V.E.2. The assessment of efficacy will focus primarily on measurement of: 
V.E.2.a. Transepithelial potential difference across the nasal 
epithelium. 
Patients with CF have a raised PD, a low basal Cl' permeability, and little 
response to cAMP-mediated agonists that stimulate Cl" secretion across normal 
nasal epithelium. The abnormalities in CF nasal epithelium are well characterized 
in vivo in our laboratory, and correction of these basal abnormalities would suggest 
that recombinant virus has complemented the CF gene defect and corrected the ion 
transport abnormality. Measurement of nasal PD has been repetitively used in our 
lab without difficulty. It is a non-invasive test that can be performed serially without 
damage to the nasal epithelium. Briefly, the exploring electrode is a PE50 tubing 
that is perfused sequentially with either a Ringer solution or drug solutions to test 
for Cl" secretion. The reference electrode is a 4% agar/Ringer solution in a 21 
gauge needle that is placed in the subcutaneous space. Potential difference is 
measured between balanced calomel half-cell electrodes and using a high 
impedance voltmeter. This technique has been employed hundreds of times at 
UNC without complications. 
V.E.2.b. Immunocytochemical detection of transduced CFTR 
Efficacy will also be assessed in terms of evidence of CFTR protein 
production and localization at the apical membrane by immunocytochemistry using 
antibodies against CFTR. These will be performed on nasal epithelial specimens 
using a small cytology brush, nasal epithelia using a "scrape-biopsy" technique, and 
on standard nasal biopsy specimens. Nasal epithelial specimens will also be tested 
for the presence of mRNA by PCR techniques. 
Recombinant DNA Research, Volume 17 
[493] 
