Enhancement of HIV-1 neutralisation by modulation of the virus envelope

• Main Author: Scott, Melanie
• Other Authors: McClure, Myra
• Published: Imperial College London 2009
• Subjects: 616.9
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516471

Despite over 25 years of research, the goal of producing an HIV-1 vaccine able to prevent infection has not been realised. Due to the limited immunogenicity of HIV-1 glycoproteins in vivo, this thesis explores the use of cholesterol depletion in increasing the antigenicity and immunogenicity of an whole-inactivated HIV-1 immunogen. The primary aim was to demonstrate that cholesterol depletion of HIV-1 could enhance antibody binding and viral neutralisation. The laboratory-adapted strain, HIV-1MN, was utilised to demonstrate effective cholesterol depletion of virus using the compound methyl-β-cyclodextrin (MBCD). A range of MBCD concentrations were explored to assess the effect of removing cholesterol on viral infectivity, morphology and protein composition of the virus. A 1mM MBCD concentration, which effected a 50% reduction in viral envelope cholesterol with little impact on viral structure and protein composition whilst retaining viral infectivity, was chosen to explore the effect of cholesterol depletion on virus antibody binding and neutralisation. Removal of cholesterol from the viral envelope increased antibody binding and neutralisation using a number of monoclonal antibodies, soluble CD4 (sCD4) and HIV-1 positive patient antisera. This concept was then extended to a pseudotyped primary isolate of HIV-1. Cholesterol depletion of this isolate demonstrated a more restricted enhancement of antibody binding and neutralisation of virus by monoclonal antibodies, sCD4 and homologous and heterologous HIV-1 infected patient antisera. A number of inactivating agents were then explored in the aim of creating a cholesteroldepleted, whole inactivated HIV-1MN immunogen that retained key conformational gp160 epitopes. This immunogen was then tested in a mouse model to investigate whether cholesterol depletion could enhance the immunogenicity of whole-inactivated HIV-1MN. Although measurement of antibody responses from pooled mouse sera indicated significant enhancement of humoral responses to cholesterol-depleted, wholeinactivated HIV-1MN, analysis of individual mouse responses to immunisation yielded more variable results.