Tailoring nanostructured lipid carriers for the delivery of protein antigens: Physicochemical properties versus immunogenicity studies

New vaccine formulations are still highly anticipated in the near-future to face incoming health challenges, such as emergence or reemergence of severe infectious diseases, immunosenescence associated with elderly or the spread of pathogens resistant to antibiotics. In particular, new nanoparticle-based adjuvants are promising for sub-unit vaccines in order to elicit potent and long lasting immune responses with a better control on their safety. In this context, an innovative delivery system of protein antigens has been designed based on the chemical grafting of the antigen onto the shell of Nanostructured Lipid Carriers (NLC). By using the well-known ovalbumin (OVA) as model of protein antigen, we have compared the immunogenicity properties in mice of different formulations of NLC grafted with OVA, by studying the influence of two main parameters: the size (80 nm versus 120 nm) and the surface charge (anionic versus cationic). We have shown that all mice immunized with OVA delivered through NLC produced much higher antibody titers for all tested formulations as compared to that immunized with OVA or OVA formulated in Complete Freund Adjuvant (CFA, positive control). More interestingly, the 80 nm anionic lipid particles were the most efficient antigen carrier for eliciting higher humoral immune response, as well as cellular immune response characterized by a strong secretion of gamma interferon (IFN-γ). These results associated with the demonstrated non-immunogenicity of the NLC carrier by itself open new avenues for the design of smart sub-unit vaccines containing properly engineered lipid nanoparticles which could stimulate or orient the immune system in a specific way.