Salmonella species (especially the S. enterica serotypes typhi and typhimurium) cause disease in ~90 million people every year worldwide. Salmonella infects both phagocytic immune cells (such as macrophages), as well as non-phagocytic cells. When Salmonella infects macrophages, it triggers a rapid, pro-inflammatory form of death called pyroptosis. Unlike the case with macrophages, less is known about Salmonella-triggered cell death responses in non-phagocytic cells, such as intestinal epithelial cells and fibroblasts. As these are the some of the first cell types infected by Salmonella, understanding how they respond to this bacterium, and whether pyroptotic clearance mechanisms are at play in these cells, is an important objective. Our preliminary data demonstrate that infecting epithelial and fibroblastic cells with Salmonella and later exposing them to IFN- ?, mimicking the environment of infection in the intestine, induces a novel form of cell death that is neither pyroptosis nor any of the other reported mechanisms of programmed cell death, including apoptosis, necroptosis, or autophagy. Mechanistically, we find that IFN-? ruptures the Salmonella-containing vacuole in non-phagocytic cells, releasing Salmonella into the cytosol, from where the bacterium induces cell death. Results from a CRISPR screen suggest that such cell death is the consequence of toxified mitochondria. Based on these and other observations, we hypothesize that IFN-?-induced cell death in non-phagocytic cells is a host defense mechanism that destroys infected intestinal epithelial cells to limit Samonella spread in vivo. To test this hypothesis, we have generated mice in which IFN-? signaling can be selectively ablated in either intestinal epithelial cells or phagocytes.
The Aims of this proposal are to (1) elucidate the mechanism by which Salmonella kills non- phagocytic cells upon IFN-? exposure; and (2) test the in vivo role of IFN-? signaling and cell death in Salmonella- infected intestinal epithelial cells during acute Salmonella infection. The successful completion of these Aims will reveal the mechanism and in vivo role of a IFN-?-driven new death pathway engaged by the host during anti- Salmonella immune responses.

Public Health Relevance

Salmonella causes disease in ~90 million people every year worldwide. We have identified a novel mechanism by which the anti-microbial cytokine IFN-? triggers the death of Salmonella-infected non-phagocytic cells. This mechanism may explain how Salmonella is controlled at the site of infection by gut epithelial cells, with potentially important immunological and therapeutic ramifications.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21AI142114-02
Application #
9964656
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Alexander, William A
Project Start
2019-07-01
Project End
2021-06-30
Budget Start
2020-07-01
Budget End
2021-06-30
Support Year
2
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Research Institute of Fox Chase Cancer Center
Department
Type
DUNS #
064367329
City
Philadelphia
State
PA
Country
United States
Zip Code
19111