An ACE2-blocking antibody confers broad neutralization and protection against Omicron and other SARS-CoV-2 variants of concern

Fig. 1.. 87G7 potently neutralizes Omicron and other SARS-CoV-2 variants (A) S protein schematic with mutations indicated that are found in Alpha, Beta, Gamma, Delta and Omicron (BA.1 and BA.2) variants of concern (VOCs), and Lambda and Mu variants of interest (VOIs), relative to ancestral SARS-CoV-2. The S N-terminal domain (NTD, in blue) and receptor-binding domain (RBD, in orange), and S1/S2 junction are indicated. (B) Neutralizing activity of 87G7 against virus particles pseudotyped with ancestral SARS-CoV-2 S (Wuhan-Hu-1 strain) or S proteins of Alpha, Beta, Delta and Omicron. Error bars indicate standard deviation between at least two independent replicates. (C and D) 87G7 mediated neutralization of live SARS-CoV-2 and variants. Neutralizing potency of 87G7 and REGN10933 against the D614G SARS-CoV-2, and Alpha, Beta, Delta, Gamma and BA.1 and BA.2 Omicron VOCs (C) and against Lambda and Mu SARS-CoV-2 VOIs (D). Error bars indicate standard deviation between at least two independent replicates. (E) Inhibitory Concentrations 50% (IC50) of 87G7 against SARS-CoV-2 variants calculated from the neutralization curves displayed in panel b, c and d. NT: not tested.

Fig. 2.. Structural basis for binding and neutralization by 87G7 (A) Composite cryo-EM density map for the SARS-CoV-2 spike ectodomain in complex with the 87G7 antibody Fab fragment. The spike protomers are colored blue, gray, and pink, and the 87G7 light- and heavy-chain variable domains colored purple and yellow, respectively. (B) Surface representation of the 87G7-bound RBD overlaid with the RBD-bound ACE2 (PDB ID: 6M0J). (C) Surface representation of the RBD colored according to the Kyte-Doolittle scale, where the most hydrophobic residues are colored tan and the most hydrophilic residues are colored blue. The residues which make up the 87G7 core epitope and the ACE2 footprint are outlined. (D) Close-up view showing selected interactions formed between 87G7 and the SARS-CoV-2 RBD (E) ELISA binding of 87G7 to plate-immobilized WT, F456A, F486A and Y489A S1 domains. (F) 87G7 neutralizing activity against pseudoviruses with Wuhan-Hu-1 S and SF486A. REGN10933 and REGN10987 were taken along as a reference in panel E and F. (G) Side-by-side comparison of the SARS-CoV-2 RBD bound to 87G7, WRAIR-2125 (PDB ID: 7N4L), 58G6 (PDB ID: 7E3L), P5C3 (PDB ID: 7PHG), COV2-2196 (PDB ID: 7L7D), S2E12…

Fig. 3.. 87G7 recognizes a conserved epitope in SARS-CoV-2 RBD (A) Surface representation of the SARS-CoV-2 S RBD with mutations colored red that are found in Omicron BA.1 (left panel) and Omicron BA.2 (middle panel). The right panel displays the set of mutations surrounding the 87G7 core epitope that are present in Alpha, Beta, Gamma, Delta, Lambda or Mu (see also Fig. 1a). The 87G7 core epitope residues are colored green. (B) 87G7 neutralizing activity against pseudoviruses with S variants carrying single residue substitutions found in the SARS-CoV-2 variants of concern. The REGN10933 and REGN10987 therapeutic mAbs were used for benchmarking. Data are shown as mean (± SEM) of two independent experiments with technical triplicates, and corresponding IC50 titers are presented in the lower panel.

Fig. 4.. 87G7 protects mice from challenge with D614G SARS-CoV-2 and Alpha, Beta, Gamma or Delta variants. Prophylactic and therapeutic treatment was assessed in the K18-hACE2 SARS-CoV-2 mouse model. 87G7 or isotype control mAb was administered intraperitoneally (10 mg/kg body weight) into groups of mice (n = 5) at 24 hours before (A, B, C) or after virus challenge (D, E, F). Mice were challenged intranasally with 105 PFU of SARS-CoV-2 (D614G, Alpha, Beta, Gamma or Delta) and monitored daily for weight loss (A and D). Five days after challenge lungs were collected from all mice, and lung viral antigen levels were determined by immunohistochemistry (B and E; Table S2, Figure S6), and infectious SARS-CoV-2 loads in lung tissue were measured by plaque assay (C and F). The mean values ± SEM of all data points were shown. Dashed line indicates assay limits of detection. Mann-Whitney U test was used to evaluate the statistical difference between the 87G7 and isotype-treated groups (**p<0.01, *p<0.05, ns p>0.05).

Fig. 5.. 87G7 protects hamsters from challenge with D614G SARS-CoV-2 and Gamma, Delta and Omicron variants. 87G7 or isotype control mAb was administered intraperitoneally (10 mg/kg body weight or 20mg/kg for Omicron-challenged hamsters) into groups of Syrian hamsters (n = 5, and n = 6 for Omicron groups) at 24 hours before (A, B, C) or 12 hours after virus challenge (D, E, F). Hamsters were challenged intranasally with 104 TCID50 of D614G SARS-CoV-2, Beta, Gamma or Omicron. Four days after challenge hamsters were euthanized, and infectious SARS-CoV-2 titer in lung homogenates and nasal cavity were evaluated by TCID50 measurement (A and D). Lung and nasal cavity were examined for lesions by histopathological scoring and presence of viral antigen by immunohistochemistry (B, C and E, F; Table S3-S5, Figure S7-S10). The mean values ± SEM of all data points were shown. Mann-Whitney U test was used to evaluate the statistical difference between the 87G7 and isotype-treated groups (**p<0.01, *p<0.05, ns p>0.05).