Fine tuning of CpG spatial distribution with DNA origami  for improved cancer vaccination
Multivalent presentation of ligands often enhances receptor activation and downstream signaling. DNA origami offers precise nanoscale spacing of ligands, a potentially useful feature for therapeutic nanoparticles. Here, we use a square block DNA origami platform to explore the importance of spacing of CpG oligonucleotides. CpG engages Toll-like receptors and thereby acts to activate dendritic cells. Through in vitro cell-culture studies and in vivo tumor-treatment models, we demonstrate that square blocks induce Th1 immune polarization when CpG is spaced at 3.5 nm. We observe that this DNA origami vaccine enhances DC activation, antigen cross-presentation, CD8+ T cell activation, Th1-polarized CD4+ activation and natural killer cell activation. The vaccine also synergizes effectively with anti-PD-L1 for improved cancer immunotherapy in melanoma and lymphoma models and induces long-term T cell memory. Our results suggest that DNA origami may serve as a platform for controlling adjuvant spacing and co-delivering antigens in vaccines. Overall design: The immature BMDCs were treated with different vaccines for 1 day and collected by TRIzol (Invitrogen). The samples were send to Genewiz for RNA sequencing.