Recombinant DNA Advisory Committee - 03/1-2/93 
30 minutes results in diffuse gene transfer, i.e., approximately 20% of the cells were 
transduced. This data suggests that higher concentrations of vector will probably have to 
be achieved in order to realize a therapeutic effect. 
Assuming that very high concentrations of vector will be required, what are the safety 
considerations? Three days following intratracheal administration of 1 x 10 11 pfu, no 
cellular response is observed in the submucosal area. However, there was a mild 
mononuclear infiltrate that was observed on day 7 which diminished by day 14. 
Dr. Boucher explained the baboon model. The nasal mucosa of these animals was 
slowly perfused, particularly the inferior turbinate. Excess material drains anteriorly; 
therefore, the material is not swallowed and the possibility of ectopic expression is 
minimized. Dose-response studies in the baboon indicate that concentrations in excess 
of 1 x 10 11 pfu per ml will be required to obtain efficient transduction. 
Dr. Haselkom asked Dr. Boucher to address the issue of submucosal resistance in the 
mouse. Dr. Boucher explained that although these tissues are resistant to wild-type 
adenovirus infection, there are receptors that are expressed in the nasal epithelium. The 
issue of gene transfer may not be dependent on the virus going through an entire life- 
cycle. Dr. Boucher introduced Dr. Wilson to provide additional information about the 
primate model. 
Presentation~Dr. Wilson 
Dr. Wilson explained that the investigators have established the primate model to 
determine toxicity. A total of 12 baboons, 3 animals per group, received between 1 x 10 7 
and 1 x 10 10 pfu per ml into their lung on the contralateral side. At a concentration of 1 
x 10 10 pfu per ml, 90% of the distal airway and alveolar cells were transduced. The cells 
of the proximal airway demonstrated sporadic gene transduction. A clear dose-response 
was observed. The gross necropsies were normal at all doses except at 1 x 10 10 pfu per 
ml. On day 21, this concentration of vector demonstrated hemorrhagic reaction in 
localized segments of the lung. Other than the development of this infiltrate at day 21 
and a slight fluctuation in their blood gases, the animals were clinically normal. These 
baboons have also been analyzed for the recovery of virus by BAL and nasal swabs. No 
virus was recovered from any of these animals. 
Dr. Wilson commented on the status of the safety testing of the proposed vector. At the 
December 1992 RAC meeting, Dr. Ginsberg suggested that indicator cells are the 
method of choice for detecting replication-competent virus. However, the problem with 
indicator cells is that HeLa cells cannot tolerate a high MOI due to cytopathic effects. 
The maximum tolerated dose on HeLa cells was 100 pfu per plate. Dr. Ginsberg 
suggested using A549 cells. Dr. Wilson said that the investigators anticipated testing a 
Recombinant DNA Research, Volume 17 
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