CFTR cDNA to the respiratory epithelium in vivo in experimental animals are 
double stranded DNA circular DNA plasmids combined with liposomes 
(Yoshimura et al . , 1992). However, the extent of expression with this 
vector system is very limited, with no possibilities of therapeutic benefit 
to the individual. Further, this limited expression can be achieved only 
with very large amounts of DNA (equivalent to 500 mg for a 50 kg human) . Of 
the other vector systems considered (retrovirus, adeno-associated virus, 
naked plasmid, plasmid linked to ligand, plasmid delivered in association 
with adenovirus or fragments of adenovirus, vaccinia, or influenza), there 
is currently no in vivo evidence that any will work in the required fash- 
ion. 
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Recombinant DNA Research, Volume 16 
