STING Activating Synthetic Nanovaccine for HPV-Induced Cancers

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Abstract Human papilloma virus (HPV) infection is the primary cause of cervical cancer in women worldwide. In addition, HPV-induced head and neck and anogenital cancers are also rising in both male and female populations in the US. Immunotherapy is becoming an important component of cancer care in addition to surgery, radiation therapy and chemotherapy. Checkpoint inhibitors and adoptive cell transfer therapy such as chimeric antigen receptor T cell therapy have shown durable patient response in melanoma, non-small cell lung cancer, and renal cell cancer patients. However, immune-related toxicity, high costs, and unsustainable memory T cell immunity are major limitations for the rapid adoption of T cell therapy in patient care. Recently, we established a STING-activating polymeric nanovaccine to boost tumor-specific T cell immunity against various solid cancers. The nanovaccine consists of a physical mixture of an antigen with a synthetic polymeric nanoparticle, PC7A NP, which generated robust cytotoxic T lymphocyte (CTL) response and long-term memory T cell immunity with low systemic cytokines release. PC7A nanovaccine produced potent tumor growth inhibition and increased long-term survival in melanoma, colorectal cancer and human papilloma virus (HPV)-E6/E7 tumor models in mice. In this application, we will test the hypothesis that direct binding of PC7A to STING will lead to STING redistribution from ER to Golgi for innate stimulation and furthermore, inhibiting immune checkpoints elevated by STING activation will overcome tumor resistance to PC7A nanovaccine. We will carry out the following specific aims: (1) Investigate the biochemical mechanism of STING activation by PC7A polymer. (2) Investigate the mechanism of vaccine resistance. (3) Investigate nanovaccine efficacy in a transgenic mouse model displaying human HLA-A2. Successful execution of this research will lead to a synthetic nanovaccine for immunotherapy of HPV- induced cancers. The proposed PC7A nanovaccine and checkpoint inhibition strategy can also be adopted for immunotherapy of other types of cancers.