IDDF2023-ABS-0003 Experimental study of a new recombinant vaccinia virus carrying CXCL9 and IL-7 double genes combined with immune effector cells and immune checkpoint blocking triple therapy for gastric cancer

Background

To prepare a new recombinant oncolytic vaccinia virus carrying CXCL9 and IL-7 double genes by molecular biological method, and to preliminarily explore the significance of the combined strategy of oncolytic virus infection, immune effector cell and immune checkpoint blocking in the treatment of gastric cancer through animal model treatment experiment.

Methods

The recombinant vaccinia virus eukaryotic expression plasmid pSC65-CXCL9-IL7 carrying both CXCL9 and IL-7 genes was constructed step by step by genetic engineering, and then the vaccinia virus strain was recombined in the eukaryotic cells of the vector. After repeated screening and purification with a limited dilution method, purified recombinant oncolytic poxvirus VV-CXCL9-IL7 was obtained. The anti-tumor effect on gastric cancer cells and the function of producing and secreting IL-7 and CXCL9 molecules were preliminarily verified by cell experiments in vitro. VV-CXCL9-IL7 was used to intervene and treat the tumor-bearing animal model of subcutaneous implanted tumor of gastric cancer in nude mice. The triple intervention group of recombinant vaccinia virus intratumoral injection+cytotoxic T lymphocytes (CTL)+immune checkpoint blocker (PD-1 monoclonal antibody), the single intervention group of three measures, the dual intervention group and the blank control group were established. After the intervention according to the established groups, tumor growth curve method, tumor inhibition rate method and animal bioluminescence method were used to detect the tumor treatment effect, and the concentrations of CXCL9 and IL-7 in serum and tissue homogenate of animals in each group were detected by Elisa method.

Results

The recombinant oncolytic poxvirus VV-CXCL9-IL7 was successfully constructed. In vivo, the production and release of chemokines IL-7 and CXCL9 were preliminarily verified in serum and tissue homogenate of animals. The therapeutic intervention results of animal models showed that the tumor growth was most strongly inhibited in the triple intervention group.

Conclusions

The combination of recombinant oncolytic poxvirus+CTL+PD-1 monoclonal antibody has a strong anti-tumor effect in the intervention experiment of gastric cancer animal models, and has potential clinical application for gastric cancer, which can be injected intratumorally through endoscopy.