Characterisation of subtype C HIV-I envelope glycoproteins and their recognition by llama antibody fragments.
Doctoral thesis, UCL (University College London).
Subtype C HIV-1 is currently responsible for the majority of new infections in the world, particularly in parts of Africa where the adult prevalence rate is as high as 15%. In the absence of a viable vaccine in the near future, the study of new neutralising antibodies that can inhibit virus entry is urgently needed. To understand the subtype C HIV-1 envelopes, the env gene was cloned directly from 15 patient plasma samples obtained from a few countries in Africa and in the UK, and 18 replication-competent chimeric viruses were created. These envelopes were then characterised and compared with other envelopes in standard reference panels. We then exploited the unique properties of llama heavy-chain antibodies to create antibody fragments (VHH) that can recognise HIV-1 envelopes and prevent infection. Four VHH that recognise a conformation dependent epitope on gp41 were isolated from a llama that was immunised with recombinant gp140 derived from a subtype B’/C isolate after panning of the phage libraries on recombinant gp41. These VHH were more potent in neutralising subtype C isolates than subtype B isolates. Based on the success of an earlier study on VHH that recognise an epitope overlapping the CD4 binding site on gp120, a novel strategy was used to isolate variants of the VHH to create a family-specific VHH library. Thirty-one new VHH were characterised and grouped according to their neutralisation breadth against 3 subtype C viruses. The neutralisation breadth of the VHH correlated with its dissociation rate with gp120, and was found to be dependent on 3 amino acid residues in the third complementarity determining region of the VHH. These VHH may have further use in applications such as HIV-1 microbicides development and immunogen design through reverse immunology.
|Title:||Characterisation of subtype C HIV-I envelope glycoproteins and their recognition by llama antibody fragments|
|Open access status:||An open access version is available from UCL Discovery|
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