Long-Lasting, Fine-Tuned Anti-tumor Activity of Recombinant Listeria monocytogenes Vaccine Is Controlled by Pyroptosis and Necroptosis Regulatory and Effector Molecules

One of the main objectives of developing new anti-cancer vaccine strategies is to effectively induce CD8+ T cell-mediated anti-tumor immunity. Live recombinant vectors, notably Listeria mono-cytogenes, have been shown to elicit a robust in vivo CD8+ T cell response in preclinical settings. Significantly, it has been demonstrated that Listeria induces inflammatory/immunogenic cell death mechanisms such as pyroptosis and necroptosis in immune cells that favorably control immunological responses. Therefore, we postulated that the host's response to Listeria-based vec-tors and the subsequent induction of CD8+ T cell-mediated immunity would be compromised by the lack of regulatory or effector molecules involved in pyroptosis or necroptosis. To test our hy-pothesis, we used recombinant L. monocytogenes carrying the ovalbumin gene (LM.OVA) to vac-cinate wild-type (WT), caspase-1/11-/-, gsdmd-/-, ripk3-/-, and mlkl-/- C57Bl/6 mice. We performed an in vivo cytotoxicity assay to assess the efficacy of OVA-specific CD8+ T lymphocytes in eliminat-ing target cells in wild-type and genetically deficient backgrounds. Furthermore, we evaluated the specific anti-tumor immune response in mice inoculated with B16F0 and B16F0.OVA mela-noma cell lines. Our findings demonstrated that while caspase-1/11 and GSDMD deficiencies in-terfere with the rapid control LM.OVA infection, of the KO seems to contribute to the early acti-vation of OVA-specific CTL responses. In contrast, individual deficiency of each one of these pro-teins negatively impact the generation of long-lasting effector CD8+ T cells.