| Summary: | The Equatorial Spitting Cobra (<i>Naja sumatrana</i>) is a medically important venomous snake species in Southeast Asia. Its wide geographical distribution implies potential intra-specific venom variation, while there is no species-specific antivenom available to treat its envenoming. Applying a protein-decomplexing proteomic approach, the study showed that three-finger toxins (3FTX), followed by phospholipases A<sub>2</sub> (PLA<sub>2</sub>), were the major proteins well-conserved across <i>N. sumatrana</i> venoms of different locales. Variations were noted in the subtypes and relative abundances of venom proteins. Of note, alpha-neurotoxins (belonging to 3FTX) are the least in the Penang specimen (Ns-PG, 5.41% of total venom proteins), compared with geographical specimens from Negeri Sembilan (Ns-NS, 14.84%), southern Thailand (Ns-TH, 16.05%) and Sumatra (Ns-SU, 10.81%). The alpha-neurotoxin abundance, in general, correlates with the venom’s lethal potency. The Thai <i>Naja kaouthia</i> Monovalent Antivenom (NkMAV) was found to be immunoreactive toward the <i>N. sumatrana</i> venoms and is capable of cross-neutralizing <i>N. sumatrana</i> venom lethality to varying degrees (potency = 0.49–0.92 mg/mL, interpreted as the amount of venom completely neutralized per milliliter of antivenom). The potency was lowest against NS-SU venom, implying variable antigenicity of its lethal alpha-neurotoxins. Together, the findings suggest the para-specific and geographical utility of NkMAV as treatment for <i>N. sumatrana</i> envenoming in Southeast Asia.
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