For detection and measurement of compounds that inhibit binding of viral SARS-CoV-2 Spike protein to human ACE2 receptor.

The Human SARS-CoV-2 Spike Protein Inhibitor Screening Kit is designed for the identification and characterization of inhibitor molecules, including antibodies or chemicals, that prevent the binding of SARS-CoV-2 virus to the host angiotensin-converting enzyme 2 (ACE-2)-expressing cells. The Spike (S) protein is a type I transmembrane glycoprotein present on the surface of coronaviruses (CoV). Entry of CoV, including SARS-CoV-2, into host cells is mediated by the S protein, where it interacts with the cell-surface receptor ACE2. In humans, ACE2 is expressed in several organs and tissues, including the intestinal and respiratory epithelia.

The S protein has been shown to play a key role in the induction of neutralizing antibody and T cell responses, which may lead to protective immunity. This inhibitor screening assay is based on a competitive ELISA method, in which inhibitors to be tested are mixed with biotinylated recombinant human ACE2 and are added to ELISA strip plates coated with recombinant SARS-CoV-2 S protein.. The captured biotinylated ACE2 is detected by streptavidin-horseradish peroxidase (HRP), which binds the biotinylated ACE2.

Addition of the chromogenic enzyme substrate 3,3’,5,5’ tetramethylbenzidine (TMB) results in a coloured product with an intensity directly proportional to the binding activity of ACE2 to the S protein. Inhibitors will compete with the biotinylated ACE2 for binding to the SARS-CoV-2 S protein, resulting in reduced signal for more effective inhibitors. This inhibitor screening assay can be performed in the reverse configuration, in which the plate is coated with biotinylated recombinant ACE2, recombinant S Protein is mixed with the inhibitor to be tested, and S protein binding is detected using anti-human IgG-HRP.