Elucidation of N-linked oligosaccharide structures of recombinant human factor VIII using fluorophore-assisted carbohydrate electrophoresis.

Abstract

Characterization of the carbohydrate moiety is a critical measure of manufacturing process consistency of recombinant human Factor VIII (rFVIII) in Chinese-hamster ovary (CHO) cells. FVIII, a large (300 kDa) glycoprotein, is employed therapeutically for the correction of haemophilia A. While N-linked and O-linked oligosaccharides are found in this protein, the current study focuses on the N-linked oligosaccharides. The N-linked oligosaccharides from rFVIII were released using either peptide N-glycosidase F or endoglycosidase H, derivatized with the fluorophore 8-aminonaphthalene-1,3,6-trisulphonate, and analysed by fluorophore-assisted carbohydrate electrophoresis (FACE). The electrophoretically resolved oligosaccharide bands were isolated and individual bands subjected to digestion with defined pools of exoglycosidases and re-electrophoresed on FACE sequencing gels. The resulting gel patterns were interpreted, based on band mobility shifts, to obtain the sequence structure of the oligosaccharides. A total of eight acidic and 12 neutral structures were identified, and the majority of the oligosaccharides (approximately 92%) were found to be sialylated. All of the major oligosaccharide structures found in CHO-cell-derived rFVIII have also been reported to be present in plasma-derived FVIII. Among the most abundant are disialylated, biantennary, core-fucosylated (approximately 40%), followed by trisialylated, triantennary, core-fucosylated and monosialo, biantennary, core-fucosylated structures (each approximately 18%). The Gal alpha 1-3Gal structures reported to be present in baby-hamster-kidney-cell-derived rFVIII were not found in the CHO-cell-derived protein. The glycosylation patterns were consistent in six random lots of rFVIII [coefficient of variation (%) 3-14] based on percentage lane luminance data of bands that represent approximately 98% of all asparagine-linked oligosaccharides.