Candida albicans Hypha Formation and Mannan Masking of β-Glucan Inhibit Macrophage Phagosome Maturation

Judith M Bain, Johanna Louw, Leanne E Lewis, Blessing Okai, Catriona A Walls, Elizabeth R Ballou, Louise A Walker, Delyth Reid, Carol A Munro, Alistair J P Brown, Gordon D Brown, Neil A R Gow, Lars P Erwig

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Abstract

UNLABELLED: Candida albicans is a major life-threatening human fungal pathogen in the immunocompromised host. Host defense against systemic Candida infection relies heavily on the capacity of professional phagocytes of the innate immune system to ingest and destroy fungal cells. A number of pathogens, including C. albicans, have evolved mechanisms that attenuate the efficiency of phagosome-mediated inactivation, promoting their survival and replication within the host. Here we visualize host-pathogen interactions using live-cell imaging and show that viable, but not heat- or UV-killed C. albicans cells profoundly delay phagosome maturation in macrophage cell lines and primary macrophages. The ability of C. albicans to delay phagosome maturation is dependent on cell wall composition and fungal morphology. Loss of cell wall O-mannan is associated with enhanced acquisition of phagosome maturation markers, distinct changes in Rab GTPase acquisition by the maturing phagosome, impaired hyphal growth within macrophage phagosomes, profound changes in macrophage actin dynamics, and ultimately a reduced ability of fungal cells to escape from macrophage phagosomes. The loss of cell wall O-mannan leads to exposure of β-glucan in the inner cell wall, facilitating recognition by Dectin-1, which is associated with enhanced phagosome maturation.

IMPORTANCE: Innate cells engulf and destroy invading organisms by phagocytosis, which is essential for the elimination of fungal cells to protect against systemic life-threatening infections. Yet comparatively little is known about what controls the maturation of phagosomes following ingestion of fungal cells. We used live-cell microscopy and fluorescent protein reporter macrophages to understand how C. albicans viability, filamentous growth, and cell wall composition affect phagosome maturation and the survival of the pathogen within host macrophages. We have demonstrated that cell wall glycosylation and yeast-hypha morphogenesis are required for disruption of host processes that function to inactivate pathogens, leading to survival and escape of this fungal pathogen from within host phagocytes. The methods employed here are applicable to study interactions of other pathogens with phagocytic cells to dissect how specific microbial features impact different stages of phagosome maturation and the survival of the pathogen or host.

Original languageEnglish
Article numbere01874-14
JournalmBio
Volume5
Issue number6
DOIs
Publication statusPublished - 2 Dec 2014

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Mannans
Phagosomes
Glucans
Hyphae
Candida albicans
Macrophages
Cell Wall
Phagocytes
rab GTP-Binding Proteins
Host-Pathogen Interactions
Immunocompromised Host
Growth
Glycosylation
Morphogenesis
Phagocytosis
Actins
Microscopy
Immune System
Eating
Hot Temperature

Cite this

Bain, J. M., Louw, J., Lewis, L. E., Okai, B., Walls, C. A., Ballou, E. R., ... Erwig, L. P. (2014). Candida albicans Hypha Formation and Mannan Masking of β-Glucan Inhibit Macrophage Phagosome Maturation. mBio, 5(6), [e01874-14]. https://doi.org/10.1128/mBio.01874-14

Candida albicans Hypha Formation and Mannan Masking of β-Glucan Inhibit Macrophage Phagosome Maturation. / Bain, Judith M; Louw, Johanna; Lewis, Leanne E; Okai, Blessing; Walls, Catriona A; Ballou, Elizabeth R; Walker, Louise A; Reid, Delyth; Munro, Carol A; Brown, Alistair J P; Brown, Gordon D; Gow, Neil A R; Erwig, Lars P.

In: mBio, Vol. 5, No. 6, e01874-14, 02.12.2014.

Research output: Contribution to journalArticle

Bain, JM, Louw, J, Lewis, LE, Okai, B, Walls, CA, Ballou, ER, Walker, LA, Reid, D, Munro, CA, Brown, AJP, Brown, GD, Gow, NAR & Erwig, LP 2014, 'Candida albicans Hypha Formation and Mannan Masking of β-Glucan Inhibit Macrophage Phagosome Maturation', mBio, vol. 5, no. 6, e01874-14. https://doi.org/10.1128/mBio.01874-14
Bain, Judith M ; Louw, Johanna ; Lewis, Leanne E ; Okai, Blessing ; Walls, Catriona A ; Ballou, Elizabeth R ; Walker, Louise A ; Reid, Delyth ; Munro, Carol A ; Brown, Alistair J P ; Brown, Gordon D ; Gow, Neil A R ; Erwig, Lars P. / Candida albicans Hypha Formation and Mannan Masking of β-Glucan Inhibit Macrophage Phagosome Maturation. In: mBio. 2014 ; Vol. 5, No. 6.
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T1 - Candida albicans Hypha Formation and Mannan Masking of β-Glucan Inhibit Macrophage Phagosome Maturation

AU - Bain, Judith M

AU - Louw, Johanna

AU - Lewis, Leanne E

AU - Okai, Blessing

AU - Walls, Catriona A

AU - Ballou, Elizabeth R

AU - Walker, Louise A

AU - Reid, Delyth

AU - Munro, Carol A

AU - Brown, Alistair J P

AU - Brown, Gordon D

AU - Gow, Neil A R

AU - Erwig, Lars P

N1 - Received 28 August 2014 Accepted 28 October 2014 Published 2 December 2014 Copyright © 2014 Bain et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported license. ACKNOWLEDGMENTS We thank Janet Willment, Aberdeen Fungal Group, University of Aberdeen, for kindly providing the soluble Dectin-1-Fc reporter. All microscopy was performed with the assistance of the University of Aberdeen Core Microscopy & Histology Facility, and we thank the IFCC for their assistance with flow cytometry. We thank the Wellcome Trust for funding (080088, 086827, 075470, 099215, 097377, and 101873). E.R.B. and A.J.P.B. are funded by the European Research Council (ERC-2009-AdG-249793), and J.L. is funded by a Medical Research Council Clinical Training Fellowship.

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N2 - UNLABELLED: Candida albicans is a major life-threatening human fungal pathogen in the immunocompromised host. Host defense against systemic Candida infection relies heavily on the capacity of professional phagocytes of the innate immune system to ingest and destroy fungal cells. A number of pathogens, including C. albicans, have evolved mechanisms that attenuate the efficiency of phagosome-mediated inactivation, promoting their survival and replication within the host. Here we visualize host-pathogen interactions using live-cell imaging and show that viable, but not heat- or UV-killed C. albicans cells profoundly delay phagosome maturation in macrophage cell lines and primary macrophages. The ability of C. albicans to delay phagosome maturation is dependent on cell wall composition and fungal morphology. Loss of cell wall O-mannan is associated with enhanced acquisition of phagosome maturation markers, distinct changes in Rab GTPase acquisition by the maturing phagosome, impaired hyphal growth within macrophage phagosomes, profound changes in macrophage actin dynamics, and ultimately a reduced ability of fungal cells to escape from macrophage phagosomes. The loss of cell wall O-mannan leads to exposure of β-glucan in the inner cell wall, facilitating recognition by Dectin-1, which is associated with enhanced phagosome maturation.IMPORTANCE: Innate cells engulf and destroy invading organisms by phagocytosis, which is essential for the elimination of fungal cells to protect against systemic life-threatening infections. Yet comparatively little is known about what controls the maturation of phagosomes following ingestion of fungal cells. We used live-cell microscopy and fluorescent protein reporter macrophages to understand how C. albicans viability, filamentous growth, and cell wall composition affect phagosome maturation and the survival of the pathogen within host macrophages. We have demonstrated that cell wall glycosylation and yeast-hypha morphogenesis are required for disruption of host processes that function to inactivate pathogens, leading to survival and escape of this fungal pathogen from within host phagocytes. The methods employed here are applicable to study interactions of other pathogens with phagocytic cells to dissect how specific microbial features impact different stages of phagosome maturation and the survival of the pathogen or host.

AB - UNLABELLED: Candida albicans is a major life-threatening human fungal pathogen in the immunocompromised host. Host defense against systemic Candida infection relies heavily on the capacity of professional phagocytes of the innate immune system to ingest and destroy fungal cells. A number of pathogens, including C. albicans, have evolved mechanisms that attenuate the efficiency of phagosome-mediated inactivation, promoting their survival and replication within the host. Here we visualize host-pathogen interactions using live-cell imaging and show that viable, but not heat- or UV-killed C. albicans cells profoundly delay phagosome maturation in macrophage cell lines and primary macrophages. The ability of C. albicans to delay phagosome maturation is dependent on cell wall composition and fungal morphology. Loss of cell wall O-mannan is associated with enhanced acquisition of phagosome maturation markers, distinct changes in Rab GTPase acquisition by the maturing phagosome, impaired hyphal growth within macrophage phagosomes, profound changes in macrophage actin dynamics, and ultimately a reduced ability of fungal cells to escape from macrophage phagosomes. The loss of cell wall O-mannan leads to exposure of β-glucan in the inner cell wall, facilitating recognition by Dectin-1, which is associated with enhanced phagosome maturation.IMPORTANCE: Innate cells engulf and destroy invading organisms by phagocytosis, which is essential for the elimination of fungal cells to protect against systemic life-threatening infections. Yet comparatively little is known about what controls the maturation of phagosomes following ingestion of fungal cells. We used live-cell microscopy and fluorescent protein reporter macrophages to understand how C. albicans viability, filamentous growth, and cell wall composition affect phagosome maturation and the survival of the pathogen within host macrophages. We have demonstrated that cell wall glycosylation and yeast-hypha morphogenesis are required for disruption of host processes that function to inactivate pathogens, leading to survival and escape of this fungal pathogen from within host phagocytes. The methods employed here are applicable to study interactions of other pathogens with phagocytic cells to dissect how specific microbial features impact different stages of phagosome maturation and the survival of the pathogen or host.

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DO - 10.1128/mBio.01874-14

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