Persistent hypofibrinolysis in severe COVID-19 associated with elevated fibrinolysis inhibitors activity.

Hypercoagulability and reduced fibrinolysis are well-established complications associated with COVID-19. However, the timelines for the onset and resolution of these complications remain unclear. The aim of this study was to evaluate, in a cohort of COVID-19 patients, changes in coagulation and fibrinolytic activity through ROTEM assay at different time points during the initial 30 days following the onset of symptoms in both mild and severe cases. Blood samples were collected at five intervals after symptoms onset: 6-10 days, 11-15 days, 16-20 days, 21-25 days, and 26-30 days. In addition, fibrinogen, plasminogen, PAI-1, and alpha 2-antiplasmin activities were determined. Out of 85 participants, 71% had mild COVID-19. Twenty uninfected individuals were evaluated as controls. ROTEM parameters showed a hypercoagulable state among mild COVID-19 patients beginning in the second week of symptoms onset, with a trend towards reversal after the third week of symptoms. In severe COVID-19 cases, hypercoagulability was observed since the first few days of symptoms, with a tendency towards reversal after the fourth week of symptoms onset. A hypofibrinolytic state was identified in severe COVID-19 patients from early stages and persisted even after 30 days of symptoms. Elevated activity of PAI-1 and alpha 2-antiplasmin was also detected in severe COVID-19 patients. In conclusion, both mild and severe cases of COVID-19 exhibited transient hypercoagulability, reverted by the end of the first month. However, severe COVID-19 cases sustain hypofibrinolysis throughout the course of the disease, which is associated with elevated activity of fibrinolysis inhibitors. Persistent hypofibrinolysis could contribute to long COVID-19 manifestations.

Extracellular vesicles are a late marker of inflammation, hypercoagulability and COVID-19 severity.

Exacerbated inflammation and coagulation are a hallmark of COVID-19 severity. Extracellular vesicles (EVs) are intercellular transmitters involved in inflammatory conditions, which are capable of triggering prothrombotic mechanisms. Since the release of EVs is potentially associated with COVID-19-induced coagulopathy, the aim of this study was to evaluate changes in inflammation- and hypercoagulability-related EVs during the first month after symptom onset and to determine whether they are associated with disease severity. Blood samples of patients with mild or severe forms of the disease were collected on three occasions: in the second, third and fourth weeks after symptom onset for the quantification by flow cytometry of CD41A (platelet glycoprotein IIb/IIIa), CD162 (PSGL-1), CD31 (PECAM-1) and CD142 cells (tissue factor). Analysis of variance (ANOVA) with repeated measures, Kruskal-Wallis and correlation tests were used. Eighty-five patients were enrolled, 71% of whom had mild disease. Seventeen uninfected individuals served as controls. Compared to controls, both mild and severe COVID-19 were associated with higher EV-CD31+, EV-CD41+ and EV-CD142+ levels. All EV levels were higher in severe than in mild COVID-19 only after the third week from symptom onset, as opposed to C-reactive protein and D-dimer levels, which were higher in severe than in mild COVID-19 earlier during disease progression. EV levels were also associated with C-reactive protein and D-dimer levels only after the third week of symptoms. In conclusion, EVs expressing CD41A, CD31, TF, and CD162 appear as late markers of COVID-19 severity. This finding may contribute to the understanding of the pathogenesis of acute and possibly long COVID-19.

Anticoagulant Activity of Nucleic Acid Nanoparticles (NANPs) Assessed by Thrombin Generation Dynamics on a Fully Automated System.

Rapidly reversible anticoagulant agents have great clinical potential. Oligonucleotide-based anticoagulant agents are uniquely positioned to fill this clinical niche, as they are able to be deactivated through the introduction of the reverse complement oligo. Once the therapeutic and the antidote oligos meet in solution, they are able to undergo isothermal reassociation to form short, inactive, duplexes that are rapidly secreted via filtration by the kidneys. The formation of the duplexes interrupts the structure of the anticoagulant oligo, allowing normal coagulation to be restored. To effectively assess these new anticoagulants, a variety of methods may be employed. The measurement of thrombin generation (TG) reflects the overall capacity of plasma to produce active thrombin and provides a strong contribution to identifying new anticoagulant drugs, including DNA/RNA thrombin binding aptamer carrying fibers which are used through this chapter as an example. Here we describe the TG assessed by Calibrated Automated Thrombogram (CAT) assay in a fully automated system. This method is based on the detection of TG in plasma samples by measuring fluorescent signals released from a quenched fluorogenic thrombin substrate and the subsequent conversion of these signals in TG curves.