Abstract 3562: LOAd732 - a novel oncolytic adenovirus with enhanced immunostimulatory properties and resistance to immunosuppression
Authors: Wenthe Jessica , Eriksson Emma , Lövgren Tanja , Moreno Rafael , Alemany Ramon , Loskog Angelica 
Published: June 2022

Abstract
Immunotherapy aims at activating or re-activating the immune system to create an anti-tumor response that could lead to eradication of the tumor cells. Central is the activation of dendritic cells (DCs) capable of presenting tumor antigens to T cells that can expand and kill tumor cells. However, the tumor is a harsh environment for the adaptive immune system and many of the conditions needed for the establishment of an immune response are lacking. Oncolytic viral therapy presents an opportunity to overcome the immunosuppression in tumors by destroying tumor cells, releasing antigens and immunostimulatory factors. The effects of the oncolytic virus can be further amplified by the introduction of transgenes expressed by the virus. LOAd oncolytic adenoviruses belong to a platform of Ad5/35 adenoviruses that have replication restricted to tumor cells. The viruses express human immunostimulatory transgenes under a CMV promotor that enables expression in all infected cells. LOAd703, encoding trimerized (TMZ)-CD40L and 4-1BBL, is under clinical investigation in solid tumors. Herein we present the data from the investigation of our novel oncolytic adenovirus LOAd732 that encodes for three human transgenes; TMZ-CD40L, 4-1BBL and IL-2. Infection of the human cell lines Mel526 and Mel624 with LOAd732 led to cell killing as was evaluated by MTS viability assay and to expression of the transgenes, TMZ-CD40L, 4-1BBL and IL-2 evaluated by flow cytometry and ELISA. Moreover the immmunostimulatory function of LOAd732 was investigated by infecting immature dendritic cells, differentiated from CD14+ monocytes using GM-CSF and IL-4. Flow cytometry assay revealed that DCs infected with LOAd732 showed a mature profile with expression of activation markers and co-stimulatory molecules such as CD80, CD83, CD86, CD70, ICAM-1, and MHC molecules. Analysis of supernatants from the cultures with multiplex immunoassay (MDS technology) showed that LOAd732 DCs produce IL-12p70, IL-15, IL-21 and CXCL10. To assess the functionality of the DCs infected by LOAd732, the capacity of the cells to expand antigen-specific T cells were investigated in a CMV model system where DCs from CMV positive donors are pulsed with a CMV peptide and co-cultured with autologous T cells. LOAd732 infected DCs could expand CMV-specific CD8+ T cells. Since the tumor microenvironment often is immunosuppressive, TGF-β and IL-10 was added to the co-cultures to model these conditions. The addition of the immunosuppressing cytokines did not affect LOAd732 capacity to expand the antigen-specific T cells.
In conclusion, LOAd732 infected DCs express activation markers and co-stimulatory molecules and produce cytokines necessary for the initiation of an immune response. Moreover the DCs are functional and can expand antigen-specific T cells and protect them from TGF-β and IL-10 suppression.
Citation Format: Jessica Wenthe, Emma Eriksson, Tanja Lövgren, Rafael Moreno, Ramon Alemany, Angelica Loskog. LOAd732 - a novel oncolytic adenovirus with enhanced immunostimulatory properties and resistance to immunosuppression [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 3562.