Elevated Circulating Monocytes and Monocyte Activation in Pulmonary Post-Acute Sequelae of Sars-Cov-2 Infection

Monocytes and macrophages play a pivotal role in inflammation during acute SARS-CoV-2 infection. However, their contribution to the development of pulmonary post-acute sequelae of SARS-CoV-2 infection (PPASC) are not fully elucidated. To determine monocyte dysregulation and cytokines associated with PPASC, we analyzed plasma cytokine expression and circulating monocytes in COVID-19 convalescents [convalescents with PPASC (PG) and no symptoms (RG)], comparing them to uninfected individuals (NG). We found elevated plasma level of IL-1Ra expression, but FGF expression was reduced in PG, compared to NG. COVID-19 convalescents displayed increased monocyte levels and CD169+ monocytes. CD169+ monocyte subsets correlated with DLCOc% inversely and IL-1α, IL-1β, MIP-1α, Eotaxin, and IFNγ expression positively in PG. This study present evidence that COVID convalescents exhibit monocyte alteration beyond the acute COVID-19 infection period even in convalescents with no residual symptoms. Furthermore, monocyte alteration and increased activated monocyte subsets may impact pulmonary function in COVID-19 convalescents.