<named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin

ABSTRACT The macrophage response to planktonic Staphylococcus aureus involves the induction of proinflammatory microbicidal activity. However, S. aureus biofilms can interfere with these responses in part by polarizing macrophages toward an anti-inflammatory profibrotic phenotype. Here we demonstrat...

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Autores principales:	Tyler D. Scherr, Mark L. Hanke, Ouwen Huang, David B. A. James, Alexander R. Horswill, Kenneth W. Bayles, Paul D. Fey, Victor J. Torres, Tammy Kielian
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/c55082d268f9458ca6c96b049b4388eb
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spelling	oai:doaj.org-article:c55082d268f9458ca6c96b049b4388eb2021-11-15T15:41:26Z<named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin10.1128/mBio.01021-152150-7511https://doaj.org/article/c55082d268f9458ca6c96b049b4388eb2015-09-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01021-15https://doaj.org/toc/2150-7511ABSTRACT The macrophage response to planktonic Staphylococcus aureus involves the induction of proinflammatory microbicidal activity. However, S. aureus biofilms can interfere with these responses in part by polarizing macrophages toward an anti-inflammatory profibrotic phenotype. Here we demonstrate that conditioned medium from mature S. aureus biofilms inhibited macrophage phagocytosis and induced cytotoxicity, suggesting the involvement of a secreted factor(s). Iterative testing found the active factor(s) to be proteinaceous and partially agr-dependent. Quantitative mass spectrometry identified alpha-toxin (Hla) and leukocidin AB (LukAB) as critical molecules secreted by S. aureus biofilms that inhibit murine macrophage phagocytosis and promote cytotoxicity. A role for Hla and LukAB was confirmed by using hla and lukAB mutants, and synergy between the two toxins was demonstrated with a lukAB hla double mutant and verified by complementation. Independent confirmation of the effects of Hla and LukAB on macrophage dysfunction was demonstrated by using an isogenic strain in which Hla was constitutively expressed, an Hla antibody to block toxin activity, and purified LukAB peptide. The importance of Hla and LukAB during S. aureus biofilm formation in vivo was assessed by using a murine orthopedic implant biofilm infection model in which the lukAB hla double mutant displayed significantly lower bacterial burdens and more macrophage infiltrates than each single mutant. Collectively, these findings reveal a critical synergistic role for Hla and LukAB in promoting macrophage dysfunction and facilitating S. aureus biofilm development in vivo. IMPORTANCE Staphylococcus aureus has a propensity to form multicellular communities known as biofilms. While growing in a biofilm, S. aureus displays increased tolerance to nutrient deprivation, antibiotic insult, and even host immune challenge. Previous studies have shown that S. aureus biofilms thwart host immunity in part by preventing macrophage phagocytosis. It remained unclear whether this was influenced solely by the considerable size of biofilms or whether molecules were also actively secreted to circumvent macrophage-mediated phagocytosis. This is the first report to demonstrate that S. aureus biofilms inhibit macrophage phagocytosis and induce macrophage death through the combined action of leukocidin AB and alpha-toxin. Loss of leukocidin AB and alpha-toxin expression resulted in enhanced S. aureus biofilm clearance in a mouse model of orthopedic implant infection, suggesting that these toxins could be targeted therapeutically to facilitate biofilm clearance in humans.Tyler D. ScherrMark L. HankeOuwen HuangDavid B. A. JamesAlexander R. HorswillKenneth W. BaylesPaul D. FeyVictor J. TorresTammy KielianAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 4 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Tyler D. Scherr Mark L. Hanke Ouwen Huang David B. A. James Alexander R. Horswill Kenneth W. Bayles Paul D. Fey Victor J. Torres Tammy Kielian <named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin
description	ABSTRACT The macrophage response to planktonic Staphylococcus aureus involves the induction of proinflammatory microbicidal activity. However, S. aureus biofilms can interfere with these responses in part by polarizing macrophages toward an anti-inflammatory profibrotic phenotype. Here we demonstrate that conditioned medium from mature S. aureus biofilms inhibited macrophage phagocytosis and induced cytotoxicity, suggesting the involvement of a secreted factor(s). Iterative testing found the active factor(s) to be proteinaceous and partially agr-dependent. Quantitative mass spectrometry identified alpha-toxin (Hla) and leukocidin AB (LukAB) as critical molecules secreted by S. aureus biofilms that inhibit murine macrophage phagocytosis and promote cytotoxicity. A role for Hla and LukAB was confirmed by using hla and lukAB mutants, and synergy between the two toxins was demonstrated with a lukAB hla double mutant and verified by complementation. Independent confirmation of the effects of Hla and LukAB on macrophage dysfunction was demonstrated by using an isogenic strain in which Hla was constitutively expressed, an Hla antibody to block toxin activity, and purified LukAB peptide. The importance of Hla and LukAB during S. aureus biofilm formation in vivo was assessed by using a murine orthopedic implant biofilm infection model in which the lukAB hla double mutant displayed significantly lower bacterial burdens and more macrophage infiltrates than each single mutant. Collectively, these findings reveal a critical synergistic role for Hla and LukAB in promoting macrophage dysfunction and facilitating S. aureus biofilm development in vivo. IMPORTANCE Staphylococcus aureus has a propensity to form multicellular communities known as biofilms. While growing in a biofilm, S. aureus displays increased tolerance to nutrient deprivation, antibiotic insult, and even host immune challenge. Previous studies have shown that S. aureus biofilms thwart host immunity in part by preventing macrophage phagocytosis. It remained unclear whether this was influenced solely by the considerable size of biofilms or whether molecules were also actively secreted to circumvent macrophage-mediated phagocytosis. This is the first report to demonstrate that S. aureus biofilms inhibit macrophage phagocytosis and induce macrophage death through the combined action of leukocidin AB and alpha-toxin. Loss of leukocidin AB and alpha-toxin expression resulted in enhanced S. aureus biofilm clearance in a mouse model of orthopedic implant infection, suggesting that these toxins could be targeted therapeutically to facilitate biofilm clearance in humans.
format	article
author	Tyler D. Scherr Mark L. Hanke Ouwen Huang David B. A. James Alexander R. Horswill Kenneth W. Bayles Paul D. Fey Victor J. Torres Tammy Kielian
author_facet	Tyler D. Scherr Mark L. Hanke Ouwen Huang David B. A. James Alexander R. Horswill Kenneth W. Bayles Paul D. Fey Victor J. Torres Tammy Kielian
author_sort	Tyler D. Scherr
title	<named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin
title_short	<named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin
title_full	<named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin
title_fullStr	<named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin
title_full_unstemmed	<named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin
title_sort	<named-content content-type="genus-species">staphylococcus aureus</named-content> biofilms induce macrophage dysfunction through leukocidin ab and alpha-toxin
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/c55082d268f9458ca6c96b049b4388eb
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<named-content content-type="genus-species">Staphylococcus aureus</named-content> Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin

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