Rabbit snake-bite model to assess safety and efficacy of anti viper chicken antibodies (IgY)

摘要

Infusion of mammalian antivenom is considered to be the best available treatment for snake bites; but, production of cost-effective IgG in pure form is challenging. Purification of egg yolk immunoglobulins (IgY) raised against various toxins has been found to be relatively easier. But to use IgY for therapeutic purpose its efficacy and safety need to be experimentally proven which is hardly done due to lack of an appropriate model. In this study, pure IgY against viper venom was isolated and its efficacy and safety for intravenous infusion was tested in rabbits. Rabbit snake bite model was created by subcutaneous injection of 2x lethal dose50 (LD50) venom. Animals were given intravenous infusion of pure anti-viper IgY and recovery was monitored. Isolated chicken immunoglobulin (IgY) was >90% homogenous and showed 1:32 titre in immunodiffusion experiment. The minimum hemorrhagic dose (MHD) of viper venom was 0.2mg and antihaemorragic dose (AHD) of IgY was 4x concentration (0.8 mg) of native venom. Subcutaneously injected venom at LD50 resulted in severe local reaction, coagulation abnormality and mortality in rabbits. When anti viper IgY was infused within 2 h of envenomation, the animals survived, clotting parameters were reversed to normal and animals showed steady weight gain like healthy animals. No adverse effect of IgY was noticed on renal or hepatic function. The efficacy of commercially available mammalian IgG was lower than that of anti-viper IgY. Long term stability of the purified and lyophilized IgY was demonstrated. The effective IgY dose required to prevent mortality in the envenomed rabbits was found to be 4x of the injected venom estimated by Lowry's protein assay. It has been demonstrated that rabbit model of snake bite is successfully cured by anti-snake IgY infusion at a specific dose.