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Neuroimmune Responses in a New Experimental Animal Model of Cerebral Aspergillosis. mBio 2022; 13:e0225422. [PMID: 36040029 PMCID: PMC9600342 DOI: 10.1128/mbio.02254-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Exposure of immunosuppressed individuals to the opportunistic fungal pathogen Aspergillus fumigatus may result in invasive pulmonary aspergillosis (IPA), which can lead to the development of cerebral aspergillosis (CA), a highly lethal infection localized in the central nervous system (CNS). There are no experimental models of CA that effectively mimic human disease, resulting in a considerable knowledge gap regarding mechanisms of neurological pathogenicity and neuroimmune responses during infection. In this report, immunosuppressed mice (via acute, high-dose corticosteroid administration) challenged with A. fumigatus resting conidia intranasally, followed a day later by a 70-fold lower inoculum of pre-swollen conidia intravenously (IN + IV + steroid), demonstrated increased weight loss, signs of severe clinical disease, increased fungal burden in the brain, and significant reduction in survival compared to immunosuppressed mice challenged intranasally only (IN + steroid) or non-immunosuppressed mice challenged both intranasally and intravenously (IN + IV). The IN + IV + steroid group demonstrated significant decreases in monocytes, eosinophils, dendritic cells (DCs), and invasive natural killer T (iNKT) cells, but not neutrophils or γδ T cells, in the brain compared to the IN + IV group. Likewise, the IN + IV + steroid group had significantly lower levels of interleukin (IL)-1β, IL-6, IL-17A, CC motif chemokine ligand 3 (CCL3), CXC chemokine ligand 10 (CXCL10), and vascular endothelial growth factor (VEGF) in the brain compared to the IN + IV group. IN + IV + steroid was superior to both IN + IV + chemotherapy (cytarabine + daunorubicin) and IN + IV + neutropenia for the development of CA. In conclusion, we have developed a well-defined, physiologically relevant model of disseminated CA in corticosteroid-induced immunosuppressed mice with a primary pulmonary infection. This model will serve to advance understanding of disease mechanisms, identify immunopathogenic processes, and help define the protective neuroinflammatory response to CA. IMPORTANCE Invasive fungal infections (IFIs) result in significant mortality in immunosuppressed individuals. Of these, invasive pulmonary aspergillosis (IPA), caused by the opportunistic mold Aspergillus fumigatus, is the most lethal. Lethality in IPA is due to two main factors: destruction of the lung leading to compromised pulmonary function, and dissemination of the organism to extrapulmonary organs. Of these, the CNS is the most common site of dissemination. However, very little is known regarding the pathogenesis of or immune response during cerebral aspergillosis, which is directly due to the lack of an animal model that incorporates immunosuppression, lung infection, and consistent dissemination to the CNS/brain. In this report, we have developed a new experimental animal model of CA which includes the above parameters and characterized the neuroimmune response. We further compared this disseminated CA model to two additional immunosuppressive strategies. Overall, this model of disseminated CA following IPA in an immunosuppressed host provides a novel platform for studying the efficacy of antifungal drugs and immunotherapies for improving disease outcomes.
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Dutta O, Espinosa V, Wang K, Avina S, Rivera A. Dectin-1 Promotes Type I and III Interferon Expression to Support Optimal Antifungal Immunity in the Lung. Front Cell Infect Microbiol 2020; 10:321. [PMID: 32733815 PMCID: PMC7360811 DOI: 10.3389/fcimb.2020.00321] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 05/26/2020] [Indexed: 12/18/2022] Open
Abstract
Pulmonary infections with Aspergillus fumigatus (Af) are a significant cause of invasive fungal disease and lead to high morbidity and mortality in diverse populations throughout the world. Currently available antifungal drugs are often ineffective, thus contributing to unacceptably high mortality rates in patients suffering from invasive fungal infections. The use of cytokines as adjunctive immune therapies holds the promise of significantly improving patient outcomes in the future. In recent studies, we identified an essential role for type I and III interferons as regulators of optimal antifungal responses by pulmonary neutrophils during infection with Af. Although various membrane and cytosolic nucleic acid sensors are known to regulate interferon production in response to viruses, the pathways that regulate the production of these cytokines during fungal infection remain uncovered. In the current study, we demonstrate that dectin-1-mediated recognition of β-glucan on the cell wall of the clinically relevant fungal pathogen Aspergillus fumigatus promotes the activation of a protective cascade of type I and III interferon expression. We further demonstrate that exogenous administration of type I and III interferons can rescue inadequate antifungal responses in dectin-1−/− mice, suggesting the potential therapeutic benefit of these cytokines as activators of antifungal defense in the context of innate defects.
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Affiliation(s)
- Orchi Dutta
- Graduate School of Biomedical Sciences, Rutgers Biomedical and Health Sciences, Newark, NJ, United States.,Center for Immunity and Inflammation, Rutgers Biomedical and Health Sciences, Newark, NJ, United States
| | - Vanessa Espinosa
- Center for Immunity and Inflammation, Rutgers Biomedical and Health Sciences, Newark, NJ, United States
| | - Keyi Wang
- Graduate School of Biomedical Sciences, Rutgers Biomedical and Health Sciences, Newark, NJ, United States.,Center for Immunity and Inflammation, Rutgers Biomedical and Health Sciences, Newark, NJ, United States
| | - Samantha Avina
- Graduate School of Biomedical Sciences, Rutgers Biomedical and Health Sciences, Newark, NJ, United States.,Center for Immunity and Inflammation, Rutgers Biomedical and Health Sciences, Newark, NJ, United States
| | - Amariliz Rivera
- Department of Pediatrics, Center for Immunity and Inflammation, Rutgers Biomedical and Health Sciences, Newark, NJ, United States
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Złotko K, Wiater A, Waśko A, Pleszczyńska M, Paduch R, Jaroszuk-Ściseł J, Bieganowski A. A Report on Fungal (1→3)-α-d-glucans: Properties, Functions and Application. Molecules 2019; 24:E3972. [PMID: 31684030 PMCID: PMC6864487 DOI: 10.3390/molecules24213972] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 10/30/2019] [Accepted: 10/31/2019] [Indexed: 12/13/2022] Open
Abstract
The cell walls of fungi are composed of glycoproteins, chitin, and α- and β-glucans. Although there are many reports on β-glucans, α-glucan polysaccharides are not yet fully understood. This review characterizes the physicochemical properties and functions of (1→3)-α-d-glucans. Particular attention has been paid to practical application and the effect of glucans in various respects, taking into account unfavourable effects and potential use. The role of α-glucans in plant infection has been proven, and collected facts have confirmed the characteristics of Aspergillus fumigatus infection associated with the presence of glucan in fungal cell wall. Like β-glucans, there are now evidence that α-glucans can also stimulate the immune system. Moreover, α-d-glucans have the ability to induce mutanases and can thus decompose plaque.
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Affiliation(s)
- Katarzyna Złotko
- Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland.
| | - Adrian Wiater
- Department of Industrial and Environmental Microbiology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
| | - Adam Waśko
- Department of Biotechnology, Human Nutrition and Food Commodity Science, University of Life Sciences in Lublin, Skromna 8, 20-704 Lublin, Poland.
| | - Małgorzata Pleszczyńska
- Department of Industrial and Environmental Microbiology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
| | - Roman Paduch
- Department of Virology and Immunology, Maria Curie-Skłodowska University, ul. Akademicka 19, 20-033 Lublin, Poland.
- Department of General Ophthalmology, Medical University, Chmielna 1, 20-079 Lublin, Poland.
| | - Jolanta Jaroszuk-Ściseł
- Department of Industrial and Environmental Microbiology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
| | - Andrzej Bieganowski
- Institute of Agrophysics, Polish Academy of Sciences, Doświadczalna 4, 20-290 Lublin, Poland.
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4
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Aharoni-Kats L, Zelinger E, Chen S, Yarden O. Altering Neurospora crassa MOB2A exposes its functions in development and affects its interaction with the NDR kinase COT1. Mol Microbiol 2018; 108:641-660. [PMID: 29600559 DOI: 10.1111/mmi.13954] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/15/2018] [Indexed: 12/30/2022]
Abstract
The Neurospora crassa Mps One Binder (MOB) proteins MOB2A and MOB2B physically interact with the Nuclear Dbf2 Related (NDR) kinase COT1 and have been shown to have overlapping functions in various aspects of asexual development. Here, we identified two N. crassa MOB2A residues, Tyr117 and Tyr119, which are potentially phosphorylated. Using phosphomimetic mob-2a mutants we have been able to establish that apart from their previously described roles, MOB2A/B are involved in additional developmental processes. Enhanced conidial germination, accompanied by conidial agglutination, in the phosphomimetic mutants indicated that MOB2A is a negative regulator of germination. Thick-section imaging of perithecia revealed slow maturation and a lack of asci alignment in the mutant strains demonstrating a role for MOB2A in sexual development. We demonstrate that even though MOB2A and MOB2B have some overlapping functions, MOB2B cannot compensate for the roles MOB2A has in conidiation and germination. Altering Tyr residues 117 and 119 impaired the physical interactions between MOB2A and COT1, most likely contributing to some of the observed effects. As cot-1 and the phosphomimetic mutants share an extragenic suppressor (gul-1), we concluded that at least some of the effects imposed by altering Tyr117 and Tyr119 are mediated by the NDR kinase.
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Affiliation(s)
- Liran Aharoni-Kats
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610000, Israel
| | - Einat Zelinger
- Centre for Scientific Imaging, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610000, Israel
| | - She Chen
- Proteomics Centre, The National Institute of Biological Sciences, Beijing 102206, China
| | - Oded Yarden
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 7610000, Israel
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5
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Maldonado S, Fitzgerald-Bocarsly P. Antifungal Activity of Plasmacytoid Dendritic Cells and the Impact of Chronic HIV Infection. Front Immunol 2017; 8:1705. [PMID: 29255464 PMCID: PMC5723005 DOI: 10.3389/fimmu.2017.01705] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 11/20/2017] [Indexed: 01/10/2023] Open
Abstract
Due to the effectiveness of combined antiretroviral therapy, people living with HIV can control viral replication and live longer lifespans than ever. However, HIV-positive individuals still face challenges to their health and well-being, including dysregulation of the immune system resulting from years of chronic immune activation, as well as opportunistic infections from pathogenic fungi. This review focuses on one of the key players in HIV immunology, the plasmacytoid dendritic cell (pDC), which links the innate and adaptive immune response and is notable for being the body’s most potent producer of type-I interferons (IFNs). During chronic HIV infection, the pDC compartment is greatly dysregulated, experiencing a substantial depletion in number and compromise in function. This immune dysregulation may leave patients further susceptible to opportunistic infections. This is especially important when considering a new role for pDCs currently emerging in the literature: in addition to their role in antiviral immunity, recent studies suggest that pDCs also play an important role in antifungal immunity. Supporting this new role, pDCs express C-type lectin receptors including dectin-1, dectin-2, dectin-3, and mannose receptor, and toll-like receptors-4 and -9 that are involved in recognition, signaling, and response to a wide variety of fungal pathogens, including Aspergillus fumigatus, Cryptococcus neoformans, Candida albicans, and Pneumocystis jirovecii. Accordingly, pDCs have been demonstrated to recognize and respond to certain pathogenic fungi, measured via activation, cytokine production, and fungistatic activity in vitro, while in vivo mouse models indicated a strikingly vital role for pDCs in survival against pulmonary Aspergillus challenge. Here, we discuss the role of the pDC compartment and the dysregulation it undergoes during chronic HIV infection, as well as what is known so far about the role and mechanisms of pDC antifungal activity.
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Affiliation(s)
- Samuel Maldonado
- Rutgers School of Graduate Studies, Newark, NJ, United States.,Department of Pathology and Laboratory Medicine, New Jersey Medical School, Newark, NJ, United States
| | - Patricia Fitzgerald-Bocarsly
- Rutgers School of Graduate Studies, Newark, NJ, United States.,Department of Pathology and Laboratory Medicine, New Jersey Medical School, Newark, NJ, United States
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6
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Sprenkeler EGG, Gresnigt MS, van de Veerdonk FL. LC3-associated phagocytosis: a crucial mechanism for antifungal host defence against Aspergillus fumigatus. Cell Microbiol 2016; 18:1208-16. [PMID: 27185357 DOI: 10.1111/cmi.12616] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 05/11/2016] [Accepted: 05/12/2016] [Indexed: 02/06/2023]
Abstract
LC3-associated phagocytosis (LAP) is a non-canonical autophagy pathway involved in the maturation of single-membrane phagosomes and subsequent killing of ingested pathogens by phagocytes. This pathway is initiated following recognition of pathogens by pattern recognition receptors and leads to the recruitment of LC3 into the phagosomal membrane. This form of phagocytosis is utilized for the antifungal host defence and is required for an efficient fungal killing. Here, we provide an overview of the LAP pathway and review the role of LAP in anti-Aspergillus host defence, as well as mechanisms induced by Aspergillus that modulate LAP to promote its survival in the host.
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Affiliation(s)
- Evelien G G Sprenkeler
- Department of Internal Medicine, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.,Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands
| | - Mark S Gresnigt
- Department of Internal Medicine, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.,Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands
| | - Frank L van de Veerdonk
- Department of Internal Medicine, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands.,Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands
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7
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Ghamrawi S, Gastebois A, Zykwinska A, Vandeputte P, Marot A, Mabilleau G, Cuenot S, Bouchara JP. A Multifaceted Study of Scedosporium boydii Cell Wall Changes during Germination and Identification of GPI-Anchored Proteins. PLoS One 2015; 10:e0128680. [PMID: 26038837 PMCID: PMC4454578 DOI: 10.1371/journal.pone.0128680] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 04/29/2015] [Indexed: 12/02/2022] Open
Abstract
Scedosporium boydii is a pathogenic filamentous fungus that causes a wide range of human infections, notably respiratory infections in patients with cystic fibrosis. The development of new therapeutic strategies targeting S. boydii necessitates a better understanding of the physiology of this fungus and the identification of new molecular targets. In this work, we studied the conidium-to-germ tube transition using a variety of techniques including scanning and transmission electron microscopy, atomic force microscopy, two-phase partitioning, microelectrophoresis and cationized ferritin labeling, chemical force spectroscopy, lectin labeling, and nanoLC-MS/MS for cell wall GPI-anchored protein analysis. We demonstrated that the cell wall undergoes structural changes with germination accompanied with a lower hydrophobicity, electrostatic charge and binding capacity to cationized ferritin. Changes during germination also included a higher accessibility of some cell wall polysaccharides to lectins and less CH3/CH3 interactions (hydrophobic adhesion forces mainly due to glycoproteins). We also extracted and identified 20 GPI-anchored proteins from the cell wall of S. boydii, among which one was detected only in the conidial wall extract and 12 only in the mycelial wall extract. The identified sequences belonged to protein families involved in virulence in other fungi like Gelp/Gasp, Crhp, Bglp/Bgtp families and a superoxide dismutase. These results highlighted the cell wall remodeling during germination in S. boydii with the identification of a substantial number of cell wall GPI-anchored conidial or hyphal specific proteins, which provides a basis to investigate the role of these molecules in the host-pathogen interaction and fungal virulence.
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Affiliation(s)
- Sarah Ghamrawi
- L'UNAM Université, Université d'Angers, Groupe d'Etude des Interactions Hôte-Pathogène, EA 3142, Angers, France
- * E-mail:
| | - Amandine Gastebois
- L'UNAM Université, Université d'Angers, Groupe d'Etude des Interactions Hôte-Pathogène, EA 3142, Angers, France
| | - Agata Zykwinska
- L'UNAM Université, Université de Nantes, Institut des Matériaux Jean Rouxel, Nantes, France
| | - Patrick Vandeputte
- L'UNAM Université, Université d'Angers, Groupe d'Etude des Interactions Hôte-Pathogène, EA 3142, Angers, France
- Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire, Angers, France
| | - Agnès Marot
- L'UNAM Université, Université d'Angers, Groupe d'Etude des Interactions Hôte-Pathogène, EA 3142, Angers, France
| | - Guillaume Mabilleau
- L'UNAM Université, Service Commun d'Imageries et Analyses microscopiques, Angers, France
| | - Stéphane Cuenot
- L'UNAM Université, Université de Nantes, Institut des Matériaux Jean Rouxel, Nantes, France
| | - Jean-Philippe Bouchara
- L'UNAM Université, Université d'Angers, Groupe d'Etude des Interactions Hôte-Pathogène, EA 3142, Angers, France
- Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire, Angers, France
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8
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Lass-Flörl C, Roilides E, Löffler J, Wilflingseder D, Romani L. Minireview: host defence in invasive aspergillosis. Mycoses 2013; 56:403-13. [PMID: 23406508 DOI: 10.1111/myc.12052] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Aspergillus is a saprophytic fungus, which mainly becomes pathogenic in immunosuppressed hosts. A failure of host defences results in a diverse set of illnesses, ranging from chronic colonisation, aspergilloma, invasive disease and hypersensitivity. A key concept in immune responses to Aspergillus species is that host susceptibility determines the morphological form, antigenic structure and physical location of the fungus. Traditionally, innate immunity has been considered as a first line of defence and activates adaptive immune mechanisms by the provision of specific signals; innate and adaptive immune responses are intimately linked. The T-helper cell (TH 1) response is associated with increased production of inflammatory cytokines IFN-γ, IL-2 and IL-12 and stimulation of antifungal effector cells. Alternatively, TH 2-type responses are associated with suppression of antifungal effector cell activity, decreased production of IFN-γ and increased concentrations of IL-4 and IL-10, which promote humoral responses to Aspergillus. The host's defensive capacity is defined by the sum of resistance and tolerance. Resistance displays the ability to limit fungal burden and elimination of the pathogen, and tolerance means the ability to limit host damage caused by immune response.
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Affiliation(s)
- Cornelia Lass-Flörl
- Division of Hygiene and Medical Microbiology, Innsbruck Medical University, Innsbruck, Austria.
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9
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Priegnitz BE, Wargenau A, Brandt U, Rohde M, Dietrich S, Kwade A, Krull R, Fleißner A. The role of initial spore adhesion in pellet and biofilm formation in Aspergillus niger. Fungal Genet Biol 2012; 49:30-8. [DOI: 10.1016/j.fgb.2011.12.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Revised: 10/05/2011] [Accepted: 12/05/2011] [Indexed: 11/30/2022]
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10
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Upadhyay SK, Gautam P, Pandit H, Singh Y, Basir SF, Madan T. Identification of fibrinogen-binding proteins of Aspergillus fumigatus using proteomic approach. Mycopathologia 2011; 173:73-82. [PMID: 21870122 DOI: 10.1007/s11046-011-9465-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Accepted: 08/11/2011] [Indexed: 11/28/2022]
Abstract
Aspergillus fumigatus, the main etiological agent for various forms of human aspergillosis, gets access to the respiratory system of human host by inhalation of airborne conidia. These conidia possibly adhere to extracellular matrix (ECM) proteins. Among the ECM proteins involved in adherence, fibrinogen is thought to be crucial. Here, we studied whether A. fumigatus three-week culture filtrate (3wcf) proteins promote binding of A. fumigatus to ECM proteins and promote fungal growth. We observed that incubation of ECM with 3wcf proteins led to dose- and time-dependent increase in adherence of conidia to the ECM. In order to identify the catalogue of fibrinogen-binding A. fumigatus proteins, we carried out fibrinogen affinity blotting using two-dimensional gel electrophoresed 3wcf proteins. A total of 15 fibrinogen-binding protein spots corresponding to 7 unique proteins were identified in 3wcf using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF-TOF). Among these, 4 proteins, namely, beta-glucosidase, alpha-mannosidase, pectate lyase A and oryzin precursor were predicted to have cell wall or extracellular localization, whereas amidase family protein and two hypothetical proteins did not display the signal sequence. This study reports seven novel fibrinogen-binding proteins of A. fumigatus, some of which could be further explored for targeting the adhesion phenomenon as antifungal strategy.
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Affiliation(s)
- Santosh Kumar Upadhyay
- Institute of Genomics and Integrative Biology, Council for Scientific and Industrial Research, Delhi, India
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11
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Wargenau A, Kwade A. Determination of adhesion between single Aspergillus niger spores in aqueous solutions using an atomic force microscope. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:11071-11076. [PMID: 20387816 DOI: 10.1021/la100653c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The interaction force between single cells in contact is of high interest in various interdisciplinary fields of biotechnology, for instance, in cultivation or biofilm formation. A method for the determination of adhesion forces between two single Aspergillus niger spores in different aqueous solutions was established in this study. Adhesion force distributions were determined at three different sodium chloride concentrations and two different pH values using an atomic force microscope (AFM). It was pointed out that adhesion data can be described by log-normal density functions, of which corresponding parameters have been estimated. Using the knowledge of distribution shape, the influence of the environmental condition on the mean values of adhesion force could be studied quantitatively. The highest value of 0.95 nN was observed at pH 2.5 and an ionic strength of 0.5 mol L(-1). Decreasing the ionic strength to 0.05 mol L(-1) decreases the adhesion force mean for about 25%. Increasing the pH value to pH 5 at a sodium chloride concentration of 0.154 mol L(-1) entails a decrease of adhesion from 0.88 to 0.56 nN. These results qualitatively agree with the absolute value of the expected surface potential of Aspergillus niger spores, which is much higher at pH 5 and should take more effect at lower concentrations of counterions.
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Affiliation(s)
- Andreas Wargenau
- Institut für Partikeltechnik, Technische Universität Braunschweig, Volkmaroder Strasse 5, D-38104 Braunschweig, Germany.
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12
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Fontaine T, Beauvais A, Loussert C, Thevenard B, Fulgsang CC, Ohno N, Clavaud C, Prevost MC, Latgé JP. Cell wall alpha1-3glucans induce the aggregation of germinating conidia of Aspergillus fumigatus. Fungal Genet Biol 2010; 47:707-12. [PMID: 20447463 DOI: 10.1016/j.fgb.2010.04.006] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 04/23/2010] [Accepted: 04/27/2010] [Indexed: 11/16/2022]
Abstract
The germination of Aspergillus fumigatus conidia can be divided into four stages: breaking of dormancy, isotropic swelling, establishment of cell polarity, and formation of a germ tube. Swelling of conidia is associated in liquid medium with a multi-cellular aggregation that produced large clumps of conidia. Conidial aggregation can be specifically prevented by the addition of alpha1-3glucanase. Swollen conidia specifically adhere to insoluble alpha1-3glucan chains. Electron microscopy studies showed that cell wall alpha1-3glucan chains became exposed at the cell surface during the swelling. These results demonstrate that cell wall alpha1-3glucans play an essential role in the aggregation between swollen conidia. Experiments with alpha1-3glucan coated latex beads show that alpha1-3glucan chains interacted between them without the requirement of any other cell wall component suggesting that biophysical properties of alpha1-3glucans are solely responsible for conidial aggregation.
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Affiliation(s)
- Thierry Fontaine
- Unité des Aspergillus, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris cedex 15, France.
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Abstract
All humans are continuously exposed to inhaled Aspergillus conidia, yet healthy hosts clear the organism without developing disease and without the development of antibody- or cell-mediated acquired immunity to this organism. This suggests that for most healthy humans, innate immunity is sufficient to clear the organism. A failure of these defenses results in a uniquely diverse set of illnesses caused by Aspergillus species, which includes diseases caused by the colonization of the respiratory tract, invasive infection, and hypersensitivity. A key concept in immune responses to Aspergillus species is that the susceptibilities of the host determine the morphological form, antigenic structure, and physical location of the fungus. In this review, we summarize the current literature on the multiple layers of innate defenses against Aspergillus species that dictate the outcome of this host-microbe interaction.
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14
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Melanin is an essential component for the integrity of the cell wall of Aspergillus fumigatus conidia. BMC Microbiol 2009; 9:177. [PMID: 19703288 PMCID: PMC2740851 DOI: 10.1186/1471-2180-9-177] [Citation(s) in RCA: 175] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 08/24/2009] [Indexed: 11/13/2022] Open
Abstract
Background Aspergillus fumigatus is the most common agent of invasive aspergillosis, a feared complication in severely immunocompromised patients. Despite the recent commercialisation of new antifungal drugs, the prognosis for this infection remains uncertain. Thus, there is a real need to discover new targets for therapy. Particular attention has been paid to the biochemical composition and organisation of the fungal cell wall, because it mediates the host-fungus interplay. Conidia, which are responsible for infections, have melanin as one of the cell wall components. Melanin has been established as an important virulence factor, protecting the fungus against the host's immune defences. We suggested that it might also have an indirect role in virulence, because it is required for correct assembly of the cell wall layers of the conidia. Results We used three A. fumigatus isolates which grew as white or brown powdery colonies, to demonstrate the role of melanin. Firstly, sequencing the genes responsible for biosynthesis of melanin (ALB1, AYG1, ARP1, ARP2, ABR1 and ABR2) showed point mutations (missense mutation, deletion or insertion) in the ALB1 gene for pigmentless isolates or in ARP2 for the brownish isolate. The isolates were then shown by scanning electron microscopy to produce numerous, typical conidial heads, except that the conidia were smooth-walled, as previously observed for laboratory mutants with mutations in the PKSP/ALB1 gene. Flow cytometry showed an increase in the fibronectin binding capacity of conidia from mutant isolates, together with a marked decrease in the binding of laminin to the conidial surface. A marked decrease in the electronegative charge of the conidia and cell surface hydrophobicity was also seen by microelectrophoresis and two-phase partitioning, respectively. Ultrastructural studies of mutant isolates detected considerable changes in the organisation of the conidial wall, with the loss of the outermost electron dense layer responsible for the ornamentations seen on the conidial surface in wild-type strains. Finally, analysis of the conidial surface of mutant isolates by atomic force microscopy demonstrated the absence of the outer cell wall rodlet layer which is composed of hydrophobins. Conclusion These results suggest that, in addition to a protective role against the host's immune defences, melanin is also a structural component of the conidial wall that is required for correct assembly of the cell wall layers and the expression at the conidial surface of adhesins and other virulence factors.
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Toyotome T, Watanabe A, Iwasaki A, Kamei K. [Strategy of Aspergillus fumigatus to evade attacks from host--projectile weapons and armor]. NIHON ISHINKIN GAKKAI ZASSHI = JAPANESE JOURNAL OF MEDICAL MYCOLOGY 2009; 50:139-45. [PMID: 19654445 DOI: 10.3314/jjmm.50.139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Humans are continually inhaling environmental fungi. When the host immune system is competent, the inhaled fungi are cleared away from the lung by host defense mechanisms. But in immunocompromised individuals, the environmental fungi (e.g., Aspergillus fumigatus) sometimes cause infection. Pathogenic fungi possess various mechanisms to invade the host. A. fumigatus is no exception in possessing several virulence factors and defense mechanisms against host immune attack.One of the virulence factors is secondary metabolite. A. fumigatus produces a variety of secondary metabolites, and the fungal products in culture supernatant have a strong apoptosis-inducing activity to macrophages and alveolar epithelial cells. These data suggest that A. fumigatus is equipped with special projectile weapons for destroying host physical barriers and immunological barriers in lung.The fungal cell wall is an easy target for the host to recognize the pathogen. One of the fungal cell wall components, beta- (1,3) -glucan, is a major fungal PAMP (pathogen-associated molecular pattern), which is recognized by one of the pattern recognition receptors, dectin-1. The interaction induces activation of transcription factors and production of proinflammatory cytokines in the host cell. However, beta-glucan of A. fumigatus is strongly exposed to the surface only during the "swollen-conidia" phase. In the hyphal phase, the fungus is covered with "armor", i.e., other cell wall components to minimize the exposure of the beta-glucan structure. These findings suggest that A. fumigatus evades the recognition and the attack from host by masking beta-glucan. A. fumigatus has clever mechanisms to defend itself and to attack the host immune system.
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Affiliation(s)
- Takahito Toyotome
- Division of Fungal Infection, Medical Mycology Research Center, Chiba University, Chiba, Japan
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Ejzykowicz DE, Cunha MM, Rozental S, Solis NV, Gravelat FN, Sheppard DC, Filler SG. The Aspergillus fumigatus transcription factor Ace2 governs pigment production, conidiation and virulence. Mol Microbiol 2009; 72:155-69. [PMID: 19220748 PMCID: PMC2690528 DOI: 10.1111/j.1365-2958.2009.06631.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Aspergillus fumigatus causes serious and frequently fatal infections in immunocompromised patients. To investigate the regulation of virulence of this fungus, we constructed and analysed an A. fumigatus mutant that lacked the transcription factor Ace2, which influences virulence in other fungi. The Deltaace2 mutant had dysmorphic conidiophores, reduced conidia production and abnormal conidial cell wall architecture. This mutant produced an orange pigment when grown on solid media, although its conidia had normal pigmentation. Conidia of the Deltaace2 mutant were larger and had accelerated germination. The resulting germlings were resistant to hydrogen peroxide, but not other stressors. Non-neutropenic mice that were immunosuppressed with cortisone acetate and infected with the Deltaace2 mutant had accelerated mortality, greater pulmonary fungal burden, and increased pulmonary inflammatory responses compared with mice infected with the wild-type or Deltaace2::ace2-complemented strains. The Deltaace2 mutant had reduced ppoC, ecm33 and ags3 mRNA expression. It is known that A. fumigatus mutants with absent or reduced expression of these genes have increased virulence in mice, as well as other phenotypic similarities to the Deltaace2 mutant. Therefore, reduced expression of these genes likely contributes to the increased virulence of the Deltaace2 mutant.
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Affiliation(s)
- Daniele E Ejzykowicz
- Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA
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17
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Fungal-Derived Immune Modulating Molecules. PATHOGEN-DERIVED IMMUNOMODULATORY MOLECULES 2009; 666:108-20. [DOI: 10.1007/978-1-4419-1601-3_9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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18
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Arana DM, Prieto D, Román E, Nombela C, Alonso-Monge R, Pla J. The role of the cell wall in fungal pathogenesis. Microb Biotechnol 2008; 2:308-20. [PMID: 21261926 PMCID: PMC3815752 DOI: 10.1111/j.1751-7915.2008.00070.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Fungal infections are a serious health problem. In recent years, basic research is focusing on the identification of fungal virulence factors as promising targets for the development of novel antifungals. The wall, as the most external cellular component, plays a crucial role in the interaction with host cells mediating processes such as adhesion or phagocytosis that are essential during infection. Specific components of the cell wall (called PAMPs) interact with specific receptors in the immune cell (called PRRs), triggering responses whose molecular mechanisms are being elucidated. We review here the main structural carbohydrate components of the fungal wall (glucan, mannan and chitin), how their biogenesis takes place in fungi and the specific receptors that they interact with. Different model fungal pathogens are chosen to illustrate the functional consequences of this interaction. Finally, the identification of the key components will have important consequences in the future and will allow better approaches to treat fungal infections.
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Affiliation(s)
- David M Arana
- Departamento de Microbiología II, Facultad de Farmacia, Universidad Complutense de Madrid, Plaza de Ramón y Cajal s/n, E-28040 Madrid, Spain
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19
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Tronchin G, Pihet M, Lopes-Bezerra LM, Bouchara JP. Adherence mechanisms in human pathogenic fungi. Med Mycol 2008; 46:749-72. [DOI: 10.1080/13693780802206435] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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20
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Toyotome T, Adachi Y, Watanabe A, Ochiai E, Ohno N, Kamei K. Activator protein 1 is triggered by Aspergillus fumigatus beta-glucans surface-exposed during specific growth stages. Microb Pathog 2007; 44:141-50. [PMID: 17928189 DOI: 10.1016/j.micpath.2007.08.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/28/2007] [Indexed: 11/29/2022]
Abstract
Aspergillus fumigatus has been shown to trigger the activation of nuclear factor-kappaB (NF-kappaB), but it remains unclear whether other transcription factors are also induced following infection by this organism. In this study, we demonstrated that A. fumigatus also triggers activator protein 1 (AP-1), a transcription factor that plays an important role during the production of cytokines and chemokines. Swollen conidia strongly induce the activation of AP-1, and more than 80% of these were stained positively with anti-beta-glucan antibodies by fluorescence microscopy. Hyphae were also stained with anti-beta-glucan antibodies, albeit significantly weaker compared with swollen conidia. Furthermore, our present findings also showed that A. fumigatus triggers the activation of AP-1 in a dectin-1 (receptor for beta-glucan)-dependent manner. These data thus suggest that AP-1 is triggered by beta-glucan recognition on the surface of A. fumigatus. We also showed that Syk tyrosine kinase is required for AP-1 induction in this pathway. We therefore speculate that the dectin-1/Syk/AP-1 signaling pathway plays an important role in the host defense response to fungal infection.
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Affiliation(s)
- Takahito Toyotome
- Division of Fungal Infection, Research Center for Pathogenic Fungi and Microbial Toxicoses, Chiba University, Chiba City, Chiba, Japan.
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21
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Volling K, Brakhage AA, Saluz HP. Apoptosis inhibition of alveolar macrophages upon interaction with conidia of Aspergillus fumigatus. FEMS Microbiol Lett 2007; 275:250-4. [PMID: 17714483 DOI: 10.1111/j.1574-6968.2007.00883.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The opportunistic human pathogenic fungus Aspergillus fumigatus (Af) causes the majority of cases of invasive aspergillosis. Because Af enters the human body through inhalation of airborne conidia, the interaction of conidia with the innate immune system (alveolar macrophages) plays a key role in the etiology of aspergillosis. Therefore, it is of central interest to investigate response mechanisms of alveolar macrophages upon interaction with Af. Here, it is demonstrate that Af inhibited host cell apoptosis of alveolar macrophages, one of the major defense immune effector cells against this pathogen. This unexpected result was due to inhibition of caspase 3 by a yet unknown mechanism.
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Affiliation(s)
- Katrin Volling
- Department of Cell and Molecular Biology, Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knoell-Institute (HKI), and Friedrich Schiller University Jena, Jena, Germany
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22
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Taubitz A, Bauer B, Heesemann J, Ebel F. Role of respiration in the germination process of the pathogenic mold Aspergillus fumigatus. Curr Microbiol 2007; 54:354-60. [PMID: 17486408 DOI: 10.1007/s00284-006-0413-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Accepted: 02/03/2007] [Indexed: 10/23/2022]
Abstract
Inhalation of resting conidia is usually the first step of a systemic infection caused by the opportunistic fungal pathogen Aspergillus fumigatus. In the lung, the inhaled spores encounter an environment that permits germination. However, the relative importance of certain environmental conditions for conidial activation and subsequent hyphae formation has so far not been analyzed in detail. In this study, we studied the role of oxygen during germination. We found that inhibitors of the respiratory chain were nearly as efficient in blocking germination as cycloheximide, an inhibitor of protein synthesis, which is already known to prevent germination of Aspergillus nidulans. We also found that A. fumigatus is unable to grow or germinate under anaerobic conditions, and using the fluorescent mitotracker dye we detected active mitochondria already at the stage of swollen conidia, which indicates that respiration is an early event during germination. In line with these data, we found that significant oxygen consumption was detectable early during germination, whereas no oxygen consumption was measurable in suspensions of resting conidia. In summary, the present study provides evidence that respiration is absolutely required for the germination of A. fumigatus conidia.
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Affiliation(s)
- Anela Taubitz
- Max-von-Pettenkofer-Institut, Ludwig-Maximilians-Universität, Pettenkoferstr. 9a, D-80336, Munich, Germany
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Steele C, Rapaka RR, Metz A, Pop SM, Williams DL, Gordon S, Kolls JK, Brown GD. The beta-glucan receptor dectin-1 recognizes specific morphologies of Aspergillus fumigatus. PLoS Pathog 2005; 1:e42. [PMID: 16344862 PMCID: PMC1311140 DOI: 10.1371/journal.ppat.0010042] [Citation(s) in RCA: 383] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Accepted: 11/03/2005] [Indexed: 01/02/2023] Open
Abstract
Alveolar macrophages represent a first-line innate host defense mechanism for clearing inhaled Aspergillus fumigatus from the lungs, yet contradictory data exist as to which alveolar macrophage recognition receptor is critical for innate immunity to A. fumigatus. Acknowledging that the A. fumigatus cell wall contains a high beta-1,3–glucan content, we questioned whether the beta-glucan receptor dectin-1 played a role in this recognition process. Monoclonal antibody, soluble receptor, and competitive carbohydrate blockage indicated that the alveolar macrophage inflammatory response, specifically the production of tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α), IL-1β, IL-6, CXCL2/macrophage inflammatory protein-2 (MIP-2), CCL3/macrophage inflammatory protein-1α (MIP-1α), granulocyte-colony stimulating factor (G-CSF), and granulocyte monocyte–CSF (GM-CSF), to live A. fumigatus was dependent on recognition via the beta-glucan receptor dectin-1. The inflammatory response was triggered at the highest level by A. fumigatus swollen conidia and early germlings and correlated to the levels of surface-exposed beta glucans, indicating that dectin-1 preferentially recognizes specific morphological forms of A. fumigatus. Intratracheal administration of A. fumigatus conidia to mice in the presence of a soluble dectin-Fc fusion protein reduced both lung proinflammatory cytokine/chemokine levels and cellular recruitment while modestly increasing the A. fumigatus fungal burden, illustrating the importance of beta-glucan–initiated dectin-1 signaling in defense against this pathogen. Collectively, these data show that dectin-1 is centrally required for the generation of alveolar macrophage proinflammatory responses to A. fumigatus and to our knowledge provides the first in vivo evidence for the role of dectin-1 in fungal innate defense. Individuals with defective immune systems are highly susceptible to infection by parasites, bacteria, viruses, and fungi. Infection by the opportunistic fungal organism Aspergillus fumigatus can be particularly severe in this population. Because many pathogenic microorganisms, including A. fumigatus, enter the body through the lung, it is important to understand the function of its immune system. The alveolar macrophage is one of the first cell types to come in contact with inhaled pathogens. An intense area of research is how lung immune cells—i.e., alveolar macrophages—recognize inhaled pathogens and respond to them. Steele et al. recently discovered that alveolar macrophages express a receptor on their surface, dectin-1, that is essential in recognizing and responding to inhaled fungal pathogens. They now have investigated the interaction between dectin-1 and A. fumigatus to determine how the dectin-1 receptor orchestrates the alveolar macrophage response. They found that alveolar macrophages respond poorly to A. fumigatus when the dectin-1 receptor is blocked. Also, in animal experiments, blocking dectin-1 renders the animals more susceptible to infection with A. fumigatus. This study may lay the foundation for developing new and novel strategies to combat infections caused by A. fumigatus.
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Affiliation(s)
- Chad Steele
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pennsylvania, USA.
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24
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Hohl TM, Van Epps HL, Rivera A, Morgan LA, Chen PL, Feldmesser M, Pamer EG. Aspergillus fumigatus triggers inflammatory responses by stage-specific beta-glucan display. PLoS Pathog 2005; 1:e30. [PMID: 16304610 PMCID: PMC1287910 DOI: 10.1371/journal.ppat.0010030] [Citation(s) in RCA: 341] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Accepted: 10/13/2005] [Indexed: 11/18/2022] Open
Abstract
Inhalation of fungal spores (conidia) occurs commonly and, in specific circumstances, can result in invasive disease. We investigated the murine inflammatory response to conidia of Aspergillus fumigatus, the most common invasive mold in immunocompromised hosts. In contrast to dormant spores, germinating conidia induce neutrophil recruitment to the airways and TNF-alpha/MIP-2 secretion by alveolar macrophages. Fungal beta-glucans act as a trigger for the induction of these inflammatory responses through their time-dependent exposure on the surface of germinating conidia. Dectin-1, an innate immune receptor that recognizes fungal beta-glucans, is recruited in vivo to alveolar macrophage phagosomes that have internalized conidia with exposed beta-glucans. Antibody-mediated blockade of Dectin-1 partially inhibits TNF-alpha/MIP-2 induction by metabolically active conidia. TLR-2- and MyD88-mediated signals provide an additive contribution to macrophage activation by germinating conidia. Selective responsiveness to germinating conidia provides the innate immune system with a mechanism to restrict inflammatory responses to metabolically active, potentially invasive fungal spores.
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Affiliation(s)
- Tobias M Hohl
- Infectious Diseases Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
- Immunology Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Heather L. Van Epps
- Immunology Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Amariliz Rivera
- Immunology Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Laura A Morgan
- Immunology Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Patrick L Chen
- Division of Infectious Diseases, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Marta Feldmesser
- Division of Infectious Diseases, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Eric G Pamer
- Infectious Diseases Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
- Immunology Program, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
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Grimm LH, Kelly S, Hengstler J, Göbel A, Krull R, Hempel DC. Kinetic studies on the aggregation of Aspergillus niger conidia. Biotechnol Bioeng 2005; 87:213-8. [PMID: 15236250 DOI: 10.1002/bit.20130] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Morphology has a crucial effect on productivity and the supply of substrate for cultures of filamentous fungi. However, cultivation parameters leading to the desired morphology are often chosen empirically as the mechanisms governing the processes involved are usually unknown. For coagulating microorganisms like Aspergillus niger the morphological development is considered to start with the aggregation of conidia right after inoculation. To elucidate the mechanism of this process, kinetic studies were carried out using an in-line particle size analyzer. Based on the data obtained from these experiments a model for conidial aggregation is proposed in this article. It consists of two separate aggregation steps. The first one takes place immediately after inoculation, but only leads to a small decrease of total particle concentration. Most suspended conidia aggregate after a second aggregation step triggered by germination and hyphal growth. Aggregation velocity of this second phase is linearly dependent on the particle growth rate.
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Affiliation(s)
- L H Grimm
- Institute of Biochemical Engineering, Technical University of Braunschweig, Gaussstrasse 17, 38106 Braunschweig, Germany
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26
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Grimm LH, Kelly S, Völkerding II, Krull R, Hempel DC. Influence of mechanical stress and surface interaction on the aggregation ofAspergillus niger conidia. Biotechnol Bioeng 2005; 92:879-88. [PMID: 16255057 DOI: 10.1002/bit.20666] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Productivity of fungal cultures is closely linked with their morphologic development. Morphogenesis of coagulating filamentous fungi, like Aspergillus niger, starts with aggregation of conidia, also denominated as spores. Several parameters are presumed to control this event, but little is known about their mode of action. Rational process optimization requires models that mirror the underlying reaction mechanisms. An approach in this regard is suggested and supported by experimental data. Aggregation kinetics was examined for the first 15 h of cultivation under different cultivation conditions. Mechanical stress was considered as well as pH-dependent surface interaction. Deliberations were based on a two-step aggregation mechanism. The first aggregation step is only affected by the pH-value, not by the fluid dynamic conditions in the bioreactor. The second aggregation step, in contrast, depends on the pH-value as well as on agitation and aeration induced power input. For the given experimental set-up, agitation had much more influence than aeration. In addition, hyphal growth rate was determined to be the driving force for the second aggregation step.
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Affiliation(s)
- L H Grimm
- Institute of Biochemical Engineering, Technical University of Braunschweig
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Singh T, Saikia R, Jana T, Arora DK. Hydrophobicity and surface electrostatic charge of conidia of the mycoparasitic Trichoderma species. Mycol Prog 2004. [DOI: 10.1007/s11557-006-0092-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Meier A, Kirschning CJ, Nikolaus T, Wagner H, Heesemann J, Ebel F. Toll-like receptor (TLR) 2 and TLR4 are essential for Aspergillus-induced activation of murine macrophages. Cell Microbiol 2003; 5:561-70. [PMID: 12864815 DOI: 10.1046/j.1462-5822.2003.00301.x] [Citation(s) in RCA: 212] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Aspergillus fumigatius is a ubiquitous saprophytic fungus that has become the most prevalent airborne fungal pathogen for immunocompromised patients during the last two decades. In this report we have analysed how macrophages recognize this microorganism. Using transfected human HEK 293 cells we demonstrate that NF-kappaB-dependent promoter activation triggered by A. fumigatus is mediated by Toll-like receptors TLR2 and TLR4, whereas no activation was observed in cells overexpressing other distinct TLR proteins (TLR1, TLR3, TLR5-10). Using macrophages derived from mice lacking TLR2 expression, expressing defective TLR4 or both we found that A. fumigatus conidia and hyphae induce NF-kappaB translocation, release of pro-inflammatory molecules, like TNFalpha, and the chemoattractant MIP-2 in a TLR2- and TLR4-dependent manner. Recognition of A. niger and A. fumigatus, was similar in terms of the parameters analysed, suggesting that pathogenic and non-pathogenic aspergilli are sensed by macrophages in a similar fashion. Finally, we found that recruitment of neutrophils is severely impaired in mice lacking both functional TLR2 and TLR4, but is less impaired in single TLR2- or TLR4-deficient mice, providing evidence that both receptors are required for an optimal immune response to Aspergillus in vivo.
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Affiliation(s)
- A Meier
- Max-von-Pettenkofer-Institute, Ludwig-Maximilians-University, Munich, Germany
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29
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Marr KA, Patterson T, Denning D. Aspergillosis. Pathogenesis, clinical manifestations, and therapy. Infect Dis Clin North Am 2002; 16:875-94, vi. [PMID: 12512185 DOI: 10.1016/s0891-5520(02)00035-1] [Citation(s) in RCA: 263] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Diseases caused by Aspergillus species are increasing in importance, especially among immunocompromised hosts. Clinical manifestations are variable, ranging from allergic to invasive disease, largely depending on the status of the host's immune system. This article focuses on the pathogenesis and clinical manifestations of diseases caused by Aspergillus species, with more detailed discussion on therapy of the most morbid manifestation, invasive aspergillosis.
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Affiliation(s)
- Kieren A Marr
- Program in Infectious Diseases, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue, N. D3-100, Seattle, WA 98109, USA.
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Tronchin G, Esnault K, Sanchez M, Larcher G, Marot-Leblond A, Bouchara JP. Purification and partial characterization of a 32-kilodalton sialic acid-specific lectin from Aspergillus fumigatus. Infect Immun 2002; 70:6891-5. [PMID: 12438366 PMCID: PMC133100 DOI: 10.1128/iai.70.12.6891-6895.2002] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2002] [Revised: 08/28/2002] [Accepted: 09/16/2002] [Indexed: 11/20/2022] Open
Abstract
Adherence of the opportunistic fungus Aspergillus fumigatus to the extracellular matrix components is considered a crucial step in the establishment of the infection. Given the high carbohydrate content of these glycoproteins and the role of carbohydrate-protein interactions in numerous adherence processes, the presence of a lectin in A. fumigatus was investigated. Different fungal extracts obtained by sonication or grinding in liquid nitrogen from resting or swollen conidia, as well as from germ tubes and mycelium, were tested by hemagglutination assays using rabbit erythrocytes. A lectin activity was recovered in all the extracts tested. However, sonication of resting conidia resulted in the highest specific activity. Purification of the lectin was achieved by gel filtration followed by ion-exchange and hydrophobic-interaction chromatographies. Analysis of the purified lectin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed an apparent molecular mass of 32 kDa, which is similar to that of the alkaline protease already identified from different strains of A. fumigatus. However, as evidenced by the use of an alkaline protease-deficient mutant, the two activities were supported by distinct proteins. In addition, hemagglutination inhibition experiments using different saccharides and glycoproteins demonstrated the specificity of the lectin for sialic acid residues. Together these results suggest that this lectin may contribute to the attachment of conidia to the extracellular matrix components through the recognition of the numerous terminal sialic acid residues of their carbohydrate chains.
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Affiliation(s)
- Guy Tronchin
- Groupe d'Etude des Interactions Hôte-Parasite, UPRES EA 3142, Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire, Angers, France.
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Rohde M, Schwienbacher M, Nikolaus T, Heesemann J, Ebel F. Detection of early phase specific surface appendages during germination of Aspergillus fumigatus conidia. FEMS Microbiol Lett 2002; 206:99-105. [PMID: 11786264 DOI: 10.1111/j.1574-6968.2002.tb10993.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
During the past 15 years the saprophytic fungus Aspergillus fumigatus has become the most prevalent airborne fungal pathogen, causing severe and often fatal infections especially in immuno-compromised patients. Germination of inhaled conidia is an early and crucial event in the infection process of A. fumigatus. In this study we have analyzed morphological changes that take place during this differentiation process using scanning electron microscopy. Our data show that (i) the hydrophobic surface layer of resting conidia seems to be shed before the cells start to swell and (ii) that filamentous surface appendages are expressed at a very early phase of the germtube formation. These surface structures were only found on the first few microm of the germtube, but were absent from the surface of mycelial hyphae and resting or swollen conidia. The highly regulated expression of these novel surface organelles suggests that they may play an important role during early germination and represent a potential target for future anti-A. fumigatus therapies.
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Affiliation(s)
- Manfred Rohde
- Gesellschaft für Biotechnologische Forschung, Bereich Mikrobiologie, Braunschweig, Germany
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Abstract
The asexual spore, or conidium, is critical in the life cycle of many fungi because it is the primary means for dispersion and serves as a 'safe house' for the fungal genome in adverse environmental conditions. This review discusses the physiological process of germination, conidial adhesion and initiation of protein synthesis and also the regulatory pathways used to activate conidial germination. These include Ca(2+)/calmodulin-mediated signaling, the cyclic AMP/protein kinase A and the ras/mitogen-activated protein kinase pathways. Insights into the process of conidial germination will increase our understanding of the mechanisms of dormancy and sensing of environmental stimuli, and permit identification of novel therapeutic targets for the treatment of spore-borne fungal infections in plants and animals.
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Affiliation(s)
- N Osherov
- Division of Pathology and Laboratory Medicine, P.O. Box 54, The University of Texas, M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA
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Wollensak G, Green WR. Remarkable case of early Aspergillus endophthalmitis. AUSTRALIAN AND NEW ZEALAND JOURNAL OF OPHTHALMOLOGY 1999; 27:361-4. [PMID: 10571402 DOI: 10.1046/j.1440-1606.1999.00220.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND This case demonstrates the early stage of Aspergillus endophthalmitis and is the second ultrastructural study of endogenous Aspergillus endophthalmitis. It is the first description of phagocytosis of Aspergillus fungi by retinal pigment epithelium (RPE). METHODS A case report and detailed light- and electron microscopic findings are presented. RESULTS Histopathological examination of serial sections of the affected right eye displayed a spread of Aspergillus fumigatus fungi along two separate paths: via the retinal and choroidal vessels. The retinal and choroidal lesions were not contiguous. The organisms penetrated blood vessel walls, Bruch's membrane and the internal limiting membrane, but not the RPE layer. A curious accumulation of the Aspergillus fungi was present on the internal aspect of Bruch's membrane, where the RPE acted as a barrier and the subretinal space was not invaded. Phagocytosis of fungi by the RPE was observed. No inflammatory cells were present between Bruch's membrane and the RPE. CONCLUSIONS This report describes a remarkable barrier function, possible local immunosuppression and phagocytosis by the RPE cells in a case of early Aspergillus endophthalmitis.
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Affiliation(s)
- G Wollensak
- Eye Pathology Laboratory, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, USA. gwollens@http://www.hotmail.com
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Abstract
Aspergillus fumigatus is one of the most ubiquitous of the airborne saprophytic fungi. Humans and animals constantly inhale numerous conidia of this fungus. The conidia are normally eliminated in the immunocompetent host by innate immune mechanisms, and aspergilloma and allergic bronchopulmonary aspergillosis, uncommon clinical syndromes, are the only infections observed in such hosts. Thus, A. fumigatus was considered for years to be a weak pathogen. With increases in the number of immunosuppressed patients, however, there has been a dramatic increase in severe and usually fatal invasive aspergillosis, now the most common mold infection worldwide. In this review, the focus is on the biology of A. fumigatus and the diseases it causes. Included are discussions of (i) genomic and molecular characterization of the organism, (ii) clinical and laboratory methods available for the diagnosis of aspergillosis in immunocompetent and immunocompromised hosts, (iii) identification of host and fungal factors that play a role in the establishment of the fungus in vivo, and (iv) problems associated with antifungal therapy.
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Affiliation(s)
- J P Latgé
- Laboratoire des Aspergillus, Institut Pasteur, 75015 Paris, France.
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Esnault K, el Moudni B, Bouchara JP, Chabasse D, Tronchin G. Association of a myosin immunoanalogue with cell envelopes of Aspergillus fumigatus conidia and its participation in swelling and germination. Infect Immun 1999; 67:1238-44. [PMID: 10024566 PMCID: PMC96452 DOI: 10.1128/iai.67.3.1238-1244.1999] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A myosin immunoanalogue was identified in conidia of Aspergillus fumigatus by Western blotting, indirect immunofluorescence assay, and gold immunoelectron microscopy with two different antimyosin antibodies. The distribution pattern of this protein was followed during the early stages of germination. A single 180-kDa polypeptide, detected predominantly in a cell envelope extract, was found to cross-react with monoclonal and polyclonal antibodies raised against vertebrate muscle myosin. Immunoelectron microscopy permitted precise localization of this polypeptide, indicating that myosin analogue was mainly distributed along the plasma membrane of resting and swollen conidia. In germinating conidia, indirect immunofluorescence microscopy revealed myosin analogue at the periphery of germ tubes, whereas actin appeared as dispersed punctate structures in the cytoplasm that were more concentrated at the site of germ tube emergence. A myosin ATPase inhibitor, butanedione monoxime, greatly reduced swelling and blocked germination. In contrast, when conidia were treated with cytochalasin B, an inhibitor of actin polymerization, swelling was not affected and germination was only partially reduced. Butanedione monoxime-treated conidia showed accumulation of cytoplasmic vesicles and did not achieve cell wall reorganization, unlike swollen conidia. Collectively, these results suggest an essential role for this myosin analogue in the deposition of cell wall components during germination of A. fumigatus conidia and therefore in host tissue colonization.
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Affiliation(s)
- K Esnault
- Groupe d'Etude des Interactions Hôte-Parasite, Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire, 49033 Angers, France
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De Lucca AJ, Bland JM, Grimm C, Jacks TJ, Cary JW, Jaynes JM, Cleveland TE, Walsh TJ. Fungicidal properties, sterol binding, and proteolytic resistance of the synthetic peptide D4E1. Can J Microbiol 1998; 44:514-20. [PMID: 9734302 DOI: 10.1139/w98-032] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The fungicidal properties of the synthetic peptide D4E1 were studied with nongerminated and germinating conidia of Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Fusarium moniliforme, and Fusarium oxysporum. The minimal lethal concentrations (MLC) needed to kill 100% of germinating conidia of A. fumigatus, A. flavus, and A. niger were 12.5, 12.5, and 25 microM, respectively. The MLC value for nongerminated and germinating conidia of both Fusarium spp. was 3.0 microM. Except for A. fumigatus, D4E1 was inactive against the nongerminated conidia of the Aspergillus spp. Physicochemical studies showed D4E1 complexed with ergosterol, a sterol present in conidial walls. Cholesterol, present in nongerminated conidia of F. moniliforme, had a greater affinity for D4E1 than did ergosterol. D4E1 was more resistant to fungal and plant protease degradation than the natural peptide, cecropin A. These in vitro results suggest D4E1 is a candidate for transgenic expression in plants to enhance host resistance to fungal infection.
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Affiliation(s)
- A J De Lucca
- Southern Regional Research Center, United States Department of Agriculture, New Orleans, LA 70124, USA.
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Tronchin G, Esnault K, Renier G, Filmon R, Chabasse D, Bouchara JP. Expression and identification of a laminin-binding protein in Aspergillus fumigatus conidia. Infect Immun 1997; 65:9-15. [PMID: 8975886 PMCID: PMC174550 DOI: 10.1128/iai.65.1.9-15.1997] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Adhesion of Aspergillus fumigatus, the causative agent of human aspergillosis, to the extracellular matrix protein laminin has been previously demonstrated. This study investigated the expression of laminin receptors during swelling of conidia, a step leading to germination and subsequent colonization of tissues. Scanning electron microscopy showed that the laminin binding sites were distributed over the external rodlet layer of resting conidia. During swelling, the characteristic rodlet layer progressively disintegrated and conidia surrounded by a smooth cell wall layer appeared. Flow cytometry using fluorescein isothiocyanate-conjugated laminin demonstrated that expression of laminin receptors at the surface of conidia was swelling dependent. Resting conidia expressed high levels of laminin receptors on their surface. A gradual decrease of laminin binding was then observed as swelling occurred, reaching a minimum for 4-h-swollen conidia. This correlated with a loss of adherence of swollen conidia to laminin immobilized on microtiter plates. Trypsin pretreatment of conidia reduced laminin binding. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ligand blotting with laminin identified in a cell wall extract a major 72-kDa cell wall glycoprotein which binds laminin. Thus, one of the initial events in the host colonization may be the recognition of basement membrane laminin by this 72-kDa cell wall surface component.
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Affiliation(s)
- G Tronchin
- Groupe d'Etude des Interactions Hôte-Parasite, Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire, Angers, France
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