Inflammasome components caspase-1 and adaptor protein apoptosis-associated speck-like proteins are important in resistance to Cryptosporidium parvum |
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Authors: | Nina N McNair Chetna Bedi Dmitry M Shayakhmetov Michael J Arrowood Jan R Mead |
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Institution: | 1. Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, 30322, USA;2. Atlanta VA Medical Center, Decatur, GA, 30033, USA;3. Lowance Center for Human Immunology, USA;4. Emory Vaccine Center, Emory University School of Medicine, Atlanta, GA, 30322, USA;5. Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Infection, Atlanta, GA 30329, USA |
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Abstract: | Cryptosporidium spp. are opportunistic protozoan parasites that infect epithelial cells in the intestinal tract and cause a flu-like diarrheal illness. Innate immunity is key to limiting the expansion of parasitic stages early in infection. One mechanism in which it does this is through the generation of early cytokines, such as IL-18. The processing and secretion of mature IL-18 (and IL-1β) is mediated by caspase-1 which is activated within an inflammasome following the engagement of inflammasome-initiating sensors. We examined how the absence of caspase-1 and caspase-11, the adapter protein Asc, and other inflammasome components affects susceptibility to cryptosporidial infection by these and other key cytokines in the gut. We found that Casp-11?/?Casp-1?/? knockout mice have increased susceptibility to Cryptosporidium parvum infection as demonstrated by the 35-fold higher oocyst production (at peak infection) compared to wild-type mice. Susceptibility correlated with a lack of IL-18 in caspase-1 and caspase1/11 knockout mice, whereas IL-18 is significantly elevated in wildtype mice. IL-1β was not generated in any significant amount following infection nor was any increased susceptibility observed in IL-1β knockout mice. We also show that the adapter protein Asc is important to susceptibility, and that the caspase-1 canonical inflammasome signaling pathway is the dominant pathway in C. parvum resistance. |
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Keywords: | IL-18 IL-1β Associated speck-like protein Nod-like receptors Inflammasome |
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