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Al-Bader N, Sheppard DC. Aspergillosis and stem cell transplantation: An overview of experimental pathogenesis studies. Virulence 2016; 7:950-966. [PMID: 27687755 DOI: 10.1080/21505594.2016.1231278] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Invasive aspergillosis is a life-threatening infection caused by the opportunistic filamentous fungus Aspergillus fumigatus. Patients undergoing haematopoietic stem cell transplant (HSCT) for the treatment of hematological malignancy are at particularly high risk of developing this fatal infection. The susceptibility of HSCT patients to infection with A. fumigatus is a consequence of a complex interplay of both fungal and host factors. Here we review our understanding of the host-pathogen interactions underlying the susceptibility of the immunocompromised host to infection with A. fumigatus with a focus on the experimental validation of fungal and host factors relevant to HSCT patients. These include fungal factors such as secondary metabolites, cell wall constituents, and metabolic adaptations that facilitate immune evasion and survival within the host microenvironment, as well as the innate and adaptive immune responses involved in host defense against A. fumigatus.
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Affiliation(s)
- Nadia Al-Bader
- a Departments of Medicine, Microbiology and Immunology , McGill University , Montréal , Québec , Canada
| | - Donald C Sheppard
- a Departments of Medicine, Microbiology and Immunology , McGill University , Montréal , Québec , Canada.,b Infectious Diseases in Global Health Program, Research Institute of the McGill University Health Center, McGill University , Montréal , Québec , Canada
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52
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Moloney NM, Owens RA, Doyle S. Proteomic analysis of Aspergillus fumigatus – clinical implications. Expert Rev Proteomics 2016; 13:635-49. [DOI: 10.1080/14789450.2016.1203783] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
| | | | - Sean Doyle
- Department of Biology, Maynooth University, Maynooth, Ireland
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53
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Neves GWP, Curty NDA, Kubitschek-Barreira PH, Fontaine T, Souza GHMF, Cunha ML, Goldman GH, Beauvais A, Latgé JP, Lopes-Bezerra LM. Modifications to the composition of the hyphal outer layer of Aspergillus fumigatus modulates HUVEC proteins related to inflammatory and stress responses. J Proteomics 2016; 151:83-96. [PMID: 27321585 DOI: 10.1016/j.jprot.2016.06.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 04/20/2016] [Accepted: 06/07/2016] [Indexed: 12/11/2022]
Abstract
Aspergillus fumigatus, the main etiologic agent causing invasive aspergillosis, can induce an inflammatory response and a prothrombotic phenotype upon contact with human umbilical vein endothelial cells (HUVECs). However, the fungal molecules involved in this endothelial response remain unknown. A. fumigatus hyphae produce an extracellular matrix composed of galactomannan, galactosaminogalactan and α-(1,3)-glucan. In this study, we investigated the consequences of UGM1 gene deletion in A. fumigatus, which produces a mutant with increased galactosaminogalactan production. The ∆ugm1 mutant exhibited an HUVEC-hyperadhesive phenotype and induced increased endothelial TNF-α secretion and tissue factor mRNA overexpression in this "semi-professional" immune host cell. Using a shotgun proteomics approach, we show that the A. fumigatus ∆ugm1 strain can modulate the levels of proteins in important endothelial pathways related to the inflammatory response mediated by TNF-α and to stress response pathways. Furthermore, a purified galactosaminogalactan fraction was also able to induce TNF-α secretion and the coincident HUVEC pathways regulated by the ∆ugm1 mutant, which overexpresses this component, as demonstrated by fluorescence microscopy. This work contributes new data regarding endothelial mechanisms in response to A. fumigatus infection. SIGNIFICANCE Invasive aspergillosis is the main opportunistic fungal infection described in neutropenic hematologic patients. One important clinical aspect of this invasive fungal infection is vascular thrombosis, which could be related, at least in part, to the activation of endothelial cells, as shown in previous reports from our group. It is known that direct contact between the A. fumigatus hyphal cell wall and the HUVEC cell surface is necessary to induce an endothelial prothrombotic phenotype and secretion of pro-inflammatory cytokines, though the cell surface components of this angioinvasive fungus that trigger this endothelial response are unknown. The present work employs a discovery-driven proteomics approach to reveal the role of one important cell wall polysaccharide of A. fumigatus, galactosaminogalactan, in the HUVEC interaction and the consequent mechanisms of endothelial activation. This is the first report of the overall panel of proteins related to the HUVEC response to a specific and purified cell wall component of the angioinvasive fungus A. fumigatus.
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Affiliation(s)
- Gabriela Westerlund Peixoto Neves
- Laboratory of Cellular Mycology and Proteomics, Universidade do Estado do Rio de Janeiro, Campus Maracanã, Pavilhão Haroldo Lisboa da Cunha sl 501D, CEP: 20550-013, Rio de Janeiro, RJ, Brazil
| | - Nathália de Andrade Curty
- Laboratory of Cellular Mycology and Proteomics, Universidade do Estado do Rio de Janeiro, Campus Maracanã, Pavilhão Haroldo Lisboa da Cunha sl 501D, CEP: 20550-013, Rio de Janeiro, RJ, Brazil
| | - Paula Helena Kubitschek-Barreira
- Laboratory of Cellular Mycology and Proteomics, Universidade do Estado do Rio de Janeiro, Campus Maracanã, Pavilhão Haroldo Lisboa da Cunha sl 501D, CEP: 20550-013, Rio de Janeiro, RJ, Brazil
| | - Thierry Fontaine
- Unité des Aspergillus, Institut Pasteur, 25 rue du Docteur Roux, 75724, Paris Cedex 15, France
| | | | - Marcel Lyra Cunha
- Laboratory of Cellular Mycology and Proteomics, Universidade do Estado do Rio de Janeiro, Campus Maracanã, Pavilhão Haroldo Lisboa da Cunha sl 501D, CEP: 20550-013, Rio de Janeiro, RJ, Brazil
| | - Gustavo H Goldman
- Universidade de São Paulo, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Departamento de Ciências Farmacêuticas, Av. do Cafe S/N, Monte Alegre, CEP:14040-903, Ribeirao Preto, SP, Brazil
| | - Anne Beauvais
- Unité des Aspergillus, Institut Pasteur, 25 rue du Docteur Roux, 75724, Paris Cedex 15, France
| | - Jean-Paul Latgé
- Unité des Aspergillus, Institut Pasteur, 25 rue du Docteur Roux, 75724, Paris Cedex 15, France
| | - Leila M Lopes-Bezerra
- Laboratory of Cellular Mycology and Proteomics, Universidade do Estado do Rio de Janeiro, Campus Maracanã, Pavilhão Haroldo Lisboa da Cunha sl 501D, CEP: 20550-013, Rio de Janeiro, RJ, Brazil.
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54
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Trevijano-Contador N, Rueda C, Zaragoza O. Fungal morphogenetic changes inside the mammalian host. Semin Cell Dev Biol 2016; 57:100-109. [PMID: 27101887 DOI: 10.1016/j.semcdb.2016.04.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 04/12/2016] [Accepted: 04/15/2016] [Indexed: 10/21/2022]
Abstract
One of the main features of the majority of pathogenic fungi is the ability to switch between different types of morphological forms. These changes include the transition between cells of different shapes (such as the formation of pseudohyphae and hyphae), or the massive growth of the blastoconidia and formation of titan cells. Morphological changes occur during infection, and there is extensive evidence that they play a key role in processes required for disease, such as adhesion, invasion and dissemination, immune recognition evasion, and phagocytosis avoidance. In the present review, we will provide an overview of how morphological transitions contribute to the development of fungal disease, with special emphasis in two cases: Candida albicans as an example of yeast that switches between blastoconidia and filaments, and Cryptococcus neoformans as an example of a fungus that changes the size without modifying the shape of the cell.
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Affiliation(s)
- Nuria Trevijano-Contador
- Mycology Reference Laboratory, National Centre for Microbiology, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo Km2, Majadahonda 28220, Madrid, Spain
| | - Cristina Rueda
- Mycology Reference Laboratory, National Centre for Microbiology, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo Km2, Majadahonda 28220, Madrid, Spain
| | - Oscar Zaragoza
- Mycology Reference Laboratory, National Centre for Microbiology, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo Km2, Majadahonda 28220, Madrid, Spain.
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55
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Croft CA, Culibrk L, Moore MM, Tebbutt SJ. Interactions of Aspergillus fumigatus Conidia with Airway Epithelial Cells: A Critical Review. Front Microbiol 2016; 7:472. [PMID: 27092126 PMCID: PMC4823921 DOI: 10.3389/fmicb.2016.00472] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 03/21/2016] [Indexed: 02/05/2023] Open
Abstract
Aspergillus fumigatus is an environmental filamentous fungus that also acts as an opportunistic pathogen able to cause a variety of symptoms, from an allergic response to a life-threatening disseminated fungal infection. The infectious agents are inhaled conidia whose first point of contact is most likely to be an airway epithelial cell (AEC). The interaction between epithelial cells and conidia is multifaceted and complex, and has implications for later steps in pathogenesis. Increasing evidence has demonstrated a key role for the airway epithelium in the response to respiratory pathogens, particularly at early stages of infection; therefore, elucidating the early stages of interaction of conidia with AECs is essential to understand the establishment of infection in cohorts of at-risk patients. Here, we present a comprehensive review of the early interactions between A. fumigatus and AECs, including bronchial and alveolar epithelial cells. We describe mechanisms of adhesion, internalization of conidia by AECs, the immune response of AECs, as well as the role of fungal virulence factors, and patterns of fungal gene expression characteristic of early infection. A clear understanding of the mechanisms involved in the early establishment of infection by A. fumigatus could point to novel targets for therapy and prophylaxis.
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Affiliation(s)
- Carys A Croft
- Centre for Heart Lung Innovation, St. Paul's Hospital, University of British Columbia, Vancouver BC, Canada
| | - Luka Culibrk
- Centre for Heart Lung Innovation, St. Paul's Hospital, University of British Columbia, Vancouver BC, Canada
| | - Margo M Moore
- Department of Biological Sciences, Simon Fraser University, Burnaby BC, Canada
| | - Scott J Tebbutt
- Centre for Heart Lung Innovation, St. Paul's Hospital, University of British Columbia, VancouverBC, Canada; Prevention of Organ Failure Centre of Excellence, VancouverBC, Canada; Department of Medicine, Division of Respiratory Medicine, University of British Columbia, VancouverBC, Canada
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56
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Abstract
The mold Aspergillus fumigatus causes invasive infection in immunocompromised patients. Recently, galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetylgalactosamine (GalNAc), was identified as a virulence factor required for biofilm formation. The molecular mechanisms underlying GAG biosynthesis and GAG-mediated biofilm formation were unknown. We identified a cluster of five coregulated genes that were dysregulated in GAG-deficient mutants and whose gene products share functional similarity with proteins that mediate the synthesis of the bacterial biofilm exopolysaccharide poly-(β1-6)-N-acetyl-d-glucosamine (PNAG). Bioinformatic analyses suggested that the GAG cluster gene agd3 encodes a protein containing a deacetylase domain. Because deacetylation of N-acetylglucosamine residues is critical for the function of PNAG, we investigated the role of GAG deacetylation in fungal biofilm formation. Agd3 was found to mediate deacetylation of GalNAc residues within GAG and render the polysaccharide polycationic. As with PNAG, deacetylation is required for the adherence of GAG to hyphae and for biofilm formation. Growth of the Δagd3 mutant in the presence of culture supernatants of the GAG-deficient Δuge3 mutant rescued the biofilm defect of the Δagd3 mutant and restored the adhesive properties of GAG, suggesting that deacetylation is an extracellular process. The GAG biosynthetic gene cluster is present in the genomes of members of the Pezizomycotina subphylum of the Ascomycota including a number of plant-pathogenic fungi and a single basidiomycete species, Trichosporon asahii, likely a result of recent horizontal gene transfer. The current study demonstrates that the production of cationic, deacetylated exopolysaccharides is a strategy used by both fungi and bacteria for biofilm formation. This study sheds light on the biosynthetic pathways governing the synthesis of galactosaminogalactan (GAG), which plays a key role in A. fumigatus virulence and biofilm formation. We find that bacteria and fungi use similar strategies to synthesize adhesive biofilm exopolysaccharides. The presence of orthologs of the GAG biosynthetic gene clusters in multiple fungi suggests that this exopolysaccharide may also be important in the virulence of other fungal pathogens. Further, these studies establish a molecular mechanism of adhesion in which GAG interacts via charge-charge interactions to bind to both fungal hyphae and other substrates. Finally, the importance of deacetylation in the synthesis of functional GAG and the extracellular localization of this process suggest that inhibition of deacetylation may be an attractive target for the development of novel antifungal therapies.
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57
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Culibrk L, Croft CA, Tebbutt SJ. Systems Biology Approaches for Host-Fungal Interactions: An Expanding Multi-Omics Frontier. OMICS : A JOURNAL OF INTEGRATIVE BIOLOGY 2016; 20:127-38. [PMID: 26885725 PMCID: PMC4799697 DOI: 10.1089/omi.2015.0185] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Opportunistic fungal infections are an increasing threat for global health, and for immunocompromised patients in particular. These infections are characterized by interaction between fungal pathogen and host cells. The exact mechanisms and the attendant variability in host and fungal pathogen interaction remain to be fully elucidated. The field of systems biology aims to characterize a biological system, and utilize this knowledge to predict the system's response to stimuli such as fungal exposures. A multi-omics approach, for example, combining data from genomics, proteomics, metabolomics, would allow a more comprehensive and pan-optic "two systems" biology of both the host and the fungal pathogen. In this review and literature analysis, we present highly specialized and nascent methods for analysis of multiple -omes of biological systems, in addition to emerging single-molecule visualization techniques that may assist in determining biological relevance of multi-omics data. We provide an overview of computational methods for modeling of gene regulatory networks, including some that have been applied towards the study of an interacting host and pathogen. In sum, comprehensive characterizations of host-fungal pathogen systems are now possible, and utilization of these cutting-edge multi-omics strategies may yield advances in better understanding of both host biology and fungal pathogens at a systems scale.
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Affiliation(s)
- Luka Culibrk
- Centre for Heart Lung Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - Carys A. Croft
- Centre for Heart Lung Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - Scott J. Tebbutt
- Centre for Heart Lung Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
- Prevention of Organ Failure (PROOF) Centre of Excellence, Vancouver, British Columbia, Canada
- Department of Medicine, Division of Respiratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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58
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Transcription Factor SomA Is Required for Adhesion, Development and Virulence of the Human Pathogen Aspergillus fumigatus. PLoS Pathog 2015; 11:e1005205. [PMID: 26529322 PMCID: PMC4631450 DOI: 10.1371/journal.ppat.1005205] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 09/13/2015] [Indexed: 11/19/2022] Open
Abstract
The transcription factor Flo8/Som1 controls filamentous growth in Saccharomyces cerevisiae and virulence in the plant pathogen Magnaporthe oryzae. Flo8/Som1 includes a characteristic N-terminal LUG/LUH-Flo8-single-stranded DNA binding (LUFS) domain and is activated by the cAMP dependent protein kinase A signaling pathway. Heterologous SomA from Aspergillus fumigatus rescued in yeast flo8 mutant strains several phenotypes including adhesion or flocculation in haploids and pseudohyphal growth in diploids, respectively. A. fumigatus SomA acts similarly to yeast Flo8 on the promoter of FLO11 fused with reporter gene (LacZ) in S. cerevisiae. FLO11 expression in yeast requires an activator complex including Flo8 and Mfg1. Furthermore, SomA physically interacts with PtaB, which is related to yeast Mfg1. Loss of the somA gene in A. fumigatus resulted in a slow growth phenotype and a block in asexual development. Only aerial hyphae without further differentiation could be formed. The deletion phenotype was verified by a conditional expression of somA using the inducible Tet-on system. A adherence assay with the conditional somA expression strain indicated that SomA is required for biofilm formation. A ptaB deletion strain showed a similar phenotype supporting that the SomA/PtaB complex controls A. fumigatus biofilm formation. Transcriptional analysis showed that SomA regulates expression of genes for several transcription factors which control conidiation or adhesion of A. fumigatus. Infection assays with fertilized chicken eggs as well as with mice revealed that SomA is required for pathogenicity. These data corroborate a complex control function of SomA acting as a central factor of the transcriptional network, which connects adhesion, spore formation and virulence in the opportunistic human pathogen A. fumigatus. Invasive fungal infections affecting immunocompromised patients are emerging worldwide. Among various human fungal pathogens, Aspergillus fumigatus is one of the most common molds causing severe invasive aspergillosis in immunocompromised patients. The conidia, which can evade from innate immunity and adhere to epithelial cells of alveoli in human lungs will start to germinate and cause the disease. Currently, the understanding of the molecular mechanisms of adherence of fungal cells to hosts is scarce. The transcription factor Flo8 controls adhesion to biotic or abiotic surfaces and morphological development in baker’s yeast. Flo8 homologues in the dimorphic human pathogenic yeast Candida albicans or the filamentous plant pathogen Magnaporthe oryzae are required for development and virulence. We found in this study that the Flo8 homologue SomA of A. fumigatus is required for adhesion and conidiation. Two independent invasive aspergillosis assays using chicken eggs or mouse demonstrated that deletion of the corresponding gene resulted in attenuated virulence. SomA represents an important fungal transcription factor at the interface between adherence, asexual spore formation and pathogenicity in an important opportunistic human pathogen.
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59
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Beaussart A, El-Kirat-Chatel S, Fontaine T, Latgé JP, Dufrêne YF. Nanoscale biophysical properties of the cell surface galactosaminogalactan from the fungal pathogen Aspergillus fumigatus. NANOSCALE 2015; 7:14996-15004. [PMID: 26308550 DOI: 10.1039/c5nr04399a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Many fungal pathogens produce cell surface polysaccharides that play essential roles in host-pathogen interactions. In Aspergillus fumigatus, the newly discovered polysaccharide galactosaminogalactan (GAG) mediates adherence to a variety of substrates through molecular mechanisms that are poorly understood. Here we use atomic force microscopy to unravel the localization and adhesion of GAG on living fungal cells. Using single-molecule imaging with tips bearing anti-GAG antibodies, we found that GAG is massively exposed on wild-type (WT) germ tubes, consistent with the notion that this glycopolymer is secreted by the mycelium of A. fumigatus, while it is lacking on WT resting conidia and on germ tubes from a mutant (Δuge3) deficient in GAG. Imaging germ tubes with tips bearing anti-β-glucan antibodies shows that exposure of β-glucan is strongly increased in the Δuge3 mutant, indicating that this polysaccharide is masked by GAG during hyphal growth. Single-cell force measurements show that expression of GAG on germ tubes promotes specific adhesion to pneumocytes and non-specific adhesion to hydrophobic substrates. These results provide a molecular foundation for the multifunctional adhesion properties of GAG, thus suggesting it could be used as a potential target in anti-adhesion therapy and immunotherapy. Our methodology represents a powerful approach for characterizing the nanoscale organization and adhesion of cell wall polysaccharides during fungal morphogenesis, thereby contributing to increase our understanding of their role in biofilm formation and immune responses.
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Affiliation(s)
- Audrey Beaussart
- Université catholique de Louvain, Institute of Life Sciences, Croix du Sud, 4-5, bte L7.07.06, B-1348 Louvain-la-Neuve, Belgium.
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60
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Zhang C, Kong Q, Cai Z, Liu F, Chen P, Song J, Lu L, Sang H. The newly nonsporulated characterization of an Aspergillus fumigatus isolate from an immunocompetent patient and its clinic indication. Fungal Genet Biol 2015; 81:250-60. [DOI: 10.1016/j.fgb.2015.03.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2014] [Revised: 03/02/2015] [Accepted: 03/05/2015] [Indexed: 12/14/2022]
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61
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cspA influences biofilm formation and drug resistance in pathogenic fungus Aspergillus fumigatus. BIOMED RESEARCH INTERNATIONAL 2015; 2015:960357. [PMID: 25821832 PMCID: PMC4363613 DOI: 10.1155/2015/960357] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 02/09/2015] [Indexed: 11/17/2022]
Abstract
The microbial cell wall plays a crucial role in biofilm formation and drug resistance. cspA encodes a repeat-rich glycophosphatidylinositol-anchored cell wall protein in the pathogenic fungus Aspergillus fumigatus. To determine whether cspA has a significant impact on biofilm development and sensitivity to antifungal drugs in A. fumigatus, a ΔcspA mutant was constructed by targeted gene disruption, and we then reconstituted the mutant to wild type by homologous recombination of a functional cspA gene. Deletion of cspA resulted in a rougher conidial surface, reduced biofilm formation, decreased resistance to antifungal agents, and increased internalization by A549 human lung epithelial cells, suggesting that cspA not only participates in maintaining the integrity of the cell wall, but also affects biofilm establishment, drug response, and invasiveness of A. fumigatus.
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62
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Jiang Z, Liu N, Hu D, Dong G, Miao Z, Yao J, He H, Jiang Y, Zhang W, Wang Y, Sheng C. The discovery of novel antifungal scaffolds by structural simplification of the natural product sampangine. Chem Commun (Camb) 2015; 51:14648-51. [DOI: 10.1039/c5cc05699c] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Structural simplification of the natural product sampangine led to the discovery of two novel antifungal compounds with excellent activity and low toxicity.
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Affiliation(s)
- Zhigan Jiang
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
- State Key Laboratory of Drug Lead Compound Research
| | - Na Liu
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
| | - Dandan Hu
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
| | - Guoqiang Dong
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
| | - Zhenyuan Miao
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
| | - Jianzhong Yao
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
| | - Haiying He
- State Key Laboratory of Drug Lead Compound Research
- Shanghai
- China
| | - Yuanying Jiang
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
| | - Wannian Zhang
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
| | - Yan Wang
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
| | - Chunquan Sheng
- School of Pharmacy
- Second Military Medical University
- Shanghai
- China
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63
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Abstract
Aspergillus fumigatus is a well adapted, opportunistic fungus that causes a severe and commonly fatal disease, invasive pulmonary aspergillosis (IPA), in highly immunocompromised patients, aspergilloma in patients with lung cavities and allergic bronchopulmonary aspergillosis (ABPA) in hypersensitive individuals. Recent studies have suggested that biofilm formation by A. fumigatus may be one of the most important virulence factors in IPA and aspergilloma. Several fungal constituents may contribute to the formation of biofilm structures on host cells, including cell wall components, secondary metabolites and drug transporters. The biofilm phenotype of the fungus is refractory to most conventional antifungal treatment options. Thus, an in-depth analysis and understanding of A. fumigatus biofilms is necessary to devise newer and better antifungal targets for treating complex A. fumigatus biofilm-associated diseases.
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Affiliation(s)
- Savneet Kaur
- School of Biotechnology, Gautam Buddha University, Greater Noida, India
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64
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Johnson G, Ferrini A, Dolan SK, Nolan T, Agrawal S, Doyle S, Bustin SA. Biomarkers for invasive aspergillosis: the challenges continue. Biomark Med 2014; 8:429-51. [PMID: 24712434 DOI: 10.2217/bmm.13.129] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The incidence of invasive aspergillosis (IA), an opportunistic infection in immunocompromised individuals, is rising, but its early diagnosis remains challenging and treatment options are limited. Hence there is an urgent need to improve existing diagnostic procedures as well as develop novel approaches. The clinical usefulness of galactomannan and β-d-glucan, widely used assays detecting cell-wall antigens of Aspergillus, is unclear and depends on clinicians' awareness of their practical limitations. This leaves room for new methods that utilise genomic, proteomic and metabolomics approaches as well as novel detection procedures, for example point-of-care lateral-flow devices. Each of these strategies has its own limitations and it is likely that a combination of methods will be required to achieve optimal performance for the diagnosis of IA and subsequent appropriate patient management.
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Affiliation(s)
- Gemma Johnson
- Blizard Institute, Queen Mary University of London, London, UK
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65
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Merlos R, Amighi K, Wauthoz N. Recent Developments in Inhaled Triazoles Against Invasive Pulmonary Aspergillosis. CURRENT FUNGAL INFECTION REPORTS 2014. [DOI: 10.1007/s12281-014-0199-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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66
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A polysaccharide virulence factor from Aspergillus fumigatus elicits anti-inflammatory effects through induction of Interleukin-1 receptor antagonist. PLoS Pathog 2014; 10:e1003936. [PMID: 24603878 PMCID: PMC3946377 DOI: 10.1371/journal.ppat.1003936] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 01/05/2014] [Indexed: 11/20/2022] Open
Abstract
The galactosaminogalactan (GAG) is a cell wall component of Aspergillus fumigatus that has potent anti-inflammatory effects in mice. However, the mechanisms responsible for the anti-inflammatory property of GAG remain to be elucidated. In the present study we used in vitro PBMC stimulation assays to demonstrate, that GAG inhibits proinflammatory T-helper (Th)1 and Th17 cytokine production in human PBMCs by inducing Interleukin-1 receptor antagonist (IL-1Ra), a potent anti-inflammatory cytokine that blocks IL-1 signalling. GAG cannot suppress human T-helper cytokine production in the presence of neutralizing antibodies against IL-1Ra. In a mouse model of invasive aspergillosis, GAG induces IL-1Ra in vivo, and the increased susceptibility to invasive aspergillosis in the presence of GAG in wild type mice is not observed in mice deficient for IL-1Ra. Additionally, we demonstrate that the capacity of GAG to induce IL-1Ra could also be used for treatment of inflammatory diseases, as GAG was able to reduce severity of an experimental model of allergic aspergillosis, and in a murine DSS-induced colitis model. In the setting of invasive aspergillosis, GAG has a significant immunomodulatory function by inducing IL-1Ra and notably IL-1Ra knockout mice are completely protected to invasive pulmonary aspergillosis. This opens new treatment strategies that target IL-1Ra in the setting of acute invasive fungal infection. However, the observation that GAG can also protect mice from allergy and colitis makes GAG or a derivative structure of GAG a potential treatment compound for IL-1 driven inflammatory diseases. Aspergillus fumigatus is an opportunistic pathogenic fungus that primarily causes infections in the immunocompromised host. It is known that Aspergillus employs various strategies to evade immune recognition by the host's immune system. Recently, galactosaminogalactan (GAG), a new component of the Aspergillus cell wall, was discovered to have potent anti-inflammatory effects in mice making them more susceptible to Aspergillosis. In the current study we found that this anti-inflammatory property of GAG was due to its capacity to induce the potent anti-inflammatory cytokine interleukin-1 Receptor antagonist. This cytokine interferes with IL-1 signalling and thereby can reduce IL-1–induced immune responses such as T-cell responses. We also found that the induction of this anti-inflammatory cytokine by GAG correlates with increased fungal burden, and mice deficient for this cytokine were protected against aspergillosis. Additionally, we show that the capacity of GAG to induce the natural regulator of IL-1 signalling could be used in the treatment of IL-1–mediated disease such as allergy and colitis. Our study provides new insights on the immunoregulatory activity of GAG and opens up possibilities to exploit the anti-inflammatory potential of GAG as a therapy for inflammatory diseases.
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Gravelat FN, Beauvais A, Liu H, Lee MJ, Snarr BD, Chen D, Xu W, Kravtsov I, Hoareau CMQ, Vanier G, Urb M, Campoli P, Al Abdallah Q, Lehoux M, Chabot JC, Ouimet MC, Baptista SD, Fritz JH, Nierman WC, Latgé JP, Mitchell AP, Filler SG, Fontaine T, Sheppard DC. Aspergillus galactosaminogalactan mediates adherence to host constituents and conceals hyphal β-glucan from the immune system. PLoS Pathog 2013; 9:e1003575. [PMID: 23990787 PMCID: PMC3749958 DOI: 10.1371/journal.ppat.1003575] [Citation(s) in RCA: 220] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 07/09/2013] [Indexed: 11/24/2022] Open
Abstract
Aspergillus fumigatus is the most common cause of invasive mold disease in humans. The mechanisms underlying the adherence of this mold to host cells and macromolecules have remained elusive. Using mutants with different adhesive properties and comparative transcriptomics, we discovered that the gene uge3, encoding a fungal epimerase, is required for adherence through mediating the synthesis of galactosaminogalactan. Galactosaminogalactan functions as the dominant adhesin of A. fumigatus and mediates adherence to plastic, fibronectin, and epithelial cells. In addition, galactosaminogalactan suppresses host inflammatory responses in vitro and in vivo, in part through masking cell wall β-glucans from recognition by dectin-1. Finally, galactosaminogalactan is essential for full virulence in two murine models of invasive aspergillosis. Collectively these data establish a role for galactosaminogalactan as a pivotal bifunctional virulence factor in the pathogenesis of invasive aspergillosis. Invasive aspergillosis is the most common mold infection in humans, predominately affecting immunocompromised patients. The mechanisms by which the mold Aspergillus fumigatus adheres to host tissues and causes disease are poorly understood. In this report, we compared mutants of Aspergillus with different adhesive properties to identify fungal factors involved in adherence to host cells. This approach identified a cell wall associated polysaccharide, galactosaminogalactan, which is required for adherence to a wide variety of substrates. Galactosaminogalactan was also observed to suppress inflammation by concealing β-glucans, key pattern associated microbial pattern molecules in Aspergillus hyphae, from recognition by the innate immune system. Mutants that were deficient in galactosaminogalactan were less virulent in mouse models of invasive aspergillosis. These data identify a bifunctional role for galactosaminogalactan in the pathogenesis of invasive aspergillosis, and suggest that it may serve as a useful target for antifungal therapy.
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Affiliation(s)
- Fabrice N. Gravelat
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | | | - Hong Liu
- Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor - University of California, Los Angeles Medical Center, Torrance, California, United States of America
| | - Mark J. Lee
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Brendan D. Snarr
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Dan Chen
- J. Craig Ventker Institute, Rockville, Maryland, United States of America
| | - Wenjie Xu
- Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - Ilia Kravtsov
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | | | - Ghyslaine Vanier
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Mirjam Urb
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Paolo Campoli
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Qusai Al Abdallah
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Melanie Lehoux
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Josée C. Chabot
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Marie-Claude Ouimet
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Stefanie D. Baptista
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - Jörg H. Fritz
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
| | - William C. Nierman
- J. Craig Ventker Institute, Rockville, Maryland, United States of America
| | | | - Aaron P. Mitchell
- Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - Scott G. Filler
- Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor - University of California, Los Angeles Medical Center, Torrance, California, United States of America
- David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, California, United States of America
| | - Thierry Fontaine
- Aspergillus Unit, Institut Pasteur, Paris, France
- * E-mail: (TF); (DCS)
| | - Donald C. Sheppard
- Departments of Microbiology and Immunology, Medicine, McGill University, Montréal, Québec, Canada
- * E-mail: (TF); (DCS)
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Campoli P, Perlin DS, Kristof AS, White TC, Filler SG, Sheppard DC. Pharmacokinetics of posaconazole within epithelial cells and fungi: insights into potential mechanisms of action during treatment and prophylaxis. J Infect Dis 2013; 208:1717-28. [PMID: 23908482 DOI: 10.1093/infdis/jit358] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND The antifungal posaconazole concentrates within host cells and protects against Aspergillus fumigatus. The specific subcellular location of posaconazole and the mechanism by which cell-associated posaconazole inhibits fungal growth remain uncharacterized. METHODS Posaconazole was conjugated with the fluorophore boron-dipyrromethene (BDP-PCZ). A549 pulmonary epithelial cells and A. fumigatus were exposed to BDP-PCZ individually and in coculture. BDP-PCZ subcellular localization and trafficking were observed using confocal microscopy and flow cytometry. RESULTS BDP-PCZ concentrated within A549 cell membranes, and in particular within the endoplasmic reticulum. Epithelial cell-associated BDP-PCZ rapidly transferred to and concentrated within A. fumigatus cell membranes on contact. BDP-PCZ transfer to conidia did not require phagocytosis and was markedly enhanced by the conidial hydrophobin RodA. Within AF, BDP-PCZ also concentrated in membranes including the endoplasmic reticulum and colocalized with the azole target enzyme CYP51a. Concentration of BDP-PCZ within host and fungal cell membranes persisted for >48 hours and could be competitively inhibited by posaconazole but not voriconazole. CONCLUSIONS Posaconazole concentrates within host cell membranes and rapidly transfers to A. fumigatus, where it accumulates to high concentrations and persists at the site of its target enzyme. These intracellular and intercellular pharmacokinetic properties probably contribute to the efficacy of PCZ.
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Abstract
The composition and organization of the cell walls from Saccharomyces cerevisiae, Candida albicans, Aspergillus fumigatus, Schizosaccharomyces pombe, Neurospora crassa, and Cryptococcus neoformans are compared and contrasted. These cell walls contain chitin, chitosan, β-1,3-glucan, β-1,6-glucan, mixed β-1,3-/β-1,4-glucan, α-1,3-glucan, melanin, and glycoproteins as major constituents. A comparison of these cell walls shows that there is a great deal of variability in fungal cell wall composition and organization. However, in all cases, the cell wall components are cross-linked together to generate a cell wall matrix. The biosynthesis and properties of each of the major cell wall components are discussed. The chitin and glucans are synthesized and extruded into the cell wall space by plasma membrane-associated chitin synthases and glucan synthases. The glycoproteins are synthesized by ER-associated ribosomes and pass through the canonical secretory pathway. Over half of the major cell wall proteins are modified by the addition of a glycosylphosphatidylinositol anchor. The cell wall glycoproteins are also modified by the addition of O-linked oligosaccharides, and their N-linked oligosaccharides are extensively modified during their passage through the secretory pathway. These cell wall glycoprotein posttranslational modifications are essential for cross-linking the proteins into the cell wall matrix. Cross-linking the cell wall components together is essential for cell wall integrity. The activities of four groups of cross-linking enzymes are discussed. Cell wall proteins function as cross-linking enzymes, structural elements, adhesins, and environmental stress sensors and protect the cell from environmental changes.
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Affiliation(s)
- Stephen J Free
- Department of Biological Sciences, SUNY, University at Buffalo, Buffalo, New York, USA.
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Gibbons JG, Rokas A. The function and evolution of the Aspergillus genome. Trends Microbiol 2012; 21:14-22. [PMID: 23084572 DOI: 10.1016/j.tim.2012.09.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2012] [Revised: 09/20/2012] [Accepted: 09/24/2012] [Indexed: 10/27/2022]
Abstract
Species in the filamentous fungal genus Aspergillus display a wide diversity of lifestyles and are of great importance to humans. The decoding of genome sequences from a dozen species that vary widely in their degree of evolutionary affinity has galvanized studies of the function and evolution of the Aspergillus genome in clinical, industrial, and agricultural environments. Here, we synthesize recent key findings that shed light on the architecture of the Aspergillus genome, on the molecular foundations of the genus' astounding dexterity and diversity in secondary metabolism, and on the genetic underpinnings of virulence in Aspergillus fumigatus, one of the most lethal fungal pathogens. Many of these insights dramatically expand our knowledge of fungal and microbial eukaryote genome evolution and function and argue that Aspergillus constitutes a superb model clade for the study of functional and comparative genomics.
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Affiliation(s)
- John G Gibbons
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
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