Region-specific neutralization of Indian cobra (Naja naja) venom by polyclonal antibody raised against the eastern regional venom: A comparative study of the venoms from three different geographical distributions.

Indian cobra (Naja naja) venoms from different geographical locations vary in their composition, biochemical, and pharmacological properties. Venom samples from eastern, western and southern India are compared in this study. The venom from eastern region was found to be the most lethal of the three regional venoms. Monovalent antivenom (NNEV-IgG) prepared against the eastern venom was found to cross-react with the other two regional venoms. NNEV-IgG at an Ag:Ab ratio of 1:25 completely neutralized the lethality of eastern venom. At this ratio, it did not neutralize the other two venoms, but the survival time of experimental mice was extended significantly. Commercially available polyvalent antivenom neutralized the lethality of western venom at an Ag:Ab ratio of 1:60 and increased the survival time of experimental mice injected with eastern and southern venoms marginally. Further, NNEV-IgG neutralized the tested pharmacological and enzymatic activities of all the three venom samples dose dependently, with neutralization potency varying with the geographic origin of the tested venoms. Thus, the present study demonstrates the diversity in the immunological properties of venom from different geographical regions and underscores the importance of developing region-specific antivenoms for therapeutic purpose.