Investigating the role of pericyte infection in Vesicular Stomatitis Virus stimulated immune activation

Abstract

Oncolytic viruses (OVs) are a type of cancer immunotherapy. Although OVs’ exact mechanism of action remains to be elucidated, it is believed that they activate the immune system by selectively infecting and lysing tumor cells. Recent studies demonstrate that non-tumor cells in the tumor microenvironment (TME) may also assist in OV-mediated tumor clearance. We have observed that Vesicular Stomatitis Virus (VSV), an OV, infects pericytes in the TME of various murine tumor models. Pericytes are vascular mural cells that maintain blood vessel physiology and take part in the inflammatory response. Despite a lack of tumor cell infections in our model, VSV treatment facilitated tumor regression in a CD8+ T-cell dependent manner. Therefore, the overall aim of this project was to investigate if pericytes play in VSV-mediated anti-tumor action. An in vitro model, using human placental pericytes (HPCs), was created to characterize the transcriptional and translational profile of VSV-infected HPCs over time. Some of the topmost differentially expressed (DE) genes and proteins of VSV-infected HPCs comprise of chemokines (MIP-1β, IFNL1 and CXCL10) and surface markers involved in immune regulation (SIGLEC1, CD69 and ICAM1). Pathways related to chemokine activity and innate immune response were also found to be enriched in the transcriptome and proteome of VSV-infected HPCs. Since multiple chemokines were secreted by VSV-infected HPCs, we sought to determine the impact of contents released by VSV-infected HPCs i.e. conditioned media (VSV CM) on human dermal microvascular endothelial cells (HDMECs). The transcriptional and translational response of HDMECs was assessed by exposing them to UV-irradiated VSV CM or titer matched VSV diluted in control media (VSV CTL). The results indicate that the elements secreted by VSV-infected HPCs increase the immune cell recruitment potential of HDMECs. This is evidenced by the significantly increased expression of immune cell recruiting genes (CSF2, IL1B and CXCL3) and immune adhesion proteins (SELE and ICAM1) in HDMECs treated with VSV CM versus those exposed to VSV CTL. Overall, the results indicate that VSV-infected HPCs exhibit a phenotype that likely alerts the immune system. VSV-infected HPCs also release soluble factors that activate endothelial cells to potentially facilitate immune cell recruitment.