Retroviral vector and expression levels in normal mice from different strains after neonatal transduction. (A) hAAT-hFIX-WPRE. The RV contains intact LTRs at the 5′ and 3′ ends, an extended packaging signal (ψ+), the 403-nt human α1-antitrypsin promoter (hAAT), the 1.5-kb hFIX cDNA (hFIX), and the 591-nt woodchuck hepatitis virus posttranscriptional regulatory element (WPRE). Transcription can initiate from the LTR or hAAT promoters, as indicated by the arrows. (B) Expression in normal mice from different strains after neonatal transduction. C3H (N = 5), BALB/c:129S (N = 5), BALB/c (N = 7), or C57BL/6 (N = 3) mice were injected with 1 × 1010 TU/kg at 2 or 3 days after birth. Average hFIX antigen levels ± SEM are shown at the indicated time in months after birth.
