Optimized armed oncolytic adenoviral vaccines (PeptiCRAd) for an enhanced anti-cancer immune response.

In according to the last available data, cancer is the second cause of death in many countries, following only cardiovascular diseases. As the risk of cancer increases in the elderly and also because of other factors such as tobacco, low vegetable and fruit intake, pollution, new treatments are needed to replace or combine the classical treatments such as surgery, radiotherapy and chemotherapy. Among the new therapeutic approaches, one emerging and promising field is the immunotherapy, which aims to elicit de novo anti-tumour response and/or boost the pre-existing anti-tumour immunity. The cancer immunotherapy consists of different approaches such as oncolytic viruses, which are able to replicate only in cancer cells, and the immune checkpoint inhibitors, which revert or prevent T-cell exhaustion. Both approaches showed efficacy in eliciting anti-tumour immune response, but solid tumours, such as triple negative breast cancer, show poor immunogenic and immunosuppressive and could benefit from a combination of these treatments. Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer currently resistant to available treatment approaches. Therefore, in the present study, we decided to evaluate the efficacy of a tumour-specific vaccine platform based on peptide-coated oncolytic adenovirus (PeptiCRAd) that we had previously developed for different tumours. PeptiCRAd is a versatile and rapid system to adsorb tumour-specific major histocompatibility complex class I (MHC-I) peptides onto the viral surface to drive the immune response toward the tumour epitopes. In fact, the combination in a single treatment of the adjuvancy of the virus with the immunological targeting of tumour-derived peptides converts the powerful anti-viral immune response obtained with viral vaccines into a more efficient anti-tumoural response. In the present work, we adapted PeptiCRAd in a poor immunogenic and high immunosuppressive tumour model such as TNBC and for the first time we improved the PeptiCRAd platform adding on the same oncolytic vaccine tumour peptides restricted for both MHC-I and MHC-II in order to harm TCD8+ and TCD4+ lymphocytes and to obtain a more efficient and complete immune response. Tumour cells evade immune recognition and destruction by down regulating MHC-I and up-regulating PDL-1. Thus, we chose and characterized human (MDA-MB-436) and mouse (4T1) triple negative breast cancer cell lines for the expression of MHC-I, MHC-II and PDL-1, demonstrating that they are a solid model for our immunotherapeutic approach. As PeptiCRAd relies on Ad-5-D24-CpG, we demonstrated that has similar cytopathic effect (CPE) to Ad-5/3-D24, already validated in human model of TNBC. In the first set of in vivo experiments, we observed that oncolytic vaccines coated with a combination of MHC-I and MHC-II peptides induced a stronger response compared to those coated with either MHC-I or MHC-II peptides. We also observed that administration of mixture of equal concentrations of oncolytic vaccines coated with MHC-I or MHC-II peptides was less efficient compared to the double coated formulation. Therefore, we conclude that MHC-I and MHC-II peptides have to be loaded on the same surface to maximize the effect. Next, we evaluated the synergistic effect of administration of the PeptiCRAd-D.C. preparation with anti-PDL1 antibody in TNBC. Our results clearly demonstrated a significant improvement of the oncolytic vaccine efficacy when administrated in combination with anti-PDL1. Finally, we translated our treatment in a relevant human model of TNBC. We performed a Cytotoxic T-lymphocytes (CTL) killing assay in a co-culture experiment with human tumours. In vitro we pulsed with our vaccine human peripheral blood mononuclear cell (PBMCs) HLA-matched with the tumours and we added them to the tumour sample and cancer cells viability was then evaluated. The tumour peptides selected in the above experiment for the PeptiCRAd preparation were selected from well-known human triple negative breast cancer antigens. In addition, one tumour peptide was selected by using an improved version of ligandome analysis. In conclusion, we have demonstrated for the first time the efficacy of PeptiCRAd technology based oncolytic vaccine in a challenging model of TNBC. In addition, we observe that vaccine coating with a combination of MHC-I and MHC-II restricted peptides is more effective than the previously used MHC-I restricted peptides coating, leading to a further improvement of the system.