Cellular Effects of SARS-CoV-2 in Mediating Thrombotic Susceptibility

1. Background and scientific rationale Infection with the novel coronavirus SARS-CoV-2, first identified in Wuhan, China in late 2019, has become a global pandemic affecting over 209 countries and territories. The illness caused by SARS-CoV-2 is classified as COVID-19. As of August 23rd, 2021, more than 212 million cases of COVID-19 had been reported in more than 220 countries, resulting in more than 4.4 million deaths. The U.S. has by far the largest number of total cases (>38 million) with a mortality rate of 1.67%. Although many patients may have only mild upper respiratory symptoms, some COVID-19 patients become severely ill with respiratory failure with risk of progression to multiple organ failure and development of systemic coagulopathy with features similar to disseminated intravascular coagulation (DIC).1 The pathophysiology of COVID-19-associated coagulopathy appears to be complex and multifactorial, involving both cellular and plasmatic elements of the hemostatic system. Development of coagulopathy is a predictor of mortality in patients with COVID-19.2 Still, there are no direct mechanistic links established between SARS-CoV-2 infection and coagulopathy or thrombosis.

At the University of Iowa, we led a multicenter randomized clinical trial comparing standard prophylactic dose to intermediate dose enoxaparin in hospitalized patients with COVID-19 (NCT04360824).3 As part of an exploratory biomarker component of this trial, we collected blood samples from hospitalized COVID-19 patients at enrollment and weekly for up to 30 days of hospitalization. Our pilot results, as well as reports from other groups, demonstrate increased potential for thrombin generation in the plasma of COVID-19 patients. In particular, in our COVID-19 patient cohort we observed that enhanced thrombin generation potential persisted for at least 30 days of hospitalization. We now propose to explore the mechanistic roles of activation of blood cells (such as platelets and neutrophils), microparticles, extracellular histones, interleukin-6 (IL6), and galectin-3 (Gal-3) as mediators of enhanced thrombin generation in patients with COVID-19. The study design will be a longitudinal cohort study, which will allow us to determine the time course of enhanced thrombin generation potential in relation to clinical outcomes and changes in markers of cellular activation in serial samples obtained from COVID-19 patients for up to 3 years after infection with SARS-CoV-2. This study may provide clues to why a subset of COVID-19 patients present with late thrombotic complications even after apparent recovery from SARS-CoV-2 infection.4 Thus, this project has a strong scientific rationale with direct clinical implications, especially given the emergence of SARS-CoV-2 variants such as delta and omicron that may prolong the pandemic and/or cause surges of COVID-19 in the coming months.

An ongoing question in the field relates to the comparative prothrombotic effects of acute COVID-19 versus incidental SARS-CoV-2 infection versus acute infection with influenza viruses. Therefore, we will include three categories of hospitalized patients in this study: (1) acute COVID-19, (2) incidental COVID-19, and (3) acute influenza A or B.

It is now recognized that SARS-CoV-2 infection can be associated with persistent, relapsing, or new symptoms or other health effects occurring after acute infection, termed "postacute sequelae of SARS-CoV-2 infection" (PASC), also known as "long COVID" or "post-COVID condition" (PCC) or "postinfective fatigue syndrome" (PIFS).5 It is not known whether or not persistent coagulopathy is a feature of PASC. Therefore, we will include assessment of post-COVID symptoms in our longitudinal cohort study design, which will allow us to assess for PASC as defined by Thaweethai et al.,2023.5 2. Objectives 2.1 Primary objectives 2.1.1 Determine the time course of enhanced thrombin generation potential in patients with COVID-19 or influenza.

2.1.2 Test the hypothesis that activation of platelets, neutrophils, and endothelial cells by plasma from COVID-19 patients is mediated by Gal-3, IL6, and/or histones.