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VIIA.2. Nasal PD 
Nasal PD studies have been performed -1,000 times at UNC over the past 
decade without significant incident. There is the possibility of infection at the site of 
subcutaneous reference needle insertion; this has not occurred over the past 10 
years at UNC. Drug sensitivity to amiloride or isoproterenol is a risk, but we have 
not observed such an event. We have had several patients suffer vaso-vagal 
reactions during the procedure; these are handled by placing the patient in a 
recumbent position, and all have recovered with no adverse effect. 
VIIA.3. Ectopic or overexpression of CFTR 
We have performed a series of studies to address these issues. The most 
compelling experiments involved the generation of transgenic mice that had been 
programmed to express high levels of human CFTR in the airway. One set of 
animals expressed CFTR from a promoter of the SPC gene that is very active in the 
distal airway including the alveolar cells and the distal bronchiolar cells. Another 
set of animals expressed CFTR from a promoter of the CC10 gene that is very active 
in most of the cells of the proximal airway. All of the transgenic lines expressed 
high levels of human CFTR protein (which is active in mouse cells) in the 
appropriate cells and none of them demonstrated pathology or clinical 
abnormalities. This suggests that expression of recombinant CFTR in the wrong cell 
or unregulated, overexpression in the correct cell will not be deleterious. These 
studies are complemented by studies in human airway cell lines that indicate no 
toxic effects of overexpression of CFTR on growth characteristics and cell volume 
regulation. 
VIIA.4. Replication of the virus and expression of viral proteins 
Ad5-CB-CFTR has been engineered in a way that the region responsible for 
activating its transcriptional units, called El, has been deleted. In principle, 
therefore, the recombinant genome should not replicate or express viral proteins in 
the recipient cell. In practice, certain cell types under special conditions can 
transactivate the viral genes using endogenous cellular factors. 
We have established a model of the CF airway that is based on the growth of 
human airway epithelial xenografts in nu/nu mice to better address these important 
issues in a relevant biological setting. This model was used to evaluate the 
possibility of viral protein expression and replication of the El deleted CFTR virus 
in the context of a human CF epithelium. These studies failed to detect viral 
protein expression. A low level of ongoing replication of the virus in human 
xenografts that were stably expressing the recombinant gene has been detected. 
Thus, low level replication can occur in human airway epithelia housed in an 
immunocompromised host (the nu/nu mouse). The possibility of low level 
replication was subsequently tested in a species closely related to humans (baboon). 
In the baboon, no replication of virus was detected in protocols that span the viral 
doses employed in this study. However, the baboon may be relatively incompetent 
for adenovirus infection, and a series of studies are underway in a species that is 
clearly competent for adenovirus 5 infection, i.e., the cotton rat. Low level 
replication is not seen with wild type adenovirus in immunocompetent hosts, and we 
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Recombinant DNA Research, Volume 17 
