Physical, chemical and immunological studies on bovine factor VIII

Highly purified bovine factor VII prepared according to our technique and having a specific activity of 500 U/mg protein has been studied. The chemical analysis of the preparation revealed it to be composed of amino acids, lipids (8-10%) and carbohydrates (7%). The lipid moiety can be removed by chromatography. Different mechanism of inactivation of bovine factor VII and the possible molecular changes induced by the inactivating agents were studied. EDTA and EGTA provoke a weakening of the bonds linking the structural elements of the molecule, which allows for the separation of two different components of the molecule by gel filtration. Upon treatment with thrombin, the carbohydrate content of bovine factor VIII decreases without any apparent degradation of the protein moiety of the molecule. The fact that precipitating and neutralizing antisera against factor VIII were obtained, shows that the molecules modified by EDTA and thrombin still have the antigenic properties of factor VIII. The inhibitor developed by hemophiliacs transfused with human factor VIII is bound to bovine factor VIII, forming a complex reveal that it is composed of bovine factor VIII and human gamma-globulin. Bovine factor VIII in the complex retains some antigenic determinants which bind rabbit antiserum against bovine factor VIII, as shown by neutralization of the antiserum and by precipitation studies.