Repeat administration of DNA/liposomes to the nasal epithelium of patientswith cystic fibrosis

The major cause of mortality in patients with cystic fibrosis (CF) is lung disease. Expression of the cystic fibrosis trans-membrane conductance regul ator (CFTR) gene product in the airways is a potential treatment. Clinical studies in which the CFTR cDNA was delivered to the respiratory epithelia o f OF patients have resulted in modest transient gene expression. it seems l ikely that repeated administration of the gene transfer vector will be requ ired for long-term gene expression. We have undertaken a double-blinded stu dy in which multiple doses of a DNA/liposome formulation were delivered to the nasal epithelium of CF patients. Ten subjects received plasmid DNA expr essing the CFTR cDNA complexed with DC-Chol/DOPE cationic liposomes, whilst two subjects received placebo. Each subject received three doses, administ ered 4 weeks apart. There was no evidence of inflammation, toxicity or an i mmune response towards the DNA/liposomes or the expressed CFTR. Nasal epith elial cells were collected 4 days after each dose for a series of efficacy assays including quantitation of vector-specific DNA and mRNA, immunohistoc hemistry of CFTR protein, bacterial adherence, and detection of halide effl ux ex vivo. Airway ion transport was also assessed in vivo by repeated nasa l potential difference (PD) measurements. On average, six of the treated su bjects were positive for CFTR gene transfer after each dose. All subjects p ositive for CFTR function were also positive for plasmid DNA, plasmid-deriv ed mRNA and CFTR protein. The efficacy measures suggest that unlike high do ses of recombinant adenoviral vectors, DNA/liposomes can be successfully re -administered without apparent loss of efficacy.