ABSTRACT
Cystic fibrosis (CF) has been a primary focus for gene therapy of lung diseases because
the genetic cause is known and the airway epithelium is accessible for direct deoxyribonucleic
acid (DNA) delivery. Soon after the mutated gene was identified in 1989, investigators
demonstrated that transfer of a normal copy of the CF gene corrected ion transport
abnormalities, thus validating the potential for use of gene therapy for this autosomal
recessive disease. However, subsequent studies in a variety of in vitro and animal
models, and more limited human studies, have revealed several obstacles to gene therapy
for CF: (1) The incomplete understanding of CF lung disease pathogenesis, particularly
the relative importance of ion transport and other cellular abnormalities (including
glycoconjugate processing, pH regulation of intracellular organelles, and membrane
trafficking), and of surface epithelial versus submucosal gland CF transmembrane regulator
(CFTR) expression, generates uncertainty as to the necessary target cells for gene
transfer and the optimum end point(s) for short-term human studies. (2) The airway
epithelium has protective barriers against viral infection that impair gene transfer
with several vectors, including recombinant viruses and DNA conjugates. Improvement
in DNA transfer technology will be necessary for successful gene therapy. (3) Immune
responses to recombinant viruses and inflammatory effects of bacterial DNA are only
partially understood and appear to limit efficacy, particularly with repeated administration.
Identification of these obstacles is prerequisite for progress, and recent studies
with novel DNA delivery methods appear promising.
KEYWORDS
Gene therapy - cystic fibrosis - airway epithelium - adenovirus - adeno-