Acute responses of non-human primates to airway delivery of an adenovirus vector containing the human cystic fibrosis transmembrane conductance regulator cDNA

Recombinant human adenovirus (Ad) vectors are leading candidates for human gene therapy for cystic fibrosis (CF) based on demonstration of efficient transfer of exogenous genes to rodent respiratory epithelium in vivo and human respiratory cells in vitro. The safety of Ad-mediated gene transfer to the respiratory epithelium and acute (up to 21 days) clinical responses to airway delivery of a replication-deficient recombinant, E1^-, E3^- Ad type 5-based vector containing the human cystic fibrosis transmembrane conductance regulator cDNA (Ad-CFTR) were evaluated in rhesus monkeys. Airway delivery of an Ad vector with the lacZ marker gene demonstrated β-galactosidase expression in epithelial cells. Animals administered intratracheal Ad-CFTR demonstrated human CFTR cDNA expression in airway epithelial cells. Animals administered Ad-CFTR intranasal, and 24 hr later, intrabronchial [2 x 10⁷ to 5 x 10¹⁰ plaque-forming units (pfu), n= 12], in a fashion similar to a proposed human protocol, or only intrabronchial (10¹¹ pfu, n = 3), had no significant changes in clinical parameters compared to vehicle controls (n = 6). Microscopic analysis of the lung by necropsy or bronchoalveolar lavage demonstrated a dose-dependent increase in inflammatory cells, primarily lymphocytes, in the area where Ad-CFTR was delivered, which persisted for at least 2 months in some animals. Serum anti-Ad type 5 neutralizing antibody titers did not rise and shed Ad was not detected. The presence of Ad-CFTR DNA, analyzed by the polymerase chain reaction (PCR), was not detected in organs outside the lung. These data demonstrate that Ad-CFTR is well tolerated in non-human primates, although there is dose-dependent inflammation in the lung not clinically apparent. This suggests that delivery of Ad vectors for human gene therapy may be dose limited.