Die Interaktion mit Gehirnendothelzellen stellt ein zentraler Schritt in der Infektionspathogenese von Neisseria meningitidis dar. In dieser Promotionsarbeit konnte gezeigt werden, dass die Infektion von menschlichen Gehirnendothelzellen mit N. meningitidis zu einer transienten Aktivierung der sauren Sphingomyelinase (ASM) gefolgt von einer vermehrten Ceramidproduktion führt. Als Antwort auf die Infektion mit N. meningitidis kommt es zu einer vermehrten Präsentation der ASM und von Ceramiden an der äusseren Seite der Plasmamembran und zu einer Ausbildung von großen Ceramid-reichen Membran-Domänen, welche mit cortical plaque assoziierten Proteinen kolokalisieren. Bei dieser N. meningitids vermittelten Aktivierung der ASM spielt das bakterielle Aussenmembranprotein Opc sowie die Aktivierung der Phosphatidylcholin-spezifische Phospholipase C über die Interaktion von Opc mit Heparansulfat-Proteoglykane eine entscheidende Rolle. Die pharmakologische oder genetische Inhibition der ASM Funktion führt zu einer geringeren Invasivität der Meningokokken ohne dabei die Adhärenz zu beeinflussen. Im Einklang mit diesen Ergebnissen steht die Beobachtung, dass die geringere Invasivität von ausgewählten Isolaten des ST-11/ST-8 Komplex in menschlichen Gehirnendothelzellen direkt mit ihrer eingeschränkter Fähigkeit korreliert, die ASM zu aktivieren bzw. eine Ceramidproduktion zu induzieren. Schlussfolgernd ist die ASM Aktivierung und eine nachfolgende Ceramidproduktion essenziell für die Internalisierung von Opc-exprimierende Meningokokken in Gehirnendothelzellen und bietet einen Erklärungsansatz für die unterschiedliche Invasivität von verschiedenen N. meningitidis Stämmen. / The interaction with brain endothelial cells is central to the pathogenicity of Neisseria meningitidis infections. Here, we show that N. meningitidis causes transient activation of acid sphingomyelinase (ASM) followed by ceramide release in brain endothelial cells. In response to N. meningitidis infection, ASM and ceramide are displayed at the outer leaflet of the cell membrane and condense into large membrane platforms which also colocalize with cortical plaque associated proteins. The outer membrane protein Opc and phosphatidylcholine-specific phospholipase C that is activated upon binding of the pathogen to heparan sulfate proteoglycans, are required for N. meningitidis-mediated ASM activation. Pharmacologic or genetic ablation of ASM abrogated meningococcal internalization without affecting bacterial adherence. In accordance, the restricted invasiveness of a defined set of pathogenic isolates of the ST-11/ST-8 clonal complex into brain endothelial cells directly correlated with their restricted ability to induce ASM and ceramide release. In conclusion, ASM activation and ceramide release are essential for internalization of Opc-expressing meningococci into brain endothelial cells, and this segregates with invasiveness of N. meningitidis strains.

Thèse de doctorat : Enzymologie Moléculaire : Nancy 1 : 2008. / Titre provenant de l'écran-titre.

Thèse de doctorat : Génie des procédés et des produits : INPL : 2008. / Titre provenant de l'écran-titre.

Neisseria meningitidis is a causative agent of meningitis and septicaemia. Pili are one of the major virulence factors that contribute to the pathogenicity of N. meningitidis. Pili of Neisseria are type IV fimbriae composed primarily of thousands of identical pilin subunits. Pilin of N. meningitidis is post-translationally modified by trisaccharide, phosphorylcholine and -glycerophosphate. The genes involved in pilin expression, pilin glycosylation and phosphorylcholine modification are phase variable (high frequency ON/OFF switching of expression). The function of pilin post-translational modifications and their phase variable expression in host:pathogen interactions is unknown. The phase variable expression of glycosylation in bacteria has been proposed to function in bacterial adherence and immune avoidance. However, the function of pilin glycosylation in N. meningitidis is unclear. Phosphorylcholine is expressed in a number of respiratory organisms including P. aeruginosa (on teichoic acid), S. pneumoniae (on lipoteichoic acid) and H. influenzae (on LPS). Phosphorylcholine in these organisms is important in colonisation of the nasopharynx and invasion of the epithelium. Studies on N. meningitidis pilin post-translational modifications have been restricted by difficulties in purification of pilin protein. In this thesis, we evaluated current pilin purification methods and established an efficient method of purifying pilin from N. meningitidis by Flag-tag purification system. Flag-tag purified pilin is post-translationally modified. The LC-ESI/MS/MS analysis performed in this thesis using Flag-tag purified pilin successfully determined the phosphorylcholine post-translational modification sites. Based on the MS data and the mutagenesis analysis, phosphorylcholine is covalently linked to serine 157 and serine 160 of pilin. The colony immunoblot of a serine 157/160 to alanine mutant revealed that phosphorylcholine modifications of these sites on pilin are the only surface exposed phosphorylcholine and is responsible for binding to TEPC-15 (the monoclonal antibody which binds to phosphorylcholine). In this thesis, molecular modelling demonstrated that surface exposure of pilin phosphorylcholine could be altered by the phase variation of pilin glycosylation on the adjacent pilin monomer. Furthermore, the sites for phosphorylcholine modification are commonly observed in N. meningitidis strains but not in N. gonorrhoeae indicating the importance of phosphorylcholine in pathogenisis of N. meningitidis. In addition, the biosynthesis of phosphorylcholine for pilin post-translational modification still remains a mystery. Bacteria generally obtain choline from the environment. In this thesis, we demonstrated that pilin phosphorylcholine post-translational modification could be endogenously synthesized in N. meningitidis. In summary, this thesis describes the purification method of obtaining pure post-translationally modified pilin from N. meningitidis. The phosphorylcholine post-translation modification sites on pilin have been determined and showed the importance of these sites in antibody binding specificity.

Würzburg, Universiẗat, Diss., 2008.

Würzburg, Univ., Diss., 2007. / Zsfassung in engl. Sprache.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.

Würzburg, Univ., Diss., 2005. / Erscheinungsjahr an der Haupttitelstelle: 2004

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Made available in DSpace on 2014-09-09T12:30:35Z (GMT). No. of bitstreams: 2 license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) 21.pdf: 2527128 bytes, checksum: a04af2c4a06eeb1f926017f8e317075e (MD5) Previous issue date: 2012 / Nesse trabalho, foram desenvolvidas metodologias aplicadas ao controle de qualidade de vacinas antimeningocócicas sorogrupo B. Este desenvolvimento se deu com base na avaliação do perfil protéico das preparações vacinais. Para isso, foram desenvolvidas condições de análise para a identificação e caracterização dos antígenos vacinais por eletroforese bidimensional e espectrometria de massas. Muitos antígenos importantes imunologicamente foram identificados e outros antígenos com menor importância também foram caracterizados por espectrometria de massas. Para a avaliação imunológica das preparações vacinais foi produzido um anticorpo policlonal anti-OMV. Esse anticorpo foi capaz de identificar os antígenos majoritários imunologicamente presentes nas preparações. Além do conteúdo do perfil proteico, foi feita a avaliação do conteúdo de LOS em preparações vacinais por metodologia físico-química. A cadeia o-específica do LOS é formada por um oligossacarídeo formado por unidades que se repetem de um açúcar de 8 carbonos denominado KDO (ácido 2-ceto-3-deoxioctulosonico).O KDO funciona como marcador químico da estrutura do LOS e a sua dosagem foi realizada por cromatografia líquida de alta eficiência por troca iônica com detecção amperométrica pulsada. Essa metodologia foi validada frente aos requisitos do INMETRO, e apresentou resultados satisfatórios para método de determinação quantitativa. As metodologias desenvolvidas foram muito importantes para a garantia do direito à saúde, uma vez que é responsabilidade das autoridades sanitárias nacionais assegurarem que os imunobiológicos disponíveis no Brasil, de origem nacional ou não, sejam seguros, de qualidade e eficácia comprovadas, já que a garantia da qualidade dos imunobiológicos se deve, dentre outros motivos, ao fato de que tais produtos são aplicados em grupos de pessoas sadias e as campanhas expõem toda uma faixa etária da população ao insumo. / In this work methodologies for meningococcal serogroup B vaccines were developed. The basic analyses were the protein profile by electrophoresis. For that, spefic conditions for antigen characterization by two dimensional electrophoresis and mass spectrometry were developed. Many of the most important antigens were identified by mass spectrometry, as also some minor antigens. For a immunological evaluation of vaccine preparations, polyclonal antibodies against outer membrane vesicles (OMVs). These antibodies recognize major antigens in the preparation. The content of lipoligosaccharide (LOS) in the preparations were also evaluated. O-specific chain of LOS has a 8 carbon sugar called 2-keto-3-deoxioctolunosic acid (KDO). KDO is a chemical marker of LOS structure; KDO was analyzed using high performance anion exchange chromatography of pulsed amperometric detection. This methodology was validated using INMETRO parameters; It is suitable for quantitative analysis. All developed methodologies are important to heath warranty, since vaccines efficacy, safety and quality are under the responsibility of health authorities in Brazil. Quality in vaccines is very important, since these products are used in a healthy age group of the population.