Antimicrobial peptides and virulence factors in meningococcal colonisation and disease
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
The Gram-negative bacterium Neisseria meningitidis is a transient commensal of the human nasopharynx, but occasionally causes life-threatening disease. During colonisation of its niche, N. meningitidis has to overcome innate immune defences, including the expression of antimicrobial peptides (AMPs). Meningococcal resistance to the host defence peptide LL-37 was investigated in Papers I and II. The polysaccharide capsule and lipopolysaccharide (LPS) were found to increase LL-37 resistance by inhibiting peptide binding to the bacteria. Further, N. meningitidis responded to sub-lethal doses of LL-37 by an increase in capsule biosynthesis. Intriguingly, adhesion to epithelial cells and tissues protected N. meningitidis from physiological concentrations of LL-37 and two other helical peptides. The protective effect was mediated by RhoA- and Cdc42-dependent host cell signalling and cholesterol-rich membrane microdomains. The host epithelium thus seems to play an active role in AMP resistance.
Cell-penetrating peptides (CPPs) are structurally related to AMPs, but are primarily employed for the delivery of membrane-impermeable molecules in vitro and in vivo. In Paper III, several of these peptides were screened for antimicrobial activity against N. meningitidis. The best candidate, transportan-10 (TP10), exhibited membrane-disruptive, bactericidal activity and decreased bacteraemia levels in a mouse model of meningococcal disease. Additionally, TP10 inhibited binding of LPS to macrophages, thereby neutralising its inflammatory effect. These dual effects of TP10 may potentially be harnessed for the treatment of invasive disease.
The role of the N. meningitidis polynucleotide phosphorylase (PNPase) homologue in pathogenesis was studied in Paper IV. PNPase-deficient meningococci were hyper-aggregative and resistant to normal human serum, and these phenotypes were associated with an accumulation of extracellular DNA on the pili and surface of the bacteria. Wild-type meningococci differentially regulated PNPase expression in contact with epithelial cells and in human serum, suggesting the dynamic regulation of PNPase levels during pathogenesis.
Place, publisher, year, edition, pages
Stockholm: Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University , 2014. , 68 p.
Neisseria meningitidis, antimicrobial peptide, LL-37, cell-penetrating peptide, resistance, polynucleotide phosphorylase
Research subject Molecular Bioscience
IdentifiersURN: urn:nbn:se:su:diva-99175ISBN: 978-91-7447-849-5OAI: oai:DiVA.org:su-99175DiVA: diva2:687624
2014-02-21, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Sørensen, Ole E., Docent
Jonsson, Ann-Beth, Professor
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.2014-01-302014-01-122014-01-22Bibliographically approved
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