cells Communication Circulating Platelet-Derived Extracellular Vesicles Are a Hallmark of Sars-Cov-2 Infection Giuseppe Cappellano 1,2,† , Davide Raineri 1,2,† , Roberta Rolla 1,3 , Mara Giordano 1,3 , Chiara Puricelli 3 , Beatrice Vilardo 1,2 , Marcello Manfredi 2,4 , Vincenzo Cantaluppi 2,4,5 , Pier Paolo Sainaghi 2,4,6 , Luigi Castello 4,7 , Nello De Vita 4 , Lorenza Scotti 4 , Rosanna Vaschetto 4, * , Umberto Dianzani 1,3 and Annalisa Chiocchetti 1,2   Citation: Cappellano, G.; Raineri, D.; Rolla, R.; Giordano, M.; Puricelli, C.; Vilardo, B.; Manfredi, M.; Cantaluppi, V.; Sainaghi, P.P.; Castello,L.; et al. Circulating Platelet-Derived Extracellular Vesicles Are a Hallmark of Sars-Cov-2 Infection. Cells 2021, 10, 85. https://doi.org/10.3390/ cells10010085 Received: 30 November 2020 Accepted: 3 January 2021 Published: 7 January 2021 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional clai- ms in published maps and institutio- nal affiliations. Copyright: © 2021 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Health Sciences, Interdisciplinary Research Center of Autoimmune Diseases—IRCAD, Università del Piemonte Orientale, 28100 Novara, Italy; giuseppe.cappellano@med.uniupo.it (G.C.); davide.raineri@med.uniupo.it (D.R.); roberta.rolla@med.uniupo.it (R.R.); mara.giordano@med.uniupo.it (M.G.); beatrice.vilardo@uniupo.it (B.V.); umberto.dianzani@med.uniupo.it (U.D.); annalisa.chiocchetti@med.uniupo.it (A.C.) 2 Center for Translational Research on Autoimmune and Allergic Disease—CAAD, Università del Piemonte Orientale, 28100 Novara, Italy; marcello.manfredi@uniupo.it (M.M.); vincenzo.cantaluppi@med.uniupo.it (V.C.); pierpaolo.sainaghi@med.uniupo.it(P.P.S.) 3 Clinical Chemistry Unit, “Maggiore della Carità” University Hospital, 28100 Novara, Italy; 20032501@studenti.uniupo.it 4 Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; luigi.castello@med.uniupo.it (L.C.); nellodevita@hotmail.com (N.D.V.); lorenza.scotti@uniupo.it (L.S.) 5 Nephrology and Kidney Transplantation Unit, “Maggiore della Carità” University Hospital, 28100 Novara, Italy 6 Immunorheumatology Unit, Division of Internal Medicine, “Maggiore della Carità” Univerisity Hospital, 28100 Novara, Italy 7 Emergency Department, “Maggiore della Carità” University Hospital, 28100 Novara, Italy * Correspondence: rosanna.vaschetto@med.uniupo.it; Tel.: +39-032-1373-3406 † These authors contributed equally to this work. Abstract: Sars-Cov-2 infection causes fever and cough that may rapidly lead to acute respiratory distress syndrome (ARDS). Few biomarkers have been identified but, unfortunately, these are individually poorly specific, and novel biomarkers are needed to better predict patient outcome. The aim of this study was to evaluate the diagnostic performance of circulating platelets (PLT)-derived extracellular vesicles (EVs) as biomarkers for Sars-Cov-2 infection, by setting a rapid and reliable test on unmanipulated blood samples. PLT-EVs were quantified by flow cytometry on two independent cohorts of Sars-CoV-2+ (n = 69), Sars-Cov-2− (n = 62) hospitalized patients, and healthy controls. Diagnostic performance of PLT-EVs was evaluated by receiver operating characteristic (ROC) curve. PLT-EVs count were higher in Sars-Cov-2+ compared to Sars-Cov-2− patients or HC. ROC analysis of the combined cohorts showed an AUC = 0.79 and an optimal cut-off value of 1472 EVs/μL, with 75% sensitivity and 74% specificity. These data suggest that PLT-EVs might be an interesting biomarker deserving further investigations to test their predictive power. Keywords: circulating biomarker; extracellular vesicles; platelets; COVID-19; Sars-Cov-2 1. Introduction SARS-CoV-2 is causing COVID-19, a pandemic burden with an unprecedented impact on healthcare systems worldwide. The clinical manifestation of COVID-19 varies from asymptomatic to a severe disease affecting the respiratory tract, that may evolve to ARDS, with patients admitted to the intensive care unit needing mechanical ventilation [1]. COVID- 19 has also systemic manifestations, affecting several systems, including the cardiovascular, the gastrointestinal, the hematopoietic, the renal, and the immune one [2]. Sars-Cov-2+ patients experience several non-specific symptoms like fever, fatigue, and others. In the Cells 2021, 10, 85. https://doi.org/10.3390/cells10010085 https://www.mdpi.com/journal/cells