MSc (Microbiology) / Department of Microbiology

University of Venda / MSc (Microbiology)

PhD / Department of Microbiology

MSc (Microbiology) / Department of Microbiology / See the attached abstract below.

PhD (Microbiology) / Department of Microbiology / High genetic diversity is a major contributory factor in the development of drug resistance, in addition to challenges in diagnosis and treatment monitoring in the therapeutics of human immunodeficiency virus (HIV) .Within the wide HIV-1 diversity, differences in mutational frequency, disease progression, drug response and transmission amongst HIV-1 subtypes have been shown. In spite HIV-1 subtype C (HIV-1C) being the most prevalent variant globally, none of the available drugs nor screening assays for inhibitory molecules have been developed targeting the genetics of this important subtype. This study therefore aimed to overexpress and biophysically characterize HIV-1C reverse transcriptase and protease to serve as reagents in the development of assays for routine screening of molecules inhibitory to HIV-1C. Heterologous expression of HIV-1C reverse transcriptase and protease isolates that are prevalent in South Africa was carried out in Escherichia coli (E. coli (BL21-DE3). The secondary and tertiary structures of the proteins were determined using, circular dichroism (CD) and fluorescence spectroscopy respectively. Thereafter, interaction studies to delineate interaction properties of natural products for possible inhibition of protease were conducted. Furthermore, in silico studies to determine binding interactions, further confirmed by in vitro binding assays of a pepsin inhibitor homolog (Bm-33) from Brugia malayi , against protease were also conducted. Expressed reverse transcriptase and protease from the globally prevalent HIV-1C were shown to be structurally and functionally intact for application in downstream HIV-1 inhibition assays. Interaction studies on the other hand revealed successful inhibition of the expressed HIV-1C PR with gallotanin. Furthermore, binding interactions of Bm-33 and HIV-1 PR revealed the first intermolecular interactions of the two molecules displaying possible inhibition of HIV-1 PR / NRF

The central problem for researchers of HIV-1 evolution is explaining the apparent design of the virus for causing pandemic infection in humans: understanding how HIV-1 spreads is key to halting the pandemic. Current knowledge of how HIV-1 spreads from host to host is based upon experimental observation and indirect inferences informed by theory. The hypothesis of this thesis is that diversity of HIV-1 around the time of transmission is important for viral adaptation to a new human host, rather than intrinsic superiority of particular strains found in infectious fluids from human donor hosts, and that studying recombination is important for understanding this behaviour. To demonstrate the apparent randomness of transmission, I test the null-hypothesis that hard selection accounts for between-host viral divergence in a rare case study of contemporaneous infection. I explain how the experimental data that I have generated and the analyses I have carried out address certain basic assumptions and predictions about HIV-1 transmission and may inform current strategies for vaccine design. Specifically, my approach contributes to the current literature on HIV-1, by investigating an alternative hypothesis to the single virion theory of sexual transmission and by characterizing the role of recombination in a pseudodiploid virus following multiple-infection.