CFTR knock-out (KO) ferrets (Sun et al., 2008) and pigs (Rogers et al., 2008) recapitulate many features of the lung disease phenotype observed in humans with CF. Lentivirus-, rAd- and rAAV-mediated CFTR lung gene transfer in CFTR-KO pigs have demonstrated the proof-of-concept for gene therapy in the hostile environment of CF lungs (Cooney et al., 2016; Steines et al., 2016; Cooney et al., 2018b). The gene discussed is CFTR; the disease is cystic fibrosis.