Pathophysiological Mechanisms of PASC: Inflammatory Mediators of Endothelial Dysfunction in the RECOVER Cohort

Introduction: The goal of our ROA (Kraig, Kellogg, Seals) was to determine whether development of Long COVID in subjects previously infected with SARS-CoV-2 was associated with endothelial dysfunction and/or inflammatory sequelae. Aim 1 was a longitudinal study of 165 subjects while Aim 2 focused on 58 participants with additional physiological data (EndoPAT). Data were analyzed and stratified by sex and age.

Objective: Our objective is to determine whether endothelial dysfunction, due to the over-arching inflammation seen with SARS-CoV-2 infection, plays a seminal role in the development and progression of Long COVID pathologies.

Methods: Aim 1. Sera, collected longitudinally from 165 RECOVER subjects (at the 0, 3, and 6 month time points), were analyzed for biomarkers of inflammation [VCAM-1, sICAM-1, IL-6, IL-1Ra, sRAGE], autoimmune activation [antibodies to ACE2], and endothelial dysfunction [using an ex vivo assay]. In addition, RNAs from PBMCs collected at the same visits were analyzed by qPCR for p21 RNA levels, a marker of cellular senescence. All subjects studied had been infected with SARS-CoV-2 prior to specimen collection and a few had subsequent secondary infections as well. Aim 2. A subset of 58 RECOVER subjects (with or without Long COVID symptoms) who had undergone EndoPAT, a non-invasive in vivo measure of endothelial function, was studied further in order to correlate the biomarker measures with physiological indicators of endothelial dysfunction. Sera from these subjects were analyzed as described above and results are being compared to the clinical parameters using the 7 Bridges platform.

Results: Of the 165 RECOVER subjects studied, 104 had developed symptoms of Long COVID while 61 had not. As expected, sex was a predictor of Long COVID; females out-numbered males 83♀:21♂ compared to 31♀:30♂ in the recovered group. Although most biomarkers showed no significant correlation with Long COVID, two cytokines, IL-1RA and sICAM-1, remained at higher levels in the affected individuals. Both had been previously associated with acute infection. Correlation studies for the markers tested and clinical indicators of cardiovascular pathology showed relatively weak interactions. Ongoing analysis of the tier-3-data may provide more insights.

Conclusion/Discussion: Certain circulating inflammatory markers, specifically IL-1RA and sICAM-1, remain at higher levels in those subjects that develop symptoms of Long COVID; these differences did not diminish over the 6-month time frame examined, nor did they appear to correlate with specific Long COVID symptoms. Further analysis of later time points and more clinical indicators would be beneficial.

Key Topics:

• Assay and in vitro studies to gain mechanistic insights
• Biomarker, in-depth phenotyping assays and in vitro studies using tissue and other biospecimens