Chimeric ACE2 peptide ligand for diagnostic assays of SARS-CoV-2

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Recently, angiotensin-converting enzyme 2 (ACE2) was shown to be a functional receptor for SARS-CoV-2, enabling the virus to enter host target cells. Using structure-based rational design, a chimeric ACE2 peptide was designed by us for use as a ligand for analytical quantitation of SARS-CoV-2. We aim to improve the initial design and examine the potential uses of a chimeric peptide displaying a 3-D discontinuous epitope representative of the binding surface of ACE2 recognized by the RBD of the corona virus spike protein, S1. This chimera was initially designed based on multiple structures of the S1 RBD and ACE2 complexes (PDB codes 6LZG, 6VSB, 6VXX, 6VYB, and 6LXT).The chimera was meant to be a physiologically relevant, high affinity probe specific for the epitope that is critically important for the virus binding to the target cell surface receptor. Functionality of the chimera in that respect can be easily proven by in vitro competition assays using recombinant S1 protein fragments (S1 ectodomain and S1 RBD) and recombinant ectodomain of the ACE2 protein. We will use tagged proteins that can be immobilized to use BLI for characterization of binding. The aim of this work is to adapt the chimeric ACE2 peptide for two diagnostic applications: 1) to develop and characterize an imuno-qPCR assay for the detection of SARS-CoV-2 in saliva and mucosal samples 2) to perform in vivo bioimaging, biodistribution, clearance and toxicity studies. The novel applications represent promising tools to advance coronavirus epidemiology, pathogenicity, and receptors related knowledge.