Browsing by Author "Wood, Natasha T."

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    The Influence of N-Linked Glycans on the MolecularDynamics of the HIV-1 gp120 V3 Loop
    (PLoS ONE, 2013) Wood, Natasha T.; Fadda, Elisa; Davis, Robert; Grant, Oliver C.; Martin, Joanne C.; Woods, Robert J.; Travers, Simon A.
    N-linked glycans attached to specific amino acids of the gp120 envelope trimer of a HIV virion can modulate the binding affinity of gp120 to CD4, influence coreceptor tropism, and play an important role in neutralising antibody responses. Because of the challenges associated with crystallising fully glycosylated proteins, most structural investigations have focused on describing the features of a non-glycosylated HIV-1 gp120 protein. Here, we use a computational approach to determine the influence of N-linked glycans on the dynamics of the HIV-1 gp120 protein and, in particular, the V3 loop. We compare the conformational dynamics of a non-glycosylated gp120 structure to that of two glycosylated gp120 structures, one with a single, and a second with five, covalently linked high-mannose glycans. Our findings provide a clear illustration of the significant effect that N-linked glycosylation has on the temporal and spatial properties of the underlying protein structure. We find that glycans surrounding the V3 loop modulate its dynamics, conferring to the loop a marked propensity towards a more narrow conformation relative to its non-glycosylated counterpart. The conformational effect on the V3 loop provides further support for the suggestion that N-linked glycosylation plays a role in determining HIV-1 coreceptor tropism.
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    Structural rearrangements maintain the Glycan Shield of an HIV-1 envelope trimer after the loss of a glycan
    (Nature Research, 2018) Ferreira, Roux-Cil; Grant, Oliver C.; Moyo, Thandeka; Dorfman, Jeffrey R.; Woods, Robert J.; Travers, Simon A.; Wood, Natasha T.
    The HIV-1 envelope (Env) glycoprotein is the primary target of the humoral immune response and a critical vaccine candidate. However, Env is densely glycosylated and thereby substantially protected from neutralisation. Importantly, glycan N301 shields V3 loop and CD4 binding site epitopes from neutralising antibodies. Here, we use molecular dynamics techniques to evaluate the structural rearrangements that maintain the protective qualities of the glycan shield after the loss of glycan N301. We examined a naturally occurring subtype C isolate and its N301A mutant; the mutant not only remained protected against neutralising antibodies targeting underlying epitopes, but also exhibited an increased resistance to the VRC01 class of broadly neutralising antibodies. Analysis of this mutant revealed several glycans that were responsible, independently or through synergy, for the neutralisation resistance of the mutant. These data provide detailed insight into the glycan shield’s ability to compensate for the loss of a glycan, as well as the cascade of glycan movements on a protomer, starting at the point mutation, that affects the integrity of an antibody epitope located at the edge of the diminishing effect. These results present key, previously overlooked, considerations for HIV-1 Env glycan research and related vaccine studies.
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    Trends in Genotypic HIV-1 Antiretroviral resistance between 2006 and 2012 in South African Patients receiving first- and second line antiretroviral treatment regimens
    (University of the Western Cape, 2013) Van Zyl, Gert U.; Liu, Tommy F.; Claassen, Mathilda; Engelbrecht, Susan; de Oliveira, Tulio; Preiser, Wolfgang; Wood, Natasha T.; Travers, Simon A.; Shafer, Robert W.
    South Africa's national antiretroviral (ARV) treatment program expanded in 2010 to include the nucleoside reverse transcriptase (RT) inhibitors (NRTI) tenofovir (TDF) for adults and abacavir (ABC) for children. We investigated the associated changes in genotypic drug resistance patterns in patients with first-line ARV treatment failure since the introduction of these drugs, and protease inhibitor (PI) resistance patterns in patients who received ritonavir-boosted lopinavir (LPV/r)-containing therapy.