BIOLOGICAL SIGNIFICANCE: The Indian krait or blue krait, Bungarus caeruleus, is a highly venomous snake that contributes to the snakebite envenoming problem in South Asia. This is a less aggressive snake species but its accidental bite can cause rapid and severe neurotoxicity, in which the patient may succumb to paralysis, respiratory failure and death within a short frame of time. The proteomic analysis of its venom (sourced from Sri Lanka) unveils its content that well correlates to its envenoming pathophysiology, driven primarily by the abundant presynaptic and postsynaptic neurotoxins (β-bungarotoxins and κ-neurotoxins, respectively). The absence of cytotoxins in the venom proteome also correlates with the lack of local envenoming sign (pain, swelling), and explains why the bite may be insidious until later stage when paralysis sets in. The muscarinic toxin-like proteins in the venom may be the cause of severe abdominal pain that precedes paralysis in many cases, and justifies the need of closely monitoring this symptom in suspected cases. Venom samples from Sri Lanka, India and Pakistan exhibited no remarkable variation in protein profiling and reacted immunologically toward the VINS Indian Polyvalent Antivenom, though to a varying extent. The antivenom is effective in neutralizing the Sri Lankan and Indian venoms, confirming its clinical use in the countries. The antivenom efficacy against the Pakistani venom, however, may be further optimized by incorporating the Pakistani venom in the antivenom production.

CONCLUSIONS/SIGNIFICANCE: The newly developed polyvalent antivenom NPAV may find potential application in the treatment of elapid bites in Southeast Asia, especially Malaysia, a neighboring nation of Thailand. Nevertheless, the applicability of NPAV in the treatment of cobra and krait envenomations in Southeast Asian victims needs to be confirmed by clinical trials. The cross-neutralization results may contribute to the design of broad-spectrum polyvalent antivenom.

SIGNIFICANCE: A shotgun proteomic approach adopted in this study revealed the compositional details of the venom of common tiger snake from Australia, Notechis scutatus. The proteomic findings provided additional information on the relative abundances of toxins and the detection of proteins of minor expression unreported previously. The potent lethal effect of the venom was neutralized by bioCSL Sea Snake Antivenom, an anticipated finding due to the fact that the Sea Snake Antivenom is actually bivalent in nature, being raised against a mix of venoms of the beaked sea snake (Hydrophis schistosus) and N. scutatus. However, it is surprising to note that bioCSL Sea Snake Antivenom neutralized N. scutatus venom much more effectively compared to the targeted sea snake venom by a marked difference in potency of approximately 6-fold. This phenomenon may be explained by the main difference in the proteomes of the two venoms, where H. schistosus venom is dominated by short-neurotoxins in high abundance - this is a poorly immunogenic toxin group that has been increasingly recognized in the venoms of a few cobras. Further investigations should be directed toward strategies to improve the neutralization of short-neurotoxins, in line with the envisioned production of an effective pan-regional elapid antivenom.

BIOLOGICAL SIGNIFICANCE: Laticauda colubrina (yellow-lipped sea krait) is a widely distributed, semi-aquatic venomous snake species. The venom proteome at the level of protein family is unsophisticated and consistent with its restricted prey selection. Nonetheless, the subproteomic findings revealed geographical variability of the venom for this widely distributed species. In contrast to two previous reports, the results for the Balinese L. colubrina venom showed that LNTX Neurotoxin a and Neurotoxin b were co-existent while the PLA2 lethal subtype (PLA-II) was undetected by means of LCMS/MS and by in vivo assay. This is an observable trait of L. colubrina considered divergent from specimens previously studied for the Philippines and the Solomon Islands. The stark geographical variation might be reflective of trophic adaptation following evolutionary arms race between the snake and the prey (eels) in different localities. The preferred trait would likely propagate and remain significant within the geographical population, since the strong behaviour of site fidelity in the species would have minimized gene flow between distant populations. Meanwhile, the in vivo neutralization study verified that the efficacy of the heterologous Sea Snake Antivenom (Australian product) is attributable to the cross-neutralization of SNTX and LNTX, two principal lethal toxins that made up the bulk of L. colubrina venom proteins. The findings also implied that L. colubrina, though could be evolutionarily more related to the terrestrial elapids, has evolved a much streamlined, neurotoxin- and PLA2-predominated venom arsenal, with major antigenicity shared among the true sea snakes and the Australo-Papuan elapids. The findings enrich our current understanding of the complexity of L. colubrina venom and the neutralizing spectrum of antivenom against the principal toxins from this unique elapid lineage.

CONCLUSION: The prevalence of early hypersensitivity reaction to snake antivenom in HSNZ was relatively high. Healthcare providers should be aware of the appropriate method of preparing and administering antivenom, and the management for acute hypersensitivity reactions. This will optimize the management of snakebite and ensure patient safety.