Production of factor VIII deficient plasma by immunodepletion using three monoclonal antibodies.

Factor VIII deficient plasma was made from pooled, HIV antibody and hepatitis B antigen screened, normal human plasma by cryoprecipitation and immuno-depletion, using three different monoclonal antibodies bound to Sepharose columns, in series. These monoclonal antibodies are specific respectively for von Willebrand factor, factor VIII heavy chain and factor VIII light chain. The immunodepleted plasma contained less than 0.002 u/ml factor VIII coagulation activity (VIII:C) less than 0.0001 u/ml von Willebrand factor antigen and 1-2 g/l fibrinogen, while the levels of other clotting factors were unchanged. This immunodepleted plasma was compared with commercial factor VIII deficient plasma obtained from a severe haemophilia A patient as substrate in the one-stage factor VIII assay. Plasmas obtained from 20 normal subjects and 28 patients with von Willebrand's disease or haemophilia A were assayed for VIII:C using the two substrates. The results were very highly correlated (r = 0.96). The columns have high capacity and can be regenerated at least 10 times. Large-scale production of a substrate for factor VIII assays free of virus contamination is now feasible.