Recombinant DNA Advisory Committee - 03/1-2/93 
One major difference between this study and other protocols approved by the RAC is 
that this protocol is the first to utilize a BPV vector. In responding to a question from 
Dr. Miller regarding the infectivity of BPV, Dr. Podack stated that the 69% fragment of 
the BPV genome contained in the vector deletes the genes for proteins that are 
necessary to make an infectious particle. BPV virus is very difficult to grow in vitro , 
based on data reported in the literature over the past 15 to 20 years. The only way to 
obtain BPV is to extract the virus from a cow wart. Other reports have documented the 
absence of BPV sequences in slaughter house butchers who have repeatedly been 
exposed to bovine warts. In responding to the question about recombination of the 
vector with human papilloma viruses, Dr. Podack stated that based on extensive 
literature, no recombination of approximately 60 subtypes of human viruses has been 
reported. Papilloma viruses are very species-specific, a bovine virus will infect a cow, but 
not other animals. Responding to the question of transforming potential, Dr. Podack 
agreed that this risk is real. There are 3 potentially transforming genes, E5, E6 and E7, 
in these viruses. E5 has been shown to be transforming in both bovine and human 
species. 
Discussion 
In the present protocol, tumor cells are transfected with the BPV vector. Do these 
tumor cells become more aggressive? Dr. Podack stated that in SCLC cells, no 
morphology changes or changes in the rate of cell division have been observed. Dr. 
Miller asked whether the critical experiment has been performed in animals, i.e., have 
transfected and untransfected cells been injected into the Lewis lung carcinoma model. 
Dr. Podack answered that no differences in tumorigenicity have been observed in animal 
survival. According to literature, it is very difficult to demonstrate transformation in 
tissue culture with this vector. No transformed foci were observed in cells selected for 
G418 resistance. However, without selection, foci developed after long periods of time. 
The vector has not been conclusively demonstrated to be transforming. Dr. Nava Sarver 
of the National Institute of Allergy and Infectious Diseases, NIH, stated that she has 
shown that papilloma virus transformation can be demonstrated with the C127 cells both 
in vitro and in vivo in mice. 
Dr. Miller commented on a question raised by Dr. Carmen that a radiation dose of 
12,000 rads appears to be insufficient to kill all transfected cells. Dr. Miller was 
concerned that a new type of cancer might arise from the residual surviving cells. After 
reviewing Dr. Podack's data on cell survival following several doses of irradiation 
treatments, Drs. Smith and Miller agreed that 12,000 rads of irradiation does not kill all 
the tumor cells. Dr. Parkman stated that the radiation dose is already very high. 
Increasing the dose might compromise the transfected cells' ability to produce IL-2. A 
clonogenic assay would be a preferable method for determining tumor growth after 
radiation. Dr. Podack stated that he would conduct that assay if it is required for 
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