A genetic screen identifies a protective type III interferon response to Cryptosporidium that requires TLR3 dependent
Alexis R Gibson1, Adam Sateriale1, Jennifer E Dumaine1
1Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
Abstract:
Cryptosporidium is a leading cause of severe diarrhea and diarrheal-related death in children worldwide. As an obligate intracellular parasite, Cryptosporidium relies on intestinal epithelial cells to provide a niche for its growth and survival, but little is known about the contributions that the infected cell makes to this relationship. Here we conducted a genome wide CRISPR/Cas9 knockout screen to discover host genes that influence Cryptosporidium parvum infection and/or host cell survival. Gene enrichment analysis indicated that the host interferon response, glycosaminoglycan (GAG) and glycosylphosphatidylinositol (GPI) anchor biosynthesis are important determinants of susceptibility to C. parvum infection and impact on the viability of host cells in the context of parasite infection. Several of these pathways are linked to parasite attachment and invasion and C-type lectins on the surface of the parasite. Evaluation of transcript and protein induction of innate interferons revealed a pronounced type III interferon response to Cryptosporidium in human cells as well as in mice. Treatment of mice with IFNλ reduced infection burden and protected immunocompromised mice from severe outcomes including death, with effects that required STAT1 signaling in the enterocyte. Initiation of this type III interferon response was dependent on sustained intracellular growth and mediated by the pattern recognition receptor TLR3. We conclude that host cell intrinsic recognition of Cryptosporidium results in IFNλ production critical to early protection against this infection.
Insights
Cryptosporidium infection triggers a type III interferon response in intestinal cells, mediated by TLR3. This interferon lambda (IFNλ) response is crucial for protecting against parasite burden and severe outcomes.
Area of Science:
- Host-pathogen interactions
- Immunology
- Gastroenterology
Background:
- Cryptosporidium is a major cause of diarrheal disease in children globally.
- The role of host intestinal cells in Cryptosporidium infection is poorly understood.
- Understanding host factors is key to developing new treatments.
Purpose of the Study:
- To identify host genes influencing Cryptosporidium parvum infection and host cell survival.
- To elucidate the host cell's intrinsic defense mechanisms against Cryptosporidium.
- To investigate the role of the interferon response in Cryptosporidium infection.
Main Methods:
- Genome-wide CRISPR/Cas9 knockout screen in host cells.
- Gene enrichment analysis to identify key pathways.
- Evaluation of interferon response in human cells and mouse models.
- Investigating the role of TLR3 and STAT1 signaling.
Main Results:
- Host interferon response, GAG, and GPI anchor biosynthesis pathways are critical for C. parvum susceptibility and cell viability.
- A strong type III interferon response (IFNλ) is induced by Cryptosporidium in human and mouse cells.
- IFNλ treatment reduced parasite burden and protected mice from severe outcomes, dependent on STAT1 signaling.
- The IFNλ response is initiated by TLR3 and triggered by intracellular parasite growth.
Conclusions:
- Host cell recognition of Cryptosporidium leads to IFNλ production, a vital early defense mechanism.
- Targeting the type III interferon pathway offers a potential therapeutic strategy against Cryptosporidium infections.
- This study highlights the importance of host cell intrinsic immunity in controlling parasitic infections.
