Comparative study on the ability of IgG and F(ab ')(2) antivenoms to neutralize lethal and myotoxic effects induced by Micrurus nigrocinctus (coral snake) venom

comparative study was performed on the ability of IgG and F(ab')(2) antiven oms to neutralize lethal and myotoxic activities of Micrurus nigrocinctus v enom. Both antivenoms were adjusted to a similar neutralizing potency in ex periments where venom and antivenoms were preincubated prior to injection. No significant differences were observed between IgG and F(ab')(2) antiveno ms concerning neutralization of lethal effect in rescue experiments, i.e., when antivenom was administered intravenously after envenomation, However F (ab')(2) antivenom was more effective in prolonging the time of death when subneutralizing doses were administered immediately after venom injection. Both products partially reversed the binding of M. nigrocinctus alpha-neuro toxins to acetylcholine receptor in vitro. The IgG and F(ab')(2) antivenoms effectively neutralized venom-induced myotoxicity when administered intrav enously immediately after envenomation, although neutralization was poor if antivenom injections were delayed, Intramuscular injection of venom promot ed diffusion of antivenom antibodies throughout muscle tissue, and F(ab')(2 ) diffused to a higher extent than IgG molecules, Thus, despite the observa tion that F(ab')(2) antivenom was mon effective than IgG antivenom in prolo nging the time of death when subneutralizing doses were administered immedi ately after envenomation, no major differences were observed in antivenom n eutralization of lethal and myotoxic effects or in their capacity to revers e neurotoxin binding to the acetylcholine receptor.