The Role And Mechanism Of Macrophages In The Immunotherapeutic Efficacy Of OHSV2

BackgroundOncolytic virus combined with immune checkpoint blockade has shown potential clinical application significance.The role and mechanism of innate immune cells in oncolytic virus therapy of tumors have not been elucidated.Recent studies have found that the immune checkpoint protein SIRPa exists on macrophages.When the ligand CD47 molecule expressed by tumor cells binds to it,it sends a "don’t eat me" signal to macrophages,which blocks the macrophages from recognizing and killing the tumor cells.Therefore,this study intends to explore the efficacy and molecular mechanism of oncolytic herpes simplex virus type Ⅱ(oHSV2)combined with anti-SIRPa antibody in the treatment of tumors.ObjectiveTo explore the effect of oHSV2 on the function of macrophages in the process of tumor treatment,as well as the efficacy and molecular mechanism of the combination of antiSIRPα antibody and oHSV2.MethodsWe validated the polarizing ability of oHSV2 treatment on RAW264.7 by in vitro experiments(CCK8 assay,macrophage typing and killing assay).We further validated the polarizing ability of oHSV2 treatment on macrophages by in vivo experiments(clodronate liposomes-treated mouse colon cancer CT26 model).The efficacy of oHSV2 combined with anti-SIRPα antibody in anti-tumor therapy was verified by mouse colon cancer CT26 model and breast cancer 4T1 model.We preliminarily elucidated the effect of oHSV2 combined with anti-SIRPa antibody on the tumor microenvironment by pathological detection and transcriptome sequencing of the tumor tissue of the mouse colon cancer CT26 model.ResultsoHSV2 induced M1-type polarization of macrophages in vitro.A mouse model of oHSV2 combined with clodronate liposomes induced M1-type polarization of macrophages and established long-lasting anti-tumor immune memory.oHSV2 combined with anti-SIRPa antibody effectively inhibited tumor growth in mouse colon cancer CT26 model and breast cancer 4T1 model,and significantly prolonged the survival time of mice.oHSV2 combined with anti-SIRPα antibody established effective anti-tumor immunity by remodeling the tumor immune microenvironment.The expression of Tnk2/Ack1 gene was significantly different between the oHSV2 combined with anti-SIRPa antibody treatment group and the control group.We found that Tnk2/Ack1 gene was closely related to tumor immunity and prognosis of colon cancer patients,and we established a prognosis model of colorectal cancer patients with Tnk2/Ack1 related genes by analyzing the TCGA database.ConclusionsoHSV2 effectively induced macrophage polarization to M1 type both in vivo and in vitro,thereby exerting innate antitumor immune response.oHSV2 combined with anti-SIRPa antibody enhanced its oncolytic activity,inhibited tumor growth and prolonged mouse survival time.The possible mechanism was to induce the polarization of macrophages to M1 type,thereby exerting their natural anti-tumor immune potential,which provided valuable clues for improving the clinical efficacy of oncolytic virus.oHSV2 combined with anti-SIRPα antibody induced the decreased expression of anti-tumor immune-related gene Tnk2/Ack1,which might affect the survival of colon cancer patients.