Intein-Fused Lucine Zippers Increase Plasma Coagulation Activity by Improving Protein Trans-Splicing in Dual-Vector Factor VIII Gene Delivered Mice

We previously demonstrated that leucine zippers fused to intein could increase secretion of spliced B-domain-deleted coagulation factor VIII (BDD-F VIII) protein and activity by dual-vector based BDD-F VIII gene transfected cell in vitro through improving protein trans-splicing. In this study, a pair of plasmid vectors expressing human BDD-F VIII heavy and light chain fused with lucine zipper and split Ssp DnaB intein was co-injected into C57BL/6 mice via the portal vein. Fourty-eight hours post-injection, the level of heavy chain and F VIII coagulation activity in collected plasma were determined and shown as (298 +/- 67) mu g/L and (1.15 +/- 0.29) U/ml respectively, greater than that of control mice injected with both vectors without leucine zippers ((179 +/- 59) mu g/L and (0.58 +/- 0.19) U/ml). It demonstrated that leucine zippers fused intein could increase F VIII coagulation activity in plasma of mice with intein-based dual-vector BDD-F VIII gene delivery through improved protein trans-splicing. It provided evidence for ongoing hemophilia A gene therapy using dual-AAV vecors.