Kdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity

ABSTRACT The highly virulent Francisella tularensis subsp. tularensis has been classified as a category A bioterrorism agent. A live vaccine strain (LVS) has been developed but remains unlicensed in the United States because of an incomplete understanding of its attenuation. Lipopolysaccharide (LPS)...

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Autores principales:	Nihal A. Okan, Sabina Chalabaev, Tae-Hyun Kim, Avner Fink, Robin A. Ross, Dennis L. Kasper
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2013
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/e2dbee38dec14692b0a7218af97817a5
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spelling	oai:doaj.org-article:e2dbee38dec14692b0a7218af97817a52021-11-15T15:40:23ZKdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity10.1128/mBio.00638-122150-7511https://doaj.org/article/e2dbee38dec14692b0a7218af97817a52013-03-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00638-12https://doaj.org/toc/2150-7511ABSTRACT The highly virulent Francisella tularensis subsp. tularensis has been classified as a category A bioterrorism agent. A live vaccine strain (LVS) has been developed but remains unlicensed in the United States because of an incomplete understanding of its attenuation. Lipopolysaccharide (LPS) modification is a common strategy employed by bacterial pathogens to avoid innate immunity. A novel modification enzyme has recently been identified in F. tularensis and Helicobacter pylori. This enzyme, a two-component Kdo (3-deoxy-d-manno-octulosonic acid) hydrolase, catalyzes the removal of a side chain Kdo sugar from LPS precursors. The biological significance of this modification has not yet been studied. To address the role of the two-component Kdo hydrolase KdhAB in F. tularensis pathogenesis, a ΔkdhAB deletion mutant was constructed from the LVS strain. In intranasal infection of mice, the ΔkdhAB mutant strain had a 50% lethal dose (LD50) 2 log10 units higher than that of the parental LVS strain. The levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) in bronchoalveolar lavage fluid were significantly higher (2-fold) in mice infected with the ΔkdhAB mutant than in mice infected with LVS. In vitro stimulation of bone marrow-derived macrophages with the ΔkdhAB mutant induced higher levels of TNF-α and IL-1β in a TLR2-dependent manner. In addition, TLR2−/− mice were more susceptible than wild-type mice to ΔkdhAB bacterial infection. Finally, immunization of mice with ΔkdhAB bacteria elicited a high level of protection against the highly virulent F. tularensis subsp. tularensis strain Schu S4. These findings suggest an important role for the Francisella Kdo hydrolase system in virulence and offer a novel mutant as a candidate vaccine. IMPORTANCE The first line of defense against a bacterial pathogen is innate immunity, which slows the progress of infection and allows time for adaptive immunity to develop. Some bacterial pathogens, such as Francisella tularensis, suppress the early innate immune response, killing the host before adaptive immunity can mature. To avoid an innate immune response, F. tularensis enzymatically modifies its lipopolysaccharide (LPS). A novel LPS modification—Kdo (3-deoxy-d-manno-octulosonic acid) saccharide removal—has recently been reported in F. tularensis. We found that the ∆kdhAB mutant was significantly attenuated in mice. Additionally, the mutant strain induced an early innate immune response in mice both in vitro and in vivo. Immunization of mice with this mutant provided protection against the highly virulent F. tularensis strain Schu S4. Thus, our study has identified a novel LPS modification important for microbial virulence. A mutant lacking this modification may be used as a live attenuated vaccine against tularemia.Nihal A. OkanSabina ChalabaevTae-Hyun KimAvner FinkRobin A. RossDennis L. KasperAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 4, Iss 1 (2013)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Nihal A. Okan Sabina Chalabaev Tae-Hyun Kim Avner Fink Robin A. Ross Dennis L. Kasper Kdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity
description	ABSTRACT The highly virulent Francisella tularensis subsp. tularensis has been classified as a category A bioterrorism agent. A live vaccine strain (LVS) has been developed but remains unlicensed in the United States because of an incomplete understanding of its attenuation. Lipopolysaccharide (LPS) modification is a common strategy employed by bacterial pathogens to avoid innate immunity. A novel modification enzyme has recently been identified in F. tularensis and Helicobacter pylori. This enzyme, a two-component Kdo (3-deoxy-d-manno-octulosonic acid) hydrolase, catalyzes the removal of a side chain Kdo sugar from LPS precursors. The biological significance of this modification has not yet been studied. To address the role of the two-component Kdo hydrolase KdhAB in F. tularensis pathogenesis, a ΔkdhAB deletion mutant was constructed from the LVS strain. In intranasal infection of mice, the ΔkdhAB mutant strain had a 50% lethal dose (LD50) 2 log10 units higher than that of the parental LVS strain. The levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) in bronchoalveolar lavage fluid were significantly higher (2-fold) in mice infected with the ΔkdhAB mutant than in mice infected with LVS. In vitro stimulation of bone marrow-derived macrophages with the ΔkdhAB mutant induced higher levels of TNF-α and IL-1β in a TLR2-dependent manner. In addition, TLR2−/− mice were more susceptible than wild-type mice to ΔkdhAB bacterial infection. Finally, immunization of mice with ΔkdhAB bacteria elicited a high level of protection against the highly virulent F. tularensis subsp. tularensis strain Schu S4. These findings suggest an important role for the Francisella Kdo hydrolase system in virulence and offer a novel mutant as a candidate vaccine. IMPORTANCE The first line of defense against a bacterial pathogen is innate immunity, which slows the progress of infection and allows time for adaptive immunity to develop. Some bacterial pathogens, such as Francisella tularensis, suppress the early innate immune response, killing the host before adaptive immunity can mature. To avoid an innate immune response, F. tularensis enzymatically modifies its lipopolysaccharide (LPS). A novel LPS modification—Kdo (3-deoxy-d-manno-octulosonic acid) saccharide removal—has recently been reported in F. tularensis. We found that the ∆kdhAB mutant was significantly attenuated in mice. Additionally, the mutant strain induced an early innate immune response in mice both in vitro and in vivo. Immunization of mice with this mutant provided protection against the highly virulent F. tularensis strain Schu S4. Thus, our study has identified a novel LPS modification important for microbial virulence. A mutant lacking this modification may be used as a live attenuated vaccine against tularemia.
format	article
author	Nihal A. Okan Sabina Chalabaev Tae-Hyun Kim Avner Fink Robin A. Ross Dennis L. Kasper
author_facet	Nihal A. Okan Sabina Chalabaev Tae-Hyun Kim Avner Fink Robin A. Ross Dennis L. Kasper
author_sort	Nihal A. Okan
title	Kdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity
title_short	Kdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity
title_full	Kdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity
title_fullStr	Kdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity
title_full_unstemmed	Kdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity
title_sort	kdo hydrolase is required for <named-content content-type="genus-species">francisella tularensis</named-content> virulence and evasion of tlr2-mediated innate immunity
publisher	American Society for Microbiology
publishDate	2013
url	https://doaj.org/article/e2dbee38dec14692b0a7218af97817a5
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Kdo Hydrolase Is Required for <named-content content-type="genus-species">Francisella tularensis</named-content> Virulence and Evasion of TLR2-Mediated Innate Immunity

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