Browsing by Author "Wood, N."

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Adaptive changes in HIV-1 subtype C proteins during early infection are driven by changes in HLA-associated immune pressure.
(Elsevier., 2009) Treurnicht, Florette K.; Seoighe, Cathal.; Martin, Darren Patrick.; Wood, N.; Abrahams, Melissa-Rose.; de Assis Rosa, Debra.; Bredell, Helba.; Woodman, Zenda.; Hide, Winston.; Mlisana, Koleka Patience.; Abdool Karim, Salim Safurdeen.; Gray, Clive M.; Williamson, Carolyn.
It is unresolved whether recently transmitted human immunodeficiency viruses (HIV) have genetic features that specifically favour their transmissibility. To identify potential “transmission signatures”, we compared 20 full-length HIV-1 subtype C genomes from primary infections, with 66 sampled from ethnically and geographically matched individuals with chronic infections. Controlling for recombination and phylogenetic relatedness, we identified 39 sites at which amino acid frequency spectra differed significantly between groups. These sites were predominantly located within Env, Pol and Gag (14/39, 9/39 and 6/39 respectively) and were significantly clustered (33/39) within known immunoreactive peptides. Within 6 months of infection, we detected reversion-to-consensus mutations at 14 sites and potential CTL escape mutations at seven. Here we provide evidence that frequent reversion mutations probably allows the virus to recover replicative fitness which, together with immune escape driven by the HLA alleles of the new hosts, differentiate sequences from chronic infections from those sampled shortly after transmission.
A case study of the capital structure decisions in practice in the real estates sector of the J.S.E.
(2003) Kamanzi, James.; Wood, N.
An ongoing debate in the corporate finance world concerns the question of a firm's optimal capital structure. More specifically, is there a way of dividing a firm's capital into debt and equity so as to maximize the value of the firm? From a practical standpoint, this question is of utmost importance for corporate financial officers. Yet, the academic literature has not been very helpful to provide clear guidance on practical issues. Except for a few theoretical models, there is a lack of literature concernmg how companies should decide their leverage ratios in practice. These models are unfortunately not applicable in real practice because of their inability to provide managers with a precise optimal leverage level. The purpose of this study concerns the practical matter of deciding the appropriate capital structure and the possibility of improvement for the companies. Specifically: How do the case companies decide their capital structure? Are their current capital stmctures optimal or is there room for improvement? To be able to examine these questions it was necessary to investigate companies that are as comparable as possible within the same industry. Different industries were identified based on the Johannesburg Stock Exchange industry classification and were analyzed for comparability issues. The real estate industry was found to experiences very similar business and has an opportunity to take more debt due to the nature of its asset structure. Three companies were selected from the property segment of the real estate industry based on their leverage ratios and companies with highest, medium, and lowest leverages in the industry were selected. Gold-edge was found to be the highest levered company in the industry, while Samrand and Putprop were found to be average and least levered in the industry respectively. The findings indicate that none of the companies uses capital structure models when deciding their capital structure. The case companies' capital structure indicates that Gold-edge's current capital structure is considered as close to optimal as possible while Putprop and Samrand current capital structure are not optimal and there is room for improvement.
Quantitating the multiplicity of infection with human immunodeficiency virus type 1 subtype C reveals a non-poisson distribution of transmitted variants.
(American Society for Microbiology., 2008) Abrahams, Melissa-Rose.; Anderson, Jeffrey A.; Giorgi, Elena E.; Seoighe, Cathal.; Mlisana, Koleka Patience.; Liu, Pinghuang.; Athreya, G. S.; Treurnicht, Florette K.; Keele, Brandon F.; Wood, N.; Salazar-Gonzalez, Jesus F.; Bhattacharya, Tanmoy.; Chu, Haitao.; Hoffman, Irving F.; Galvin, S.; Mapanje, Clement.; Kazembe, P.; Thebus, Ruwayhida.; Fiscus, Susan A.; Hide, Winston.; Cohen, Myron S.; Abdool Karim, Salim Safurdeen.; Haynes, Barton F.; Shaw, George M.; Hahn, Beatrice H.; Korber, Bette T. M.; Swanstrom, Ronald.; Williamson, Carolyn.
Identifying the specific genetic characteristics of successfully transmitted variants may prove central to the development of effective vaccine and microbicide interventions. Although human immunodeficiency virus transmission is associated with a population bottleneck, the extent to which different factors influence the diversity of transmitted viruses is unclear. We estimate here the number of transmitted variants in 69 heterosexual men and women with primary subtype C infections. From 1,505 env sequences obtained using a single genome amplification approach we show that 78% of infections involved single variant transmission and 22% involved multiple variant transmissions (median of 3). We found evidence for mutations selected for cytotoxic-T-lymphocyte or antibody escape and a high prevalence of recombination in individuals infected with multiple variants representing another potential escape pathway in these individuals. In a combined analysis of 171 subtype B and C transmission events, we found that infection with more than one variant does not follow a Poisson distribution, indicating that transmission of individual virions cannot be seen as independent events, each occurring with low probability. While most transmissions resulted from a single infectious unit, multiple variant transmissions represent a significant fraction of transmission events, suggesting that there may be important mechanistic differences between these groups that are not yet understood.