Engineering of gold nanoparticles for effective cancer vaccines

Abstract

Many nanomaterials were recently incorporated into development of vaccines due to their advantages in kinetics of antigen exposure and cellular processing. While physicochemical properties of nanomaterials might be determining factors in the induction of immune response, their ultimate influence on the immune response has not been definitively established and rational vaccine design is challenging. In second chapter, we studied the effect of gold nanoparticle size on lymph node delivery and induction of CD8+ T-cell response. Specifically, immune responses to sub-40nm gold nanoparticles (GNPs) which can directly drain into lymph nodes were assessed. To study the size effect of GNPs on cellular immune response, GNPs with diameters of 7, 14, 28 nm were successfully conjugated with recombinant ovalbumin, resulting in OVA-GNPs with hydrodynamic diameter (HD) of ~10, 22, and 33 nm. DC cell uptake and cross-presentation efficiency in vitro was increased in size-dependently, and lymph node delivery of OVA-GNPs in vivo was higher in 22 and 33-nm of OVA-GNPs compared to 10 nm OVA-GNPs. An ex vivo restimulation assay using OVA as an antigen revealed that OVA-GNP (22, 33 nm) immunized groups had higher frequencies of OVA-specific CD8+ T cells

moreover, these cells were shown to be poly-functional. 22-nm OVA-GNPs showed greater antitumor efficacy, and higher infiltration of CD8+ T-cells and greater tumor cell apoptosis and cell death than 10-nm OVA-GNPs. Taken together, our results suggest that the size threshold for induction of potent cellular responses and T-cell poly-functionality by GNPs lies between 10 nm and 22 nm, and highlight the importance of nanoparticle size as a critical parameter in designing and developing nanoparticle-based vaccines. In third chapter, we studied the effect of GNP surface chemistry on T-cell cross-priming by dendritic cells. Specifically, we constructed a library of peptide-gold nanoparticle-antigen hybrids system with tunable surface chemistry by decorating the surface of 14 nm GNPs with OVA antigens and various peptide ligands. Most of synthesized hybrids were physiologically stable and efficiently taken up by dendritic cells. Through screening of a library of peptide-gold nanoparticle-antigen hybrids using DC2.4 cells and OT-1 T-cells, we could identify the heat hybrids with maximized cross-priming efficiency. Also, hybrids nanoparticles coated with peptides ending with amino acids containing carboxyl or hydroxyl side chain induced higher level of cross-priming than those containing hydrophobic and aromatic ring. Those heat hybrids indeed more efficiently primed BMDCs to induce higher level of OT-1 T-cell proliferation. These results showed the usefulness of our screening methods and the potential of heat hybrids to be used as antigen-pulsing agents for development of dendritic cell-based vaccine. This work also highlights the importance of nanoparticle surface chemistry in T-cell cross-priming process, and informs the principle for designing of antigen-pulsing agents for DC priming.