ABSTRACT
SARS-CoV-2 is a newly emergent coronavirus, which has adversely impacted human health and has led to the COVID-19 pandemic. There is an unmet need to develop therapies against SARS-CoV-2 due to its severity and lack of treatment options. A promising approach to combat COVID-19 is through the neutralization of SARS-CoV-2 by therapeutic antibodies. Previously, we described a strategy to rapidly identify and generate llama nanobodies (VHH) from naïve and synthetic humanized VHH phage libraries that specifically bind the S1 SARS-CoV-2 spike protein, and block the interaction with the human ACE2 receptor. In this study we used computer-aided design to construct multi-specific VHH antibodies fused to human IgG1 Fc domains based on the epitope predictions for leading VHHs. The resulting tri-specific VHH-Fc antibodies show more potent S1 binding, S1/ACE2 blocking, and SARS-CoV-2 pseudovirus neutralization than the bi-specific VHH-Fcs or combination of individual monoclonal VHH-Fcs. Furthermore, protein stability analysis of the VHH-Fcs shows favorable developability features, which enable them to be quickly and successfully developed into therapeutics against COVID-19.
Subject(s)
Betacoronavirus/metabolism , Single-Domain Antibodies/immunology , Spike Glycoprotein, Coronavirus/immunology , Amino Acid Sequence , Angiotensin-Converting Enzyme 2 , Antigen-Antibody Reactions , Betacoronavirus/isolation & purification , Binding Sites , COVID-19 , Cell Line , Computer-Aided Design , Coronavirus Infections/pathology , Coronavirus Infections/virology , Epitopes/chemistry , Epitopes/immunology , Humans , Immunoglobulin Fc Fragments/genetics , Immunoglobulin Fc Fragments/metabolism , Molecular Docking Simulation , Mutagenesis, Site-Directed , Neutralization Tests , Pandemics , Peptide Library , Peptidyl-Dipeptidase A/chemistry , Peptidyl-Dipeptidase A/genetics , Peptidyl-Dipeptidase A/metabolism , Pneumonia, Viral/pathology , Pneumonia, Viral/virology , Protein Stability , SARS-CoV-2 , Single-Domain Antibodies/genetics , Single-Domain Antibodies/metabolism , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/metabolismABSTRACT
Coronaviruses cause severe human viral diseases including SARS, MERS and COVID-19. Most recently SARS-CoV-2 virus (causing COVID-19) has led to a pandemic with no successful therapeutics. The SARS-CoV-2 infection relies on trimeric spike (S) proteins to facilitate virus entry into host cells by binding to ACE2 receptor on host cell membranes. Therefore, blocking this interaction with antibodies are promising agents against SARS-CoV-2. Here we describe using humanized llama antibody VHHs against SARS-CoV-2 that would overcome the limitations associated with polyclonal and monoclonal combination therapies. From two llama VHH libraries, unique humanized VHHs that bind to S protein and block the S/ACE2 interaction were identified. Furthermore, pairwise combination of VHHs showed synergistic blocking. Multi-specific antibodies with enhanced affinity and avidity, and improved S/ACE2 blocking are currently being developed using an in-silico approach that also fuses VHHs to Fc domains. Importantly, our current bi-specific antibody shows potent S/ACE2 blocking (KD - 0.25 nM, IC100 â¼ 36.7 nM, IC95 â¼ 12.2 nM, IC50 â¼ 1 nM) which is significantly better than individual monoclonal VHH-Fcs. Overall, this design would equip the VHH-Fcs multiple mechanisms of actions against SARS-CoV-2. Thus, we aim to contribute to the battle against COVID-19 by developing therapeutic antibodies as well as diagnostics.