von Willebrand factor contaminating porcine factor VIII concentrate (Hyate:C) causes platelet aggregation

Severe thrombocytopenia has been reported to occur in some patients treated with a polyelectrolyte-fractionated porcine factor VIII concentrate (Hyate:C) (Kernoff et al, 1984; Gatti & Mannucci, 1984). We report here that Hyate:C induces aggregation of platelet-rich plasma in vitro accompanied by ATP release and thromboxane B2 formation, and is inhibited by EDTA and prostaglandin E1. Hyate:C induced platelet aggregation is affected by monoclonal antibodies anti-glycoprotein Ib or anti-glycoprotein IIb/IIIa and suppressed by polyclonal anti-porcine von Willebrand factor antiserum. We conclude that the aggregating ability of Hyate:C is due to porcine von Willebrand factor present in the concentrate. The occasional thrombocytopenia described after Hyate:C infusions probably results from the interaction between platelets and the porcine von Willebrand factor contaminating the concentrate.