The Anti-SARS-CoV-2 Spike Protein S1 Receptor-Binding Domain Antibody, Clone Covi-2 (Blocking/Recombinant antibody reacts with Spike Protein S1 receptor binding domain (RBD) expressed by SARS-associated coronavirus 2 (SARS-CoV-2/2019-nCoV).

The Spike (S) protein is a type I transmembrane glycoprotein present on the surface of coronaviruses (CoV). Entry of CoV into host cells is mediated by the S protein, where it interacts with the cell-surface receptor angiotensin-converting enzyme 2 (ACE2). In humans, ACE2 is expressed in several organs and tissues, including intestinal and respiratory epithelium.

The S protein has two subunits, S1 and S2, where S1 primarily consists of the 193 amino acid long RBD and the N-terminal domain (NTD). The S2 domain is responsible for membrane fusion. During CoV infection, the S protein is cleaved into the N-terminal S1 subunit and C-terminal S2 subunit by host proteases, transforming its conformation from the pre-fusion to the post-fusion state. 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. The RBD binds to ACE2, while the function of the NTD is not well understood. The Covi-2 antibody blocks the interaction of the S1 subunit with the ACE2 receptor and binds to a different epitope than the Covi-1 antibody.