TMIC-23. A SEQUENTIAL IMAGING STRATEGY TO STUDY ONCOLYTIC VIRUS INFILTRATION, REPLICATION AND TUMOR MICROENVIRONMENTAL PERTURBATIONS, EX VIVO

The use of oncolytic viruses (OV) as therapeutic agents for glioblastoma multiforme (GBM) is an emerging clinical focus. OV have the potential to reinvigorate the immune contexture in the tumor microenvironment (TME). However, current pre-clinical models are insufficient to study the immune effects of OV. Here, we describe an imaging approach using a human ex-vivo platform to study the effects of OV on tumor-associated immune cells in GBM. Using the rQNestin34.5v.1 herpes simplex virus (rQNestin) we treated human GBM ex-vivo, incorporating autologous patient-derived peripheral-blood mononucleated cells and whole tissue fragments. We treated GBM (n=10) with rQNestin, capable of expressing GFP, and profiled GFP expression as a proxy for replication. We analyzed serial sections of H&E, HSV-1, and multiplex immunohistochemistry (mIHC) to investigate the impact of rQNestin on the spatial context of the immune compartment. Cell Signaling Technology antibodies, CD3e (D7A6E™,ID:85061), CD68 (D4B9C,ID:76437), CD11c (D3V1E,49420), MHC-Class II ((HLA-DRB)LGII-612.14,NA) and Pan-keratin (C11,4545) were optimized for identifying intratumoral T-cells (CD3e+), macrophages (CD68) and dendritic cells (CD11c+MHCII+) in relation to the surrounding tissue architecture (pan cytokeratin). Using the serial-section imaging approach, we overlaid infiltration and replication of rQNestin. Additionally, strategic sectioning identified dynamic spatial alterations in the immune compartment, via visualization of the tumor-immune interface with indications of infiltration and replication. Quantitative pathology showed dynamic re-arrangement of immune cells - in spatial orientation, quantity and localization, relative to the tumor, under rQnestin pressure, ex-vivo. Here, we report that our ex-vivo human tumor model can be used to evaluate the effects of OV in the TME – not only viral replication but also the direct effect on the immune compartment. In particular, we can assess changes in immune subsets post-OV treatment in a 3-D manner, therefore providing greater insight into their spatial arrangement and distribution. These findings could develop our understanding of anti-tumor OV mechanisms.