Recombinant Oncolytic Vaccinia Virus Expressing The Extracellular Domain Of CD155 For Cancer Therapy

BackgroundImmunotherapy holds promise for effective cancer treatment.Different from other traditional therapies,it educates the immune system to eliminate tumors.Immune checkpoint regulates the balance of co-stimulatory signaling and co-inhibitory signaling to control T cell-mediated immune responses.PD-1 and CTLA-4 are two typical molecules that regulate co-inhibitory signaling.At present,the monoclonal antibody like anti-PD-1/PD-L1 have been widely used in clinical therapy for many tumors.Oncolytic virotherapy(OV)is a rising star in cancer immunotherapy.OV possesses multiple distinguished mechanisms to kill malignant cells: 1)directly oncolysis,in turn the dead cells release viral particles to infect adjacent tumor cells,which amplifies the oncolytic effect;2)induce immunogenic cell death,which lysed tumor cells release abundant danger associated pattern molecules and tumor associated antigens to stimulate immune responses;3)By inserting foreign therapeutic genes into the viral genome,a recombinant virus expresses genes of interest to regulate tumor microenvironment for a more effective therapy.CD155 is a cell membrane molecule and often over-expressed on tumor cells.Many studies show that CD155 is involved in cell adhesion,contact inhibition,invasion,and proliferation.In addition,CD155 is the ligand of CD226 and TIGIT,respectively.However,CD155/CD226 is an immune activator signaling pathway,whereas CD155/TIGIT is an immune inhibitory signaling pathway.Others and our previous studies showed that CD155 has more affinity with TIGIT than CD226.Recent studies showed that TIGIT is associated with exhaustion of cytotoxic T lymphocytes and NK cells,blockade of TIGIT could reverse exhaustion these immune cells.MethodsIn this study,we constructed a recombinant oncolytic vaccinia virus(western reserve strain)expressing the extracellular domain of murine CD155(s CD155).The plasmid carrying the s CD155 gene was inserted into the wild-type vaccinia virus by Homologous recombination.followed by drug-screening and identification to obtain a recombinant virus VV-s CD155.Then VV-s CD155 was amplified in Hela S3 cells and titer was determined by plaque forming unit.VV expressing EGFP(VV-EGFP)was constructed in the same way and used as control in this study.Viral replication,protein secretion and oncolysis were determined in vitro by TCID50,western blot,and CCK-8.The recruitment and infiltration of immune cells were determined in an ascitic HCC mouse model by flowcytometry.The anti-tumor efficacy of VV-s CD155 was investigated in several subcutaneous tumor models including breast cancer and two colorectal cancers.Tumor growth curves and survival were monitored.Results 1.VV-s CD155 effectively infects cancer cells and secrets target protein soluble CD155.2.VV-s CD155 replicates effectively in serial of cancer cells and has the similar oncolytic efficacy as the control virus.3.Vaccinia virus significantly recruits lymphocytes infiltration to the tumor microenvironment.4.VV-s CD155 exhibits a potent anti-tumor effect in several solid tumors and significantly prolonged survival of tumor bearing mice.SignificanceWe have successfully constructed a recombinant oncolytic vaccinia virus expressing the extracellular domain of CD155(VV-s CD155).VV-s CD155 replicates effectively in many cancer cells and exhibits the anti-tumor effects both in vitro and in vivo.Our study provides a novel biological weapon for effective cancer immunotherapy.