Different binding signals of His-AT, His-HCII and mFc-S1 on heparin microarray. (A) Fluorescence binding signals of His-tagged AT and HCII (635 nm) and mFc-tagged SARS-CoV-2 S1 (488 nm). Binding curves of His-AT (B), His-HCII (C) and mFc-S1 (D) with serial concentrations were obtained from the fluorescence intensities of microspot images.

Anticoagulation activities of heparin, HS and bivalirudin and the inhibitory effect S protein of SARS-CoV-2. (A) Heparin inactivates thrombin and Xa activities through AT with IC₅₀ at ~0.01 μg/mL and ~0.025 μg/mL respectively. (B) S trimer inhibits the effect of AT on thrombin by competitive binding to heparin. (C) S trimer inhibits the effect of AT on Xa by binding to heparin. (D) Heparin inactivates thrombin activity through HCII with IC₅₀ at ~0.5 μg/mL. (E) S trimer inhibits the effect of HCII by binding to heparin. (F) HS inactivates thrombin activity through AT with IC₅₀ at ~7.5 μg/mL. (G) S trimer inhibits the effect of AT by binding to HS. (H) Bivalirudin inactivates thrombin activities with IC₅₀ at ~5 μg/mL. (I) S trimer cannot reverse inhibitory effect of bivalirudin on thrombin.

SARS-CoV-2 S protein causes coagulation and thrombosis in zebrafish. (A, B) The positions and the timeline of microinjection and the mechanical injury on zebrafish embryos. (C) The effect of S trimer on bleeding time in response to the mechanical injury; ****, P < 0.0001. (D, E) Imaging analysis of o-dianisidine stained embryos microinjected with PBS and S trimer. (F, G) Confocal imaging analysis of Tg(gatal:DsRed:fli1a:Egfp-CAAX) embryos microinjected with PBS and S trimer.

HS/heparin treatment can reduce the coagulation caused by S protein. (A, B) The effect of HS and heparin (Hep) co-injection with S trimer on bleeding time; ****, P < 0.0001. (C) The frequency (F) of thrombosis happened in capillaries (DLAV, ISV and CVP), large vessels including artery and vein (DA, PCV), and both capillaries and large vessels (DIC + DP).