title: Primary Role for Toll-Like Receptor-Driven Tumor Necrosis Factor Rather than Cytosolic Immune Detection in Restricting Coxiella burnetii Phase II Replication within Mouse Macrophages.
abstract: Coxiella burnetii replicates within permissive host cells by employing a Dot/Icm type IV secretion system (T4SS) to translocate effector proteins that direct the formation of a parasitophorous vacuole. C57BL/6 mouse macrophages restrict the intracellular replication of the C. burnetii. Nine Mile phase II (NMII) strain. However, eliminating Toll-like receptor 2 (TLR2) permits bacterial replication, indicating that the restriction of bacterial replication is immune mediated. Here, we examined whether additional innate immune pathways are employed by C57BL/6 macrophages to sense and restrict NMII replication. In addition to the known role of TLR2 in detecting and restricting NMII infection, we found that TLR4 also contributes to cytokine responses but is not required to restrict bacterial replication. Furthermore, the TLR signaling adaptors MyD88 and Trif are required for cytokine responses and restricting bacterial replication. The C. burnetii NMII T4SS translocates bacterial products into C57BL/6 macrophages. However, there was little evidence of cytosolic immune sensing of NMII, as there was a lack of inflammasome activation, T4SS-dependent cytokine responses, and robust type I interferon (IFN) production, and these pathways were not required to restrict bacterial replication. Instead, endogenous tumor necrosis factor (TNF) produced upon TLR sensing of C. burnetii NMII was required to control bacterial replication. Therefore, our findings indicate a primary role for TNF produced upon immune detection of C. burnetii NMII by TLRs, rather than cytosolic PRRs, in enabling C57BL/6 macrophages to restrict bacterial replication.
authors.affiliation: Cell and Molecular Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: William P
authors.initials: WP
authors.lastname: Bradley
authors.affiliation: Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Boyer
authors.affiliation: Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Hieu T
authors.initials: HT
authors.lastname: Nguyen
authors.affiliation: Cell and Molecular Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: L Dillon
authors.initials: LD
authors.lastname: Birdwell
authors.affiliation: Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Janet
authors.initials: J
authors.lastname: Yu
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Juliana M
authors.initials: JM
authors.lastname: Ribeiro
authors.affiliation: Cell and Molecular Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Susan R
authors.identifier: http://orcid.org/0000-0002-8155-4528
authors.initials: SR
authors.lastname: Weiss
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Dario S
authors.identifier: http://orcid.org/0000-0002-7856-7512
authors.initials: DS
authors.lastname: Zamboni
authors.affiliation: Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, USA.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Roy
authors.affiliation: Cell and Molecular Biology Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA sunshin@mail.med.upenn.edu.|Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Sunny
authors.initials: S
authors.lastname: Shin
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D016997:Coxiella burnetii / Q000502:physiology*; D003600:Cytosol; D005786:Gene Expression Regulation / Q000502:physiology; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D053594:Myeloid Differentiation Factor 88; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; C507780:Myd88 protein, mouse; C476286:Ticam1 protein, mouse; C495342:TLR2 protein, human; C493487:Tlr4 protein, mouse