[Genetic origin of venom variability: impact on the preparation of antivenin serums]

One of the main possible origin of the biochemical variations of venoms could be genetic. We studied the venom of members of litters born in a snake farm (12 Crotalus atrox and 21 Naja haje). We first used the electrophoresis in cellulose acetate (AE). Then, variations were confirmed by immunoelectrophoresis (AIE) using an antivenom (IPSER Africa, Pasteur Mérieux Sérums & Vaccines) and immunsera prepared on rabbit from i) venom presenting the maximum of bands in electrophoresis (complete venom) and ii) pure toxins (neurotoxin-alpha and cardiotoxin-gamma). At last, the toxicity of some samples was measured and the ability of SAV to neutralise the corresponding sample was measured. The AE of C. atrox venoms showed a good homogeneity, probably due to a good genetic stability of the investigated group. On the other hand, N. haje venoms have revealed a great heterogeneity. The 13 samples were allocated to five groups according to the absence of some fractions compared to the complete venom. The AIE showed that the neurotoxin-alpha is present in every sample, but variable in quantity, even when it did not appear on AE. We suggest that these pattern variations are due either to relative variations of protein fractions in samples or to modifications of the chemical composition of the neurotoxin-alpha. However, the variation of toxicity between the different samples questioned the neutralisation ability of antivenoms. We propose that venom sample choice for SAV production should be based on biochemical criteria and toxicity of samples rather than random pooling.