The role of pneumolysin in pro-inflammatory mediator production

Search, Jennifer Julia (2002) The role of pneumolysin in pro-inflammatory mediator production. PhD thesis, University of Glasgow.

Abstract

Pneumolysin is a pore forming toxin produced by Streptococcus pneumoniae and is necessary for full virulence during pneumococcal infection. Pneumolysin monomers oligomerise in cell membranes and form pores which can lead to cell lysis or, at low concentrations, lead to production of pro-inflammatory mediators. We attempted to define the role of oligomerisation in pneumolysin-induced pro-inflammatory mediator production. Site directed mutagenesis was used to alter amino acid residues within the pneumolysin structure thought to be essential for oligomerisation. An assay was developed to detect oligomerisation by measuring changes in fluorescence in the environment of an extrinsic fluor, ANS. Contrary to expectations, the data presented here show that mutating these residues does not abolish oligomerisation of the toxin. We therefore have not been able to resolve the role of oligomerisation in mediator production. Evidence that the lytic activity of the toxin is involved is shown by use of a mutant toxin in which the lytic activity is abolished to less than 0.1%. Lytic concentrations of the toxin also stimulate much greater production of both nitric oxide and tumour necrosis factor from macrophages than sublytic concentrations. Experiments using the whole organism confirm the role of pneumolysin in mediator production by Streptococcus pneumoniae. These data have also revealed other interesting interactions between the pneumococcus and host cells that involve pneumolysin. Data from microarray experiments reported here confirm increased expression of several pro-inflammatory mediators previously reported to be induced by pneumolysin. Other mediators expected to show enhanced gene regulation were not confirmed. This highlights the complexity of these methods and the need for further research into these mechanisms. Data from the microarray and experiments using laser scanning cytometry confirm the ability of pneumolysin to induce apoptosis in macrophages. We have confirmed the importance of pneumolysin in the development of an inflammatory response and shown how it may be pivotal in the outcome of the host response to pneumococcal infection.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QH Natural history > QH301 Biology; Q Science > QR Microbiology > QR180 Immunology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Supervisor's Name: Mitchell, Professor Tim J.
• Date of Award: 2002
• Depositing User: Enlighten Team
• Unique ID: glathesis:2002-84636
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 01 Oct 2024 14:49
• Last Modified: 01 Oct 2024 14:49
• Thesis DOI: 10.5525/gla.thesis.84636
• URI: https://theses.gla.ac.uk/id/eprint/84636