251
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Herskovits AA, Auerbuch V, Portnoy DA. Bacterial ligands generated in a phagosome are targets of the cytosolic innate immune system. PLoS Pathog 2007; 3:e51. [PMID: 17397264 PMCID: PMC1839167 DOI: 10.1371/journal.ppat.0030051] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Accepted: 02/16/2007] [Indexed: 12/13/2022] Open
Abstract
Macrophages are permissive hosts to intracellular pathogens, but upon activation become microbiocidal effectors of innate and cell-mediated immunity. How the fate of internalized microorganisms is monitored by macrophages, and how that information is integrated to stimulate specific immune responses is not understood. Activation of macrophages with interferon (IFN)–γ leads to rapid killing and degradation of Listeria monocytogenes in a phagosome, thus preventing escape of bacteria to the cytosol. Here, we show that activated macrophages induce a specific gene expression program to L. monocytogenes degraded in the phago-lysosome. In addition to activation of Toll-like receptor (TLR) signaling pathways, degraded bacteria also activated a TLR-independent transcriptional response that was similar to the response induced by cytosolic L. monocytogenes. More specifically, degraded bacteria induced a TLR-independent IFN-β response that was previously shown to be specific to cytosolic bacteria and not to intact bacteria localized to the phagosome. This response required the generation of bacterial ligands in the phago-lysosome and was largely dependent on nucleotide-binding oligomerization domain 2 (NOD2), a cytosolic receptor known to respond to bacterial peptidoglycan fragments. The NOD2-dependent response to degraded bacteria required the phagosomal membrane potential and the activity of lysosomal proteases. The NOD2-dependent IFN-β production resulted from synergism with other cytosolic microbial sensors. This study supports the hypothesis that in activated macrophages, cytosolic innate immune receptors are activated by bacterial ligands generated in the phagosome and transported to the cytosol. Innate immune recognition of microorganisms has a direct impact on the type and the magnitude of the immune response elicited. While recognition of microorganisms relies on receptors that sense pathogen-associated molecular patterns, (PAMPs), it was reasonable to suspect that immune cells could discriminate between live and dead bacteria. Listeria monocytogenes is an intracellular pathogenic bacterium used extensively as a model system for studying basic aspects of innate and acquired immunity. L. monocytogenes is internalized by macrophages, escapes from a vacuole, multiplies within the cytosol, and spreads from cell to cell without lysing the cells. We used wild-type and bacterial mutants of L. monocytogenes to demonstrate that macrophages not only respond differently to bacteria that are growing in the cytosol and to non-growing bacteria that are trapped in a vacuole, but that they also can discriminate between intact or degraded bacteria in the vacuole. We showed that macrophages induce specific immune response when bacteria are killed and degraded. This response was directly correlated to the ability of macrophages to degrade bacteria and involved receptors that were located in the host cell cytosol. These observations led us to suggest that bacterial degradation products may serve as messengers that inform immune cells that bacteria were killed and degraded. This information might affect directly the immune response, for example, by down-regulating inflammatory responses that can be deleterious. We call these bacterial degradation products PAMP-PM (PAMP–post-mortem).
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Affiliation(s)
- Anat A Herskovits
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Victoria Auerbuch
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Daniel A Portnoy
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- School of Public Health, University of California, Berkeley, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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252
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Marshall JD, Heeke DS, Gesner ML, Livingston B, Van Nest G. Negative regulation of TLR9-mediated IFN-alpha induction by a small-molecule, synthetic TLR7 ligand. J Leukoc Biol 2007; 82:497-508. [PMID: 17565046 DOI: 10.1189/jlb.0906575] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Toll-like receptors (TLRs) are a family of molecules that function as sensors for the detection of foreign pathogens through the recognition of nonvariable microbial motifs. Although numerous studies have focused on singular TLRs, less attention has been focused on how simultaneous signaling of multiple TLRs may result in counter-regulation of the effects of each. Here, we examine the counter-regulation that occurs during simultaneous stimulation of TLR7 and TLR9 on human plasmacytoid dendritic cells (PDCs) and B cells. Interestingly, we observed that the capacity for potent IFN-alpha-induction by TLR9 ligands like CpG-C and CpG-A is markedly reduced by concurrent small molecule TLR7 stimulation. However, this inhibition is specific to particular CpG motif-containing immunostimulatory sequence (ISS) functions such as IFN-alpha induction and BDCA-2 down-regulation. Other ISS activities such as PDC expression of CD80/CD86, secretion of IL-6, and B cell proliferation are not altered by the presence of TLR7 ligands (TLR7Ls). In concordance with the ability of TLR7Ls to decrease IFN-alpha secretion induced by ISS, we also find that the expression of interferon regulatory factor-7 (IRF-7), a transcriptional factor critical for IFN-alpha expression, is reduced. Furthermore, down-regulation of TLR9 mRNA expression is accelerated after TLR7 stimulation. These data indicate that TLR7 and TLR9 costimulation do not combine synergistically for IFN-alpha induction and demonstrate that, instead, a negative feedback mechanism has evolved, possibly to prevent levels of IFN-alpha secretion potentially detrimental to the host.
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253
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Newman KC, Riley EM. Whatever turns you on: accessory-cell-dependent activation of NK cells by pathogens. Nat Rev Immunol 2007; 7:279-91. [PMID: 17380157 DOI: 10.1038/nri2057] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Natural killer (NK) cells have a crucial role in combating infections and cancers and their surface receptors can directly recognize and respond to damaged, transformed or non-self cells. Whereas some virus-infected cells are recognized by this same route, NK-cell responses to many pathogens are triggered by a different mechanism. Activation of NK cells by these pathogens requires the presence of accessory cells such as monocytes, macrophages and dendritic cells. Recent studies have identified numerous pathogen-recognition receptors that enable accessory cells to recognize different pathogens and subsequently transmit signals--both soluble and contact-dependent--to NK cells, which respond by upregulating their cytotoxic potential and the production of inflammatory cytokines.
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Affiliation(s)
- Kirsty C Newman
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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254
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Lambiase A, Coassin M, Costa N, Lauretti P, Micera A, Ghinelli E, Aloe L, Rama P, Bonini S. Topical treatment with nerve growth factor in an animal model of herpetic keratitis. Graefes Arch Clin Exp Ophthalmol 2007; 246:121-7. [PMID: 17479276 DOI: 10.1007/s00417-007-0593-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 04/04/2007] [Accepted: 04/05/2007] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND In vitro and in vivo studies demonstrated the antiviral efficacy of nerve growth factor (NGF) and its cyto-protective effect in herpes simplex virus (HSV)-infected cells. The aims of this study were to evaluate the role of endogenous NGF in HSV corneal infection, and the effects of topical NGF treatment on herpetic keratitis. METHODS Herpetic keratitis was induced in 40 rabbits with the HSV-1 McKrae strain. Animals were divided into four groups, and treated with topical neutralizing anti-NGF antibodies, NGF, acyclovir or balanced salt solution (BSS) respectively. The clinical course of HSV keratitis was evaluated and scored by slit-lamp examination. In addition, biochemical (immunohistochemistry for glycoprotein D) and molecular (nested PCR for glycoprotein D) analyses were carried out to estimate viral replication. RESULTS Treatment with anti-NGF antibodies induced a more severe keratitis associated with increased biochemical and molecular markers of active viral replication. Two animals in this group developed lethal HSV encephalitis. Conversely, topical treatment with NGF induced a significant amelioration of clinical and laboratory parameters when compared to the BSS treated group (control). No significant differences were observed between NGF- and acyclovir-treated groups. CONCLUSIONS This study demonstrated the crucial role of endogenous NGF in herpetic keratitis. The comparable effects of NGF and acyclovir confirm the antiviral activity of NGF, and indicate a potential use of topical NGF in herpetic keratitis.
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Affiliation(s)
- Alessandro Lambiase
- Interdisciplinary Center for Biomedical Research (CIR), Laboratory of Ophthalmology, University Campus Bio-Medico of Rome, Via E. Longoni, 83 00155, Rome, Italy
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255
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Puro R, Schneider RJ. Tumor necrosis factor activates a conserved innate antiviral response to hepatitis B virus that destabilizes nucleocapsids and reduces nuclear viral DNA. J Virol 2007; 81:7351-62. [PMID: 17475655 PMCID: PMC1933346 DOI: 10.1128/jvi.00554-07] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Tumor necrosis factor (TNF) is critical for the control of hepatitis B virus (HBV) in the clinical setting and in model systems. TNF induces noncytopathic suppression and clearance of HBV in animal models, possibly through reduction of viral nucleocapsids, but the mechanism is not well described. Here, we demonstrate the molecular mechanism and broad host range for TNF action against HBV. We show that TNF rapidly blocks HBV replication by promoting destabilization of preexisting cytoplasmic viral nucleocapsids containing viral RNA and DNA, as well as empty nucleocapsids. TNF destabilized human HBV nucleocapsids in a variety of human hepatocytic cell lines and in primary rat hepatocytes and also destabilized duck HBV (DHBV) nucleocapsids in chicken hepatocytic cells. Lysates from TNF-treated uninfected cells also destabilized HBV nucleocapsids in vitro. Moreover, inhibition of DHBV DNA replication by TNF blocks nuclear accumulation of the viral transcription template, maintenance of which is essential for the establishment and maintenance of chronic infection. We show that TNF destabilization of HBV nucleocapsids does not involve ubiquitination or methylation of the viral core protein and is not mediated by the nitric oxide free radical arm of the TNF pathway. These results define a novel antiviral mechanism mediated by TNF against multiple types of HBVs in different species.
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Affiliation(s)
- Robyn Puro
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
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256
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Humann J, Bjordahl R, Andreasen K, Lenz LL. Expression of the p60 autolysin enhances NK cell activation and is required for listeria monocytogenes expansion in IFN-gamma-responsive mice. THE JOURNAL OF IMMUNOLOGY 2007; 178:2407-14. [PMID: 17277147 DOI: 10.4049/jimmunol.178.4.2407] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Both peptidoglycan and muropeptides potently modulate inflammatory and innate immune responses. The secreted Listeria monocytogenes p60 autolysin digests peptidoglycan and promotes bacterial infection in vivo. Here, we report that p60 contributes to bacterial subversion of NK cell activation and innate IFN-gamma production. L. monocytogenes deficient for p60 (Deltap60) competed well for expansion in mice doubly deficient for IFNAR1 and IFN-gammaR1 or singly deficient for IFN-gammaR1, but not in wild-type, IFNAR1(-/-), or TLR2(-/-) mice. The restored competitiveness of p60-deficient bacteria suggested a specific role for p60 in bacterial subversion of IFN-gamma-mediated immune responses, since in vivo expansion of three other mutant L. monocytogenes strains (DeltaActA, DeltaNamA, and DeltaPlcB) was not complemented in IFN-gammaR1(-/-) mice. Bacterial expression of p60 was not required to induce socs1, socs3, and il10 expression in infected mouse bone marrow macrophages but did correlate with enhanced production of IL-6, IL-12p70, and most strikingly IFN-gamma. The primary source of p60-dependent innate IFN-gamma was NK cells, whereas bacterial p60 expression did not significantly alter innate IFN-gamma production by T cells. The mechanism for p60-dependent NK cell stimulation was also indirect, given that treatment with purified p60 protein failed to directly activate NK cells for IFN-gamma production. These data suggest that p60 may act on infected cells to indirectly enhance NK cell activation and increase innate IFN-gamma production, which presumably promotes early bacterial expansion through its immunoregulatory effects on bystander cells. Thus, the simultaneous induction of IFN-gamma production and factors that inhibit IFN-gamma signaling may be a common strategy for misdirection of early antibacterial immunity.
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Affiliation(s)
- Jessica Humann
- Integrated Department of Immunology, National Jewish Medical and Research Center, Denver, CO 80206, USA
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257
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Mancuso G, Midiri A, Biondo C, Beninati C, Zummo S, Galbo R, Tomasello F, Gambuzza M, Macrì G, Ruggeri A, Leanderson T, Teti G. Type I IFN signaling is crucial for host resistance against different species of pathogenic bacteria. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2007; 178:3126-33. [PMID: 17312160 DOI: 10.4049/jimmunol.178.5.3126] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
It is known that host cells can produce type I IFNs (IFN-alphabeta) after exposure to conserved bacterial products, but the functional consequences of such responses on the outcome of bacterial infections are incompletely understood. We show in this study that IFN-alphabeta signaling is crucial for host defenses against different bacteria, including group B streptococci (GBS), pneumococci, and Escherichia coli. In response to GBS challenge, most mice lacking either the IFN-alphabetaR or IFN-beta died from unrestrained bacteremia, whereas all wild-type controls survived. The effect of IFN-alphabetaR deficiency was marked, with mortality surpassing that seen in IFN-gammaR-deficient mice. Animals lacking both IFN-alphabetaR and IFN-gammaR displayed additive lethality, suggesting that the two IFN types have complementary and nonredundant roles in host defenses. Increased production of IFN-alphabeta was detected in macrophages after exposure to GBS. Moreover, in the absence of IFN-alphabeta signaling, a marked reduction in macrophage production of IFN-gamma, NO, and TNF-alpha was observed after stimulation with live bacteria or with purified LPS. Collectively, our data document a novel, fundamental function of IFN-alphabeta in boosting macrophage responses and host resistance against bacterial pathogens. These data may be useful to devise alternative strategies to treat bacterial infections.
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Affiliation(s)
- Giuseppe Mancuso
- Dipartimento di Patologia e Microbiologia Sperimentale, Università degli Studi di Messina, Via Consolare Valeria 1, 98125 Messina, Italy
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258
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Martinelli E, Cicala C, Van Ryk D, Goode DJ, Macleod K, Arthos J, Fauci AS. HIV-1 gp120 inhibits TLR9-mediated activation and IFN-{alpha} secretion in plasmacytoid dendritic cells. Proc Natl Acad Sci U S A 2007; 104:3396-401. [PMID: 17360657 PMCID: PMC1805537 DOI: 10.1073/pnas.0611353104] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2006] [Indexed: 12/11/2022] Open
Abstract
Plasmacytoid dendritic cells (pDCs) play a central role in innate and adaptive immune responses against viral infections. pDCs secrete type I IFNs and proinflammatory cytokines upon stimulation by either TLR7 or TLR9. Throughout the course of HIV infection, the production of type-I IFNs is profoundly impaired, and total pDC cell counts in peripheral blood correlates inversely with viral load and positively with CD4(+) T cell count. The origin of these defects is unclear. pDCs express CD4, CCR5, and CXCR4, the primary receptor and coreceptors, respectively, for the HIV envelope; yet little is known concerning the effects of the viral envelope on these cells. Here, we show that exposure of pDCs to gp120 results in the suppression of activation of these cells. This suppression is specific for TLR9-mediated responses, because TLR7-mediated responses are unaffected by gp120. gp120 also suppressed TLR9-mediated induction of proinflammatory cytokines and expression of CD83, a marker of DC activation. Finally, gp120 suppressed pDC-induced cytolytic activity of natural killer cells. Taken together, these data demonstrate that the direct interaction of HIV-1 gp120 with pDCs interferes with TLR9 activation resulting in a decreased ability of pDCs to secrete antiviral and inflammatory factors that play a central role in initiating host immune responses against invading pathogens.
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Affiliation(s)
- Elena Martinelli
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Disease, Bethesda, MD 20892, USA.
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259
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Stanley SA, Johndrow JE, Manzanillo P, Cox JS. The Type I IFN Response to Infection with Mycobacterium tuberculosis Requires ESX-1-Mediated Secretion and Contributes to Pathogenesis. THE JOURNAL OF IMMUNOLOGY 2007; 178:3143-52. [PMID: 17312162 DOI: 10.4049/jimmunol.178.5.3143] [Citation(s) in RCA: 326] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The ESX-1 secretion system is a major determinant of Mycobacterium tuberculosis virulence, although the pathogenic mechanisms resulting from ESX-1-mediated transport remain unclear. By global transcriptional profiling of tissues from mice infected with either wild-type or ESX-1 mutant bacilli, we found that host genes controlled by ESX-1 in vivo are predominantly IFN regulated. ESX-1-mediated secretion is required for the production of host type I IFNs during infection in vivo and in macrophages in vitro. The macrophage signaling pathway leading to the production of type I IFN required the host kinase TANK-binding kinase 1 and occurs independently of TLR signaling. Importantly, the induction of type I IFNs during M. tuberculosis infection is a pathogenic mechanism as mice lacking the type I IFNR were more restrictive for bacterial growth in the spleen than wild-type mice, although growth in the lung was unaffected. We propose that the ESX-1 secretion system secretes effectors into the cytosol of infected macrophages, thereby triggering the type I IFN response for the manipulation of host immunity.
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Affiliation(s)
- Sarah A Stanley
- Department of Microbiology and Immunology, University of California-San Francisco, San Francisco, CA 94158, USA
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260
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Wang JP, Liu P, Latz E, Golenbock DT, Finberg RW, Libraty DH. Flavivirus activation of plasmacytoid dendritic cells delineates key elements of TLR7 signaling beyond endosomal recognition. THE JOURNAL OF IMMUNOLOGY 2007; 177:7114-21. [PMID: 17082628 DOI: 10.4049/jimmunol.177.10.7114] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
TLR7 senses RNA in endosomal compartments. TLR7 expression and signaling have been demonstrated in plasmacytoid and myeloid dendritic cells, B cells, and T cells. The regulation of TLR7 signaling can play a crucial role in shaping the immune response to RNA viruses with different cellular tropisms, and in developing adjuvants capable of promoting balanced humoral and cell-mediated immunity. We used unique characteristics of two ssRNA viruses, dengue virus and influenza virus, to delineate factors that regulate viral RNA-human TLR7 signaling beyond recognition in endosomal compartments. Our data show that TLR7 recognition of enveloped RNA virus genomes is linked to virus fusion or uncoating from the endosome. The signaling threshold required to activate TLR7-type I IFN production is greater than that required to activate TLR7-NF-kappaB-IL-8 production. The higher order structure of viral RNA appears to be an important determinant of TLR7-signaling potency. A greater understanding of viral RNA-TLR7 activity relationships will promote rational approaches to interventional and vaccine strategies for important human viral pathogens.
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Affiliation(s)
- Jennifer P Wang
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA.
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261
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Huang YH, Chou MH, Du YY, Huang CC, Wu CL, Chen CL, Chuang JH. Expression of toll-like receptors and type 1 interferon specific protein MxA in biliary atresia. J Transl Med 2007; 87:66-74. [PMID: 17075576 DOI: 10.1038/labinvest.3700490] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Viral infection and type I interferon have been implicated in the pathogenesis of biliary atresia (BA), but the expression of toll-like receptors (TLRs) that recognize viruses, as well as of type 1 interferon specific signaling molecules are still unknown in BA. Fresh liver tissues were obtained from patients in early and late stage of BA and from patients with choledochal cyst (CC), as well as from normal controls receiving liver resection for benign lesion other than cholestasis or fibrosis. Archived liver tissues from patients with neonatal hepatitis (NH) were obtained for immunohistochemical studies. TLR2, 3, 4, 7 and 9 that recognized Gram-positive bacteria, double-stranded RNA virus, lipopolysaccharide, single-stranded RNA virus and DNA virus, respectively, were studied. Real-time quantitative reverse transcription polymerase chain reaction (QRT-PCR) was used to quantitate TLR, type I interferon specific molecule MxA, interleukin-6 (IL-6) and IL-8 mRNA expression and immunohistochemistry for TLR 7 and MxA protein staining. These results show that there were significantly higher TLR7 and lower TLR3 and TLR9 mRNA expression in early stage of BA than in CC. MxA mRNA expression was also significantly higher in early stage of BA and in CC than in late stage of BA. Immunoreactive TLR7 and MxA staining was higher in early stage of BA than in late stage of BA, NH and CC, which was associated with significantly higher IL-8 mRNA expression in BA than in CC. The results implicate involvement of TLRs, particularly TLR7, and type 1 specific interferon signaling in the pathogenesis of BA, especially in early stage, which is associated with upregulation of inflammatory cytokines IL-8.
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Affiliation(s)
- Ying-Hsien Huang
- Department of Pediatrics, Chang Gung Memorial Hospital-Kaohsiung Medical Center and the Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Kaohsiung, Taiwan, ROC
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262
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Chen M, Gerlier D. Viral hijacking of cellular ubiquitination pathways as an anti-innate immunity strategy. Viral Immunol 2006; 19:349-62. [PMID: 16987055 DOI: 10.1089/vim.2006.19.349] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Viruses are obligate parasites of host cells. Virus-host coevolution has selected virus for growth despite antiviral defenses set up by hosting cells and organisms. Ubiquitin conjugation onto proteins, through a cascade of reactions mediated by E1 (ubiquitin-activating enzyme) and E2 and E3 (ubiquitin- conjugating ligases), is one of the major regulatory systems that, in particular, tightly controls the concentration of cellular proteins by sorting them for degradation. The combined diversity of E2 and E3 ligases ensures the selective/specific ubiquitination of a large number of protein substrates within the cell interior. Therefore it is not surprising that several viruses encode proteins with E3 ubiquitin ligase activities that target cellular proteins playing a key role in innate antiviral mechanisms.
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Affiliation(s)
- Mingzhou Chen
- CNRS, Université de Lyon, UMR5537, Laboratoire de Virologie et Pathogenèse Virale, IFR Laennec, Lyon, France
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263
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Harari A, Dutoit V, Cellerai C, Bart PA, Du Pasquier RA, Pantaleo G. Functional signatures of protective antiviral T-cell immunity in human virus infections. Immunol Rev 2006; 211:236-54. [PMID: 16824132 DOI: 10.1111/j.0105-2896.2006.00395.x] [Citation(s) in RCA: 217] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The most common human viruses have different abilities to establish persistent chronic infection. Virus-specific T-cell responses are critical in the control of virus replication and in the prevention of disease in chronic infection. A large number of phenotypic markers and a series of functions have been used to characterize virus-specific CD4+ and CD8+ T-cell responses, and these studies have shown great phenotypic and functional heterogeneity of the T-cell responses against different viruses. The heterogeneity of the T-cell response has been proposed to be specific to each virus. However, over the past 2 years, several studies have provided evidence that the phenotypic and functional heterogeneity of CD4+ and CD8+ T-cell responses is predominantly regulated by the levels of antigen load. The levels of antigen load modulate the phenotypic and functional patterns of the T-cell response within the same virus infection. Furthermore, the functional characterization of virus-specific CD4+ and CD8+ T-cell responses has identified signatures of protective antiviral immunity. Polyfunctional, i.e. interleukin-2 and interferon-gamma (IFN-gamma) secretion and proliferation, and not monofunctional, i.e. IFN-gamma secretion, CD4+ and CD8+ T-cell responses represent correlates of protective antiviral immunity in chronic virus infections.
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Affiliation(s)
- Alexandre Harari
- Laboratory of AIDS Immunopathogenesis, Division of Immunology and Allergy, Department of Medicine, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
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264
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Zhou H, Perlman S. Mouse hepatitis virus does not induce Beta interferon synthesis and does not inhibit its induction by double-stranded RNA. J Virol 2006; 81:568-74. [PMID: 17079305 PMCID: PMC1797428 DOI: 10.1128/jvi.01512-06] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mouse hepatitis virus (MHV) does not induce interferon (IFN) production in fibroblasts or bone marrow-derived dendritic cells. In this report, we show that the essential IFN-beta transcription factors NF-kappaB and IFN regulatory factor 3 are not activated for nuclear translocation and gene induction during infection. However, MHV was unable to inhibit the activation of these factors and subsequent IFN-beta production induced by poly(I:C). Further, MHV infection did not inhibit IFN-beta production mediated by known host pattern recognition receptors (PRRs) (RIG-I, Mda-5, and TLR3). These results are consistent with the notion that double-stranded RNA, produced during MHV infection, is not accessible to cellular PRRs.
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Affiliation(s)
- Haixia Zhou
- Department of Microbiology, University of Iowa, Bowen Science Building 3-730, Iowa City, IA 52242, USA
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265
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Shiina M, Kobayashi K, Kobayashi T, Kondo Y, Ueno Y, Shimosegawa T. Dynamics of immature subsets of dendritic cells during antiviral therapy in HLA-A24-positive chronic hepatitis C patients. J Gastroenterol 2006; 41:758-764. [PMID: 16988764 DOI: 10.1007/s00535-006-1843-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2006] [Accepted: 04/12/2006] [Indexed: 02/04/2023]
Abstract
BACKGROUND The cellular immune response is important in chronic hepatitis C (CHC). To better understand its mechanism, we examined dendritic cells (DCs) and hepatitis C virus (HCV)-specific cytotoxic T cells (CTLs), which are thought to contribute to liver injury and viral clearance. METHODS CHC patients received 24 weeks of interferon-alpha-based antiviral therapy. We analyzed time-sequential frequencies of peripheral DCs, classified as myeloid DCs (mDCs) or plasmacytoid DCs (pDCs), together with peptide major histocompatibility class I tetramers, epitope specific for HCV core 129-137 (t*24/c129) or HCV NS3 1296-1304 (t*24/ns1294), directly ex vivo. RESULTS The mDC and pDC populations changed in parallel (P < 0.05), showing a significant transient decrease at weeks 12 and 16 during the therapy, and then recovering. However, neither of the tetramer results showed a direct correlation with the kinetics of peripheral DCs. CONCLUSIONS There is an apparent effect of antiviral therapy or a subsequent reduction of HCV on host immunity, but the effect may not include the induction of CTLs in CHC.
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Affiliation(s)
- Masaaki Shiina
- Division of Gastroenterology, Tohoku University Graduate School of Medicine, Sendai, Japan
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266
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Hippenstiel S, Opitz B, Schmeck B, Suttorp N. Lung epithelium as a sentinel and effector system in pneumonia--molecular mechanisms of pathogen recognition and signal transduction. Respir Res 2006; 7:97. [PMID: 16827942 PMCID: PMC1533821 DOI: 10.1186/1465-9921-7-97] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Accepted: 07/08/2006] [Indexed: 12/22/2022] Open
Abstract
Pneumonia, a common disease caused by a great diversity of infectious agents is responsible for enormous morbidity and mortality worldwide. The bronchial and lung epithelium comprises a large surface between host and environment and is attacked as a primary target during lung infection. Besides acting as a mechanical barrier, recent evidence suggests that the lung epithelium functions as an important sentinel system against pathogens. Equipped with transmembranous and cytosolic pathogen-sensing pattern recognition receptors the epithelium detects invading pathogens. A complex signalling results in epithelial cell activation, which essentially participates in initiation and orchestration of the subsequent innate and adaptive immune response. In this review we summarize recent progress in research focussing on molecular mechanisms of pathogen detection, host cell signal transduction, and subsequent activation of lung epithelial cells by pathogens and their virulence factors and point to open questions. The analysis of lung epithelial function in the host response in pneumonia may pave the way to the development of innovative highly needed therapeutics in pneumonia in addition to antibiotics.
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Affiliation(s)
- Stefan Hippenstiel
- Department of Internal Medicine/Infectious Diseases and Respiratory Medicine, Charité – Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Bastian Opitz
- Department of Internal Medicine/Infectious Diseases and Respiratory Medicine, Charité – Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Bernd Schmeck
- Department of Internal Medicine/Infectious Diseases and Respiratory Medicine, Charité – Universitätsmedizin Berlin, 13353 Berlin, Germany
| | - Norbert Suttorp
- Department of Internal Medicine/Infectious Diseases and Respiratory Medicine, Charité – Universitätsmedizin Berlin, 13353 Berlin, Germany
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267
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Sun Q, Sun L, Liu HH, Chen X, Seth RB, Forman J, Chen ZJ. The specific and essential role of MAVS in antiviral innate immune responses. Immunity 2006; 24:633-42. [PMID: 16713980 DOI: 10.1016/j.immuni.2006.04.004] [Citation(s) in RCA: 464] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 04/18/2006] [Accepted: 04/25/2006] [Indexed: 12/15/2022]
Abstract
The mitochondrial antiviral signaling protein (MAVS) mediates the activation of NFkappaB and IRFs and the induction of interferons in response to viral infection. In vitro studies have also suggested that MAVS is required for interferon induction by cytosolic DNA, but the in vivo evidence is lacking. By generating MAVS-deficient mice, here we show that loss of MAVS abolished viral induction of interferons and prevented the activation of NFkappaB and IRF3 in multiple cell types, except plasmacytoid dendritic cells (pDCs). However, MAVS was not required for interferon induction by cytosolic DNA or by Listeria monocytogenes. Mice lacking MAVS were viable and fertile, but they failed to induce interferons in response to poly(I:C) stimulation and were severely compromised in immune defense against viral infection. These results provide the in vivo evidence that the cytosolic viral signaling pathway through MAVS is specifically required for innate immune responses against viral infection.
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Affiliation(s)
- Qinmiao Sun
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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268
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Wong JJY, Pung YF, Sze NSK, Chin KC. HERC5 is an IFN-induced HECT-type E3 protein ligase that mediates type I IFN-induced ISGylation of protein targets. Proc Natl Acad Sci U S A 2006; 103:10735-40. [PMID: 16815975 PMCID: PMC1484417 DOI: 10.1073/pnas.0600397103] [Citation(s) in RCA: 224] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Type I IFNs induce the expression of IFN-stimulated gene 15 (ISG15) and its conjugation to cellular targets. ISGylation is a multistep process involving IFN-inducible Ube1L, UbcH8, and a yet-to-be identified E3 ligase. Here we report the identification of an IFN-induced HECT-type E3 protein ligase, HERC5/Ceb1, which mediates ISGylation. We also defined a number of proteins modified by ISG15 after IFN triggering or HERC5 overexpression. A reduction in endogenous HERC5 by small interfering RNA inhibition blocks the IFN-induced ISG15 conjugation. Conversely, HERC5 coexpression with Ube1L and UbcH8 induces the ISG15 conjugation in vivo independent of IFN stimulation. A targeted substitution of Cys-994 to Ala in the HECT domain of HERC5 completely abrogates its E3 protein ligase activity. Therefore, this study demonstrates that HERC5/Ceb1 is involved in the conjugation of ISG15 to cellular proteins.
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Affiliation(s)
| | | | - Newman Siu-Kwan Sze
- Proteomics Laboratory, Genome Institute of Singapore, 60 Biopolis Street, #02-01 Genome, Singapore 138672
| | - Keh-Chuang Chin
- *Immunology and Virology Laboratory and
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, Block MD4, 5 Science Drive 2, Singapore 117597; and
- Immunology Program, National University of Singapore, Office of Life Sciences Satellite Laboratory, Defense Medical and Environmental Research Institute Building, #03-01, 27 Medical Drive, Singapore 117510
- To whom correspondence should be addressed. E-mail:
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