In vitro and in vivo functional characterization of gutless recombinant SV40-derived CFTR vectors

In cystic fibrosis (CF), respiratory failure caused by progressive airway obstruction and tissue damage is primarily a result of the aberrant inflammatory responses to lung infections with Pseudomonas aeruginosa. Despite considerable improvement in patient survival, conventional therapies are mainly supportive. Recent progress toward gene therapy for CF has been encouraging; however, several factors such as immune response and transduced cell turnover remain as potential limitations to CF gene therapy. As alternative gene therapy vectors for CF, we examined the feasibility of using recombinant SV40-derived vectors (rSV40s), which may circumvent some of these obstacles. To accommodate the large cystic fibrosis transmembrane conductance regulator (CFTR) cDNA, we removed not only SV40 Tag genes, but also all capsid genes. We, therefore, tested whether 'gutless' rSV40s could be packaged and were able to express a functional human CFTR cDNA. The results from our in vitro analysis determined that rSV40-CFTR was able to successfully result in the expression of CFTR protein, which localized to the plasma membrane and restored channel function to CFTR-deficient cells. Similarly, in vivo experiments delivering rSV40-CFTR to the lungs of Cftr-/- mice resulted in a reduction of the pathology associated with intra-tracheal P. aeruginosa challenge. rSV40-CFTR-treated mice had less weight loss when compared with control-treated mice as well as demonstrably reduced lung inflammation as evidence by histology and reduced inflammatory cytokines in the broncho-alveolar lavage. The reduction in inflammatory cytokine levels led to an evident decrease in neutrophil influx to the airways. These results indicate that further study of the application of rSV40-CFTR to CF gene therapy is warranted.