Detection of proviral genome in secondary colonies derived from engrafted NOD/SCID mice. Secondary colonies were established with cells obtained from the BM of engrafted NOD/SCID animals 6 weeks after injection. The presence of LNSN proviral DNA in hematopoietic colonies derived from three mice injected with CB#1 (A), one mouse injected with CB#3 (B), and one mouse injected with CB#5 (C) was assessed by a sensitive LNGFR-specific PCR. The 425-bp–specific LNGFR product was detected by Southern blotting. Amplification of a sequence from the human mannose binding protein (MBP) gene was used to control for the presence of DNA.63