Recombinant DNA Advisory Committee - 12/3-4/92 
respiratory route? Dr. Ginsberg responded that he was unaware of any instance where 
these experiments have been performed. 
Dr. Post asked for further information regarding long-term persistence of non-integrated 
adenovirus. Dr. Ginsberg stated that both Ela and Elb are required for adenovirus 
integration; therefore, Ela and Elb mutants will not transform cells because there is no 
integration. Dr. Ginsberg noted that persistent infection of cultured lymphoid cells has 
been demonstrated for up to 3Y2 years without any evidence of integration. 
Dr. Hirano asked if it is more advantageous or disadvantageous to retain the E3 segment 
of the vector. Dr. Ginsberg answered that the advantages of retaining this segment 
outweigh the disadvantages. Since there will be only a 5% increase in the size of the 
genome, only assembly will be facilitated. 
Dr. D. Miller asked if the packaging cells contain other viruses that could be transferred 
in addition to the vector. Dr. Ginsberg said that the cultures could possibly be 
contaminated with adeno-associated virus (AAV); however, testing will be performed to 
monitor for such contaminating agents. There are no naturally occurring contaminants. 
Review-Dr. Schaechter 
Dr. Schaechter said that he is reassured by the information provided by Dr. Ginsberg; 
specifically, that the ability of the adenovirus vector to replicate and recombine is very 
small. However, it would be useful for the RAC to discuss the outcome if the virus 
actually replicated. What would be the outcome if CFTR is overexpressed in the cells of 
any tissue? What are the conductance and permeability problems that would arise? In 
murine experiments, overexpression of the CFTR gene produces no untoward effects; 
however, this is not a homologous experiment. Overexpression of the protein is a highly 
regulated step that requires phosphorylation by a highly regulated mechanism. In theory, 
overproduction of CFTR should not produce a deleterious effect. 
Dr. Schaechter said that he had concerns regarding the efficacy of this protocol. What 
percent of the bronchial epithelial cells will have to be transduced in order to achieve a 
temporary therapeutic effect? Is lavage the best method for accomplishing this 
transduction? What about aerosols? The chances of this single administration treatment 
being effective does not seem to be overwhelming. How will data derived from this 
experiment provide assurance that future studies will result in a therapeutic modality? 
Review-Dr. Walters 
Dr. Walters complimented the investigators on a well designed protocol. However, he 
noted that there were still a few remaining concerns following his communications with 
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Recombinant DNA Research, Volume 16 
