cAMP prevents antibody-mediated thrombus formation in COVID-19

Background: COVID-19 antibody (Ab) induced procoagulant platelets (PLTs) were recently identified and associated with a higher risk of thromboembolic events in patients infected with SARS-CoV-2. However, the underlying mechanisms leading to procoagulant PLTs in COVID-19 remain elusive. Aims: In this study the mechanisms of COVID-19 Ab induced procoagulant PLT formation as well as the contribution of this PLT subpopulation in thrombus formation were investigated. Methods: Washed PLTs were incubated with IgG fractions from severe COVID-19 ICU or non-COVID-19 ICU patients and analyzed for changes in the expression of caspase 3 using immunoblot as well as CD62P (P-selectin) and phosphatidylserine (PS) via double staining in flow cytometry. To investigate the impact of procoagulant PLTs on thrombus formation, collagen coated microfluidic channels were perfused with whole blood after incubation with IgG antibodies from COVID-19 or control patients. Results: ICU COVID-19 IgG induced a significant increase in caspase 3 cleavage and formation of CD62P/PS positive procoagulant PLTs compared to the ICU control group (31.63%±3.86 vs. 4.04%±1.16, P = 0.0007). Remarkably, incubation of PLTs with ICU COVID-19 IgG resulted in increased thrombus formation (mean % surface area covered [SAC]±SEM: 13.95±1.55 vs. 2.86±1.10, P = 0.0070) and was significantly inhibited by PLT FcγRIIA blockade (16.49±1.02 vs. 5.84±1.93, P = 0.0090). Most importantly and of potential therapeutic relevance, Ab induced procoagulant PLTs and increased thrombus formation were markedly reduced in the presence of Iloprost, a prostacyclin analogue and elevator of intracellular cAMP (41.36%±3.60 vs. 22.22%±3.92, P = 0.0156 and 14.63±2.31 vs. 3.85±0.95, P = 0.0079, respectively). Conclusions: Our findings indicate that COVID-19 Abs induce procoagulant PLTs and increased thrombus formation in a FcγRIIA dependent pathway. As these changes were inhibited via Iloprost, upregulation of cAMP in PLTs might be a promising future therapeutic approach for the complex coagulopathy observed in critical ill COVID-19 patients. (Figure Presented) .