In vivo persistence of transduced cells as detected by PCR. Mononuclear cells from rhesus peripheral blood were obtained at indicated time points. DNA was extracted and subjected to semi-quantitative PCR spanning the polylinkers (see Fig 1). The longer PCR products are derived from the retroviral vector and the shorter ones are derived from the AAV vectors. The copy number control was made from log dilution of the G1PLII-retroviral producer clone into the control rhesus lymphocyte DNA.