Recombinant DNA Advisory Committee - 12/3—4/92 
rescue this replication-incompetent vector and create replication-competent Type 5 
adenovirus containing the CFTR gene? Dr. Parkman explained that the investigators 
have responded to these concerns by including the criteria that only patients with serum 
antibodies to Type 5 adenovirus will be used for this study. The presence of serum 
antibodies eliminates concerns regarding transmission of the CFTR gene to the germ 
cells of the patient. Rescued Type 5 adenovirus would be neutralized and eliminated 
from the patient's circulation. For this reason, the requirement that patients should be 
beyond reproductive age or have evidence of sterility are probably excessive criteria. 
As an added safety procedure, patients will undergo pulmonary cell sampling in order to 
screen for the presence of Ela and Elb sequences. Patients who exhibit positive PCR to 
these sequences will be excluded from the study. In summary, only those individuals who 
have had pre-existing Type 5 adenovirus infections (as demonstrated by serum 
antibodies) and who have no evidence of persistent adenovirus elements (Ela or Elb) 
will be eligible for this protocol. 
The E3 sequences that are capable of suppressing the host immunological response have 
been removed from the proposed vector. Therefore, in the event that a replication- 
competent recombinant virus were formed, the recombinant virus would be less 
pathogenic to the patient than the wild-type virus. 
Dr. Parkman commended the investigators for their excellent responses to his 
preliminary reviews. He noted that he still has concerns regarding the possibility that a 
patient who has remaining transduced epithelial cells after 3 to 4 months may acquire a 
wild-type adenovirus infection that could cause the recombinant virus to be rescued. The 
question also remains about the bronchial levels in which the CFTR gene will be 
expressed. If the vector is instilled into the upper bronchi, how far down will the 
expression occur, i.e., first, second, or third order bronchioles? 
Review-Dr, Ginsberg 
Dr. Murray called on Dr. Harold Ginsberg, an expert on adenoviruses and ad hoc 
consultant to the RAC, to provide his review of Dr. Crystal's protocol, specifically the 
vector issues. 
Dr. Ginsberg explained that there are tremendous advantages to using adenovirus vectors 
that have the Ela and Elb regions deleted; except for a high multiplicity of infection 
(MOI), the virus is incapable of replication. Ela is critical for enhancing the 
transcription of other early genes. Adenoviruses, like all DNA viruses, have genes that 
are expressed early. These early genes are required for DNA replication and the 
production of infectious virus. If DNA replication does not occur, then neutralizing 
antibodies will not be made. Another unique feature of Ela is that this region contains 
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Recombinant DNA Research, Volume 16 
