Enhanced HC secretion from HCHL mutein in vivo. CD4KOHA mice were injected with 4 × 1011 vg/mouse AAV8-HCHL vector (n = 4, open square), 4 × 1011 vg/mouse AAV8-HC745 vector (n = 4, close diamond), or 1 × 1011 vg/mouse AAV8-HCHL vector (n = 4, open square). The expression of FVIII heavy chain (y-axis) in mouse plasma was measured by FVIII heavy-chain-specific ELISA biweekly (x-axis). Error bars indicate standard error. ELISA, enzyme-linked immunosorbent assay; FVIII, factor VIII; HC, heavy chain.