SARS-CoV-2 Entry Genes Expression in Relation with Interferon Response in Cystic Fibrosis Patients

Abstract

The expression rate of SARS-CoV-2 entry genes, angiotensin-converting enzyme 2 (ACE2), the main viral receptor and the proteases, furin and transmembrane serine protease 2 (TMPRSS2) in cystic fibrosis (CF) individuals is poorly known. Hence, we examined their levels in upper respiratory samples of CF patients (n = 46) and healthy controls (n = 45). Moreover, we sought to understand the interplay of type I interferon (IFN-I) with ACE2, furin and TMPRSS2 by evaluating their gene expression with respect to ISG15, a well-known marker of IFN activation, in upper respiratory samples and after ex vivo IFNβ exposure. Lower ACE2 levels and trends toward the reduction of furin and TMPRSS2 were found in CF patients compared with the healthy controls; decreased ACE2 amounts were also detected in CF individuals with pancreatic insufficiency and in those receiving inhaled antibiotics. Moreover, there was a strong positive correlation between ISG15 and ACE2 levels. However, after ex vivo IFNβ stimulation of nasopharyngeal cells, the truncated isoform (dACE2), recently demonstrated as the IFN stimulated one with respect to the full-length isoform (flACE2), slightly augmented in cells from CF patients whereas in those from healthy donors, dACE2 levels showed variable levels of upregulation. An altered expression of SARS-COV-2 entry genes and a poor responsiveness of dACE2 to IFN-I stimulation might be crucial in the diffusion of SARS-CoV-2 infection in CF.

Expression of ACE2—a Key SARS-CoV-2 Entry Factor—Is Not Increased in the Nasal Mucosa of People with Cystic Fibrosis

“…Thus, our data set is one of the few to date to provide a direct assessment of ACE2 and TMPRSS2 in the nasal mucosa of PwCF and control subjects. Moreover, our data suggest that expression of ACE2 or its short isoform may not be affected by IFN signaling in vivo , which differs from the two previous studies showing that IFNs can increase ACE2 expression in vitro ( 6 , 17 ). Nevertheless, an additional validation study using orthogonal techniques would be required to confirm our findings.…”

“…Our analysis provides evidence that expression of ACE2 , a key entry factor on epithelial cells for SARS-CoV-2, is not different in the nasal epithelium between HVs and PwCF. Other groups have recently assessed ACE2 expression in the airways of PwCF ( 17 – 18 ). Hou and colleagues performed single-molecule fluorescence in situ hybridization for ACE2 and TMPRSS2 in lungs explanted from PwCF with end-stage disease and control donor lungs but did not quantify ACE2 expression or assess nasal epithelium ( 19 ).…”

“…In contrast to our findings, reanalysis of publicly available data sets from PwCF by Stanton and colleagues demonstrated increased expression of ACE2 and decreased expression of TMPRSS2 , but the original studies were performed on cultured airway cells rather than on primary cells obtained from PwCF ( 18 ). Using quantitative PCR and oropharyngeal swabs, Bitossi and colleagues reported decreased expression of ACE2 in PwCF ( 17 ). It is important to note that analysis in both studies was done without adjustment for sample composition, which, as we have shown in the case of TMPRSS2 , can affect expression results.…”

Mechanisms by which the cystic fibrosis transmembrane conductance regulator may influence SARS‐CoV‐2 infection and COVID‐19 disease severity

“…TMPRSS2 RNA expression was variable (Figure 1A), but (unlike ACE2) demonstrated moderate correlation with SARS‐CoV‐2 replication (Figure 1B, R 2 = .76), compatible with importance of secreted proteases during the viral infectious cycle 30,81 . Protease/anti‐protease imbalance is well established in CF airways in vivo, 82–91 and the possibility that clinical features of CF lung disease related to protease activity might influence SARS‐CoV‐2 infection has been suggested previously 32,39 . As expected, F508del CFTR mRNA levels were similar to wild type (p = .440), that is, the F508del variant elicits a protein folding abnormality without markedly altering CFTR mRNA abundance (Figure 1A).…”

“…[29][30][31] Specific features of CFTR cellular biology have been postulated as a link between CF and COVID-19 severity. [32][33][34][35][36][37][38][39] For example, pre-pandemic studies of airway biology described CFTR localization in clathrin-coated pits (same location as the coronaviral receptor), debated CFTR as a regulator of endosomal pH (and therefore potentially contributing during viral proteolysis and/or uncoating), demonstrated CFTR regulation of airway mucosal pH, and showed local chloride concentration to be important during receptor attachment of other coronaviruses. [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] Any of these factors might be taken to suggest mechanistic connections between CFTR and coronaviral pathogenesis.…”