Primates, Probes, and Protection: Preclinical Evaluation of Antibodies to HIV-1 and SARS-CoV-2 in Rhesus Macaques Open Access
Edwards, Christopher (Summer 2025)
Abstract
Broadly neutralizing antibodies (bNAbs) exhibit protective efficacy against HIV-1 infection making them an ideal archetype for HIV-1 vaccine design. Presently, no vaccine candidate has induced bNAbs against neutralization-resistant tier 2 viruses. However, the development of stabilized, native-like envelope (Env) trimers such as BG505.SOSIP.664 has marked a significant advancement in vaccine design, due to their ability to elicit tier 2 neutralizing antibodies (NAbs) in rhesus macaques (RM). NAb development against tier 2 immunogens in RM remains poorly understood, with hypothesized contributions from genetic variation at the IG loci, naive B cell repertoire, and differential gene expression in B cell lineages. To address these knowledge gaps, we have developed a set of BG505.SOSIP.644 probes capable of recovering paired clonotype identity, antigen specificity, and gene expression of B cells in a high throughput fashion. These probes were constructed by conjugating biotinylated BG505.SOSIP.644 to streptavidin covalently linked to both sc-RNA-Seq compatible DNA oligonucleotides and flow cytometry compatible fluorophores. Using these reagents, we isolated and sequenced BG505.SOSIP.644 specific memory B cells from an RM developing high titers of neutralizing antibodies. To benchmark the accuracy of our technology, we compared our recovered heavy and light chain sequences to those identified from the same animal using conventional methodology and successfully recovered 100% of previously identified NAbs. We then applied this technology to recover BG505.SOSIP.644 specific memory B cells from 5 additional vaccinated RMs, and cloned 34 antibodies for functional characterization. Our approach will allow for high-throughput analysis of the evolution of Env specific lineages in both RM and humans in response vaccination with HIV-1 Env immunogens, including BG505.SOSIP.644.
The continued evolution of SARS-CoV-2 variants capable of subverting vaccine and infection-induced immunity suggests the advantage of a broadly protective vaccine against betacoronaviruses (β-CoVs). Recent studies have isolated monoclonal antibodies (mAbs) from SARS-CoV-2 recovered-vaccinated donors capable of neutralizing many variants of SARS-CoV-2 as well as other β-CoVs. Many of these mAbs target the conserved S2 stem region of the SARS-CoV-2 spike protein, rather than the receptor binding domain contained within S1 primarily targeted by current SARS-CoV-2 vaccines. One of these S2-directed mAbs, CC40.8, has demonstrated protective efficacy in small animal models against SARS-CoV-2 challenge. As the next step in the pre-clinical testing of S2-directed antibodies as a strategy to protect from SARS-CoV-2 infection, we evaluated the in vivo efficacy of CC40.8 in a clinically relevant non-human primate model by conducting passive antibody transfer to RM followed by SARS-CoV-2 challenge. CC40.8 mAb was intravenously infused at 10mg/kg, 1mg/kg, or 0.1mg/kg into groups (n = 6) of RM, alongside one group that received a control antibody (PGT121 10mg/kg). We observed a significant reduction in viral loads, inflammatory cytokines, and inflammatory macrophages within the lower airway of animals infused with 10mg/kg and 1mg/kg doses of CC40.8, and viral genome sequencing revealed a lack of escape mutations in the CC40.8 epitope. These data demonstrate the protective efficiency of broadly neutralizing S2-targeting antibodies against SARS-CoV-2 infection within the lower airway while providing critical preclinical work necessary for the development of pan–β-CoV vaccines.
Collectively, the results of these studies highlight the power of high-resolution immunoprofiling tools and non-human primate models to advance rational vaccine for two major global pathogens, HIV-1 and SARS-CoV-2, and underscore the potential of broadly neutralizing antibodies to inform next-generation strategies for preventing infection by highly variable viruses.
Table of Contents
Chapter One: Introduction – SARS-CoV2 | HIV - 1
Chapter Two: Passive infusion of an S2-Stem broadly neutralizing antibody protects against SARS-CoV-2 infection and lower airway inflammation in rhesus macaques - 46
Chapter Three: Non-human primate LIBRA-Seq accelerates neutralizing antibody discovery in RM vaccinated against HIV-1 - 129
Chapter Four: Discussion - 181
References: - 190
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Primates, Probes, and Protection: Preclinical Evaluation of Antibodies to HIV-1 and SARS-CoV-2 in Rhesus Macaques () | 2025-07-16 14:01:35 -0400 |
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