Venom constituents of Notechis scutatus scutatus (Australian tiger snake) from differing geographic regions

Antiprotozoal Effect of Snake Venoms and Their Fractions: A Systematic Review

Background: Protozoal infection is a lingering public health issue of great concern, despite efforts to produce drugs and vaccines against it. Recent breakthrough research has discovered alternative antiprotozoal agents encompassing the use of snake venoms and their components to cure these infections. This study collated the existing literature to examine the antiprotozoal effect of snake venoms and their fractions. Methods: We conducted a systematic review following the PRISMA guidelines. The PubMed and Embase databases were searched from their inception until 13 October 2021. Articles were screened at the title, abstract and full-text phases. Some additional studies were obtained through the manual search process. Results: We identified 331 studies via the electronic database and manual searches, of which 55 reporting the antiprotozoal effect of snake venoms and their components were included in the review. Around 38% of studies examined the effect of whole crude venoms, and a similar percentage evaluated the effect of a proportion of enzymatic phospholipase A2 (PLA2). In particular, this review reports around 36 PLA2 activities and 29 snake crude venom activities. We also report the notable phenomenon of synergism with PLA2 isoforms of Bothrops asper. Importantly, limited attention has been given so far to the antiprotozoal efficacies of metalloproteinase, serine protease and three-finger toxins, although these venom components have been identified as significant components of the dominant venom families. Conclusion: This study highlights the impact of snake venoms and their fractions on controlling protozoal infections and suggests the need to examine further the effectiveness of other venom components, such as metalloproteinase, serine protease and three-finger toxins. Future research questions in this field must be redirected toward synergism in snake venom components, based on pharmacological usage and in the context of toxicology. Ascertaining the effects of snake venoms and their components on other protozoal species that have not yet been studied is imperative.

A Meta-Analysis of the Protein Components in Rattlesnake Venom

The specificity and potency of venom components give them a unique advantage in developing various pharmaceutical drugs. Though venom is a cocktail of proteins, rarely are the synergy and association between various venom components studied. Understanding the relationship between various components of venom is critical in medical research. Using meta-analysis, we observed underlying patterns and associations in the appearance of the toxin families. For Crotalus, Dis has the most associations with the following toxins: PDE; BPP; CRL; CRiSP; LAAO; SVMP P-I and LAAO; SVMP P-III and LAAO. In Sistrurus venom, CTL and NGF have the most associations. These associations can predict the presence of proteins in novel venom and understand synergies between venom components for enhanced bioactivity. Using this approach, the need to revisit the classification of proteins as major components or minor components is highlighted. The revised classification of venom components is based on ubiquity, bioactivity, the number of associations, and synergies. The revised classification can be expected to trigger increased research on venom components, such as NGF, which have high biomedical significance. Using hierarchical clustering, we observed that the genera's venom compositions were similar, based on functional characteristics rather than phylogenetic relationships.

Australian elapid snake envenomation in cats: Clinical priorities and approach

Practical relevance: No fewer than 140 species of terrestrial snakes reside in Australia, 92 of which possess venom glands. With the exception of the brown tree snake, the venom-producing snakes belong to the family Elapidae. The venom of a number of elapid species is more toxic than that of the Indian cobra and eastern diamondback rattle snake, which has earned Australia its reputation for being home to the world's most venomous snakes. Clinical challenges: The diagnosis of elapid snake envenomation is not always easy. Identification of Australian snakes is not straightforward and there are no pathognomonic clinical signs. In cats, diagnosis of envenomation is confounded by the fact that, in most cases, there is a delay in seeking veterinary attention, probably because snake encounters are not usually witnessed by owners, and also because of the tendency of cats to hide and seek seclusion when unwell. Although the administration of antivenom is associated with improved outcomes, the snake venom detection kit and antivenom are expensive and so their use may be precluded if there are financial constraints. Evidence base: In providing comprehensive guidance on the diagnosis and treatment of Australian elapid snake envenomation in cats, the authors of this review draw on the published veterinary, medical and toxicology literature, as well as their professional experience as specialists in medicine, and emergency medicine and critical care.

A Simple and Novel Strategy for the Production of a Pan-specific Antiserum against Elapid Snakes of Asia

Snakebite envenomation is a serious medical problem in many tropical developing countries and was considered by WHO as a neglected tropical disease. Antivenom (AV), the rational and most effective treatment modality, is either unaffordable and/or unavailable in many affected countries. Moreover, each AV is specific to only one (monospecific) or a few (polyspecific) snake venoms. This demands that each country to prepare AV against its local snake venoms, which is often not feasible. Preparation of a 'pan-specific' AV against many snakes over a wide geographical area in some countries/regions has not been possible. If a 'pan-specific' AV effective against a variety of snakes from many countries could be prepared, it could be produced economically in large volume for use in many countries and save many lives. The aim of this study was to produce a pan-specific antiserum effective against major medically important elapids in Asia. The strategy was to use toxin fractions (TFs) of the venoms in place of crude venoms in order to reduce the number of antigens the horses were exposed to. This enabled inclusion of a greater variety of elapid venoms in the immunogen mix, thus exposing the horse immune system to a diverse repertoire of toxin epitopes, and gave rise to antiserum with wide paraspecificity against elapid venoms. Twelve venom samples from six medically important elapid snakes (4 Naja spp. and 2 Bungarus spp.) were collected from 12 regions/countries in Asia. Nine of these 12 venoms were ultra-filtered to remove high molecular weight, non-toxic and highly immunogenic proteins. The remaining 3 venoms were not ultra-filtered due to limited amounts available. The 9 toxin fractions (TFs) together with the 3 crude venoms were emulsified in complete Freund's adjuvant and used to immunize 3 horses using a low dose, low volume, multisite immunization protocol. The horse antisera were assayed by ELISA and by in vivo lethality neutralization in mice. The findings were: a) The 9 TFs were shown to contain all of the venom toxins but were devoid of high MW proteins. When these TFs, together with the 3 crude venoms, were used as the immunogen, satisfactory ELISA antibody titers against homologous/heterologous venoms were obtained. b) The horse antiserum immunologically reacted with and neutralized the lethal effects of both the homologous and the 16 heterologous Asian/African elapid venoms tested. Thus, the use of TFs in place of crude venoms and the inclusion of a variety of elapid venoms in the immunogen mix resulted in antiserum with wide paraspecificity against elapid venoms from distant geographic areas. The antivenom prepared from this antiserum would be expected to be pan-specific and effective in treating envenomations by most elapids in many Asian countries. Due to economies of scale, the antivenom could be produced inexpensively and save many lives. This simple strategy and procedure could be readily adapted for the production of pan-specific antisera against elapids of other continents.

A comparative study of venomics of Naja naja from India and Sri Lanka, clinical manifestations and antivenomics of an Indian polyspecific antivenom

Naja naja (Indian cobra) from Sri Lanka and India is the WHO Category 1 medically important snakes in both countries. Some antivenom produced against Indian N. naja (NNi) were less effective against Sri Lankan N. naja (NNsl). Proteomes of NNi and NNsl venoms were studied by RP-HPLC, SDS-PAGE and LC/MS/MS. Six protein families were identified in both venoms with the most abundant were the 3 finger toxins (3FTs) where cytotoxins (CTX) subtype predominated, followed by phospholipase A2, cysteine-rich venom protein, snake venom metalloproteases, venom growth factors, and protease inhibitors. Qualitative and quantitative differences in the venomics profiles were observed. Some proteins were isolated from either NNi or NNsl venom. Postsynaptic neurotoxins (NTX) were identified for the first time in NNsl venom. Thus, there are geographic intra-specific variations of venom composition of the two N. naja. The relative abundance of CTX and NTX explained well the clinical manifestations of these venoms. Antivenomics study of an Indian antivenom (Vins) showed the antibodies effectively bound all venom toxins from both snakes but more avidly to the Indian venom proteins. The lower antibody affinity towards the 'heterologous' venom was the likely cause of poor efficacy of the Indian antivenom used to treat NNsl envenoming.

A pharmacological and biochemical examination of the geographical variation of Chironex fleckeri venom

Chironex fleckeri (box jellyfish) are found in the northern tropical waters of Australia. Although C. fleckeri have a wide geographical distribution and are able to swim large distances, adults tend to stay in small restricted areas. Clinical data shows that deaths from envenoming have not been recorded in Western Australia, yet numerous fatalities have occurred in Northern Territory and Queensland waters. One explanation for this discrepancy is a geographical variation in venom composition. This study examined the pharmacological and biochemical profiles of C. fleckeri venom from different geographical locations and seasons. Venoms were screened for cytotoxicity using a rat aortic smooth muscle cell line (A7r5). While all venoms caused concentration-dependent cytotoxicity, differences were seen in the potency of venoms from Mission Beach and Weipa, when collected in different seasons, as indicated by IC(50) values. Similarly venoms collected within the same season, from different locations around Australia, displayed marked differences in venom composition as shown by size exclusion HPLC and SDS-PAGE profiles which indicated the absence or reduced quantity of 'peaks' in some venoms. Based on IC(50) data obtained from the cell assay, the effects of the most potent (i.e. from Weipa in 2006) and the least potent (i.e. from Broome in 2007) venoms were examined in anesthetised rats. Both venoms at 10 microg/kg (i.v.) caused a transient hypertensive phase followed by cardiovascular collapse. However, at 4 microg/kg (i.v.) venom from Weipa 2006 caused a transient hypertensive phase followed by a transient decrease in MAP while venom from Broome 2007 only caused a small transient increase in MAP. This study demonstrates that there is considerable geographical variation in the composition of C. fleckeri venoms which is most distinct between specimens from western and eastern Australia and may explain the geographical variation in reported deaths.

A comparative analysis of the clotting and fibrinolytic activities of the snake venom (Bothrops atrox) from different geographical areas in Venezuela

Venom constitution within the same snake species can present considerable geographical variations. Bothrops atrox venoms were obtained from adult snakes captured at different geographical locations: Parguasa (Bolívar state); Puerto Ayacucho 1, Serranía del Cuao and Puerto Ayacucho 2 (Amazon state). The coagulant and fibrinolytic activities of these venoms were compared. Amidolytic activity of crude snake venom was measured by a micromethod designed in our laboratory. Coagulant activity on plasma and fibrinogen due to thrombin-like activity in venoms was also determined. Crude snake venom fibrinolytic activity by the fibrin plate method was assayed. Chromatographic studies were developed on Protein-Pack 300 column. Polyacrylamide gel electrophoresis was carried out under reduced conditions. After SDS-PAGE of samples, the fibrin-zymography was tested on agarose-fibrin plates. The results demonstrated several differences among B. atrox venoms from different geographical areas. Chromatograms and SDS-PAGE profiles indicated that venoms from the same species presented differences in the molecular mass of their components. The procoagulant activity depended on the utilized method (amidolytic versus clotting). Parguasa and Puerto Ayacucho 2 venoms presented procoagulant activity for both methods. Furthermore, Parguasa venom had also the highest hemorrhagic activity and the lowest LD50. In relation to the fibrinolytic activity, Puerto Ayacucho 1 venom was the most active, equally for fibrin plates as for the amidolytic method (t-PA like). This venom had the lowest coagulant activity, which induced us to think that probably its procoagulant activity was interfered by its fibrinolytic activity.

Comparison of active venom components between Eastern brown snakes collected from South Australia and Queensland

The abundance and activity of the prothrombin activator (pseutarin C) within the venom of the Eastern brown snake (Pseudonaja textilis textilis) is the primary determinant of its coagulation potency. Textilinin-1, also in this venom, is a plasmin inhibitor which is thought to exert its toxic effects through the slowing of fibrinolysis. The aim of this report is to determine if there are differences in the potency of the venom from Eastern brown snakes collected from South Australia (SA) compared to those from Queensland (QLD). A concentration of 0.4 microg/ml venom protein from six QLD specimens clotted citrated plasma in an average time of 21.4+/-3.3 s compared to 68.7+/-2.4 s for the same amount of SA venom (averaged for six individuals). The more potent procoagulant activity of the QLD venom was measured between 0.4 and 94 microg/ml venom protein in plasma. The anti-plasmin activity of textilinin was also greater in the venom of the snakes collected from QLD, causing full inhibition of plasmin at approximately 1.88 microg/ml of venom protein compared to approximately 7.5 microg/ml for the SA venoms. It is concluded that geographic differentiation of the Eastern brown snakes results in significant differences venom potency.

Purification and characterization of an anticoagulant phospholipase A(2) from Indian monocled cobra (Naja kaouthia) venom

An anticoagulant, non-toxic phospholipase A(2) was isolated from the venom of Indian monocled cobra (Naja kaouthia) by a combination of ion-exchange chromatography on CM-Sephadex C-50 and gel filtration on Sephadex G-50. This purified protein named NK-PLA(2)-I, had a subunit molecular mass of 13.6 kDa and migrated as a dimer under non-reduced condition in SDS-PAGE. NK-PLA(2)-I was a highly thermostable protein requiring basic pH optima for its catalytic activity and showed preferential hydrolysis of phosphotidylcholine. This protein exhibited higher anticoagulant, indirect hemolysis, liver and heart tissue damaging activity but exerted less toxicity, direct hemolysis, edema and lung tissue damaging activity as compared to whole venom. Treatment of NK-PLA(2)-I with rho-BPB, TPCK, PMSF, antivenom and heating had almost equal effect on PLA(2), and other pharmacological properties except in vitro tissue damaging activity. Current investigation provides a fairly good indication that NK-PLA(2)-I induces various pharmacological effects by mechanisms, which are either dependent or independent of its catalytic activity.

Investigation of coagulopathy in three cases of tiger snake (Notechis ater occidentalis) envenomation

AIMS

To investigate the severe coagulopathy (fibrinogen < 1.0 g/l) that occurs in some cases of tiger snake envenomation. Specifically, to determine the concentration of clotting factors on presentation and during resolution of the coagulopathy.

METHODS

Clotting factors II, V, VII, VIII, IX, XI were assayed on all coagulation samples received from three successive cases of severe tiger snake envenomations. Assays were performed at dilutions of 1:5 and 1:10 using an MLA 1600c automated coagulation analyser and Dade Behring factor-deficient plasmas, controls and standards. D-dimers were assayed using Agen Dimertest latex kit, fibrinogen was determined using the Clauss method and platelet counts were performed using Abbott Cell-Dyn 4000 analysers.

RESULTS

The activity of the coagulation factors of the intrinsic pathway was reduced (factor VIII < 44% in all cases, factor IX < 33%, factor XI < 52% in Cases 1 and 2) but the results for the two dilutions were not parallel. In one case, factor VIII and factor IX activity increased 2-fold prior to the administration of blood products. Treatment with blood products corrected the coagulation indices in two out of the three cases but factor V remained low in one case (25%).

CONCLUSIONS

The non-parallel results and the apparent increase in factor levels prior to treatment may result from the transient presence of an inhibitor to factors VIII, IX and XI in cases of tiger snake envenomation. Insight into the effects of snake venom on individual coagulation factors could be beneficial when considering new treatments for the coagulopathy induced by snake envenomation.

Electrospray liquid chromatography/mass spectrometry fingerprinting of Acanthophis (death adder) venoms: taxonomic and toxinological implications

Death adders (genus Acanthophis) are unique among elapid snakes in both morphology and venom composition. Despite this genus being among the most divergent of all elapids, the venom has been historically regarded as relatively quite simple. In this study, liquid chromatography/mass spectrometry (LC/MS) analysis has revealed a much greater diversity in venom composition, including the presence of molecules of novel molecular weights that may represent a new class of venom component. Furthermore, significant variation exists between species and populations, which allow for the LC/MS fingerprinting of each species. Mass profiling of Acanthophis venoms clearly demonstrates the effectiveness of this technique which underpins fundamental studies ranging from chemotaxonomy to drug design.

Variations in biochemical and pharmacological properties of Indian cobra (Naja naja naja) venom due to geographical distribution

Indian cobra (Naja naja naja) venom obtained from three different geographical regions was studied in terms of electrophoretic pattern, biochemical and pharmacological activities. SDS-PAGE banding pattern revealed significant variation in the protein constituents of the three regional venoms. The eastern venom showed highest indirect hemolysis and hyaluronidase activity. In contrast, western and southern venoms were rich in proteolytic activity. All the three regional venoms were devoid of p-tosyl-L-arginine methyl ester hydrolysing activity. The eastern venom was found to be most lethal among the three regional venoms. The lethal potency varied as eastern > western > southern regional venoms. In addition, all the three regional venoms showed marked variations in their ability to induce symptoms/signs of neurotoxicity, myotoxicity, edema and effect on plasma coagulation process. Polyclonal antiserum prepared against the venom of eastern region cross-reacted with both southern and western regional venoms, but varied in the extent of cross-reactivity by ouchterlony immunodiffusion and ELISA.

Species and regional variations in the effectiveness of antivenom against the in vitro neurotoxicity of death adder (Acanthophis) venoms

Although viperlike in appearance and habit, death adders belong to the Elapidae family of snakes. Systemic envenomation represents a serious medical problem with antivenom, which is raised against Acanthophis antarcticus venom, representing the primary treatment. This study focused on the major Acanthophis variants from Australia and islands in the Indo-Pacific region. Venoms were profiled using liquid chromatography-mass spectrometry, and analyzed for in vitro neurotoxicity (0.3-10 microg/ml), as well as the effectiveness of antivenom (1-5 units/ml; 10 min prior to the addition of 10 microg/ml venom). The following death adder venoms were examined: A. antarcticus (from separate populations in New South Wales, Queensland, South Australia, and Western Australia), A. hawkei, A. praelongus, A. pyrrhus, A. rugosus, A. wellsi, and venom from an unnamed species from the Indonesian island of Seram. All venoms abolished indirect twitches of the chick isolated biventer cervicis nerve-muscle preparation in a dose-dependent manner. In addition, all venoms blocked responses to exogenous acetylcholine (1 mM) and carbachol (20 microM), but not KCl (40 mM), suggesting postsynaptic neurotoxicity. Death adder antivenom (1 unit/ml) prevented the neurotoxic effects of A. pyrrhus, A. praelongus, and A. hawkei venoms, although it was markedly less effective against venoms from A. antarcticus (NSW, SA, WA), A. rugosus, A. wellsi, and A. sp. Seram. However, at 5 units/ml, antivenom was effective against all venoms tested. Death adder venoms, including those from A. antarcticus geographic variants, differed not only in their venom composition but also in their neurotoxic activity and susceptibility to antivenom. For the first time toxicological aspects of A. hawkei, A. wellsi, A. rugosus, and A. sp. Seram venoms were studied.

A pharmacological examination of venoms from three species of death adder (Acanthophis antarcticus, Acanthophis praelongus and Acanthophis pyrrhus)

The common (A. antarcticus), northern (A. praelongus) and desert (A. pyrrhus) death adders are species belonging to the Acanthophis genus. The present study compared some pharmacological aspects of the venoms of these species and examined the in vitro efficacy of death adder antivenom. Neurotoxicity was determined by the time to produce 90% inhibition (t(90)) of indirect (0.1 Hz, 0.2 ms, supramaximal voltage) twitches in the chick biventer cervicis nerve-muscle (3-10 microg/ml) and mouse phrenic nerve-diaphragm (10 microg/ml) preparations. A. praelongus venom was significantly less neurotoxic than A. antarcticus venom but was not significantly different from A. pyrrhus venom. In the biventer muscle, all three venoms (3-10 microg/ml) abolished responses to exogenous ACh (1 mM) and carbachol (20 microM), but not KCl (40 mM), indicating activity at post-synaptic nicotinic receptors. All venoms (30 microg/ml) failed to produce significant inhibition of direct twitches (0.1 Hz, 2.0 ms, supramaximal voltage) in the chick biventer cervicis nerve-muscle preparation. However, A. praelongus (30 microg/ml) venom initiated a significant direct contracture of muscle, indicative of some myotoxic activity. The prior (10 min) administration of death adder antivenom (1 unit/ml), which is raised against A. antarcticus venom, markedly attenuated the twitch blockade produced by all venoms (10 microg/ml). Administration of antivenom (1.5 units/ml) at t(90) markedly reversed, over a period of 4 h, the inhibition of twitches produced by A. praelongus (3 microg/ml, 72+/-6% recovery) and A. pyrrhus (3 microg/ml, 51+/-9% recovery) but was less effective against A. antarcticus venom (3 microg/ml, 22+/-7% recovery). These results suggest that all three venoms contain postsynaptic neurotoxins. Death adder antivenom displayed differing efficacy against the in vitro neurotoxicity of the three venoms.

Characterisation of the biochemical and biological variations from the venom of the death adder species (Acanthophis antarcticus, A. praelongus and A. pyrrhus)

We report on species variation in the venoms of the three species of death adder; the Common death adder (Acanthophis antarcticus), the Northern death adder (Acanthophis praelongus) and the Desert death adder (Acanthophis pyrrhus). The venoms were found to vary in their biochemical (chromatography) and biological (PLA(2) activity, anticoagulant activity and reactivity with commercial death adder antivenom) properties. Each species produced significant differences in the profile and distribution of PLA(2) activity, when whole venom was applied to a cation-exchange Mono-S column. PLA(2) enzymes were purified from each venom and termed acanthoxin B (from A. praelongus), acanthoxin C (from A. pyrrhus) and the previously characterised acanthoxin A (from A. antarcticus). Acanthoxin B and C showed lower enzymatic activities than acanthoxin A (4.0, 13.7 and 23.9 micromol of phospholipid hydrolyzed/min/mg protein, respectively). N-terminal sequencing revealed acanthoxin B to share highest homology with the numerous PLA(2) isozymes (Pa-12C, Pa-1G, Pa-12A) from the King brown snake (Pseudechis australis) and Acanthin I from the Common death adder. Similar to acanthoxin A, acanthoxin C showed highest homology with Acanthin I/II, and pseudexin A-chain from the Red-bellied black snake (Pseudechis porphyriacus). Whole venom from A. antarcticus, A. praelongus and A. pyrrhus each showed weak anticoagulant activity (being able to prolong coagulation of the plasma for 107, 220 and 195 s, respectively). By immunodiffusion, each venom produced precipitation bands against commercial death adder antivenom.

Structure-function studies on Taiwan cobra long neurotoxin homolog

A novel long neurotoxin homolog was purified from Naja naja atra (Taiwan cobra) venom using the combination of ion exchange chromatography and reverse phase high performance liquid chromatography. The determined protein sequence was essentially the same as that deduced from the cDNA amplified by reverse transcriptase-polymerase chain reaction. The long neurotoxin homolog exhibited an activity that inhibited acetylcholine-induced muscle contractions, as with N. naja atra cobrotoxin. The degree of inhibition caused by the addition of long neurotoxin homolog was approximately 70% of that observed with the addition of cobrotoxin. Unlike the well-known short and long neurotoxins, this neurotoxin homolog contained two additional cysteine residues forming a disulfide linkage in the N-terminal region. Circular dichroism measurement and computer models of the neurotoxin reveal that its secondary structure was not abundant in beta-sheet as noted with short and long neurotoxins. This less ordered structure may be associated with the lower activity noted with the long neurotoxin homolog. Together with the finding that the known long neurotoxin homologs exclusively appear in the venoms of the Naja and Bungarus genera, the long neurotoxin homologs should represent an evolutionary branch from the long and short neurotoxins in the Elapidae family.

Structure-function properties of venom components from Australian elapids

A comprehensive review of venom components isolated thus far from Australian elapids. Illustrated is that a tremendous structural homology exists among the components but this homology is not representative of the functional diversity. Further, the review illuminates the overlooked species and areas of research.

Anions and the anomalous gel filtration behavior of notexin and scutoxin

Based on their mol. wts, notexin and scutoxin elute later than expected from gel filtration columns in multiple peaks [Francis et al. (1991) Toxicon 29, 85-96]. Notexins present in these peaks have identical amino acid sequences and unmodified amino acid side-chains. Scutoxin is an isoform of notexin which contains arginine at position 16 and glutamate at position 82. Like notexin, it also elutes in different fractions on a gel filtration column, yet the fractions show identical amino acid sequence. This perplexing chromatographic behavior appears to be caused by the association of these proteins with different anions, since dissolving notexin in buffers containing different anions produces up to a 30% change in elution volume. Certain anions promote an apparent reduction in the interaction of notexin with gel filtration matrix, hence earlier elution. These anions include citrate, 3-phosphoglycerate and 2-phosphoglycerate, which also inhibit the PLA2 activity of notexin. However, even under conditions which minimize protein-matrix interaction the toxins elute later than expected based on their mol. wt.

A comparative study on the biological properties of venoms from juvenile and adult common tiger snake (Notechis scutatus) venoms

1. The biological properties of venoms from juvenile and adult common tiger snakes (Notechis scutatus) were compared. 2. The lethality, procoagulant activity and enzymatic activities of the juvenile venom were not substantially different from those of the adult venom. 3. Electrophoretic studies, however, indicated some minor differences in the protein composition of the juvenile and adult venoms.