Cytotoxicity of Venoms and Cytotoxins from Asiatic Cobras (, , ) and Neutralization by Antivenoms from Thailand, Vietnam, and Taiwan.

Envenoming by cobras ( spp.) often results in extensive local tissue necrosis when optimal treatment with antivenom is not available. This study investigated the cytotoxicity of venoms and purified cytotoxins from the Monocled Cobra (), Taiwan Cobra (), and Equatorial Spitting Cobra () in a mouse fibroblast cell line, followed by neutralization of the cytotoxicity by three regional antivenoms: the Thai monovalent antivenom (NkMAV), Vietnamese snake antivenom (SAV) and Taiwanese Neuro bivalent antivenom (NBAV). The cytotoxins of (NA-CTX) and (NS-CTX) were identified as P-type cytotoxins, whereas that of (NK-CTX) is S-type. All venoms and purified cytotoxins demonstrated varying concentration-dependent cytotoxicity in the following trend: highest for , followed by and . The antivenoms moderately neutralized the cytotoxicity of venom but were weak against and venom cytotoxicity. The neutralization potencies of the antivenoms against the cytotoxins were varied and generally low across NA-CTX, NS-CTX, and NK-CTX, possibly attributed to limited antigenicity of CTXs and/or different formulation of antivenom products. The study underscores the need for antivenom improvement and/or new therapies in treating local tissue toxicity caused by cobra envenomings.