Southern blot analysis corroborates polyclonality and VCN as determined by qPCR. (A) DNA was cut with EcoR1, which cuts once within the vector as shown. Mixtures of DNA from a K562 cell line containing a single copy of the SIV vector with DNA from untransduced K562 cells in the proportions shown provide an estimate of the sensitivity of the blot to detect clonal bands. (B) Estimation of vector copy number in PB and BM cells of animals CJ5B and RQ2617 by Southern blot analysis. DNA was cut with BglII, which cuts twice in the vector genome as indicated, liberating a near full-length proviral genome that was detected by the indicated probe. Mixtures of DNA from a K562 cell line containing a single copy of the SIV vector with DNA from untransduced K562 cells in the proportions shown provide an estimate of the VCN in the rhesus samples shown.