STRONG CROSS-REACTION OF HUMAN ANTI-APROTININ ANTIBODIES FROM HEART-TRANSPLANT PATIENT WITH [ARG(15)]APROTININ

We detected anti-aprotinin antibodies by an enzyme immunoassay in seru m of a 33 year old man who showed anaphylactic reactions during heart transplantation under aprotinin reexposition. The antibodies were isol ated by affinity chromatography by aprotinin immobilized on CNBr activ ated Sepharose. The crossreactivity was tested by a competitive enzyme immunoassay (50% inhibition) against different aprotinin homologues a nd two human Kunitz-type protease inhibitors, bikunin and TFPI. In com parison with native aprotinin (immunoreactivity = 100%) the crossreact ion of the homologue [Arg(15)]aprotinin was 76%, of [Val(15)]aprotinin 15% and of isoaprotinin 1, [Ala(14,38)]aprotinin and [seco15/16]aprot inin less than 10%. An immunoreactivity with bikunin and TFPI was not detected, Similar results were obtained with polyclonal anti-aprotinin antibodies from rabbit. Our results show that human anti-aprotinin an tibodies are mainly directed against the reactive site of aprotinin, F rom this we conclude that the reactive site exposes the major epitope resulting in a major target site for antibodies in a species independe nt way, and therefore, it is obvious that the recombinant aprotinin ho mologue [Arg(15)]aprotinin, which is scheduled for therapy in open-hea rt surgery, will have similar immunogenic effects as native aprotinin.