Patients with Coronavirus-associated disease 2019 (COVID-19) display alterations of the hemostatic system and the presence of a prothrombotic status frequently leading to vascular complications. However, the impact of COVID-19 on platelet activity, aggregation and agglutination remains to be clarified. It is also not known how microRNAs influence platelet functions in these patients. In the present proposal, we will measure total levels of von Willebrand factor (vWF) and vWF binding to the platelet glycoprotein (Gp) complex (GPIb-IX-V), in a cohort of COVID-19 patients admitted to the intensive care unit of Policlinico Umberto I university hospital. Moreover, we will evaluate platelet aggregation in response to agonists, (ADP, collagen, arachidonic acid) and platelet agglutination in response to ristocetin (RCo). We will investigate whether the levels of vWF antigen and the active form of vWF binding to platelets (vWF:RCo), are altered in these patients. We will analyze if this is associated with higher agglutination rates induced by RCo, thereby indicating an increased capability of vWF to bound to platelets. Conversely, we will investigate if platelet aggregation in response to both ADP and collagen is different in COVID-19 patients.
This study will help in understanding if COVID-19 is associated with increased vWF-induced platelet agglutination and reduced platelet responsiveness to aggregation stimuli. Furthermore, we will establish complete miRNome profile and identify platelet miRNAs correlated with activation and aggregation functions from plasma of Covid-19 patients. Further, we will analyze platelets from Covid-19 patients for their miRNA content to identify if disease causing miRNAs use platelets as vehicles. The results obtained from this proposal will have translational relevance since platelet adhesion to vWF may represent a marker to predict possible complications and better delineate therapeutic strategies in COVID-19 patients.
The pandemic caused by SARS-CoV-2 has caused unprecedented number of patients with acute respiratory distress syndrome with consequent aortic and venous thrombotic complications due to excessive inflammation, platelet activation, endothelial dysfunction and stasis.
As the vaccine drive proceeds with varying degree of efficiency across the globe, we must take into consideration the novel virus variants with more infectious power and transmission being generated as Sars-Cov-2 comes coming under selective pressure. Indeed, the latest delta variant with high infectivity is a case in point. Since, the risk of a third wave of Covid-19 cannot be excluded globally due to such new viral variants, it becomes important to identify laboratory parameters which help to identify those patients with a particularly high risk of thrombotic complications.
We have preliminarily identified marked increase in plasma levels of von Willebrand Factor Antigen, VWF ristocetin cofactor (vWF:RCo) expression of activated VWF, e rates of platelet agglutination induced by ristocetin in Covid-19 patients who were critically ill in the first phase of the pandemic. In this proposal, we will investigate how those patients who got cured are now with regards to the platelet activation and aggregation functions. Furthermore, we propose to carry out a complete miRNome profile of platelet derived miRNAs in patients with varying Covid-19 illness, identify and correlate platelet miRNA expression with platelet activation and aggregation parameters. We also propose to correlate the platelet miRNA expression in Covid-19 plasma with SARS-CoV-2 viral load.
Overall, our proposal aims to identify alteration in platelet functional parameters of Covid-19 patients and microRNA related molecular mechanisms of activation and aggregation of platelets. This will lead to identification of novel biomarkers to stratify patients which are at higher risk of thrombotic events correlated with SARS-CoV-2 infection and mitigate events of such risks with adequate therapeutic interventions.