Interactions between the Neisseria meningitidis and its human host

• Main Author: Azimi, Sheyda
• Published: University of Nottingham 2015
• Subjects: 616.9
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.718673

Neisseria meningitidis colonises the nasopharyngeal epithelial cells with no symptoms. Bacteria occasionally cross the epithelium and access the deeper tissue and bloodstream. The exact mechanism triggering the commensal bacteria to become virulent is not fully understood. To study the possible effects of the interaction of whole meningococcal cells with various pro-inflammatory cytokines ELISAs were performed. These showed diverse levels of binding of meningococci to tested cytokines. The pilQ, pilE deficient N. meningitidis used in ELISA to study the role of the Type IV Pili (TFP) in interaction of bacteria with IL-8 and TNF-a. There was a significant decrease in the binding levels of meningococcal cells to both IL-8 and TNF-a in a pilQ mutant (p=0.0002 and p<0.0001) compared to the wild type. Meningococci binding to TNF-a and IL-8 was slightly inhibited after adding various carbohydrates moiety of Lewis antigens. Mutants of glycosyl transferases responsible for TFP glycosylation were tested in ELISA to examine the possible effects on interaction with cytokines. There was a significant decrease in binding of these mutants both to IL-8 and TNF-a (p<0.0001) compared to the wild type meningococci. This observation suggested that the meningococcal binding to tested cytokines is mediated by 0-glycosylated components of TFP. We further investigated the possible effects of cytokine treatment on regulation of meningococcal gene expression by transcriptome analysis. The data derived from transcriptome analysis showed differential expression of 473 genes in response to IL-8 and 1080 genes in response to TNF-a compared to the control untreated meningococci. As part of this study the possible role between meningococci cells and Fibroblast Growth Factor Receptor 1 (FGFR1) interaction with endothelial cells forming the blood brain barrier (BBB) was investigated. Human brain microvascular endothelial cells (HMBECs) showed expression of FGFR1 lllc and FGFR3 lllb in these cells. Infection of HBMECs and following confocal microscopy studies showed that activated FGFR1 is recruited by meningococcal colonies on the surface of HBMECs and in the cytoplasm by internalised meningococci. This study showed that optimal expression and activation of FGFR1 plays an important role in the invasion of N. meningitidis into HBMECs as FGFR1 siRNA transfection of HBMECs and chemical inhibition of FGFR1 cause significant reduction in the number of meningococci invaded into these cells (p=0.0003 and p=0.0005 respectively). ELISA studies using the extracellular domain of FGFR1 showed a direct and specific interaction between meningococci FGFR1 lllc as it was significantly higher than the binding of N. lactamica and N. polysacchariae (p=0.0198 and p=0.0236; n=3) and two other meningeal pathogens, H. influenzae and S. pneumoniae. The significant decrease in the binding levels of pilQ. mutant to FGFR1 compared to the wild type strain suggests that binding of meningococci to FGFR1 is pili mediated.