J. Glasspool-malone et Rw. Malone, Marked enhancement of direct respiratory tissue transfection by aurintricarboxylic acid, HUM GENE TH, 10(10), 1999, pp. 1703-1713
Simple, nontoxic, and pharmaceutically defined methods for genetic modifica
tion of respiratory tissues may enable development of a variety of molecula
r medicines. Clinical applications for such medicines include treatment of
inborn errors of metabolism, interventions for asthma and iatrogenic pulmon
ary fibrosis, and disease prophylaxis via mucosal polynucleotide vaccinatio
n. "Free," "direct," or "naked" plasmid adminstration is a simple, apparent
ly safe, and pharmaceutically defined gene delivery method. Murine, macaque
, and clinical human studies have demonstrated transfection of respiratory
tissues after direct application of free plasmid. The aim of this study was
to develop a simple and safe alternative to respiratory tissue transductio
n, and specifically to provide a theoretical framework for developing a cat
egory of adjuvants, nuclease inhibitors, that augment the transfection acti
vity of free plasmid. Plasmid employing the human CMV IE promoter/enhancer
to drive expression of the Photinus pyralis luciferase reporter protein was
administered intratracheally into mouse lung with or without the nuclease
inhibitor aurintricarboxylic acid (ATA). Lavage samples and tissue extracts
were used to demonstrate inhibition of lung nuclease activity. ATA dose es
calation studies were performed using lung homogenate assays to characteriz
e transfection. Potential toxicity was assessed histologically. The data in
dicate that nucleases present in respiratory fluids accelerate clearance of
biologically active plasmid from lung, that intratracheal coadministration
of ATA together with plasmid reduces extracellular DNA clearance, and that
this treatment results in marked enhancement of reporter protein expressio
n. The effective dose for ATA enhancement of direct lung transfection was 0
.5 mu g/g mouse weight, and the LD50 was approximately 6 mu g/g. These find
ings provide a theoretical and practical foundation for further development
of an alternative gene delivery system: free plasmid-based respiratory tra
nsfection technology.