Plasma Extracellular Vesicles Derived from Pediatric COVID-19 Patients Modulate Monocyte and T Cell Immune Responses Based on Disease Severity

Abstract

Background: The COVID-19 pandemic has caused significant morbidity and mortality globally. The role of plasma-derived extracellular vesicles (EVs) in pediatric COVID-19 patients remains unclear. Methods: We isolated EVs from healthy controls (n = 13) and pediatric COVID-19 patients (n = 104) with varying severity during acute and convalescent phases using serial ultracentrifugation. EV effects on healthy PBMCs, naïve CD4+ T cells, and monocytes were assessed through in vitro assays, flow cytometry, and ELISA. Results: Our findings indicate that COVID-19 severity correlates with diverse immune responses. Severe acute cases exhibited increased cytokine levels, decreased IFNγ levels, and lower CD4+ T cell and monocyte counts, suggesting immunosuppression. EVs from severe acute patients stimulated healthy cells to express higher PDL1, increased Th2 and Treg cells, reduced IFNγ secretion, and altered Th1/Th17 ratios. Patient-derived EVs significantly reduced proinflammatory cytokine production by monocytes (p