A thesis submitted to the School of Pathology, Faculty of Health Sciences, University of the
Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of
Philosophy.
Johannesburg, 2016 / Human Immunodeficiency Virus Type 1 (HIV-1) infects approximately two million people
annually, highlighting the need for a preventative vaccine. An effective HIV-1 vaccine will
likely need to elicit broadly neutralizing antibodies (bNAbs), which arise naturally in some
infected individuals and recognize the envelopes (Env) of multiple HIV-1 strains.
Understanding the molecular events that contribute to bNAb development during infection
may provide a blueprint for vaccine strategies. Here we investigated the development of a
V1V2-directed bNAb lineage in the context of viral co-evolution in an HIV-1 superinfected
participant (CAP256). For this, clonally-related monoclonal antibodies (mAbs), with a range
of neutralization breadth, were isolated. We determined their developmental pathway from
strain-specificity towards neutralization breadth and identified viral variants responsible for
initiating and maturing this bNAb lineage.
MAbs were isolated by memory B cell culture or trimer-specific single B cell sorting and
extensively characterized by Env-pseudotyped neutralization, cell surface-expressed Env
binding, electron microscopy and epitope-predictive algorithms. Antibody next-generation
sequencing (NGS) at multiple time-points enabled the inference of the unmutated common
ancestor (UCA) of this lineage. Viral co-evolution was investigated using Env single genome
amplification and V1V2 NGS.
A family of 33 clonally-related mAbs, CAP256-VRC26.01-33, was isolated from samples
spanning four years of infection. The UCA of this lineage possessed an unusually long heavy
chain complementarity determining region 3 (CDRH3), which resulted from a unique
recombination event. Surprisingly, this UCA potently neutralized later viral variants that had
evolved from the superinfecting virus, which we termed bNAb-initiating Envs. Viral
diversification, which peaked prior to the development of neutralization breadth, created
multiple immunotypes at key residues in the V1V2 epitope. Exposure to these immunotypes
allowed adaptation of some mAbs to tolerate this variation and thus mature towards
neutralization breadth.
Based on these data, we proposed a four-step immunization strategy which includes
priming with bNAb-initiating Envs to engage rare B cells with a long CDRH3; followed by
three sequential boosts (including select V1V2 immunotypes) to drive antibody maturation.
In conclusion, this study has generated a testable HIV-1 vaccine immunization strategy
through the delineation of mAb-virus co-evolution during the development of neutralization
breadth. / MT2017
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/22283 |
| Date | January 2016 |
| Creators | Bhiman, Jinal Nomathemba |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (xvii, 162 leaves), application/pdf |
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