Fig. 7

Recombinant human ACE2 protein and anti-Spike monoclonal antibody suppress SARS-CoV-2-induced platelet activation. A, Enhanced platelet aggregation by SARS-CoV-2 is abolished by recombinant human ACE2 protein and anti-Spike monoclonal antibody (targeting the receptor-binding domain [RBD] of SARS-CoV-2). Representative results are presented from 3 experiments using platelets from different donors. B, Enhanced platelet aggregation by Spike protein is suppressed by ACE2 protein and anti-Spike antibody. Representative results are presented from 3 experiments using platelets from different healthy donors. For A and B, the healthy human platelets were pretreated with ACE2 protein (10 μg/mL) or anti-Spike antibody (4 μg/mL) for 10 min, then treated with SARS-CoV-2 (1 × 10⁵ PFU, 30 min) or Spike protein (2 μg/mL, 5 min) before stimulation by 0.025 U/mL thrombin or 0.6 μg/mL collagen. C and D, The ACE2 protein and anti-Spike antibody reversed PAC-1 binding and CD62P expression induced by SARS-CoV-2 (C) or Spike protein (D). Representative images and summary data are presented from 4 experiments using platelets from different healthy donors. E, Enhanced platelet spreading induced by SARS-CoV-2 (E1) or its Spike protein (E2) are abolished by ACE2 protein and anti-Spike monoclonal antibody. Representative images and summary data of 4 experiments are presented using platelets from different healthy donors. F, Accelerated clot retraction induced by SARS-CoV-2 (F1) or its Spike protein (F2) are abolished by ACE2 protein and anti-Spike monoclonal antibody. Representative images and summary data of 4 experiments are presented using platelets from different healthy donors. For C, D, E and F, platelets were pretreated with ACE2 protein (10 μg/mL) or anti-Spike antibody (4 μg/mL) for 10 min, and incubated with SARS-CoV-2 (1 × 10⁵ PFU, 30 min) or Spike protein (2 μg/mL, 5 min), and then subjected to flow cytometry of thrombin-activated platelets, platelet spreading assay, and clot retraction assay. G, Increased thrombus area induced by Spike protein in wild-type mice transfused with platelets from hACE2 transgenic mice is suppressed by ACE2 protein and anti-Spike antibody. Representative photographs of FeCl3-induced thrombus formation at the indicated time points within 30 min after intravenous administration of Spike protein (200 μg/kg) with ACE2 protein (1 mg/kg) or anti-Spike monoclonal antibody (400 μg/kg). Dot plot showing thrombus area for control or Spike protein treated mice (n = 10). Statistical analyses were performed using one-way ANOVA, followed by Tukey’s post hoc analysis in (C), (D), (E), (F), and (G). *P < 0.05; **P < 0.01. RhACE2 indicates recombinant human ACE2 protein; anti-S Ab, anti-Spike antibody