In Vivo Imaging Tracking and Immune Responses to Nanovaccines Involving Combined Antigen Nanoparticles with a Programmed Delivery

Combined nanovaccine can generate robust and persistent antigen-specific immune responses. A combined nanovaccine was developed based on antigen-loaded genipin-cross-linked-polyethyleneimine–antigen nanoparticles and in vivo multispectral fluorescence imaging tracked the antigen delivery of combined nanovaccine. The inner layer antigen nanoparticles carried abundant antigens by self-cross-linking for persistent immune response, whereas the outer antigen on the surface of antigen nanoparticles provided the initial antigen exposure. The delivery of combined nanovaccine was tracked dynamically and objectively by the separation of inner genipin cross-linked antigen nanoparticle and the outer fluorescent antigen. The immune responses of the combined nanovaccine were evaluated including antigen-specific CD4⁺ and CD8⁺ T-cell responses, IgG antibody level, immunological memory, and CD8⁺ cytotoxic T lymphocyte responses. The results indicated that the inner and outer antigens of combined vaccine can be tracked in real time with a programmed delivery by the dual fluorescence imaging. The programmed delivery of the inner and outer antigens induced strong immune responses with a combination of a quick delivery and a persistent delivery. With adequate antigen exposure, the dendritic cells were effectively activated and matured, and following T cells were further activated for immune response. Compared with a single nanoparticle formulation, the combined nanovaccine exactly elicited a stronger antigen-specific immune response.