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Cellular activating properties and morphology of membrane-bound and purified meningococcal lipopolysaccharide

Department of Pediatrics, UllevÅl University Hospital, Oslo, Norway, a.k.bjerre{at}ioks.uio.no

Berit Brusletto

Department of Clinical Chemistry, UllevÅl University Hospital, Oslo, Norway

Einar Rosenqvist

Department of Vaccinology, National Institute of Public Health, Oslo, Norway

Ellen Namork

Department of Environmental Medicine, National Institute of Public Health, Oslo, Norway

Peter Kierulf

Department of Clinical Chemistry, UllevÅl University Hospital, Oslo, Norway

Reidun Øvstebø

Department of Clinical Chemistry, UllevÅl University Hospital, Oslo, Norway

Gun-Britt Joø

Department of Clinical Chemistry, UllevÅl University Hospital, Oslo, Norway

Petter Brandtzæg

Department of Pediatrics, UllevÅl University Hospital, Oslo, Norway

Neisseria meningitidis, the cause of epidemic meningitis and acute lethal sepsis, synthesizes surplus lipopolysaccharides (LPSs) during growth, which are released as outer membrane vesicles (OMV) or `blebs'. Meningococcal disease severity is related to plasma LPS levels. We have compared the biological activities of native outer membrane vesicles (nOMV) to those of purified Nm-LPS (Nm-LPS) and LPS-depleted OMV (dOMV) prepared from N. meningitidis. The LPS content of nOMV was determined spectrophotometrically by quantifying KDO and by silver-stained SDS-PAGE gels. The morphology of the preparations was studied by transmission electron microscopy. The Limulus amoebocyte lysate (LAL) assay was used to quantify LPS in the plasma solutions. The preparations were diluted in endotoxin-free heparin plasma to equal amounts of LPS (w/w) in the range 50—5000 pg/ml. The biological reactivity was tested by: (i) a monocyte target-assay (monocyte purity 96%); and (ii) a whole blood model, measuring the secretion of TNF- and IL-6 induction of procoagulant activity in monocytes (PCA). In both models, nOMV induced dose-dependent cell responses (TNF-, IL-6, PCA) similar to purified Nm-LPS, whereas dOMV induced minimal responses. However, LAL activity was significantly higher for nOMV than for purified Nm-LPS and dOMV. The cellular responses of purified Nm-LPS and nOMV were reduced (>95%) by a specific anti-CD 14-antibody.

Journal of Endotoxin Research, Vol. 6, No. 6, 437-445 (2000)
DOI: 10.1177/09680519000060060501


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