CD4 and cystic fibrosis: Alternatively, the Cas9/gRNA system could be delivered by a number of different virus vectors [46,47] which have been used to successfully delivery CFTR in large animal models [48,49], and are in pre-clinical development for a first-in-man CF trial [50]; the CCR5-edited autologous CD4 T cells successfully used to reduce levels of HIV RNA in patients were edited using ZFNs delivered by virus vectors [51].