[Glycosylation and L303e/F309S mutations improve intein-mediated splicing of the split coagulation factor VIII]

We recently demonstrated that an intein-mediated protein splicing can be used to transfer B-domain-deleted FVIII (BDD-FVIII) gene by a dual-vector. In this study, we observed the effect of a variant heavy chain with six potential glycosylation sites of B domain and L303E/F309S mutations in its A1 domain, which were proven to be beneficial for FVIII secretion, on secretion of spliced BDD-FVIII. By transient co-transfection of cultured 293 cells with intein-fused variant heavy chain (DMN6HCIntN) and light chain (IntCLC) genes, the culture supernatant was analyzed quantitatively by ELISA for secreted spliced BDD-FVIII antigen and by a chromogenic assay for bioactivity. The data showed that the amount of spliced BDD-FVIII protein and coagulation activity in culture supernatant from DMN6HCIntN plus IntCLC co-transfected cells were up to (149 +/- 23) ng x mL(-1) and (1.12 +/- 0.14) u x mL(-1) respectively greater than that of intein-fused wild type heavy (HCIntN) and light chain (IntCLC) co-transfected cells [(99 +/- 14) ng x mL(-1) and (0.77 +/- 0.13) u x mL(-1)] indicating that the variant heavy chain is able to improve the secretion of spliced BDD-FVIII and activity. A cellular mechanism-independent BDD-FVIII splicing was also observed. It provided evidence for ongoing animal experiment using intein-mediated dual-AAV vector technology for delivery of the BDD-FVIII genes.