Late Breaking Abstract - Characteristics of Post-COVID-19 interstitial lung syndrome in Bronchoalveolar Lavage: Preliminary results

The long term consequences of severe COVID-19 in the lungs remain speculative, however interstitial abnormalities in these patients may arise and develop into pulmonary fibrosis. In this study previously identified fibrotic markers from the BAL were compared in Post-COVID-19 patients and other ILDs. 8 Post-COVID-19 patients were referred for evaluation 3-6 months from the acute disease phase, to the ILD clinic, since February 2021. Two patients showed mild ground glass opacities with normal DLCO%, and all six other patients had variable extent of fibrosis. ILD patients included 8 IPF, 10 CHP, 8 CVD-ILD and 4 controls. BAL cellular composition was determined by MGG staining and CD45, CD14, CD11c and CD163 staining. Monocytes were identified by SSC/CD45 parameters by flow cytometry and percentages of CD11c, CD14 monocytes were calculated. Col1a and OPN expression was measured by immunofluorescence. DLCO% was used as a measure of disease severity at baseline. Collectively, monocyte levels were associated with lower DLCO% (Rs=-0.46, p=0.013) and a similar trend was observed for the ILD groups. Importantly, IPF and Post-COVID-19-ILD patients had more monocytes than controls (p=0.008 and 0.05). Monocyte population showed high CD11c positivity (>95%) in all samples and variable CD14 levels. Higher CD14 positive monocytes were associated with lower DLCO% in ILDs (Rs=-0.5, p=0.0065). Neutrophils and eosinophils were negatively associated with DLCO% in fibrotic patients (Rs=-0.46, p=0.013, and Rs=-0.4, p=0.033) and a similar trend was observed for the Post-COVID-19-ILD group. Col1a and OPN were elevated in the Post-COVID-19-ILD group as previously described for fibrotic patients.