An imaging flow cytometry method to study platelet-monocyte aggregates using Long COVID as a model
Background
Long COVID is characterised by persistent systemic inflammation and endothelial dysfunction, with increasing evidence implicating thromboinflammatory mechanisms. Platelet-monocyte aggregates (PMA) represent a sensitive marker of platelet activation and immune-vascular interactions, but their role in Long COVID remains incompletely defined.
Methods
This study quantified circulating PMA in 20 Long COVID patients and 20 healthy controls using a two-colour imaging flow cytometry assay targeting CD14 (a monocyte receptor for pathogen-associated molecular patterns, PAMPs) and CD62P (P-selectin).
PMA were expressed as a percentage of total monocytes, and platelet attachment patterns were classified into single versus multiple platelet binding. Statistical analyses included Shapiro-Wilk normality testing, unpaired t-tests, Mann-Whitney U tests or two-way ANOVA as appropriate, and linear regression for correlation analysis.
Results
Circulating PMA were significantly elevated in Long COVID patients compared with controls (29.19 [20.02-37.26] vs 4.59 [2.67-7.16], p < 0.0001).
Long COVID samples showed a reduced proportion of monocytes with single platelet attachment and a corresponding increase in multiple platelet binding (p < 0.0001).
In controls, %PMA increased with age (p < 0.01), whereas no age association was observed in Long COVID, indicating an elevated baseline independent of age.
Conclusions
Long COVID is associated with markedly increased platelet-monocyte aggregation and altered platelet attachment dynamics, consistent with sustained thromboinflammatory activity. PMA represent a sensitive cellular marker of platelet-driven immune activation and may have utility as an accessible biomarker for stratifying thromboinflammatory burden in Long COVID.
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Thompon, Anel; Venter, Chantelle; de Villiers, Willem JS; De Swardt, Dalene; Laubscher, Gert J; Kell, Douglas B; Pretorius, Etheresia
Background
Long COVID is characterised by persistent systemic inflammation and endothelial dysfunction, with increasing evidence implicating thromboinflammatory mechanisms. Platelet-monocyte aggregates (PMA) represent a sensitive marker of platelet activation and immune-vascular interactions, but their role in Long COVID remains incompletely defined.
Methods
This study quantified circulating PMA in 20 Long COVID patients and 20 healthy controls using a two-colour imaging flow cytometry assay targeting CD14 (a monocyte receptor for pathogen-associated molecular patterns, PAMPs) and CD62P (P-selectin).
PMA were expressed as a percentage of total monocytes, and platelet attachment patterns were classified into single versus multiple platelet binding. Statistical analyses included Shapiro-Wilk normality testing, unpaired t-tests, Mann-Whitney U tests or two-way ANOVA as appropriate, and linear regression for correlation analysis.
Results
Circulating PMA were significantly elevated in Long COVID patients compared with controls (29.19 [20.02-37.26] vs 4.59 [2.67-7.16], p < 0.0001).
Long COVID samples showed a reduced proportion of monocytes with single platelet attachment and a corresponding increase in multiple platelet binding (p < 0.0001).
In controls, %PMA increased with age (p < 0.01), whereas no age association was observed in Long COVID, indicating an elevated baseline independent of age.
Conclusions
Long COVID is associated with markedly increased platelet-monocyte aggregation and altered platelet attachment dynamics, consistent with sustained thromboinflammatory activity. PMA represent a sensitive cellular marker of platelet-driven immune activation and may have utility as an accessible biomarker for stratifying thromboinflammatory burden in Long COVID.
Web | DOI | PDF | bioRxiv | Preprint