Deleterious effect of P. aeruginosa on F508del-CFTR rescued by Elexacaftor/Tezacaftor/Ivacaftor is clinical-strain dependent in patient-derived nasal cells

The triple cystic fibrosis transmembrane conductance regulator (CFTR) modulators combination Elexacaftor/tezacaftor/ivacaftor (ETI) has been approved for people with CF (pwCF) bearing at least one F508del allele. Despite the development of CFTR modulators having dramatically improved respiratory outcomes in pwCF, clinical studies have showed variable responses to this drug formulation. Of note, airway inflammation and bacterial colonisation persist in the upper and lower respiratory tract even in ETI treated patients. Therefore, we first tested the clinical exoproducts (EXO) of P. aeruginosa isolated from 15 CF patient in WT and F508del-CFTR CF bronchial epithelial (CFBE) cells and found that EXO variably decreased WT-, F508del- and ETI-dependent F508del-CFTR function and increased proinflammatory cytokines and ROS levels in a clinical strain-specific manner. We were then prompted to evaluate the effects of EXO in ex-vivo patient-derived tissues. Therefore, we cultured primary nasal epithelial (HNE) cells with EXO isolated from the corresponding pwCF to mimic the native status of CF airway. Similarly, we observed a variable reduction of F508del-CFTR function in presence or absence of ETI and upregulation of proinflammatory cytokines and ROS levels. Interestingly, HNE cells treated with EXO isolated from the corresponding donor and 3 different pwCF, showed a variable reduction of ETI-dependent F508del-CFTR function mainly due to clinical strains with limited effect of patient background. Furthermore, we demonstrated that ETI pretreatment decreased the cytokines and ROS levels down to the levels of uninfected cells. These pre-clinical studies suggest that in-vitro screening of patient-specific response to CFTR modulators under infection/inflammation conditions, could prove to be a valuable tool to enhance the prediction of clinical response.