Inhibition by CaNa2EDTA of local tissue damage induced by Bothrops asper (terciopelo) venom:: Application in horse immunization for antivenom production

The ability of the chelating agent CaNa(2)EDTA to inhibit local tissue damage induced by Bothrops asper venom was studied in mice and in horses used for polyvalent (Crotalinae) antivenom production. CaNa(2)EDTA was devoid of toxicity when injected i.m. or s.c. inducing only a mild edema. Preincubation of B. asper venom with CaNa(2)EDTA inhibited hemorrhagic and dermonecrotic activities, but did not reduce edema-forming and myotoxic effects. A group of horses initially immunized with native venoms developed less severe local tissue reactions when injected with booster doses of venom and CaNa(2)EDTA than when receiving booster injections of venom alone, although they showed a similar antivenom response. Moreover. antivenoms produced from plasmas of horses that received booster injections of either venom alone or venom plus CaNa(2)EDTA had similar neutralizing activity against lethal, hemorrhagic and coagulant effects induced by B. asper venom. The similar antibody response was corroborated by Western blotting using crude venom and by an ELISA that estimates anti-myotoxin titer. It is concluded that the chelating agent CaNa(2)EDTA reduces the extent of local tissue damage induced by B. asper venom, without affecting the immune response of horses against pharmacologically-relevant venom components. (C) 1998 Elsevier Science Ltd. All rights reserved.