Abstract A034: VV-iVP55: A Superior Vaccinia Virus Platform with Enhanced Oncolytic Potency and Immunogenicity

Abstract

Abstract This research introduces VV-iVP55, a conditionally replicating vaccinia virus platform, as a promising alternative to thymidine kinase (Tk) deleted oncolytic vaccinia viruses. The unique feature of VV-iVP55 is its growth control using doxycycline, a trait not found in conventional Tk-deleted viruses. Laboratory studies revealed that VV-iVP55 achieves higher virus titers and lower cell viability in B16-F10 and MC38 syngeneic models compared to Tk-deleted viruses. Notably, VV-iVP55 demonstrated lower toxicity in immunocompromised mice upon doxycycline withdrawal, unlike Tk-deleted viruses that showed significant toxicity. In vivo efficacy studies further highlighted the superiority of VV-iVP55 over Tk-deleted viruses in CT26 and B16 subcutaneous models, as well as MC38 subcutaneous and intraperitoneal models. An immune microenvironment analysis conducted six days post-intratumoral injection revealed beneficial alterations induced by VV-iVP55, such as increased T and B cell content in the tumor and reduced MDSCs in both the tumor and spleen. Moreover, VV-iVP55 was linked to a significant change in T cell differentiation. Unlike the PBS and Tk viruses, which showed almost complete differentiation towards effector T cells, VV-iVP55 maintained a substantial population of T cells in naive and transition phases, significantly in both CD4 and CD8 T cells. This likely led to lower expression of exhaustion markers PD1, TIM3, TIGIT, and LAG3, suggesting less exhaustion and more potential for immune response. In summary, VV-iVP55 emerges as a powerful alternative to Tk-deleted oncolytic vaccinia viruses, offering enhanced immunogenicity, controlled toxicity, and preserved oncolytic properties. Citation Format: Reza Rezaei, Taha Azad, Julia Petryk, John C. Bell. VV-iVP55: A Superior Vaccinia Virus Platform with Enhanced Oncolytic Potency and Immunogenicity [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A034.