Hemostatic profile of COVID-19 convalescent plasma (CCP) donors from Bergamo Area

Background: Hypercoagulability, complement activation and endothelial perturbation characterize sever COVID-19. After disease remission, a proportion of convalescent subjects still experience post-COVID-19 symptoms. No information is available on persistence of hemostatic alterations in this setting. Bergamo city, represents one of the first and most affected area by SARS-CoV-2 infection in the world. For this reason, since the beginning we were actively involved in recruiting CCP donors. Aims: In a large cohort of CCP donors, we aimed to characterize biomarkers of hypercoagulability and of endothelial perturbation in order to find associations with disease severity, demographic characteristics, and anti-SARS-CoV-2 antibody levels. Methods : Candidate CCP donors were tested for the anti-SARSCoV-2 antibodies, including anti-S IgG antibodies (Anti-S Ab) and anti-N IgG antibodies (Anti-N Ab). In addition, the following plasma biomarkers were assessed: fibrinogen, protein C, protein S, factor V, factor VIII, factor XIII, D-dimer, and von Willebrand factor (vWF). Results: 425 CCP candidates (275M/150F, age range 19-67 years) were admitted to donation. Male gender, age > 40 years, and severe form of COVID-19 were identified as independent predictors of high levels of both anti-S and anti-N Ab ( p <0.001). Among hemostatic parameters, levels of vWF antigen, vWF activity and protein C were significantly higher in CCP donors who had severe COVID-19 compared to donors who had non-severe COVID-19 ( p <0.001). Furthermore, vWF levels positively correlated with anti-S Ab levels (vWF-antigen r=0.216 vWF-activity r=0.257 and vWFRiCof r=0.226, p <0.01). Conclusions: Our data show that gender, age and severe disease can be predictors of an increased immunological response. Furthermore, convalescent subjects show a persistently high vWF levels, suggesting a persistence of the endothelial activation, despite of clinical disease remission.