practical solution for long term use. However, an Infant with the diagnosis of 
ADA deficiency established by prenatal testing and delivered by C-sectlon 
directly into a sterile environment would be the ideal candidate patient for 
gene therapy. In this case the patient would be kept in a pathogen-free 
environment until reconstitution following gene insertion had occurred. 
B. Research design, anticipated risks and benefits 
1. Structure and characteristics of the biological system 
Provide a full description of the nethods and reagents to be enployed 
for gene delivery and the rationale for their use. The following are 
specific points to be addressed: 
a. What Is the structure of the cloned DNA that will be used? 
(1) Describe the gene (genomic or cDNA). the bacterial plasmid or 
phage vector, and the delivery vector (if any). Provide complete 
nucleotide sequence analysis or a detailed restriction enzyme 
map of the total construct. 
The SAX retroviral vector used was produced by modifying the 
N2 parent vector. The development of N2 was described in Armentano. et al.. 
V i rol . in press (copy supplied in Appendix B). and was originally derived from 
Moloney murine leukemia virus (Mo-MuLV). A schematic comparison of Mo-MuLV. 
N2 and SAX is in Appendix A, Figure 1. The N2 vector, in a backbone of plasmid 
pBR322. was constructed by removing most of the sequences coding for the viral 
gag , pol . and erw proteins while leaving the 5' -long terminal repeat (LTR) 
sequences, the packaging signal, a small portion of viral gag sequence and the 
3* -LTR sequences intact. The 5 '-LTR fragment, including the packaging signal, 
from Mo-MuLV was generated by Bgll and Xhol digests followed by a limited 
exonuclease digestion with Bal31 and the addition of EcoRl linkers. The 3 '-LTR 
from Mo-MuLV was obtained by digestion with BamHI and PstI, limited Bal31 
digestion and addition of EcoRl linkers followed by digestion with Clal. The 
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Recombinant DNA Research, Volume 12 
