251
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Duclos S, Clavarino G, Rousserie G, Goyette G, Boulais J, Camossetto V, Gatti E, LaBoissière S, Pierre P, Desjardins M. The endosomal proteome of macrophage and dendritic cells. Proteomics 2011; 11:854-64. [PMID: 21280226 DOI: 10.1002/pmic.201000577] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 11/08/2010] [Accepted: 11/29/2010] [Indexed: 01/13/2023]
Abstract
The essential roles of the endovacuolar system in health and disease call for the development of new tools allowing a better understanding of the complex molecular machinery involved in endocytic processes. We took advantage of the floating properties of small latex beads (sLB) on a discontinuous sucrose gradient to isolate highly purified endosomes following internalization of small latex beads in J774 macrophages and bone marrow-derived dendritic cells (DC). We particularly focused on the isolation of macrophages early endosomes and late endosomes/lysosomes (LE/LYS) as well as the isolation of LE/LYS from immature and lipopolysaccharide-activated (mature) DC. We subsequently performed a comparative analysis of their respective protein contents by MS. As expected, proteins already known to localize to the early endosomes were enriched in the earliest fraction of J774 endosomes, while proteins known to accumulate later in the process, such as hydrolases, were significantly enriched in the LE/LYS preparations. We next compared the LE/LYS protein contents of immature DC and mature DC, which are known to undergo massive reorganization leading to potent immune activation. The differences between the protein contents of endocytic organelles from macrophages and DC were underlined by focusing on previously poorly characterized biochemical pathways, which could have an unexpected but important role in the endosomal functions of these highly relevant immune cell types.
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Affiliation(s)
- Sophie Duclos
- Département de Pathologie et Biologie Cellulaire, Université de Montréal, Montréal, QC, Canada
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252
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Leichtle A, Hernandez M, Lee J, Pak K, Webster NJ, Wollenberg B, Wasserman SI, Ryan AF. The role of DNA sensing and innate immune receptor TLR9 in otitis media. Innate Immun 2011; 18:3-13. [PMID: 21239460 DOI: 10.1177/1753425910393539] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Otitis media (OM), a common infectious disease in children, is associated with bacterial middle ear (ME) infection. Toll-like receptors (TLRs) are important mediators of innate immune responses, and TLR9 specifically recognizes the unmethylated cytidine-phosphate-guanosine (CpG) motifs in bacterial DNA. Additional sensors of foreign DNA have recently been identified. The role of DNA sensing and TLR9 was investigated in a murine model of OM induced by non-typeable Haemophilus influenzae (NTHi). Expression of genes related to DNA-sensing pathways involved in innate immunity was assessed via DNA microarray, qPCR and immunohistochemistry. Middle ear responses to NTHi were examined in wild-type and TLR9(-/-) mice by histopathology and bacterial culture. Expression of TLR9 signaling genes was modestly up-regulated during OM, as was TLR9 protein in both ME mucosal cells and infiltrating leukocytes. However, genes known to be regulated by CpG DNA were dramatically up-regulated, as were genes involved in DNA sensing by DIA, Pol-III and AIM2. Toll-like receptor 9 deletion significantly prolonged the inflammatory response induced by NTHi in the ME and delayed bacterial clearance. The results suggest that DNA sensing via TLR9 plays a role in OM pathogenesis and recovery. Alternative forms of DNA sensing may also contribute to OM.
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Affiliation(s)
- Anke Leichtle
- Department of Surgery/Otolaryngology, University of Lübeck, Lübeck, Germany
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253
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Barbalat R, Ewald SE, Mouchess ML, Barton GM. Nucleic acid recognition by the innate immune system. Annu Rev Immunol 2011; 29:185-214. [PMID: 21219183 DOI: 10.1146/annurev-immunol-031210-101340] [Citation(s) in RCA: 437] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Receptors of the innate immune system recognize conserved microbial features and provide key signals that initiate immune responses. Multiple transmembrane and cytosolic receptors have evolved to recognize RNA and DNA, including members of the Toll-like receptor and RIG-I-like receptor families and several DNA sensors. This strategy enables recognition of a broad range of pathogens; however, in some cases, this benefit is weighed against the cost of potential self recognition. Recognition of self nucleic acids by the innate immune system contributes to the pathology associated with several autoimmune or autoinflammatory diseases. In this review, we highlight our current understanding of nucleic acid sensing by innate immune receptors and discuss the regulatory mechanisms that normally prevent inappropriate responses to self.
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Affiliation(s)
- Roman Barbalat
- Division of Immunology & Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, 94720-3200, USA
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254
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Affiliation(s)
- Jae-Min Yuk
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon, Korea
- Infection Signaling Network Research Center, Chungnam National University School of Medicine, Daejeon, Korea
| | - Eun-Kyeong Jo
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon, Korea
- Infection Signaling Network Research Center, Chungnam National University School of Medicine, Daejeon, Korea
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255
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Cowled C, Baker M, Tachedjian M, Zhou P, Bulach D, Wang LF. Molecular characterisation of Toll-like receptors in the black flying fox Pteropus alecto. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2011; 35:7-18. [PMID: 20692287 PMCID: PMC7103217 DOI: 10.1016/j.dci.2010.07.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Revised: 07/23/2010] [Accepted: 07/23/2010] [Indexed: 05/21/2023]
Abstract
Bats are believed to be reservoir hosts for a number of emerging and re-emerging viruses, many of which are responsible for illness and mortality in humans, livestock and other animals. In other vertebrates, early responses to viral infection involve engagement of Toll-like receptors (TLRs), which induce changes in gene expression collectively leading to an "antiviral state". In this study we report the cloning and bioinformatic analysis of a complete set of TLRs from the black flying fox Pteropus alecto, and perform quantitative tissue expression analysis of the nucleic acid-sensing TLRs 3, 7, 8 and 9. Full-length mRNA transcripts from TLRs homologous to human TLRs 1-10 were sequenced, as well as a nearly intact TLR13 pseudogene that was spliced and polyadenylated. This prototype data can now be used to design functional studies of the bat innate immune system.
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Affiliation(s)
- Christopher Cowled
- CSIRO Livestock Industries, Australian Animal Health Laboratory, 5 Portarlington Rd, East Geelong, Victoria 3220, Australia
| | - Michelle Baker
- CSIRO Livestock Industries, Australian Animal Health Laboratory, 5 Portarlington Rd, East Geelong, Victoria 3220, Australia
- Center for Evolutionary and Theoretical Immunology, Department of Biology, The University of New Mexico, Albuquerque NM 87131, USA
- Corresponding author. Tel.: +61 3 52275052; fax: +61 3 52275555.
| | - Mary Tachedjian
- CSIRO Livestock Industries, Australian Animal Health Laboratory, 5 Portarlington Rd, East Geelong, Victoria 3220, Australia
| | - Peng Zhou
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Dieter Bulach
- CSIRO Livestock Industries, Australian Animal Health Laboratory, 5 Portarlington Rd, East Geelong, Victoria 3220, Australia
| | - Lin-Fa Wang
- CSIRO Livestock Industries, Australian Animal Health Laboratory, 5 Portarlington Rd, East Geelong, Victoria 3220, Australia
- Australian Biosecurity Cooperative Research Centre for Emerging Infectious Diseases, Geelong, Victoria 3220, Australia
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256
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Deshmukh SD, Kremer B, Freudenberg M, Bauer S, Golenbock DT, Henneke P. Macrophages recognize streptococci through bacterial single-stranded RNA. EMBO Rep 2010; 12:71-6. [PMID: 21164516 DOI: 10.1038/embor.2010.189] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Accepted: 10/25/2010] [Indexed: 02/06/2023] Open
Abstract
Group B streptococcus (GBS) is a leading cause of both neonatal sepsis and meningitis, two diseases that are characterized by inflammation. However, the manner in which GBS organisms are recognized by monocytes and macrophages is poorly understood. In this study, we report that the recognition of GBS and other Gram-positive bacteria by macrophages and monocytes relies on bacterial single-stranded RNA (ssRNA). ssRNA interacts with a signalling complex, which comprises the Toll-like receptor adaptors MyD88 and UNC-93B, but not the established MyD88-dependent ssRNA sensors. The role of ssRNA in the recognition of Gram-positive bacteria--leading to the induction of inflammatory cytokines--has potential implications for sepsis pathogenesis, diagnosis and treatment.
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Affiliation(s)
- Sachin D Deshmukh
- Centre of Chronic Immunodeficiency, Medical Centre, University Freiburg, Breisacherstrasse 117, Freiburg 79106, Germany
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257
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Ewald SE, Barton GM. Nucleic acid sensing Toll-like receptors in autoimmunity. Curr Opin Immunol 2010; 23:3-9. [PMID: 21146971 DOI: 10.1016/j.coi.2010.11.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2010] [Revised: 11/15/2010] [Accepted: 11/17/2010] [Indexed: 01/19/2023]
Abstract
Trafficking and activation of the nucleic acid sensing TLRs is subject to unique regulatory requirements imposed by the risk of self-recognition. Like all TLRs these receptors traffick through the Golgi, however, access to the secretory pathway is controlled by a binding partner present in the ER. Receptor activation in the endolysosome is regulated through a proteolytic mechanism that requires activity of compartment-resident proteases, thereby preventing activation in other regions of the cell. Advances in our understanding of the cell biology of these receptors have been paralleled by efforts to understand their precise roles in autoimmunity. Mouse models have revealed that TLR7 and TLR9 make unique contributions to the types of self-molecules recognized in disease and possibly disease severity. Currently, methods of inhibiting TLR7 and TLR9 are being tested in clinical trials for systemic lupus erythamatosus.
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Affiliation(s)
- Sarah E Ewald
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, 405 Life Sciences Addition, Berkeley, CA 94720-3200, USA.
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258
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Shi Z, Cai Z, Sanchez A, Zhang T, Wen S, Wang J, Yang J, Fu S, Zhang D. A novel Toll-like receptor that recognizes vesicular stomatitis virus. J Biol Chem 2010; 286:4517-24. [PMID: 21131352 DOI: 10.1074/jbc.m110.159590] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Toll-like receptors (TLRs) are the key molecular sensors used by the mammalian innate immune system to detect various types of pathogens. Tlr13 is a novel and uncharacterized member of the mammalian TLR family. Here we report the cloning and characterization of tlr13. Tlr13 is predominantly expressed in the spleen, particularly in dendritic cells and macrophages. Tlr13 appears to activate a MyD88- and TAK1-dependent TLR signaling pathway, inducing the activation of NF-κB. This receptor can also activate type 1 interferon through IRF7. Furthermore, Tlr13 seems to be another intracellular TLR. Remarkably, cells expressing tlr13 fail to respond to known TLR ligands but instead respond specifically to vesicular stomatitis virus. Cells with the knockdown of tlr13 are highly susceptible to vesicular stomatitis virus infection. Thus, these results provide an important insight into the potential role of the novel Toll-like receptor tlr13 in the recognition of viral infection.
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Affiliation(s)
- Zhongcheng Shi
- Center for Infectious and Inflammatory Diseases at Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, Texas 77030, USA
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259
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Cavalieri D, Rivero D, Beltrame L, Buschow SI, Calura E, Rizzetto L, Gessani S, Gauzzi MC, Reith W, Baur A, Bonaiuti R, Brandizi M, De Filippo C, D'Oro U, Draghici S, Dunand-Sauthier I, Gatti E, Granucci F, Gündel M, Kramer M, Kuka M, Lanyi A, Melief CJ, van Montfoort N, Ostuni R, Pierre P, Popovici R, Rajnavolgyi E, Schierer S, Schuler G, Soumelis V, Splendiani A, Stefanini I, Torcia MG, Zanoni I, Zollinger R, Figdor CG, Austyn JM. DC-ATLAS: a systems biology resource to dissect receptor specific signal transduction in dendritic cells. Immunome Res 2010; 6:10. [PMID: 21092113 PMCID: PMC3000836 DOI: 10.1186/1745-7580-6-10] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Accepted: 11/19/2010] [Indexed: 12/20/2022] Open
Abstract
Background The advent of Systems Biology has been accompanied by the blooming of pathway databases. Currently pathways are defined generically with respect to the organ or cell type where a reaction takes place. The cell type specificity of the reactions is the foundation of immunological research, and capturing this specificity is of paramount importance when using pathway-based analyses to decipher complex immunological datasets. Here, we present DC-ATLAS, a novel and versatile resource for the interpretation of high-throughput data generated perturbing the signaling network of dendritic cells (DCs). Results Pathways are annotated using a novel data model, the Biological Connection Markup Language (BCML), a SBGN-compliant data format developed to store the large amount of information collected. The application of DC-ATLAS to pathway-based analysis of the transcriptional program of DCs stimulated with agonists of the toll-like receptor family allows an integrated description of the flow of information from the cellular sensors to the functional outcome, capturing the temporal series of activation events by grouping sets of reactions that occur at different time points in well-defined functional modules. Conclusions The initiative significantly improves our understanding of DC biology and regulatory networks. Developing a systems biology approach for immune system holds the promise of translating knowledge on the immune system into more successful immunotherapy strategies.
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Affiliation(s)
- Duccio Cavalieri
- Department of Pharmacology, University of Firenze, Firenze, Italy.
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260
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Pifer R, Benson A, Sturge CR, Yarovinsky F. UNC93B1 is essential for TLR11 activation and IL-12-dependent host resistance to Toxoplasma gondii. J Biol Chem 2010; 286:3307-14. [PMID: 21097503 DOI: 10.1074/jbc.m110.171025] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Toll-like receptor (TLR) activation relies on biochemical recognition of microbial molecules and localization of the TLR within specific cellular compartments. Cell surface TLRs largely recognize bacterial membrane components, and intracellular TLRs are exclusively involved in sensing nucleic acids. Here we show that TLR11, an innate sensor for the Toxoplasma protein profilin, is an intracellular receptor that resides in the endoplasmic reticulum. The 12 membrane-spanning endoplasmic reticulum-resident protein UNC93B1 interacts directly with TLR11 and regulates the activation of dendritic cells in response to Toxoplasma gondii profilin and parasitic infection in vivo. A deficiency in functional UNC93B1 protein abolished TLR11-dependent IL-12 secretion by dendritic cells, attenuated Th1 responses against T. gondii, and dramatically enhanced susceptibility to the parasite. Our results reveal that the association with UNC93B1 and the intracellular localization of TLRs are not unique features of nucleic acid-sensing TLRs but is also essential for TLR11-dependent recognition of T. gondii profilin and for host protection against this parasite.
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Affiliation(s)
- Reed Pifer
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9093, USA
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261
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Huang X, Yang Y. Targeting the TLR9-MyD88 pathway in the regulation of adaptive immune responses. Expert Opin Ther Targets 2010; 14:787-96. [PMID: 20560798 DOI: 10.1517/14728222.2010.501333] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
IMPORTANCE OF THE FIELD Toll-like receptors (TLRs) are innate immune receptors critical in the innate immune defense against invading pathogens. Recent advances also reveal a crucial role for TLRs in shaping adaptive immune responses, conferring a potential therapeutic value to their modulation in the treatment of diseases. AREAS COVERED IN THIS REVIEW The aim of this review is to discuss TLR9, the TLR9-MyD88 signaling pathway and its role in regulation of adaptive immune responses, as well as potential therapeutic implications by targeting this pathway. WHAT THE READER WILL GAIN This review shows that the TLR9-MyD88 signaling pathway plays a critical role in promoting adaptive immune responses and that modulation of this pathway may have enormous therapeutic potential in enhancing vaccine potency, controlling autoimmunity, as well as improving the outcome of viral-vector-mediated gene therapy. TAKE HOME MESSAGE Although TLR9 agonists have been used as adjuvants for enhancing vaccine potency, further exploitation of the TLR9-MyD88 pathway and its dynamic interaction with the immune system in vivo is needed to provide more effective therapeutic inventions in the design of vaccines for infectious diseases, allergies and cancer, in the control of autoimmunity, as well as in the improvement of viral-vector-mediated gene therapy.
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Affiliation(s)
- Xiaopei Huang
- Duke University Medical Center, Department of Medicine, Durham, NC 27710, USA
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262
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Baumann CL, Aspalter IM, Sharif O, Pichlmair A, Blüml S, Grebien F, Bruckner M, Pasierbek P, Aumayr K, Planyavsky M, Bennett KL, Colinge J, Knapp S, Superti-Furga G. CD14 is a coreceptor of Toll-like receptors 7 and 9. ACTA ACUST UNITED AC 2010; 207:2689-701. [PMID: 21078886 PMCID: PMC2989773 DOI: 10.1084/jem.20101111] [Citation(s) in RCA: 172] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
CD14 interacts with and is essential for the functions of endosomal TLR7 and TLR9 in mice. Recognition of pathogens by the innate immune system requires proteins that detect conserved molecular patterns. Nucleic acids are recognized by cytoplasmic sensors as well as by endosomal Toll-like receptors (TLRs). It has become evident that TLRs require additional proteins to be activated by their respective ligands. In this study, we show that CD14 (cluster of differentiation 14) constitutively interacts with the MyD88-dependent TLR7 and TLR9. CD14 was necessary for TLR7- and TLR9-dependent induction of proinflammatory cytokines in vitro and for TLR9-dependent innate immune responses in mice. CD14 associated with TLR9 stimulatory DNA in precipitation experiments and confocal imaging. The absence of CD14 led to reduced nucleic acid uptake in macrophages. Additionally, CD14 played a role in the stimulation of TLRs by viruses. Using various types of vesicular stomatitis virus, we showed that CD14 is dispensable for viral uptake but is required for the triggering of TLR-dependent cytokine responses. These data show that CD14 has a dual role in nucleic acid–mediated TLR activation: it promotes the selective uptake of nucleic acids, and it acts as a coreceptor for endosomal TLR activation.
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Affiliation(s)
- Christoph L Baumann
- Research Center for Molecular Medicine of the Austrian Academy of Sciences, 1090 Vienna, Austria
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263
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Maródi L, Casanova JL. Primary immunodeficiencies may reveal potential infectious diseases associated with immune-targeting mAb treatments. J Allergy Clin Immunol 2010; 126:910-7. [DOI: 10.1016/j.jaci.2010.08.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Revised: 07/16/2010] [Accepted: 08/06/2010] [Indexed: 01/13/2023]
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264
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Bortezomib suppresses function and survival of plasmacytoid dendritic cells by targeting intracellular trafficking of Toll-like receptors and endoplasmic reticulum homeostasis. Blood 2010; 117:500-9. [PMID: 20956804 DOI: 10.1182/blood-2010-05-284737] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Dendritic cells (DCs) play a pivotal role in the pathogenesis of inflammatory disorders, so suppressing the activity of DCs is instrumental in treating such diseases. In the present study, we show that a proteasome inhibitor, bortezomib, suppresses the survival and immunostimulatory function of human plasmacytoid DCs (pDCs) by targeting 2 critical points, intracellular trafficking of nucleic acid-sensingToll-like receptors (TLRs) and endoplasmic reticulum (ER) homeostasis. Among the immune cells in blood, pDCs were the most susceptible to the killing effect of bortezomib. This correlates with a decrease in the spliced form of a transcription factor XBP1, which rescues cells from apoptosis by maintaining ER homeostasis. Bortezomib suppressed the production of interferon-α and interleukin-6 by pDCs activated with a TLR9-stimulating CpG DNA and a TLR7-stimulating influenza virus, which appears to be partially independent of apoptosis. Bortezomib inhibited translocation of TLR9 from the ER to endolysosomes but not of an ER membrane protein, Unc93B1, that delivers TLR9 to endolysosomes. Thus, bortezomib suppresses the activity of pDCs by inhibiting intracellular trafficking of TLRs through disrupting the coordinated translocation of TLRs and Unc93B1 and by disturbing ER homeostasis. This study suggests that proteasome inhibitors may alleviate inflammatory disorders such as lupus and psoriasis that involve pDCs.
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265
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Roberts TL, Turner ML, Dunn JA, Lenert P, Ross IL, Sweet MJ, Stacey KJ. B cells do not take up bacterial DNA: an essential role for antigen in exposure of DNA to toll-like receptor-9. Immunol Cell Biol 2010; 89:517-25. [PMID: 20921967 DOI: 10.1038/icb.2010.112] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Murine dendritic cells (DC) and macrophages respond to bacterial CpG DNA through toll-like receptor 9 (TLR9). Although it is frequently assumed that bacterial DNA is a direct stimulus for B cells, published work does not reliably show responses of purified B cells. Here we show that purified splenic B cells did not respond to Escherichia coli DNA with induction of CD86, despite readily responding to single-stranded (ss) phosphodiester CpG oligodeoxynucleotides (ODN). This was due to a combination of weak responses to both long and double-stranded (ds) DNA. B-cell DNA uptake was greatly reduced with increasing DNA length. This contrasts with macrophages where DNA uptake and subsequent responses were enhanced with increasing DNA length. However, when DNA was physically linked to hen egg lysozyme (HEL), HEL-specific B cells showed efficient uptake of DNA, and limited proliferation in response to the HEL-DNA complex. We propose that, in the absence of other signals, B cells have poor uptake and responses to long dsDNA to prevent polyclonal activation. Conversely, when DNA is physically linked to a B-cell receptor (BCR) ligand, its uptake is increased, allowing TLR9-dependent B-cell activation in an antigen-specific manner. We could not generate fragments of E. coli DNA by limited DNaseI digestion that could mimic the stimulatory effect of ss CpG ODN on naïve B cells. We suggest that the frequently studied polyclonal B-cell responses to CpG ODN are relevant to therapeutic applications of phosphorothioate-modified CpG-containing ODN, but not to natural responses to foreign or host dsDNA.
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Affiliation(s)
- Tara L Roberts
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
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266
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Sasai M, Linehan MM, Iwasaki A. Bifurcation of Toll-like receptor 9 signaling by adaptor protein 3. Science 2010; 329:1530-4. [PMID: 20847273 DOI: 10.1126/science.1187029] [Citation(s) in RCA: 278] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Endosomal Toll-like receptors (TLRs) 7 and 9 recognize viral pathogens and induce signals leading to the activation of nuclear factor κB (NF-κB)-dependent proinflammatory cytokines and interferon regulatory factor 7 (IRF7)-dependent type I interferons (IFNs). Recognition of viral nucleic acids by TLR9 requires its cleavage in the endolysosomal compartment. Here, we show that TLR9 signals leading to the activation of type I IFN, but not proinflammatory cytokine genes, require TLR9 trafficking from endosomes to a specialized lysosome-related organelle. Furthermore, we identify adapter protein-3 as the protein complex responsible for the trafficking of TLR9 to this subcellular compartment. Our results reveal an intracellular mechanism for bifurcation of TLR9 signals by selective receptor trafficking within the endosomal system.
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Affiliation(s)
- Miwa Sasai
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
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267
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Pyzik M, Gendron-Pontbriand EM, Fodil-Cornu N, Vidal SM. Self or nonself? That is the question: sensing of cytomegalovirus infection by innate immune receptors. Mamm Genome 2010; 22:6-18. [PMID: 20882286 DOI: 10.1007/s00335-010-9286-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 09/01/2010] [Indexed: 12/18/2022]
Abstract
Cytomegaloviruses (CMV) are ubiquitous, opportunistic DNA viruses that have mastered the art of immune evasion through their ability to mimic host proteins or to inhibit antiviral responses. The study of the host response against CMV infection has illuminated many facets of the complex interaction between host and pathogen. Here, we review evidence derived from the animal models and human studies that supports the central role played by innate immune receptors in the recognition of virus infection and their participation in the many layers of defense.
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Affiliation(s)
- Michal Pyzik
- Department of Human Genetics and Centre for the Study of Host Resistance, McGill University, Montreal, Quebec, Canada
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268
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Qi R, Hoose S, Schreiter J, Sawant KV, Lamb R, Ranjith-Kumar CT, Mills J, San Mateo L, Jordan JL, Kao CC. Secretion of the human Toll-like receptor 3 ectodomain is affected by single nucleotide polymorphisms and regulated by Unc93b1. J Biol Chem 2010; 285:36635-44. [PMID: 20855885 DOI: 10.1074/jbc.m110.144402] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The innate immune receptor Toll-like receptor 3 (TLR3) can be present on the surface of the plasma membranes of cells and in endolysosomes. The Unc93b1 protein has been reported to facilitate localization of TLR7 and 9 and is required for TLR3, -7, and -9 signaling. We demonstrate that siRNA knockdown of Unc93b1 reduced the abundance of TLR3 on the cell surface without altering total TLR3 accumulation. In addition, siRNA to Unc93b1 reduced the secretion of the TLR3 ectodomain (T3ECD) into the cell medium. Furthermore, two human single nucleotide polymorphisms that affected herpesvirus and influenza virus encephalopathy as well as a natural isoform generated by alternative splicing were found to be impaired for T3ECD secretion and decreased the abundance of TLR3 on the cell surface. The locations of the SNP P554S and the deletion in the isoform led to the identification of a loop in the TLR3 ectodomain that is required for secretion and a second whose presence decreased secretion. Finally, a truncated protein containing the N-terminal 10 leucine-rich repeats of T3ECD was sufficient for secretion in an Unc93b1-dependent manner.
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Affiliation(s)
- Rongsu Qi
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47401-3700, USA
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269
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Abstract
Differential alteration of Toll-like receptor (TLR) expression in inflammatory bowel disease (IBD) was first described 10 years ago. Since then, studies from many groups have led to the current concept that TLRs represent key mediators of innate host defense in the intestine, involved in maintaining mucosal as well as commensal homeostasis. Recent findings in diverse murine models of colitis have helped to reveal the mechanistic importance of TLR dysfunction in IBD pathogenesis. It has become evident that environment, genetics, and host immunity form a multidimensional and highly interactive regulatory triad that controls TLR function in the intestinal mucosa. Imbalanced relationships within this triad may promote aberrant TLR signaling, critically contributing to acute and chronic intestinal inflammatory processes in IBD colitis and associated cancer.
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Affiliation(s)
- Elke Cario
- Division of Gastroenterology & Hepatology, University Hospital of Essen, and Medical School, University of Duisburg-Essen, Essen, Germany.
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270
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Bereczky-Veress B, Abdelmagid N, Piehl F, Bergström T, Olsson T, Sköldenberg B, Diez M. Influence of perineurial cells and Toll-like receptors 2 and 9 on Herpes simplex type 1 entry to the central nervous system in rat encephalitis. PLoS One 2010; 5:e12350. [PMID: 20806060 PMCID: PMC2929186 DOI: 10.1371/journal.pone.0012350] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 07/28/2010] [Indexed: 12/17/2022] Open
Abstract
Herpes simplex encephalitis (HSE) is a rare disease with high mortality and significant morbidity among survivors. We have previously shown that susceptibility to HSE was host-strain dependent, as severe, lethal HSE developed after injection of human Herpes simplex type 1 virus (HSV-1) into the whiskers area of DA rats, whereas PVG rats remained completely asymptomatic. In the present study we investigated the early immunokinetics in these strains to address the underlying molecular mechanisms for the observed difference. The virus distribution and the immunological responses were compared in the whiskers area, trigeminal ganglia and brain stem after 12 hours and the first four days following infection using immunohistochemistry and qRT-PCR. A conspicuous immunopathological finding was a strain-dependent difference in the spread of the HSV-1 virus to the trigeminal ganglia, only seen in DA rats already from 12 hpi. In the whiskers area infected perineurial cells were abundant in the susceptible DA strain after 2 dpi, whereas in the resistant PVG rats HSV-1 spread was confined only to the epineurium. In both strains activation of Iba1(+)/ED1(+) phagocytic cells followed the distribution pattern of HSV-1 staining, which was visible already at 12 hours after infection. Notably, in PVG rats higher mRNA expression of Toll-like receptors (Tlr) -2 and -9, together with increased staining for Iba1/ED1 was detected in the whiskers area. In contrast, all other Tlr-pathway markers were expressed at higher levels in the susceptible DA rats. Our data demonstrate the novel observation that genetically encoded properties of the host nerve and perineurial cells, recruitment of phagocyting cells together with the low expression of Tlr2 and -9 in the periphery define the susceptibility to HSV-1 entry into the nervous system.
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Affiliation(s)
- Biborka Bereczky-Veress
- Department of Medicine Solna, Unit of Infectious Diseases, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Nada Abdelmagid
- Department of Clinical Neuroscience, Neuroimmunology Unit, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Fredrik Piehl
- Department of Clinical Neuroscience, Neuroimmunology Unit, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Tomas Bergström
- Department of Clinical Virology, University of Gothenburg, Göteborg, Sweden
| | - Tomas Olsson
- Department of Clinical Neuroscience, Neuroimmunology Unit, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Birgit Sköldenberg
- Department of Medicine Solna, Unit of Infectious Diseases, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
| | - Margarita Diez
- Department of Clinical Neuroscience, Neuroimmunology Unit, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden
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271
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Melo MB, Kasperkovitz P, Cerny A, Könen-Waisman S, Kurt-Jones EA, Lien E, Beutler B, Howard JC, Golenbock DT, Gazzinelli RT. UNC93B1 mediates host resistance to infection with Toxoplasma gondii. PLoS Pathog 2010; 6:e1001071. [PMID: 20865117 PMCID: PMC2928809 DOI: 10.1371/journal.ppat.1001071] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Accepted: 07/26/2010] [Indexed: 01/08/2023] Open
Abstract
UNC93B1 associates with Toll-Like Receptor (TLR) 3, TLR7 and TLR9, mediating their translocation from the endoplasmic reticulum to the endolysosome, hence allowing proper activation by nucleic acid ligands. We found that the triple deficient ‘3d’ mice, which lack functional UNC93B1, are hyper-susceptible to infection with Toxoplasma gondii. We established that while mounting a normal systemic pro-inflammatory response, i.e. producing abundant MCP-1, IL-6, TNFα and IFNγ, the 3d mice were unable to control parasite replication. Nevertheless, infection of reciprocal bone marrow chimeras between wild-type and 3d mice with T. gondii demonstrated a primary role of hemopoietic cell lineages in the enhanced susceptibility of UNC93B1 mutant mice. The protective role mediated by UNC93B1 to T. gondii infection was associated with impaired IL-12 responses and delayed IFNγ by spleen cells. Notably, in macrophages infected with T. gondii, UNC93B1 accumulates on the parasitophorous vacuole. Furthermore, upon in vitro infection the rate of tachyzoite replication was enhanced in non-activated macrophages carrying mutant UNC93B1 as compared to wild type gene. Strikingly, the role of UNC93B1 on intracellular parasite growth appears to be independent of TLR function. Altogether, our results reveal a critical role for UNC93B1 on induction of IL-12/IFNγ production as well as autonomous control of Toxoplasma replication by macrophages. One third of the human population in the world is chronically infected with Toxoplasma gondii. While the majority of infected individuals are asymptomatic, toxoplasmosis is a major cause of congenital disease, abortion, and a life-threatening opportunistic disease in immunocompromised individuals. Early activation of the innate immune system and cytokine production by myeloid cells is required for establishment of protective immunity to T. gondii infection. In mice, a mutation in the UNC93B1 gene abolishes signaling via the intracellular innate immune receptors, namely Toll-like receptors (TLR) 3, 7 and 9, thus, named triple-deficiency (3d) mice. Our results demonstrate that the hyper-susceptibility of 3d mice to T. gondii infection is associated with impaired IL-12 production, delayed IFNγ production, and uncontrolled parasite replication in macrophages. Overall, our study reveals a critical role for UNC93B1 in the immunological control of T. gondii infection.
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Affiliation(s)
- Mariane B. Melo
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Pia Kasperkovitz
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Anna Cerny
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | | | - Evelyn A. Kurt-Jones
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Egil Lien
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Bruce Beutler
- The Scripps Research Institute, La Jolla, California, United States of America
| | | | - Douglas T. Golenbock
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Centro de Pesquisas Réne Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil
| | - Ricardo T. Gazzinelli
- University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Centro de Pesquisas Réne Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil
- Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
- * E-mail:
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272
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Chang ZL. Important aspects of Toll-like receptors, ligands and their signaling pathways. Inflamm Res 2010; 59:791-808. [PMID: 20593217 DOI: 10.1007/s00011-010-0208-2] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 04/06/2010] [Accepted: 04/22/2010] [Indexed: 12/17/2022] Open
Abstract
Due to the rapid increase of new information on the multiple roles of Toll-like receptors (TLRs), this paper reviews several main properties of TLRs and their ligands and signaling pathways. The investigation of pathogen infections in knockout mice suggests that specific TLRs play a key role in the activation of immune responses. Although the investigation of TLR biology is just beginning, a number of important findings are emerging. This review focuses on the following seven aspects of this emerging field: (a) a history of TLR and ligand studies; (b) the molecular basis of recognition by TLRs: TLR structures, pathogen-associated molecular pattern binding sites, TLR locations and functional responses; (c) cell types in TLR expression; (d) an overview of TLRs and their ligands: expression and ligands of cell-surface TLRs and of intracellular TLRs; (e) TLR-signaling pathways; (f) discussion: TLRs control of innate and adaptive systems; the trafficking of intracellular TLRs to endolysosomes; investigation of TLRs in regulating microRNA; investigation of crystal structure of TLRs with ligand binding; incidence of infectious diseases associated with single nucleotide polymorphisms (SNPs) in TLR genes; risk of cancer related to SNPs in TLR genes; TLR-ligand mediated anti-cancer effects; and TLR-ligand induced chronic inflammation and tumorigenesis; and (g) conclusions.
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Affiliation(s)
- Z L Chang
- Institute of Biochemistry and Cell Biology, Shanghai Institute for Biological Science, Chinese Academy of Sciences, Shanghai 200031, China.
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273
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Mikula I, Bhide M, Pastorekova S, Mikula I. Characterization of ovine TLR7 and TLR8 protein coding regions, detection of mutations and Maedi Visna virus infection. Vet Immunol Immunopathol 2010; 138:51-9. [PMID: 20638136 DOI: 10.1016/j.vetimm.2010.06.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 06/15/2010] [Accepted: 06/21/2010] [Indexed: 11/30/2022]
Abstract
Toll-like receptors (TLRs) 2, 3, 4, 7, 8 and 9 play a crucial role in the recognition of viral entities and modulation of the innate immune system. This work presents sequence analysis of ovine TLR7 and TLR8 genes, depicts novel mutations and describes frequencies of mutations in Maedi Visna infected and healthy sheep. Totally 48 samples of the breed Tsigai were analyzed for the presence of mutations. Within 20 mutations, 14 were silent whereas 6 were missense. The frequencies of missense mutations in the Maedi Visna infected compared to non-infected sheep were: Lys115Glu (P-0.766, F-test), Asn117 (P-0.380) and Lys818Arg (P-0.739). These three mutations were localized in extra LRR (lucine rich repeat) region of TLR7, while mutation Ile73Leu (P-0.498) was located within LRR2 motif. Both mutations in TLR8, Asn165Lys (P-1.0) and Tyr349His (P-0.700), were present in extra LRR region. The secondary structure analysis of ovine TLR7 and TLR8 revealed conserved LRR motif structure, however with some irregularities compared to cattle and human. Transmembrane domains of TLR7 and TLR8 showed 100% homology between sheep and cattle wherein no mutations were found. In both TLRs TIR domains were highly conserved with occurrence of 4 silent mutations. Mutations in TLR7 and TLR8 may play an important role as predisposition factor for Maedi Visna infection. Considering the sequence homology among sheep, cattle and human genes encoding TLR7 and TLR8, we predict their similar function, localization and downstream signaling.
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Affiliation(s)
- Ivan Mikula
- Laboratory of Biomedical Microbiology and Immunology, University of Veterinary Medicine and Pharmacy, Komenskeho-73, Kosice, Slovakia
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274
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Bagashev A, Fitzgerald MC, Larosa DF, Rose PP, Cherry S, Johnson AC, Sullivan KE. Leucine-rich repeat (in Flightless I) interacting protein-1 regulates a rapid type I interferon response. J Interferon Cytokine Res 2010; 30:843-52. [PMID: 20586614 DOI: 10.1089/jir.2010.0017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The cell autonomous response to viral infection is carefully regulated to induce type I interferons (IFNs), which in turn induce the establishment of an antiviral state. Leucine-rich repeat (in Flightless I) interacting protein-1 (LRRFIP1) and LRRFIP2 are 2 related proteins that have been identified as interacting with MyD88 and Flightless I homolog, a leucine-rich repeat protein. LRRFIP2 positively regulates NFκB and macrophage cytokine production after lipopolysaccharide, but less is known about LRRFIP1. We hypothesized that LRRFIP1 could be more important in antiviral responses, as overexpression led to type I IFN production in a pilot study. The induction of type I IFNs occurred even in the absence of virus, but was enhanced by the presence of virus. Conversely, knockdown of LRRFIP1 compromised IFN expression. We found that LRRFIP1 was rapidly recruited to influenza-containing early endosomes in a p38-dependent fashion. This was specific for virus-containing endosomes as there was almost no colocalization of LRRFIP1 with early endosomes in the absence of virus. Further, LRRFIP1 was recruited to RNA-containing vesicles. Taken together, these data suggest that LRRFIP1 participates in cell responses to virus at early time points and is important for type I IFN induction.
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Affiliation(s)
- Asen Bagashev
- The Division of Allergy Immunology, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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275
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Baronti C, Sire J, de Lamballerie X, Quérat G. Nonstructural NS1 proteins of several mosquito-borne Flavivirus do not inhibit TLR3 signaling. Virology 2010; 404:319-30. [PMID: 20554300 DOI: 10.1016/j.virol.2010.05.020] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Revised: 02/11/2010] [Accepted: 05/17/2010] [Indexed: 01/21/2023]
Abstract
Flaviviruses are single-stranded positive RNA viruses that replicate through double stranded RNA (dsRNA) intermediates. These dsRNA may be recognized as pathogen-associated molecular patterns by cellular receptors including membrane-bound Toll-like receptor 3 (TLR3) and cytosolic helicases RIG-I and MDA5. dsRNA stimulation results in signaling cascades converging to activation of interferon (IFN) regulatory factor 3 (IRF3) and to transcriptional activation of several interferon stimulated genes, including IFNss and inflammatory cytokines. There are conflicting reports concerning the ability of West Nile virus to counteract TLR3 signaling. In our analyses, transiently or stably expressed NS1 proteins from two West Nile viruses, two dengue 2 viruses and a yellow fever virus failed to inhibit TLR3 signaling in two different mammalian cell lines. Moreover, using siRNA inhibiting the helicase signalization pathway, we show that viral infection did not impede TLR3 responses to poly(I:C). We conclude that NS1 proteins from distinct mosquito-borne flaviviruses do not inhibit TLR3 signaling.
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Affiliation(s)
- Cécile Baronti
- UMR IRD 190, Emergence des Pathologies Virales, Université de la Méditerranée, Faculté de Médecine de la Timone, 27 Bd Jean Moulin, 13005 Marseille, France
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276
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Santiago-Raber ML, Dunand-Sauthier I, Wu T, Li QZ, Uematsu S, Akira S, Reith W, Mohan C, Kotzin BL, Izui S. Critical role of TLR7 in the acceleration of systemic lupus erythematosus in TLR9-deficient mice. J Autoimmun 2010; 34:339-48. [DOI: 10.1016/j.jaut.2009.11.001] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 11/03/2009] [Accepted: 11/04/2009] [Indexed: 10/20/2022]
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277
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Keestra AM, de Zoete MR, Bouwman LI, van Putten JPM. Chicken TLR21 is an innate CpG DNA receptor distinct from mammalian TLR9. THE JOURNAL OF IMMUNOLOGY 2010; 185:460-7. [PMID: 20498358 DOI: 10.4049/jimmunol.0901921] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
TLRs comprise a family of evolutionary conserved sensory receptors that respond to distinct classes of ligands. For one major evolutionary branch of TLRs, the ligands are still largely unknown. Here we report the cloning and function of one member of this group, chicken TLR21 (chTLR21). This TLR is absent in the human species but has homologs in fish and frog and displays similarity with mouse TLR13. Expression of chTLR21 in HEK293 cells resulted in activation of NF-kappaB in response to unmethylated CpG DNA, typically recognized by mammalian TLR9. Silencing of chTLR21 (but not chTLR4) in chicken macrophages inhibited the response to CpG-DNA (but not to LPS), indicating similar functionality of the endogenous receptor. ChTLR21 responded to human- and murine-specific TLR9 ligands, as well as to bacterial genomic DNA isolated from Salmonella enterica serovar Enteritidis. Confocal microscopy located chTLR21 in the same intracellular compartments as human TLR9. Inhibition of the chTLR21 response by the endosomal maturation inhibitor chloroquine suggested that the receptor is functional in endolysosomes, as known for TLR9. The analogous localization and function of the phylogenetically only distantly related chTLR21 and mammalian TLR9 suggest that during evolution different classes of TLRs have emerged that recognize the same type of ligands.
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Affiliation(s)
- A Marijke Keestra
- Department of Infectious Diseases and Immunology, Utrecht University, Utrecht, The Netherlands
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278
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Abstract
Synaptic vesicles are specialized cycling endosomes that contain a unique constellation of membrane proteins. Proteins are sorted to vesicles by short amino acid sequences that serve as binding sites for clathrin adaptor proteins. Here we show that a tyrosine-based endocytosis motif in the vesicle protein SV2 is required for trafficking to synaptic vesicles of both SV2 and the calcium sensor protein synaptotagmin. Aberrant neurotransmission in cultured hippocampal neurons lacking SV2 was rescued by expression of wild-type SV2A, but not by SV2A-Y46A, a mutant containing a disrupted endocytosis motif in SV2A's cytoplasmic N terminus. Neurons expressing SV2A-Y46A had significantly more SV2 on the plasma membrane, indicating reduced internalization. A screen for proteins that preferentially bound wild-type SV2A identified multiple endocytosis-related proteins, and in vitro binding studies confirmed binding to the clathrin adaptors AP2, EPS15, and amphiphysin 2/Bin1. Neurons lacking SV2 contained less synaptotagmin and had a higher proportion of synaptotagmin on the plasma membrane. Expression of either wild-type SV2A or SV2A-Y46A restored synaptotagmin expression levels; however, only wild-type SV2A restored a normal proportion of synaptotagmin on the plasma membrane. These findings indicate that SV2 influences the expression and trafficking of synaptotagmin via separate mechanisms. Synaptic vesicles immunoisolated from SV2A/B double knock-out mice had significantly less synaptotagmin than vesicles isolated from wild-type mice. Our results indicate that SV2 plays a major role in regulating the amount of synaptotagmin in synaptic vesicles and provide an explanation for the observation that synapses lacking SV2 have fewer vesicles competent for calcium-induced fusion.
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279
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Loewendorf A, Benedict CA. Modulation of host innate and adaptive immune defenses by cytomegalovirus: timing is everything. J Intern Med 2010; 267:483-501. [PMID: 20433576 PMCID: PMC2902254 DOI: 10.1111/j.1365-2796.2010.02220.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Human cytomegalovirus (HCMV) (HHV-5, a beta-herpesvirus) causes the vast majority of infection-related congenital birth defects, and can trigger severe disease in immune suppressed individuals. The high prevalence of societal infection, the establishment of lifelong persistence and the growing number of immune-related diseases where HCMV is touted as a potential promoter is slowly heightening public awareness to this virus. The millions of years of co-evolution between CMV and the immune system of its host provides for a unique opportunity to study immune defense strategies, and pathogen counterstrategies. Dissecting the timing of the cellular and molecular processes that regulate innate and adaptive immunity to this persistent virus has revealed a complex defense network that is shaped by CMV immune modulation, resulting in a finely tuned host-pathogen relationship.
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Affiliation(s)
- A Loewendorf
- Division of Molecular Immunology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA
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280
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Abstract
Viruses that infect the nervous system may cause acute, chronic or latent infections. Despite the so-called immunoprivileged status of the nervous system, immunosurveillance plays an important role in the fate of viral infection of the brain. Herpes simplex virus 1 (HSV-1) persists in the nervous system for the life of the host with periodic stress induced reactivation that produces progeny viruses. Prevention of reactivation requires a complex interplay between virus neurons, and immune response. New evidence supports the view that CD8+T cells employing both lytic granule- and IFN-gamma-dependent effectors are essential in setting up and maintaining HSV-1 latency. HSV-1 infection of the nervous system can be seen as a parasitic invasion which leaves the individual at risk for subsequent reactivation and disease. The recent observation that herpes virus latency may confer protection against experimental bacterial infection suggests that unexpected symbiosis may exist between latent viruses and the infected nervous system of its host.
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Affiliation(s)
- M Lafon
- URA CNRS 3015, unité de neuro-immunologie virale, Institut Pasteur, 25, rue du Dr-Roux, 75724 Paris cedex 15, France.
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281
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Abstract
Foreign nucleic acids, the signature of invading viruses and certain bacteria, are sensed intracellularly. The nucleic acid-specific Toll-like receptors (TLRs) detect and signal within endolysosomal compartments, triggering the induction of cytokines essential for the innate immune response. These cytokines include proinflammatory molecules produced mainly by macrophages and conventional dendritic cells, as well as type I interferons, which are produced in great quantities by plasmacytoid dendritic cells. The cellular and molecular pathways by which nucleic acids and TLRs meet within the endosome assure host protection yet also place the host at risk for the development of autoimmunity. Here, we review the latest findings on the intracellular TLRs, with special emphasis on ligand uptake, receptor trafficking, signaling, and regulation.
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282
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Kawai T, Akira S. The role of pattern-recognition receptors in innate immunity: update on Toll-like receptors. Nat Immunol 2010. [DOI: 78495111110.1038/ni.1863' target='_blank'>'"<>78495111110.1038/ni.1863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [78495111110.1038/ni.1863','', '10.1083/jcb.200612056')">Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2022]
78495111110.1038/ni.1863" />
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283
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Kawai T, Akira S. The role of pattern-recognition receptors in innate immunity: update on Toll-like receptors. Nat Immunol 2010; 11:373-84. [PMID: 20404851 DOI: 10.1038/ni.1863] [Citation(s) in RCA: 6295] [Impact Index Per Article: 449.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The discovery of Toll-like receptors (TLRs) as components that recognize conserved structures in pathogens has greatly advanced understanding of how the body senses pathogen invasion, triggers innate immune responses and primes antigen-specific adaptive immunity. Although TLRs are critical for host defense, it has become apparent that loss of negative regulation of TLR signaling, as well as recognition of self molecules by TLRs, are strongly associated with the pathogenesis of inflammatory and autoimmune diseases. Furthermore, it is now clear that the interaction between TLRs and recently identified cytosolic innate immune sensors is crucial for mounting effective immune responses. Here we describe the recent advances that have been made by research into the role of TLR biology in host defense and disease.
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Affiliation(s)
- Taro Kawai
- Laboratory of Host Defense, World Premier International Immunology Frontier Research Center, Osaka University, Osaka, Japan
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284
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Suhir H, Etzioni A. The role of Toll-like receptor signaling in human immunodeficiencies. Clin Rev Allergy Immunol 2010; 38:11-9. [PMID: 19430930 DOI: 10.1007/s12016-009-8135-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Through the last decade, clinical immunology has witnessed a considerable progress in understanding the role of the innate immunity in human host defense, with Toll-like receptors (TLRs) being the most extensively innate immune receptors investigated. Growing literature documents the relevance of TLR signaling pathways to human disease, revealing a small, but expanding, group of new monogenic primary immunodeficiencies, in patients with various infectious diseases, previously considered as of unexplained "idiopathic" origin. Herein, we review these recently described deficiencies. Autosomal recessive IRAK-4 and myeloid differentiation factor 88 deficiencies were reported in 2003 and 2008, respectively, conferring predisposition to pyogenic bacterial infections, and autosomal recessive UNC93B1 and autosomal dominant TLR3 deficiencies were reported in 2006 and 2007, respectively, conferring predisposition to herpes simplex encephalitis. Furthermore, we highlight the published data associating TLR polymorphism with an altered susceptibility to infectious diseases.
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Affiliation(s)
- Hanna Suhir
- Meyer's Children Hospital, The Rappaport School of Medicine, Technion, Haifa, Israel
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285
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Tang F, Du Q, Liu YJ. Plasmacytoid dendritic cells in antiviral immunity and autoimmunity. SCIENCE CHINA-LIFE SCIENCES 2010; 53:172-82. [PMID: 20596824 DOI: 10.1007/s11427-010-0045-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2009] [Accepted: 01/15/2010] [Indexed: 10/19/2022]
Abstract
Plasmacytoid dendritic cells (pDCs) represent a unique and crucial immune cell population capable of producing large amounts of type I interferons (IFNs) in response to viral infection. The function of pDCs as the professional type I IFN-producing cells is linked to their selective expression of Toll-like receptor 7 (TLR7) and TLR9, which sense viral nucleic acids within the endosomal compartments. Type I IFNs produced by pDCs not only directly inhibit viral replication but also play an essential role in linking the innate and adaptive immune system. The aberrant activation of pDCs by self nucleic acids through TLR signaling and the ongoing production of type I IFNs do occur in some autoimmune diseases. Therefore, pDC may serve as an attractive target for therapeutic manipulations of the immune system to treat viral infectious diseases and autoimmune diseases.
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Affiliation(s)
- Fei Tang
- Center for Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
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286
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Cao W, Bover L. Signaling and ligand interaction of ILT7: receptor-mediated regulatory mechanisms for plasmacytoid dendritic cells. Immunol Rev 2010; 234:163-76. [PMID: 20193018 PMCID: PMC2919054 DOI: 10.1111/j.0105-2896.2009.00867.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Plasmacytoid dendritic cells (pDCs) are specialized dendritic cells (DCs) that produce large amounts of type I interferon (IFN) after Toll-like receptor (TLR) activation. Human pDCs preferentially express immunoglobulin-like transcript 7 (ILT7; LILRA4), which couples with a signaling adapter to activate a prominent immunoreceptor tyrosine-based activation motif (ITAM)-mediated signaling pathway. ILT7 protein directly binds to and can be activated by bone marrow stromal cell antigen 2 (BST2; CD317) protein, the expression of which is found on cells pre-exposed to IFN or on the surface of human cancer cells. The interaction between ILT7 and BST2 functions to assure an appropriate TLR response by pDCs during viral infection and likely participates in pDC-tumor crosstalk. Two opposing modes of receptor-mediated regulatory mechanisms work jointly to fine tune the innate immunity of pDCs.
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Affiliation(s)
- Wei Cao
- Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA.
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287
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Nakano S, Morimoto S, Suzuki S, Watanabe T, Amano H, Takasaki Y. Up-regulation of the endoplasmic reticulum transmembrane protein UNC93B in the B cells of patients with active systemic lupus erythematosus. Rheumatology (Oxford) 2010; 49:876-81. [PMID: 20159909 DOI: 10.1093/rheumatology/keq001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES The transmembrane endoplasmic reticulum (ER) protein UNC93B plays an essential role in the normal response to signalling through intracellular Toll-like receptor (TLR)3, TLR7, TLR8 and TLR9. In the current study, we examined the level of UNC93B expression on peripheral B cells from patients with active SLE, and investigated any correlation with SLE pathogenesis. METHODS Peripheral blood mononuclear cells (PBMCs) and B cells from 43 active SLE patients were analysed by quantitative RT-PCR to determine the precise levels of UNC93B mRNA. We also analysed UNC93B protein expression on B cells from SLE patients using immunoblotting. RESULTS The expression of UNC93B mRNA on PBMCs from active SLE patients was significantly higher than that of controls (P < 0.05). The intracellular expression level of UNC93B protein on CD20(+) B cells from active SLE patients was also higher than in the controls. Moreover, the expression of UNC93B on B cells from lupus patients correlated significantly with high titres of anti-dsDNA antibody (P < 0.05). CONCLUSIONS Up-regulation of the ER membrane protein UNC93B on human lupus B cells suggests that TLR9 and UNC93B play a partial role in the pathogenesis of SLE by inducing defective peripheral B-cell tolerance.
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Affiliation(s)
- Souichiro Nakano
- Department of Internal Medicine and Rheumatology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421 Japan.
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288
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McGettrick AF, O'Neill LAJ. Localisation and trafficking of Toll-like receptors: an important mode of regulation. Curr Opin Immunol 2010; 22:20-7. [PMID: 20060278 DOI: 10.1016/j.coi.2009.12.002] [Citation(s) in RCA: 239] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Accepted: 12/13/2009] [Indexed: 01/22/2023]
Abstract
In recent years the importance of the localisation and trafficking of Toll-like receptors (TLRs) and their adaptors within the cell has become apparent. Localisation and trafficking of both cell surface and endosomal TLRs, alongside their adaptors, appears to play an important role not only in ligand recognition but also in the downregulation of signaling following ligand stimulation. Chaperones, such as gp96, PRAT4A and Unc93B1 play a role in TLR localisation. TLR4 cycles between the Golgi and the plasma membrane until engaged by LPS. The MyD88-dependent pathway is then initiated at the plasma membrane, followed by the movement of the TLR4 complex into the endosome where the MyD88-independent pathway is activated. Several proteins, including Triad3A and TAG appear to be involved in the movement of TLR4 to the lysosome for degradation.
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Affiliation(s)
- Anne F McGettrick
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
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289
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Bird PI, Trapani JA, Villadangos JA. Endolysosomal proteases and their inhibitors in immunity. Nat Rev Immunol 2009; 9:871-82. [PMID: 19935806 DOI: 10.1038/nri2671] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The cellular endolysosomal compartment is dynamic, complex and incompletely understood. Its organelles and constituents vary between different cell types, but endolysosomal proteases are key components of this compartment in all cells. In immune cells, these proteases function in pathogen recognition and elimination, signal processing and cell homeostasis, and they are regulated by dedicated inhibitors. Pathogens can produce analogous proteases to subvert the host immune response. The balance in activity between a protease and its inhibitor can tune the immune response or cause damage as a result of mislocalized proteolysis. In this Review, we highlight recent developments in this area and emphasize the importance of studying the role of endolysosomal proteases, and their natural inhibitors, in the initiation and regulation of immune responses.
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Affiliation(s)
- Phillip I Bird
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
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290
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Abstract
Toll-like receptors (TLRs) are a family of innate immune system receptors responsible for recognizing conserved pathogen-associated molecular patterns (PAMPs). PAMP binding to TLRs initiates intracellular signaling pathways that lead to the upregulation of a variety of costimulatory molecules and the synthesis and secretion of various cytokines and interferons by cells of the innate immune system. TLR-induced innate immune responses are a prerequisite for the generation of most adaptive immune responses, and in the case of B cells, TLRs directly regulate signaling from the antigen-specific B-cell receptor. The outcome of TLR signaling is determined, in part, by the cells in which they are expressed and by the selective use of signaling adaptors. Recent studies suggest that, in addition, both the ligand recognition by TLRs and the functional outcome of ligand binding are governed by the subcellular location of the TLRs and their signaling adaptors. In this review we describe what is known about the intracellular trafficking and compartmentalization of TLRs in innate system's dendritic cells and macrophages and in adaptive system's B cells, highlighting how location regulates TLR function.
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Affiliation(s)
- Akanksha Chaturvedi
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
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291
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Ma L, Horvitz HR. Mutations in the Caenorhabditis elegans U2AF large subunit UAF-1 alter the choice of a 3' splice site in vivo. PLoS Genet 2009; 5:e1000708. [PMID: 19893607 PMCID: PMC2762039 DOI: 10.1371/journal.pgen.1000708] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Accepted: 10/05/2009] [Indexed: 11/18/2022] Open
Abstract
The removal of introns from eukaryotic RNA transcripts requires the activities of five multi-component ribonucleoprotein complexes and numerous associated proteins. The lack of mutations affecting splicing factors essential for animal survival has limited the study of the in vivo regulation of splicing. From a screen for suppressors of the Caenorhabditis elegans unc-93(e1500) rubberband Unc phenotype, we identified mutations in genes that encode the C. elegans orthologs of two splicing factors, the U2AF large subunit (UAF-1) and SF1/BBP (SFA-1). The uaf-1(n4588) mutation resulted in temperature-sensitive lethality and caused the unc-93 RNA transcript to be spliced using a cryptic 3′ splice site generated by the unc-93(e1500) missense mutation. The sfa-1(n4562) mutation did not cause the utilization of this cryptic 3′ splice site. We isolated four uaf-1(n4588) intragenic suppressors that restored the viability of uaf-1 mutants at 25°C. These suppressors differentially affected the recognition of the cryptic 3′ splice site and implicated a small region of UAF-1 between the U2AF small subunit-interaction domain and the first RNA recognition motif in affecting the choice of 3′ splice site. We constructed a reporter for unc-93 splicing and using site-directed mutagenesis found that the position of the cryptic splice site affects its recognition. We also identified nucleotides of the endogenous 3′ splice site important for recognition by wild-type UAF-1. Our genetic and molecular analyses suggested that the phenotypic suppression of the unc-93(e1500) Unc phenotype by uaf-1(n4588) and sfa-1(n4562) was likely caused by altered splicing of an unknown gene. Our observations provide in vivo evidence that UAF-1 can act in regulating 3′ splice-site choice and establish a system that can be used to investigate the in vivo regulation of RNA splicing in C. elegans. Eukaryotic genes contain intervening intronic sequences that must be removed from pre-mRNA transcripts by RNA splicing to generate functional messenger RNAs. While studying genes that encode and control a presumptive muscle potassium channel complex in the nematode Caenorhabditis elegans, we found that mutations in two splicing factors, the U2AF large subunit and SF1/BBP suppress the rubberband Unc phenotype caused by a rare missense mutation in the gene unc-93. Mutations affecting the U2AF large subunit caused the recognition of a cryptic 3′ splice site generated by the unc-93 mutation, providing in vivo evidence that the U2AF large subunit can affect splice-site selection. By contrast, an SF1/BBP mutation that suppressed the rubberband Unc phenotype did not cause splicing using this cryptic 3′ splice site. Our genetic studies identified a region of the U2AF large subunit important for its effect on 3′ splice-site choice. Our mutagenesis analysis of in vivo transgene splicing identified a positional effect on weak 3′ splice site selection and nucleotides of the endogenous 3′ splice site important for recognition. The system we have defined should facilitate future in vivo analyses of pre–mRNA splicing.
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Affiliation(s)
- Long Ma
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - H. Robert Horvitz
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail:
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292
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Sepulveda FE, Maschalidi S, Colisson R, Heslop L, Ghirelli C, Sakka E, Lennon-Duménil AM, Amigorena S, Cabanie L, Manoury B. Critical role for asparagine endopeptidase in endocytic Toll-like receptor signaling in dendritic cells. Immunity 2009; 31:737-48. [PMID: 19879164 DOI: 10.1016/j.immuni.2009.09.013] [Citation(s) in RCA: 228] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Revised: 06/26/2009] [Accepted: 09/11/2009] [Indexed: 11/25/2022]
Abstract
Intracellular Toll-like receptor 3 (TLR3), TLR7, and TLR9 localize in endosomes and recognize single-stranded RNA and nucleotides from viruses and bacteria. This interaction induces their conformational changes resulting in the production of proinflammatory cytokines and upregulation of cell surface molecules. TLR9 requires a proteolytic cleavage for its signaling. Here, we report that myeloid and plasmacytoid dendritic cells (DCs) deficient for the asparagine endopeptidase (AEP), a cysteine lysosomal protease, showed a decrease in the secretion of proinflammatory cytokines in response to TLR9 stimulation in vitro and in vivo. Upon stimulation, full-length TLR9 was cleaved into a 72 kDa fragment and this processing was strongly reduced in DCs lacking AEP. Processed TLR9 coeluted with the adaptor molecule MyD88 and AEP after size exclusion chromatography. When expressed in AEP-deficient DCs, the 72 kDa proteolytic fragment restored TLR9 signaling. Thus, our results identify an endocytic protease playing a critical role in TLR processing and signaling in DCs.
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293
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Identification of Mouse Cytomegalovirus Resistance Loci by ENU Mutagenesis. Viruses 2009; 1:460-83. [PMID: 21994556 PMCID: PMC3185521 DOI: 10.3390/v1030460] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 10/19/2009] [Accepted: 10/20/2009] [Indexed: 12/14/2022] Open
Abstract
Host resistance to infection depends on the efficiency with which innate immune responses keep the infectious agent in check. Innate immunity encompasses components with sensing, signaling and effector properties. These elements with non-redundant functions are encoded by a set of host genes, the resistome. Here, we review our findings concerning the resistome. We have screened randomly mutagenized mice for susceptibility to a natural opportunistic pathogen, the mouse cytomegalovirus. We found that some genes with initially no obvious functions in innate immunity may be critical for host survival to infections, falling into a newly defined category of genes of the resistome.
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294
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Kumar H, Kawai T, Akira S. Toll-like receptors and innate immunity. Biochem Biophys Res Commun 2009; 388:621-5. [PMID: 19686699 DOI: 10.1016/j.bbrc.2009.08.062] [Citation(s) in RCA: 816] [Impact Index Per Article: 54.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Accepted: 08/14/2009] [Indexed: 12/13/2022]
Abstract
Toll-like receptors (TLRs) are evolutionarily conserved innate receptors expressed in various immune and non-immune cells of the mammalian host. TLRs play a crucial role in defending against pathogenic microbial infection through the induction of inflammatory cytokines and type I interferons. Furthermore, TLRs also play roles in shaping pathogen-specific humoral and cellular adaptive immune responses. In this review, we describe the recent advances in pathogen recognition by TLRs and TLR signaling.
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Affiliation(s)
- Himanshu Kumar
- Laboratory of Host Defense, WPI Immunology Frontier Research Center, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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295
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Vilaysane A, Muruve DA. The innate immune response to DNA. Semin Immunol 2009; 21:208-14. [DOI: 10.1016/j.smim.2009.05.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Accepted: 05/06/2009] [Indexed: 12/25/2022]
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296
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Beutler B. Microbe sensing, positive feedback loops, and the pathogenesis of inflammatory diseases. Immunol Rev 2009; 227:248-63. [PMID: 19120489 DOI: 10.1111/j.1600-065x.2008.00733.x] [Citation(s) in RCA: 182] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The molecular apparatus that protects us against infection can also injure us by causing autoimmune or autoinflammatory disease. It now seems that at times, defects within the sensing arm of innate immunity contribute to diseases of this type. The initiation of an immune response is often microbe dependent and, in many cases, Toll-like receptor (TLR) dependent. Positive feedback loops triggering immune activation may occur when TLR signaling pathways stimulate host cells in an unchecked manner. Or, immune activation may persist because of failure to eradicate an inciting infection. Or on occasion, endogenous DNA may trigger specific immune responses that beget further responses in a TLR-dependent autoamplification loop. Specific biochemical defects that cause loop-related autoimmunity have been revealed by random germline mutagenesis and by gene targeting. We have also developed some insight into critical points at which feedback loops can be interrupted.
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Affiliation(s)
- Bruce Beutler
- Department of Genetics, The Scripps Research Institute, La Jolla, CA 92037, USA.
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297
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Abstract
Recombinant viral vectors such as adenovirus and adenovirus-associated virus have been used widely as vehicles for gene therapy applications because of the high efficiency with which they transfer genes into a wide spectrum of cells in vivo. However, enthusiasm for the use of viral vectors in gene therapy has been tempered by significant problems of attendant host cellular and humoral immune responses that limit their safety and efficacy in vivo. Advances in immunology have suggested a crucial role for the innate immune system in the induction of immune responses to viruses. Thus, a better understanding of the mechanisms by which the host's innate immune system recognizes viruses and viral vectors will help in the design of effective strategies to improve the outcome of viral vector-mediated gene therapy. In this review we first discuss our current understanding of innate immune recognition of viruses in general, and then focus on the innate immune responses to viral vectors for gene therapy.
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Affiliation(s)
- Xiaopei Huang
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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298
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Yu JE, Knight AK, Radigan L, Marron TU, Zhang L, Sanchez-Ramón S, Cunningham-Rundles C. Toll-like receptor 7 and 9 defects in common variable immunodeficiency. J Allergy Clin Immunol 2009; 124:349-56, 356.e1-3. [PMID: 19592080 DOI: 10.1016/j.jaci.2009.05.019] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 05/10/2009] [Accepted: 05/12/2009] [Indexed: 12/21/2022]
Abstract
BACKGROUND Common variable immunodeficiency (CVID) is characterized by hypogammaglobulinemia, reduced numbers of peripheral blood isotype-switched memory B cells, and loss of plasma cells. OBJECTIVE Because Toll-like receptor (TLR) activation of B cells can initiate and potentially sustain normal B cell functions, we examined functional outcomes of TLR7 and TLR9 signaling in CVID B cells. METHODS TLR7-mediated, TLR7/8-mediated, and TLR9-mediated cell proliferation, isotype switch, and immunoglobulin production by control and CVID B cells or isolated naive and memory B cell subsets were examined. We quantitated TNF-alpha, IL-6, and IL-12 production in response to TLR1-9 ligands and measured IFN-alpha production by TLR7-stimulated PBMCs and isolated plasmacytoid dendritic cells (pDCs). IFN-beta mRNA expression by TLR3-stimulated fibroblasts was assessed. RESULTS Unlike CD27(+) B cells of controls, TLR7-activated, TLR7/8-activated, or TLR9-activated CVID B cells or isolated CD27(+) B cells did not proliferate, upregulate CD27, or shed surface IgD. TLR-stimulated CVID B cells failed to upregulate activation-induced cytosine deaminase mRNA or produce IgG and IgA. TLR7-stimulated PBMCs and pDCs produced little or no IFN-alpha. Reconstituting IFN-alpha in TLR7-stimulated CVID B-cell cultures facilitated proliferation, CD27 upregulation, and isotype switch. These TLR defects are restricted because CVID PBMCs stimulated with TLR ligands produced normal amounts of TNF-alpha, IL-6, and IL-12; TLR3-mediated expression of IFN-beta by CVID fibroblasts was normal. CONCLUSION Defective TLR7 and TLR9 signaling in CVID B cells and pDCs, coupled with deficient IFN-alpha, impairs CVID B cell functions and prevents TLR-mediated augmentation of humoral immunity in vivo.
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Affiliation(s)
- Joyce E Yu
- Department of Medicine, Mount Sinai Medical Center, New York, NY 10029, USA
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299
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Green NM, Laws A, Kiefer K, Busconi L, Kim YM, Brinkmann MM, Trail EH, Yasuda K, Christensen SR, Shlomchik MJ, Vogel S, Connor JH, Ploegh H, Eilat D, Rifkin IR, van Seventer JM, Marshak-Rothstein A. Murine B cell response to TLR7 ligands depends on an IFN-beta feedback loop. THE JOURNAL OF IMMUNOLOGY 2009; 183:1569-76. [PMID: 19587008 DOI: 10.4049/jimmunol.0803899] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Type I IFNs play an important, yet poorly characterized, role in systemic lupus erythematosus. To better understand the interplay between type I IFNs and the activation of autoreactive B cells, we evaluated the effect of type I IFN receptor (IFNAR) deficiency in murine B cell responses to common TLR ligands. In comparison to wild-type B cells, TLR7-stimulated IFNAR(-/-) B cells proliferated significantly less well and did not up-regulate costimulatory molecules. By contrast, IFNAR1(-/-) B cells did not produce cytokines, but did proliferate and up-regulate activation markers in response to other TLR ligands. These defects were not due to a difference in the distribution of B cell populations or a failure to produce a soluble factor other than a type I IFN. Instead, the compromised response pattern reflected the disruption of an IFN-beta feedback loop and constitutively low expression of TLR7 in the IFNAR1(-/-) B cells. These results highlight subtle differences in the IFN dependence of TLR7 responses compared with other TLR-mediated B cell responses.
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Affiliation(s)
- Nathaniel M Green
- Department of Microbiology, Boston University School of Medicine, Boston, MA 02118, USA
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300
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Barton GM, Kagan JC. A cell biological view of Toll-like receptor function: regulation through compartmentalization. Nat Rev Immunol 2009; 9:535-42. [PMID: 19556980 DOI: 10.1038/nri2587] [Citation(s) in RCA: 492] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
An emerging paradigm in innate immune signalling is that cell biological context can influence the outcome of a ligand-receptor interaction. In this Review we discuss how Toll-like receptor (TLR) activation and signal transduction are regulated by subcellular compartmentalization of receptors and downstream signalling components. In particular, we focus on the functional specialization of TLRs in the endosomal system. We discuss recent studies that illustrate how basic aspects of the cellular machinery contribute to TLR function and regulation. This emerging area of research will provide important information on how immune signal transduction networks depend on (and in some cases influence) the generic regulators that organize eukaryotic cells.
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Affiliation(s)
- Gregory M Barton
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720-3200, USA.
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