Defining virus-antibody interplay during the development of HIV-1 neutralization breadth to inform vaccine design
Bhiman, Jinal Nomathemba
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.
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
Bhiman, Jinal Nomathemba (2016) Defining virus-antibody interplay during the development of HIV-1 neutralization breadth to inform vaccine design, University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/22283>