Abstract
Properties of factor VIII (FVIII) in recombinant FVIII concentrates (rFVIII, BAY w 6240) were investigated using 6 kinds of monoclonal antibodies to FVIII.
The FVIII: C levels obtained by the one-stage method using severe hemophilia A plasma as a substrate were identical with those indicated on the label (100u/ml). The FVIII: C levels obtained by the chromogenic method were relatively higher than those by the one-stage method.
The FVIII: Ag levels assayed by polyclonal ELISA agreed with those by NMC-VIII/1 (recognizes the 80KDa fragment of L-chain) or NMC-VIII/5 (the 70KDa of L-chain) monoclonal ELISA, whereas the FVIII: Ag levels by C 5 (the 54KDa of H-chain) monoclonal ELISA were 2.5-3.0 times higher than those by other monoclonal ELISAs. The ratio between FVIII: Ag and FVIII: C was 1.4. It was considered that FVIII in the recombinant concentrates lost its activity less than FVIII in the heat-treated concentrates commercially available.
No von Willebrand factor was detectable by the sandwich ELISA system. SDS-PAGE pattern showed almost no contamination except albumin as a stabilizer.
Immunoblot analysis revealed that FVIII in recombinant concentrates could react not only with monoclonal antibodies to L-chain and H-chain, but also with monoclonal antibodies to middle portion of FVIII molecule.
These results suggest that the fundamental structure of FVIII molecule for coagulant activity is preserved in the rFVIII concentrates, and that it is expected to be useful for the treatment of hemophiliacs.
