title: Neutrophil extracellular traps in the host defense against sepsis induced by Burkholderia pseudomallei (melioidosis).
abstract: BACKGROUND
  Neutrophil extracellular traps (NETs) are a central player in the host response to bacteria: neutrophils release extracellular DNA (nucleosomes) and neutrophil elastase to entrap and kill bacteria. We studied the role of NETs in Burkholderia pseudomallei infection (melioidosis), an important cause of Gram-negative sepsis in Southeast Asia.
  
  
  METHODS
  In a prospective observational study, circulating nucleosomes and neutrophil elastase were assayed in 44 patients with Gram-negative sepsis caused by B. pseudomallei (melioidosis) and 82 controls. Functional assays included human neutrophil stimulation and killing assays and a murine model of B. pseudomallei infection in which NET function was compromised using DNase. Specified pathogen-free 8- to 12-week-old C57BL/6 mice were sacrificed post-infection to assess bacterial loads, inflammation, and pathology.
  
  
  RESULTS
  Nucleosome and neutrophil elastase levels were markedly elevated in patients compared to controls. NETs killed B. pseudomallei effectively, and neutrophils stimulated with B. pseudomallei showed increased elastase and DNA release in a time- and dose-dependent matter. In mice, NET disruption with intravenous DNase administration resulted in decreased nucleosome levels. Although DNase treatment of mice resulted in diminished liver inflammation, no differences were observed in bacterial dissemination or systemic inflammation.
  
  
  CONCLUSIONS
  B. pseudomallei is a potent inducer of NETosis which was reflected by greatly increased levels of NET-related components in melioidosis patients. Although NETs exhibited antibacterial activity against B. pseudomallei, NET formation did not protect against bacterial dissemination and inflammation during B. pseudomallei-induced sepsis.
authors.affiliation: Center for Experimental and Molecular Medicine (CEMM), Academic Medical Center, Meibergdreef 9, Room G2-132, Amsterdam, 1105 AZ, The Netherlands, h.k.dejong@amc.uva.nl.
authors.forename: Hanna K
authors.initials: HK
authors.lastname: de Jong
authors.forename: Gavin Ckw
authors.initials: GC
authors.lastname: Koh
authors.forename: Ahmed
authors.initials: A
authors.lastname: Achouiti
authors.forename: Anne J
authors.initials: AJ
authors.lastname: van der Meer
authors.forename: Ingrid
authors.initials: I
authors.lastname: Bulder
authors.forename: Femke
authors.initials: F
authors.lastname: Stephan
authors.forename: Joris Jth
authors.initials: JJ
authors.lastname: Roelofs
authors.forename: Nick Pj
authors.initials: NP
authors.lastname: Day
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Peacock
authors.forename: Sacha
authors.initials: S
authors.lastname: Zeerleder
authors.forename: W Joost
authors.initials: WJ
authors.lastname: Wiersinga