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Quantum Dot-Conjugated SARS-CoV‑2 Spike Pseudo-Virions Enable Tracking of Angiotensin Converting Enzyme 2 Binding and Endocytosis

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posted on 08.09.2020, 20:30 by Kirill Gorshkov, Kimihiro Susumu, Jiji Chen, Miao Xu, Manisha Pradhan, Wei Zhu, Xin Hu, Joyce C. Breger, Mason Wolak, Eunkeu Oh
The first step of SARS-CoV-2 infection is binding of the spike protein’s receptor binding domain to the host cell’s ACE2 receptor on the plasma membrane. Here, we have generated a versatile imaging probe using recombinant Spike receptor binding domain conjugated to fluorescent quantum dots (QDs). This probe is capable of engaging in energy transfer quenching with ACE2-conjugated gold nanoparticles to enable monitoring of the binding event in solution. Neutralizing antibodies and recombinant human ACE2 blocked quenching, demonstrating a specific binding interaction. In cells transfected with ACE2-GFP, we observed immediate binding of the probe on the cell surface followed by endocytosis. Neutralizing antibodies and ACE2-Fc fully prevented binding and endocytosis with low nanomolar potency. Importantly, we will be able to use this QD nanoparticle probe to identify and validate inhibitors of the SARS-CoV-2 Spike and ACE2 receptor binding in human cells. This work enables facile, rapid, and high-throughput cell-based screening of inhibitors for coronavirus Spike-mediated cell recognition and entry.