Neutralizing Antibodies Induced by First-Generation gp41-Stabilized HIV-1 Envelope Trimers and Nanoparticles.

Sonu Kumar,Timothy Ngo,Andrew B Ward,Linling He,Xiaohe Lin,Jeffrey Copps,Max Crispin,Gabriel Ozorowski,Joel D Allen,Cindy Sou,Ian A Wilson,Benjamin Shapero,Jiang Zhu,Lei Zhang,Thomas E Smithgall

doi:10.1128/mbio.00429-21

Abstract

ABSTRACTThe immunogenicity of gp41-stabilized HIV-1 BG505 envelope (Env) trimers and nanoparticles (NPs) was recently assessed in mice and rabbits. Here, we combined Env-specific B-cell sorting and repertoire sequencing to identify neutralizing antibodies (NAbs) from immunized animals. A panel of mouse NAbs was isolated from mice immunized with a 60-meric I3-01 NP presenting 20 stabilized trimers. Three mouse NAbs potently neutralized BG505.T332N by recognizing a glycan epitope centered in the C3/V4 region on BG505 Env, as revealed by electron microscopy (EM), X-ray crystallography, and epitope mapping. A set of rabbit NAbs was isolated from rabbits immunized with a soluble trimer and a 24-meric ferritin NP presenting 8 trimers. Neutralization assays against BG505.T332N variants confirmed that potent rabbit NAbs targeted previously described glycan holes on BG505 Env and accounted for a significant portion of the autologous NAb response in both the trimer and ferritin NP groups. Last, we examined NAb responses that were induced by non-BG505 Env immunogens. We determined a 3.4-Å-resolution crystal structure for the clade C transmitted/founder (T/F) Du172.17 Env with a redesigned heptad repeat 1 (HR1) bend in gp41. This clade C Env, in a soluble trimer form and in a multivalent form with 8 trimers attached to ferritin NP, and the gp41-stabilized clade A Q482-d12 Env trimer elicited distinct NAb responses in rabbits, with notable differences in neutralization breadth. Although eliciting a broad NAb response remains a major challenge, our study provides valuable information on an HIV-1 vaccine design strategy that combines gp41 stabilization and NP display.

Highlights

The immunogenicity of gp41-stabilized HIV-1 BG505 envelope (Env) trimers and nanoparticles (NPs) was recently assessed in mice and rabbits
The recognition of Env by mouse neutralizing antibodies (NAbs) is much less understood relative to rabbit NAbs. The effect of both heptad repeat 1 (HR1) and gp41 stabilization, which is the core of uncleaved prefusion optimized (UFO) trimer design [19, 37], on NAb elicitation and epitope targeting in wild-type animal models has not been as well characterized as SOSIP and native flexibly linked (NFL) trimers
Our analysis revealed that M4H2K1 and VRC01 would “clash” in their Env-bound mode as indicated by slightly overlapping electron microscopy (EM) densities, suggesting that the M4H2K1 epitope is in proximity to the CD4 binding site (CD4bs) that is targeted by VRC01

Summary

Introduction

The immunogenicity of gp41-stabilized HIV-1 BG505 envelope (Env) trimers and nanoparticles (NPs) was recently assessed in mice and rabbits. Monoclonal NAbs were isolated from previously immunized mice and rabbits for structural and functional analyses, which revealed that potent mouse NAbs recognize the C3/V4 region and small NP-elicited rabbit NAbs primarily target known glycan holes on BG505 Env. This study validates the gp stabilization strategy for HIV-1 Env vaccine design and highlights the challenge in eliciting a broad NAb response. The recognition of Env by mouse (and to some extent macaque) NAbs is much less understood relative to rabbit NAbs. the effect of both HR1 and gp stabilization, which is the core of UFO trimer design [19, 37], on NAb elicitation and epitope targeting in wild-type animal models has not been as well characterized as SOSIP and NFL trimers

Methods

Results

Conclusion