Effect of virucidal heat treatment on proteins in human factor VIII concentrates.

Intermediate-purity and fibrinogen-poor factor VIII concentrates were heated in the lyophilized state at 60 degrees C for up to 72 hours to inactivate blood-borne viruses. The effect of heat treatment on factor VIII, von Willebrand factor (vWf), and other proteins present in the concentrates (albumin, fibrinogen, fibronectin, IgG, and IgM) was evaluated. Heat-induced protein aggregation, particularly of fibrinogen and fibronectin, occurred within 48 hours in the intermediate-purity concentrates and correlated well with decreased solubility of these products. Heated fibrinogen-poor concentrates were readily soluble and did not show protein aggregation even after 72 hours at 60 degrees C. Neither concentrate developed detectable neoantigens when tested against antisera to whole human plasma and to heated and unheated concentrates. Aggregation of the vWf molecule, detected by altered mobility in crossed immunoelectrophoresis and multimeric analysis in SDS agarose gels, occurred in heated intermediate-purity concentrates but not in fibrinogen-poor concentrates. Thus, higher-purity factor VIII concentrates withstand heat treatment better than concentrates that contain greater levels of contaminating proteins, particularly fibrinogen.