Dispholidus typus (bommslang) snake venom: purification and properties of the coagulant principle

The sweet side of venom: Glycosylated prothrombin activating metalloproteases from Dispholidus typus (boomslang) and Thelotornis mossambicanus (twig snake)

Dispholidus typus and Thelotornis mossambicanus are closely related rear-fanged colubrid snakes that both possess strongly procoagulant venoms. However, despite similarities in overall venom biochemistry and resulting clinical manifestations, the underlying venom composition differs significantly between the two species. As a result, the only available antivenom-which is a monovalent antivenom for D. typus-has minimal cross reactivity with T. mossambicanus and is not a clinically viable option. It was hypothesised that this lack of cross reactivity is due to the additional large metalloprotease protein within T. mossambicanus venom, which may also be responsible for faster coagulation times. In this study, we found that T. mossambicanus venom is a more powerful activator of prothrombin than that of D. typus and that the SVMP transcripts from T. mossambicanus form a clade with those from D. typus. The sequences from D. typus and T. mossambicanus were highly similar in length, with the calculated molecular weights of the T. mossambicanus transcripts being significantly less than the molecular weights of some isoforms on the 1D SDS-PAGE gels. Analyses utilising degylcosylating enzymes revealed that T. mossambicanus SVMPs are glycosylated during post-translational modification, but that this does not lead to the different molecular weight bands observed in 1D SDS-PAGE gels. However, differences in glycosylation patterns may still explain some of the difference between the enzymatic activities and neutralization by antivenom that have been observed in these venoms. The results of this study provide new information regarding the treatment options for patients envenomated by T. mossambicanus as well as the evolution of these dangerous snakes.

Differential heme-mediated modulation of Deinagkistrodon, Dispholidus, Protobothrops and Pseudonaja hemotoxic venom activity in human plasma

Envenomation by vipers with hemotoxic enzymes continues to be a worldwide source of morbidity and mortality. The present work examined the effects of exposure of venom enzymes to carbon monoxide and O-phenylhydroxylamine, agents that modulate the biometal heme, by forming carboxyheme and metheme, respectively. Four venoms obtained from medically important, diverse snake venom found in Africa, Asia and Australia were analyzed. The species that had venom tested in human plasma with thrombelastography and heme modulating agents were Deinagkistrodon acutus, Protobothrops mucrosquamatus, Dispholidus typus and Pseudonaja textilis. These venoms varied four hundred-fold in potency (ng-µg/ml) to exert procoagulant effects on human plasma; further, there was species specific variability in venom inhibition after exposure to carboxyheme or metheme agents. Lastly, using a wide range of carbon monoxide concentrations, it was determined that the factor V component of P. textilis venom was likely inhibited before the factor X component. Further investigation using this thrombelastograph-based, venom "kinetomic" methodology involving heme modulation will demonstrate in time its laboratory and clinical utility.

What killed Karl Patterson Schmidt? Combined venom gland transcriptomic, venomic and antivenomic analysis of the South African green tree snake (the boomslang), Dispholidus typus

Background

Non-front-fanged colubroid snakes comprise about two-thirds of extant ophidian species. The medical significance of the majority of these snakes is unknown, but at least five species have caused life-threatening or fatal human envenomings. However, the venoms of only a small number of species have been explored.

Methods

A combined venomic and venom gland transcriptomic approach was employed to characterise of venom of Dispholidus typus (boomslang), the snake that caused the tragic death of Professor Karl Patterson Schmidt. The ability of CroFab™ antivenom to immunocapture boomslang venom proteins was investigated using antivenomics.

Results

Transcriptomic-assisted proteomic analysis identified venom proteins belonging to seven protein families: three-finger toxin (3FTx); phospholipase A₂ (PLA₂); cysteine-rich secretory proteins (CRISP); snake venom (SV) serine proteinase (SP); C-type lectin-like (CTL); SV metalloproteinases (SVMPs); and disintegrin-like/cysteine-rich (DC) proteolytic fragments. CroFab™ antivenom efficiently immunodepleted some boomslang SVMPs.

Conclusions

The present work is the first to address the overall proteomic profile of D. typus venom. This study allowed us to correlate the toxin composition with the toxic activities of the venom. The antivenomic analysis suggested that the antivenom available at the time of the unfortunate accident could have exhibited at least some immunoreactivity against the boomslang SVMPs responsible for the disseminated intravascular coagulation syndrome that caused K.P. Schmidt's fatal outcome.

General significance

This study may stimulate further research on other non-front-fanged colubroid snake venoms capable of causing life-threatening envenomings to humans, which in turn should contribute to prevent fatal human accidents, such as that unfortunately suffered by K.P. Schmidt.

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The venom proteome of Dispholidus typus (boomslang) is reported.

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Transcriptomic-assisted proteomic analysis identified venom proteins belonging to seven protein families.

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Boomslang venom proteome is dominated (75%) by snake venom PIII-metalloproteinases (PIII-SVMPs).

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CroFab™ antivenom efficiently immunodepleted some boomslang PIII-SVMPs.

Non-front-fanged colubroid snakes: a current evidence-based analysis of medical significance

Non-front-fanged colubroid snakes (NFFC; formerly and artificially taxonomically assembled as "colubrids") comprise about 70% of extant snake species and include several taxa now known to cause lethal or life threatening envenoming in humans. Although the medical risks of bites by only a handful of species have been documented, a growing number of NFFC are implicated in medically significant bites. The majority of these snakes have oral products (Duvernoy's secretions, or venoms) with unknown biomedical properties and their potential for causing harm in humans is unknown. Increasingly, multiple NFFC species are entering the commercial snake trade posing an uncertain risk. Published case reports describing NFFC bites were assessed for evidence-based value, clinical detail and verified species identification. These data were subjected to meta-analysis and a hazard index was generated for select taxa. Cases on which we consulted or personally treated were included and subjected to the same assessment criteria. Cases involving approximately 120 species met the selection criteria, and a small subset designated Hazard Level 1 (most hazardous), contained 5 species with lethal potential. Recommended management of these cases included antivenom for 3 species, Dispholidus typus, Rhabdophis tiginis, Rhabdophis subminiatus, whereas others in this subset without commercially available antivenoms (Thelotornis spp.) were treated with plasma/erythrocyte replacement therapy and supportive care. Heparin, antifibrinolytics and/or plasmapheresis/exchange transfusion have been used in the management of some Hazard Level 1 envenomings, but evidence-based analysis positively contraindicates the use of any of these interventions. Hazard Level 2/3 species were involved in cases containing mixed quality data that implicated these taxa (e.g. Boiga irregularis, Philodryas olfersii, Malpolon monspessulanus) with bites that caused rare systemic effects. Recommended management may include use of acetylcholinesterase inhibitors (e.g. neostigmine) and wound care on a case-by-case basis. Hazard level 3 species comprised a larger group capable of producing significant local effects only, often associated with a protracted bite (eg Heterodon nasicus, Borikenophis (Alsophis) portoricensis, Platyceps (Coluber) rhodorachis). Management is restricted to wound care. Bites by Hazard level 4 species comprised the majority of surveyed taxa and these showed only minor effects of no clinical importance. This study has produced a comprehensive evidence-based listing of NFFC snakes tabulated against medical significance of bites, together with best-practice management recommendations. This analysis assumes increasing importance, as there is growing exposure to lesser-known NFFC snakes, particularly in captive collections that may uncover further species of significance in the future. Careful and accurate documentation of bites by verified species of NFFC snakes is required to increase the evidence base and establish the best medical management approach for each species.

A biochemical and pharmacological examination of Rhamphiophis oxyrhynchus (Rufous beaked snake) venom

The venom of R. oxyrhynchus, a member of the psammophiine subfamily of the colubrid assemblage, was examined for biological activity using biochemical and pharmacological techniques. Venom displayed a high protein content, a complex electrophorectic profile and PLA2 activity but no detectable proteolytic or haematological activities. In the chick biventer cervicis nerve muscle preparation, venom (1-10 microg/ml) displayed postsynaptic neurotoxic activity as evidenced by inhibition of indirect (0.1 Hz, 0.2 ms, supramaximal V) twitches and responses to exogenous acetylcholine (1 mM) and carbachol (20 microM). This inhibitory effect was poorly reversible by washing. Venom (30-50 microg/ml) caused a rapid and readily reversible inhibition of direct (0.1 Hz, 2 ms, supramaximal V) twitches of the chick biventer cervicis nerve muscle preparation without morphological changes to the muscle fibers. Venom (30-100 microg/ml) inhibited electrically-evoked (0.2 Hz, 0.3 ms, 70-100 V) twitches of the prostatic segment of the rat vas deferens. This inhibitory effect was not significantly attenuated by 8-phenyltheophylline (8-PT; 20 microM), idazoxan (1 microM), a combination of ranitidine (0.2 microM) and thioperamide (10 microM) or capsazepine (10 microM). Venom (5 mg/kg) induced hypotension with subsequent cardiovascular collapse in the anaesthetised rat. The cardiovascular collapse was prevented by artificial respiration of the animals prior to venom administration. The biological activities demonstrated by R. oxyrhynchus venom may aid in prey envenomation strategies such as prey immobilisation. This study provides further evidence that colubrid venoms are comprised of multiple components which can display a variety of actions, some of which may be novel, therefore reinforcing the largely untapped potential of colubrid venoms.

Characterization of venom (Duvernoy's secretion) from twelve species of colubrid snakes and partial sequence of four venom proteins

R.E. Hill and S.P. Mackessy. Characterization of venom (Duvernoy's secretion) from twelve species of colubrid snakes and partial sequence of four venom proteins. Toxicon XX, xx-yy, 2000. - Venomous colubrids, which include more than 700 snake species worldwide, represent a vast potential source of novel biological compounds. The present study characterized venom (Duvernoy's gland secretion) collected from twelve species of opisthoglyphous (rear-fanged) colubrid snakes, an extremely diverse assemblage of non-venomous to highly venomous snakes. Most venoms displayed proteolytic activity (casein), though activity levels varied considerably. Low phosphodiesterase activity was detected in several venoms (Amphiesma stolata, Diadophis punctatus, Heterodon nasicus kennerlyi, H. n. nasicus and Thamnophis elegans vagrans), and acetylcholinesterase was found in Boiga irregularis saliva and venom, but no venoms displayed hyaluronidase, thrombin-like or kallikrein-like activities. High phospholipase A(2) (PLA(2)) activity was found in Trimorphodon biscutatus lambda venom, and moderate levels were detected in Boiga dendrophila and D. p. regalis venoms as well as B. dendrophila and H. n. nasicus salivas. Non-reducing SDS-PAGE revealed 7-20 protein bands (3.5 to over 200 kD, depending on species) for all venoms analyzed, and electrophoretic profiles of venoms were typically quite distinct from saliva profiles. Components from A. stolata, Hydrodynastes gigas, Tantilla nigriceps and T. e. vagrans venoms showed protease activity when run on gelatin zymogram gels. N-terminal protein sequences for three 26 kD venom components of three species (H. gigas, H. torquata, T. biscutatus) and one 3.5 kD component (T. nigriceps) were also obtained, and the 3.5 kD peptide showed apparent sequence homology with human vascular endothelial growth factor; these data represent the first sequences of colubrid venom components. Protease, phosphodiesterase and PLA(2) activities are also common to elapid and viperid snake venoms, but it is apparent that numerous other (as yet undescribed) components make up the majority of colubrid venom proteins. The complex nature of venoms produced by most species surveyed, and the high levels of protease or phospholipase A(2) activity of some venoms, suggest that many colubrids could become an important source of human health concern as encounters with these snakes increase.

Enzymatic properties of the Duvernoy's secretion of Blanding's tree snake (Boiga blandingi) and of the mangrove snake (Boiga dendrophila)

Duvernoy's secretion from representatives of the colubrid genus Boiga has been shown by other workers: (1) to contain an alpha-bungarotoxin-like component (Blanding's tree snake, Boiga blandingi); (2) to exhibit acetylcholine receptor binding activity (the brown tree snake, Boiga irregularis); and (3) to react strongly (B. blandingi and the mangrove snake, Boiga dendrophila) with antisera raised against elapid venoms. The present study provides the first evidence for the presence of acetylcholinesterase, a common elapid enzyme, in the Duvernoy's secretion of B. dendrophila and B. blandingi at levels of 122 +/- 7 and 0.36 +/- 0.02 International Enzyme Units, respectively. Constants for inhibition by eserine were 1.25 x 10(-7) M and 2.79 x 10(-7) M, respectively. The Duvernoy's secretion of B. dendrophila exhibited significant phospholipase and haemolytic activities, whereas phosphodiesterase was only weakly present and no thrombin-like activity was observed.

Properties of Duvernoy's secretions from opisthoglyphous and aglyphous colubrid snakes

Relatively little attention has been given to the biological properties of Duvernoy's secretions produced by opisthoglyphous and some aglyphous colubrid snakes. A review is presented of literature pertaining to these secretions. Most detailed analyses of Duvernoy's secretions and their biological properties have been performed since the late 1970s. The dispholidines, Dispholidus typus and Thelotornis sp., and the natricines, Rhabdophis tigrinus and R. subminiata, have received the most attention due to the high toxicity of their secretions and their medical importance. These species produce secretions with variably strong prothrombin-activating activity, defibrinating activity, and hemorrhagic potential. Boigines, and natricines other than Rhabdophis, produce secretions of low to moderate toxicity and are variably hemorrhagic and proteolytic. Xenodontines and homalopsines similarly show hemorrhagic potential with low to moderate toxicity. Neurotoxic activity has been reported only from secretions of the boigines, Boiga blandingi and B. irregularis and the xenodontine, Heterodon platyrhinos. These species produce secretions containing postsynaptically acting components. Analyses of some of these secretions have shown that enzymes common to many ophidian venoms such as phospholipases A and L-amino acid oxidase are uncommon in the colubrid secretions studied. This may be due to few studies assaying for multiple enzyme activities and/or the unavailability of many secretion samples for study. Methods of secretion extraction, storage, and assay are discussed. Projected future research and the adaptive implications of Duvernoy's secretions are considered.

Isolation and characterization of five fibrin(ogen)olytic enzymes from the venom of Philodryas olfersii (green snake)

Five distinct fibrin(ogen)olytic proteinases PofibC1, C2, C3, H and S were isolated by gel filtration and ion-exchange chromatographies. PofibC1, C2, C3 and H are metalloproteinases inhibited by ethylenediamine tetracetic acid (EDTA) or 1,10-phenanthroline. Only PofibH had hemorrhagic activity. PofibS is a serine proteinase, inhibited by phenylmethylsulfonyl fluoride (PMSF) or Torresea cearensis trypsin inhibitor (TCTI). All five enzymes were inhibited by dithiothreitol (DTT) or dithioerythritol (DTE). PofibC1 and C2 presented the same mol. wt of 47,000 and are acidic proteins of pI 6.2 PofibC3 is a basic proteinase of pI 8.5 and mol. wt 45,000. The hemorrhagic proteinase PofibH had a mol. wt of 58,000 and pI of 4.6 and PofibS had a mol. wt of 36,000 and pI of 4.5. The five proteinases degraded fibrin and fibrinogen. PofibC1, C2, C3 and H degraded preferentially A alpha-chains while PofibS cleaved concomitantly A alpha and B beta-chains of fibrinogen. None of these enzymes cleaved the gamma-chain of fibrinogen. When correlated with the thrombin delay time, the most active was PofibS, while PofibH and PofibC1 showed almost no activity. The proteinases also differed in the peptide cleavage of B-chain of insulin. Philodryas olfersii venom promoted in vivo a loss of the circulant plasma fibrinogen, as was observed in experiments with rats.

Characterization of snake venom components acting on blood coagulation and platelet function

Snake venoms can affect blood coagulation and platelet function in various ways. The physicochemical properties and the mechanisms of actions of the snake venom components affecting blood coagulation and platelet function are discussed.

The secretion of Duvernoy's gland of Malpolon monspessulanus induces haemorrhage in the lungs of mice

A toxic protein that induces death of mice with profuse bleeding from the nostrils was isolated from the secretion of Duvernoy's gland of Malpolon monspessulanus (Colubridae). The toxic protein, referred to as CM-b, showed mainly one band on SDS-PAGE corresponding to a mol. wt of 24,000. Its intravenous LD50 in mice was 1 microgram/g and i.v. injections of lethal or sublethal doses induced haemorrhage in the lungs. When injected into the skin of mice, however, the toxin was not haemorrhagic. CM-b showed no proteolytic or procoagulant activity. The nature of this and other components from Duvernoy's secretion of colubrids that cause similar effects remains to be established.

Hemorrhagic, fibrinogenolytic and edema-forming activities of the venom of the colubrid snake Philodryas olfersii (green snake)

The venom of P. olfersii has high hemorrhagic, edema-inducing and fibrin(ogen)olytic activities. It is devoid of thrombin-like, procoagulant, phospholipase A2 and platelet aggregating enzymes. The main activities are metalloproteinases inhibited by metal chelators (EDTA and 1,10-phenanthroline) and sulfhydryl compounds (DTT and cysteine). The hemorrhagic and fibrinogenolytic enzymes were partially purified by gel filtration on HPLC. The hemorrhagic activity of the venom was neutralized by commercial horse antivenoms to Bothrops species, as well as by rabbit antisera specific for hemorrhagic factors isolated from these Bothrops venoms. No immunoprecipitin reactions were obtained, indicating that the few epitopes of the P. olfersii hemorrhagin are involved in these neutralization reactions. The fibrinogenolytic enzyme cleaves A alpha-chain more quickly than the B beta-chain of human fibrinogen. The venom also solubilizes fibrin. This solubilization appears to occur from the hydrolysis of unpolymerized alpha-chain and cross-linked gamma-gamma dimer. The fibrin peptide products are distinct from those produced by plasmin.

Human envenomation by the South American opisthoglyph Clelia clelia plumbea (Wied)

A 4-year-old girl was hospitalized 10 hr after having been envenomated by a 1.4 m Clelia clelia plumbea, a colubrid. Although the patient exhibited pronounced edema and local hemorrhage, she did not manifest systemic symptoms. Because the attending physician viewed the case as a possible Bothrops bite, anti-Bothrops antivenom (FUNED) was administered. All local symptoms disappeared gradually over a period of 3 days.

Effects of snake venoms on hemostasis

Proteins found in venoms, especially of the Viperidae snake family, exert, often with a narrow specificity, activating, inactivating, or other converting effects on different components of the hemostatic and fibrinolytic systems, respectively. Some purified snake venom proteins have become valuable tools in basic research and in diagnostic procedures in hemostaseology. "Procoagulant" as well as "anticoagulant" venom components have been identified in in vitro test systems. "Procoagulant" snake venom components may cause in vivo, upon massive application as in the case of snake-bite of small prey animals, intravascular coagulation leading to circulatory arrest and rapid death. Smaller doses of procoagulant venom components applied to large organisms as in the case of snake-bite accidents in humans, may cause a consumption coagulopathy with localized or generalized bleeding. Highly purified, specific fibrinogen coagulant venom proteinases are used in human medicine to produce therapeutic defibrinogenation. These practically nontoxic venom enzymes may act synergistically with other components aggravating their toxic effects.

Lethal potency and fractionation of Duvernoy's secretion from the brown tree snake, Boiga irregularis

The liquid secretion contained only 15% protein and had relatively low proteolytic activity. The reconstituted crude secretion had a murine i.p. LD50 of 10.33 mg/kg and was not hemorrhagic in doses up to 200 micrograms. Fast Protein Liquid Chromatographic (FPLC) cation exchange analysis of reconstituted crude secretion resulted in resolution of 16 peaks. Lethal activity was identified in three peaks. The major lethal fraction was 12.5% of the secretion protein and had a murine i.p. LD50 of 7.3 mg/kg. A pooled fraction containing two lethal peaks which comprised 9.4% of secretion protein had moderate proteolytic activity and produced myoglobinuria in mice. The fraction had an approximate murine i.p. LD50 of 3.7 mg/kg. Microscopic examination of muscle tissue from mice succumbing to this fraction revealed multifocal myofiber degeneration and necrosis. SDS-PAGE indicated that the major lethal fraction contained three proteins with mol. wts of 12,500, 18,000 and 52,000 and the myotoxic fraction contained two proteins with mol. wts of 14,500 and 17,000. While B. irregularis Duvernoy's secretion has a low lethal index, it does contain a myotoxic fraction with moderate lethal potency. These observations and recent data describing clinical envenomation of several infant patients suggest that large specimens may pose a hazard to infants and small children.

Lethal factors and enzymes in the secretion from Duvernoy's gland of three colubrid snakes

Secretion from Duvernoy's gland of the colubrid snakes Malpolon, Spalerosophis, and Thamnophis was obtained by pilocarpine stimulation and tested for lethality and selected enzymatic activities. Pools of secretion from Malpolon and Spalerosophis were fractionated by gel filtration, and several major active fractions were examined. The secretion from Malpolon had an LD50 of 6.5 micrograms/gm in mice; two lethal fractions with LD50's of 2.75 micrograms/gm and 4.5 micrograms/gm were isolated. One of these fractions appears to be a basic phospholipase A with a molecular weight of about 17,000. Spalerosophis had a secretion with an LD50 of 2.75 micrograms/gm in mice; one main lethal fraction with an LD50 of 2.5 micrograms/gm was isolated. Secretion from Thamnophis had an LD50 of 33.3 micrograms/gm; it was not fractionated owing to a paucity of material. At least two of the snake species examined have toxic secretions that may be important during feeding by killing or weakening and helping to subdue the struggling prey.