Combined encapsulation of a tumor antigen and immune cells using a self-assembling immunostimulatory DNA hydrogel to enhance antigen-specific tumor immunity.

Our previous study demonstrated that the incorporation of a tumor antigen into a self-assembling DNA hydrogel, comprised of a DNA containing un-methylated cytosine-phosphate-guanine (CpG) dinucleotides (CpG DNA), efficiently induced antigen-specific tumor immunity after intra-tumoral injection into tumor-bearing mice. We hypothesized that the additional incorporation of immune cells, the target for the antigen and immunostimulatory CpG DNA, would increase the antitumor response. To prove this, immune cells were also encapsulated into the CpG DNA hydrogel and delivered along with the antigen. Mouse dendritic DC2.4 cells maintained their form even after incorporation into the DNA hydrogel. The incorporation of mouse macrophage-like J774.1 cells and RAW264.7 cells into CpG DNA hydrogel did not significantly affect their viability. J774.1, RAW264.7, DC2.4, and mouse bone marrow-derived dendritic cells (BMDCs) were efficiently activated when incorporated into the CpG DNA hydrogel. The CpG DNA hydrogel incorporated with both the tumor antigen and BMDCs effectively induced antigen-specific immune responses, and retarded tumor growth following intradermal administration before and after tumor inoculation without severe local and systemic adverse events. These data indicate that the combined delivery of a tumor antigen and immune cells using an immunostimulatory CpG DNA hydrogel is effective in inducing antigen-specific antitumor immunity.