Potent broadly neutralizing antibody development against the HIV-1 fusion peptide epitope

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Project Summary/Abstract Vaccines and antibody interventions against human immunodeficiency virus-1 (HIV-1) have made tremendous progress, but are not yet ready for broad clinical use. A vaccine that prevents new infections could provide a major boost to ending the HIV-1 pandemic by blocking transmissions. The HIV-1 fusion peptide (FP) has shown promise as a broadly neutralizing antibody (bNAb)-directed vaccine target site because vaccine antigens can effectively prime and expand B cell responses targeting FP. However, HIV-1 genetic diversity at FP and the limited potency & neutralization breadth of known antibodies at the FP site has slowed progress for FP-directed interventions. A better understanding of how anti-FP antibodies can attain exquisite neutralization potency and breadth against HIV-1 will enable improved vaccines and therapeutic development. This project will explore critical mutational pathways for anti-FP antibodies, providing new molecular and functional insights for better antibody & vaccine solutions against HIV-1 FP. Aim 1 of the project will apply precision mutational scanning and directed evolution to engineer exquisite neutralization potency for antibodies targeting HIV-1 FP. We will implement a new single-cell droplet-based screening platform established by our laboratory to directly identify antibody variants based on neutralization function. Aim 1 will enhance anti-FP antibody breadth & potency beyond current best-in-class examples, and by studying these antibodies we will learn more about the structural & molecular requirements for potent protection at FP. For Aim 2, we will explore the affinity mutational landscapes that can increase cross-reactivity and breadth against FP, and compare those data with neutralization profiles in Aim 1 to understand the connections between affinity-enhancing and neutralization-enhancing mutations. Finally, in Aim 3 we will explore how antibody variable region mutations can also influence Fc-effector function, and how HIV-1 Fc effector protein engagement co- correlates with affinity and neutralization of a given mutation against diverse HIV-1 viral isolates. Data from Aim 3 will accelerate our understanding of bNAb Fc effector recruitment mechanisms, and synergize with parallel improvements in Fab-mediated neutralization potency. This project elucidates the critical relationships between neutralization potency, antigen affinity, and effector function in antibodies targeting the FP site. Our multi-platform approach enables the most comprehensive functional study of anti-FP antibodies to date, with layered characterization of the genetic, biophysical, and functional features that lead to exquisite anti-HIV-1 activity. The new bNAbs generated and knowledge gained by this project will provide critical information and resources to develop globally relevant vaccines and therapeutics against HIV-1 FP.