(439) CFTR impairment strongly decrease SARS-CoV-2 replication in human bronchial epithelial cells

Background: People with cystic fibrosis should be considered at increased risk of developing severe symptoms in case of COVID-19. Surprisingly, reduced spread of SARS-CoV-2 and milder COVID-19 symptoms have been reported in these subjects, suggesting complex regulation of SARS-CoV-2 replication. We analysed SARS-CoV-2 replication in wild-type and CFTR-modified human bronchial epithelial cell lines and primary cells in order to shed light on possible mechanisms involved in the peculiar characteristics of SARS-CoV-2 infection in people with cystic fibrosis.

Methods: Primary human bronchial epithelial cells expressing wild-type or F508del CFTR and newly developed immortalized

CRISPR/Cas9 CFTR ablated clones

were infected with SARS-CoV-2, and real-time RT-PCR was used to evaluate viral load in both supernatant and cell extracts at different time points. To access CFTR involvement, its function was inhibited in wild-type cells with the CFTR-specific inhibitor iOWH032 and partially restored (up to 50%) in F508del expressing cells with a combination of CFTR modulators (VX-661+VX-445). SARS-CoV-2 receptor ACE-2 expression and localization were investigated by both western blotting, flow cytometry and immunofluorescence.

Results: CFTR-modified bronchial cells, compared with wild-type cell lines, showed a reduced replication of SARS-CoV-2 . Moreover, ACE-2 expression at 72 hours post infection was higher in wild-type compared to CFTR-modified cells. Furthermore, by inhibiting CFTR channel function a significant inhibition of viral replication in cells with wild-type CFTR was achieved, and by correcting CFTR function in F508del expressing cells an increase in SARS-CoV-2 viral particles release was detected. Ultrastructural analysis by transmission and scanning electron microscopy revealed a different morphology of viral replication structures, in particular higher number of autophagosomes and altered multivesicular cytoplasmatic structures were present in CF cells.

Conclusions: CFTR expression/function is involved, either directly or indirectly, in the regulation of SARS-CoV-2 replication, thus providing novel insights into the role of CFTR and the development of therapeutic strategies for SARS-CoV-2 infection.

Acknowledgements: The present study was supported by Fondazione Cariverona, ENACT project VIRO-COVID and by Lega Italiana Fibrosi Cistica onlus (C.S.)

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