Elevated circulating monocytes and monocyte activation in COVID-19 convalescent individuals

Area of Science:

• Immunology
• Infectious Diseases
• Pulmonology

Background:

• Monocytes and macrophages are key in acute SARS-CoV-2 inflammation.
• Their role in post-acute sequelae of SARS-CoV-2 infection (PASC) requires further investigation.

Purpose of the Study:

• To compare plasma cytokine and monocyte levels in individuals with pulmonary PASC, recovered from SARS-CoV-2, and SARS-CoV-2 negative controls.
• To investigate monocyte subset distribution and activation markers in relation to pulmonary function post-COVID-19.

Main Methods:

• Cross-sectional study comparing three groups: pulmonary PASC (PG), recovered (RG), and negative (NG).
• Plasma cytokines measured by Luminex assay; monocyte subsets and CD169 expression analyzed by flow cytometry.

Main Results:

• Elevated IL-1Ra and reduced FGF in PG vs. NG.
• Increased monocyte counts and CD169 expression on intermediate and non-classical monocytes in PG and RG compared to NG.
• CD169+ intermediate monocytes correlated negatively with lung function (DLCOc%); CD169+ non-classical monocytes correlated with inflammatory cytokines.

Conclusions:

• COVID-19 convalescents show persistent monocyte alterations, irrespective of residual symptoms.
• Altered monocytes and increased activated subsets may impair pulmonary function in post-COVID conditions.
• Findings offer insights into PASC immunopathology and potential therapeutic targets.