Anti-RBD-6 antibody (VHH-72)

General information on Anti-RBD-6 antibody

Antibody anti-RBD-6 is a single-domain camelid heavy chain immunoglobulin (VHH, nanobody). It was developed by immunizing a llama with stabilized spike proteins from coronaviruses MERS-CoV and SARS-CoV-1. After immunization and development of a measurable immune response, the RNA was isolated from the peripheral blood mononuclear cells (PBMCs) and used as a template for cDNA synthesis and amplification of the antibody genes.
The resulting library of antibodies was screened by phage display with Escherichia coli and M13 helper phages against the spike protein of SARS-CoV-1. Binders with the highest affinity were screened for cross-reactivity with the spike protein of the new coronavirus and selected for further studies. The anti-RBD-6 antibody displayed a high affinity towards the spike proteins of SARS-CoV-1 and SARS-CoV-2. Crystallization studies further revealed this antibody binds a conserved region of the receptor-binding domain (RBD) shared between the two SARS strains. Additional studies with pseudotyped viral particles showed that the anti-RBD-6 antibody in a monovalent format (VHH) displayed only a mild neutralizing activity against these viruses.
Due to its initially feeble activity, the monovalent VHH was further engineered into a bivalent conformation (VHH-VHH). This format succeeded in enhancing this molecule’s neutralizing activity.
VHH antibodies are valuable reagents due to their enhanced chemo and thermostability in comparison to conventional antibodies. They are also easier to produce in vitro due to the absence of glycans on their surface. Moreover, they display higher diffusion rates making their ideal reagents for diagnostics and therapeutic applications. In this context, this bivalent VHH molecule can serve to investigate SARS-CoV-2 mechanisms of infection, develop robust in vitro diagnostic tools, and used for medical imaging when conjugated with the adequate molecular markers.