Expression of Biologically Active Recombinant B-Domain-Deleted Human Factor VIII in Mammalian Cells.

Hemophilia A is an X-linked recessive bleeding disorder, widely prevalent throughout the world, for which, replacement therapy is a current treatment done by infusion of either human plasma derived FVIII or recombinant FVIII. In order to produce a recombinant form of biologically active human coagulation factor VIII, a mammalian expression system is necessary for proper post-translational modifications. In this regard, two types of mammalian cell lines, COS7 and CHO, were transfected with a recombinant plasmid, constructed by insertion of a NotI restriction fragment containing B-domain-deleted cDNA of hFVIII in pcDNA3 plasmid, downstream of CMV promoter. By performing one-stage clotting assay as well as ELISA test on the conditioned media collected from transfected cells, we confirmed transient and stable expression of rhFVIII in the transfected COS7 and CHO cells, respectively. The presence of rhFVIII mRNA was also demonstrated by performing RT-PCR on total cellular RNA, extracted from the stably transfected CHO cells. The highest amount of produced active rhFVIII in the stably transfected CHO cells was estimated to be around 0.1 U/ml of the cultured media. By applying southern blotting experiment on the digested as well as high molecular weight chromosomal DNA, prepared from the stably transfected CHO cells, we have demonstrated the presence of the rhFVIII expressing plasmid in the CHO cells. The recombinant plasmid as well as the stable FVIII expressing cell line developed in this study has provided useful bases for further molecular studies of various important factors influencing the expression efficiency of rhFVIII.