Detection of cFVIII in the plasma of AAV-cFVIII-104–injected dogs. Canine FVIII (1 and 4 ng as measured by ELISA) was immunoprecipitated from media collected from HepG2 cells that were transduced with AAV-cFVIII-104. Media collected from uninfected cells served as a negative control. The media was spiked with 500 μL FVIII-deficient dog plasma prior to immunoprecipitation. Canine FVIII was immunoprecipitated from the plasma (500 μL) of 2 AAV-cFVIII-104–treated dogs, Elisa and Junior. Plasma from an untreated Hem A dog was used as a negative control. SC denotes the position of single-chain cFVIII.