Cross Reactivity of Natural Hirudin Compared to the Recombinant Hirudins with Sheep Anti Hirudin Antibody

Abstract 4321

Recombinant versions of hirudin such as lepirudin (Refludan®) and desirudin (Iprivask®) are currently used as parenteral anticoagulants for various indications. The recombinant hirudin preparations differ from the natural hirudin in lacking a sulfate group on tyrosine at the 63^rd position and a single amino acid substitution. It is hypothesized that these minor differences in the natural and recombinant versions of hirudins contribute to a differential immunogenic behavior. The purpose of this investigation was to compare the relative immunoreactivity of the three forms of hirudin to a sheep antin–hirudin antibody. Antibodies (anti-n-hirudin) were generated in sheep treated with natural hirudin isolated from the medicinal leech (Hirudo medicinalis ). SDS-PAGE immunoblot and Western transfer were conducted using the native hirudin and two recombinant hirudins against the sheep anti-n-hirudin IgG antibodies. Cross-reactivity was quantified by measuring total optical density of the bands using a UVP densitometric scanning system and chemiluminescence detection, by comparing the protein-antibody complex band density from the western blot showed a comparable behavior of the Desirudin and Lepirudin in contrast to the normal or native hirudin which exhibited a much higher band density (2-fold increase). Moreover, the native hirudin exhibited specific bands representing mono, di- and tetra-meric forms, whereas the two recombinant forms exhibited primarily monomeric and dimeric forms. Interestingly several other preclinical versions of recombinant hirudins exhibited fifferent immunoblotting patterns. Although, the structural differences and the molecular weight represent relatively minor variations in the natural and recombinant hirudins, these studies strongly suggest a differential behavior of natural and recombinant hirudins in terms of their cross-reactivity with anti-n-hirudin antibodies.