M.Sc. / It is generally believed that the development of a completely effective vaccine for the human immunodeficiency virus (HIV) will likely require neutralizing antibodies that react with the diverse strains of cell-free forms of this virus, as well as induce cellular responses in the form of cytotoxic T-lymphocytes (CTL), to eliminate cell-associated virus. Vaccines based on viral envelope proteins attempt to induce the former response, whilst DNA/vector based approaches aim to induce CTL. The membrane proximal external region (MPER) of HIV-1 gp41 is a target of two broadly neutralizing human monoclonal antibodies, 2F5 and 4E10, and is an important lead for vaccine design. It is conserved among several strains of HIV-1, except for subtype C where restricted mutations are found, especially in the epitopes of 2F5 and 4E10. Mono- and polyvalent (homologous and heterologous) synthetic peptide constructs of the epitopes recognised by 2F5 and 4E10, based on HIV-1 subtype C, have been designed and their immunogenicity compared in this study. The peptide constructs, designated MPER 1 / 2, a / b, induced humoral immune responses in mice and rabbits with the use of adjuvants. The homologous constructs (designated a) induced better humoral immune responses than the heterologous versions (designated b) in small animals. However the antibodies generated in rabbits were not potent enough to neutralize isolates of HIV- 1. The induction of neutralizing antibodies may be addressed by further conformational considerations, as conjugation to an octameric lysine core was insufficient. The peptide constructs did induce proliferative and inflammatory immune responses in a murine model. Additionally, the peptide constructs were highly antigenic as neutralizing anti-HIV antibodies present in naturally infected sera were able to recognise and bind to the MPER peptides as antigen in ELISAs. This suggests that the peptide constructs may be of value for characterizing anti-MPER antibody responses in infected individuals. The constructs were further able to mimic the true representation of these regions in vivo, as human monoclonal antibodies 2F5 and 4E10 were able to recognize and bind 3 of the 4 constructs. The human anti-MPER antibodies as well as the recombinant monoclonal antibodies had a higher binding affinity for the heterologous constructs. The MPER constructs exhibited many beneficial characteristics and may therefore hold application as a component in HIV-1 preventative and therapeutic vaccination following further modification.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:8307 |
| Date | 28 April 2009 |
| Creators | Philippeos, Christina |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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