Autologous Tumor Vaccine Modified With Recombinant New Castle Disease Virus Expressing IL-7Promotes Anti-tumor Immune Response

Objective: Autologous tumor cell modified with non-lytic Newcastle DiseaseVirus (ATV/NDV) is a promising vaccine for cancer immunotherapy. IL-7plays acritical role in lymphocyte development and homeostasis. In order to improve theefficacy of ATV/NDV, we used the reverse genetic system to construct the recombinantNDV which could express murine IL-7[NDV-LX/(IL-7)] by inserting IL-7gene intothe genome of non-lytic NDV strain LX.The recombinant NDV-LX/(IL-7) was usedfor the preparation of ATV-NDV-LX/(IL-7). We want to know whether theATV-NDV-LX/(IL-7) could enhance the anti-tumor effect compared with thetraditionalATV-NDV.Methods：(1) Constructing the recombinant NDV which could express RFP(NDV-LX/RFP)or IL-7[NDV-LX/(IL-7)] by using the reverse genetic system.(2) Detecting the biological function of NDV-LX/(IL-7) in vitro. Preparation theATV-NDV by using NDV-LX/RFP and NDV-LX/(IL-7) and detect the killing capacityof splencytes induced byATV-NDV-LX/RFP andATV-NDV-LX/(IL-7).(3) Tumor prophylaxis model： mice were subcutaneously injected with PBS、B16-F10autologous tumor vaccine、B16-LX/RFP and B16-LX/(IL-7) for two times.14days after the last injection, the mice were subcutaneously injected with B16-F10melanoma cells. The tumor growth curve was observed and the splencytes wereharvested for FACS analysis and cytotoxicity assay.(4) Tumor therapeutic model: mice were subcutaneously injected with B16-F10 melanoma cells.7days later, the mice were given PBS、B16-F10autologous tumorvaccine、B16-LX/RFP and B16-LX/(IL-7) by subcutaneous injection for total of4times, twice a week. The tumor growth curve was observed and the splencytes and thetumor infiltrating lymphocytes (TIL) were harvested for FACS analysis andcytotoxicity assay.(5) In the tumor therapeutic model,3days before sacrificing the mice, the micewere given i.p. injection of100ug EdU.3days later, the mice were sacrificed, theproportion of EdU+CD8+T cell in spleen and TIL were detected by FACS analysis.(6) In the tumor therapeutic model, the mice were i.p. injected with anti-CD8depletion antibody one day after tumor cell injection. The tumor growth curve wasobserved to determine whether the increased anti-tumor effect induced byB16-LX/(IL-7) was mediated by CD8+T cells.Results：(1) We successfully constructed the recombinant NDV-LX/RFP andNDV-LX/(IL-7). The two recombinant NDV strains were non-lytic. High quantity ofIL-7could be detected in the supernatant of virus-infected tumor cells.(2) We used the ATV-NDV-LX/(IL-7) to stimulate the splencytes in vitro, theresults showed an increased tumor killing capacity compared with the control group.(3) In the tumor therapeutic model, tumor growth was significantly prevented inthe mice of ATV-NDV-LX/(IL-7) group. The proportion and absolute numbers ofCD8+IFN-(IL-7) group.the spleen were significantly increased in theATV-NDV-LX/(IL-7) group.(4) In the tumor therapeutic model, mice in the ATV-NDV-LX/(IL-7) groupshowed better anti-tumor effect. The proportion and absolute numbers ofCD8+IFN-tumor therapethe spleen were significantly increased in theATV-NDV-LX/(IL-7) group. The proportion and absolute numbers ofCD8+IFN-significantly increased in the ATV-NDV-LX/(IL-7) group. The proportionand absolute num group.(5) In the CD8+T cell proliferation assay, we didn’t see any significantly difference of EdU+CD8+T cell in spleen and TIL, suggesting IL-7did not promoteCD8+T cell prolifetion.(6) In the CD8+T cell depletion assay，the anti-tumor effect was diminished afterCD8+T cell depletion.Conclusion：The autologous tumor vaccine modified by NDV-LX/(IL-7) showedan increased anti-tumor effect compared with the traditional ATV-NDV. This increasedanti-tumor effect was mediated by CD8+T cells.