CROSS-REACTIVITY TO PORCINE FACTOR-VIII OF FACTOR-VIII INHIBITORS IN PATIENTS WITH HEMOPHILIA IN AUSTRALIA AND NEW-ZEALAND

Background: Inhibitory antibodies which neutralise factor VIII develop in 10-20% of individuals with inherited haemophilia A and rarely as a utoantibodies in normal individuals to cause acquired haemophilia. The antibodies are directed against human factor VIII but cross-react to varying degrees with porcine factor VIII. Porcine factor VIII can be u sed for treatment in individuals with low cross-reactivity. Aims: To d etermine the cross-reactivity of factor VIII inhibitors between human factor VIII and porcine factor VIII, in a population of patients with inherited and acquired haemophilia A. Also, to determine whether patie nts with inherited haemophilia and inhibitors have a higher incidence of factor VIII gene inversion in intron 22. Methods: Samples and data sheets from 43 patients with inherited and ten with acquired haemophil ia were submitted from hospitals in Australia and New Zealand. Inhibit or levels to human and porcine factor WI were measured by the Bethesda method in 39 with inherited and nine with acquired haemophilia A. Res ults: Of 39 patients with inherited haemophilia A, cross-reactivity wa s 0% in 17 patients, 1-19% in six, 20-39% in II and 40-80% in five. In six of nine patients with acquired haemophilia cross-reactivity was l ess than or equal to 7%. In inherited severe haemophilia A, the freque ncy of the intron 22 inversion was not greater in 37 study patients th an in 28 patients without an inhibitor. Conclusions: Many patients in Australia and New Zealand with inhibitors to human factor VIII present ly show a low or absent level of cross-reactivity to porcine factor VI II. These may respond to treatment with this concentrate at least in t he short term. There remains a group of patients with high cross-react ivity who will respond only to recombinant factor Wa or prothrombin co mplex concentrates.