The neurotoxic effect of Naja nubiae (Serpentes: Elapidae) venom from Sudan.

Background: Neurotoxicity is a common feature of elapid snake envenomation. There are limited studies on the toxicity of Naja nubiae venom, the Nubian spitting cobra, from north-east Africa.

Methods: We used the chick biventer cervicis nerve-muscle preparation to demonstrate the neurotoxic effect of N. nubiae venom and to compare it with the potent neurotoxic cobra Naja melanoleuca venom. Venoms were separated by successive reverse-phase high-performance liquid chromatography (RP-HPLC) runs and the molecular mass of the neurotoxins was determined by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS).

Results: Both venoms caused time-dependent inhibition of nerve-mediated twitches with a t90 value of 22.2±1.9 min and 12.9±1.2 min for N. nubiae and N. melanoleuca venoms, respectively. Prior incubation of some commercial antivenom (EchiTab-Plus-ICP [Costa Rica], CSL, Parkville, Victoria, Australia) and snake venom antisera [India]) did not prevent the neurotoxic effect of N. nubiae venom. The chromatographic separation of N. nubiae and N. melanoleuca venoms followed by MALDI-TOF MS analysis revealed that short-chain α-neurotoxin accounted for 8.4% of N. nubiae and 14.8% of N. melanoleuca whole venoms.

Conclusions: N. nubiae venom, which was previously known as cytotoxic venom, exhibits considerable in vitro neurotoxic effects on chick nerve-muscle preparations that may have consequences for antivenom development in north-east Africa.