Materials arid Methods 
Animals and Cell lines 
The animals used in these studies were cyncmolgus macaque monkeys obtained 
from Hazel ton Research Animals. NIH 3T3 cells were kindly provided by Dr. 
Sandra Ruscetti, and the PG-4 cell line (used as a helper virus indicator for 
S+L - assays) by Dr. Robert Bass in. 
Vector Construction 
The construction of the retroviral vector SAX (Figure 1) and the 
generation of the virus producer cell line S3A have been described previously 
(13) . Briefly, SAX was made by inserting a SV40-prcmoted human ADA cDNA into 
the previously described (5,6,16) parental vector, N2. A fusion gene was 
created between the SV40 promoter end the ADA structural gene by placing the 
400 bp Kpn I-Hind III fragment containing the enhancer and promoter elements of 
the SV40 early region irrmediately upstream of a 1300 bp sequence containing the 
full-length ADA cDNA (10) (Eco RI-Acc 1 fragment of clone ADA 211) . 
Bone Marrow Processing end Transplantation 
Marrow (approximately 40-60 ml) was harvested from the long bones of the 
animal prior to irradiation. Mononuclear cells were isolated by 3% gelatin 
sedimentation end Ficoll/Hypaque gradient separation. These cells were then 
incubated with vector producing cells or vector-containing supernatants at 37 
in the presence of 8 ug/ml polybrene (Aldrich) as described in the text. The 
cyncmolgus primates received a dose of 1000 rads total body irradiation ( 60 Co 
at 10 rads/min.) immediately followed by infusion of their autologous bone 
marrow infected with the SAX vector. This dose of irradiation produces 
permanent aplasia in unreconstituted animals in this primate model. 
Hematopoietic Cell Culture 
The CFU-C assay for nyeloid progenitors has been described (17,18). The 
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