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In vivo discrimination of type 3 secretion system-positive and -negative Pseudomonas aeruginosa via a caspase-1-dependent pathway. Infect Immun 2010; 78:4744-53. [PMID: 20823203 DOI: 10.1128/iai.00744-10] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Microbe-associated molecular patterns are recognized by Toll-like receptors of the innate immune system. This recognition enables a rapid response to potential pathogens but does not clearly provide a way for the innate immune system to discriminate between virulent and avirulent microbes. We find that pulmonary infection of mice with type 3 translocation-competent Pseudomonas aeruginosa triggers a rapid inflammatory response, while infection with isogenic translocation-deficient mutants does not. Discrimination between translocon-positive and -negative bacteria requires caspase-1 activity in bone marrow-derived cells and interleukin-1 receptor signaling. Thus, the activation of caspase-1 by bacteria expressing type 3 secretion systems allows for rapid recognition of bacteria expressing conserved functions associated with virulence.
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Skerrett SJ, Wilson CB, Liggitt HD, Hajjar AM. Redundant Toll-like receptor signaling in the pulmonary host response to Pseudomonas aeruginosa. Am J Physiol Lung Cell Mol Physiol 2006; 292:L312-22. [PMID: 16936244 DOI: 10.1152/ajplung.00250.2006] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of pulmonary defenses against Pseudomonas aeruginosa requires myeloid differentiation factor 88 (MyD88), an adaptor for Toll-like receptor (TLR) signaling. To determine which TLRs mediate recognition of P. aeruginosa, we measured cytokine responses of bone marrow cells from wild-type mice and mice lacking TLR2 (TLR2(-/-)), TLR4 (TLR4(-/-)), TLR2 and TLR4 (TLR2/4(-/-)), or MyD88 (MyD88(-/-)) to wild-type P. aeruginosa and to fliC P. aeruginosa, which lacks the TLR5 ligand flagellin. Mice also were challenged with aerosolized bacteria to determine cytokine responses, lung inflammation, and bacterial clearance. TNF induction required MyD88 and was absent in TLR2/4(-/-) cells in response to fliC but not wild-type P. aeruginosa, whereas TLR2(-/-) cells exhibited augmented responses. In vivo, TLR4(-/-) mice responded to wild-type P. aeruginosa with reduced cytokine production and inflammation, but intact bacterial clearance, while TLR2(-/-) mice had partially impaired cytokine responses and delayed bacterial killing despite normal inflammation. When challenged with fliC, MyD88(-/-) mice failed to mount early cytokine and inflammatory responses or control bacterial replication, resulting in necrotizing lung injury and lethal disseminated infection. TLR4(-/-) and TLR2/4(-/-) mice responded to fliC infection with severely limited inflammatory and cytokine responses but intact bacterial clearance. TLR2(-/-) mice had partially reduced cytokine responses but augmented inflammation and preserved bacterial killing. These data indicate that TLR4- and flagellin-induced signals mediate most of the acute inflammatory response to Pseudomonas and that TLR2 has a counterregulatory role. However, MyD88-dependent pathways, in addition to those downstream of TLR2, TLR4, and TLR5, are required for pulmonary defense against P. aeruginosa.
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Affiliation(s)
- Shawn J Skerrett
- Division of Pulmonary and Critical Care Medicine, Harborview Medical Center, 325 Ninth Avenue, Box 359640, Seattle, WA 98104, USA.
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Feuillet V, Medjane S, Mondor I, Demaria O, Pagni PP, Galán JE, Flavell RA, Alexopoulou L. Involvement of Toll-like receptor 5 in the recognition of flagellated bacteria. Proc Natl Acad Sci U S A 2006; 103:12487-92. [PMID: 16891416 PMCID: PMC1567905 DOI: 10.1073/pnas.0605200103] [Citation(s) in RCA: 241] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Toll-like receptors (TLRs) are key components of the immune system that detect microbial infection and trigger antimicrobial host defense responses. TLR5 is a sensor for monomeric flagellin, which is a component of bacterial flagella known to be a virulence factor. In this study we generated TLR5-deficient mice and investigated the role of TLR5 signaling in the detection of flagellin and antibacterial immune responses to Salmonella typhimurium and Pseudomonas aeruginosa. We found that TLR5 is essential for the recognition of bacterial flagellin both in vivo and ex vivo. TLR5 contribution to antibacterial host response to i.p. infection with S. typhimurium or intranasal administration of P. aeruginosa may be masked by TLR4 or other sensing mechanisms. By using radiation bone marrow chimera, we showed that upon i.p. injection of flagellin immune responses are mediated by lymphoid cells, whereas resident cells are required for the initiation of response upon intranasal flagellin administration. These results suggest that flagellin recognition in different organs is mediated by distinct TLR5-expressing cells and provide insights into the cooperation of the TLR5 and TLR4 signaling pathways used by the innate immune system in the recognition of bacterial pathogens.
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Affiliation(s)
- Vincent Feuillet
- *Centre d’Immunologie de Marseille–Luminy, Université de la Méditerranée, Case 906, 13288 Marseille, France
- Institut National de la Santé et de la Recherche Médicale, Unité 631, 13288 Marseille, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6102, 13288 Marseille, France
| | - Samir Medjane
- *Centre d’Immunologie de Marseille–Luminy, Université de la Méditerranée, Case 906, 13288 Marseille, France
- Institut National de la Santé et de la Recherche Médicale, Unité 631, 13288 Marseille, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6102, 13288 Marseille, France
| | - Isabelle Mondor
- *Centre d’Immunologie de Marseille–Luminy, Université de la Méditerranée, Case 906, 13288 Marseille, France
- Institut National de la Santé et de la Recherche Médicale, Unité 631, 13288 Marseille, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6102, 13288 Marseille, France
| | - Olivier Demaria
- *Centre d’Immunologie de Marseille–Luminy, Université de la Méditerranée, Case 906, 13288 Marseille, France
- Institut National de la Santé et de la Recherche Médicale, Unité 631, 13288 Marseille, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6102, 13288 Marseille, France
| | - Philippe P. Pagni
- *Centre d’Immunologie de Marseille–Luminy, Université de la Méditerranée, Case 906, 13288 Marseille, France
- Institut National de la Santé et de la Recherche Médicale, Unité 631, 13288 Marseille, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6102, 13288 Marseille, France
| | - Jorge E. Galán
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536; and
| | - Richard A. Flavell
- Section of Immunobiology and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520
- To whom correspondence may be addressed at:
Section of Immunobiology, Yale University School of Medicine, 300 Cedar Street, New Haven, CT 06520. E-mail:
| | - Lena Alexopoulou
- *Centre d’Immunologie de Marseille–Luminy, Université de la Méditerranée, Case 906, 13288 Marseille, France
- Institut National de la Santé et de la Recherche Médicale, Unité 631, 13288 Marseille, France
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6102, 13288 Marseille, France
- To whom correspondence may be addressed at:
Centre d’Immunologie de Marseille–Luminy, 163 Avenue de Luminy, Case 906, 13288 Marseille, Cedex 9, France. E-mail:
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