CFTR and cystic fibrosis: To determine the effectiveness of a lentiviral (LV) gene therapy in live intact CF mice, we have used a well-established transepithelial PD technique in the nasal airways, originally based on the method described by Parsons et al. (2000), and subsequently used in a longitudinal study to measure the persistence of CFTR lentiviral airway gene therapy (Cmielewski et al., 2014).