Immunofibrotic drivers of impaired lung function in postacute sequelae of SARS-CoV-2 infection

BACKGROUND. Individuals recovering from COVID-19 frequently experience persistent respiratory ailments, which are key elements of postacute sequelae of SARS-CoV-2 infection (PASC); however, little is known about the underlying biological factors that may direct lung recovery and the extent to which these are affected by COVID-19 severity. METHODS. We performed a prospective cohort study of individuals with persistent symptoms after acute COVID-19, collecting clinical data, pulmonary function tests, and plasma samples used for multiplex profiling of inflammatory, metabolic, angiogenic, and fibrotic factors. RESULTS. Sixty-one participants were enrolled across 2 academic medical centers at a median of 9 weeks (interquartile range, 6-10 weeks) after COVID-19 illness: n =13 participants (21%) had mild COVID-19 and were not hospitalized, n = 30 participants (49%) were hospitalized but were considered noncritical, and n =18 participants (30%) were hospitalized and in the intensive care unit (ICU). Fifty-three participants (85%) had lingering symptoms, most commonly dyspnea (69%) and cough (58%). Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and diffusing capacity for carbon monoxide (DLCO) declined as COVID-19 severity increased (P < 0.05) but these values did not correlate with respiratory symptoms. Partial least-squares discriminant analysis of plasma biomarker profiles clustered participants by past COVID-19 severity. Lipocalin-2 (LCN2), MMP-7, and HGF identified by our analysis were significantly higher in the ICU group (P < 0.05), inversely correlated with FVC and DLCO (P < 0.05), and were confirmed in a separate validation cohort (n = 53). CONCLUSION. Subjective respiratory symptoms are common after acute COVID-19 illness but do not correlate with COVID-19 severity or pulmonary function. Host response profiles reflecting neutrophil activation (LCN2), fibrosis signaling (MMP-7), and alveolar repair (HGF) track with lung impairment and may be novel therapeutic or prognostic targets.

Automated summary

This study found that biological factors related to neutrophil activation, fibrosis signaling, and alveolar repair may be novel therapeutic or prognostic targets for individuals recovering from COVID-19 with persistent respiratory symptoms.