Biological profiles of nasal epithelium in long COVID

<bold>Objective:</bold> The nasal epithelium(NE) is the primary site of infection for SARS-CoV-2, however little is known about its role in long COVID(LC). Therefore, this study aimed to investigate its biological profiles to unravel pathophysiological mechanisms of LC. <bold>Methods:</bold> Medical data and NE were collected from LC patients at 3-6 months post-COVID. Transcriptomes were explored using hierarchical clustering to identify transcriptomic and cellular clusters. Patients with and without pulmonary radiological abnormalities(PRA) were compared using a supervised approach. CRISPR-Cas9 gene-editing was used for functional validation. NE was cultured at air-liquid-interface and exposed to viral RNA analogue poly(I:C) and interferon-g(IFNg). Phenotype and function of NE and innate lymphoid cells(ILC) were analyzed from LC patients and healthy controls(HC) using molecular biology techniques. <bold>Results:</bold> Transcriptomic(n=2) and cellular(n=2) clusters of NE were identified and related to inflammation and ciliogenesis. In patients with PRA, <italic>SMURF1</italic> was significantly upregulated. <italic>SMURF1</italic>-/- mutant NE cells showed significantly decreased inflammatory cytokine production upon viral stimulation. In LC NE compared to HC, the gene expression of pro-inflammatory cytokines was increased at baseline and after stimulation. Increased frequencies of IFNg-producing ILCs were found in the blood of LC patients, that <italic>in vitro</italic> produced more IFNg after exposure to epithelium-derived IL-1b compared to HC. <italic>Ex vivo</italic>, this NE inflammatory state resulted in reduced barrier function and enhanced regeneration potential in LC. <bold>Conclusion:</bold> Inflammatory profiles of NE were found in LC. This study shows the need to further assess and validate <italic>SMURF1</italic> and IL-1b for the disease management of LC.