Snake venoms and hemostasis

A review on snake venom extracellular vesicles: Past to present

Around 95% of snake venom is protein. Along with the soluble proteins, snake venom also contains proteins encapsulated in vesicles known as Snake Venom Extracellular Vesicles (SVEV). SVEVs are nano-sized membrane-bound vesicles released from the snake venom gland cells. The available published research works on SVEVs are minimal. Extracellular vesicles in the Snake Venom gland were initially discovered during the histopathological analysis of the Crotalus durissus terrificus snakes' venom gland. Later, various techniques were employed to isolate and characterize the SVEVs. The cargo of SVEV consists of a variety of proteins like Phospholipase A-2, C-type Lectins, L-Amino Acid Oxidase, Cysteine-Rich Secretory Proteins, Serine Proteinases, Dipeptidyl Peptidase-IV, Aminopeptidase-A, Ecto-5'-nucleotidases, Disintegrins. Proteomic data revealed the presence of some exclusive proteins in the SVEVs, and the other proteins are in varying concentrations in the SVEVs compared to their whole Venom. Interaction of SVEVs with mammalian cell lines showed the disruption of primary physiological functions leads to host immune modulation, and long-term effects of envenoming. Snakebite victim's blood showed variations in the specific Extracellular vesicle concentration. It has been hypothesized that SVEVs are responsible for long-term toxicity. The current review focuses on the various techniques adopted to isolate and characterize SVEVs and discusses the exclusiveness and variations of SVEV proteins and their role in snakebites.

Biochemical and toxicological profiles of venoms from an adult female South American bushmaster (Lachesis muta rhombeata) and her offspring

In this work, we compared the biochemical and toxicological profiles of venoms from an adult female specimen of Lachesis muta rhombeata (South American bushmaster) and her seven offspring born in captivity, based on SDS-PAGE, RP-HPLC, enzymatic, coagulant, and hemorrhagic assays. Although adult and juvenile venoms showed comparable SDS-PAGE profiles, juveniles lacked some chromatographic peaks compared with adult venom. Adult venom had higher proteolytic (caseinolytic) activity than juvenile venoms (p < 0.05), but there were no significant inter-venom variations in the esterase, PLA2, phosphodiesterase and L-amino acid oxidase (LAAO) activities, although the latter activity was highly variable among the venoms. Juveniles displayed higher coagulant activity on human plasma, with a minimum coagulant dose ∼42% lower than the adult venom (p < 0.05), but there were no age-related differences in thrombin-like activity. Adult venom was more fibrinogenolytic (based on the rate of fibrinogen chain degradation) and hemorrhagic than juvenile venoms (p < 0.05). The effective dose of Bothrops/Lachesis antivenom (produced by the Instituto Butantan) needed to neutralize the coagulant activity was ∼57% greater for juvenile venoms (p < 0.05), whereas antivenom did not attenuate the thrombin-like activity of juvenile and adult venoms. Antivenom significantly reduced the hemorrhagic activity of adult venom (400 μg/kg, i. d.), but not that of juvenile venoms. Overall, these data indicate a compositional and functional ontogenetic shift in L. m. rhombeata venom.

Daboxin P, a phospholipase A2 of Indian Daboia russelii venom, modulates thrombin-mediated platelet aggregation

Daboxin P, reported earlier from the venom of Daboia russellii, disturbs the blood coagulation cascade by targeting factor X and factor Xa. The present study exhibits that Daboxin P also inhibits platelet aggregation induced by various agonists. The thrombin-induced platelet aggregation was inhibited maximum whereas inhibition of collagen-induced platelet aggregation was found to be 50% and no inhibition of adenosine diphosphate (ADP) and arachidonic acid-induced aggregation was observed. Daboxin P dose-dependently inhibited the thrombin-induced platelet aggregation with Anti-Aggregation 50 (AD50 ) dose of 55.166 nM and also reduced the thrombin-mediated calcium influx. In-silico interaction studies suggested that Daboxin P binds to thrombin and blocks its interaction with its receptor on the platelet surface. Quenching of thrombin's emission spectrum by Daboxin P and electrophoretic profiles of pull-down assay further reveals the binding between Daboxin P and thrombin. Thus, the present study demonstrates that Daboxin P inhibits thrombin-induced platelet aggregation by binding to thrombin.

Comparing Traditional and Toxin-Oriented Approaches towards Antivenom Production against Bitis arietans Snake Venom

Accidents with snakes are responsible for about 32,000 deaths annually in sub-Saharan Africa, caused mostly by snakes from the genus Bitis, in particular Bitis arietans. B. arietans venom is composed of a complex mixture of toxins, mainly metalloproteases, serine proteases, phospholipases, lectins, and disintegrins. In this work, we compared two approaches to anti-B. arietans antivenom production: immunization with crude snake venom ("traditional approach") and immunization with selected key toxins isolated from the snake venom ("toxin oriented" approach). Fractions from B. arietans venom were isolated by size exclusion chromatography. Crude venom and samples containing serine proteases or metalloproteases were selected for the immunization of BALB/c mice. Anti-B. arietans and anti-serine proteases plasmas showed a similar recognition profile and higher titers and affinity than the anti-metalloproteases plasma. Cross-recognition of other Bitis venoms was observed, but with low intensity. Although the plasma of all experimental groups inhibited the enzymatic activity of B. arietans venom in vitro, in vivo protection was not achieved. Our results have shown limitations in both approaches considered. Based on this, we proposed a model of polyclonal, species-specific, monovalent antivenoms that could be used as a base to produce customizable polyvalent sera for use in sub-Saharan Africa.

A potent anticoagulant hybrid of snake venom derived FIX-binding protein and anti-factor IX RNA aptamer: Assessed by in-silico and electrochemical analyses

Anticoagulant therapies are crucial in the management of surgical complications as well as the prophylaxis of thrombosis. Many studies are being conducted on the Habu snake-venom anticoagulant, FIX-binding protein (FIX-Bp), for its greater potency and strong affinity to FIX clotting factor. On the other hand, the capacity to promptly reverse such acute anticoagulation is equally important. Combining a reversible anticoagulant with FIX-Bp may be advantageous in maintaining the balance between adequate anticoagulation and repealing when necessary. In this study, authors integrated FIX-Bp and RNA aptamer-based anticoagulants into a single target, FIX clotting factor, in order to achieve a robust anticoagulant effect. An in-silico and electrochemical approach were used to investigate the combination of FIX-Bp and RNA aptamers as a bivalent anticoagulant and to verify the competing or predominant binding sites of each anticoagulant. The in-silico analysis discovered that both the venom- and aptamer-anticoagulant had a strong affinity for the FIX protein at the Gla-domain and EGF-1 domain by holding 9 conventional hydrogen bonds with the binding energy of -34.859 kcal/mol. The electrochemical technique verified that both anticoagulants had different binding sites. The impedance load upon RNA aptamer binding to FIX protein was 14 %, whereas the addition of FIX-Bp caused a significant impedance rise of 37 %. This indicates that the addition of aptamers prior to FIX-Bp is a promising strategy for the conception of a hybrid anticoagulant.

Neutrophil-mediated erythrophagocytosis following Russell's viper (Daboia russelii) bite

Snakebite envenomation is regarded as a high-priority neglected tropical disease by the World Health Organisation, as it results in significant loss of lives and permanent disabilities. Russell's viper is one of the snakes that causes morbidities, mortalities and disabilities in India. The clinical presentation of Russell's viper envenomation is characterised by local envenoming effects, tissue damage, venom-induced coagulopathy, neurotoxicity, and kidney injury. However, venom composition and its mechanisms of toxicity are highly variable even within snakes of the same species including Russell's viper. This variation in venom composition results in a broad range of clinical complications. Here we present a previously undocumented case of neutrophil-mediated erythrophagocytosis in a healthy 28-year-old female following Russell's viper bite. Systemic envenomation effects and bleeding abnormalities in this patient were corrected by the administration of polyvalent antivenom. Two days later, the patient developed progressive swelling and ecchymosis in the bitten limb. Observed abnormal limits within blood testing were followed up by a peripheral blood smear where it was found that 30% of neutrophils had phagocytosed erythrocytes as they were found within the cytoplasm. The patient underwent a fasciotomy for compartmental syndrome and received packed red cells and a course of corticosteroids. Following this treatment, the patient made a full recovery. This case report outlines a previously undocumented pathological event induced by Russell's viper envenomation, guiding diagnosis and treatment. Clinicians' knowledge of the mechanisms of toxicity of Russell's viper envenomation and its clinical manifestations are essential for improving the treatment of snakebites to achieve positive outcomes.

Platelet aggregation inhibitors from Bothrops alternatus snake venom

Snake venoms are a complex mixture of proteins and peptides that can activate/inhibit platelet aggregation. Bothrops alternatus venom include three main families: metalloproteinases (SVMPs), serinoproteinases (SVSPs) and phospholipases A₂ (PLA₂s), among other minor components. In this work, we used inhibitor cocktails (containing Na₂-EDTA, PMSF and/or pBPB) to investigate the effect of these three families and of baltergin (a PIII SVMP) on platelet aggregation by a turbidmetric method using a microplate reader. Cocktails 1 (active SVMPs) and 2 (active PLA₂s) significantly reduced aggregation induced by ristocetin and collagen and by collagen and thrombin, respectively. Cocktail 3 (active SVSPs) showed a mild activation of aggregation, indicating the content of thrombin-like enzymes (TLEs) in this venom is low. Cocktail 4 (active minor components) displayed inhibitory effect with all agonists assayed (ristocetin, ADP, collagen and thrombin) but at higher IC₅₀ values. Baltergin exhibited inhibitory effect when the catalytic domain was active for ristocetin-stimulated platelet aggregation and showed a non-enzymatic mechanism of inhibition when collagen was used as agonist. It was not able to disaggregate platelet thrombus. We conclude that B. alternatus venom is a source of natural inhibitors of platelet aggregation due to the action of SVMPs and PLA₂s. Other minor components such as C-type lectins likely contribute to the antiplatelet effect. The interest in knowing the action of venom components on platelet function lies both in the understanding of the pathophysiology of snake bite envenomation and in their biotechnological application.

The Middle Eastern Cousin: Comparative Venomics of Daboia palaestinae and Daboia russelii

Among the medically most important snakes in the world, the species belonging to the genus Daboia have been attributed to the highest number of human envenomings, deaths and disabilities. Given their significant clinical relevance, the venoms of Russell's vipers (D. russelii and D. siamensis) have been the primary focus of research. In contrast, the composition, activity, ecology and evolution of venom of its congener, the Palestine viper (D. palaestinae), have remained largely understudied. Therefore, to unravel the factors responsible for the enhanced medical relevance of D. russelii in comparison to D. palaestinae, we comparatively evaluated their venom proteomes, biochemical activities, and mortality and morbidity inflicting potentials. Furthermore, the synthesis and regulation of venom in snakes have also remained underinvestigated, and the relative contribution of each venom gland remains unclear. We address this knowledge gap by sequencing the tissue transcriptomes of both venom glands of D. palaestinae, and comparatively evaluating their contribution to the secreted venom concoction. Our findings highlight the disparity in the venom composition, function and toxicities of the two Daboia species. We also show that toxin production is not partitioned between the two venom glands of D. palaestinae.

A Review of the Proteomic Profiling of African Viperidae and Elapidae Snake Venoms and Their Antivenom Neutralisation

Snakebite envenoming is a neglected tropical disease (NTD) that results from the injection of snake venom of a venomous snake into animals and humans. In Africa (mainly in sub-Saharan Africa), over 100,000 envenomings and over 10,000 deaths per annum from snakebite have been reported. Difficulties in snakebite prevention and antivenom treatment are believed to result from a lack of epidemiological data and underestimated figures on snakebite envenoming-related morbidity and mortality. There are species- and genus-specific variations associated with snake venoms in Africa and across the globe. These variations contribute massively to diverse differences in venom toxicity and pathogenicity that can undermine the efficacy of adopted antivenom therapies used in the treatment of snakebite envenoming. There is a need to profile all snake venom proteins of medically important venomous snakes endemic to Africa. This is anticipated to help in the development of safer and more effective antivenoms for the treatment of snakebite envenoming within the continent. In this review, the proteomes of 34 snake venoms from the most medically important snakes in Africa, namely the Viperidae and Elipdae, were extracted from the literature. The toxin families were grouped into dominant, secondary, minor, and others based on the abundance of the protein families in the venom proteomes. The Viperidae venom proteome was dominated by snake venom metalloproteinases (SVMPs-41%), snake venom serine proteases (SVSPs-16%), and phospholipase A₂ (PLA₂-17%) protein families, while three-finger toxins (3FTxs-66%) and PLA₂s (16%) dominated those of the Elapidae. We further review the neutralisation of these snake venoms by selected antivenoms widely used within the African continent. The profiling of African snake venom proteomes will aid in the development of effective antivenom against snakebite envenoming and, additionally, could possibly reveal therapeutic applications of snake venom proteins.

Venom induced consumption coagulopathy and performance of 20-min whole blood clotting test for its detection in viperid envenomation

Background:

Venom induced consumption coagulopathy (VICC) and its underlying mechanisms have not been fully elucidated in viperid envenomation (VE), especially among Indian patients. We evaluated for VICC in VE, assessed the performance of 20-min whole blood clotting test (20WBCT) for VICC detection and also studied predictors of VICC.

Methods:

This hospital-based observational study enrolled 103 consecutive patients (age ⩾ 12 years) of snakebite admitted within 24 h of bite, with features of VE. They underwent 20WBCT, prothrombin time (PT)/international normalised ratio (INR), plasma fibrinogen and D-dimer testing during first 24 h after enrolment. Overt VICC (defined by overt bleeding), subclinical VICC (INR ⩾ 1.4 and/or fibrinogen < 2g/L, without overt bleeding), disseminated intravascular coagulation (DIC) (overt/non-overt, defined based on International Society on Thrombosis and Haemostasis (ISTH) DIC score) and primary defibrination (PDF) were evaluated among patients.

Results:

VICC overall was noted in 77 (≈75%) and overt VICC in 52 (≈50%). DIC (overt/non-overt) was noted in 59 (≈77%) and PDF in 2 (2.6%) patients with VICC. Sensitivity, specificity, positive predictive value and negative predictive value of 20WBCT for VICC detection were 98.7% (95%CI: 92.9–99.9%), 65.4% (95%CI: 44.3–82.8%), 89.4% (95%CI: 83.3–93.5%) and 94.4% (95%CI: 70.4–99.2%) respectively. Severe cellulitis in bitten limb predicted reduced VICC risk.

Conclusion:

Majority (75%) of patients with VE had VICC and 68% with VICC had overt bleeding. DIC (overt/non-overt) was the predominant contributor to VICC. Though 20WBCT is a good screening test for VICC, false positive results should be kept in mind before deciding on snake antivenom treatment.

Fibrinogenolysis in Venom-Induced Consumption Coagulopathy after Viperidae Snakebites: A Pilot Study

Envenomations that are caused by Viperidae snakebites are mostly accompanied by venom-induced consumption coagulopathy (VICC) with defibrination. The clinical course of VICC is well described; however, reports about its detailed effects in the hemocoagulation systems of patients are sparse. In this pilot study, we prospectively analyzed the changes in plasma fibrinogen that were caused by the envenomation of six patients by five non-European Viperidae snakes. Western blot analysis was employed and fibrinogen fragments were visualized with the use of specific anti-human fibrinogen antibodies. All of the studied subjects experienced hypo- or afibrinogenemia. The western blot analysis demonstrated fibrinogenolysis of the fibrinogen chains in all of the cases. Fibrinogenolysis was considered to be a predominant cause of defibrination in Crotalus, Echis, and Macrovipera envenomation; while, in the cases of VICC that were caused by Atheris and Calloselasma envenomation, the splitting of the fibrinogen chains was present less significantly.

Medical Management after Lancehead Snakebite in North Amazon: A Case Report of Long-Term Disability

Snakebites are a major public health problem in indigenous communities in Brazil, leading to acute local and systemic damage with resulting deficiencies. Long-term musculoskeletal disabilities related to snakebites have been a neglected area of research. Bothrops (lancehead) snakes are responsible for most of the permanent sequelae related to snakebites in Latin America. Here, we present a case report of a 32-year-old male indigenous patient who was envenomed by a Bothrops species. The patient was clinically followed for a period of approximately 2 years and 6 months, during which time he experienced a loss of musculoskeletal tissue and required several medical procedures such as debridement, tissue reconstruction, and physical therapy, which resulted in a recovery of mobility, though with a permanent sequelae in gait. This case report shows how snakebites have a significant impact on health systems, as victims require physiotherapy, plastic surgery, and orthopedics services, as well as social support for reintegration into their local communities.

The Enzymatic Core of Scorpion Venoms

Enzymes are an integral part of animal venoms. Unlike snakes, in which enzymes play a primary role in envenomation, in scorpions, their function appears to be ancillary in most species. Due to this, studies on the diversity of scorpion venom components have focused primarily on the peptides responsible for envenomation (toxins) and a few others (e.g., antimicrobials), while enzymes have been overlooked. In this work, a comprehensive study on enzyme diversity in scorpion venoms was performed by transcriptomic and proteomic techniques. Enzymes of 63 different EC types were found, belonging to 330 orthogroups. Of them, 24 ECs conform the scorpion venom enzymatic core, since they were determined to be present in all the studied scorpion species. Transferases and lyases are reported for the first time. Novel enzymes, which can play different roles in the venom, including direct toxicity, as venom spreading factors, activators of venom components, venom preservatives, or in prey pre-digestion, were described and annotated. The expression profile for transcripts coding for venom enzymes was analyzed, and shown to be similar among the studied species, while being significantly different from their expression pattern outside the telson.

Venom of Viperidae: A Perspective of its Antibacterial and Antitumor Potential

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The emergence of multi-drug resistant bacteria and limitations on cancer treatment represent two important challenges in modern medicine. Biological compounds have been explored with a particular focus on venoms. Although they can be lethal or cause considerable damage to humans, venom is also a source rich in components with high therapeutic potential.

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Viperidae family is one of the most emblematic venomous snake families and several studies highlighted the antibacterial and antitumor potential of viper toxins. According to the literature, these activities are mainly associated to five protein families - svLAAO, Disintegrins, PLA2, SVMPs and C-type lectins- that act through different mechanisms leading to the inhibition of the growth of bacteria, as well as, cytotoxic effects and inhibition of metastasis process. In this review, we provide an overview of the venom toxins produced by species belonging to the Viperidae family, exploring their roles during the envenoming and their pharmacological properties, in order to demonstrate its antibacterial and antitumor potential.

Application of Hemocoagulase Bothrops Atrox in the submucosal injection for endoscopic submucosal dissection: a preliminary trial

OBJECTIVE

This study aimed to evaluate the efficacy and safety of using Hemocoagulase Bothrops Atrox in the submucosal injection solution for endoscopic submucosal dissection (ESD).

METHODS

A total of 120 patients with superficial neoplastic lesions of the esophagus, stomach, and colon receiving ESD were randomly divided into two groups: The epinephrine group used epinephrine-containing submucosal fluid cushion for ESD, while the hemocoagulase group used Hemocoagulase Bothrops Atrox-containing submucosal fluid cushion for ESD. The preoperative, intraoperative, and postoperative clinical parameters and postoperative adverse events of the two groups were recorded, and comparative analysis within and between groups was performed.

RESULTS

There was no significant difference in the demographic and clinical characteristics between the hemocoagulase and epinephrine group (all P > 0.05). ESD surgery was completed in all patients. The hemocoagulase group had significantly shorter surgery time (P = 0.003) and less number of intraoperative bleeding (P = 0.010) than the epinephrine group. However, there was no significant difference in the incidences of postoperative delayed hemorrhage, and adverse events between the two groups (all P > 0.05). Multivariate linear regression demonstrated that the epinephrine group had significantly more number of intraoperative bleeding (B: 0.98, 95% confidence interval: 0.04-1.93) as compared with the hemocoagulase group.

CONCLUSION

Compared with epinephrine, using Hemocoagulase Bothrops Atrox in the submucosal injection for ESD surgery can significantly reduce the number of intraoperative bleeding, shorten the operation time, and did not elevate the incidence of adverse events.

LIMITED PROTEOLYSIS OF FIBRINOGEN BY PROTEASE OF Gloydius halys halys SNAKE VENOM

Aim. One of the approaches for studying structure and functions of proteins is their limited proteolysis. Proteolytic fragments of macromolecules can preserve the biological activity and can be used for the study of their structural and functional peculiarities. Thus, the characterization of new proteolytic enzymes and determination of the specificity of their action can be of interest for exploration. In the present work, we focused on the action of protease from the venom of Gloydius halys halys on fibrinogen, the crucial protein of blood coagulation system. Methods. Products of fibrinogen hydrolysis by protease from the venom of G. halys halys were studied by SDS-PAGE electrophoresis and western-blot analysis using monoclonal antibodies ІІ-5 Сand 1-5A targeted to 20‒78 and 549‒610 fragments of fibrinogen Aα-chain. Molecular weights of hydrolytic products were determined using MALDI-TOF analysis on Voyager DE PRO (USA). Sequence of hydrolytic products were predicted by «Peptide Mass Calculator» soft ware. Results. SDS-PAGE showed that protease from the venom of Gloydius halys halys initially cleaved Аα-chain of fibrinogen molecule. Western-blot analysis confirmed that this protease specifically cleaves off fragment of C-terminal parts of Аα-chain with apparent molecular weight of 22 kDa. Cleaved fragment was identified by MALDI-TOF analysis as the 21.1 kDa polypeptide. «Peptide Mass Calculator» predicted that such a fragment corresponded to Аα414-610 residue of fibrinogen molecule. Thus, we showed that studied protease cleaved peptide bond AαK413-L414 with the formation of stable partly hydrolyzed fibrinogen desAα414-610. Conclusions. The use of protease from the venom of Gloydius halys halys would allow obtaining the unique partly hydrolyzed fibrinogen des Aα 414‒610 that is suitable for the study of structure and functions of fibrinogen αС-regions.

Biological and Biochemical Characterization of Coronado Island Rattlesnake (Crotalus helleri caliginis) Venom and Antivenom Neutralization

The Baja California Peninsula has over 250 islands and islets with many endemic species. Among them, rattlesnakes are the most numerous but also one of the least studied groups. The study of island rattlesnake venom could guide us to a better understanding of evolutionary processes and the description of novel toxins. Crotalus helleri caliginis venom samples were analyzed to determine possible ontogenetic variation with SDS-PAGE in one and two dimensions and with RP-HPLC. Western Blot, ELISA, and amino-terminal sequencing were used to determine the main components of the venom. The biological and biochemical activities demonstrate the similarity of C. helleri caliginis venom to the continental species C. helleri helleri, with both having low proteolytic and phospholipase A₂ (PLA₂) activity but differing due to the absence of neurotoxin (crotoxin-like) in the insular species. The main components of the snake venom were metalloproteases, serine proteases, and crotamine, which was the most abundant toxin group (30–35% of full venom). The crotamine was isolated using size-exclusion chromatography where its functional effects were tested on mouse phrenic nerve–hemidiaphragm preparations in which a significant reduction in muscle twitch contractions were observed. The two Mexican antivenoms could neutralize the lethality of C. helleri caliginis venom but not the crotamine effects.

Snake Venoms in Diagnostic Hemostasis and Thrombosis

Snake venoms have evolved primarily to immobilize and kill prey, and consequently, they contain some of the most potent natural toxins. Part of that armory is a range of hemotoxic components that affect every area of hemostasis, which we have harnessed to great effect in the study and diagnosis of hemostatic disorders. The most widely used are those that affect coagulation, such as thrombin-like enzymes unaffected by heparin and direct thrombin inhibitors, which can help confirm or dispute their presence in plasma. The liquid gold of coagulation activators is Russell's viper venom, since it contains activators of factor X and factor V. It is used in a range of clotting-based assays, such as assessment of factor X and factor V deficiencies, protein C and protein S deficiencies, activated protein C resistance, and probably the most important test for lupus anticoagulants, the dilute Russell's viper venom time. Activators of prothrombin, such as oscutarin C from Coastal Taipan venom and ecarin from saw-scaled viper venom, are employed in prothrombin activity assays and lupus anticoagulant detection, and ecarin has a valuable role in quantitative assays of direct thrombin inhibitors. Snake venoms affecting primary hemostasis include botrocetin from the jararaca, which can be used to assay von Willebrand factor activity, and convulxin from the cascavel, which can be used to detect deficiency of the platelet collagen receptor, glycoprotein VI. This article takes the reader to every area of the diagnostic hemostasis laboratory to appreciate the myriad applications of snake venoms available in diagnostic practice.

Snake venom proteomics and antivenomics of two Sundaic lance-headed pit vipers: Trimeresurus wiroti (Malaysia) and Trimeresurus puniceus (Indonesia)

Envenomation by two medically important Sundaic pit vipers, Trimeresurus wiroti (Malaysia) and Trimeresurus puniceus (Indonesia), causes hemotoxic syndrome with a potentially fatal outcome. Research on the compositions and antigenicity of these pit viper venoms is however lacking, limiting our understanding of the pathophysiology and treatment of envenomation. This study investigated the venom proteomes of both species through a protein decomplexation strategy, applying C₁₈ reverse-phase high-performance liquid chromatography followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and protein identification through nano-electrospray ionization liquid chromatography-tandem mass spectrometry (nano-ESI-LCMS/MS) of trypsin-digested peptides. The venom antigenicity was profiled against the Thai Green Pit Viper Antivenom (GPVAV, a hetero-specific antivenom), using indirect enzyme-linked immunosorbent assay (ELISA). The venom proteomes of T. wiroti and T. puniceus consisted of 10 and 12 toxin families, respectively. The major proteins were of diverse snake venom serine proteases (19-30% of total venom proteins), snake venom metalloproteinases (17-26%), disintegrins (9-16%), phospholipases A₂ (8-28%) and C-type lectins (~8%). These were putative snake toxins implicated in hemorrhage and coagulopathy, consistent with clinical hemotoxicity. GPVAV showed strong immunorecognition toward high and medium molecular weight proteins (e.g., SVMP and PLA₂) in both venoms, while a lower binding activity was observed toward small proteins such as disintegrins. Conserved antigenicity in the major hemotoxins supported toxicity cross-neutralization by GPVAV and indicated that the immunorecognition of low molecular weight toxins may be optimized for improved binding efficacy. Taken together, the study provides insights into the pathophysiology and antivenom treatment of envenomation caused by T. wiroti and T. puniceus in the region.

Erythrocyte haemotoxicity profiling of snake venom toxins after nanofractionation

Snakebite is classified as a priority Neglected Tropical Disease by the World Health Organization. Understanding the pathology of individual snake venom toxins is of great importance when developing more effective snakebite therapies. Snake venoms may induce a range of pathologies, including haemolytic activity. Although snake venom-induced erythrocyte lysis is not the primary cause of mortality, haemolytic activity can greatly debilitate victims and contributes to systemic haemotoxicity. Current assays designed for studying haemolytic activity are not suitable for rapid screening of large numbers of toxic compounds. Consequently, in this study, a high-throughput haemolytic assay was developed that allows profiling of erythrocyte lysis, and was validated using venom from a number of medically important snake species (Calloselasma rhodostoma, Daboia russelii, Naja mossambica, Naja nigricollis and Naja pallida). The assay was developed in a format enabling direct integration into nanofractionation analytics, which involves liquid chromatographic separation of venom followed by high-resolution fractionation and subsequent bioassaying (and optional proteomics analysis), and parallel mass spectrometric detection. Analysis of the five snake venoms via this nanofractionation approach involving haemolytic assaying provided venom-cytotoxicity profiles and enabled identification of the toxins responsible for haemolytic activity. Our results show that the elapid snake venoms (Naja spp.) contained both direct and indirect lytic toxins, while the viperid venoms (C. rhodostoma and D. russelii) only showed indirect lytic activities, which required the addition of phospholipids to exert cytotoxicity on erythrocytes. The haemolytic venom toxins identified were mainly phospholipase A2s and cytotoxic three finger toxins. Finally, the applicability of this new analytical method was demonstrated using a conventional snakebite antivenom treatment and a small-molecule drug candidate to assess neutralisation of venom cytotoxins.

Small Angle X-ray Scattering, Molecular Modeling, and Chemometric Studies from a Thrombin-Like (Lmr-47) Enzyme of Lachesis m. rhombeata Venom

INTRODUCTION

Snakebite envenomation is considered a neglected tropical disease, and SVTLEs critical elements are involved in serious coagulopathies that occur on envenoming. Although some enzymes of this group have been structurally investigated, it is essential to characterize other proteins to better understand their unique properties such as the Lachesis muta rhombeata 47 kDa (Lmr-47) venom serine protease.

METHODS

The structure of Lmr-47 was studied in solution, using SAXS, DLS, CD, and in silico by homology modeling. Molecular docking experiments simulated 21 competitive inhibitors.

RESULTS

At pH 8.0, Lmr-47 has an Rg of 34.5 ± 0.6 Å, Dmax of 130 Å, and SR of 50 Å, according to DLS data. Kratky plot analysis indicates a rigid shape at pH 8.0. Conversely, the pH variation does not change the center of mass's intrinsic fluorescence, possibly indicating the absence of fluorescent amino acids in the regions affected by pH variation. CD experiments show a substantially random coiled secondary structure not affected by pH. The low-resolution model of Lmr-47 presented a prolate elongated shape at pH 8.0. Using the 3D structure obtained by molecular modeling, docking experiments identified five good and three suitable competitive inhibitors.

CONCLUSION

Together, our work provided insights into the structure of the Lmr-47 and identified inhibitors that may enhance our understanding of thrombin-like family proteins.

Slounase, a Batroxobin Containing Activated Factor X Effectively Enhances Hemostatic Clot Formation and Reducing Bleeding in Hypocoagulant Conditions in Mice

Uncontrolled bleeding associated with trauma and surgery is the leading cause of preventable death. Batroxobin, a snake venom-derived thrombin-like serine protease, has been shown to clot fibrinogen by cleaving fibrinopeptide A in a manner distinctly different from thrombin, even in the presence of heparin. The biochemical properties of batroxobin and its effect on coagulation have been well characterized in vitro. However, the efficacy of batroxobin on hemostatic clot formation in vivo is not well studied due to the lack of reliable in vivo hemostasis models. Here, we studied the efficacy of batroxobin and slounase, a batroxobin containing activated factor X, on hemostatic clot composition and bleeding using intravital microcopy laser ablation hemostasis models in micro and macro vessels and liver puncture hemostasis models in normal and heparin-induced hypocoagulant mice. We found that prophylactic treatment in wild-type mice with batroxobin, slounase and activated factor X significantly enhanced platelet-rich fibrin clot formation following vascular injury. In heparin-treated mice, batroxobin treatment resulted in detectable fibrin formation and a modest increase in hemostatic clot size, while activated factor X had no effect. In contrast, slounase treatment significantly enhanced both platelet recruitment and fibrin formation, forming a stable clot and shortening bleeding time and blood loss in wild-type and heparin-treated hypocoagulant mice. Our data demonstrate that, while batroxobin enhances fibrin formation, slounase was able to enhance hemostasis in normal mice and restore hemostasis in hypocoagulant conditions via the enhancement of fibrin formation and platelet activation, indicating that slounase is more effective in controlling hemorrhage.

Remarkable intrapopulation venom variability in the monocellate cobra (Naja kaouthia) unveils neglected aspects of India's snakebite problem

Interpopulation venom variation has been widely documented in snakes across large geographical distances. This variability is known to markedly influence the effectiveness of snakebite therapy, as antivenoms manufactured against one population may not be effective against others. In contrast, the extent of intrapopulation venom variability, especially at finer geographical scales, remains largely uninvestigated. Moreover, given the historical focus on the 'big four' Indian snakes, our understanding of venom variation in medically important yet neglected snakes, such as the monocellate cobra (Naja kaouthia), remains unclear. To address this shortcoming, we investigated N. kaouthia venoms sampled across a small spatial scale (<50 km) in Eastern India. An interdisciplinary approach employed in this study unveiled considerable intrapopulation differences in the venom proteomic composition, pharmacological and biochemical activities, and toxicity profiles. Documentation of stark differences in venoms at such a finer geographical scale, despite the influence of similar ecological and environmental conditions, is intriguing. Furthermore, evaluation of in vitro and in vivo venom recognition and neutralisation potential of Indian polyvalent 'big four' antivenoms and Thai monovalent N. kaouthia antivenom revealed concerning deficiencies. These results highlight the negative impact of phylogenetic divergence and intrapopulation snake venom variation on the effectiveness of conventional antivenom therapy. SIGNIFICANCE: In contrast to our understanding of snake venom variation across large distances, which is theorised to be shaped by disparities in ecology and environment, intrapopulation variation at finer geographic scales remains scarcely investigated. Assessment of intrapopulation venom variability in Naja kaouthia at a small spatial scale (<50 km) in Eastern India unravelled considerable differences in venom compositions, activities and potencies. While the influence of subtle differences in prey preference and local adaptations cannot be ruled out, these findings, perhaps, also emphasise the role of accelerated molecular evolutionary regimes that rapidly introduce variations in evolutionarily younger lineages, such as advanced snakes. The inability of 'big four' Indian antivenoms and Thai N. kaouthia monovalent antivenom in countering these variations highlights the importance of phylogenetic considerations for the development of efficacious snakebite therapy. Thus, we provide valuable insights into the venoms of one of the most medically important yet neglected Indian snakes.

Massive cutaneous complications due to snakebite: A case report and literature review

Wound infections due to snake bites such as cellulitis and necrotizing fasciitis, although not common, are seen in snake bites and if left untreated can cause serious complications.

Biogeographic venom variation in Russell's viper (Daboia russelii) and the preclinical inefficacy of antivenom therapy in snakebite hotspots

BACKGROUND

Snakebite in India results in over 58,000 fatalities and a vast number of morbidities annually. The majority of these clinically severe envenomings are attributed to Russell's viper (Daboia russelii), which has a near pan-India distribution. Unfortunately, despite its medical significance, the influence of biogeography on the composition and potency of venom from disparate D. russelii populations, and the repercussions of venom variation on the neutralisation efficacy of marketed Indian antivenoms, remain elusive.

METHODS

Here, we employ an integrative approach comprising proteomic characterisation, biochemical analyses, pharmacological assessment, and venom toxicity profiling to elucidate the influence of varying ecology and environment on the pan-Indian populations of D. russelii. We then conducted in vitro venom recognition experiments and in vivo neutralisation assays to evaluate the efficacy of the commercial Indian antivenoms against the geographically disparate D. russelii populations.

FINDINGS

We reveal significant intraspecific variation in the composition, biochemical and pharmacological activities and potencies of D. russelii venoms sourced from five distinct biogeographic zones across India. Contrary to our understanding of the consequences of venom variation on the effectiveness of snakebite therapy, commercial antivenom exhibited surprisingly similar neutralisation potencies against the majority of the investigated populations, with the exception of low preclinical efficacy against the semi-arid population from northern India. However, the ability of Indian antivenoms to counter the severe morbid effects of Daboia envenoming remains to be evaluated.

CONCLUSION

The concerning lack of antivenom efficacy against the north Indian population of D. russelii, as well as against two other 'big four' snake species in nearby locations, underscores the pressing need to develop pan-India effective antivenoms with improved efficacy in high snakebite burden locales.

Biogeographical venom variation in the Indian spectacled cobra (Naja naja) underscores the pressing need for pan-India efficacious snakebite therapy

Background

Snake venom composition is dictated by various ecological and environmental factors, and can exhibit dramatic variation across geographically disparate populations of the same species. This molecular diversity can undermine the efficacy of snakebite treatments, as antivenoms produced against venom from one population may fail to neutralise others. India is the world’s snakebite hotspot, with 58,000 fatalities and 140,000 morbidities occurring annually. Spectacled cobra (Naja naja) and Russell’s viper (Daboia russelii) are known to cause the majority of these envenomations, in part due to their near country-wide distributions. However, the impact of differing ecologies and environment on their venom compositions has not been comprehensively studied.

Methods

Here, we used a multi-disciplinary approach consisting of venom proteomics, biochemical and pharmacological analyses, and in vivo research to comparatively analyse N. naja venoms across a broad region (>6000 km; seven populations) covering India’s six distinct biogeographical zones.

Findings

By generating the most comprehensive pan-Indian proteomic and toxicity profiles to date, we unveil considerable differences in the composition, pharmacological effects and potencies of geographically-distinct venoms from this species and, through the use of immunological assays and preclinical experiments, demonstrate alarming repercussions on antivenom therapy. We find that commercially-available antivenom fails to effectively neutralise envenomations by the pan-Indian populations of N. naja, including a complete lack of neutralisation against the desert Naja population.

Conclusion

Our findings highlight the significant influence of ecology and environment on snake venom composition and potency, and stress the pressing need to innovate pan-India effective antivenoms to safeguard the lives, limbs and livelihoods of the country’s 200,000 annual snakebite victims.

Annually, India is burdened by the highest number of snake envenomations across the globe, with over 58,000 fatalities and three times the number of morbidities, predominantly affecting the rural agrarian communities. The spectacled cobra (Naja naja) and Russell’s viper (Daboia russelii) are responsible for the vast majority of envenomations in the country, in part, due to their near country-wide distributions. In this study, we unveil the astounding differences in venom composition of N. naja from six different biogeographical zones across the country (>6000 km). We provide a comprehensive account of their disparate venom proteomic profiles, biochemical and pharmacological effects, and the associated potencies. Our study uncovers alarming differences in the efficacy of the marketed polyvalent antivenoms in neutralising these venoms, thereby, emphasising the pressing need to develop dose-efficacious and pan-India effective antivenoms for the treatment of snakebites in the country. This study also highlights the significant influence of ecology and diverse environments on the venom variability, insinuating the necessity for innovating cost-effective and pan-India efficacious solutions to safeguard the lives, limbs and livelihoods of India’s two hundred thousand annual snakebite victims.

Bothrops atrox from Ecuadorian Amazon: Initial analyses of venoms from individuals

Bothrops atrox is the most clinically relevant snake species within the Amazon region, which includes Ecuadorian territories. It comprises a large distribution, which could contribute to the genetic and venomic variation identified in the species. The high variability and protein isoform diversity of its venom are of medical interest, since it can influence the clinical manifestations caused by envenomation and its treatment. However, in Ecuador there is insufficient information on the diversity of venomic phenotypes, even of relevant species such as B. atrox. Here, we characterized the biochemical and toxicological profiles of the venom of six B. atrox individuals from the Ecuadorian Amazon. Differences in catalytic activities of toxins, elution profiles in liquid chromatography, electrophoretic patterns, and toxic effects among the analyzed samples were identified. Nonetheless, in the preclinical testing of antivenom, two samples from Mera (Pastaza) required a higher dose to achieve total neutralization of lethality and hemorrhage. Taken together, these data highlight the importance of analyzing individual venoms in studies focused on the outcomes of envenoming.

The anti-rabies activity of Caspian cobra venom

Rabies is acute encephalitis that continuously kills thousands of people annually. There is no clinical cure for rabies so far and its prevention is limited to sero-vaccinations based on standard WHO protocols. Certain compounds such as snake venoms contain active biological components with tendency toward acetylcholine receptors and ion channels at the cell surface. These compounds then are able to reduce aggregation of the virus in neuromuscular junction that may lead to inhibit the virus activity. In this study we worked on cytotoxicity and antiviral activity effects of Naja naja oxiana (Iranian Caspian cobra) snake venom components, on Rabies Lyssavirus (Rabies virus; RABV) infected mammalian cells. The concentration of 25 μg/ml F5 fraction separated by FPLC showed minor toxicity on BHK-21 cells by MTT test and high antiviral activity against infected cells by FAT assay. Further studies on F5 fractionation by HPLC showed that the proliferation of infected BHK-21 cells by rabies virus CVS-11 strain was decreased up to 80% by using 20 μg/ml P5 peak, after 48 h. We assume that P5-peptide (MW < 10 kDa) enters the cells through AChR receptors same as rabies virus without competition in binding to the cell receptors and is able to reduce the virus proliferation on post viral infection phase. This is the first report of the presence of an anti-rabies effect of Caspian cobra snake venom component. As per our results the P5 peak is a suitable candidate for further studies as a new agent to reduce CVS-11 rabies virus.

Flaxseed Cysteine Protease Exhibits Strong Anticoagulant, Antiplatelet, and Clot-Dissolving Properties

In this study, we purified and characterized flaxseed cysteine protease (FSCP) with strong anticoagulant, antiplatelet, and clot-dissolving properties. The enzyme was purified to homogeneity by a combination of gel permeation and ion-exchange column chromatography techniques. The purity of the enzyme was evaluated by SDS-PAGE, RP-HPLC, and MALDI-TOF. FSCP was observed as a single band of approximately 160 kDa in SDS-PAGE under reducing and non-reducing conditions. The exact molecular mass of FSCP was found to be 168 kDa by MALDI-TOF spectrometry. The CD spectra of FSCP revealed the presence of 25.6% helices, 25.8% turns, and 48% random coils with no beta-sheet structures. FSCP hydrolyzed both casein and gelatin with a specific activity of 3.5 and 4.2 unit/mg min respectively. The proteolytic activity of FSCP was completely abolished by iodoacetic acid (IAA), suggesting FSCP is a cysteine protease. The pH optimum for the proteolytic activity of FSCP was pH 6.0; the temperature optimum was 30°C. FSCP exhibited strong anticoagulant effect in both platelet-rich plasma (PRP) and platelet-poor plasma (PPP) by extending the clotting time from 222 to 1100 s and from 256 to 1210 s, respectively. FSCP degraded human fibrinogen and fibrin clots. The products of fibrinogen degradation by thrombin and FSCP were different. Furthermore, FSCP inhibited aggregation of washed platelets triggered by ADP, epinephrine, thrombin, collagen, arachidonic acid, and platelet activating factor (PAF). FSCP was found to be nontoxic as it did not damage the membrane of red blood cells (RBCs) and did not induce hemorrhage and edema in experimental mice.

Peptide-based topical agents and intravenous hemostat for rapid hemostasis

Traumatic coagulopathy due to severe external injury and internal hemorrhage is life-threatening to accident victims and soldiers on the battlefield, causing considerable number of deaths worldwide. Patients with inherited bleeding disorders (such as haemophilia, von Willebrand disease, inherited qualitative platelet defects, and afibrinogenemia) also contribute to the vast number of deaths due to abnormal bleeding, and these patients are difficult to handle during surgery. Platelets and different plasma proteins play an essential role in blood coagulation and in the maintenance of the body's hemostatic balance. The improper function or deficiency of these factors cause abnormal bleeding. To address such bleeding disorders, external clotting agents (such as extracellular protein-inspired natural and synthetic peptide-based sealants and peptide-functionalized polymer/liposome-based sealants) have been developed by different groups of researchers. The primary focus of this review is to provide molecular insights into the existing biologically inspired peptide-based sealants, highlighting the advantages and limitations of such reported designed sealants to handle blood clotting, and also provide insights into the design of improved next-generation surgical sealants.

Bedside Coagulation Tests in Diagnosing Venom-Induced Consumption Coagulopathy in Snakebite

Venom-induced consumption coagulopathy is the most important systemic effect of snake envenoming. Coagulation tests are helpful to accurately and promptly diagnose venom-induced consumption coagulopathy and administer antivenom, which is the only specific treatment available. However, bedside clotting tests play a major role in diagnosing coagulopathy in low-income settings, where the majority of snakebites occur. We conducted a literature search in MEDLINE^® from 1946 to 30 November 2019, looking for research articles describing clinical studies on bedside coagulation tests in snakebite patients. Out of 442 articles identified, 147 articles describing bedside clotting assays were included in the review. Three main bedside clotting tests were identified, namely the Lee–White clotting test, 20-min whole blood clotting time and venous clotting time. Although the original Lee–White clotting test has never been validated for snake envenoming, a recently validated version has been used in some South American countries. The 20-min whole blood clotting time test is the most commonly used test in a wide range of settings and for taxonomically diverse snake species. Venous clotting time is almost exclusively used in Thailand. Many validation studies have methodological limitations, including small sample size, lack of case-authentication, the inclusion of a heterogeneous mix of snakebites and inappropriate uses of gold standard tests. The observation times for bedside clotting tests were arbitrary, without proper scientific justification. Future research needs to focus on improving the existing 20-min whole blood clotting test, and also on looking for alternative bedside coagulation tests which are cheap, reliable and quicker.

Bleeding Disorders in Bothrops atrox Envenomations in the Brazilian Amazon: Participation of Hemostatic Factors and the Impact of Tissue Factor

Bleeding is a common hemostatic disorder that occurs in Bothrops envenomations. We evaluated the changes in coagulation, fibrinolysis components, and platelets in Bothrops atrox envenomations with bleeding. This is an observational study with B. atrox snakebite patients (n = 100) treated in Manaus, Brazilian Amazon. Bleeding was recorded on admission and during hospitalization. We found that the platelet count in our patients presented a weak correlation to tissue factor, factor II, and plasminogen. Tissue factor presented weak correlation to factor V, II, D-dimer, plasminogen, alpha 2-antiplasmin, and moderate correlation to fibrinogen and fibrin/fibrinogen degradation product (FDP). Patients with systemic bleeding (n = 20) presented low levels of factor V, II, fibrinogen, plasminogen, and alpha 2-antiplasmin, and high levels of tissue factor and FDP compared to those without bleeding. Patients with only local bleeding (n = 41) and without bleeding showed similar levels of hemostatic factors. Thrombocytopenia was observed mainly in patients with systemic bleeding and increased levels of serum venom. No association was found between venom levels and systemic bleeding, or between venom levels and clinical severity of envenomation. This is the first report that shows the participation of the extrinsic coagulation pathway in the consumption coagulopathy of B. atrox envenomations with systemic bleeding due to tissue factor release.

Neutralizing Effects of Small Molecule Inhibitors and Metal Chelators on Coagulopathic Viperinae Snake Venom Toxins

Animal-derived antivenoms are the only specific therapies currently available for the treatment of snake envenoming, but these products have a number of limitations associated with their efficacy, safety and affordability for use in tropical snakebite victims. Small molecule drugs and drug candidates are regarded as promising alternatives for filling the critical therapeutic gap between snake envenoming and effective treatment. In this study, by using an advanced analytical technique that combines chromatography, mass spectrometry and bioassaying, we investigated the effect of several small molecule inhibitors that target phospholipase A2 (varespladib) and snake venom metalloproteinase (marimastat, dimercaprol and DMPS) toxin families on inhibiting the activities of coagulopathic toxins found in Viperinae snake venoms. The venoms of Echis carinatus, Echis ocellatus, Daboia russelii and Bitis arietans, which are known for their potent haemotoxicities, were fractionated in high resolution onto 384-well plates using liquid chromatography followed by coagulopathic bioassaying of the obtained fractions. Bioassay activities were correlated to parallel recorded mass spectrometric and proteomics data to assign the venom toxins responsible for coagulopathic activity and assess which of these toxins could be neutralized by the inhibitors under investigation. Our results showed that the phospholipase A2-inhibitor varespladib neutralized the vast majority of anticoagulation activities found across all of the tested snake venoms. Of the snake venom metalloproteinase inhibitors, marimastat demonstrated impressive neutralization of the procoagulation activities detected in all of the tested venoms, whereas dimercaprol and DMPS could only partially neutralize these activities at the doses tested. Our results provide additional support for the concept that combinations of small molecules, particularly the combination of varespladib with marimastat, serve as a drug-repurposing opportunity to develop new broad-spectrum inhibitor-based therapies for snakebite envenoming.

Interspecific and intraspecific venom enzymatic variation among cobras (Naja sp. and Ophiophagus hannah)

The genera Ophiophagus and Naja comprise part of a clade of snakes referred to as cobras, dangerously venomous front-fanged snakes in the family Elapidae responsible for significant human mortality and morbidity throughout Asia and Africa. We evaluated venom enzyme variation for eleven cobra species and three N. kaouthia populations using SDS-PAGE venom fingerprinting and numerous enzyme assays. Acetylcholinesterase and PLA₂ activities were the most variable between species, and PLA₂ activity was significantly different between Malaysian and Thailand N. kaouthia populations. Venom metalloproteinase activity was low and significantly different among most species, but levels were identical for N. kaouthia populations; minor variation in venom L-amino acid oxidase and phosphodiesterase activities were seen between cobra species. Naja siamensis venom lacked the α-fibrinogenolytic activity common to other cobra venoms. In addition, venom from N. siamensis had no detectable metalloproteinase activity and exhibited an SDS-PAGE profile with reduced abundance of higher mass proteins. Venom profiles from spitting cobras (N. siamensis, N. pallida, and N. mossambica) exhibited similar reductions in higher mass proteins, suggesting the evolution of venoms of reduced complexity and decreased enzymatic activity among spitting cobras. Generally, the venom proteomes of cobras show highly abundant three-finger toxin diversity, followed by large quantities of PLA₂s. However, PLA₂ bands and activity were very reduced for N. haje, N. annulifera and N. nivea. Venom compositionalenzy analysis provides insight into the evolution, diversification and distribution of different venom phenotypes that complements venomic data, and this information is critical for the development of effective antivenoms and snakebite treatment.

Proteomic and toxinological characterization of Peruvian pitviper Bothrops brazili ("jergón shushupe"), venom

Bothrops brazili is a pitviper from Amazonian region, responsible for many accidents in Peru. Despite its relevance, its venom has not been extensively characterized. In the present work, Bothrops brazili venom (BbV) components were analyzed by RP-HPLC, SDS-PAGE and MALDI-TOF/TOF. Approximately 37 proteins were identified, belonging to 7 families. Snake venom metalloproteinases (SVMPs) were the most abundant proteins of the venom (33.05%), followed by snake venom serine proteinases (SVSPs, 26.11%), phospholipases A₂ (PLA₂, 25.57%), snake C-type lectins (CTLs, 9.61%), L-aminoacid oxidase (LAAO, 3.80%), cystein-rich secretory proteins (CRISP, 1.67%) and Bradykinin-potentiating peptide (BPP, 0.20%). In vitro enzymatic activities of BbV showed high levels of SVMP activity and reduced Hyal activity in comparison with other bothropic venoms. Furthermore, BbV reduced VERO cells viability. ELISA and Western Blotting showed that both Peruvian and Brazilian bothropic antivenoms were able to recognize BbV components. This work provides an overview of BbV venom content and indicates a potential efficiency of Peruvian and Brazilian antivenoms to treat accidents with this species.

Coagulation factor activity patterns of venom-induced consumption coagulopathy in naturally occurring tiger snake (Notechis scutatus) envenomed dogs treated with antivenom

BACKGROUND

Venom-induced consumption coagulopathy (VICC) from tiger snake (Notechis scutatus) envenomation results in a dose-dependent coagulopathy that is detectable on coagulometry. However, individual coagulation factor activities in dogs with tiger snake envenomation have not been determined. This study aimed to characterise VICC and the time course of recovery in tiger snake envenomed dogs and to investigate an association between tiger snake venom (TSV) concentrations and factor activity.

METHODS

This was a prospective, observational, cohort study. The study cohort was 11 dogs of any age, breed, sex, body weight >10 kg, confirmed serum TSV on ELISA and treated with antivenom. Blood was collected at enrolment before antivenom administration, then at 3, 12 and 24 h after antivenom administration. Tiger snake venom concentrations were detected with a sandwich ELISA. Fibrinogen was measured using a modified Clauss method, and coagulation factors (F) II, V, VII, VIII and X were measured with factor-deficient human plasma using a modified prothrombin (PT) and activated partial thromboplastin (aPTT) method. Linear mixed models, with multiple imputations of censored observations, were used to determine the effect of time and TSV concentration on the coagulation times and factor activity. This cohort was compared to 20 healthy controls.

RESULTS

At enrolment, there were severe deficiencies in fibrinogen, FV and FVIII, with predicted recovery by 10.86, 11.75 and 13.14 h after antivenom, respectively. There were modest deficiencies in FX and FII, with predicted recovery by 20.57 and 32.49 h after antivenom, respectively. No changes were detected in FVII. Prothrombin time and aPTT were markedly prolonged with predicted recovery of aPTT by 12.58 h. Higher serum TSV concentrations were associated with greater deficiencies in FII, FV and FVIII, and greater prolongations in coagulation times. The median (range) serum TSV concentration was 57 (6-2295) ng/mL.

CONCLUSIONS

In tiger snake envenomed dogs, we detected a profound, TSV-concentration-related consumption of select coagulation factors, that rapidly recovered toward normal. These findings allowed further insight into tiger snake VICC in dogs.

Effect of Traditional Chinese Medicine on Long-Term Outcomes of Snakebite in Taiwan

Herein, we review the characteristics of the six predominant venomous snakes in Taiwan and the effects of traditional Chinese medicine on the long-term outcomes of snakebite venom. We electronically searched databases, including PubMed, ClinicalKey, China National Knowledge Infrastructure, National Digital Library of Theses and Dissertations in Taiwan, and Airiti Library, from their inception to November 2019 by using the following Medical Subject Headings' keywords: snakebite, long-term, chronic, Chinese medicine, CAM, herb, and Taiwan. The most common long-term effects of snakebite envenomation include "migraine-like syndrome", brain injuries caused by hypoxia or intracranial hemorrhage, and chronic kidney disease. In addition, hypopituitarism is also worth mentioning. Traditional Chinese medicine can potentially be used in a complementary or alternative treatment for these effects, but additional studies are needed.

Beyond the 'big four': Venom profiling of the medically important yet neglected Indian snakes reveals disturbing antivenom deficiencies

Background

Snakebite in India causes the highest annual rates of death (46,000) and disability (140,000) than any other country. Antivenom is the mainstay treatment of snakebite, whose manufacturing protocols, in essence, have remained unchanged for over a century. In India, a polyvalent antivenom is produced for the treatment of envenomations from the so called ‘big four’ snakes: the spectacled cobra (Naja naja), common krait (Bungarus caeruleus), Russell’s viper (Daboia russelii), and saw-scaled viper (Echis carinatus). In addition to the ‘big four’, India is abode to many other species of venomous snakes that have the potential to inflict severe clinical or, even, lethal envenomations in their human bite victims. Unfortunately, specific antivenoms are not produced against these species and, instead, the ‘big four’ antivenom is routinely used for the treatment.

Methods

We characterized the venom compositions, biochemical and pharmacological activities and toxicity profiles (mouse model) of the major neglected yet medically important Indian snakes (E. c. sochureki, B. sindanus, B. fasciatus, and two populations of N. kaouthia) and their closest ‘big four’ congeners. By performing WHO recommended in vitro and in vivo preclinical assays, we evaluated the efficiencies of the commercially marketed Indian antivenoms in recognizing venoms and neutralizing envenomations by these neglected species.

Findings

As a consequence of dissimilar ecologies and diet, the medically important snakes investigated exhibited dramatic inter- and intraspecific differences in their venom profiles. Currently marketed antivenoms were found to exhibit poor dose efficacy and venom recognition potential against the ‘neglected many’. Premium Serums antivenom failed to neutralise bites from many of the neglected species and one of the ‘big four’ snakes (North Indian population of B. caeruleus).

Conclusions

This study unravels disturbing deficiencies in dose efficacy and neutralisation capabilities of the currently marketed Indian antivenoms, and emphasises the pressing need to develop region-specific snakebite therapy for the ‘neglected many’.

Snakebite is a ‘neglected tropical disease’ that majorly affects the rural populations in developing countries. India bears the brunt of snakebites with over 46,000 deaths and 140,000 disabilities, annually. A significant number of these bites are attributed to the widely distributed ‘big four’ snakes, namely spectacled cobra (Naja naja), common krait (Bungarus caeruleus), Russell’s viper (Daboia russelii), and saw-scaled viper (Echis carinatus). The commercial antivenoms marketed in India are only manufactured against these four species, while neglecting many other medically relevant snakes with restricted geographic distribution. Snakebite pathology is dependent on the venom composition of the population/species, which can, in turn, vary intra- and inter-specifically. Though this variation severely limits the cross-population/species antivenom efficacy, envenomations by the neglected snakes in India are treated with the ‘big four’ antivenom. Therefore, to unravel the underlying venom variability, we investigated venom proteomic, biochemical/pharmacological and toxicity profiles of the major neglected Indian snakes and their ‘big four’ relatives. To assess the effectiveness of the ‘big four’ antivenom in treating bites from these neglected snakes, we performed preclinical experiments, which revealed alarming inadequacies of the commercial antivenoms. Our findings accentuate the compelling necessity for the innovation of highly efficacious next-generation snakebite therapy in India.

Risk factor, monitoring, and treatment for snakebite induced coagulopathy: a multicenter retrospective study

Background

Snakebite can cause various complications, including coagulopathy. The clinical features of snakebite-associated coagulopathy differ from those of disseminated intravascular coagulation (DIC) caused by other diseases and its treatment is controversial.

Methods

We retrospectively reviewed the medical records of patients hospitalized for snakebite between January 2006 and September 2018.

Results

A total of 226 patients were hospitalized due to snakebite. Their median hospital stay was 4.0 days (interquartile range, 2.0 to 7.0 days). Five patients arrived at hospital with shock and one patient died. Twenty-one patients had overt DIC according to the International Society of Thrombosis and Hemostasis scoring system. Two patients developed major bleeding complications. Initial lower cholesterol level at presentation was associated with the development of overt DIC. International normalization ratio (INR) exceeding the laboratory’s measurement limit was recorded as late as 4 to 5 days after the bite. Higher antivenom doses (≥18,000 units) and transfusion of fresh frozen plasma (FFP) or cryoprecipitate did not affect prolonged INR duration or hospital stay in the overt DIC patients without bleeding.

Conclusions

Initial lower cholesterol level may be a risk factor for overt DIC following snakebite. Although patients lack apparent symptoms, the risk of coagulopathy should be assessed for at least 4 to 5 days following snakebite. Higher antivenom doses and transfusion of FFP or cryoprecipitate may be unbeneficial for coagulopathic patients without bleeding.

Atroxlysin-III, A Metalloproteinase from the Venom of the Peruvian Pit Viper Snake Bothrops atrox (Jergón) Induces Glycoprotein VI Shedding and Impairs Platelet Function

Atroxlysin-III (Atr-III) was purified from the venom of Bothrops atrox. This 56-kDa protein bears N-linked glycoconjugates and is a P-III hemorrhagic metalloproteinase. Its cDNA-deduced amino acid sequence reveals a multidomain structure including a proprotein, a metalloproteinase, a disintegrin-like and a cysteine-rich domain. Its identity with bothropasin and jararhagin from Bothrops jararaca is 97% and 95%, respectively. Its enzymatic activity is metal ion-dependent. The divalent cations, Mg²⁺ and Ca²⁺, enhance its activity, whereas excess Zn²⁺ inhibits it. Chemical modification of the Zn²⁺-complexing histidine residues within the active site by using diethylpyrocarbonate (DEPC) inactivates it. Atr-III degrades plasma fibronectin, type I-collagen, and mainly the α-chains of fibrinogen and fibrin. The von Willebrand factor (vWF) A1-domain, which harbors the binding site for GPIb, is not hydrolyzed. Platelets interact with collagen via receptors for collagen, glycoprotein VI (GPVI), and α2β1 integrin. Neither the α2β1 integrin nor its collagen-binding A-domain is fragmented by Atr-III. In contrast, Atr-III cleaves glycoprotein VI (GPVI) into a soluble ~55-kDa fragment (sGPVI). Thereby, it inhibits aggregation of platelets which had been stimulated by convulxin, a GPVI agonist. Selectively, Atr-III targets GPVI antagonistically and thus contributes to the antithrombotic effect of envenomation by Bothrops atrox.

Snake Venoms in Drug Discovery: Valuable Therapeutic Tools for Life Saving

Animal venoms are used as defense mechanisms or to immobilize and digest prey. In fact, venoms are complex mixtures of enzymatic and non-enzymatic components with specific pathophysiological functions. Peptide toxins isolated from animal venoms target mainly ion channels, membrane receptors and components of the hemostatic system with high selectivity and affinity. The present review shows an up-to-date survey on the pharmacology of snake-venom bioactive components and evaluates their therapeutic perspectives against a wide range of pathophysiological conditions. Snake venoms have also been used as medical tools for thousands of years especially in tradition Chinese medicine. Consequently, snake venoms can be considered as mini-drug libraries in which each drug is pharmacologically active. However, less than 0.01% of these toxins have been identified and characterized. For instance, Captopril^® (Enalapril), Integrilin^® (Eptifibatide) and Aggrastat^® (Tirofiban) are drugs based on snake venoms, which have been approved by the FDA. In addition to these approved drugs, many other snake venom components are now involved in preclinical or clinical trials for a variety of therapeutic applications. These examples show that snake venoms can be a valuable source of new principle components in drug discovery.

The extract from Agkistrodon halys venom protects against lipopolysaccharide (LPS)-induced myocardial injury

BACKGROUND

Snake venoms contain various bioactive constituents which possess potential therapeutic effects. The aim of this work was to investigate the effect of the extract from Agkistrodon halys venom on lipopolysaccharide (LPS)-induced myocardial injury.

METHODS

Thirty male Sprague-Dawley rats were randomly assigned to three groups (10 rats per group): control group, LPS group and LPS + extract group. Rats in control and the LPS groups were intravenously injected with sterile saline solution, and rats in the LPS + extract group with the extract. After 2 h, rats of the control group were intraperitoneally injected sterile saline solution, and rats in the LPS and the LPS + extract groups were treated with LPS (20 mg per kg body weight). Levels of creatine kinase (CK) and lactate dehydrogenase (LDH) in serum were determined. Anti-inflammation of the extract was analyzed via determination of TNF-α and IL-6 in serum, and expression of TNF-α, IL-6, COX-2 and p-ERK protein in hearts. Heme oxygenase-1 (HO-1) and p-NF-κB protein expression in hearts, superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in serum were used to evaluate the anti-oxidative properties of the extract.

RESULTS

Extract pretreatment significantly decreased the level of serum CK and LDH, reduced the generation of inflammatory cytokines such as TNF-α and IL-6, and also reduced serum level of MDA in the LPS + extract group compared with the LPS group. In addition, the extract increased SOD activity in serum, HO-1 protein expression in hearts, and decreased TNF-α, IL-6, COX-2, p-NF-κB and p-ERK1/2 protein expression.

CONCLUSION

Our results suggested that beneficial effect of this extract might be associated with an improved anti-oxidation and anti-inflammatory effect via downregulation of NF-κB/COX-2 signaling by activating HO-1/CO in hearts.

Structurally Robust and Functionally Highly Versatile-C-Type Lectin (-Related) Proteins in Snake Venoms

Snake venoms contain an astounding variety of different proteins. Among them are numerous C-type lectin family members, which are grouped into classical Ca²⁺- and sugar-binding lectins and the non-sugar-binding snake venom C-type lectin-related proteins (SV-CLRPs), also called snaclecs. Both groups share the robust C-type lectin domain (CTLD) fold but differ in a long loop, which either contributes to a sugar-binding site or is expanded into a loop-swapping heterodimerization domain between two CLRP subunits. Most C-type lectin (-related) proteins assemble in ordered supramolecular complexes with a high versatility of subunit numbers and geometric arrays. Similarly versatile is their ability to inhibit or block their target molecules as well as to agonistically stimulate or antagonistically blunt a cellular reaction triggered by their target receptor. By utilizing distinct interaction sites differentially, SV-CLRPs target a plethora of molecules, such as distinct coagulation factors and receptors of platelets and endothelial cells that are involved in hemostasis, thrombus formation, inflammation and hematogenous metastasis. Because of their robust structure and their high affinity towards their clinically relevant targets, SV-CLRPs are and will potentially be valuable prototypes to develop new diagnostic and therapeutic tools in medicine, provided that the molecular mechanisms underlying their versatility are disclosed.

Factors Associated with Systemic Bleeding in Bothrops Envenomation in a Tertiary Hospital in the Brazilian Amazon

Bothrops snakebites usually present systemic bleeding, and the clinical–epidemiological and laboratorial factors associated with the development of this manifestation are not well established. In this study, we assessed the prevalence of Bothrops snakebites with systemic bleeding reported at the Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, in Manaus, Amazonas State, Brazil, and the clinical–epidemiological and laboratorial factors associated with systemic bleeding. This is an observational, cross-sectional study carried out between August, 2013 and July, 2016. Patients who developed systemic bleeding on admission or during hospitalization were considered cases, and those with non-systemic bleeding were included in the control group. Systemic bleeding was observed in 63 (15.3%) of the 442 Bothrops snakebites evaluated. Bothrops snakebites mostly occurred in males (78.2%), in rural areas (89.0%) and in the age group of 11 to 30 years old (40.4%). It took most of the patients (59.8%) less than 3 h to receive medical assistance. Unclottable blood (AOR = 3.11 (95% CI = 1.53 to 6.31; p = 0.002)) and thrombocytopenia (AOR = 4.52 (95% CI = 2.03 to 10.09; p < 0.001)) on admission were independently associated with systemic bleeding during hospitalization. These hemostatic disorders on admission increase the chances of systemic bleeding during hospitalization. Prospective studies are needed to clarify the pathophysiology of systemic bleeding in Bothrops snakebites in the Amazon region.

Kn-Ba: a novel serine protease isolated from Bitis arietans snake venom with fibrinogenolytic and kinin-releasing activities

Background

Bitis arietans is a venomous snake found in sub-Saharan Africa and in parts of Morocco and Saudi Arabia. The envenomation is characterized by local and systemic reactions including pain, blistering, edema and tissue damage, besides hemostatic and cardiovascular disturbances, which can cause death or permanent disabilities in its victims. However, the action mechanisms that provoke these effects remain poorly understood, especially the activities of purified venom components. Therefore, in order to elucidate the molecular mechanisms that make the Bitis arietans venom so potent and harmful to human beings, this study reports the isolation and biochemical characterization of a snake venom serine protease (SVSP).

Methods

Solubilized venom was fractionated by molecular exclusion chromatography and the proteolytic activity was determined using fluorescent substrates. The peaks that showed serine protease activity were determined by blocking the proteolytic activity with site-directed inhibitors. In sequence, the fraction of interest was submitted to another cycle of molecular exclusion chromatography. The purified serine protease was identified by mass spectrometry and characterized biochemically and immunochemically.

Results

A serine protease of 33 kDa with fibrinogen-degrading and kinin-releasing activities was isolated, described, and designated herein as Kn-Ba. The experimental Butantan Institute antivenom produced against Bitis arietans venom inhibited the Kn-Ba activity.

Conclusions

The in vitro activities of Kn-Ba can be correlated with the capacity of the venom to provoke bleeding and clotting disorders as well as hypotension, which are common symptoms presented by envenomed victims. Obtaining satisfactory Kn-Ba inhibition through the experimental antivenom is important, given the WHO’s recommendation of immunotherapy in cases of human accidents with venomous snakes.

Electronic supplementary material

The online version of this article (10.1186/s40409-018-0176-5) contains supplementary material, which is available to authorized users.