SUMMARY Inflammasomes are cytosolic innate immune complexes that form in response to a variety of pathogen- associated or stress-induced stimuli. Activated inflammasomes recruit Caspase-1, which initiates downstream inflammatory signaling. Genetic deletion of inflammasome components in mice has demonstrated the critical importance of inflammasomes during infection by viral, bacterial and eukaryotic pathogens. In addition, the inappropriate activation of inflammasomes has been linked to numerous auto-inflammatory and auto-immune diseases in humans. Host-pathogen coevolution is a major factor underlying the genetic and molecular determinants of cross- species transmission and infectious disease. The antagonistic nature of host-pathogen interactions can drive recurrent cycles of adaptation and counter-adaptation. These evolutionary ‘arms races’ drive rapid molecular innovation. Thus, the unique history of pathogen encounters of each lineage has driven species-specific adaptations. It should therefore not be surprising that laboratory mice are poor models of many human-specific or human-adapted pathogens. In this proposal I outline my vision to leverage the species-specific nature of host-pathogen interactions to develop improved models of human immunity and pathogenesis. Using a combination of evolution-guided and mechanism-focused approaches, I have made the following discoveries: 1) the Dengue virus (DENV) protease NS2B3 activates the human (but not mouse) NLRP1 inflammasome. DENV is the first known pathogen that activates human NLRP1. This finding supports a formerly unrecognized role for NLRP1 in host immunity and pathogenesis to DENV infection. 2) the enteric bacterial pathogen Shigella antagonizes the human (but not mouse) NAIP/NLRC4 inflammasome. Based on this finding, I have found that NLRC4-deficient mice are highly susceptible to enteric infection and. exhibit hallmarks of intestinal inflammation. Thus, I have established the first mouse model of Shigellosis. This proposal seeks to boldly expand on these observations using innovative approaches to generate new or significantly refine models of human infectious disease. I propose to 1) establish a new model of DENV immunity and pathogenesis, and 2) advance the development of the Shigellosis mouse model. Both DENV and Shigella are important human pathogens, which combined cause >200 million infections per year. Improved DENV infection models is a clear but unmet need, and until my Shigellosis mouse model, mice were thought to be refractory to Shigella enteric infection. Thus, the successful completion of the stated goals will significantly impact human infectious disease research.