Pyroptosis-inducing active caspase-1 as a genetic adjuvant in anti-cancer DNA vaccination

Pyroptosis is a recently discovered form of inflammatory programmed necrosis characterized by caspase1-mediated and gasdermin D-dependent cell death leading to the release of pro-inflammatory cytokines such as Interleukin-1 beta (IL-18). Here, we evaluated whether pyroptosis could be exploited in DNA vaccination by incorporating a constitutively active variant of caspase-1 to the antigen-expressing DNA. In vitro, transfection with constitutively active caspase-1 DNA induced pro-IL-18 maturation and IL-18 release as well as gasdermin D-dependent cell death. To test active caspase-1 as a genetic adjuvant for the induction of antigen-specific T cell responses, mice were vaccinated intradermally with a DNA vaccine consisting of the active caspase-1 plasmid together with a plasmid encoding an ovalbuminderived CD8 T cell epitope. Active caspase-1 accelerated and amplified antigen-specific CD8 T cell responses when administered simultaneously with the DNA vaccine at an equimolar dose. Moreover, upon challenge with melanoma cells expressing ovalbumin, mice vaccinated with the antigen vaccine adjuvanted with active caspase-1 showed significantly better survival compared to the non-adjuvanted group. In conclusion, we have developed a novel genetic adjuvant that for the first time employs the pyroptosis pathway to improve DNA vaccination against cancer. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).