Outcome of gene transfer with ss or scAAV1 in HB mice. HB mice were injected i.m. with 1011 vg of ss or scAAV1-CMV-hF.IX (n = 4/group). Plasma was collected 1, 2, and 4 weeks post-injection. (A) Circulating hF.IX levels were measured by ELISA. (B) Anti-hF.IX IgG1 levels in plasma were measured by ELISA. (C) Bethesda titer. One BU represents the inhibition of 50% of clotting activity. (D-E) Splenocytes were harvested and restimulated with media alone, the CD8 epitope of hF.IX, or SEB, and IFN-γ spot-forming units (per 106 cells) were measured by ELISPOT. Measurements were performed on individual animals two weeks (D) or four weeks (E) post-injection. Data points are averages ± SEM. Results are representative of at least two independent experiments. * P < 0.05, ** P < 0.01, *** P < 0.001, ns = not significant.