Iv 3i*Ui I tliik 
Another possibility is that the Ad5-CB-CFTR will undergo a recombination 
with homologous wild type Ad to form a more toxic structure. As demonstrated 
below the most likely recombination will be between the large stretch of homology 
3’ to the CFTR minigene. This will form two recombinants: one containing the 
CFTR minigene with E3 sequences (this exceeds the wild type genome size; our 
attempts to actually make this virus have failed because it cannot be packaged) and 
a wild-type hybrid genome missing E3 sequences (there is no theoretical reason to 
expect this to be more pathogenic than either parent). 
E3 deletion 
Figure 26. Possible forms of recombination between Ad5-CB-CFTR and wild 
type adenovirus. 
The next consideration relates to the probability that the Ad5-CB-CFTR 
virus can replicate, spread and be transmitted. We believe that this will be unlikely 
based on our animal data. In order to assure that this does not occur we will keep 
the patients in isolation for a period of at least 10 days following the treatment. The 
patient’s nasal swabs and sputum will be evaluated for Ad5-CB-CFTR sequences 
before discharge. If there is evidence of ongoing spread the patient will be asked to 
stay in the hospital for additional days. We think this will be extremely unlikely. 
The other possible situation that could lead to spread is if the patient becomes 
superinfected with a homologous wild type virus which mobilizes the recombinant 
genome. It is impossible for this to occur through the generation of a replication 
competent virus containing the minigene due to size limitations of packaging. The 
spread of the genome would have to occur by adenoviral functions provided in trans. 
We think this is highly unlikely and should not prevent the study. In order to 
address this potential concern we will work to be particularly cognizant of signs and 
symptoms characteristic of adenoviral infections and will continue to survey nasal 
swabs for Ad5-CB-CFTR sequences using the PCR assay. 
Recombinant DNA Research, Volume 17 
[508] 
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