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Title: Role of antibodies specific for the V3 region of gp120 in HIV-1 infection
Author: Robertson, Carole Anne
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1993
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On infection with HIV-1, the host exerts a highly specific immune response against the virus. Despite this, HIV-1 is able to persist in the host, resulting in the gradual deterioration of the immune system, leading to opportunistic infections characteristic of HIV-infection and ultimately death of the individual. To elucidate the mechanisms involved in the pathogenesis and persistence of the virus, it is important to understand what role if any, the immune response generated against the virus has in the control of HIV-1 infection or progression to disease. This thesis describes the development of branched peptides for use in the detection of specific antibodies and describes two studies measuring the antibody responses of HlV-1 infected individuals against the V3 immunodominant region of HIV-1 gp120. Branched peptides had previously been shown to be more immunogenic in rabbits and can detect antibodies at lower concentrations than can the equivalent monomeric peptides. The initial work described in this thesis, was designed to further characterise the observed increased sensitivity of branched peptides, to investigate the basis for it and to optimise branched peptides for use as serodiagnostic reagents. A series of experiments were performed to test the effect of varying the distance between the epitope and the core by introducing glycine spacers. The sensitivity of branched peptides in detection of specific antibodies was also compared with that of the native protein. Two systems were studied. The first, involved the HSV-1 UL42 protein and reactive monoclonal antibody Z1F11. The second, involved a peptide derived from the third hypervariable region (V3) of the HIV-1 gp120 protein. These experiments clearly demonstrate that the progressive addition of glycine spacers between the reactive epitope in UL42 and the polylysine core increased the reactivity of the branched peptides with Z1F11. In addition , optimal reactivity of the UL42 peptides with monoclonal antibody Z1F11, was observed with the addition of four or five glycine residues and further addition of glycine residues did not significantly increase the sensitivity of these peptides. Comparison of the reactivity of the branched peptide with a five glycine spacer and the native UL42 protein demonstrated that both were equal in reactivity with monoclonal antibody ZIFII, The branched peptide derived from the V3 region of HIV-1 gp120 was eight-fold more sensitive than the native protein in detection of antibodies in the sera of HIV-1 infected individuals. The second study presented in this thesis was undertaken to investigate whether the levels and affinities of antibodies present in infected mothers, directed against the V3 region of HIV-1 gp120 correlated with a lack of transmission of the virus from mother to child as had been previously reported. To do this, a retrospective study of the antibody responses in the sera taken from a cohort of seven mothers who transmitted HIV-1 to their children and 20 who did not, was performed. Maternal sera were titrated in a series of doubling dilutions and tested in an ELISA against both a V3 branched peptide encompassing the entire V3 loop region (amino acids 297-330) and a branched peptide containing an immunodominant region of gp41 (amino acids 596-614). Anti- gp41 litres were used to normalise the anti-V3 litres. Maternal sera were also screened for the presence of antibodies that bind to the V3 peptide with high affinity, using an antigen limited ELISA, in which the monomeric V3 peptide was titrated in a series of dilutions and screened for reactivity against the sera. A high affinity antibody would be detectable in ELISA at low peptide concentrations. No differences were observed in either litres or affinities of maternal antibodies to the V3 sequence from transmitters and non transmitters of HIV-1 to their children.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available