published_or_final_version / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Microbiology / Master / Master of Philosophy

published_or_final_version / abstract / Surgery / Master / Master of Philosophy

published_or_final_version / abstract / Pathology / Master / Master of Philosophy

published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Philosophy

Twenty-two subjects with chronic/recurrent Epstein-Barr Virus (EBV) infection were compared with 22 controls to assess cognitive dysfunction. Subjects were compared on 15 measures of cognitive functioning from the Boston Diagnostic Aphasia Examination, Perceptual Speed, Wechsler Adult Intelligence Scale-Revised, Finger Tapping Test, Stroop Test, Trail-Making Test, Wisconsin Card Sorting Test and Revised Wechsler Memory Scale. They also were compared on measures of depression including the Beck Depression Inventory, Minnesota Multiphasic Personality Inventory (MMPI) depression subscale and SCL-90-Revised depression subscale. Group differences were assessed using discriminant analysis. Only some measures were included in this analysis, i.e. percent retention on Visual Reproduction and Logical Memory subtests of the Revised Wechsler Memory Scale, differential between time scores and between error scores on conditions three and two of the Stroop Test and total number of errors and perseverative errors on the Wisconsin Card Sorting Test. The Beck Depression Inventory was included to statistically remove depression effects from cognitive performances. Remaining measures were administered for exploratory and/or comparative purposes only. Results from discriminant analysis revealed significant group differences on the Beck, but not on any cognitive measure either before or after removal of depression effects. However, direction of group differences on cognitive measures occurred as expected. Also, a post-hoc multivariate analysis of variance revealed significant group differences on MMPI scales 1, 2 and 3 with EBV subjects showing higher elevations. Significant group differences also occurred on MMPI scale 7. Two categories of explanation for results are offered. The first suggests that cognitive deficits were missed due to shortcomings in study design. Remaining hypotheses address the possibility that no cognitive deficits occur with chronic/recurrent EBV infection. Suggestion for why EBV patients complain of cognitive deficits include discussion of hysteroid tendencies and intensification of sensations by a focus on somatic processes. The usefulness of assuming a multifactorial basis for symptoms associated with chronic/recurrent EBV infection, and the importance of abandoning the either/or approach of earlier investigators to hypothesizing about etiology, are discussed.

The vitamin D receptor (VDR) is a transcription factor mediating genomic responses to the biologically active form of vitamin D, 1,25(OH)2D3, a key modulator of the immune system. Knowledge on how these polymorphisms modulate the vitamin D endocrine system and confer risk of disease is hindered by the fact that several of the associated allelic variants are located in introns or are synonymous and likely serve as markers within an extended haplotype covering disease-causing alleles. The functional relevance of VDR polymorphisms need to be studied in the context of the haplotype, comparing haplotypes with the process of DNA transcription, protein levels and biological function. These functional studies should be performed using techniques reflecting the in vivo, naturally occurring milieu as close as possible. VDR has several known allelic variants including a FokI restriction fragment length polymorphism in exon II, BsmI and ApaI polymorphisms in the intron VIII, and a synonymous TaqI variant in exon IX. The aim of the current study was the identification of sequence variants in VDR, to define haplotype patterns in the Caucasian population and to understand the functional consequences of single nucleotide polymorphisms (SNPs) and haplotypes. Methods: EBV transformed B-lymphocyte cell lines, from twenty-three individuals, within the Caucasian population were established. Polymorphisms and haplotypes in VDR were identified by genotyping and sequencing. Quantification of the VDR protein level measured with flow cytometry was studied together with the genotype and haplotype data to determine possible influence of genotypes or haplotype and VDR protein levels. Biological function was analysed by the percentage inhibition that each individual experienced in the presence of 1,25(OH)2D3, measured by the Alamar Blue assay and the Trypan blue dye exclusion method. Results: The results showed thatVDR genotypes and haplotypes may not influence VDR protein level although certain genotypes and haplotypes significantly influenced biological function. It was proposed that VDR variants may account for significant influences on cellular responsiveness to 1,25(OH)2D3 as mediated by VDR. Conclusions: The findings of the current study suggest that individual SNPs and haplotypes of VDR influences quality of the repose in the presence of 1,25(OH)2D3, rather than quantity of the VDR levels. This knowledge may permit a rational choice of polymorphisms to use in epidemiology studies or improve our understanding of the significance of VDR genetic polymorphisms on biological function. Keywords: functionality, polymorphism, haplotype, vitamin D receptor, VDR, 1,25(OH)2D3, structure-function analysis, biological responsiveness. / Prof. L. Bornman

<p>Epstein-Barr virus (EBV) is a ubiquitous human pathogen that establishes a lifelong latent infection in over ninety percent of all adult humans worldwide. While typically benign, EBV has been causally associated with a number of human malignancies in the settings of immune suppression, genetic, and/or environmental factors. While a highly successful pathogen based on prevalence, the ability of the virus to immortalize human B cells (a stage of infection thought to be critical for the establishment of latency) is quite poor. We hypothesize that the interactions between the virus and the human host early after infection are ultimately important for the outcome of viral latency establishment. To answer this question we broadly profiled primary human B cells at both early and late times after EBV infection to assay both host mRNA expression and the host-driven response to apoptotic stimuli. We found that EBV infection induces host gene expression signatures early after infection that are functionally distinct from the gene expression program late after infection. These studies also led to the novel discovery that viral gene expression is controlled differently early after infection, including the delayed expression of a viral protein that is critical for the establishment of latency. Furthermore, we have also shown that EBV can use a single viral protein to alter and repress host apoptotic sensitivity in the face of an anti-viral apoptotic response.</p> / Dissertation