Development and Analysis of Recombinant Adenoviruses for Gene Therapy of Cystic Fibrosis

Abstract

A new adenovirus-based vector (Ad2/CFTR-1) has been constructed in which the cDNA encoding the cystic fibrosis transmembrane conductance regulator (CFTR), the cystic fibrosis (CF) gene product, replaces the early region 1 coding sequences, E1a and E1b. The virus retains the E3 region. Ad2/CFTR-1 and a related construct encoding β-galactosidase replicate in human 293 cells which provide E1 gene functions in trans. Replication of these recombinant viruses was not detected in a variety of other cells, although very limited viral DNA synthesis and transcription from the E4 and L5 regions could be measured. These E1-deletion vectors were also deficient in cellular transformation, shut-off of host cell protein synthesis, and production of cytopathic effects, even at high multiplicities of infection. Ad2/CFTR-1 produced CFTR protein in a variety of cells including airway epithelia from CF patients. Expression of functional CFTR protein in a CF airway epithelial monolayer was detected by correction of the CI¯ transport defect characteristic of CF. Surprisingly low multiplicities of infection (0.1 moi) were sufficient to generate CFTR Cl¯ current across a CF epithelial monolayer in vitro. These data, together with the lack of obvious toxicity, suggest that Ad2/CFTR-1 should be suitable for CF gene therapy.

Overview summary

Gene therapy for cystic flbrosis (CF) will likely require delivery of a normal CF gene to the airway epithelia of CF patients. Here we report the construction of a new adenovirus-based vector, Ad2/CFTR-1, designed for this purpose. This vector is derived from adenovirus type 2 and lacks most of the E1 region coding sequences. In place of the E1 sequence, cDNA encoding CFTR, the CF gene product, is substituted. Unlike many E1-deletion vectors, the construct retains the entire E3 region. We present data on some aspects of the viral life cycle in tissue culture cells and demonstrate the ability of this vector to complement the defect in transepithelial Cl¯ secretion characteristic of human CF airway epithelial cells.