccines due to their safety. However, their low immunogenicity remains a challenge. Nanoparticle vaccines offer advantages by protecting proteins from degradation and acting as adjuvants to stimulate the immune system. Herein, a polyplexe (OVA@PEI/Fu) formed by the electrostatic interaction between positively charged polyethyleneimine (PEI) and negatively charged fucoidan was prepared for the encapsulation of a model antigen, ovalbumin (OVA). Experimental results revealed that the incorporation of fucoidan in the polyplexes not only enhanced OVA loading efficiency but also contributed adjuvant effects, significantly boosting dendritic cell activation and maturation in vitro compared to OVA@PEI polyplexes. In vivo experiments showed that the OVA@PEI/Fu can induce strong anti-OVA specific antibody responses, as well as OVA-specific CD4⁺ and CD8⁺ T cell responses. The carrier developed in the present study shows promise as a platform for protein-based subunit vaccines.