OC 57.1 - SARS-CoV-2 Spike Protein Enhanced Thrombosis is inhibited by Tipiracil in Mice

Background: COVID-19 is accompanied by excessive systemic thrombotic events, but the mechanism is unknown. All major COVID-19 vaccines were associated with thrombosis. Thymidine phosphorylase (TYMP) plays an important role in platelet activation, thrombosis, and inflammation. TYMP expression is significantly increased in COVID-19 patients.

Aims: To test the hypothesis that TYMP mediates SARS-CoV-2 spike protein (SP)-enhanced thrombosis.

Methods: Transfection of plasmid encoding SP or the receptor-binding domain (RBD) with human ACE2 was conducted in COS-7 cells. BEAS-2B cells were treated with SP or RBD containing COS-7 cell lysates, and TYMP expression and activation of NF-κB were examined. K18-hACE2 transgenic (ACE2-TG) mice were intraperitoneally treated with SP or RBD containing COS-7 cells lysates, and thrombosis was assessed three days later using the FeCl3 injury-induced carotid artery thrombosis model.

Results: SP and RBD led to ACE2 shedding, significantly increased TYMP expression, and NF-κB activation in BEAS-2B cells. In comparison to wildtype mice, ACE2-TG mice are anti-thrombotic and had significantly prolonged thrombosis time. Treating ACE2-TG mice with COS-7 cells transfected with empty plasmid did not affect the thrombosis. However, treating the ACE2-TG mice with SP- or RBD-containing COS-7 cell lysates dramatically enhanced thrombosis and significantly shortened time to occlusive thrombi formation. SP is more powerful than RBD in enhancing thrombosis. SP-enhanced thrombosis was dramatically inhibited by simultaneously feeding the mice with 1 mg/kg of tipiracil. TYMP is expressed in human type II alveolar epithelial cells and bronchial epithelium. By using the MGH Emergency Department COVID-19 Cohort with Olink Proteomics TYMP data and Receiver Operating Characteristic analysis, we found TYMP is a sensitive and specific marker in diagnosing COVID-19 (AUC 0.8721, p < 0.0001).

Conclusion(s): SARS-CoV-2 SP and RBD are pro-inflammatory and pro-thrombotic. SP/RBD-induced thrombosis is inhibited by tipiracil, a TYMP inhibitor. TYMP is a sensitive marker for COVID-19 diagnosis. Targeting TYMP could be a novel effective treatment for COVID-19.