Author ORCID Identifier
https://orcid.org/0000-0001-7547-0427
Date of Award
Spring 2025
Document Type
Thesis (Ph.D.)
Department or Program
Microbiology and Immunology
First Advisor
James B. Bliska
Abstract
Yersinia and Pseudomonas use a T3SS to secrete effectors into host cells that inhibit phagocytosis and modulate immune responses, such as inflammasome activation. Inflammasomes promote the activation of the proinflammatory protease caspase-1. The activation of an inflammasome sensor in response to a signal or ligand initiates the assembly of the inflammasome leading to activation of caspase-1 which cleaves GSDMD and pro-inflammatory cytokines IL-1β and IL-18 into their mature forms. As neutrophils are recruited in large quantities to sites of infection, they are excellent candidates to drive inflammasome dependent responses. Neutrophils have been shown to produce multiple inflammasomes, like pyrin and NLRC4. For this study, I developed a primed neutrophil infection model to study the role of effectors in regulating inflammasome activity during infection. This model was validated by infection with Y. pseudotuberculosis and shows a requirement for the pyrin inflammasome for secretion of IL-1β and pyroptosis in response to ∆yopM. I also showed that pyrin is dispensable for inflammasome activation during infection with P. aeruginosa. Using a mouse model of infection, I show that the expression of pyrin in myeloid cells promotes protection against infection with Y. pseudotuberculosis ∆yopM or yopJC172A∆yopM, and this prevents the formation of microcolonies in the spleen. Finally, using an ex vivo model I investigated the role of ExoS and the hypersecretion of ExoS from P. aeruginosa on neutrophil cell death pathways. Using a combination of ExoS mutants and CF clinical strains, as well as various mouse lines containing defects in inflammasome components, I show that the activation of the NLRC4 inflammasome in neutrophils is inhibited by ExoS. Inhibition of NLRC4 by ExoS promotes necrosis and this is enhanced when ExoS is hypersecreted. Additionally, I show that ExoS ADPRT activity promotes this inhibition, and infection using a mutant lacking ExoS ADPRT activity activates NLRC4-dependent IL-1βsecretion and pyroptosis. Regulation of inflammasomes by bacterial effectors in macrophages have been well documented, however these interactions in neutrophils have been less well studied. Here, I extend our understanding of neutrophil inflammasomes and the role of effectors in regulating cell death responses to infection with Y. pseudotuberculosis or P. aeruginosa.
Original Citation
Reuven AD et al. ExoS Effector in Pseudomonas aeruginosa Hyperactive Type III Secretion System Mutant Promotes Enhanced Plasma Membrane Rupture in Neutrophils. 2025. PLoS Pathogens.
Recommended Citation
Reuven, Arianna D., "Neutrophil Inflammatory Death Regulation by Bacterial Type III Secreted Effectors" (2025). Dartmouth College Ph.D Dissertations. 386.
https://digitalcommons.dartmouth.edu/dissertations/386
