Toxicity and cross-neutralization of snake venoms from two lesser-known arboreal pit vipers in Southeast Asia: Trimeresurus wiroti and Trimeresurus puniceus.

The lesser-known Sundaic lance-headed pit vipers Trimeresurus wiroti (Malaysia) and Trimeresurus puniceus (Indonesia) contribute to the disease burden of snakebite envenomation in Southeast Asia, but their venom toxicity and neutralization remain insufficiently investigated. This study demonstrated that both venoms were procoagulant (involving thrombin-like activity), hemorrhagic, and lethal to mice, with T. wiroti venom being more lethal (LD = 0.78 μg/g c.f. 1.21 μg/g). The hetero-specific antivenom from Thailand, Green Pit Viper Antivenom (GPVAV, raised against Trimeresurus albolabris) cross-reacted with T. wiroti and T. puniceus venoms with a higher efficacy of immunological binding activity for the latter. The antivenom was also effective in cross-neutralizing the procoagulant, hemorrhagic and lethal effects of the venoms. In lethality neutralization, GPVAV showed a potency of 0.79-1.05 mg venom per mL antivenom, corresponding to the complete neutralization of approximately 8-10 mg venom per unit vial of antivenom for T. wiroti and T. puniceus venoms. Taken together, it was inferred that T. wiroti, T. puniceus, and T. albolabris venoms share common toxin epitopes, thus enabling the cross-neutralization observed. These findings suggest that GPVAV may be potentially useful in the management of envenomation by T. wiroti and T. puniceus while awaiting clinical trial and validation.