ABSTRACT
The long term consequences of severe COVID-19 in the lungs remain speculative, however interstitial abnormalities in these patients may arise. In this study previously identified fibrotic markers from the BAL were evaluated in PostCOVID-19 patients. 26 patients were referred for evaluation of respiratory symptoms and/or abnormalities on HRCT, on average 5.3 months from the acute disease phase, to the Post COVID-19 clinic. 20 patients showed persistent radiological findings with fibrotic changes and/or altered respiratory function. Bronchoalveolar lavage cellular composition was determined by MGG staining and CD45, CD14, CD11c, CD163 and Osteopontin staining. Airway monocytes were identified by SSClo/CD45+ parameters and surface expression of CD11c, CD14 and CD16 by flow cytometry. FVC% and DLCO% were used as measures of disease severity. Collectively, monocyte percentages in the BAL were associated with lower FVC% (Rs=-0.53,p=0.02). Importantly, patients with DLCO% below 60 showed higher monocyte infiltration (p=0.015). CD14 positivity on monocytes was more pronounced in patients with DLCO% below 60, while CD16 and CD11c were not associated with DLCO. Increased Osteopontin expression in airway macrophages was also linked with lower DLCO% levels (Rs=-0.661, p=0.019), in contrast to CD163 macrophage expression which tended to be higher in patients with higher DLCO%. Neutrophils were negatively associated with DLCO% in Post-COVID-19 patients (Rs=-0.62,p=0.01). Airway immune cell populations from BAL were associated with Post-COVID-19 induced altered respiratory function.