Oncolytic adenoviruses coated with MHC-I tumor epitopes increase the anti-tumor immunity and efficacy against melanoma

The stimulation of the immune system using oncolytic adenoviruses (OAds) has attracted significant interest and several studies suggested that OAd´s immunogenicity might be important for their efficacy. Therefore, we developed a versatile and rapid system to adsorb tumor-specific major histocompatibility complex class I (MHC-I) peptides onto the viral surface to drive the immune response towards the tumor-epitopes. By studying the model epitope SIINFEKL we demonstrated that the peptide-coated OAd (PeptiCRAd) retains its infectivity and the cross-presentation of the modified-exogenous epitope on MHC-I is not hindered. We then showed that the SIINFEKL-targeting PeptiCRAd achieves a superior anti-tumor efficacy and increases the percentage of anti-tumor CD8+ T-cells and mature epitope-specific dendritic cells in vivo. PeptiCRAds loaded with clinically relevant tumor epitopes derived from tyrosinase-related protein 2 (TRP-2) and human gp100 could reduce the growth of primary-treated tumors and secondary-untreated melanomas, promoting the expansion of antigen-specific T-cell populations. Finally, we tested PeptiCRAd in humanized mice bearing human melanomas. In this model, a PeptiCRAd targeting the human melanoma-associated antigen A1 (MAGE-A1) and expressing granulocyte and macrophage colony-stimulating factor (GM-CSF) was able to eradicate established tumors and increased the human MAGE-A1-specific CD8+ T-cell population. Herein we show that the immunogenicity of OAds plays a key role in their efficacy and it can be exploited to direct the immune response system towards exogenous tumor epitopes. This versatile and rapid system overcomes the immunodominance of the virus and elicits a tumor-specific immune response, making PeptiCRAd a promising approach for clinical testing.