Vector persistence in hemophilia B dogs after liver-directed gene therapy. Hepatic biopsies, DNA isolation, FIX PCR, and microcapillary electrophoresis were as described. The fragment at 174 bp is the endogenous mutant FIX amplicon, and the fragment at 179 bp is the AAV vector-derived normal canine FIX amplicon. The relative percentage of each fragment is indicated (%) to the right of each peak. Amplification of DNA from peripheral blood and sperm DNA generated only the 174-bp fragment (not shown).