Convalescent COVID-19 patients are susceptible to endothelial dysfunction due to persistent immune activation

Chioh, Florence WJ; Fong, Siew-Wai; Young, Barnaby E; Wu, Kan-Xing; Siau, Anthony; Krishnan, Shuba; Chan, Yi-Hao; Carissimo, Guillaume; Teo, Louis LY; Gao, Fei; Tan, Ru San; Zhong, Liang; Koh, Angela S; Tan, Seow-Yen; Tambyah, Paul A; Renia, Laurent; Ng, Lisa FP; Lye, David C; Cheung, Christine

Numerous reports of vascular events after an initial recovery from COVID-19 form our impetus to investigate the impact of COVID-19 on vascular health of recovered patients. We found elevated levels of circulating endothelial cells (CECs), a biomarker of vascular injury, in COVID-19 convalescents compared to healthy controls. In particular, those with pre-existing conditions (e.g., hypertension, diabetes) had more pronounced endothelial activation hallmarks than non-COVID-19 patients with matched cardiovascular risk. Several proinflammatory and activated T lymphocyte-associated cytokines sustained from acute infection to recovery phase, which correlated positively with CEC measures, implicating cytokine-driven endothelial dysfunction. Notably, we found higher frequency of effector T cells in our COVID-19 convalescents compared to healthy controls. The activation markers detected on CECs mapped to counter receptors found primarily on cytotoxic CD8(+) T cells, raising the possibility of cytotoxic effector cells targeting activated endothelial cells. Clinical trials in preventive therapy for post-COVID-19 vascular complications may be needed.