Gene therapy as a treatment modality for the respiratory manifestations of CF raises several 
questions with regard to the overall safety of the procedures involved in the clinical protocol. 
These concerns can be broadly grouped into issues related to 1) routine clinical procedures 
usually performed in individuals with cystic fibrosis such as phlebotomy, radiologic studies, 
bronchoscopy and bronchoalveolar lavage; 2) the tissue location and level of expression of the 
normal CFTR protein; 3) the in vivo use of a replication deficient recombinant adenoviral vector 
to transduce respiratory epithelial cells such as issues of replication of the vector, induction of 
immune response either from the material administered or from the expression of endogenous 
viral genes; safety issues for the patient related to alterations in respiratory epithelial cell 
function other than those related to aberrant levels of CFTR mRNA must also be considered and 
finally 4) safety issues for the health care workers and patient contacts. Questions related to 
safety issues in each of these categories will be considered separately below. 
4.1 Routine Clinical Procedures Usually Carried Out in CF Patients: Use of standard 
clinical procedures such as phlebotomy and radiological studies including chest roentgenography, 
CT scanning, bronchoscopy and bronchoalveolar lavage are commonly carried as part of the 
standard care of individuals with cystic fibrosis. The safety of each of these procedures is 
addressed in section 5 of this protocol and in the informed consent and will be discussed with 
the patient in detail. Standard medical treatment of any complications related to those 
procedures will be fully available to the subject. 
4.2 Safety Considerations Regarding Location and Level of Expression of Normal CFTR 
Within the Lung: Since the CFTR expression appears to be influenced by both developmental 
and tissue specific influences, it is possible that unregulated or aberrantly regulated CFTR 
mRNA could have untoward physiological consequences. The lack of the CF phenotype of 
heterozygote patients who are carriers for CFTR mutations suggests that potential decrease in 
copy number of wild type CFTR is not associated with discernible disease and suggesting that 
modest decreases in CFTR gene expression (if copy number related) is not harmful. At the 
present time both in vitro and in, vzvo studies support the concept that aberrant expression of the 
CFTR mRNA is not associated with detectable toxicity, see below. 
CFTR mRNA has been both permanently and transiently transferred into a variety of normal 
and CF cells including CFPAC-1 human tracheal grafts (Engelhardt et.al., 1992) CFT-1 cells 
(Johnson et.al., 1992) and other cells (Tabcharani et.al., 1991; Drumm et.al., 1990) without 
signs of toxicity. Likewise, adenoviral mediated transfer of CFTR to the lung was not toxic in 
the cotton rat (Rosenfeld et.al., 1991, 1992). CFTR has been produced at high levels in the 
breast tissue of transgenic mice without observed toxicity and with concomitant production of 
readily detectable hCFTR protein in the milk (DeTullio et.al., 1992). In experiments from this 
laboratory, we have tested the toxicity of CFTR by directing its expression in the lung and other 
organs using a variety of promoter-enhancer elements obtained from surfactant protein-C (SP-C), 
CC 10 and /3-actin genes (Whitsett et.al., 1992a, b). The hCFTR mRNA were expressed at 
varying levels in several organs of these transgenic mice (Table I). Most of the transgenic 
mouse lines have been maintained for one to two years during which time we have not observed 
any evidence of developmental, morphological or physiological abnormalities in these animals. 
( In the SP-C hCFTR transgenic mice (J4) and others, the mRNA or CFTR protein were readily 
detected in the bronchiolar and alveolar cells (Figure 24) as well as in the testes of transgenic 
mice. Growth, development and reproduction has been entirely normal in these hCFTR bearing 
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