Identification of migR, a Regulatory Element of the Francisella tularensis Live Vaccine Strain iglABCD Virulence Operon Required for Normal Replication and Trafficking in Macrophages

Blake W Buchan; Ramona L McCaffrey; Stephen R Lindemann; Lee-Ann H Allen; Bradley D Jones

doi:10.1128/IAI.00229-09

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Identification of migR, a Regulatory Element of the Francisella tularensis Live Vaccine Strain iglABCD Virulence Operon Required for Normal Replication and Trafficking in Macrophages

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Identification of migR, a Regulatory Element of the Francisella tularensis Live Vaccine Strain iglABCD Virulence Operon Required for Normal Replication and Trafficking in Macrophages

Blake W Buchan, Ramona L McCaffrey, Stephen R Lindemann, Lee-Ann H Allen and Bradley D Jones

Infection and immunity, Vol.77(6), pp.2517-2529

06/2009

DOI: 10.1128/IAI.00229-09

PMCID: PMC2687360

PMID: 19349423

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Abstract

Francisella tularensis , the etiological agent of tularemia, is capable of infecting a wide range of animals and causes a severe, lethal disease in humans. The pathogen evades killing by cells of the innate immune system utilizing genes encoding a pathogenicity island, including iglABCD , and instead utilizes these cells as a niche for replication and dissemination to other organs within the host. Regulators of the igl genes (e.g., MglA, SspA, FevR and PmrA) have been identified, but environmental stimuli and mechanisms of regulation are as yet unknown and are likely to involve additional gene products. In this work, we more closely examine the roles that environmental iron and the ferric uptake repressor protein (Fur) play in the regulation of the iglABCD operon. We also used a genetic approach to identify and characterize a new regulator of the igl operon, designated migR ( m acrophage i ntracellular g rowth r egulator; FTL_1542). Quantitative real-time reverse transcription-PCR in a site-directed migR mutant confirmed the reduction in the number of iglC transcripts in this strain and also demonstrated reduced expression of fevR . Comparison of the migR and fevR mutants in monocyte-derived macrophages (MDMs) and epithelial cell lines revealed a reduced ability for each mutant to grow in MDMs, yet only the fevR mutant exhibited impaired replication in epithelial cell lines. Confocal analysis of infected MDMs revealed that although neither mutant reached the MDM cytosol, the fevR mutant was trapped in lamp-1-positive phagosomes, whereas the migR mutant resided in mature phagolysosomes enriched with both lamp-1 and cathepsin D. Disruption of migR and fevR also impaired the ability of F. tularensis to prevent neutrophil oxidant production. Thus, we have identified migR , a gene that regulates expression of the iglABCD operon and is essential for bacterial growth in MDMs and also contributes to the blockade of neutrophil NADPH oxidase activity.

Molecular Pathogenesis

Details

Title: Subtitle: Identification of migR, a Regulatory Element of the Francisella tularensis Live Vaccine Strain iglABCD Virulence Operon Required for Normal Replication and Trafficking in Macrophages
Creators: Blake W Buchan - Departments of Microbiology
Ramona L McCaffrey - Departments of Microbiology
Stephen R Lindemann - Departments of Microbiology
Lee-Ann H Allen - Departments of Microbiology
Bradley D Jones - Departments of Microbiology
Resource Type: Journal article
Publication Details: Infection and immunity, Vol.77(6), pp.2517-2529
DOI: 10.1128/IAI.00229-09
PMID: 19349423
PMCID: PMC2687360
NLM abbreviation: Infect Immun
ISSN: 0019-9567
eISSN: 1098-5522
Publisher: American Society for Microbiology (ASM)
Language: English
Date published: 06/2009
Academic Unit: Microbiology and Immunology; Infectious Diseases; Internal Medicine
Record Identifier: 9984083881002771

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