Chitosan-alginate/R8 ternary polyelectrolyte complex as an oral protein-based vaccine candidate induce effective mucosal immune responses.

Vaccination is the most effective method for preventing infectious diseases. Oral vaccinations have attracted much attention due to the ability to boost intestinal and systemic immunity. The focus of this study was to develop a poly (lactide-co-glycolide) acid (PLGA)-based ternary polyelectrolyte complex (PEC) with chitosan, sodium alginate, and transmembrane peptides R8 for the delivery of antigen proteins. In this study, the antigen protein (HBf), consisting of the Mycobacterium avium subspecies paratuberculosis (MAP) antigens HBHA, Ag85B, and Bfra, was combined with R8 to generate self-assembled conjugates. The results showed that PEC presented a cross-linked reticular structure to protect the encapsulated proteins in the simulated gastric fluid. Then, the nanocomposite separated into individual nanoparticles after entering the simulated intestinal fluid. The ternary PEC with R8 promoted the in vivo uptake of antigens by intestinal lymphoid tissue. Moreover, the ternary PEC administered orally to mice promoted the secretion of specific antibodies and intestinal mucosal IgA. In addition, in the mouse models of MAP infection, the ternary PEC enhanced splenic T cell responses, thus reducing bacterial load and liver pathology score. These results suggested that this ternary electrolyte complex could be a promising delivery platform for oral subunit vaccine candidates, not limited to MAP infection.