Rosenheim, Joshua;
(2024)
Variation in beta-defensin expression in the control of Mycobacterium tuberculosis.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis (Mtb) and remains a leading cause of death by an infectious agent worldwide. The intracellular survival and replication of Mtb within macrophages is a determinate of Mtb persistence and pathogenesis. Our understanding of the physiological mechanisms behind human macrophage restriction of Mtb remains limited. Beta-defensins are antimicrobial peptides proposed to mediate antimicrobial restriction of Mtb. I investigated their induction and cellular source in the tuberculin skin test (TST) as an in vivo human experimental challenge model. This model revealed striking inter-individual variation in expression of beta-defensins independent of interferon-gamma (IFNγ). To elucidate the causes of expression variation in TST RNA- sequencing data, genome-wide single nucleotide polymorphism array profiling, gene modules analysis, and typing of genetic copy number were used. These data attributed inter-individual variation in expression to both differences in genetic copy number and variation in cytokine signalling upstream of beta-defensins. Beta-defensins are expressed by epithelial and myeloid cells, but it was not known which cell types were producing beta-defensins in vivo during anti- Mtb immune responses. To address this knowledge gap, single cell RNA-sequencing (scRNA-seq) and spatial gene expression with RNAscope fluorescence in situ hybridisation (FISH) were employed, revealing inducible expression exclusively limited to epithelial cells. Publicly available scRNA-seq and assay for transposase-accessible chromatin using sequencing (ATAC-seq) data were interrogated to support conclusions. Whether beta-defensins represent a physiologically important mechanism of antimicrobial defence against Mtb required further study. Using a fluorescent Mtb-infection model, I quantified intracellular and extracellular Mtb growth in human monocyte-derived macrophage (MDM) culture by flow cytometry. I demonstrated variable production of beta-defensins by airway epithelial cells in vitro and found no effect of secreted beta-defensins on macrophage control of Mtb. Taken together these data suggest beta-defensins do not contribute towards antimicrobial restriction of Mtb early during infection in humans.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Variation in beta-defensin expression in the control of Mycobacterium tuberculosis |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Infection and Immunity |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10198829 |
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