The Indian krait (Bungarus caeruleus) is one of the "Big Four" venomous snakes widely distributed in South Asia. The present venomic study reveals that its
venom (Sri Lankan origin) is predominated by
phospholipases A2 (64.5% of total
proteins), in which at least 4.6% are presynaptically-acting β-bungarotoxin A-chains.
Three-finger toxins (19.0%) are the second most abundant, comprising 15.6% κ-
neurotoxins, the potent postsynaptically-acting long
neurotoxins. Comparative chromatography showed that
venom samples from Sri Lanka, India and Pakistan did not exhibit significant variation. These
venoms exhibited high immunoreactivity toward VINS Indian Polyvalent
Antivenom (VPAV). The Pakistani krait
venom, however, had a relatively lower degree of binding, consistent with its moderate neutralization by VPAV (potency=0.3mg
venom neutralized per ml
antivenom) while the Sri Lankan and Indian
venoms were more effectively neutralized (potency of 0.44 mg/ml and 0.48 mg/ml, respectively). Importantly, VPAV was able to neutralize the Sri Lankan and Indian
venoms to a comparable extent, supporting its use in Sri Lanka especially in the current situation where Sri Lanka-specific
antivenom is unavailable against this species. The findings also indicate that the Pakistani B. caeruleus
venom is immunologically less comparable and should be incorporated in the production of a pan-regional, polyspecific
antivenom.
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.