Structure and Dynamics of HIV-1 Env Trimers on Native Virions Engaged in Living T Cells

Abstract

The HIV-1 envelope glycoprotein (Env) mediates viral entry into the host cell. Although the highly dynamic nature of Env intramolecular conformations has been shown with single molecule spectroscopy in vitro, the bona fide Env intra- and intermolecular mechanics when engaged in live T cells remains unknown. We used both, two photon fast fluorescence lifetime imaging detection of single-molecule Forster Resonance Energy Transfer and single molecule photobleaching to reveal transitions between intramolecular and intermolecular conformations that mediate Env clustering. Furthermore, we show that three broad neutralizing anti-Env antibodies directed to different epitopes destabilise Env intramolecular dynamics and their clusters when engaged to living T cells. Importantly, our results show that Env clustering is a common conformation across different HIV-1 Env strains, which depends on efficient virus maturation, and that is disrupted upon binding of Env to CD4 or to neutralizing antibodies. Thus, this study illuminates how different intramolecular conformations and clusters of Env mediate HIV-1 Env-T cell interactions in real time and therefore might control immune evasion.