Extracellular matrix scaffold-assisted tumor vaccines induce tumor regression and long-term immune memory

Injectable scaffold delivery is an immune engineering strategy to enhance the efficacy and reliability of cancer vaccine immunotherapy. The composition and structure of the biomaterial scaffold determines both vaccine release kinetics and inherent immune stimulation via the scaffold host response. Extracellular matrix (ECM) scaffolds prepared from decellularized tissues initiate an acute alternative inflammatory response following implantation, which facilitates wound healing following tumor resection and promotes local cancer immune surveillance. However, it remains unknown whether this environment is compatible with generating protective anti-tumor cytotoxic immunity with local immunotherapy delivery. Here, we engineered an ECM scaffold-assisted therapeutic cancer vaccine that maintained an immune microenvironment consistent with tissue reconstruction. Immune adjuvants MPLA, GM-CSF, and CDA were screened in a cancer vaccine formulated for decellularized small intestinal submucosa (SIS) ECM scaffold co-delivery. Though MPLA and GM-CSF showed the greatest increase in local myeloid cell infiltration, we found that the STING pathway adjuvant CDA was the most potent inducer of cytotoxic immunity with SIS-ECM scaffold delivery. Further, CDA did not diminish hallmark ECM immune responses needed in wound healing such as high Il4 cytokine expression. SIS scaffold delivery enhanced therapeutic vaccine efficacy using CDA and the antigen ovalbumin, curing greater than 50% of established EG.7 tumors in young mice and 75% in 24-week-old mature mice, compared to soluble components alone (0% cured). SIS-ECM scaffold assisted vaccination extended antigen exposure, was dependent on CD8+ cytotoxic T cells, and generated long term anti-tumor memory at least 7 months post-vaccination in both young and mature-aged mice. This study shows that an ECM scaffold is a promising delivery vehicle to enhance cancer vaccine efficacy while being orthogonal to characteristics of pro-healing immune hallmarks. ### Competing Interest Statement The authors have declared no competing interest.