Long-term expression of functional cFIX after second administration of AAV2/8 or AAV2/5 vectors in AAV2-pretreated hemophilia B dogs. Hemophilia B dog D39 (•) was initially injected intraportally with AAV2 LSP-cFIX-W at a dose of 2.8 × 10¹² GC/kg, and 995 days after the first injection, the dog received a second intraportal injection with AAV2/8 LSP-cFIX-W vector at a dose of 5 × 10¹² GC/kg. Hemophilia B dog C52 (▵) received a first intraportal injection of AAV2 LSP-cFIX at a dose of 2.8 × 10¹¹ GC/kg; 1180 days after the first injection, the dog received a second intraportal injection with AAV2/5 LSP-cFIX-W vector at a dose of 2.3 × 10¹³ GC/kg. (A,D) WBCT; normal range is 8 to 12 minutes as indicated by the shaded area; before the first vector injection, WBCT for D39 was more than 60 minutes and for C52 it was 42 minutes. Open arrows indicate the spontaneous bleeding episodes that required plasma infusion. (B,E) aPTT; shaded area indicates the normal range, which is 24 to 32 seconds; before treatment, aPTTs for D39 and C52 were 97.8 seconds and 97.7 seconds, respectively. The reduction of aPTT after vector readministration in both dogs was significant (P ≤ .001, ANOVA). Open arrows indicate the spontaneous bleeding episodes that required plasma infusion. (C) Plasma cFIX antigen levels; dotted line indicates the therapeutic level, which is 250 ng/mL.