The rational design of an HIV-1 vaccine immunogen able to induce potent, cross-reactive, neutralising antibodies remains one of the single greatest challenges in the field of vaccine research today. Roughly a dozen broadly neutralising monoclonal antibodies have been isolated to date, and their epitopes represent important vaccination targets. Interestingly, apart from three that identify over-lapping epitopes in gp41, all of the broadly neutralising monoclonal antibodies target epitopes apparent on different conformations of gp120 (including the epitopes of PG9/PG16). Thus the gp120 monomer remains the most ideal template for immunogen design. Recently, epitopes in the C3-V4 region of gp120 have been shown to be major targets for early strain-specific neutralising antibodies in subtype C infected individuals. Autologous neutralising antibodies identify vulnerable sites on the envelope, and understanding the nature of antigenic “hotspots” on gp120 will help to guide rational vaccine design. This study sought to confirm in four individuals that the C3-V4 epitope was in fact apparent on monomeric gp120, and thereafter to better characterise the nature of viral escape from these antibodies. Using magnetic beads coated with one of 16 different recombinant gp120 proteins it was confirmed that the C3-V4 response was aimed at a monomer-specific epitope in all four cases. In two instances these antibodies were shown to contribute to autologous neutralisation, while in a third the existence of quaternary structure specific antibodies that could not be adsorbed with monomeric gp120 made this link impossible. In the forth instance transfer of the C3-V4 region was shown to expose a normally occluded epitope in the CD4 binding site. This research also provided evidence for other epitopes for autologous neutralising antibodies in C3, overlapping with the CD4 binding site and V5. Lastly, by introducing relevant escape mutations into the parental recombinant gp120s and then comparing the ability of these proteins to adsorb out anti-C3 antibodies, it was shown that while these mutations conferred complete resistance to neutralisation they did not prevent the antibodies from binding to their respective epitopes. The extensive characterisation of C3-related epitopes such as those described in this research should no doubt contribute to the rational design of a gp120 based vaccine immunogen aimed at eliciting broad and potent neutralising antibody responses.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/11023 |
| Date | 17 January 2012 |
| Creators | Wibmer, Constantinos Kurt |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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