Platelet activation and partial desensitization are associated with viral xenophagy in patients with severe COVID-19

Abstract

Mild thrombocytopenia, changes in platelet gene expression, enhanced platelet functionality, and presence of platelet-rich thrombi in the lung have been associated with thromboinflammatory complications of patients with COVID-19. However, whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) gets internalized by platelets and directly alters their behavior and function in infected patients remains elusive. Here, we investigated platelet parameters and the presence of viral material in platelets from a prospective cohort of 29 patients with severe COVID-19 admitted to an intensive care unit. A combination of specific assays, tandem mass spectrometry, and flow cytometry indicated high levels of protein and lipid platelet activation markers in the plasma from patients with severe COVID-19 associated with an increase of proinflammatory cytokines and leukocyte-platelets interactions. Platelets were partly desensitized, as shown by a significant reduction of αIIbβ3 activation and granule secretion in response to stimulation and a decrease of surface GPVI, whereas plasma from patients with severe COVID-19 potentiated washed healthy platelet aggregation response. Transmission electron microscopy indicated the presence of SARS-CoV-2 particles in a significant fraction of platelets as confirmed by immunogold labeling and immunofluorescence imaging of Spike and nucleocapsid proteins. Compared with platelets from healthy donors or patients with bacterial sepsis, platelets from patients with severe COVID-19 exhibited enlarged intracellular vesicles and autophagolysosomes. They had large LC3-positive structures and increased levels of LC3II with a co-localization of LC3 and Spike, suggesting that platelets can digest SARS-CoV-2 material by xenophagy in critically ill patients. Altogether, these data show that during severe COVID-19, platelets get activated, become partly desensitized, and develop a selective autophagy response.

SARS-CoV-2 Omicron variant infection affects blood platelets, a comparative analysis with Delta variant

“…Furthermore, platelets from severe patients infected with Omicron exhibited decreased a IIb b3 integrin activation following stimulation with some physiological agonists, along with a decrease in granules secretion. This partial desensitization suggests that, preactivated platelets display a hyporesponsive phenotype, which has also been observed in severe Delta infection (22,32,42). Thus, Omicron variant mutations have not eliminated the platelet phenotype previously described in severe patients infected with ancestral strains.…”

“…Despite the low presence of angiotensin-converting enzyme 2 (ACE2), the best documented receptor for SARS-CoV-2, in platelets, it has been demonstrated that platelets from COVID-19 patients contain viral particles ( 12 , 20 , 22 , 23 ) and can internalize SARS-CoV-2 in vitro through various pathways ( 12 , 20 ). In addition to SARS-CoV-2, other viruses such as dengue and influenza have been shown to infect megakaryocytes and be present in platelets ( 24 , 25 ).…”

Beyond Basic Characterization and Omics: Immunomodulatory Roles of Platelet-Derived Extracellular Vesicles Unveiled by Functional Testing

“…Therefore, exploration of the tunability of the PEVome in the context of the immune system is relevant for e.g., the possibility to tune the PEVs towards a defined profile, which would be of interest for the development of drug delivery systems or advanced molecular therapeutic products (AMTP) with innate therapeutic capacity 83 . Also, the high interest in the diagnostic biomarker use of PEVs still demands a better understanding of the variability of the PEVome and its relation to the PEV-inducing signal, whether it is e.g., viral by CLEC-2 84 , thrombotic, mediated by thrombin and collagen receptors 85 , or singularly by GPVI.…”

Breakthrough infections after COVID-19 vaccinations do not elicit platelet hyperactivation and are associated with high platelet–lymphocyte and low platelet–neutrophil aggregates

“…In our experimental settings the impaired αIIbβ3 activation persisted after removal of the plasma as if the platelets were changed irreversibly by the infection. Although SARS-CoV-2 RNA in not always measurable in serum [ 23 , 24 ], virus debris has been detected inside platelets from patients and has been associated with cell death [ 25 ] and to partial desensitization of αIIbβ3 [ 26 ]. Thus, one could speculate that when the virus becomes systemic, it can affect platelet function directly.…”