Thesis (Ph. D.)--University of Chicago, Faculty of the School of Social Service Administration, 2002. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 296-314).

Thesis (M.A.)-University of KwaZulu-Natal, Durban, 2008. / Full text also available online. Scroll down for electronic link.

Thesis (MSD (EAP))--University of Pretoria, 2003.

published_or_final_version / Mathematics / Master / Master of Philosophy

published_or_final_version / Community Medicine / Master / Master of Public Health

Background Routine voluntary HIV screening has been found to be cost-effective in regions with undiagnosed prevalence > 0.1%. However, a large proportion of infected patients are still unaware of their status and presenting to care late, leading to greater risk s for infection. As expanded ART has been shown to be highly effective in improving patient health and reducing HIV viral load, a strategy of expanded screening with earlier initiation of ART may be effective at reducing the numbers of new infections. Aim A systematic review was carried out with the aim of understanding what drives the cost-effectiveness of expanded HIV screening at low prevalence rates. A thorough investigation of sensitivity analysis was done to determine if low prevalent regions can implement screening at good value for cost and how money should be spent to maximize benefits. Methods An extensive literature review of studies published in English between 1996 and 2010 were identified from various electronic databases, included gray literature search and hand search. A qualitative assessment of the literature was undertaken. Results Results of the analysis found that expanded screening can be cost-effective at undiagnosed prevalence rates below that of current recommendations. Factors of linkage to care, and benefits of reduced secondary transmissions through reduced risk behaviors had the most impact on models. Screening while maximizing benefits due to linkage to care and secondary transmissions can may be appropriate for low prevalence regions such as Hong Kong, however further analysis would be necessary. / published_or_final_version / Public Health / Master / Master of Public Health

R5-tropic HIV-1 is predominantly transmitted during unprotected sexual contacts, rendering CCR5 antagonist as an attractive agent not only for antiretroviral therapy but also for prevention. Here, we report two 1,3,3,4-tetrasubstituted pyrrolidine embodied compounds, TD-0232 and TD-0680, as novel small molecule CCR5 antagonists and investigate their specificities, potencies and underlying mechanisms. We found that both TD-0232 and TD-0680 inhibited a diverse group of R5-tropic HIV-1 and SIV strains in both single-cycle infectivity assays and live viral PBMC assays. When compared to other CCR5 antagonists, such as TAK-779 and the only FDA-approved Maraviroc, TD-0680 displayed the highest potency with EC50 values at the subnanomolar levels (range 0.09nM-2.29nM). TD-0232 and TD-0680, but not Tenofovir, a nucleoside reverse transcriptase inhibitor, completely blocked envelope-mediated cell-cell fusion and subsequent viral transmission. Critically, TD-0680 was potent at inhibiting the replication of a TAK-779/Maraviroc-resistant HIV-1 variant in PBMCs at a subnanomolar concentration. Interestingly, despite binding to a similar transmembrane pocket of CCR5, TD-0232 and TD-0680 functioned differently as revealed by site-directed mutagenesis and drug combination assays. Based on the sequence homology, we constructed a CCR5 molecule model using the crystallized CXCR4 as a template. By docking of CCR5 antagonists with CCR5, we identified a unique binding mode of TD-0680, which has not been described previously. TD-0680, with an exo-configuration, extended its interaction with the ECL-2 region of CCR5 in a protruding manner, thereby interrupting the interaction between the virus and its co-receptor more effectively. In an antibody recognition assay, we confirmed that TD-0680 had an enhanced inhibitory activity against the anti-ECL2 monoclonal antibodies binding. Furthermore, we investigated the antiviral activities of TD-0232 and TD-0680 that were formulated into a thermo-reversible acidic microbicide gel. Both drugs were stable in the acidic gels and could be released rapidly for long lasting and potent antiviral activities. Although human semen could enhance the infection of HIV-1, it did not seem to affect the potencies of the TD-0232 and TD-0680 gels. In summary, our findings suggest that TD-0232 and TD-0680 can be further developed not only as anti-HIV-1 agents for therapeutic purposes but also as potent microbicides for the prevention of sexual transmission of R5-tropic HIV-1. / published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

Acquired Immunodeficiency Syndrome (AIDS) and tuberculosis (TB) have posed diagnostic and therapeutic challenges globally. Nowadays, it is estimated that 34 millions people are living with Human Immunodeficiency Virus (HIV). About 2 millions of people die from AIDS-related causes currently in each year. Tuberculosis is the most common presenting illness and leading cause of death among AIDS patients. Emerging studies suggest that HIV and Mycobacterium tuberculosis (Mtb), the causative pathogen of TB, act synergistically to accelerate decline of immune functions and cause the death. Mtb infection usually remains latent. Only small portion of infected individuals develops active TB. However HIV infection boosts the risk of reactivation of TB and susceptibility to new Mtb infection. In contrast, Mtb infection dysregulates cytokines production and induces HIV viral replication. Although it is well-known that HIV and Mtb potentiate each other in disease development, mechanisms of interaction of the two pathogens remain not well-elucidated. The aim of this study is to investigate the interaction of HIV viral protein Tat with mycobacteria infection, which may provide insights in the interplay between HIV and Mtb infections. HIV viral transactivator protein, Tat, plays a critical role in HIV replication; and its induction of apoptosis in CD4+ T cells contributes to immune defects. In this study, Tat was demonstrated to dysregulate immune responses against mycobacteria such as autophagy, a tightly regulated bacterial clearance mechanism. With pretreatment of the primary human blood monocyte-derived macrophages with Tat, the interferon-γ (IFN-γ)-induced Signal Transducer and Activator of Transcription-1 (STAT-1) phosphorylation was suppressed. Inhibition of STAT-1 phosphorylation ultimately led to downregulation of autophagy-associated gene, microtubule-associated protein light chain 3 (LC3) expressions. Of note, Tat was demonstrated to inhibit the colocalization of Bacillus Calmette Guerin (BCG) and IFN-γ-induced autophagosomes under fluorescent microscopy examination. In addition to the inhibition of bactericidal autophagy, Tat was found to manipulate cytokines production. Tat was demonstrated to enhance mycobacteria-induced tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) production. TNF-α and IL-1β have been well-demonstrated in literatures that can limit bacterial growth. They, however, have been also shown as important contributors to the increase of HIV viral replication in HIV and mycobacteria coinfection. Mtb-induced TNF-α production can induce transcriptional activation of the HIV long terminal repeat (LTR) promoter while blocking of IL-1β production decreases HIV replication. Tat enhancement of these cytokines production may therefore contribute to the knowledge of the increased viral replication in HIV and mycobacteria coinfection. Furthermore, new microRNAs, up-and-coming fine-tuners of innate immunity, were discovered. MicroRNAs, a family of non-coding RNAs, can regulate gene expressions post-transcriptionally and control various developmental and cellular processes. They can target mRNAs of cellular signaling molecules, transcription factors or cytokines as to regulate the immunity. Herein, microRNA-1303, originally with unknown function, was shown to regulate mycobacteria-induced TNF-α production and affect the Tat enhancement of TNF-α production. Taken together, the results of this study demonstrated that HIV viral protein, Tat could dysregulate immune responses to mycobacteria. The study of the dysregulation may further elucidate the interplay between HIV and mycobacteria infections. / published_or_final_version / Paediatrics and Adolescent Medicine / Doctoral / Doctor of Philosophy

abstract / Microbiology / Doctoral / Doctor of Philosophy