Abstract 3542: Oncolytic adenovirus encoding transgenes for IFN-beta and recombinant CD40 ligand promotes conventional dendritic cell activation and trafficking with enhanced tumor infiltrating lymphocytes for effective cancer immunotherapy
Authors: Zheng Hong , Antonia Scott , Cantwell Mark J. , Yu Xiaoqing , Beg Amer A. 
Published: June 2022

Abstract
Clinical studies have shown that pre-existing tumor-reactive T cells are critically important for effective cancer immunotherapy. Methods to augment the number and functionality of tumor-reactive T cells are therefore vital. Given that cytotoxic CD8 T cell priming requires conventional dendritic cells (cDC), we hypothesized that strategies to enhance cDC functionality in tumors would augment anti-tumor CD8 T cell responses. CD40 and type 1 IFN signaling pathways each promote the cross-presentation function of cDCs to activate CD8 T cells. However, it is unclear whether these pathways are functionally independent and whether their combined activation in tumor cDC leads to higher levels of T cell priming. Using adenovirus vectors, we tested the impact of expression of IFNβ and a chimeric membrane-stable CD40 ligand (MEM40) in syngeneic mouse tumor models. Compared to intratumoral administration of each individual transgene-encoding adenovirus, combined MEM40 + IFNβ expression resulted in the best tumor growth control, highest levels of tumor infiltrating lymphocytes (TILs), and systemic CD8 T cell responses. MEM40 and IFNβ were independently capable of enhancing T cell responses as we found IFNβ in CD40-/- mice and MEM40 in type 1 IFN receptor IFNAR1-/- mice induced a strong T cell response. These results were consistent with a cDC-mediated priming mechanism. Studies with cDC1 deficient BATF3-/- mice revealed a crucial role of this cDC subset in MEM40 + IFNβ induced T cell responses. IFNβ alone and MEM40 + IFNβ triggered increase in lymph node (LN) homing receptor CCR7 expression in cDC1 concurrent with a reduction in cDC1 in tumors and gain in tumor draining LNs. Simultaneously, combined MEM40 + IFNβ combination led to the highest levels of expression of CD80 and CD86 co-stimulatory molecules in both tumor and LN cDC1. Single cell (sc)-RNA sequencing of tumor DCs further showed that MEM40 + IFNβ led to the highest proportion of a recently defined mature/regulatory cDC subset characterized by high expression of CCR7, CD40 and IL12b. Applying these results towards an effective therapeutic modality, we developed a dual-transgene-armed MEM40 + IFNβ expressing conditionally replicative adenovirus (MEM-288) that simultaneously confers tumor-specific oncolysis and promotes tumor antigen release. MEM-288 drives MEM40 + IFNβ expression in freshly resected human lung tumors and generates potent anti-tumor responses as a monotherapy and in combination with immune checkpoint inhibitors. Furthermore, MEM-288 induced enhancement of tumor-reactive TILs and provides a rationale for studies to determine whether MEM-288 pre-treatment generates a superior TIL product for more effective adoptive T cell therapy.
Citation Format: Hong Zheng, Scott Antonia, Mark J. Cantwell, Xiaoqing Yu, Amer A. Beg. Oncolytic adenovirus encoding transgenes for IFN-beta and recombinant CD40 ligand promotes conventional dendritic cell activation and trafficking with enhanced tumor infiltrating lymphocytes for effective cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3542.