A DNA-polymer hybrid nanocomplex based bi-adjuvant vaccine for tumor immunotherapy

The immunosuppressive tumor microenvironment (TME) seriously impedes the cancer immunotherapy; Toll-like receptors (TLRs) agonists combination is emerging as vaccine adjuvant in reprogramming tumor immune microenvironment. Herein, we develop a supramolecular DNA-polymer hybrid nanocomplex-based bi-adjuvant vaccine for tumor immunotherapy. In the nanocomplex, the co-assembly of TLR9 agonist (CpG) and TLR7 agonist (loxoribine) was achieved via dynamic DNA assembly and boron chemistry. Poly-N-isopropyl acrylamide (PNIPAM) served as the framework of the nanocomplex, and meanwhile, designer DNA sequences were introduced as cross-linkers in the nanoframework to trigger the hybridization chain reaction (HCR)-based assembly of CpG sequences containing hairpins. The polymer framework was decorated with phenylboronic acid to capture and release loxoribine via reversible formation of cyclic boric acid ester. A lipid shell was coated on the outside of the CpG and loxoribine co-loaded nanocomplex to prevent the leakage of loxoribine in plasma. After intravenous injection, the nanocomplex was internalized by the tumor-associated immune cells via lysosomal related pathways. CpG and loxoribine synergistically stimulated TLR9 and TLR7 receptors, thus leading to the conversion of suppressive M2 macrophage to active M1 macrophage, maturation of dendritic cells, and activation of T cells. The dual activation of TLR9 and TLR7 effectively reprogramed tumor immune microenvironments in vivo, wherein robust CD8+ T cell response and efficient tumor regression were achieved. This work provides a unique design concept for the TLR agonists combination-based nanovaccine for tumor immunotherapy.