Final Report Summary - REVERSIBLEINFECTION (Pathogen and commensal immunity compared in a reversible infection model that uncouples immunity from pathogen immune evasion)
The goal of this project was the development and application of novel, so-called reversibly colonizing, strains of non-pathogenic and pathogenic gram-negative bacteria. These require external supplementation with the bacteria-specific amino acids D-alanine and meso-diaminopimelic acid to synthesize their cell walls and grow. This cell wall amino acid auxotrophy enables the highly transient and fully reversible experimental intestinal colonization, respectively infection, of germ-free animals with live bacteria. This strictly limits innate and adaptive immune activation to the initial phase of bacteria-mucosal interaction.
We engineered auxotrophic strains of the pathogens Salmonella typhimurium and Citrobacter rodentium that fully transiently colonized germ-free mice. These strains retained their epithelial cell invasiveness and adhesiveness that characterizes the pathogenicity of S. typhimurium and C. rodentium, respectively. This allowed us to effectively isolate the initial pathogenic bacterial-mucosal interaction and study the resulting protective innate and adaptive immune responses. These analyses revealed the very rapid induction of highly protective intestinal innate immunity in a bacterial pathogenicity factor-dependent manner. Moreover, reversible infection revealed bacterial pathogenicity factor-driven induction of protective adaptive immunity against re-exposure to the wild-type pathogen. Our experiments further revealed a distinct essentiality of central pattern recognition receptor signaling pathways for pathogen defense and the induction of adaptive immunity. The knowledge generated in this project is relevant for the future development of intestinal vaccines and bacteriotherapies.
We engineered auxotrophic strains of the pathogens Salmonella typhimurium and Citrobacter rodentium that fully transiently colonized germ-free mice. These strains retained their epithelial cell invasiveness and adhesiveness that characterizes the pathogenicity of S. typhimurium and C. rodentium, respectively. This allowed us to effectively isolate the initial pathogenic bacterial-mucosal interaction and study the resulting protective innate and adaptive immune responses. These analyses revealed the very rapid induction of highly protective intestinal innate immunity in a bacterial pathogenicity factor-dependent manner. Moreover, reversible infection revealed bacterial pathogenicity factor-driven induction of protective adaptive immunity against re-exposure to the wild-type pathogen. Our experiments further revealed a distinct essentiality of central pattern recognition receptor signaling pathways for pathogen defense and the induction of adaptive immunity. The knowledge generated in this project is relevant for the future development of intestinal vaccines and bacteriotherapies.