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Detection of a microbial metabolite by STING regulates inflammasome activation in response to Chlamydia trachomatis infection

Published version
Peer-reviewed

Type

Article

Change log

Authors

Webster, SJ 
Brode, S 
Ellis, L 
Fitzmaurice, TJ 
Elder, MJ 

Abstract

The innate immune system is a critical component of host defence against microbial pathogens, but effective responses require an ability to distinguish between infectious and non-infectious insult to prevent inappropriate inflammation. Using the important obligate intracellular human pathogen Chlamydia trachomatis; an organism that causes significant immunopathology, we sought to determine critical host and pathogen factors that contribute to the induction of inflammasome activation. We assayed inflammasome activation by immunoblotting and ELISA to detect IL-1β processing and LDH release to determine pyroptosis. Using primary murine bone marrow derived macrophages or human monocyte derived dendritic cells, infected with live or attenuated Chlamydia trachomatis we report that the live organism activates both canonical and non-canonical inflammasomes, but only canonical inflammasomes controlled IL-1β processing which preceded pyroptosis. NADPH oxidase deficient macrophages were permissive to Chlamydia trachomatis replication and displayed elevated type-1 interferon and inflammasome activation. Conversely, attenuated, non-replicating Chlamydia trachomatis, primed but did not activate inflammasomes and stimulated reduced type-1 interferon responses. This suggested bacterial replication or metabolism as important factors that determine interferon responses and inflammasome activation. We identified STING but not cGAS as a central mediator of interferon regulated inflammasome activation. Interestingly, exogenous delivery of a Chlamydia trachomatis metabolite and STING ligand-cyclic di-AMP, recovered inflammasome activation to attenuated bacteria in a STING dependent manner thus indicating that a bacterial metabolite is a key factor initiating inflammasome activation through STING, independent of cGAS. These data suggest a potential mechanism of how the innate immune system can distinguish between infectious and non-infectious insult and instigate appropriate immune responses that could be therapeutically targeted.

Description

Keywords

Animals, Chlamydia Infections, Chlamydia trachomatis, Cyclic AMP, Dendritic Cells, Female, Humans, Inflammasomes, Interferon Type I, Interleukin-1beta, Macrophages, Male, Membrane Proteins, Mice, Nucleotidyltransferases

Journal Title

PLoS Pathogens

Conference Name

Journal ISSN

1553-7366
1553-7374

Volume Title

13

Publisher

Public Library of Science (PLoS)
Sponsorship
Medical Research Council (MR/M020134/1)
Medical Research Council (G1001765)
Arthritis Research Uk (None)
Arthritis Research Uk (None)
Biotechnology and Biological Sciences Research Council (BB/H003916/1)
Wellcome Trust (108045/Z/15/Z)
This work was supported by a Medical Research Council grant (RG61445) to JCG and HJSG http://www.mrc.ac.uk/, an Arthritis Research UK Senior Fellowship (RG61798) grant to JCG http://www.arthritisresearchuk.org/, the National Institute for Health Research http://www.nihr.ac.uk/ Cambridge Biomedical Research Centre http://www.cambridge-brc.org.uk/ and Cambridge Arthritis Research Endeavour (CARE) http://www.cambridge-arthritis.org.uk/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.