SIMILAR EFFECTIVENESS OF FAB AND F(AB')(2) ANTIVENOMS IN THE NEUTRALIZATION OF HEMORRHAGIC ACTIVITY OF VIPERA-BERUS SNAKE-VENOM IN MICE

The ability of two antivenoms to Vipera spp., consisting of Fab (Thera peutic Antibodies), or of F(ab')(2) (Zagreb Institute of Immunology) a ntibody fragments, to neutralize the hemorrhagic activity of Vipera be rus snake venom in mice, was compared. First, the neutralizing potency was determined by in vitro preincubation of venom and antivenom, foll owed by intradermal injection into mice and subsequent measurement of the hemorrhagic area. Both antivenoms had the same anti-hemorrhagic po tency, in terms of volume of antivenom/mass of venom, with an estimate d ED(50) (50% reduction of the effect) of 80 mu l antivenom/mg venom. Therefore, no adjustments in dose were necessary for subsequent in viv o comparative experiments. When the antivenoms were administered intra venously into mice immediately after intradermal venom injection, ther e was no difference in their effectiveness in reducing hemorrhagic les ions, at all doses tested. These results indicate that neutralization of local hemorrhagic activity of V. berus venom in vivo is not improve d by the use of the smaller Fab fragments, in comparison to F(ab')(2), when equivalent neutralizing units are injected. However, this does n ot exclude the possibility that other clinically relevant venom effect s may be neutralized with different efficiency by Fab or F(ab')(2) fra gments of antibodies. Copyright (C) 1996 Elsevier Science Ltd