Protein antigen conjugated with cholesteryl amino-pullulan nanogel shows delayed degradation in dendritic cells and augmented immunogenicity

Carriers that augment delivery, immunogenicity or both are crucial in the development of vaccines especially component vaccines as components of pathogens are often poorly immunogenic. Cholesteryl pullulan (CHP) that forms nano-sized hydrogel (nanogel) and encapsulates proteins was shown to be useful in the delivery of vaccines. Here we demonstrate that subcutaneous immunization of mice with bovine serum albumin (BSA) chemically conjugated to NH2-CHP nanogel induces strong antibody production. This augmented antibody production requires covalent conjugation between BSA and CHP, but does not require nanogel formation. Conjugation of NH2-CHP nanogel induces persistence of BSA in dendritic cells (DCs) in vivo. As resistance to lysosomal degradation was previously shown to augment antigen presentation by DCs, conjugation of antigens with CHP nanogel may enhance antibody production to antigens by delaying lysosomal degradation. Therefore, delayed degradation of antigens by covalent conjugation with nanoparticles may be a good strategy for the development of effective vaccines.