Comparison of human heavy- and light-chain antigen expression in vivo. Hem-A/Rag1 mice were injected with 3 × 10¹¹ vg/mouse of both AAV-hFVIII-HC and AAV-hFVIII-LC (A), AAV-hFVIII-LC (B), and AAV-hFVIII-HC (C). Mice were bled periodically, plasma was harvested, and FVIII heavy-chain (▪) and light-chain (♦) antigen levels were measured by chain-specific ELISAs. Error bars indicate standard deviation.