Relationships between factor VIII:Ag and factor VIII in recombinant and plasma-derived factor VIII concentrates.
A variety of plasma-derived (pd) and recombinant (r) factor VIII (FVIII) concentrates are used to prevent and treat bleeding in severe hemophilia A patients. A significant side effect of FVIII replacement is the development of FVIII neutralizing antibodies (inhibitors) in up to 30% of patients receiving FVIII concentrates. The FVIII protein content (FVIII:Ag) per unit of FVIII:C in FVIII concentrates, and how effectively the FVIII:Ag in FVIII concentrates binds to von Willebrand factor (VWF) may provide information relevant for the survival of FVIII:C in vivo and for estimating the risk for inhibitor development. The FVIII:Ag content of nine r-FVIII and nine pd-FVIII concentrates were quantified in this study using two enzyme-linked immunosorbent assay (ELISA) platforms. The two ELISA platforms were based on the use of a monoclonal anti-(FVIII light chain)-IgG and polyclonal anti-FVIII antibodies as capture antibodies and both ELISAs were equally able to detect > or =0.005 IU of FVIII:Ag. Measured in international units, the r-FVIII concentrates contained significantly higher FVIII:Ag per unit of FVIII:C than the pd-FVIII concentrates. The VWF-binding profiles of the r-FVIII and pd-FVIII concentrates were also determined by gel filtration chromatography. Unlike the plasma-derived products, the r-FVIII concentrates invariably contained a fraction of FVIII:Ag molecules (approximately 20%) which was unable to associate with VWF. Given that VWF regulates both factor VIII proteolysis and survival of FVIII:Ag in vivo, the fraction of FVIII:Ag unable to bind to VWF may have a reduced survival and be more susceptible to proteolytic degradation in vivo. The extent to which the fractions of FVIII:Ag in concentrates able and unable to bind to VWF contribute to inhibitor development in severe FVIII-deficient patients is unknown.
Lin
Y
Y
Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.
Yang
X
X
Chevrier
M-C
MC
Craven
S
S
Barrowcliffe
T W
TW
Lemieux
R
R
Ofosu
F A
FA
D015153:Blotting, Western; D004347:Drug Interactions; D004797:Enzyme-Linked Immunosorbent Assay; D005169:Factor VIII / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D006467:Hemophilia A / Q000097:blood* / Q000188:drug therapy; D006470:Hemorrhage / Q000517:prevention & control*; D006801:Humans; D010949:Plasma; D014841:von Willebrand Factor / Q000032:analysis / Q000378:metabolism*
D014841:von Willebrand Factor; C078147:F8 protein, human; D005169:Factor VIII