Thesis (Ph. D.)--University of Hong Kong, 2006.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (M. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (MTh(Practical Theology)--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M.D.)--University of Pennsylvania, 1800. / Dedicated to Benjamin Rush, M.D., and to Arthur May, M.D., the author's brother. Signatures: [A]⁴ B-C⁴ D1. Not in Blake. Film 633 reel 64 is part of Research Publications Early American Medical Imprints collection (RP reel 64, no. 1240). DNLM

Alzheimer’s disease is the most common cause of late-life dementia and the fourth leading cause of death in the developed world. The aetiology of AD has not yet been resolved. It has been suggested that AD could result from multifactorial process involving both a genetic predisposition and an exposure to environmental factors modulated by the biological aging process. To date, epidemiological and molecular genetic data have led to the identification of three genes, amyloid precursor protein (APP), presenilin 1 (PS1) and presenilin 2 (PS2) genes, which, when mutated, can cause an early onset form of AD. Genetic linkage studies and association studies have also shown that the ε4 allele of the apolipoprotein E gene increases risk for AD in a dose dependent manner in both early onset and late onset AD. Recently, it has also been suggested that environmental factors may interact with a genetic predisposition to modify the risk of AD. Extensive research is underway to identify environmental and genetic risk factors for this complex disease. Over 40 genes have been tested as AD candidates yet none has been clearly established as an AD risk factor. Currently scientists are investigating the interrelationship between various gene loci and how environmental factors could affect an individual’s susceptibility to AD. This study evaluated the genotoxicity of environmental agents such as hydrogen peroxide, cadmium chloride and γ radiation induced oxidative DNA damage in lymphocytes and within specific DNA sequences of APP (exon 15-18) and PS1 (exon 3-12) genes of AD patients and age-matched control subjects. As indicators of oxidative DNA damage, the frequencies of DNA strand breaks, oxidized pyrimidines and altered purines was assessed using the alkaline Comet assay modified with lesion-specific endonucleases, endo-III and fpg; and fluorescence in situ hybridisation. The number of APP and PS1 hybridisation spots per comet were used as an indicator of the extent of damage. The location of the hybridisation spots in the head or tail of the comet were recorded to further determine whether the gene of interest lies within or in the vicinity of a damaged region of DNA. With the alkaline Comet assay modified with endo-III and fpg, it was demonstrated that patients with AD had significantly increased levels of DNA strand breaks, oxidized pyrimidines and altered purines induced by hydrogen peroxide, cadmium chloride and γ radiation compared with control subjects (p<0.05). This was further confirmed by the fluorescence in situ hybridisation modification of the alkaline Comet assay by demonstrating a significant increase in the mean number of APP and PS1 gene hybridisation spots per comet in AD patients compared with control subjects. Moreover, the gene sensitivity index of APP and PS1 to hydrogen peroxide, cadmium chloride and γ radiation were found to be higher in AD patients than in control subjects. Taken together, our results suggest (i) that lymphocytes from patients with AD are sensitive to these environmental genotoxic agents and (ii) there was an overall increase in the mean number and sensitivity index of APP and PS1 genes to environmental genotoxic agents which might link a genetic cause to oxidative stress in peripheral cells of AD patients than in control subjects. Although the mechanisms by which these environmental agents induced oxidative DNA damage remained to be elucidated, our data suggest that increased oxidative stress is an inherent property of cells carrying genes associated with AD. / Dr. H. Abrahamse Mrs. J. V. Hind

No description available.

[No abstract available] / Science, Faculty of / Botany, Department of / Graduate

Includes bibliography. / This dissertation comprises an application of social marketing principles and techniques to AIDS prevention in the workplace. The overall research objective of this dissertation is to investigate the provisions which have been made for AIDS in companies in South Africa, and to gain an understanding of the "preventative AIDS provisions" which the respondents consider practical to implement in their workplace, in order to generate conclusions and recommendations. The research findings, discussions and conclusions highlight areas for future research.

Background Up to 59% of tuberculosis (TB)/human immunodeficiency virus (HIV) co-treated patients develop paradoxical TB-associated immune reconstitution inflammatory syndrome (TB-IRIS) after addition of antiretroviral (ARV) therapy to anti-tuberculous therapy (ATT). The course can be prolonged and the average mortality rate is 2% (75% for TB-IRIS involving the central nervous system (CNS)). Immune elements – including neutrophils - involved in the anti-Mycobacterium tuberculosis (Mtb) response are implicated in pathogenesis, which remains incompletely understood. Diagnosis is one of exclusion, no reliable laboratory markers exist, corticosteroid-mediated prophylaxis and therapy are only partially effective, and no treatment targets tissue damage. Disentangling cause and effect in complex disorders such as TB-IRIS requires techniques capable of interrogating complex biological systems. Neutrophils are the major circulating leukocyte population, the earliest innate system responders, and exhibit various unusual immunometabolic functional specialisations. Proteins represent the most functionally-proximal and commonly pharmacologically-targeted cellular biomolecules. Label-free high-performance liquid chromatography-coupled tandem mass spectrometry (HPLCMS/MS) is well-suited to differentially profiling the ex vivo neutrophil proteome in an unbiased manner, in order to investigate TB-IRIS predisposition and pathogenesis. Methods Applying first principles to existing human literature, the most parsimonious holistic hypothetical model regarding paradoxical TB-IRIS predisposition and pathogenesis was inferred. A clinical cohort of control (CTRL) and matched TB-IRIS case (IRIS) study participants was assembled. Demographic, clinical, and biochemical characteristics were analysed for statistically-significant differences and to identify potential risk/protective factors (relative risk (RR) with 95% confidence interval (CI)). A small group (n = 9) of TB-HIV- healthy volunteers (HVs) was also assembled. Phlebotomy occurred at two timepoints: just prior to ARV initiation (week 0) and at the typical time of IRIS manifestation (week 2). Neutrophils were isolated and lysed, proteins underwent on-filter protein trypsinisation, peptide salts and detergents were removed, and neutrophil-optimised HPLC-MS/MS was conducted. Spectra were submitted to MaxQuant for parent protein identification and quantitation. Comparisons of (a) CTRL0 and IRIS0 to HV (and resultant differences) identified class-differential impacts of partial ATT-treated coinfection (IRIS predisposition) and of (b) CTRL2 to CTRL0 and IRIS2 to IRIS0 (and resultant differences) identified class-differential impacts of ARV therapy (IRIS pathogenesis). Class-discriminating proteomic differences were visualised using principal components analysis (PCA), protein differential expression analysis was performed (including for detectable/undetectable and significantly differentiallyexpressed (SDE) proteins), and results informed differential functional profiling via gene ontology overrepresentation analysis (GO-ORA) and pathway activation state prediction. To address shortcomings of current knowledgebases and automated tools, a novel deep manual analysis approach focused on key inference-friendly proteins, convergent findings, and neutrophil-specific functional modules. Integrated findings extended the literature-derived TB-IRIS model, generating testable novel hypotheses, one of which was partially validated using live-cell fluorescence microscopy. Proteomic data were additionally analysed to detect Mtb proteins, preliminarily analyse variable post-translational modifications (PTMs) of interest, and identify candidate prognostic and diagnostic biomarkers. Finally, mechanistic hypotheses facilitated identification of novel potential prophylactic and therapeutic targets. Results (1) Literature suggests advanced TB/HIV-coinfection (including a higher Mtb/antigen load) as the major TB-IRIS risk factor. Attendant significant immunometabolic state perturbations include myeloid overactivation, metabolic stress (possibly including adaptogen depletion), a lack of regulatory receptors, impaired pro-inflammatory signal transduction, and impaired antigen clearance. These likely predispose to lytic cell death - including release of host- and pathogen-derived inflammatory/cytotoxic molecules and proteolytic enzymes - and less restrained/more abnormal inflammation as well as tissue damage, on restoration of HIV-suppressed inflammatory signalling pathways by ARV therapy. (2) Regarding the clinical cohort, a sample size of > 42 participants per characteristic-matched comparison class provides > 95% power to detect a two-fold change with 99% confidence. Cases exhibited known TB-IRIS risk factors, and largely expected white cell count (WCC), body mass index (BMI), and C-reactive protein (CRP) level changes in response to ARV therapy (e.g. WCC increase and BMI decrease). None of the few participants on alternate (efavirenz (EFV)- or tenofovir (TDF)-lacking) regimens developed TB-IRIS. Pre-ARV prednisone (or incidental antihistamine/anti-fungal) use was associated with a non-significantly decreased TB-IRIS risk. Interestingly, smoking is associated with a significant decrease in TB-IRIS risk by 60%. (3) Regarding sample processing and analysis, the average sample collection to neutrophil isolation interval was within recommended limits. Isolation yield exceeded 15 x 106 and 25 x 106 per sample in the CTRL and IRIS groups, respectively. Isolated neutrophil purity exceeded 80% in both groups; the few low-purity samples were excluded from subsequent proteomic analysis. Lysates from 5 x 106 neutrophils routinely yielded over 100μg total protein, tryptic digestion was efficient (on average < 96% missed cleavages), and equivalent peptide injection volumes yielded comparable total ion chromatogram (TIC) profiles and intensities. An average 23% spectral identification rate resulted in a total of 2532 protein group identifications, the deepest neutrophil proteome coverage achieved to date without pre-fractionation, representing ~12% of human protein coding genes, and ~25% of the detectable human proteome. Samples were analysed in two (randomised) batches, producing independent datasets A (N = 37) and B (N =74). Withindataset technical replicates exhibit excellent agreement in protein identities and quantities; betweendataset protein identities and functional inferences also exhibit excellent agreement. We identify a number of proteins apparently not known to be expressed by human neutrophils, as well as one predicted human protein never before observed empirically. Overall, parent pathways of level-altered proteins suggest perturbation of nine major neutrophil function modules at both time-points: (a) signal transduction, (b) pattern recognition receptor (PRR) and cytokine signalling, (c) the eicosanoid cascade, (d) neutrophil antimicrobial functions, (e) carbon-energy metabolism, (f) protein homeostasis, (g) integrated nitrogen-sulfur-B-vitamin and redox/xenobiotic/glyoxal metabolism, (h) gene expression, and (i) cytoskeletal dynamics. (4) Regarding impacts of partially ATT-treated co-infection (week 0), neutrophil proteomic profiles successfully distinguish between HV and IRIS0 or CTRL0. Many differences from HV are shared between IRIS0 and CTRL0 (i.e. driven by partially ATT-treated co-infection), but some are class-unique (i.e. driven by factors predisposing to or protecting from TB-IRIS). Findings are supported by a head-to-head comparison of the CTRL0 and IRIS0 proteomes, including changes suggesting: more prevalent type I IFN, TGFβ, and Th2-type cytokine signalling; poorer capacity for restraint of alternate complement activation; mitochondrial and oxidative stress (including proneness to necrosis); impaired function (e.g. microbicidality, TLR/IL-1R-MyD88-NFκB signalling, and caspase 1- mediated IL-1β and IL-18 maturation) of activated neutrophils; and enhanced lipid and upstream (but inhibited downstream) isoprenoid synthesis (including decreased steroidogenesis). Candidate biomarkers distinguish CTRL- and IRIS-class partially ATT-treated neutrophils from HV neutrophils and from each other. (5) Regarding impacts of ARV therapy (week 2), both IRIS and CTRL neutrophil proteomes exhibit significant changes in response to ARV therapy. Many changes are shared between IRIS and CTRL (i.e. driven by ARV therapy and declining viral load (VL)), but some are class-unique (i.e. driven by factors preventing/contributing to TB-IRIS pathogenesis). Findings are supported by a head-to-head comparison of the CTRL2 and IRIS2 proteomes, including changes suggesting: a slower decline in type I IFN signalling; increased inflammatory cytokine (e.g. IL-6, TNFα, and IFNγ) signalling and protease (e.g. MMP-8) activity; decreased sensitivity to immunoregulatory glucocorticoids and vitamin A; and increased mitochondrial, endoplasmic reticulum (ER), and oxidative stress. Candidate biomarkers distinguish CTRL- and IRIS-group ARV-exposed neutrophils from baseline and from each other. (6) Livecell fluorescence microscopy of HV neutrophils suggests that in vivo-equivalent levels of EFV rapidly alter mitochondrial, lysosomal, and aggresomal architecture in a manner consistent with organelle and protein folding stress, and suggesting cell death commitment. (7) Integrated neutrophil immunometabolic changes suggested by proteomic findings support and extend the biologically compelling literature-derived model. Model highlights include more advanced baseline TB/HIV (including higher type I IFN, TGFβ, and possibly Th2-type cytokine levels), with consequent impaired myeloid-mediated Mtb antigen clearance and depletion of cellular adaptogens. The resultant abnormal immunometabolic state produces myeloid cells less able to counteract metabolic stress and primed for less-restrained inflammation. Introduction of mitotoxic ARV drugs and rapid lifting of HIVmediated immune embargoes escalates myeloid metabolic (including oxidative) stress and overactivation (including via NLRC4, CASP4/5, TLR/IL-1R-MyD88-NFκB, and MAPK-AP1 signalling), producing - instead of Mtb clearance - inflammatory cell death with release of immune-activating and tissue-damaging host- and Mtb-derived molecules. Reactivation of Mtb lymphocyte memory responses likely only produces clinically-apparent inflammation (TB-IRIS) when multiple simultaneous but incompatible immune programmes (e.g. overzealous myeloid activity, Th1, Th2, Th17, and Treg) coexist. Based on this model, existing compounds with the potential for rational, safe, effective TB-IRIS prophylaxis/therapy are identified (e.g. glutathione, vitamins B-complex and A/D/E, rapamycin, and metformin) which may assist in restoring system homeostasis.