One century after the pioneering work of Calmette and of Phisalix and Bertrand, antivenoms are still prepared from plasma or serum of hyperimmunized animals, mostly horses. However, manufacturing processes have changed over the years and most current preparations are no longer crude serums but purified F(ab ) 2 antivenoms which are much better tolerated. In order to increase further the purity and safety of a F(ab ) 2 antivenom to European vipers, Ipser Europe, we have developed a new manufacturing process which is based on ion-exchange chromatography. The process includes one step for the selective extraction of equine IgG T antitoxins from other immunoglobulins G. This allows a doubling of the antivenomous specific activity. A final pasteurization is performed in order to increase viral safety. In size-exclusion HPLC analysis, F(ab ) 2 purity was over 90% and the main other component was Fab (about 5%). No high mol. wt aggregates were detected. Moreover, no in vitro anticomplementary activity was found, nor hypotensive effect during a flash i.v. administration in rats. A pharmacokinetics study after i.v. injection in the rabbit showed half-lives of 2.66 ± 0.74 hr (distribution) and 49.7 ± 4.1 hr (elimination). The distribution volume was 224 ± 28 ml/kg Vdβ. These values compare favourably with published values for smaller Fab fragments. An immunoneutralization study in the rabbit confirmed that pasteurized, ion-exchange chromatography purified equine IgG T F(ab ) 2 represent an excellent alternative to older antivenoms.
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