151
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Reeves RK, Fultz PN. Disparate effects of acute and chronic infection with SIVmac239 or SHIV-89.6P on macaque plasmacytoid dendritic cells. Virology 2007; 365:356-68. [PMID: 17490699 PMCID: PMC2043480 DOI: 10.1016/j.virol.2007.03.055] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 03/02/2007] [Accepted: 03/30/2007] [Indexed: 12/13/2022]
Abstract
Blood plasmacytoid dendritic cells (pDCs) contribute to both innate and adaptive immune responses by secreting high levels of IFN-alpha following acute bacterial and viral infections and indirectly by augmenting cell-mediated immunity. Cross-sectional studies have shown that the number of circulating pDCs in HIV patients, compared to that in uninfected individuals, is reduced. However, since the time of infection is usually unknown in HIV-infected patients, pDC-virus interactions that occur immediately after virus exposure are poorly understood. The current study investigated pDC dynamics during acute and chronic infections of macaques with either SIVmac239 or the pathogenic SIV-HIV chimera, SHIV-89.6P, as models for HIV infection. In three rhesus and three pig-tailed macaques infected intravenously with SIVmac239, the percentages of pDCs in blood declined 2- to 6-fold during the first 6 weeks after infection and remained depressed throughout the disease course. Surprisingly, no consistent, comparable decline in peripheral blood pDCs was observed in six macaques infected with SHIV-89.6P. In this latter group, percentages of pDCs did not correlate with CD4(+) T cells, but there was an inverse relationship with viral load. In addition, when compared to naïve controls, the percentages of pDCs were reduced in spleens and peripheral lymph nodes of SIVmac239- but not SHIV-89.6P-infected animals that had progressed to AIDS. Proviral DNA was detected during the acute phase in pDCs isolated from macaques infected with either virus. These results imply that, even though macaque pDCs can be infected by both SIVmac239 and SHIV-89.6P, the subsequent effects on in vivo pathogenesis differ. The underlying mechanism(s) for these differences is unclear, but the selection of SIV or SHIV as a challenge virus might influence the outcome of some studies, such as those evaluating vaccines or the therapeutic efficacy of drugs.
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Affiliation(s)
| | - Patricia N. Fultz
- Department of Microbiology, University of Alabama at Birmingham, BBRB 509E, 845 19th St. South, Birmingham, AL 35294, USA
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152
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Wykes MN, Liu XQ, Beattie L, Stanisic DI, Stacey KJ, Smyth MJ, Thomas R, Good MF. Plasmodium strain determines dendritic cell function essential for survival from malaria. PLoS Pathog 2007; 3:e96. [PMID: 17616976 PMCID: PMC1904473 DOI: 10.1371/journal.ppat.0030096] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2006] [Accepted: 05/21/2007] [Indexed: 11/19/2022] Open
Abstract
The severity of malaria can range from asymptomatic to lethal infections involving severe anaemia and cerebral disease. However, the molecular and cellular factors responsible for these differences in disease severity are poorly understood. Identifying the factors that mediate virulence will contribute to developing antiparasitic immune responses. Since immunity is initiated by dendritic cells (DCs), we compared their phenotype and function following infection with either a nonlethal or lethal strain of the rodent parasite, Plasmodium yoelii, to identify their contribution to disease severity. DCs from nonlethal infections were fully functional and capable of secreting cytokines and stimulating T cells. In contrast, DCs from lethal infections were not functional. We then transferred DCs from mice with nonlethal infections to mice given lethal infections and showed that these DCs mediated control of parasitemia and survival. IL-12 was necessary for survival. To our knowledge, our studies have shown for the first time that during a malaria infection, DC function is essential for survival. More importantly, the functions of these DCs are determined by the strain of parasite. Our studies may explain, in part, why natural malaria infections may have different outcomes.
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Affiliation(s)
- Michelle N Wykes
- The Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Xue Q Liu
- The Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Lynette Beattie
- The Queensland Institute of Medical Research, Brisbane, Queensland, Australia
- Immunology and Infection Unit, University of York, York, United Kingdom
| | - Danielle I Stanisic
- The Queensland Institute of Medical Research, Brisbane, Queensland, Australia
- Infection and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Katryn J Stacey
- Institute for Molecular Bioscience, CRC for Chronic Inflammatory Diseases, University of Queensland, Brisbane, Queensland, Australia
| | - Mark J Smyth
- Cancer Immunology Program, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
| | - Ranjeny Thomas
- Centre for Immunology and Cancer Research, University of Queensland, Woolloongabba, Queensland, Australia
| | - Michael F Good
- The Queensland Institute of Medical Research, Brisbane, Queensland, Australia
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153
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Newman KC, Korbel DS, Hafalla JC, Riley EM. Cross-talk with myeloid accessory cells regulates human natural killer cell interferon-gamma responses to malaria. PLoS Pathog 2007; 2:e118. [PMID: 17154717 PMCID: PMC1687207 DOI: 10.1371/journal.ppat.0020118] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Accepted: 09/21/2006] [Indexed: 11/19/2022] Open
Abstract
Data from a variety of experimental models suggest that natural killer (NK) cells require signals from accessory cells in order to respond optimally to pathogens, but the precise identity of the cells able to provide such signals depends upon the nature of the infectious organism. Here we show that the ability of human NK cells to produce interferon-γ in response to stimulation by Plasmodium falciparum–infected red blood cells (iRBCs) is strictly dependent upon multiple, contact-dependent and cytokine-mediated signals derived from both monocytes and myeloid dendritic cells (mDCs). Contrary to some previous reports, we find that both monocytes and mDCs express an activated phenotype following short-term incubation with iRBCs and secrete pro-inflammatory cytokines. The magnitude of the NK cell response (and of the KIR− CD56bright NK cell population in particular) is tightly correlated with resting levels of accessory cell maturation, indicating that heterogeneity of the NK response to malaria is a reflection of deep-rooted heterogeneity in the human innate immune system. Moreover, we show that NK cells are required to maintain the maturation status of resting mDCs and monocytes, providing additional evidence for reciprocal regulation of NK cells and accessory cells. However, NK cell–derived signals are not required for activation of accessory cells by either iRBCs or bacterial lipolysaccharide. Together, these data suggest that there may be differences in the sequence of events required for activation of NK cells by non-viral pathogens compared to the classical model of NK activation by virus-infected or major histocompatibility complex–deficient cells. These findings have far-reaching implications for the study of immunity to infection in human populations. The outcome of infection is determined both by the ability to limit the initial phase of pathogen colonisation and by the ability to mount an effective adaptive immune response. Both of these processes are influenced by innate immune responses, of which a crucial component can be the ability of natural killer (NK) cells to secrete pro-inflammatory cytokines. Studies in both humans and mice indicate that the magnitude of the early (innate) interferon (IFN)–γ response is a crucial determinant of the outcome of malaria infection. In this study, Newman et al. show that activation of human NK cells by Plasmodium falciparum–infected red blood cells to produce IFN-γ is strictly dependent upon, and regulated by, contact-mediated and soluble (cytokine) signals from two accessory cell populations (myeloid dendritic cells and monocytes). Furthermore, the magnitude of the human NK cell IFN-γ response to P. falciparum–infected red blood cells is highly correlated with levels of expression of co-stimulatory molecules on resting accessory cells. These findings suggest that it might be possible to predict the magnitude of the innate cytokine response, and possibly even susceptibility to malarial disease, from the phenotype of resting monocytes. In addition, these data contribute to the development of a new model of NK activation by non-viral pathogens in which activation of accessory cells precedes, rather than follows, NK activation.
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Affiliation(s)
- Kirsty C Newman
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Daniel S Korbel
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Julius C Hafalla
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Eleanor M Riley
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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154
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deWalick S, Amante FH, McSweeney KA, Randall LM, Stanley AC, Haque A, Kuns RD, MacDonald KPA, Hill GR, Engwerda CR. Cutting edge: conventional dendritic cells are the critical APC required for the induction of experimental cerebral malaria. THE JOURNAL OF IMMUNOLOGY 2007; 178:6033-7. [PMID: 17475826 DOI: 10.4049/jimmunol.178.10.6033] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Cerebral malaria (CM) is a serious complication of Plasmodium falciparum infection, causing significant morbidity and mortality among young children and nonimmune adults in the developing world. Although previous work on experimental CM has identified T cells as key mediators of pathology, the APCs and subsets therein required to initiate immunopathology remain unknown. In this study, we show that conventional dendritic cells but not plasmacytoid dendritic cells are required for the induction of malaria parasite-specific CD4+ T cell responses and subsequent experimental CM. These data have important implications for the development of malaria vaccines and the therapeutic management of CM.
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Affiliation(s)
- Saskia deWalick
- Queensland Institute of Medical Research, Herston, Australia
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155
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Coban C, Ishii KJ, Horii T, Akira S. Manipulation of host innate immune responses by the malaria parasite. Trends Microbiol 2007; 15:271-8. [PMID: 17466521 DOI: 10.1016/j.tim.2007.04.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Revised: 03/26/2007] [Accepted: 04/11/2007] [Indexed: 10/23/2022]
Abstract
It has long been known that malaria infection causes host immune modulation by various mechanisms. However, the role of Toll-like receptors (TLRs) in mediating innate immune responses to parasite-derived components during the blood stages of malaria has only recently been described. TLRs might have an important role in pathogenesis during malaria infection, as supported by genetic analyses in mice and humans. Moreover, recent findings revealed that sporozoites can partially differentiate in lymph nodes and that liver stages induce the formation of previously unknown parasite-filled vesicles (merosomes) that could function as immune escape machinery. Elucidation of the mechanisms by which the host innate immune system responds to, and/or is manipulated by, Plasmodium infection will hopefully lead to discoveries of potential targets that will ultimately prevent and/or intervene in malaria infection.
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Affiliation(s)
- Cevayir Coban
- Department of Host Defense, Research Institute for Microbial Diseases, Osaka University, Yamadaoka 3-1, Suita City, Osaka 565-0871, Japan
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156
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Lamb TJ, Voisine C, Koernig S, Egan CA, Harnett W, Langhorne J. The pathology of Plasmodium chabaudi infection is not ameliorated by the secreted filarial nematode immunomodulatory molecule, ES-62. Parasite Immunol 2007; 29:271-6. [PMID: 17430551 DOI: 10.1111/j.1365-3024.2007.00941.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ES-62 is a phosphorylcholine-containing glycoprotein secreted by filarial nematodes. This molecule has been shown to reduce the severity of inflammation in collagen-induced arthritis (CIA) in mice, a model of rheumatoid arthritis, via down-regulation of anti-collagen type 1 immune responses. Malaria parasites induce a pro-inflammatory host immune response and many of the symptoms of malaria are immune system-mediated. Therefore we have asked whether the immunomodulatory properties of ES-62 can down-regulate the severity of malaria infection in BALB/c mice infected with Plasmodium chabaudi. We have found that ES-62 has no significant effect on the course of P. chabaudi parasitaemia, and does not significantly affect any of the measures of malaria-induced pathology taken throughout infection.
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Affiliation(s)
- T J Lamb
- Division of Parasitology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
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157
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Elliott SR, Spurck TP, Dodin JM, Maier AG, Voss TS, Yosaatmadja F, Payne PD, McFadden GI, Cowman AF, Rogerson SJ, Schofield L, Brown GV. Inhibition of dendritic cell maturation by malaria is dose dependent and does not require Plasmodium falciparum erythrocyte membrane protein 1. Infect Immun 2007; 75:3621-32. [PMID: 17470539 PMCID: PMC1932960 DOI: 10.1128/iai.00095-07] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Red blood cells infected with Plasmodium falciparum (iRBCs) have been shown to modulate maturation of human monocyte-derived dendritic cells (DCs), interfering with their ability to activate T cells. Interaction between Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) and CD36 expressed by DCs is the proposed mechanism, but we show here that DC modulation does not require CD36 binding, PfEMP1, or contact between DCs and infected RBCs and depends on the iRBC dose. iRBCs expressing a PfEMP1 variant that binds chondroitin sulfate A (CSA) but not CD36 were phagocytosed, inhibited lipopolysaccharide (LPS)-induced phenotypic maturation and cytokine secretion, and abrogated the ability of DCs to stimulate allogeneic T-cell proliferation. CD36- and CSA-binding iRBCs showed comparable inhibition. P. falciparum lines rendered deficient in PfEMP1 expression by targeted gene knockout or knockdown also inhibited LPS-induced phenotypic maturation, and separation of DCs and iRBCs in transwells showed that inhibition was not contact dependent. Inhibition was observed at an iRBC:DC ratio of 100:1 but not at a ratio of 10:1. High doses of iRBCs were associated with apoptosis of DCs, which was not activation induced. Lower doses of iRBCs stimulated DC maturation sufficient to activate autologous T-cell proliferation. In conclusion, modulation of DC maturation by P. falciparum is dose dependent and does not require interaction between PfEMP1 and CD36. Inhibition and apoptosis of DCs by high-dose iRBCs may or may not be physiological. However, our observation that low-dose iRBCs initiate functional DC maturation warrants reevaluation and further investigation of DC interactions with blood-stage P. falciparum.
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Affiliation(s)
- Salenna R Elliott
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia.
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158
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Metenou S, Suguitan AL, Long C, Leke RGF, Taylor DW. Fetal immune responses to Plasmodium falciparum antigens in a malaria-endemic region of Cameroon. THE JOURNAL OF IMMUNOLOGY 2007; 178:2770-7. [PMID: 17312120 DOI: 10.4049/jimmunol.178.5.2770] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Plasmodium falciparum infection during pregnancy can lead to the transplacental passage of malarial Ags that are capable of inducing acquired immune responses in the fetus. Studies have identified cytokines produced by malaria-specific cord blood (CB) T cells, but information on fetal B cells is limited. Thus, CB mononuclear cells from 120 Cameroonian newborns were cultured for 7 days in vitro and supernatants were assessed by ELISA for Abs to an extract of malarial schizonts (MA), recombinant apical merozoite Ag 1 (AMA-1), the 42-kDa C-terminal region of merozoite surface protein 1 (MSP-1(42)), a B epitope of ring-infected erythrocyte surface Ag (RESA), and the dominant B epitope of the circumsporozoite protein (CSP). Only 12% of supernatants contained IgM to MA but 78% had IgG to one or more malarial Ags, with 53% having IgG to AMA-1, 38% to MSP-1(42), 3% to RESA, and 0% to CSP. The Abs to AMA-1 and MSP-1(42) were predominantly IgG1 and IgG3. CB mononuclear cells were also tested for the ability to secrete cytokines in response to MA and a pool of conserved MSP-1 T cell epitopes. Among the Ag-reactive samples, 39.3% produced only Th2-type cytokines, whereas 60.6% produced a combination of Th1- and Th2-type cytokines. Although a Th2 bias was observed, the in utero cytokine environment was adequate to support isotype switching to cytophilic IgGs, the isotypes that are protective in adults. Because many infants living in a low transmission area are born with malaria-specific B and T cells, the influence of in utero priming on neonatal immunity merits further investigation.
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Affiliation(s)
- Simon Metenou
- Department of Biology, Georgetown University, Washington, D. C. 20057, USA
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159
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Schleicher U, Liese J, Knippertz I, Kurzmann C, Hesse A, Heit A, Fischer JAA, Weiss S, Kalinke U, Kunz S, Bogdan C. NK cell activation in visceral leishmaniasis requires TLR9, myeloid DCs, and IL-12, but is independent of plasmacytoid DCs. ACTA ACUST UNITED AC 2007; 204:893-906. [PMID: 17389237 PMCID: PMC2118560 DOI: 10.1084/jem.20061293] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Natural killer (NK) cells are sentinel components of the innate response to pathogens, but the cell types, pathogen recognition receptors, and cytokines required for their activation in vivo are poorly defined. Here, we investigated the role of plasmacytoid dendritic cells (pDCs), myeloid DCs (mDCs), Toll-like receptors (TLRs), and of NK cell stimulatory cytokines for the induction of an NK cell response to the protozoan parasite Leishmania infantum. In vitro, pDCs did not endocytose Leishmania promastigotes but nevertheless released interferon (IFN)-alpha/beta and interleukin (IL)-12 in a TLR9-dependent manner. mDCs rapidly internalized Leishmania and, in the presence of TLR9, produced IL-12, but not IFN-alpha/beta. Depletion of pDCs did not impair the activation of NK cells in L. infantum-infected mice. In contrast, L. infantum-induced NK cell cytotoxicity and IFN-gamma production were abolished in mDC-depleted mice. The same phenotype was observed in TLR9(-/-) mice, which lacked IL-12 expression by mDCs, and in IL-12(-/-) mice, whereas IFN-alpha/beta receptor(-/-) mice showed only a minor reduction of NK cell IFN-gamma expression. This study provides the first direct evidence that mDCs are essential for eliciting NK cell cytotoxicity and IFN-gamma release in vivo and demonstrates that TLR9, mDCs, and IL-12 are functionally linked to the activation of NK cells in visceral leishmaniasis.
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MESH Headings
- Animals
- CD11c Antigen/metabolism
- Cell Differentiation
- DNA, Protozoan/genetics
- Dendritic Cells/cytology
- Dendritic Cells/immunology
- Dendritic Cells/metabolism
- Female
- Interferon-alpha/biosynthesis
- Interferon-beta/biosynthesis
- Interleukin-12/deficiency
- Interleukin-12/genetics
- Interleukin-12/immunology
- Killer Cells, Natural/cytology
- Killer Cells, Natural/immunology
- Leishmania donovani/genetics
- Leishmaniasis, Visceral/immunology
- Leishmaniasis, Visceral/metabolism
- Leishmaniasis, Visceral/parasitology
- Leishmaniasis, Visceral/pathology
- Lymphocyte Activation/immunology
- Mice
- Mice, Knockout
- Myeloid Cells/cytology
- Myeloid Cells/immunology
- Phenotype
- Receptor, Interferon alpha-beta/deficiency
- Receptor, Interferon alpha-beta/genetics
- Receptor, Interferon alpha-beta/metabolism
- Toll-Like Receptor 9/immunology
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Affiliation(s)
- Ulrike Schleicher
- Institute of Medical Microbiology and Hygiene, University of Freiburg, D-79104 Freiburg, Germany
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160
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Tetsutani K, To H, Torii M, Hisaeda H, Himeno K. Malaria parasite induces tryptophan-related immune suppression in mice. Parasitology 2007; 134:923-30. [PMID: 17316473 DOI: 10.1017/s0031182007002326] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Plasmodium spp. cause the worst parasitic diseases in humans and evade host immunity in complicated ways. Activated catabolism of tryptophan in dendritic cells is thought to suppress immunity, which is mediated by an inducible rate-limiting enzyme of tryptophan catabolism, indoleamine 2,3 dioxygenase (IDO), via both tryptophan depletion and production of toxic metabolites. In various infections, including malaria, IDO is known to be activated but its biological significance is unclear; therefore, we investigated whether malaria parasites induce IDO to suppress host immune responses. We found that enzymatic activity of IDO was elevated systematically in our mouse malaria model, and was abolished by in vivo IDO inhibition with 1-methyl tryptophan. Experimental infection with Plasmodium yoelii showed that IDO inhibition slightly suppressed parasite density in association with enhanced proliferation and IFN-gamma production by CD4+ T cells in response to malaria parasites. Our observations suggest that induction of IDO is one of the immune mechanisms of malaria parasites.
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Affiliation(s)
- K Tetsutani
- Kyushu University Graduate School of Medicine, Department of Parasitology, 3-1-1, Maidashi, Fukuoka, 812-0054, Japan.
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161
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Abstract
Malaria is an infectious disease that causes serious morbidity and mortality worldwide. The disease is associated with a variety of clinical syndromes ranging from asymptomatic to lethal infections involving anaemia, organ failure, pulmonary and cerebral disease. The molecular and cellular factors responsible for the differences in disease severity are poorly understood but parasite-specific immune responses are thought to play a critical role in pathogenesis. Dendritic cells have an essential role in linking innate and adaptive immune responses and here we review their role in the context of malaria.
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Affiliation(s)
- Michelle Wykes
- The Queensland Institute of Medical Research, The Bancroft Centre, 300 Herston Road, Brisbane, Qld 4006, Australia.
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162
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Parroche P, Lauw FN, Goutagny N, Latz E, Monks BG, Visintin A, Halmen KA, Lamphier M, Olivier M, Bartholomeu DC, Gazzinelli RT, Golenbock DT. Malaria hemozoin is immunologically inert but radically enhances innate responses by presenting malaria DNA to Toll-like receptor 9. Proc Natl Acad Sci U S A 2007; 104:1919-24. [PMID: 17261807 PMCID: PMC1794278 DOI: 10.1073/pnas.0608745104] [Citation(s) in RCA: 398] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Hemozoin (HZ) is an insoluble crystal formed in the food vacuole of malaria parasites. HZ has been reported to induce inflammation by directly engaging Toll-like receptor (TLR) 9, an endosomal receptor. "Synthetic" HZ (beta-hematin), typically generated from partially purified extracts of bovine hemin, is structurally identical to natural HZ. When HPLC-purified hemin was used to synthesize the crystal, beta-hematin had no inflammatory activity. In contrast, natural HZ from Plasmodium falciparum cultures was a potent TLR9 inducer. Natural HZ bound recombinant TLR9 ectodomain, but not TLR2. Both TLR9 stimulation and TLR9 binding of HZ were abolished by nuclease treatment. PCR analysis demonstrated that natural HZ is coated with malarial but not human DNA. Purified malarial DNA activated TLR9 but only when DNA was targeted directly to the endosome with a transfection reagent. Stimulatory quantities of natural HZ contain <1 microg of malarial DNA; its potency in activating immune responses was even greater than transfecting malarial DNA. Thus, although the malarial genome is extremely AT-rich, its DNA is highly proinflammatory, with the potential to induce cytokinemia and fever during disease. However, its activity depends on being bound to HZ, which we propose amplifies the biological responses to malaria DNA by targeting it to a TLR9(+) intracellular compartment.
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Affiliation(s)
- Peggy Parroche
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Fanny N. Lauw
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Nadege Goutagny
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Eicke Latz
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Brian G. Monks
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Alberto Visintin
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Kristen A. Halmen
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Marc Lamphier
- Eisai Research Institute, 4 Corporate Drive, Andover, MA 01810
| | - Martin Olivier
- Department of Microbiology/Immunology, McGill University, Montreal, Quebec, Canada H3A 2T8; and
| | - Daniella C. Bartholomeu
- Department of Biochemistry and Immunology and Department of Parasitology, Biological Sciences Institute, Federal University of Minas Gerais, 6627 Belo Horizonte, Brazil
| | - Ricardo T. Gazzinelli
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
- Centro de Pesquisas René Rachou, FIOCRUZ, 1715 Belo Horizonte, Brazil
- Department of Biochemistry and Immunology and Department of Parasitology, Biological Sciences Institute, Federal University of Minas Gerais, 6627 Belo Horizonte, Brazil
| | - Douglas T. Golenbock
- *Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605
- To whom correspondence should be addressed at:
Division of Infectious Diseases and Immunology, University of Massachusetts Medical School; LRB 308, 364 Plantation Street, Worcester, MA 01605. E-mail:
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163
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Abstract
Malaria, caused by the infection with parasites of the germs Plasmodium, is one of the three most important infectious diseases worldwide, along with tuberculosis and infection with human immunodeficiency virus. Natural killer (NK) cells are lymphocytes classically involved in the early defense against viral infections and intracytoplasmic bacterial infections and are also implicated during the course of tumor development and allogeneic transplantation. These cells display important cytotoxic activity and produce high levels of proinflammatory cytokines. In both mouse and human models of malaria, NK cells appear to be a major source of interferon-gamma during the early phase of infection. In humans, indirect signaling through monocytes/macrophages required to optimally stimulate NK cell activity. However, the in vivo functions of NK cells during malaria are still enigmatic, and many issues remain to be dissected, such as the molecular basis of the direct recognition of iRBCs by NK cells.
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Affiliation(s)
- Sophie Roetynck
- Centre d'Immunologie de Marseille-Luminy, Université de la Méditerranée, Marseille, France
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164
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Abstract
Innate immune response against Plasmodium falciparum (Pf), a causative agent of human malaria, is the result of several thousand years of co-evolution between the parasite and his host. An early IFN-gamma production during infection is associated with a better evolution of the disease. Natural killer (NK) cells are among the first cells in peripheral blood to produce IFN-gamma in response to Pf-infected erythrocytes (Pf-E). NK cells are found in blood, in secondary lymphoid organs as well as in peripheral non-lymphoid tissues. They participate in host innate responses that occur upon viral and intracytoplasmic bacterial infections, but also during the course of tumor development and allogeneic transplantation. These lymphocytes are not only important players of innate effector responses, but also participate in the initiation and development of adaptive immune responses. In addition, direct sensing of Pf infection by NK cells induces their production of the proinflammatory chemokine IL-8, suggesting a role for NK cells in the recruitment and the activation of other cells during malaria infection. Several other cell subsets are involved in the innate immune response to Pf. Dendritic cells, macrophages, gamma delta T cells, NKT cells are able to sense the presence of the parasite. Along this line, the presence of IL-12 is necessary to NK cell IFN-gamma production and a functional cooperation takes place between macrophages and NK cells in the context of this parasitic infection. In particular, IL-18 produced by macrophages is a key factor for this NK response. However, the molecular basis of Pf-E recognition by NK cells as well as the functional role of NK cell responses during the course of the disease remain to be adressed.
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Affiliation(s)
- Sophie Roetynck
- Centre d'Immunologie de Marseille-Luminy, Inserm-CNRS, Université de la Méditerranée, Parc Scientifique et Technologique de Luminy, Case 906, 13288 Marseille Cedex 09, France
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165
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Breitling LP, Fendel R, Mordmueller B, Adegnika AA, Kremsner PG, Luty AJF. Cord blood dendritic cell subsets in African newborns exposed to Plasmodium falciparum in utero. Infect Immun 2006; 74:5725-9. [PMID: 16988249 PMCID: PMC1594912 DOI: 10.1128/iai.00682-06] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Placental Plasmodium falciparum infection affects birth outcomes and sensitizes fetal lymphocytes to parasite antigens. We assessed the influence of maternal P. falciparum infection on fetal myeloid dendritic cells (mDC) and plasmacytoid dendritic cells (pDC), analyzing the cord blood of offspring of Gabonese mothers with different infection histories. Cord blood from newborns of mothers with malarial infection at delivery had significantly more mDC than that from nonexposed newborns (P = 0.028) but mDC and pDC HLA-DR expression was unrelated to maternal infection history. Independently of these findings, cord blood mDC and pDC numbers declined significantly as a function of increasing maternal age (P = 0.029 and P = 0.033, respectively). The inducible antigen-specific interleukin-10-producing regulatory-type T-cell population that we have previously detected in cord blood of newborns with prolonged in utero exposure to P. falciparum may directly reflect the altered DC numbers in such neonates, while the maintenance of cord blood DC HLA-DR expression contrasts with that of DC from P. falciparum malaria patients.
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Affiliation(s)
- Lutz P Breitling
- Medical Parasitology-268, Department of Medical Microbiology, MMB-NCMLS, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
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166
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Broen K, Brustoski K, Engelmann I, Luty AJF. Placental Plasmodium falciparum infection: causes and consequences of in utero sensitization to parasite antigens. Mol Biochem Parasitol 2006; 151:1-8. [PMID: 17081634 DOI: 10.1016/j.molbiopara.2006.10.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Accepted: 10/02/2006] [Indexed: 11/26/2022]
Abstract
Available evidence suggests that, in African populations, systemic blood-dwelling parasitoses of mothers are associated with enhanced susceptibility to infection of their offspring. Thus, children born to mothers with filariasis or schistosomiasis are infected earlier, and offspring of mothers with placental Plasmodium falciparum at delivery, commonly referred to as pregnancy-associated malaria or PAM, are themselves at higher risk of developing parasitaemia during infancy. Since foetal/neonatal antigen-presenting cells (APC) are either immature or provide insufficient costimulatory signals to T cells, thus favouring tolerance induction, it is commonly assumed that soluble parasite components [protein antigens], transferred transplacentally and inducing foetal immune tolerance, are largely, if not exclusively, responsible for these outcomes. Plasmodial asexual blood stage antigen-specific T cells are detectable in as many as two-thirds of all cord blood samples in malaria-endemic countries of sub-Saharan Africa, indicating that in utero sensitization may be a common phenomenon during pregnancy in these populations. Parasite antigen-specific T cell responses of neonates born to helminth-infected mothers display a highly skewed Th2-type cytokine pattern, with a prominent role for the regulatory cytokine interleukin (IL)-10. Similarly, the cord blood immune response of those born to mothers identified with on-going PAM is characterised by inducible parasite antigen-specific IL-10-producing regulatory T cells that can inhibit both APC HLA expression and Th1-type T cell responses. In contrast, plasmodial antigen-specific Th1-type responses, characterised by IFN-gamma production, predominate in cord blood of those born to mothers successfully treated for Pf malaria during gestation, suggesting that the duration and/or the nature of antigen exposure in utero governs the outcome with respect to neonatal immune responses. Aspects of APC function in the context of these differentially modulated responses, whether and how the latter translate into altered susceptibility to Pf infection during infancy, as well as the possible implications for vaccination in early life, are aspects that are discussed in this review.
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Affiliation(s)
- Kelly Broen
- Department of Medical Microbiology 268, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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167
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Urban BC, Cordery D, Shafi MJ, Bull PC, Newbold CI, Williams TN, Marsh K. The frequency of BDCA3-positive dendritic cells is increased in the peripheral circulation of Kenyan children with severe malaria. Infect Immun 2006; 74:6700-6. [PMID: 17000725 PMCID: PMC1698077 DOI: 10.1128/iai.00861-06] [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: 11/20/2022] Open
Abstract
The ability of Plasmodium falciparum-infected erythrocytes to adhere to host endothelial cells via receptor molecules such as ICAM-1 and CD36 is considered a hallmark for the development of severe malaria syndromes. These molecules are also expressed on leukocytes such as dendritic cells. Dendritic cells are antigen-presenting cells that are crucial for the initiation of adaptive immune responses. In many human diseases, their frequency and function is perturbed. We analyzed the frequency of peripheral blood dendritic cell subsets and the plasma concentrations of interleukin-10 (IL-10) and IL-12 in Kenyan children with severe malaria and during convalescence and related these parameters to the adhesion phenotype of the acute parasite isolates. The frequency of CD1c(+) dendritic cells in children with acute malaria was comparable to that in healthy controls, but the frequency of BDCA3(+) dendritic cells was significantly increased. Analysis of the adhesion phenotypes of parasite isolates revealed that adhesion to ICAM-1 was associated with the frequency of peripheral blood CD1c(+) dendritic cells, whereas the adhesion of infected erythrocytes to CD36 correlated with high concentrations of IL-10 and low concentrations of IL-12 in plasma.
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Affiliation(s)
- Britta C Urban
- Centre for Clinical Vaccinology and Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Old Road, Oxford OX3 7LJ, United Kingdom.
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168
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Abstract
Toll-like receptor 9 (TLR9) is specialized for the recognition of pathogenic nucleic acids. TLR9 is expressed in intracellular compartments where it responds specifically to pathogen DNA. Several factors contribute to the ability of TLR9 to discriminate between self and foreign DNA. Regulatory mechanisms of the innate and adaptive immune system exist that balance the immune responses mediated by TLR9. Short synthetic CpG oligodeoxynucleotides are used to induce controlled and directed TLR9-dependent stimulation and are effective immune modulators in preclinical and clinical studies. This review will summarize the interplay between TLR9-dependent opposing stimulatory and regulatory effects in innate and adaptive immunity.
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Affiliation(s)
- Jörg Vollmer
- Coley Pharmaceutical, GmbH, Langenfeld, Germany.
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169
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Guiducci C, Ott G, Chan JH, Damon E, Calacsan C, Matray T, Lee KD, Coffman RL, Barrat FJ. Properties regulating the nature of the plasmacytoid dendritic cell response to Toll-like receptor 9 activation. ACTA ACUST UNITED AC 2006; 203:1999-2008. [PMID: 16864658 PMCID: PMC2118381 DOI: 10.1084/jem.20060401] [Citation(s) in RCA: 291] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human plasmacytoid dendritic cells (PDCs) can produce interferon (IFN)-α and/or mature and participate in the adaptive immune response. Three classes of CpG oligonucleotide ligands for Toll-like receptor (TLR)9 can be distinguished by different sequence motifs and different abilities to stimulate IFN-α production and maturation of PDCs. We show that the nature of the PDC response is determined by the higher order structure and endosomal location of the CpG oligonucleotide. Activation of TLR9 by the multimeric CpG-A occurs in transferrin receptor (TfR)-positive endosomes and leads exclusively to IFN-α production, whereas monomeric CpG-B oligonucleotides localize to lysosome-associated membrane protein (LAMP)-1–positive endosomes and promote maturation of PDCs. However, CpG-B, when complexed into microparticles, localizes in TfR-positive endosomes and induces IFN-α from PDCs, whereas monomeric forms of CpG-A localize to LAMP-1–positive endosomes accompanied by the loss of IFN-α production and a gain in PDC maturation activity. CpG-C sequences, which induce both IFN-α and maturation of PDCs, are distributed in both type of endosomes. Encapsulation of CpG-C in liposomes stable above pH 5.75 completely abrogated the IFN-α response while increasing PDC maturation. This establishes that the primary determinant of TLR9 signaling is not valency but endosomal location and demonstrates a strict compartmentalization of the biological response to TLR9 activation in PDCs.
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170
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Minns LA, Menard LC, Foureau DM, Darche S, Ronet C, Mielcarz DW, Buzoni-Gatel D, Kasper LH. TLR9 is required for the gut-associated lymphoid tissue response following oral infection of Toxoplasma gondii. THE JOURNAL OF IMMUNOLOGY 2006; 176:7589-97. [PMID: 16751405 DOI: 10.4049/jimmunol.176.12.7589] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
TLRs expressed by a variety of cells, including epithelial cells, B cells, and dendritic cells, are important initiators of the immune response following stimulation with various microbial products. Several of the TLRs require the adaptor protein, MyD88, which is an important mediator for the immune response following Toxoplasma gondii infection. Previously, TLR9-mediated innate immune responses were predominantly associated with ligation of unmethylated bacterial CpG DNA. In this study, we show that TLR9 is required for the Th1-type inflammatory response that ensues following oral infection with T. gondii. After oral infection with T. gondii, susceptible wild-type (WT; C57BL/6) but not TLR9(-/-) (B6 background) mice develop a Th1-dependent acute lethal ileitis; TLR9(-/-) mice have higher parasite burdens than control WT mice, consistent with depressed IFN-gamma-dependent parasite killing. A reduction in the total T cell and IFN-gamma-producing T cell frequencies was observed in the lamina propria of the TLR9(-/-) parasite-infected mice. TLR9 and type I IFN production was observed by cells from infected intestines in WT mice. TLR9 expression by dendritic cell populations is essential for their expansion in the mesenteric lymph nodes of infected mice. Infection of chimeric mice deleted of TLR9 in either the hemopoietic or nonhemopoietic compartments demonstrated that TLR9 expression by cells from both compartments is important for efficient T cell responses to oral infection. These observations demonstrate that TLR9 mediates the innate response to oral parasite infection and is involved in the development of an effective Th1-type immune response.
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Affiliation(s)
- Laurie A Minns
- Department of Medicine, Dartmouth Medical School, Lebanon, NH 03756, USA
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171
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Sponaas AM, Cadman ET, Voisine C, Harrison V, Boonstra A, O'Garra A, Langhorne J. Malaria infection changes the ability of splenic dendritic cell populations to stimulate antigen-specific T cells. ACTA ACUST UNITED AC 2006; 203:1427-33. [PMID: 16754719 PMCID: PMC2118320 DOI: 10.1084/jem.20052450] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The capacity of splenic CD11c+ dendritic cell (DC) populations to present antigen (Ag) to T cells differs during malarial infection with Plasmodium chabaudi in mice. Both CD11c+CD8+ and CD8− DCs presented malarial peptides on their surface during infection. However, although both DC subsets expressing malaria peptides could induce interferon-γ production by CD4 T cells, only CD8− DCs isolated at the acute phase of infection stimulated Ag-specific T cell proliferation and interleukin (IL)-4 and -10 production from MSP1-specific T cell receptor for Ag transgenic T cells coincidental with our reported Th1 to Th2 switch at this stage in response to the pathogen. The timing of these distinct DC responses coincided with increased levels of apoptosis in the CD8+ population and an increase in the numbers of CD8− DCs in the spleen. Our data suggest that the switch in CD4 T cell responses observed in P. chabaudi–infected mice may be the result of the presentation by different DC populations modified by the malaria infection.
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Affiliation(s)
- Anne-Marit Sponaas
- Division of Parasitology and 2Division of Immunoregulation, National Institute for Medical Research, London NW7 1AA, United Kingdom
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172
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Blasius AL, Colonna M. Sampling and signaling in plasmacytoid dendritic cells: the potential roles of Siglec-H. Trends Immunol 2006; 27:255-60. [PMID: 16679063 DOI: 10.1016/j.it.2006.04.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 03/24/2006] [Accepted: 04/21/2006] [Indexed: 11/23/2022]
Abstract
Plasmacytoid dendritic cells (pDCs) detect viruses through toll-like receptor (TLR)7 and TLR9 and respond by secreting type I interferons (IFNs). Because TLR7 and TLR9 are present in endosomes, a mechanism is required to capture and deliver viruses to TLRs. A member of the sialic acid binding Ig-like lectin (Siglec) family, Siglec-H, has recently been identified as a specific surface marker for pDCs in mice. Siglec-H is endocytosed and can mediate the uptake of antigens for processing and presentation. Thus, Siglec-H might have a role in the capture of viruses or other pathogens for their delivery to intracellular TLRs. Paradoxically, Siglec-H also transmits intracellular signals through the associated adaptor DAP12, which reduces pDC responses to TLR ligands. In this review, we discuss models to explain the potential outcomes of Siglec-H engagement in the pDC secretion of type I IFN.
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Affiliation(s)
- Amanda L Blasius
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO 63110, USA
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173
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Millington OR, Di Lorenzo C, Phillips RS, Garside P, Brewer JM. Suppression of adaptive immunity to heterologous antigens during Plasmodium infection through hemozoin-induced failure of dendritic cell function. J Biol 2006; 5:5. [PMID: 16611373 PMCID: PMC1561486 DOI: 10.1186/jbiol34] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Revised: 12/16/2005] [Accepted: 03/02/2006] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Dendritic cells (DCs) are central to the initiation and regulation of the adaptive immune response during infection. Modulation of DC function may therefore allow evasion of the immune system by pathogens. Significant depression of the host's systemic immune response to both concurrent infections and heterologous vaccines has been observed during malaria infection, but the mechanisms underlying this immune hyporesponsiveness are controversial. RESULTS Here, we demonstrate that the blood stages of malaria infection induce a failure of DC function in vitro and in vivo, causing suboptimal activation of T cells involved in heterologous immune responses. This effect on T-cell activation can be transferred to uninfected recipients by DCs isolated from infected mice. Significantly, T cells activated by these DCs subsequently lack effector function, as demonstrated by a failure to migrate to lymphoid-organ follicles, resulting in an absence of B-cell responses to heterologous antigens. Fractionation studies show that hemozoin, rather than infected erythrocyte (red blood cell) membranes, reproduces the effect of intact infected red blood cells on DCs. Furthermore, hemozoin-containing DCs could be identified in T-cell areas of the spleen in vivo. CONCLUSION Plasmodium infection inhibits the induction of adaptive immunity to heterologous antigens by modulating DC function, providing a potential explanation for epidemiological studies linking endemic malaria with secondary infections and reduced vaccine efficacy.
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Affiliation(s)
- Owain R Millington
- Division of Immunology, Infection and Inflammation, University of Glasgow, Glasgow G11 6NT, UK
- Current address: Centre for Biophotonics, University of Strathclyde, Glasgow G4 0NR, UK
| | - Caterina Di Lorenzo
- Division of Immunology, Infection and Inflammation, University of Glasgow, Glasgow G11 6NT, UK
| | - R Stephen Phillips
- Division of Infection and Immunity, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK
| | - Paul Garside
- Division of Immunology, Infection and Inflammation, University of Glasgow, Glasgow G11 6NT, UK
- Current address: Centre for Biophotonics, University of Strathclyde, Glasgow G4 0NR, UK
| | - James M Brewer
- Division of Immunology, Infection and Inflammation, University of Glasgow, Glasgow G11 6NT, UK
- Current address: Centre for Biophotonics, University of Strathclyde, Glasgow G4 0NR, UK
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174
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Abstract
The capacity of malarial infection to suppress the patient's immune responses both to the parasite and to other antigens has long puzzled researchers. A prime suspect, the parasite-produced pigment hemozoin, has now been clearly shown to mediate immunosuppression by inhibiting dendritic cell activity.
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Affiliation(s)
- Britta C Urban
- Centre for Clinical Vaccinology and Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Old Road, Oxford, OX3 7LJ, UK.
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175
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Abstract
Microorganisms that invade a vertebrate host are initially recognized by the innate immune system through germline-encoded pattern-recognition receptors (PRRs). Several classes of PRRs, including Toll-like receptors and cytoplasmic receptors, recognize distinct microbial components and directly activate immune cells. Exposure of immune cells to the ligands of these receptors activates intracellular signaling cascades that rapidly induce the expression of a variety of overlapping and unique genes involved in the inflammatory and immune responses. New insights into innate immunity are changing the way we think about pathogenesis and the treatment of infectious diseases, allergy, and autoimmunity.
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Affiliation(s)
- Shizuo Akira
- Department of Host Defense, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
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176
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Ing R, Segura M, Thawani N, Tam M, Stevenson MM. Interaction of mouse dendritic cells and malaria-infected erythrocytes: uptake, maturation, and antigen presentation. THE JOURNAL OF IMMUNOLOGY 2006; 176:441-50. [PMID: 16365437 DOI: 10.4049/jimmunol.176.1.441] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Consistent with their seminal role in detecting infection, both mouse bone marrow-derived and splenic CD11c+ dendritic cells (DCs) exhibited higher levels of uptake of Plasmodium chabaudi-parasitized RBCs (pRBCs) than of noninfected RBCs (nRBCs) as determined by our newly developed flow cytometric technique using the dye CFSE to label RBCs before coculture with DCs. To confirm that expression of CFSE by CD11c+ cells following coculture with CFSE-labeled pRBCs represents internalization of pRBC by DCs, we showed colocalization of CFSE-labeled pRBCs and PE-labeled CD11c+ DCs by confocal fluorescence microscopy. Treatment of DCs with cytochalasin D significantly inhibited the uptake of pRBCs, demonstrating that uptake is an actin-dependent phagocytic process. The uptake of pRBCs by splenic CD11c+ DCs was significantly enhanced after infection in vivo and was associated with the induction of DC maturation, IL-12 production, and stimulation of CD4+ T cell proliferation and IFN-gamma production. These results suggest that DCs selectively phagocytose pRBCs and present pRBC-derived Ags to CD4+ T cells, thereby promoting development of protective Th1-dependent immune responses to blood-stage malaria infection.
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Affiliation(s)
- Rebecca Ing
- Centre for the Study of Host Resistance, Research Institute of the McGill University Health Centre, McGill University, Montréal, Québec, Canada
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177
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Rogers KA, Rogers AB, Leav BA, Sanchez A, Vannier E, Uematsu S, Akira S, Golenbock D, Ward HD. MyD88-dependent pathways mediate resistance to Cryptosporidium parvum infection in mice. Infect Immun 2006; 74:549-56. [PMID: 16369011 PMCID: PMC1346622 DOI: 10.1128/iai.74.1.549-556.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Cryptosporidium spp. cause diarrheal disease worldwide. Innate immune responses mediating resistance to this parasite are not completely understood. To determine whether MyD88-dependent pathways play a role in resistance to Cryptosporidium parvum, we compared the course of infection in MyD88(-/-) mice to that in their wild-type (WT) littermate controls. Three- to 4-week-old mice were infected with C. parvum, and infection was monitored by quantifying fecal oocyst shedding. Twelve days postinfection, the histology of the intestines was examined to quantify intestinal parasite burden and to determine if there were any pathological changes. Fecal oocyst shedding and intestinal parasite burden were significantly greater in MyD88(-/-) mice than in littermate controls. Nonetheless, both WT and MyD88(-/-) mice cleared the infection within 3 weeks. These results indicate that MyD88-dependent pathways are involved in mediating initial resistance to C. parvum. Since gamma interferon (IFN-gamma) is known to mediate resistance to C. parvum, we also studied infection in MyD88(-/-) mice and WT controls in which this cytokine was temporarily neutralized. Fecal oocyst shedding, as well as intestinal parasite burden, intestinal inflammation, and mortality, was significantly greater in MyD88(-/-) mice in which IFN-gamma was neutralized than in IFN-gamma-neutralized WT mice or in MyD88(-/-) mice in which this cytokine was active. These results suggest that MyD88 and IFN-gamma had an additive effect in conferring protection from C. parvum infection. While this study confirms the importance of IFN-gamma in conferring resistance to infection with C. parvum, it suggests that MyD88-mediated pathways also play a role in innate immunity to this parasite.
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MESH Headings
- Adaptor Proteins, Signal Transducing/deficiency
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/physiology
- Animals
- Antigens, Differentiation/genetics
- Antigens, Differentiation/physiology
- Cryptosporidiosis/immunology
- Cryptosporidiosis/metabolism
- Cryptosporidiosis/mortality
- Cryptosporidium parvum/immunology
- Enterocolitis/immunology
- Enterocolitis/metabolism
- Enterocolitis/mortality
- Enterocolitis/parasitology
- Female
- Immunity, Innate/genetics
- Interferon-gamma/antagonists & inhibitors
- Interferon-gamma/physiology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Myeloid Differentiation Factor 88
- Receptors, Immunologic/deficiency
- Receptors, Immunologic/genetics
- Receptors, Immunologic/physiology
- Signal Transduction/genetics
- Signal Transduction/immunology
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Affiliation(s)
- K A Rogers
- Division of Geographic Medicine and Infectious Diseases, Tufts-New England Medical Center, 750 Washington Street, Boston, MA 02111, USA
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178
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Chen XM, O'Hara SP, Nelson JB, Splinter PL, Small AJ, Tietz PS, Limper AH, LaRusso NF. Multiple TLRs are expressed in human cholangiocytes and mediate host epithelial defense responses to Cryptosporidium parvum via activation of NF-kappaB. THE JOURNAL OF IMMUNOLOGY 2006; 175:7447-56. [PMID: 16301652 DOI: 10.4049/jimmunol.175.11.7447] [Citation(s) in RCA: 158] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Infection of epithelial cells by Cryptosporidium parvum triggers a variety of host-cell innate and adaptive immune responses including release of cytokines/chemokines and up-regulation of antimicrobial peptides. The mechanisms that trigger these host-cell responses are unclear. Thus, we evaluated the role of TLRs in host-cell responses during C. parvum infection of cultured human biliary epithelia (i.e., cholangiocytes). We found that normal human cholangiocytes express all known TLRs. C. parvum infection of cultured cholangiocytes induces the selective recruitment of TLR2 and TLR4 to the infection sites. Activation of several downstream effectors of TLRs including IL-1R-associated kinase, p-38, and NF-kappaB was detected in infected cells. Transfection of cholangiocytes with dominant-negative mutants of TLR2 and TLR4, as well as the adaptor molecule myeloid differentiation protein 88 (MyD88), inhibited C. parvum-induced activation of IL-1R-associated kinase, p-38, and NF-kappaB. Short-interfering RNA to TLR2, TLR4, and MyD88 also blocked C. parvum-induced NF-kappaB activation. Moreover, C. parvum selectively up-regulated human beta-defensin-2 in directly infected cells, and inhibition of TLR2 and TLR4 signals or NF-kappaB activation were each associated with a reduction of C. parvum-induced human beta-defensin-2 expression. A significantly higher number of parasites were detected in cells transfected with a MyD88 dominant-negative mutant than in the control cells at 48-96 h after initial exposure to parasites, suggesting MyD88-deficient cells were more susceptible to infection. These findings demonstrate that cholangiocytes express a variety of TLRs, and suggest that TLR2 and TLR4 mediate cholangiocyte defense responses to C. parvum via activation of NF-kappaB.
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Affiliation(s)
- Xian-Ming Chen
- The Center for Basic Research in Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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179
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Nebl T, De Veer MJ, Schofield L. Stimulation of innate immune responses by malarial glycosylphosphatidylinositol via pattern recognition receptors. Parasitology 2006; 130 Suppl:S45-62. [PMID: 16281992 DOI: 10.1017/s0031182005008152] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The glycosylphosphatidylinositol (GPI) anchor of Plasmodium falciparum is thought to function as a critical toxin that contributes to severe malarial pathogenesis by eliciting the production of proinflammatory responses by the innate immune system of mammalian hosts. Analysis of the fine structure of P. falciparum GPI suggests a requirement for the presence of both core glycan and lipid moieties in the recognition and signalling of parasite glycolipids by host immune cells. It has been demonstrated that GPI anchors of various parasitic protozoa can mediate cellular immune responses via members of the Toll-like family of pattern recognition receptors (TLRs). Recent studies indicate that GPI anchors of P. falciparum and other protozoa are preferentially recognized by TLR-2, involving the MyD88-dependent activation of specific signalling pathways that mediate the production of proinflammatory cytokines and nitric oxide from host macrophages in vitro. However, the contribution of malaria GPI toxin to severe disease syndromes and the role of specific TLRs or other pattern recognition receptors in innate immunity in vivo is only just beginning to be characterized. A better understanding of the molecular mechanisms underlying severe malarial pathogenesis may yet lead to substantial new insights with important implications for the development of novel therapeutics for malaria treatment.
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Affiliation(s)
- T Nebl
- The Walter and Eliza Hall Institute of Medical Research, Victoria, Australia
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180
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Wilson NS, Behrens GMN, Lundie RJ, Smith CM, Waithman J, Young L, Forehan SP, Mount A, Steptoe RJ, Shortman KD, de Koning-Ward TF, Belz GT, Carbone FR, Crabb BS, Heath WR, Villadangos JA. Systemic activation of dendritic cells by Toll-like receptor ligands or malaria infection impairs cross-presentation and antiviral immunity. Nat Immunol 2006; 7:165-72. [PMID: 16415871 DOI: 10.1038/ni1300] [Citation(s) in RCA: 289] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Accepted: 12/09/2005] [Indexed: 01/07/2023]
Abstract
The mechanisms responsible for the immunosuppression associated with sepsis or some chronic blood infections remain poorly understood. Here we show that infection with a malaria parasite (Plasmodium berghei) or simple systemic exposure to bacterial or viral Toll-like receptor ligands inhibited cross-priming. Reduced cross-priming was a consequence of downregulation of cross-presentation by activated dendritic cells due to systemic activation that did not otherwise globally inhibit T cell proliferation. Although activated dendritic cells retained their capacity to present viral antigens via the endogenous major histocompatibility complex class I processing pathway, antiviral responses were greatly impaired in mice exposed to Toll-like receptor ligands. This is consistent with a key function for cross-presentation in antiviral immunity and helps explain the immunosuppressive effects of systemic infection. Moreover, inhibition of cross-presentation was overcome by injection of dendritic cells bearing antigen, which provides a new strategy for generating immunity during immunosuppressive blood infections.
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Affiliation(s)
- Nicholas S Wilson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia
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181
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Abstract
Dendritic cells (DCs) are important both in amplifying the innate immune response and in initiating adaptive immunity and shaping the type of T helper (Th) response. Although the role of DCs in immune responses to many intracellular pathogens has been delineated and research is underway to identify the mechanisms involved, relatively little is known concerning the role of DCs in immunity to malaria. In this review, we provide an overview and summary of previous and current studies aimed to investigate the role of DCs as antigen presenting cells (APCs). In addition, the role of DCs in inducing innate and adaptive immunity to blood-stage malaria is discussed and, where information is available, the mechanisms involved are presented. Data from studies in humans infected with Plasmodium falciparum, the major human parasite responsible for the high morbidity and mortality associated with malaria throughout many regions of the developing world, as well as data from experimental mouse models are presented. Overall, the data from these studies are conflicting. The possible reasons for these differences, including the use of different parasite species and parasite strains in the mouse studies, are discussed. Nevertheless, together the data have important implications for development of an effective malaria vaccine since the selection of appropriate Plasmodium antigens and/or adjuvants, targeting innate immune responses involving DCs, may provide optimal protection against malaria. It is hoped that this review promotes more investigation among malariologists and immunologists alike on DCs and malaria.
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Affiliation(s)
- M M Stevenson
- Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada.
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182
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Urban BC, Ing R, Stevenson MM. Early interactions between blood-stage plasmodium parasites and the immune system. Curr Top Microbiol Immunol 2005; 297:25-70. [PMID: 16265902 DOI: 10.1007/3-540-29967-x_2] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Accumulating evidence provides strong support for the importance of innate immunity in shaping the subsequent adaptive immune response to blood-stage Plasmodium parasites, the causative agents of malaria. Early interactions between blood-stage parasites and cells of the innate immune system, including dendritic cells, monocytes/macrophages, natural killer (NK) cells, NKT cells, and gamma6 T cells, are important in the timely control of parasite replication and in the subsequent elimination and resolution of the infection. The major role of innate immunity appears to be the production of immunoregulatory cytokines, such as interleukin (IL)-12 and interferon (IFN)-gamma, which are critical for the development of type 1 immune responses involving CD4+ Thl cells, B cells, and effector cells which mediate cell-mediated and antibody-dependent adaptive immune responses. In addition, it is likely that cells of the innate immune system, especially dendritic cells, serve as antigen-presenting cells. Here, we review recent data from rodent models of blood-stage malaria and from human studies, and outline the early interactions of infected red blood cells with the innate immune system. We compare and contrast the results derived from studies in infected laboratory mice and humans. These host species are sufficiently different with respect to the identity of the infecting Plasmodium species, the resulting pathologies, and immune responses, particularly where the innate immune response is concerned. The implications of these findings for the development of an effective and safe malaria vaccine are also discussed.
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Affiliation(s)
- B C Urban
- Centre for Clinical Vaccinology and Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University, Churchill Hospital, Old Road, Oxford, UK.
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183
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Ndungu FM, Urban BC, Marsh K, Langhorne J. Regulation of immune response by Plasmodium-infected red blood cells. Parasite Immunol 2005; 27:373-84. [PMID: 16179031 DOI: 10.1111/j.1365-3024.2005.00771.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
During the asexual blood stage infection of the human malaria parasite, Plasmodium falciparum, parasite-derived proteins are inserted onto the surface of the host red blood cell membrane. These proteins are highly variable and were originally thought only to mediate antigenic variation, and sequestration of parasites from peripheral circulation, thus enabling immune evasion. Recent studies have revealed that PfEMP-1 and other molecules on the P. falciparum-infected red blood cell (PfRBC) activate and modulate the immune response. In this review, we discuss how PfRBCs interact with antigen-presenting cells (APCs) and other cells of the immune system, and how such interactions could modulate the host response to Plasmodium infections.
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Affiliation(s)
- F M Ndungu
- National Institute for Medical Research, Division of Parasitology, The Ridgeway, Mill Hill, London, NW7 1AA, UK
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184
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Mockenhaupt FP, Cramer JP, Hamann L, Stegemann MS, Eckert J, Oh NR, Otchwemah RN, Dietz E, Ehrhardt S, Schröder NWJ, Bienzle U, Schumann RR. Toll-like receptor (TLR) polymorphisms in African children: Common TLR-4 variants predispose to severe malaria. Proc Natl Acad Sci U S A 2005; 103:177-82. [PMID: 16371473 PMCID: PMC1324982 DOI: 10.1073/pnas.0506803102] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genetic host factors play a substantial role in susceptibility to and severity of malaria, which continues to cause at least one million deaths per year. Recently, members of the toll-like receptor (TLR) family have been shown to be involved in recognition of the etiologic organism Plasmodium falciparum: The glycosylphosphatidylinositol anchor induces signaling in host cells via TLR-2 and -4, whereas hemozoin-induced immune activation involves TLR-9. Binding of microbial ligands to the respective TLRs triggers the release of proinflammatory cytokines via the TLR/IL-1 receptor (TIR) domain and may contribute to the host response in malaria, including cytokine induction and fever. In a case-control study among 870 Ghanaian children, we examined the influence of TLR-2, -4, and -9 polymorphisms in susceptibility to severe malaria. TLR-2 variants common in Caucasians and Asians were completely absent. However, we found a rare previously undescribed mutation (Leu658Pro), which impairs signaling via TLR-2. We failed to detect any polymorphisms within the TLR-9 Toll/IL-1 receptor domain. Two frequent TLR-9 promoter polymorphisms did not show a clear association with malaria severity. In contrast, the TLR-4-Asp299Gly variant occurred at a high rate of 17.6% in healthy controls and was even more frequent in severe malaria patients (24.1%, P < 0.05). Likewise, TLR-4-Thr399Ile was seen in 2.4% of healthy children and in 6.2% of patients (P = 0.02). TLR-4-Asp299Gly and TLR-4-Thr399Ile conferred 1.5- and 2.6-fold increased risks of severe malaria, respectively. These findings suggest TLR4-mediated responses to malaria in vivo and TLR-4 polymorphisms to be associated with disease manifestation.
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Affiliation(s)
- Frank P Mockenhaupt
- Institute of Tropical Medicine Berlin, Charité-Universitätsmedizin Berlin, Spandauer Damm 130, 14050 Berlin, Germany
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185
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Born WK, Reardon CL, O'Brien RL. The function of gammadelta T cells in innate immunity. Curr Opin Immunol 2005; 18:31-8. [PMID: 16337364 DOI: 10.1016/j.coi.2005.11.007] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Accepted: 11/24/2005] [Indexed: 02/06/2023]
Abstract
Many researchers believe that gammadelta T lymphocytes belong somewhere 'in-between' the innate and adaptive immune systems. Recent studies strongly emphasize the innate features and functions of these cells, including the use of germline elements of the T cell receptor for ligand recognition, segregation into functionally specialized cell populations in correlation with T cell receptor variable gene or protein expression, interactions with cells of the innate system at many levels and, the latest addition, the ability to present antigen. Thus, at present, much evidence suggests that gammadelta T cells function in an innate manner, although they are arguably the most complex and advanced cellular representatives of the innate immune system.
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Affiliation(s)
- Willi K Born
- Department of Immunology, at National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA.
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186
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Korbel DS, Newman KC, Almeida CR, Davis DM, Riley EM. Heterogeneous Human NK Cell Responses toPlasmodium falciparum-Infected Erythrocytes. THE JOURNAL OF IMMUNOLOGY 2005; 175:7466-73. [PMID: 16301654 DOI: 10.4049/jimmunol.175.11.7466] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Human NK cells can respond rapidly to Plasmodium falciparum-infected RBC (iRBC) to produce IFN-gamma. In this study, we have examined the heterogeneity of this response among malaria-naive blood donors. Cells from all donors become partially activated (up-regulating CD69, perforin, and granzyme) upon exposure to iRBC but cells from only a subset of donors become fully activated (additionally up-regulating CD25, IFN-gamma, and surface expression of lysosomal-associated membrane protein 1 (LAMP-1)). Although both CD56dim and CD56bright NK cell populations can express IFN-gamma in response to iRBC, CD25 and LAMP-1 are up-regulated only by CD56dim NK cells and CD69 is up-regulated to a greater extent in this subset; by contrast, perforin and granzyme A are preferentially up-regulated by CD56bright NK cells. NK cells expressing IFN-gamma in response to iRBC always coexpress CD69 and CD25 but rarely LAMP-1, suggesting that individual NK cells respond to iRBC either by IFN-gamma production or cytotoxicity. Furthermore, physical contact with iRBC can, in a proportion of donors, lead to NK cell cytoskeletal reorganization suggestive of functional interactions between the cells. These observations imply that individuals may vary in their ability to mount an innate immune response to malaria infection with obvious implications for disease resistance or susceptibility.
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MESH Headings
- Animals
- Antigens, CD/biosynthesis
- Antigens, CD/immunology
- Antigens, Differentiation, T-Lymphocyte/biosynthesis
- Antigens, Differentiation, T-Lymphocyte/immunology
- Blood Donors
- CD5 Antigens/biosynthesis
- CD5 Antigens/immunology
- Cell Communication/immunology
- Cells, Cultured
- Erythrocytes/microbiology
- Flow Cytometry
- Humans
- Interferon-gamma/biosynthesis
- Interferon-gamma/immunology
- Killer Cells, Natural/immunology
- Killer Cells, Natural/microbiology
- Lectins, C-Type
- Lymphocyte Activation/immunology
- Lysosomal-Associated Membrane Protein 1/biosynthesis
- Lysosomal-Associated Membrane Protein 1/immunology
- Membrane Glycoproteins/biosynthesis
- Membrane Glycoproteins/immunology
- Microscopy, Confocal
- Perforin
- Plasmodium falciparum/immunology
- Pore Forming Cytotoxic Proteins
- Receptors, Interleukin-2/biosynthesis
- Receptors, Interleukin-2/immunology
- Up-Regulation
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Affiliation(s)
- Daniel S Korbel
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
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187
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Baratin M, Roetynck S, Lépolard C, Falk C, Sawadogo S, Uematsu S, Akira S, Ryffel B, Tiraby JG, Alexopoulou L, Kirschning CJ, Gysin J, Vivier E, Ugolini S. Natural killer cell and macrophage cooperation in MyD88-dependent innate responses to Plasmodium falciparum. Proc Natl Acad Sci U S A 2005; 102:14747-52. [PMID: 16203971 PMCID: PMC1253601 DOI: 10.1073/pnas.0507355102] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
IFN-gamma secretion by natural killer (NK) cells is pivotal to several tumor and viral immune responses, during which NK and dendritic cells cooperation is required. We show here that macrophages are mandatory for NK cell IFN-gamma secretion in response to erythrocytes infected with Plasmodium falciparum (Pf), a causative agent of human malaria. In addition, direct sensing of Pf infection by NK cells induces their production of the proinflammatory chemokine CXCL8, without triggering their granule-mediated cytolytic programs. Despite their reported role in Pf recognition, Toll-like receptor (TLR) 2, TLR9, and TLR11 are individually dispensable for NK cell activation induced by Pf-infected erythrocytes. However, IL-18R expression on NK cells, IL-18 production by macrophages, and MyD88 on both cell types are essential components of this previously undescribed pathway of NK cell activation in response to a parasite infection.
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Affiliation(s)
- Myriam Baratin
- Centre d'Immunologie de Marseille-Luminy, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Université delaMéditerranée, 13288 Marseille, France
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188
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Watson JL, McKay DM. The immunophysiological impact of bacterial CpG DNA on the gut. Clin Chim Acta 2005; 364:1-11. [PMID: 16153626 DOI: 10.1016/j.cca.2005.05.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Revised: 05/12/2005] [Accepted: 05/16/2005] [Indexed: 12/21/2022]
Abstract
Both the endogenous commensal flora and a dysregulated mucosal immune response have been implicated as contributing to the pathogenesis of human intestinal disease. Unmethylated cytosine-guanine (CpG)-containing DNA, the ligand for Toll-like receptor 9 (TLR9), is a recently recognized microbial product with immunostimulatory and immunoregulatory effects. TLR9 is expressed by many cell types located in the intestine, including epithelial cells and classical immune cells. The physiological impact of the juxtaposition of these factors (bacterial DNA and responsive cells) in the gut therefore bears consideration. Here we discuss studies that examine the interaction between CpG DNA and the intestine, focusing on activation of epithelial cells, administration of CpG-containing oligonucleotides as therapy for experimental inflammatory enteropathies, and the role of CpG DNA in mediating the beneficial effects of bacterial probiotics.
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Affiliation(s)
- James L Watson
- Intestinal Disease Research Programme, Department of Pathology and Molecular Medicine, McMaster University, HSC-3N5C, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5
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189
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Henault M, Lee LN, Evans GF, Zuckerman SH. The human Burkitt lymphoma cell line Namalwa represents a homogenous cell system characterized by high levels of Toll-like receptor 9 and activation by CpG oligonucleotides. J Immunol Methods 2005; 300:93-9. [PMID: 15894327 DOI: 10.1016/j.jim.2005.02.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2004] [Revised: 02/25/2005] [Accepted: 02/28/2005] [Indexed: 11/21/2022]
Abstract
Human B cells and plasmacytoid dendritic cells constitutively express Toll-like receptor (TLR)9 and respond to TLR9 ligands, as evidenced by nuclear factor kappa B translocation and cytokine secretion. However, TLR9 expression on B lymphocytes appears to be dependent upon both the state of activation and differentiation of the B cell population. In the current study, TLR9 mRNA expression was evaluated in transformed human B cell lines and correlated with their response to CpG. Among the B cell lines, the Burkitt lymphoma-derived Namalwa line had the highest level of TLR9 expression, 20-fold greater than spleen. Following incubation with CpG oligonucleotide, Namalwa cells secreted increased amounts of TNF, IL-6, and IL-10 and expressed the costimulator molecules CD40, CD80, and CD86. These functional responses to TLR9 activation occurred with similar EC(50) values in the 30- to 60-nM range. These results suggest that the Namalwa Burkitt lymphoma line may serve as a useful cell-based assay for the detection of novel TLR9 agonists as well as a model to further explore the regulation of TLR9 expression and signaling.
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Affiliation(s)
- Martin Henault
- Division of Bone and Inflammation Research, Lilly Research Laboratories, Indianapolis, IN, USA
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190
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Engwerda CR, Good MF. Interactions between malaria parasites and the host immune system. Curr Opin Immunol 2005; 17:381-7. [PMID: 15950450 DOI: 10.1016/j.coi.2005.05.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Accepted: 05/26/2005] [Indexed: 10/25/2022]
Abstract
Malaria remains one of the greatest impediments to development in many tropical regions of the world. Understanding host immune responses to malaria parasites is crucial for the effective design and implementation of new vaccines and drugs. Recent research has seen the identification of the first pattern recognition receptor (TLR9) on dendritic cells for a defined product of malaria infection (hemozoin). In addition, progress has been made in understanding the role of dendritic cell subsets in malaria, and how they promote specific components of the host immune response. Potentially important advances in vaccine design have also been made by inserting a Plasmodium sporozoite epitope into the yellow fever vaccine 17D, as well as using a whole, live-attenuated sporozoite vaccine.
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Affiliation(s)
- Christian R Engwerda
- Queensland Institute of Medical Research, 300 Herston Road, Herston, Queensland 4006, Australia
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191
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Spirig R, Peduzzi E, Patarroyo ME, Pluschke G, Daubenberger CA. Structural and functional characterisation of the Toll like receptor 9 of Aotus nancymaae, a non-human primate model for malaria vaccine development. Immunogenetics 2005; 57:283-8. [PMID: 15900500 DOI: 10.1007/s00251-005-0789-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2004] [Revised: 02/08/2005] [Indexed: 11/24/2022]
Abstract
In the absence of suitable rodent animal models for Plasmodium falciparum malaria, the efficacy testing of asexual blood-stage vaccine candidates in Aotus nancymaae represents a tool to select between different formulations before conducting expensive human clinical trials. CpG oligonucleotides (ODN) specifically promote the production of pro-inflammatory and Th1-type cytokines and they enhance the immunogenicity of co-administered antigens. Toll like receptor 9 (TLR-9) binds directly and sequence-specifically to single-stranded un-methylated CpG-DNA mediating the biological effects of CpG ODN. We cloned and functionally characterised the TLR-9 cDNA of A. nancymaae. The cDNA encompassed 3,099 bp predicted to code for 1,032 amino acid residues. Results of homology searches to human TLR-9 suggested that the receptor is 93 and 94% identical at the nucleotide and amino acid sequence levels, respectively. Stimulation of splenocytes of A. nancymaae with CpG ODN resulted in proliferative responses in all animals analysed. FACS analysis of cultures incubated with CpG ODN 2006 indicated that the B cell marker CD20 was up-regulated consistent with B cell activation. The high level of sequence conservation of Aona-TLR-9 reinforces the suitability of A. nancymaae as animal model for malaria subunit vaccine development.
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Affiliation(s)
- Rolf Spirig
- Department of Medical Parasitology and Biology of Infection, Molecular Immunology, Swiss Tropical Institute, Socinstrasse 57, 4002 Basel, Switzerland
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192
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Abstract
There are several malaria vaccine candidates at various stages of development. Many of these target blood stages of Plasmodium falciparum. The spleen is a key site for removal of parasitized red blood cells, generation of immunity and production of new red blood cells during malaria. This article describes how all of these processes are modified following infection, and suggests that until we fully understand how these processes function and are modulated by infection, appropriate malaria vaccine design and delivery will be extremely difficult to achieve.
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193
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Abstract
For a long time, the family of type I interferons (IFN-alpha/beta) has received little attention outside the fields of virology and tumor immunology. In recent years, IFN-alpha/beta regained the interest of immunologists, due to the phenotypic and functional characterization of IFN-alpha/beta-producing cells, the definition of novel immunomodulatory functions and signaling pathways of IFN-alpha/beta, and the observation that IFN-alpha/beta not only exerts antiviral effects but is also relevant for the pathogenesis or control of certain bacterial and protozoan infections. This review summarizes the current knowledge on the production and function of IFN-alpha/beta during non-viral infections in vitro and in vivo.
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Affiliation(s)
- Christian Bogdan
- Institute of Medical Microbiology and Hygiene, Department of Microbiology and Hygiene, University of Freiburg, Freiburg, Germany.
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194
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Bolad A, Farouk SE, Israelsson E, Dolo A, Doumbo OK, Nebié I, Maiga B, Kouriba B, Luoni G, Sirima BS, Modiano D, Berzins K, Troye-Blomberg M. Distinct Interethnic Differences in Immunoglobulin G Class/Subclass and Immunoglobulin M Antibody Responses to Malaria Antigens but not in Immunoglobulin G Responses to Nonmalarial Antigens in Sympatric Tribes Living in West Africa. Scand J Immunol 2005; 61:380-6. [PMID: 15853923 DOI: 10.1111/j.1365-3083.2005.01587.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The well-established relative resistance to malaria observed in the Fulani as compared with other sympatric tribes in West Africa has been attributed to their higher levels of serum immunoglobulin (Ig) G antibodies to malarial antigens. In this study, we confirm and extend the previous findings by analyses of the levels of IgM, IgG and IgG subclasses of anti-malarial antibodies in asymptomatic individuals of different sympatric tribes in Burkina Faso (Fulani/Mossi) and Mali (Fulani/Dogon). The Fulani showed significantly higher median concentrations of anti-malarial IgG and IgM antibodies than the sympatric tribes at both locations. Although the overall subclass pattern of antibodies did not differ between the tribes, with IgG1 and IgG3 as dominant, the Fulani showed consistently significantly higher levels of these subclasses as compared with those of the non-Fulani individuals. No significant differences were seen in the levels of total IgG between the tribes, but the Fulani showed significantly higher levels of total IgM than their neighbours in both countries. While the antibody levels to some nonmalarial antigens showed the same pattern of differences seen for antibody levels to malaria antigens, no significant such differences were seen with antibodies to other nonmalarial antigens. In conclusion, our results show that the Fulani in two different countries show higher levels of anti-malarial antibodies than sympatric tribes, and this appears not to be a reflection of a general hyper-reactivity in the Fulani.
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MESH Headings
- Adolescent
- Adult
- Aged
- Animals
- Antibodies, Protozoan/biosynthesis
- Antibodies, Protozoan/blood
- Antigens/immunology
- Antigens/pharmacology
- Antigens, Bacterial/blood
- Antigens, Bacterial/immunology
- Antigens, Bacterial/pharmacology
- Antigens, Protozoan/immunology
- Antigens, Protozoan/pharmacology
- Antigens, Viral/blood
- Antigens, Viral/immunology
- Antigens, Viral/pharmacology
- Burkina Faso
- Child
- Enzyme-Linked Immunosorbent Assay
- Humans
- Immunoglobulin G/biosynthesis
- Immunoglobulin G/blood
- Immunoglobulin M/biosynthesis
- Immunoglobulin M/blood
- Malaria, Falciparum/blood
- Malaria, Falciparum/ethnology
- Malaria, Falciparum/immunology
- Malaria, Falciparum/parasitology
- Mali
- Middle Aged
- Plasmodium falciparum/immunology
- Population Groups
- Rural Population
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Affiliation(s)
- A Bolad
- Department of Immunology, Wenner-Gren Institute, Stockholm University, S-10691 Stockholm, Sweden
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195
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Coban C, Ishii KJ, Kawai T, Hemmi H, Sato S, Uematsu S, Yamamoto M, Takeuchi O, Itagaki S, Kumar N, Horii T, Akira S. Toll-like receptor 9 mediates innate immune activation by the malaria pigment hemozoin. ACTA ACUST UNITED AC 2005; 201:19-25. [PMID: 15630134 PMCID: PMC2212757 DOI: 10.1084/jem.20041836] [Citation(s) in RCA: 431] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Malaria parasites within red blood cells digest host hemoglobin into a hydrophobic heme polymer, known as hemozoin (HZ), which is subsequently released into the blood stream and then captured by and concentrated in the reticulo-endothelial system. Accumulating evidence suggests that HZ is immunologically active, but the molecular mechanism(s) through which HZ modulates the innate immune system has not been elucidated. This work demonstrates that HZ purified from Plasmodium falciparum is a novel non-DNA ligand for Toll-like receptor (TLR)9. HZ activated innate immune responses in vivo and in vitro, resulting in the production of cytokines, chemokines, and up-regulation of costimulatory molecules. Such responses were severely impaired in TLR9−/− and myeloid differentiation factor 88 (MyD88)−/−, but not in TLR2, TLR4, TLR7, or Toll/interleukin 1 receptor domain–containing adaptor-inducing interferon β−/− mice. Synthetic HZ, which is free of the other contaminants, also activated innate immune responses in vivo in a TLR9-dependent manner. Chloroquine (CQ), an antimalarial drug, abrogated HZ-induced cytokine production. These data suggest that TLR9-mediated, MyD88-dependent, and CQ-sensitive innate immune activation by HZ may play an important role in malaria parasite–host interactions.
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Affiliation(s)
- Cevayir Coban
- Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency (JST), Osaka, Japan
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196
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Abstract
Endemic Burkitt's lymphoma is the most common childhood cancer in equatorial Africa. Two ubiquitous human pathogens are thought to be responsible for the aetiology of this disease: Epstein-Barr virus and Plasmodium falciparum malaria. New data suggest how these two pathogens might interact to result in disease and provide insights into the emerging concepts of polymicrobial disease pathogenesis.
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Affiliation(s)
- Rosemary Rochford
- Department of Microbiology and Immunology, SUNY Upstate Medical University, Syracuse, New York, USA.
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197
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Langhorne J, Albano FR, Hensmann M, Sanni L, Cadman E, Voisine C, Sponaas AM. Dendritic cells, pro-inflammatory responses, and antigen presentation in a rodent malaria infection. Immunol Rev 2005; 201:35-47. [PMID: 15361231 DOI: 10.1111/j.0105-2896.2004.00182.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
An infection of mice with Plasmodium chabaudi is characterized by a rapid and marked inflammatory response with a rapid but regulated production of interleukin-12 (IL-12), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma). Recent studies have shown that dendritic cells (DCs) are activated in vivo in the spleen, are able to process and present malaria antigens during infection, and may provide a source of cytokines that contribute to polarization of the CD4 T-cell response. P. chabaudi-infected erythrocytes are phagocytosed by DCs, and peptides of malaria proteins are presented on major histocompatibility complex (MHC) class II. The complex disulfide-bonded structure of some malaria proteins can impede their processing in DCs, which may affect the magnitude of the CD4 T-cell response and influence T-helper 1 (Th1) or Th2 polarization. DCs exhibit a wide range of responses to parasite-infected erythrocytes depending on their source, their maturational state, and the Plasmodium species or strain. P. chabaudi-infected erythrocytes stimulate an increase in the expression of costimulatory molecules and MHC class II on mouse bone marrow-derived DCs, and they are able to induce the production of pro-inflammatory cytokines such as IL-12, TNF-alpha, and IL-6, thus enhancing the Th1 response of naïve T cells. IFN-gamma and TNF-alpha play a role in both protective immunity and the pathology of the infection, and the inflammatory disease may be regulated by IL-10 and transforming growth factor-beta. It will therefore be important to elucidate the host and parasite molecules that are involved in activation or suppression of the DCs and to understand the interplay between these opposing forces on the host response in vivo during a malaria infection.
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Affiliation(s)
- Jean Langhorne
- Division of Parasitology, National Institute for Medical Research, London, UK.
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198
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McKenna K, Beignon AS, Bhardwaj N. Plasmacytoid dendritic cells: linking innate and adaptive immunity. J Virol 2005; 79:17-27. [PMID: 15596797 PMCID: PMC538703 DOI: 10.1128/jvi.79.1.17-27.2005] [Citation(s) in RCA: 259] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- Kelli McKenna
- Department of Pathology, NYU Cancer Institute, The New York University School of Medicine, New York, New York 10016, USA
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Smith PL, Lombardi G, Foster GR. Type I interferons and the innate immune response--more than just antiviral cytokines. Mol Immunol 2005; 42:869-77. [PMID: 15829276 DOI: 10.1016/j.molimm.2004.11.008] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The role of type I interferon (referred to as IFN in this review) in early antiviral immunity is well known. More recently IFN has been shown to be a potent regulator of adaptive immunity. It is now becoming clear that a broad range of viruses, bacteria and even parasites express ligands capable of stimulating a growing number of signalling pathways that results in, often subtype specific, induction of IFN. Of particular interest are the signalling pathways associated with the Toll-like receptors. This family of receptors, each able to induce signals in response to a variety of ligands, initiates the pro-inflammatory response. They also contain members that have the capacity to induce IFN, making use of, and perhaps promoting the evolution of its pleiotropic responses. Greater knowledge of the events that result in induction of IFN is necessary in understanding the specificity of expression of an increasingly complex and important aspect of our immune system. This may reveal to us further therapeutic opportunities, either in the use of IFN or in the manipulation of their expression. This review details the established knowledge and recent advances made in understanding how and under what circumstances the IFNs are expressed, starting with brief overviews of IFN and Toll-like receptors before following the molecular processes from induction of IFN, activation of the JAK-STAT pathway and finally the expression of interferon stimulated genes and their functions.
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Affiliation(s)
- Peter L Smith
- Hepatobiliary Group, Centre for Adult and Paediatric Gastroenterology, Institute of Cell and Molecular Science, Queen Mary's School of Medicine and Dentistry, Barts and The London, UK.
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Khan AQ, Chen Q, Wu ZQ, Paton JC, Snapper CM. Both innate immunity and type 1 humoral immunity to Streptococcus pneumoniae are mediated by MyD88 but differ in their relative levels of dependence on toll-like receptor 2. Infect Immun 2005; 73:298-307. [PMID: 15618166 PMCID: PMC538967 DOI: 10.1128/iai.73.1.298-307.2005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Little is known regarding the role of Toll-like receptors (TLRs) in regulating protein- and polysaccharide-specific immunoglobulin (Ig) isotype production in response to an in vivo challenge with an extracellular bacterium. In this report we demonstrate that MyD88(-/-), but not TLR2(-/-), mice are markedly defective in their induction of multiple splenic proinflammatory cytokine- and chemokine-specific mRNAs after intraperitoneal (i.p.) challenge with heat-killed Streptococcus pneumoniae capsular type 14 (S. pneumoniae type 14). This is correlated with analogous responses in splenic cytokine protein release in vitro following addition of S. pneumoniae type 14. Consistent with these data, naive MyD88(-/-), but not TLR2(-/-), mice are more sensitive to killing following i.p. challenge with live S. pneumoniae type 14, relative to responses in wild-type mice. However, prior immunization of MyD88(-/-) mice with heat-killed S. pneumoniae type 14 protects against an otherwise-lethal challenge with live S. pneumoniae type 14. Surprisingly, both MyD88(-/-) and TLR2(-/-) mice exhibit striking and equivalent defects in elicitation of type 1 IgG isotypes (IgG3, IgG2b, and IgG2a), but not the type 2 IgG isotype, IgG1, specific for several protein and polysaccharide antigens, in response to i.p. challenge with heat-killed S. pneumoniae type 14. Of note, the type 1 IgG isotype titers specific for pneumococcal surface protein A are reduced in MyD88(-/-) mice but not TLR2(-/-) mice. These data suggest that distinct TLRs may differentially regulate innate versus adaptive humoral immunity to intact S. pneumoniae and are the first to implicate a role for TLR2 in shaping an in vivo type 1 IgG humoral immune response to a gram-positive extracellular bacterium.
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Affiliation(s)
- Abdul Q Khan
- Department of Pathology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA
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