Cross‐Neutralisation of the Neurotoxic Effects of Egyptian Cobra Venom with Commercial Tiger Snake Antivenom

Abstract

Cross-neutralisation has been demonstrated for haemorrhagic venoms including Echis spp. and Cerastes spp. and for Australia elapid procoagulant toxins. A previous study showed that commercial tiger snake antivenom (TSAV) was able to neutralise the systemic effects of the Egyptian cobra, Naja haje, in vivo but it is unclear if this was true cross-neutralisation. The aim of the current study was to determine whether TSAV can neutralise the in vitro neurotoxic effects of N. haje venom. Both Notechis scutatus (10 lg/ml) and N. haje (10 lg/ml) venoms caused inhibition of indirect (supramaximal V, 0.1 Hz, 0.2 msec.) twitches of the chick biventer cervicis nerve-muscle preparation with t 90 values (i.e. the time to produce 90% inhibition of the original twitch height) of 26 ± 1 min. (n = 4) and 36 ± 4 min.; (n = 4). This effect at 10 lg/ml was significantly attenuated by the prior addition of TSAV (5 U/ml). A comparison of the reverse-phase HPLC profiles of both venoms showed some similarities with peak elution times, and SDS-PAGE analysis elucidated comparable bands across both venoms. Further analysis using Western immunoblotting indicated TSAV was able to detect N. haje venom, and enzyme immunoassay showed that in-house biotinylated polyclonal monovalent N. scutatus antibodies were able to detect N. haje venom. These findings demonstrate crossneutralisation between different and geographically separated snakes supporting potential immunological similarities in snake toxin groups for a large range of snakes. This provides more evidence that antivenoms could be developed against specific toxin groups to cover a large range of snakes.Snake envenoming is an important public health problem in tropical and subtropical countries (e.g. Africa, Asia, Oceania and Latin America). Indeed, it has been estimated that at least 440,000 envenomings and 20,000 deaths occur annually [1]. The effects of systemic envenoming by elapid snakes may include neuromuscular paralysis, myotoxicity, coagulopathy and renal toxicity [2][3][4][5]. Local effects are often seen as well, such as severe pain, swelling and necrosis.The mainstay of treatment for systemic snake envenoming is the administration of either monovalent or polyvalent antivenom. Many underdeveloped countries, in which some of the deadliest snakes inhabit, do not have the resources and/or the financial means to stock, or facilitate the development of appropriate antivenoms. This necessitates the use of antivenoms that are not targeted against the species of snakes in that country. Antivenom paraspecificity, or antivenom crossneutralisation, refers to the ability of antivenom raised against a single species (i.e. monovalent) to neutralise the activity of venom from a different and often unrelated species. This phenomenon is not uncommon [6][7][8][9][10]. Minton (1967) examined the effect of various antivenoms manufactured by CSL Ltd through a series of LD 50 studies using mice and found that they were effective in neutralising a range of both Australian and exotic elapid ...

Use of immunoturbidimetry to detect venom–antivenom binding using snake venoms

“…2), supports previous studies demonstrating cross-reactivity between N. haje (Egyptian cobra) venom and TSAV, using enzyme immunoassay and in vitro neurotoxicity studies (Kornhauser et al, 2013).…”

“…However, there are shortages of antivenom in many parts of the world and there is a need for high quality and effective antivenoms to be developed (Lalloo et al, 2002). An essential part of antivenom development is determining the ability of antivenom to bind to toxins in snake venoms and also the cross-reactivity between particular antivenoms and other snake venoms Kornhauser et al, 2013). This allows effective polyvalent antivenoms to be developed to cover all snakes in a particular geographical region.…”

Immunological cross-reactivity and neutralization of the principal toxins of Naja sumatrana and related cobra venoms by a Thai polyvalent antivenom (Neuro Polyvalent Snake Antivenom)

“…Cross-neutralization of Naja venoms by heterologous antivenom is a well-known phenomemon (Cham et al, 2013;Kornhauser et al, 2013;Leong et al, 2012a). Neuro Polyvalent Snake Antivenom (NPAV) (produced against the venoms of the Thai monocled cobra, Naja kaouthia, and three other Thai elapid snakes) was chosen for this study as it is a commonly used polyvalent antivenom in Thailand and Malaysia, and extensive cross-neutralization data of this antivenom against venoms from various cobras are available for comparison purpose (Leong et al, 2012a).…”

Cross-Neutralisation of In Vitro Neurotoxicity of Asian and Australian Snake Neurotoxins and Venoms by Different Antivenoms

“…This enables the preparation to be used to differentiate between pre- and post-synaptic neurotoxicity [6,33]. The chick biventer preparation is also beneficial for testing the efficacy of antivenoms against neurotoxins in venoms [18,33]. To elicit contractile responses to ACh and CCh, which is required to be able to demonstrate a pre-synaptic site of action, nAChR at the motor end plate must be functioning.…”

“…Despite the structural and functional variations of the toxins within these toxin groups, similarities in their immunogenicity lead to cross-neutralisation by antivenoms raised against different snakes. Cross-neutralisation has been previously reported for some venom and antivenom combinations [13,14,15,16,17,18,19]. In most previous studies examining neurotoxic elapid venoms and antivenoms, cross-neutralisation has been measured by means of the prevention of rodent lethality (ED 50 ) [15,16,20].…”