Characterisation of novel TLR-dependent immunomodulators from tropical plant extracts

Thirlaway, Khalil (2018) Characterisation of novel TLR-dependent immunomodulators from tropical plant extracts. PhD thesis, University of Nottingham.

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Toll-like receptors (TLRs) recognise a wide range of molecular patterns, and are key in activation and coordination of the innate and adaptive immune responses. TLR ligands include pathogen-associated and damage-associated molecular patterns (PAMPs and DAMPs, respectively), as well as an increasing number of plant-derived ligands. Novel TLR ligands represent promising potential therapeutics, for example as vaccine adjuvants or selectively immunosuppressive drugs.

Exploiting Malaysia’s diverse and largely unexplored repertoire of endemic plant species, lyophilised extracts of leaf and bark tissue from various species were screened for stimulatory or inhibitory activity in four stably transfected HEK cell lines expressing TLR 2/1, 2/6, 4 and 5. Extracts showing significant changes in CXCL8 production relative to controls were fractionated to identify active components, and chemically modified to identify functional molecular groups. To better assess biological relevance of any effects, active extracts were tested for modulation of class-switching and proliferation in primary murine splenic B-lymphocytes.

Of the 21 extracts screened, three showing interactions with TLR2/6 were chosen for further analysis: 1402EtL and 1412EtB showed stimulatory activity and 1404EtL showed inhibitory activity. 1402EtL was insoluble in aqueous solution, which prevented further characterisation, but a >100kDa active fraction of 1412EtB and a 10-30kDa active fraction of 1404EtL were identified. Neither boiling nor acid-treatment affected the stimulatory activity of 1412EtB, but oxidation with metaperiodate eliminated activity. None of the three treatments affected the inhibitory activity of 1404EtL. In primary murine B-cells 1402EtL was found to induce IgG1 isotype switching and crude 1412EtB induced proliferation and upregulation of IgM expression. The acid-treated, boiled and >100kDa forms of 1412EtB produced a stronger proliferative and IgM response, as well as inducing IgG1 class switching. These data suggest that these plants represent promising candidates for development of novel TLR-mediated immunomodulatory pharmaceuticals.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Flynn, Robin J.
Haig, David
Pritchard, D.I.
Keywords: Immunology, Immunomodulation, Plant based medicine, Phytotherapy, Bioprospecting, TLR, Toll-like receptors, innate immunity, PRR, pattern recognition receptors
Subjects: Q Science > QR Microbiology > QR180 Immunology
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Veterinary Medicine and Science
Item ID: 52526
Depositing User: Thirlaway, Khalil
Date Deposited: 04 Apr 2019 14:06
Last Modified: 04 Apr 2019 14:06

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