FIG. 4.
In vivo half-lives of intravenously injected canine- and human-PCL-produced retroviral vectors in chimpanzees. Equal titers (∼5 × 109 BCFU) of DA- or HA-produced β-Gal vector were injected intravenously into chimpanzees, two animals per group. Animals A and B received canine PCL (DA) vector, and animals C and D received human PCL (HA) vector. At the times indicated, blood was drawn, and sera were prepared and frozen. The biological titer in serum samples was determined by a standard BCFU assay on tissue culture HT1080 cells. Chimpanzees A and B had very low or undetectable titers (shown here as 10 BCFU/ml).