Platelet αIIbβ3 integrin binds to SARS-CoV-2 spike protein of alpha strain but not wild type and omicron strains

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 causes a pandemic infectious disease, Coronavirus disease 2019 (COVID-19). It causes respiratory infection. Then, it progresses into a systemic infection by involving other organs. This progression mechanism remains to be elucidated, although thrombus formation plays an important role in its progression. Platelets is involved in the thrombus formation by aggregating each other through association of activated αIIbβ3 integrin with the Arg-Gly-Asp (RGD) motif-containing its ligands such as fibrinogen and von Willebrand factor. SARS-CoV-2 enters host cells through association of the spike protein (S-protein) with its receptor, angiotensin-converting enzyme 2 (ACE-2), on the host cells. While presence of ACE2 in platelets is suspicious, S-protein harbors the RGD sequences within its receptor binding domain. Therefore, it could be possible SARS-CoV-2 enter platelets through association of S-protein with αIIbβ3. In this study, we found that receptor binding domain of S-protein of WT SARS-CoV-2 strain barely bound to isolated healthy human platelets. In contrast, highly toxic alpha-strain-based N501Y substitution strongly bound to platelets in a RGD dependent manner, although binding of S protein did not induce platelet aggregation or activation. This binding may serve for transferring the infection to systemic organs.