C-type lectin-like proteins from snake venoms

Venom Composition of Neglected Bothropoid Snakes from the Amazon Rainforest: Ecological and Toxinological Implications

Snake venoms have evolved in several families of Caenophidae, and their toxins have been assumed to be biochemical weapons with a role as a trophic adaptation. However, it remains unclear how venom contributes to the success of venomous species for adaptation to different environments. Here we compared the venoms from Bothrocophias hyoprora, Bothrops taeniatus, Bothrops bilineatus smaragdinus, Bothrops brazili, and Bothrops atrox collected in the Amazon Rainforest, aiming to understand the ecological and toxinological consequences of venom composition. Transcriptomic and proteomic analyses indicated that the venoms presented the same toxin groups characteristic from bothropoids, but with distinct isoforms with variable qualitative and quantitative abundances, contributing to distinct enzymatic and toxic effects. Despite the particularities of each venom, commercial Bothrops antivenom recognized the venom components and neutralized the lethality of all species. No clear features could be observed between venoms from arboreal and terrestrial habitats, nor in the dispersion of the species throughout the Amazon habitats, supporting the notion that venom composition may not shape the ecological or toxinological characteristics of these snake species and that other factors influence their foraging or dispersal in different ecological niches.

Isolation and characterization of ZK002, a novel dual function snake venom protein from Deinagkistrodon acutus with anti-angiogenic and anti-inflammatory properties

Introduction: Pathological angiogenesis, the abnormal or excessive generation of blood vessels, plays an important role in many diseases including cancer, diabetic retinopathy, psoriasis, and arthritis. Additionally, increasing evidence supports the close linkage between angiogenesis and inflammation. Snake venoms are a rich natural source of biologically active molecules and carry rich potential for the discovery of anti-angiogenic and anti-inflammatory modulators. Methods: Here, we isolated and purified a novel protein, ZK002, from the venom of the snake Deinagkistrodon acutus, and investigated its anti-angiogenic and anti-inflammatory activities and mechanisms. Results: ZK002 was identified as a 30 kDa heterodimeric protein of α and β chains, which exhibited anti-angiogenic activity in various in vitro assays. Mechanistically, ZK002 inhibited activation of VEGF signaling and related mediators including eNOS, p38, LIMK, and HSP27. ZK002 also upregulated the metalloproteinase inhibitor TIMP3 and inhibited components of the VEGF-induced signaling cascade, PPP3R2 and SH2D2A. The anti-angiogenic activity of ZK002 was confirmed in multiple in vivo models. ZK002 could also inhibit the in vitro expression of pro-inflammatory cytokines, as well as in vivo inflammation in the carrageenin-induced edema rat model. Conclusion: Our findings highlight the potential for further development of ZK002 as a dual function therapeutic against diseases with involvement of pathogenic angiogenesis and chronic inflammation.

Pulmonary involvement from animal toxins: the cellular mechanisms

Venomous animals and their venom have always been of human interest because, despite species differences, coevolution has made them capable of targeting key physiological components of our bodies. Respiratory failure from lung injury is one of the serious consequences of envenomation, and the underlying mechanisms are rarely discussed. This review aims to demonstrate how toxins affect the pulmonary system through various biological pathways. Herein, we propose the common underlying cellular mechanisms of toxin-induced lung injury: interference with normal cell function and integrity, disruption of normal vascular function, and provocation of excessive inflammation. Viperid snakebites are the leading cause of envenomation-induced lung injury, followed by other terrestrial venomous animals such as scorpions, spiders, and centipedes. Marine species, particularly jellyfish, can also inflict such injury. Common pulmonary manifestations include pulmonary edema, pulmonary hemorrhage, and exudative infiltration. Severe envenomation can result in acute respiratory distress syndrome. Pulmonary involvement suggests severe envenomation, thus recognizing these mechanisms and manifestations can aid physicians in providing appropriate treatment.

De Novo Venom Gland Transcriptome Assembly and Characterization for Calloselasma rhodostoma (Kuhl, 1824), the Malayan Pit Viper from Malaysia: Unravelling Toxin Gene Diversity in a Medically Important Basal Crotaline

In Southeast Asia, the Malayan Pit Viper (Calloselasma rhodostoma) is a venomous snake species of medical importance and bioprospecting potential. To unveil the diversity of its toxin genes, this study de novo assembled and analyzed the venom gland transcriptome of C. rhodostoma from Malaysia. The expression of toxin genes dominates the gland transcriptome by 53.78% of total transcript abundance (based on overall FPKM, Fragments Per Kilobase Million), in which 92 non-redundant transcripts belonging to 16 toxin families were identified. Snake venom metalloproteinase (SVMP, PI > PII > PIII) is the most dominant family (37.84% of all toxin FPKM), followed by phospholipase A₂ (29.02%), bradykinin/angiotensin-converting enzyme inhibitor-C-type natriuretic peptide (16.30%), C-type lectin (CTL, 10.01%), snake venom serine protease (SVSP, 2.81%), L-amino acid oxidase (2.25%), and others (1.78%). The expressions of SVMP, CTL, and SVSP correlate with hemorrhagic, anti-platelet, and coagulopathic effects in envenoming. The SVMP metalloproteinase domains encode hemorrhagins (kistomin and rhodostoxin), while disintegrin (rhodostomin from P-II) acts by inhibiting platelet aggregation. CTL gene homologues uncovered include rhodocytin (platelet aggregators) and rhodocetin (platelet inhibitors), which contribute to thrombocytopenia and platelet dysfunction. The major SVSP is a thrombin-like enzyme (an ancrod homolog) responsible for defibrination in consumptive coagulopathy. The findings provide insight into the venom complexity of C. rhodostoma and the pathophysiology of envenoming.

Intracellular Zinc Trafficking during Crotalus atrox Venom Wound Development

In this study, we examined zinc trafficking in human umbilical vein endothelial cells (HUVEC) stimulated with Crotalus atrox (CA venom) snake venom. We utilized MTS cytotoxicity assays to monitor the cytotoxic range of CA venom. HUVEC monolayers stimulated with 10 µg/mL CA venom for 3 h displayed cellular retraction, which coincided with 53.0 ± 6.5 percent viability. In contrast, venom concentrations of 100 µg/mL produced a complete disruption of cellular adherence and viability decreased to 36.6 ± 1.0. The zinc probe Fluozin-3AM was used to detect intracellular zinc in non-stimulated controls, HUVEC stimulated with 10 µg/mL CA venom or HUVEC preincubated with TPEN for 2 h then stimulated with 10 µg/mL CA venom. Fluorescent intensity analysis returned values of 1434.3 ± 197.4 for CA venom demonstrating an increase of about two orders of magnitude in labile zinc compared to non-stimulated controls. Endothelial response to CA venom induced a 96.1 ± 3.0- and 4.4 ± 0.41-fold increase in metallothionein 1X (MT1X) and metallothionein 2A (MT2A) gene expression. Zinc chelation during CA venom stimulation significantly increased cell viability, suggesting that the maintenance of zinc homeostasis during envenomation injury improves cell survival.

Computational and in vitro analyses to identify the anticoagulant regions of Echicetin, a snake venom anticoagulant C-type lectin (snaclec): possibility to develop anticoagulant peptide therapeutics?

Snake venom C-type lectins (Snaclecs) display anticoagulant and platelet-modulating activities; however, their interaction with the critical components of blood coagulation factors was unknown. Computational analysis revealed that Echicetin (Snaclec from Echis carinatus venom) interacted with heavy chain of thrombin, and heavy and light chains of factor Xa (FXa). Based on FXa and thrombin binding regions of Echicetin, the two synthetic peptides (1A and 1B) were designed. The in silico binding studies of the peptides with thrombin and FXa showed that peptide 1B interacted with both heavy and light chains of thrombin and, peptide 1A interacted with only heavy chain of thrombin. Similarly, peptide 1B interacted with both heavy and light chains of FXa; however, peptide 1A interacted only with heavy chain of FXa. Alanine screening predicted the hot-spots residues for peptide 1A (Aspartic acid6, Valine8, Valine9, and Tyrosine17 with FXa, and Isoleucine14, Lysine15 with thrombin) and peptide 1B (Valine16 with FXa). Spectrofluorometric interaction study showed a lower Kd value for peptide 1B binding with both FXa and thrombin than peptide 1A, indicating higher binding strength of the former peptide. The circular dichroism spectroscopy also established the interaction between thrombin and the custom peptides. The in vitro study demonstrated higher anticoagulant activity of peptide 1B than peptide 1A due to higher inhibition of thrombin and FXa. Inhibition of anticoagulant activity of the peptides by respective anti-peptide antibodies corroborates our hypothesis that peptides 1A and 1B represent the anticoagulant regions of Echicetin and may be developed as antithrombotic peptide drug prototypes.Communicated by Ramaswamy H. Sarma.

Venom comparisons of endemic and micro-endemic speckled rattlesnakes Crotalus mitchellii, C. polisi and C. thalassoporus from Baja California Peninsula

A high diversity of rattlesnake species can be found in the Baja California peninsula and the island of the Gulf of California, nevertheless, their venom has been poorly evaluated. The aim of this work was to present the first characterization of endemic Crotalus mitchellii, micro endemic C. polisi and C. thalassoporus venoms. All samples provoke human plasma coagulation showing doses in the rank of 2.3-41.0 μg and also produce rapid hydrolysis of the alpha chain of bovine fibrinogen while the beta chain is attacked at larger incubation periods by C. polisi and especially by C. thalassoporus. Phospholipase activity ranging from 23.2 to 173.8 U/mg. The venoms of C. thalassoporus and C. polisi show very high hemorrhagic activity (from 0.03 to 0.31 μg). A total of 130 toxin-related proteins were identified and classified into ten families. Crotalus mitchellii venom was characterized by high abundance of crotoxin-like and other phospholipase proteins (34.5%) and serine proteinases (29.8%). Crotalus polisi showed a similar proportion of metalloproteinases (34%) and serine proteinases (22.8%) components with important contribution of C-type lectins (14.3%) and CRiSP (14.0%) proteins. Venom of C. thalassoporus is dominated by metalloproteases that amount to more than 66% of total toxin proteins. These results provide a foundation for comprehending the biological, ecological and evolutionary significance of venom composition of speckled rattlesnake from the Baja California peninsula.

Past, Present, and Future of Naturally Occurring Antimicrobials Related to Snake Venoms

This review focuses on proteins and peptides with antimicrobial activity because these biopolymers can be useful in the fight against infectious diseases and to overcome the critical problem of microbial resistance to antibiotics. In fact, snakes show the highest diversification among reptiles, surviving in various environments; their innate immunity is similar to mammals and the response of their plasma to bacteria and fungi has been explored mainly in ecological studies. Snake venoms are a rich source of components that have a variety of biological functions. Among them are proteins like lectins, metalloproteinases, serine proteinases, L-amino acid oxidases, phospholipases type A₂, cysteine-rich secretory proteins, as well as many oligopeptides, such as waprins, cardiotoxins, cathelicidins, and β-defensins. In vitro, these biomolecules were shown to be active against bacteria, fungi, parasites, and viruses that are pathogenic to humans. Not only cathelicidins, but all other proteins and oligopeptides from snake venom have been proteolyzed to provide short antimicrobial peptides, or for use as templates for developing a variety of short unnatural sequences based on their structures. In addition to organizing and discussing an expressive amount of information, this review also describes new β-defensin sequences of Sistrurus miliarius that can lead to novel peptide-based antimicrobial agents, using a multidisciplinary approach that includes sequence phylogeny.

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.

Two-Dimensional Blue Native/SDS Polyacrylamide Gel Electrophoresis for Analysis of Brazilian Bothrops Snake Venoms

Viperidae snakes are the most important agents of snakebites in Brazil. The protein composition of snake venoms has been frequently analyzed by means of electrophoretic techniques, but the interaction of proteins in venoms has barely been addressed. An electrophoretic technique that has gained prominence to study this type of interaction is blue native polyacrylamide gel electrophoresis (BN-PAGE), which allows for the high-resolution separation of proteins in their native form. These protein complexes can be further discriminated by a second-dimension gel electrophoresis (SDS-PAGE) from lanes cut from BN-PAGE. Once there is no study on the use of bidimensional BN/SDS-PAGE with snake venoms, this study initially standardized the BN/SDS-PAGE technique in order to evaluate protein interactions in Bothrops atrox, Bothrops erythromelas, and Bothrops jararaca snake venoms. Results of BN/SDS-PAGE showed that native protein complexes were present, and that snake venom metalloproteinases and venom serine proteinases maintained their enzymatic activity after BN/SDS-PAGE. C-type lectin-like proteins were identified by Western blotting. Therefore, bidimensional BN/SDS-PAGE proved to be an easy, practical, and efficient method for separating functional venom proteins according to their assemblage in complexes, as well as to analyze their biological activities in further details.

Divergent Specialization of Simple Venom Gene Profiles among Rear-Fanged Snake Genera (Helicops and Leptodeira, Dipsadinae, Colubridae)

Many venomous animals express toxins that show extraordinary levels of variation both within and among species. In snakes, most studies of venom variation focus on front-fanged species in the families Viperidae and Elapidae, even though rear-fanged snakes in other families vary along the same ecological axes important to venom evolution. Here we characterized venom gland transcriptomes from 19 snakes across two dipsadine rear-fanged genera (Leptodeira and Helicops, Colubridae) and two front-fanged genera (Bothrops, Viperidae; Micrurus, Elapidae). We compared patterns of composition, variation, and diversity in venom transcripts within and among all four genera. Venom gland transcriptomes of rear-fanged Helicops and Leptodeira and front-fanged Micrurus are each dominated by expression of single toxin families (C-type lectins, snake venom metalloproteinase, and phospholipase A2, respectively), unlike highly diverse front-fanged Bothrops venoms. In addition, expression patterns of congeners are much more similar to each other than they are to species from other genera. These results illustrate the repeatability of simple venom profiles in rear-fanged snakes and the potential for relatively constrained venom composition within genera.

Neutralization of "Chaco eagle" (Buteogallus coronatus) serum on some activities of Bothrops spp. venoms

Several species of reptiles and mammals have components in their sera that can neutralize toxic components present in snake venoms. In this manuscript, we studied the neutralizing capacity of Chaco eagle's (Buteogallus coronatus) serum. This South American bird of prey eats snakes as a regular part of its diet and has anatomical features that protect from snakes' bites. The neutralizing potency of the Chaco eagle's serum was tested on lethal, hemorrhagic, procoagulant, and phospholipase activities of the venom of "yarará grande" (Bothrops alternatus) and on phospholipase activity of "yarará ñata" (Bothrops ammodytoides) venom; both snakes are known to be the prey of Chaco eagle. Sera of crested caracara (Caracara plancus-a scavenger, omnivorous pan-American bird of prey), secretary bird (Saggitarius serpentarius-an omnivorous bird of prey from Africa that can include venomous snakes in its diet), common hen (Gallus gallus), rat (Rattus norvegicus), mouse (Mus musculus), horse (Equus caballus), and dog (Canis lupus familiaris) were also tested to compare the inhibitory capacity of neutralization. To test isologous and xenologous neutralization, sera from Bothrops alternatus and white-eared opossum (Didelphis albiventris), respectively, were used due to their known inhibitory activity on Bothrops venoms. As a control for the neutralization activity, antibothropic antivenom was used. Chaco eagle's serum neutralized hemorrhagic and phospholipasic activity and slightly neutralized the coagulation and the lethal activity of Bothrops spp. venom. The neutralizing capacity was present in the non-immunoglobulin fraction of the serum, which showed components of acidic characteristics and lower molecular weight than IgY, in correspondence with the characteristics of PLA₂s and SVMPs inhibitors described in sera from some snakes and mammals. These studies showed that Chaco eagle's serum neutralizes all toxic activities tested at a higher level than sera from animal species in which inhibitors of snake venoms have not been described (p < 0.05), while it is lower or similar in neutralizing capacity to white-eared opossum and B. alternatus sera.

The chemistry of snake venom and its medicinal potential

The fascination and fear of snakes dates back to time immemorial, with the first scientific treatise on snakebite envenoming, the Brooklyn Medical Papyrus, dating from ancient Egypt. Owing to their lethality, snakes have often been associated with images of perfidy, treachery and death. However, snakes did not always have such negative connotations. The curative capacity of venom has been known since antiquity, also making the snake a symbol of pharmacy and medicine. Today, there is renewed interest in pursuing snake-venom-based therapies. This Review focuses on the chemistry of snake venom and the potential for venom to be exploited for medicinal purposes in the development of drugs. The mixture of toxins that constitute snake venom is examined, focusing on the molecular structure, chemical reactivity and target recognition of the most bioactive toxins, from which bioactive drugs might be developed. The design and working mechanisms of snake-venom-derived drugs are illustrated, and the strategies by which toxins are transformed into therapeutics are analysed. Finally, the challenges in realizing the immense curative potential of snake venom are discussed, and chemical strategies by which a plethora of new drugs could be derived from snake venom are proposed.

Venom gene sequence diversity and expression jointly shape diet adaptation in pitvipers

Understanding the joint roles of protein sequence variation and differential expression during adaptive evolution is a fundamental, yet largely unrealized goal of evolutionary biology. Here, we use phylogenetic path analysis to analyze a comprehensive venom-gland transcriptome dataset spanning three genera of pitvipers to identify the functional genetic basis of a key adaptation (venom complexity) linked to diet breadth (DB). The analysis of gene-family-specific patterns reveals that, for genes encoding two of the most important venom proteins (snake venom metalloproteases and snake venom serine proteases), there are direct, positive relationships between sequence diversity (SD), expression diversity (ED), and increased DB. Further analysis of gene-family diversification for these proteins showed no constraint on how individual lineages achieved toxin gene SD in terms of the patterns of paralog diversification. In contrast, another major venom protein family (PLA₂s) showed no relationship between venom molecular diversity and DB. Additional analyses suggest that other molecular mechanisms—such as higher absolute levels of expression—are responsible for diet adaptation involving these venom proteins. Broadly, our findings argue that functional diversity generated through sequence and expression variations jointly determine adaptation in the key components of pitviper venoms, which mediate complex molecular interactions between the snakes and their prey.

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.

Venomics of the poorly studied hognosed pitvipers Porthidium arcosae and Porthidium volcanicum

We report the first proteomics analyses of the venoms of two poorly studied snakes, the Manabi hognosed pitviper Porthidium arcosae endemic to the western coastal province of Manabí (Ecuador), and the Costa Rican hognosed pitviper P. volcanicum with distribution restricted to South Pacific Costa Rica and western Panamá. These venom proteomes share a conserved compositional pattern reported in four other congeneric species within the clade of South American Porthidium species, P. nasutum, P. lansbergii, P. ophryomegas, and P. porrasi. The paraspecific immunorecognition profile of antivenoms produced in Costa Rica (ICP polyvalent), Perú (Instituto Nacional de Salud) and Brazil (soro antibotrópico pentavalente, SAB, from Instituto Butantan) against the venom of P. arcosae was investigated through a third-generation antivenomics approach. The maximal venom-binding capacities of the investigated antivenoms were 97.1 mg, 21.8 mg, and 25.7 mg of P. arcosae venom proteins per gram of SAB, ICP, and INS-PERU antibody molecules, respectively, which translate into 28.4 mg, 13.1 mg, and 15.2 mg of total venom proteins bound per vial of SAB, ICP, and INS-PERU AV. The antivenomics results suggest that 21.8%, 7.8% and 6.1% of the SAB, ICP, and INS-PERU antibody molecules recognized P. arcosae venom toxins. The SAB antivenom neutralized P. arcosae venom's lethality in mice with an ED₅₀ of 31.3 mgV/g SAB AV. This preclinical neutralization paraspecificity points to Brazilian SAB as a promising candidate for the treatment of envenomings by Ecuadorian P. arcosae. BIOLOGICAL SIGNIFICANCE: Assessing the preclinical efficacy profile of antivenoms against homologous and heterologous medically relevant snake venoms represents an important goal towards defining the biogeographic range of their clinical utility. This is particularly relevant in regions, such as Mesoamerica, where a small number of pharmaceutical companies produce antivenoms against the venoms of a small number of species of maximum medical relevance among the local rich herpetofauna, leaving a wide range of snakes of secondary medical relevance, but also causing life-threatening human envenomings without nominal clinical coverage. This work is part of a larger project aiming at mapping the immunological characteristics of antivenoms generated in Latin American countries towards venoms of such poorly studied snakes of the local and neighboring countries' herpetofauna. Here we report the proteomics characterization of the Manabi hognosed pitviper Porthidium arcosae endemic to the western coastal province of Manabí (Ecuador), and the Costa Rican hognosed pitviper P. volcanicum with distribution restricted to southwestern Costa Rica, the antivenomics assessment of three bothropoid commercial antivenoms produced in Costa Rica, Perú, and Brazil against the venom components of P. arcosae, and the in vivo capacity of the Brazilian soro antibotrópico pentavalente (SAB) from Instituto Butantan to neutralize the murine lethality of P. arcosae venom. The preclinical paraspecific ED₅₀ of 31.3 mg of P. arcosae venom per gram of antivenom points to Brazilian SAB as a promising candidate for the treatment of envenomings by the Manabi hognosed pitviper P. arcosae.

Involvement of von Willebrand factor and botrocetin in the thrombocytopenia induced by Bothrops jararaca snake venom

Patients bitten by snakes consistently manifest a bleeding tendency, in which thrombocytopenia, consumption coagulopathy, mucous bleeding, and, more rarely, thrombotic microangiopathy, are observed. Von Willebrand factor (VWF) is required for primary hemostasis, and some venom proteins, such as botrocetin (a C-type lectin-like protein) and snake venom metalloproteinases (SVMP), disturb the normal interaction between platelets and VWF, possibly contributing to snakebite-induced bleedings. To understand the relationship among plasma VWF, platelets, botrocetin and SVMP from Bothrops jararaca snake venom (BjV) in the development of thrombocytopenia, we used (a) Wistar rats injected s.c. with BjV preincubated with anti-botrocetin antibodies (ABA) and/or Na2-EDTA (a SVMP inhibitor), and (b) VWF knockout mice (Vwf-/-) injected with BjV. Under all conditions, BjV induced a rapid and intense thrombocytopenia. In rats, BjV alone reduced the levels of VWF:Ag, VWF:CB, high molecular weight multimers of VWF, ADAMTS13 activity, and factor VIII. Moreover, VWF:Ag levels in rats that received BjV preincubated with Na2-EDTA and/or ABA tended to recover faster. In mice, BjV caused thrombocytopenia in both Vwf-/- and C57BL/6 (background control) strains, and VWF:Ag levels tended to decrease in C57BL/6, demonstrating that thrombocytopenia was independent of the presence of plasma VWF. These findings showed that botrocetin present in BjV failed to affect the extent or the time course of thrombocytopenia induced by envenomation, but it contributed to decrease the levels and function of plasma VWF. Thus, VWF alterations during B. jararaca envenomation are an ancillary event, and not the main mechanism leading to decreased platelet counts.

Structure of the platelet glycoprotein Ib receptor in complex with a novel antithrombotic agent

Agkisacucetin, a snake C-type lectin-like protein isolated from the venom of Deinagkistrodon acutus (formerly Agkistrodon acutus), is a novel antithrombotic drug candidate in phase 2 clinical trials. Agkisacucetin specifically recognizes the platelet surface receptor glycoprotein Ib α chain (GPIbα) to block GPIb and von Willebrand factor (VWF). In this study, we solved the crystal structure of the GPIbα N-terminal domain (residues 1-305) in complex with agkisacucetin to understand their molecular recognition mechanism. The crystal structure showed that agkisacucetin primarily contacts GPIbα at the C-terminal part of the conserved leucine-rich repeat (LRR) domain (LRR-6 to LRR-8) and the previously described "β-switch" region through the β chain. In addition, we found that agkisacucetin α chain contacts part of the GPIbα C-terminal peptide after the LRR domain through complementary charge interactions. This C-terminal peptide plays a key role in GPIbα and thrombin recognition. Therefore, our structure revealed that agkisacucetin can sterically block the interaction between the GPIb receptor and VWF and thrombin proteins to inhibit platelet function. Our structural work provides key molecular insights into how an antithrombotic drug candidate recognizes the GPIb receptor to modulate platelet function to inhibit thrombosis.

From birth to adulthood: An analysis of the Brazilian lancehead (Bothrops moojeni) venom at different life stages

The Brazilian lancehead (Bothrops moojeni) has a wide distribution in Brazil and represents a serious public health hazard. Previous works reported that the symptoms of snakebites caused by B. moojeni juveniles’ bites were mainly related to coagulation, while those caused by adults’ bites had a more prominent local damage. In this work, we analyzed the venoms of B. moojeni at different life stages to better understand the ontogeny shift in this species. Snakes were grouped by age and sex, and venom pools were formed accordingly. Compositional analyses by one-dimensional electrophoresis (1-DE), chromatography, and mass spectrometry revealed that ontogenetic changes might be mostly related to phospholipase A₂ (PLA₂) and metalloproteases. Regarding the venoms functional aspect, proteolytic, L-amino acid oxidase, PLA₂, and coagulant in vitro activities were assayed, but only the first and the last ones showed age-related changes, with the venom of snakes up to 1 year-old displaying lower proteolytic and higher coagulant activities, while those from 2 years-old onward presented the opposite relation. The venoms of 3 years-old snakes were exceptions to the compositional and functional pattern of adults as both venoms presented profiles similar to neonates. Sex-related differences were observed in specific groups and were not age-related. In vivo experiments (median lethal dose and hemorrhagic activity) were statistically similar between neonates and adults, however we verified that the adult venom killed mice faster comparing to the neonates. All venoms were mostly recognized by the antibothropic serum and displayed similar profiles to 1-DE in western blotting. In conclusion, the Brazilian lancehead venom showed ontogenetic shift in its composition and activities. Furthermore, this change occurred in snakes from 1 to 2 years-old, and interestingly the venom pools from 3 years-old snakes had particular characteristics, which highlights the importance of comprehensive studies to better understand venom variability.

Baltetin: a new C-type lectin-like isolated from Bothrops alternatus snake venom which act as a platelet aggregation inhibiting

C-type lectin-like proteins found in snake venom, known as snaclecs, have important effects on hemostasis through targeting membrane receptors, coagulation factors and other hemostatic proteins. Here, we present the isolation and functional characterization of a snaclec isolated from Bothrops alternatus venom, designated as Baltetin. We purified the protein in three chromatographic steps (anion-exchange, affinity and reversed-phase chromatography). Baltetin is a dimeric snaclec that is approximately 15 and 25 kDa under reducing and non-reducing conditions, respectively, as estimated by SDS-PAGE. Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry and Edman degradation sequencing revealed that Baltetin is a heterodimer. The first 40 amino acid residues of the N-terminal region of Baltetin subunits share a high degree of sequence identity with other snaclecs. Baltetin had a specific, dose-dependent inhibitory effect on epinephrine-induced platelet aggregation in human platelet-rich plasma, inhibiting up to 69% of platelet aggregation. Analysis of the infrared spectra suggested that the interaction between Baltetin and platelets can be attributed to the formation of hydrogen bonds between the PO32- groups in the protein and PO2- groups in the platelet membrane. This interaction may lead to membrane lipid peroxidation, which prevents epinephrine from binding to its receptor. The present work suggests that Baltetin, a new C-type lectin-like protein isolated from B. alternatus venom, is the first snaclec to inhibit epinephrine-induced platelet aggregation. This could be of medical interest as a new tool for the development of novel therapeutic agents for the prevention and treatment of thrombotic disorders.

Micrurus surinamensis Peruvian snake venom: Cytotoxic activity and purification of a C-type lectin protein (Ms-CTL) highly toxic to cardiomyoblast-derived H9c2 cells

Micrurus surinamensis (Cuvier, 1817), popularly known as aquatic coral snake, has a broad geographic distribution in the Rainforest of South America. The purpose of this study was to investigate the cytotoxic effect caused by M. surinamensis venom in H9c2 cardiomyoblast cells and to identify protein components involved in cardiotoxic processes. Venom cardiotoxic potential is evidenced by cell viability reduction in a concentration-dependent manner. We have purified one of venom components responsible for this effect after three chromatographic steps: a cytotoxic 23.461 kDa protein, as determined by mass spectrometry. A 19-residue sequence (DCPSGWSSYEGSCYNFFQR) of the purified protein was deduced by MS/MS and exhibited high homology with N-terminal region of C-type lectin from snake venoms. This protein was named Ms-CTL. Morphologically, H9c2 incubation with Ms-CTL led to a significant cellular retraction and formation of cellular aggregates, as observed by microscopy phase-contrast images. Our results indicate that M. surinamensis venom is highly toxic to H9c2 cardiomyoblast cell and less or not cytotoxic to other cell lines, such as HaCat, VERO and U373. Results presented herein will help understanding the mechanisms that underlie cellular damage and tissue destruction, being useful in the development of alternative therapies against these coral snake bites.

Study of the venom proteome of Vipera ammodytes ammodytes (Linnaeus, 1758): A qualitative overview, biochemical and biological profiling

Vipera ammodytes (Va), is the European venomous snake of the greatest medical importance. We analyzed whole venom proteome of the subspecies V. ammodytes ammodytes (Vaa) from Serbia for the first time using the shotgun proteomics approach and identified 99 proteins belonging to four enzymatic families: serine protease (SVSPs), L-amino acid oxidase (LAAOs), metalloproteinases (SVMPs), group II phospholipase (PLA2s), and five nonenzymatic families: cysteine-rich secretory proteins (CRISPs), C-type lectins (snaclecs), growth factors -nerve (NGFs) and vascular endothelium (VEGFs), and Kunitz-type protease inhibitors (SPIs). Considerable enzymatic activity of LAAO, SVSPs, and SVMPs and a high acidic PLA2 activity was measured implying potential of Vaa to produce haemotoxic, myotoxic, neuro and cardiotoxic effects. Moreover, significant antimicrobial activity of Vaa venom against Gram-negative (Klebsiella pneumoniae, Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus) was found. The crude venom shows considerable potential cytotoxic activity on the C6 and HL60 and a moderate level of potency on B16 cell lines. HeLa cells showed the same sensitivity, while DU 145 and PC-3 are less sensitive than as normal cell line. Our data demonstrated a high complexity of Vaa and considerable enzymatic, antibacterial and cytotoxic activity, implying a great medical potential of Vaa venom as a promising source for new antibacterial and cytostatic agents.

Targeted identification of C-type lectins in snake venom by 2DE and Western blot

C-type lectins (CTL) and CTL-like proteins (snaclecs) are important toxins found in snake venom which can disrupt hemostasis by binding platelet membrane glycoproteins. Traditional identification of these toxins usually relies on an "activity-directed fractionation" approach which is very arduous. Here, we report a new method for rapid screening of these proteins in snake venom.

METHODS

A conserved and immunogenic peptide found in svCTLs (CTL and snaclecs) was identified by sequence alignment using DNAStar software. The peptide was de novo synthesized and conjugated to keyhole limpet hemocyanin (KLH). Rabbit antibodies were generated against the peptide by classical immunization. Deinagkistrodon acutus venom was separated by two-dimensional electrophoresis (2DE) followed by Western blot and CTLs immunodetected using the isolated polyclonal antibody. The same svCTL spots on a parallel 2DE gel were isolated and analyzed by MALDI-TOF-MS.

RESULTS

A highly conserved peptide with the sequence "KTWDDAEKFCTEQ" was identified as a common epitope in svCTLs. The polyclonal antibody against the 13aa-peptide was successfully prepared and purified. Its usefulness to detect svCTLs in D. acutus venom was tested by 2DE-WB and we determined that it positively identified all known D. acutus venom CTLs.

CONCLUSIONS

Immunodetection with antibodies against KTWDDAEKFCTEQ is an efficient strategy to identify novel svCTLs in the context of a complex proteome.

A comparative analysis of the proteomes and biological activities of the venoms from two sea snakes, Hydrophis curtus and Hydrophis cyanocinctus, from Hainan, China

We characterized and compared the venom protein profiles of Hydrophis curtus (synonyms: Lapemis hardwickii, Lapemis curtus and Hydrophis hardwickii) and Hydrophis cyanocinctus, the two representatives of medically important venomous sea snakes in Chinese waters using proteomic approaches. A total of 47 and 38 putative toxins were identified in H. curtus venom (HcuV) and H. cyanocinctus venom (HcyV), respectively, and these toxins could be grouped into 15 functional categories, mainly proteinases, phospholipases, three-finger toxins (3FTxs), lectins, protease inhibitors, ion channel inhibitors, cysteine-rich venom proteins (CRVPs) and snake venom metalloproteases (SVMPs). The constituent ratio of each toxin category varied between HcuV and HcyV with 3FTx (54% in HcuV/69% in HcyV) and PLA2 (38% in HcuV/22% in HcyV) unanimously ranked as the top two most abundant families. Both HcuV and HcyV exhibited relatively high lethality (LD₅₀ values in mice of 0.34 μg/g and 0.24 μg/g, respectively), specific PLA2 activity and hemolytic activity. On the basis of several previous reports of HcuV and HcyV collected from other areas, these findings greatly expand our understanding of geographical variation and interspecies diversity of the two sea snake venoms and can provide a scientific basis for the development of specific sea snake antivenom in the future.

Transcriptomic Analysis of Four Cerianthid (Cnidaria, Ceriantharia) Venoms

Tube anemones, or cerianthids, are a phylogenetically informative group of cnidarians with complex life histories, including a pelagic larval stage and tube-dwelling adult stage, both known to utilize venom in stinging-cell rich tentacles. Cnidarians are an entirely venomous group that utilize their proteinaceous-dominated toxins to capture prey and defend against predators, in addition to several other ecological functions, including intraspecific interactions. At present there are no studies describing the venom for any species within cerianthids. Given their unique development, ecology, and distinct phylogenetic-placement within Cnidaria, our objective is to evaluate the venom-like gene diversity of four species of cerianthids from newly collected transcriptomic data. We identified 525 venom-like genes between all four species. The venom-gene profile for each species was dominated by enzymatic protein and peptide families, which is consistent with previous findings in other cnidarian venoms. However, we found few toxins that are typical of sea anemones and corals, and furthermore, three of the four species express toxin-like genes closely related to potent pore-forming toxins in box jellyfish. Our study is the first to provide a survey of the putative venom composition of cerianthids and contributes to our general understanding of the diversity of cnidarian toxins.

Resistance of South American opossums to vWF-binding venom C-type lectins

Opossums in the clade Didelphini are well known to be resistant to snake venom due to endogenous circulating inhibitors which target metalloproteinases and phospholipases. However, the mechanisms through which these opossums cope with a variety of other damaging venom proteins are unknown. A protein involved in blood clotting (von Willebrand Factor) has been found to have undergone rapid adaptive evolution in venom-resistant opossums. This protein is a known target for a subset of snake venom C-type lectins (CTLs), which bind it and then induce it to bind platelets, causing hemostatic disruption. Several amino acid changes in vWF unique to these opossums could explain their resistance; however, experimental evidence that these changes disrupt venom CTL binding was lacking. We used platelet aggregation assays to quantify resistance to a venom-induced platelet response in two species of venom-resistant opossums (Didelphis virginiana, Didelphis aurita), and one venom-sensitive opossum (Monodelphis domestica). We found that all three species have lost nearly all their aggregation response to the venom CTLs tested. Using washed platelet assays we showed that this loss of aggregation response is not due to inhibitors in the plasma, but rather to the failure of either vWF or platelets (or both) to respond to venom CTLs. These results demonstrate the potential adaptive function of a trait previously shown to be evolving under positive selection. Surprisingly, these findings also expand the list of potentially venom tolerant species to include Monodelphis domestica and suggest that an ecological relationship between opossums and vipers may be a broader driver of adaptive evolution across South American marsupials than previously thought.

Dagestan blunt-nosed viper, Macrovipera lebetina obtusa (Dwigubsky, 1832), venom. Venomics, antivenomics, and neutralization assays of the lethal and toxic venom activities by anti-Macrovipera lebetina turanica and anti-Vipera berus berus antivenoms

We have applied a combination of venomics, in vivo neutralization assays, and in vitro third-generation antivenomics analysis to assess the preclinical efficacy of the monospecific anti-Macrovipera lebetina turanica (anti-Mlt) antivenom manufactured by Uzbiopharm® (Uzbekistan) and the monospecific anti-Vipera berus berus antivenom from Microgen® (Russia) against the venom of Dagestan blunt-nosed viper, Macrovipera lebetina obtusa (Mlo). Despite their low content of homologous (anti-Mlt, 5–10%) or para-specific (anti-Vbb, 4–9%) F(ab')₂ antibody fragments against M. l. obtusa venom toxins, both antivenoms efficiently recognized most components of the complex venom proteome's arsenal, which is made up of toxins derived from 11 different gene families and neutralized, albeit at different doses, key toxic effects of M. l. obtusa venom, i.e., in vivo lethal and hemorrhagic effects in a murine model, and in vitro phospholipase A₂, proteolytic and coagulant activities. The calculated lethality neutralization potencies for Uzbiopharm® anti-Mlt and anti-Vbb Microgen® antivenoms were 1.46 and 1.77 mg/mL, indicating that 1 mL of Uzbiopharm® and Microgen® antivenoms may protect mice from 41 to 50 LD₅₀s of Mlo venom, respectively. The remarkable degree of conservation of immunogenic determinants between species of the clades of European and Oriental viper, which evolved geographically segregated since the early Miocene, suggests an eventual window of opportunity for the treatment of envenomings by Eurasian snakes. Clearly, the rational use of heterologous antivenoms requires establishing their para-specificity landscapes. This paper illustrates the analytical power of combining in vitro and in vivo preclinical quantitative assays toward this goal.

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Efficacy against M. l. obtusa venom by two antivenoms was investigated.

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Quantification of lethality neutralizing antibodies was assessed.

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Anti-Vipera berus antivenom showed paraspecificity against M. l. obtusa venom.

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This study provides hints as how to improve the potency of the antivenoms sampled.

Sergentomyia schwetzi: Salivary gland transcriptome, proteome and enzymatic activities in two lineages adapted to different blood sources

During the blood feeding, sand fly females inject saliva containing immunomodulatory and anti-haemostatic molecules into their vertebrate hosts. The saliva composition is species-specific, likely due to an adaptation to particular haemostatic pathways of their preferred host. Research on sand fly saliva is limited to the representatives of two best-studied genera, Phlebotomus and Lutzomyia. Although the members of the genus Sergentomyia are highly abundant in many areas in the Old World, their role in human disease transmission remains uncertain. Most Sergentomyia spp. preferentially attack various species of reptiles, but feeding on warm-blooded vertebrates, including humans and domestic animals, has been repeatedly described, especially for Sergentomyia schwetzi, of which salivary gland transcriptome and proteome is analyzed in the current study. Illumina RNA sequencing and de novo assembly of the reads and their annotation revealed 17,293 sequences homologous to other arthropods’ proteins. In the sialome, all proteins typical for sand fly saliva were identified–antigen 5-related, lufaxin, yellow-related, PpSP15-like, D7-related, ParSP25-like, and silk proteins, as well as less frequent salivary proteins included 71kDa-like, ParSP80-like, SP16-like, and ParSP17-like proteins. Salivary enzymes include apyrase, hyaluronidase, endonuclease, amylase, lipase A2, adenosine deaminase, pyrophosphatase, 5’nucleotidase, and ribonuclease. Proteomics analysis of salivary glands identified 631 proteins, 81 of which are likely secreted into the saliva. We also compared two S. schwetzi lineages derived from the same origin. These lineages were adapted for over 40 generations for blood feeding either on mice (S-M) or geckos (S-G), two vertebrate hosts with different haemostatic mechanisms. Altogether, 20 and 40 annotated salivary transcripts were up-regulated in the S-M and S-G lineage, respectively. Proteomic comparison revealed ten salivary proteins more abundant in the lineage S-M, whereas 66 salivary proteins were enriched in the lineage S-G. No difference between lineages was found for apyrase activity; contrarily the hyaluronidase activity was significantly higher in the lineage feeding on mice.

Cell-Based Adhesion Assays for Isolation of Snake Venom's Integrin Antagonists

Snake venoms could lead to the development of new drugs to treat a range of life-threatening conditions like cardiovascular diseases. Most snake venoms contain a large variety of lethal toxins as well as anti-adhesive proteins such as disintegrins, which have evolved from the harmless compounds ADAMs (proteins with a disintegrin and a metalloprotease domain) and C-type lectin proteins which disturb connective tissue and cell-matrix interaction. These anti-adhesive proteins target and block integrin receptors and disrupt normal biological processes in snakes' prey such as connective tissue physiology and blood clotting. This chapter provides the experimental details of a practical, cell-based adhesion protocol to help identify and isolate disintegrins and C-type lectin proteins from snake venoms, important tools in integrin research and lead compounds for drug discovery.

Phylovenomics of Daboia russelii across the Indian subcontinent. Bioactivities and comparative in vivo neutralization and in vitro third-generation antivenomics of antivenoms against venoms from India, Bangladesh and Sri Lanka

Russell's viper (Daboia russelii) is, together with Naja naja, Bungarus caeruleus and Echis carinatus, a member of the medically important 'Big Four' species responsible for causing a large number of morbidity and mortality cases across the Indian subcontinent. Despite the wide distribution of Russell's viper and the well-documented ubiquity of the phenomenon of geographic variability of intraspecific snake venom composition, Indian polyvalent antivenoms against the "Big Four" venoms are raised against venoms sourced mainly from Chennai in the southeastern Indian state of Tamil Nadu. Biochemical and venomics investigations have consistently revealed notable compositional, functional, and immunological differences among geographic variants of Russell's viper venoms across the Indian subcontinent. However, these studies, carried out by different laboratories using different protocols and involving venoms from a single geographical region, make the comparison of the different venoms difficult. To bridge this gap, we have conducted bioactivities and proteomic analyses of D. russelii venoms from the three corners of the Indian subcontinent, Pakistan, Bangladesh, and Tamil Nandu (India) and Sri Lanka, along with comparative in vivo neutralization and in vitro third-generation antivenomics of antivenoms used in India, Bangladesh and Sri Lanka. These analyses let us to propose two alternative routes of radiation for Russell's viper in the Indian subcontinent. Both radiations, towards the northeast of India and Bangladesh and towards south India and Sri Lanka, have a common origin in Pakistan, and provide a phylovenomics ground for rationalizing the geographic variability in venom composition and their distinct immunoreactivity against available antivenoms. BIOLOGICAL SIGNIFICANCE: Russell's viper (Daboia russelii), the Indian cobra (Naja naja), the common krait (Bungarus caeruleus), and the saw-scaled viper (Echis carinatus) constitute the 'Big Four' snake species responsible for most snakebite envenomings and deaths in the Indian subcontinent. Despite the medical relevance of Daboia russelii, and the well documented variations in the clinical manifestations of envenomings by this wide distributed species, which are doubtless functionally related to differences in venom composition of its geographic variants, antivenoms for the clinical treatment of envenomings by D. russelii across the Indian subcontinent are invariably raised using venom sourced mainly from the southeastern Indian state of Tamil Nadu. We have applied a phylovenomics approach to compare the venom proteomes of Russell's vipers from the three corners of the Indian subcontinent, Pakistan, Bangladesh, and South India/Sri Lanka, and have assessed the in vitro (third-generation antivenomics) and in vivo preclinical efficacy of a panel of homologous antivenoms. The identification of two dispersal routes of ancestral D. russelii into the Indian subcontinent provides the ground for rationalizing the variability in composition and immunoreactivity of the venoms of extant geographic variants of Russell's viper. Such knowledge is relevant for envisioning strategies to improve the clinical coverage of anti- D. russelii antivenoms.

From Snake Venom's Disintegrins and C-Type Lectins to Anti-Platelet Drugs

Snake venoms are attractive natural sources for drug discovery and development, with a number of substances either in clinical use or in research and development. These drugs were developed based on RGD-containing snake venom disintegrins, which efficiently antagonize fibrinogen activation of αIIbβ3 integrin (glycoprotein GP IIb/IIIa). Typical examples of anti-platelet drugs found in clinics are Integrilin (Eptifibatide), a heptapeptide derived from Barbourin, a protein found in the venom of the American Southeastern pygmy rattlesnake and Aggrastat (Tirofiban), a small molecule based on the structure of Echistatin, and a protein found in the venom of the saw-scaled viper. Using a similar drug discovery approach, linear and cyclic peptides containing the sequence K(R)TS derived from VP12, a C-type lectin protein found in the venom of Israeli viper venom, were used as a template to synthesize Vipegitide, a novel peptidomimetic antagonist of α2β1 integrin, with anti-platelet activity. This review focus on drug discovery of these anti-platelet agents, their indications for clinical use in acute coronary syndromes and percutaneous coronary intervention based on several clinical trials, as well as their adverse effects.

Subproteome of Lachesis muta rhombeata venom and preliminary studies on LmrSP-4, a novel snake venom serine proteinase

Background:

Lachesis muta rhombeata is one of the venomous snakes of medical importance in Brazil whose envenoming is characterized by local and systemic effects which may produce even shock and death. Its venom is mainly comprised of serine and metalloproteinases, phospholipases A₂ and bradykinin-potentiating peptides. Based on a previously reported fractionation of L. m. rhombeata venom (LmrV), we decided to perform a subproteome analysis of its major fraction and investigated a novel component present in this venom.

Methods:

LmrV was fractionated through molecular exclusion chromatography and the main fraction (S5) was submitted to fibrinogenolytic activity assay and fractionated by reversed-phase chromatography. The N-terminal sequences of the subfractions eluted from reversed-phase chromatography were determined by automated Edman degradation. Enzyme activity of LmrSP-4 was evaluated upon chromogenic substrates for thrombin (S-2238), plasma kallikrein (S-2302), plasmin and streptokinase-activated plasminogen (S-2251) and Factor Xa (S-2222) and upon fibrinogen. All assays were carried out in the presence or absence of possible inhibitors. The fluorescence resonance energy transfer substrate Abz-KLRSSKQ-EDDnp was used to determine the optimal conditions for LmrSP-4 activity. Molecular mass of LmrSP-4 was determined by MALDI-TOF and digested peptides after trypsin and Glu-C treatments were analyzed by high resolution MS/MS using different fragmentation modes.

Results:

Fraction S5 showed strong proteolytic activity upon fibrinogen. Its fractionation by reversed-phase chromatography gave rise to 6 main fractions (S5C1-S5C6). S5C1-S5C5 fractions correspond to serine proteinases whereas S5C6 represents a C-type lectin. S5C4 (named LmrSP-4) had its N-terminal determined by Edman degradation up to the 53^rd amino acid residue and was chosen for characterization studies. LmrSP-4 is a fibrinogenolytic serine proteinase with high activity against S-2302, being inhibited by PMSF and benzamidine, but not by 1,10-phenantroline. In addition, this enzyme exhibited maximum activity within the pH range from neutral to basic and between 40 and 50 °C. About 68% of the LmrSP-4 primary structure was covered, and its molecular mass is 28,190 Da.

Conclusions:

Novel serine proteinase isoforms and a lectin were identified in LmrV. Additionally, a kallikrein-like serine proteinase that might be useful as molecular tool for investigating bradykinin-involving process was isolated and partially characterized.

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.

Comparative study of platelet aggregation and secretion induced by Bothrops jararaca snake venom and thrombin

Victims of Bothrops jararaca snakebites manifest bleedings, blood incoagulability, platelet dysfunction, and thrombocytopenia, and the latter has been directly implicated in the genesis of hemorrhagic diathesis. We addressed herein the direct effects of B. jararaca venom (BjV) on ex vivo platelet aggregation and granule secretion in washed human and mouse platelets. BjV directly aggregated platelets, but the extent of platelet aggregation was lower in human than mouse platelets. On the other hand, BjV (24.4 μg/mL) and thrombin (0.1 U/mL) induced a similar extent of ATP and platelet factor 4 (PF4) secretion in both species. BjV-induced platelet aggregation was independent of the platelet dense body content, as in pearl mouse (Ap3b1^-/-) platelets, whose dense bodies are deficient in adenine nucleotides and serotonin, the extent of platelet aggregation was superior to that induced in BALB/c or C57BL/6 mice. BjV-induced β-hexosaminidase secretion in human platelets was less intense than that evoked by thrombin, and the contrary was observed in mouse platelets. Irreversible inactivation of platelet cyclooxygenase 1 by acetylsalicylic acid did not reduce BjV-induced platelet aggregation. BjV exerted no cytotoxic activity in human and mouse platelets, as evaluated by lactate dehydrogenase loss. Eptifibatide, which inhibits the binding of fibrinogen to platelet glycoprotein complex GPIIb-IIIa, differently blocked BjV-induced platelet aggregation in mice and humans. BjV-induced platelet aggregation did not depend on snake venom serine proteinases nor metalloproteinases in mice, whilst serine proteinases were rather important for platelet aggregation in humans. Our results show that BjV induces direct activation, aggregation, and secretion in human and mouse platelets, but it exerts diverse responses in them, which should be considered in comparative studies to understand pathophysiological events during Bothrops envenomation.

Snake venom proteome and immuno-profiling of the hundred-pace viper, Deinagkistrodon acutus, in Taiwan

Deinagkistrodon acutus, also known as the hundred-pace viper or Chinese moccasin, is a clinically significant venomous snake in Taiwan. To address the lack of knowledge on the venom proteome of D. acutus, the venom composition was studied by a bottom-up proteomic approach combining reverse phase high-performance liquid chromatography, SDS-PAGE, and LC-MS/MS analysis. The immunoreactivity and cross-reactivity of Taiwanese freeze-dried D. acutus antivenom (DA-AV) and hemorrhagic antivenom (FH-AV) were investigated, as well. The proteomic analysis revealed the presence of 29 distinct proteins from D. acutus venom belonging to 8 snake venom protein families. Snake venom metalloproteinase (SVMP, 46.86%), C-type lectin (CLEC, 37.59%), phospholipase A₂ (PLA₂, 7.33%) and snake venom serine protease (SVSP, 6.62%) were the most abundant proteins. In addition to DA-AV, FH-AV also showed a profile of broad immunorecognition toward the venom of D. acutus. Remarkably, both antivenoms specifically reacted with the HPLC fractions containing SVMPs, and the titer was 5-10 times higher than fractions of other components. This information helps us to deeply understand the pathophysiology of D. acutus envenomation and guide us to development of more effective antivenom for clinical treatment.

Biochemical characterization of venom from Pseudoboa neuwiedii (Neuwied's false boa; Xenodontinae; Pseudoboini)

In this work, we examined the proteolytic and phospholipase A₂ (PLA₂) activities of venom from the opisthoglyphous colubrid Pseudoboa neuwiedii. Proteolytic activity (3 and 10 μg of venom) was comparable to that of Bothrops neuwiedii venom but less than Bothrops atrox. This activity was inhibited by EDTA and 1,10-phenanthroline but only slightly affected (≤30% inhibition) by PMSF and AEBSF, indicating it was mediated by snake venom metalloproteinases (SVMPs). The pH and temperature optima for proteolytic activity were 8.0 and 37 °C, respectively. The venom had no esterase activity, whereas PLA₂ activity was similar to B. atrox, greater than B. neuwiedii but less than B. jararacussu. SDS-PAGE revealed venom proteins >100 kDa, 45-70 kDa, 21-24 kDa and ~15 kDa, and mass spectrometry of protein bands revealed SVMPs, cysteine-rich secretory proteins (CRISPs) and PLA₂, but no serine proteinases. In gelatin zymography, the most active bands occurred at 65-68 kDa (seen with 0.05-0.25 μg of venom). Caseinolytic activity occurred at 50-66 kDa and was generally weaker than gelatinolytic activity. RP-HPLC of venom yielded 15 peaks, five of which showed gelatinolytic activity; peak 7 was the most active and apparently contained a P-III class SVMP. The venom showed α-fibrinogenase activity, without affecting the β and γ chains; this activity was inhibited by EDTA and 1,10-phenanthroline. The venom did not clot rat citrated plasma but reduced the rate and extent of coagulation after plasma recalcification. In conclusion, P. neuwiedii venom is highly proteolytic and could potentially affect coagulation in vivo by degrading fibrinogen via SVMPs.

Snake venom components in medicine: From the symbolic rod of Asclepius to tangible medical research and application

Both mythologically and logically, snakes have always fascinated man. Snakes have attracted both awe and fear not only because of the elegant movement of their limbless bodies, but also because of the potency of their deadly venoms. Practically, in 2017, the world health organization (WHO) listed snake envenomation as a high priority neglected disease, as snakes inflict up to 2.7 million poisonous bites, around 100.000 casualties, and about three times as many invalidities on man. The venoms of poisonous snakes are a cocktail of potent compounds which specifically and avidly target numerous essential molecules with high efficacy. The individual effects of all venom toxins integrate into lethal dysfunctions of almost any organ system. It is this efficacy and specificity of each venom component, which after analysis of its structure and activity may serve as a potential lead structure for chemical imitation. Such toxin mimetics may help in influencing a specific body function pharmaceutically for the sake of man's health. In this review article, we will give some examples of snake venom components which have spurred the development of novel pharmaceutical compounds. Moreover, we will provide examples where such snake toxin-derived mimetics are in clinical use, trials, or consideration for further pharmaceutical exploitation, especially in the fields of hemostasis, thrombosis, coagulation, and metastasis. Thus, it becomes clear why a snake captured its symbolic place at the Asclepius rod with good reason still nowadays.

Comprehensive Snake Venomics of the Okinawa Habu Pit Viper, Protobothrops flavoviridis, by Complementary Mass Spectrometry-Guided Approaches

The Asian world is home to a multitude of venomous and dangerous snakes, which are used to induce various medical effects in the preparation of traditional snake tinctures and alcoholics, like the Japanese snake wine, named Habushu. The aim of this work was to perform the first quantitative proteomic analysis of the Protobothrops flavoviridis pit viper venom. Accordingly, the venom was analyzed by complimentary bottom-up and top-down mass spectrometry techniques. The mass spectrometry-based snake venomics approach revealed that more than half of the venom is composed of different phospholipases A2 (PLA₂). The combination of this approach and an intact mass profiling led to the identification of the three main Habu PLA₂s. Furthermore, nearly one-third of the total venom consists of snake venom metalloproteinases and disintegrins, and several minor represented toxin families were detected: C-type lectin-like proteins (CTL), cysteine-rich secretory proteins (CRISP), snake venom serine proteases (svSP), l-amino acid oxidases (LAAO), phosphodiesterase (PDE) and 5'-nucleotidase. Finally, the venom of P. flavoviridis contains certain bradykinin-potentiating peptides and related peptides, like the svMP inhibitors, pEKW, pEQW, pEEW and pENW. In preliminary MTT cytotoxicity assays, the highest cancerous-cytotoxicity of crude venom was measured against human neuroblastoma SH-SY5Y cells and shows disintegrin-like effects in some fractions.

Translational Venomics: Third-Generation Antivenomics of Anti-Siamese Russell's Viper, Daboia siamensis, Antivenom Manufactured in Taiwan CDC's Vaccine Center

The venom proteome of Siamese Russell’s viper from Taiwan, alongside complementary in vivo lethality neutralization assay and in vitro third-generation antivenomics assessment of the preclinical efficacy of the homologous antivenom manufactured in Taiwan CDC’s Vaccine Center, are here reported. Taiwanese Russell’s viper venom proteome comprised 25 distinct gene products, with the heterodimeric PLA₂ viperotoxin-F representing the most abundant toxin (47.5% of total venom proteome). Coagulation FV-activating serine proteinase (RVV-V, 14%), the PIV-SVMP activator of FX (RVV-FX, 8.5%), and less abundant toxins from nine protein families, make up its venom proteome. Venom composition-pathology correlations of D. siamensis envenomings in Taiwan are discussed. The lethal effect of Taiwanese D. siamensis venom was 0.47 mg/g mouse. Antivenomics-guided assessment of the toxin recognition landscape of the Taiwanese Russell’s viper antivenom, in conjunction with complementary in vivo neutralization analysis, informed the antivenom’s maximal toxin immunorecognition ability (14 mg total venom proteins/vial), neutralization capacity (6.5 mg venom/vial), and relative content of lethality neutralizing antibodies (46.5% of the toxin-binding F(ab’)₂ antibodies). The antivenomics analysis also revealed suboptimal aspects of the CDC-Taiwan antivenom. Strategies to improve them are suggested.

Phenotypic Variation in Mojave Rattlesnake (Crotalus scutulatus) Venom Is Driven by Four Toxin Families

Phenotypic diversity generated through altered gene expression is a primary mechanism facilitating evolutionary response in natural systems. By linking the phenotype to genotype through transcriptomics, it is possible to determine what changes are occurring at the molecular level. High phenotypic diversity has been documented in rattlesnake venom, which is under strong selection due to its role in prey acquisition and defense. Rattlesnake venom can be characterized by the presence (Type A) or absence (Type B) of a type of neurotoxic phospholipase A2 (PLA2), such as Mojave toxin, that increases venom toxicity. Mojave rattlesnakes (Crotalus scutulatus), represent this diversity as both venom types are found within this species and within a single panmictic population in the Sonoran Desert. We used comparative venom gland transcriptomics of nine specimens of C. scutulatus from this region to test whether expression differences explain diversity within and between venom types. Type A individuals expressed significantly fewer toxins than Type B individuals owing to the diversity of C-type lectins (CTLs) and snake venom metalloproteinases (SVMPs) found in Type B animals. As expected, both subunits of Mojave toxin were exclusively found in Type A individuals but we found high diversity in four additional PLA2s that was not associated with a venom type. Myotoxin a expression and toxin number variation was not associated with venom type, and myotoxin a had the highest range of expression of any toxin class. Our study represents the most comprehensive transcriptomic profile of the venom type dichotomy in rattlesnakes and C. scutulatus. Even intra-specifically, Mojave rattlesnakes showcase the diversity of snake venoms and illustrate that variation within venom types blurs the distinction of the venom dichotomy.

Impact of Scyphozoan Venoms on Human Health and Current First Aid Options for Stings

Cnidaria include the most venomous animals of the world. Among Cnidaria, Scyphozoa (true jellyfish) are ubiquitous, abundant, and often come into accidental contact with humans and, therefore, represent a threat for public health and safety. The venom of Scyphozoa is a complex mixture of bioactive substances—including thermolabile enzymes such as phospholipases, metalloproteinases, and, possibly, pore-forming proteins—and is only partially characterized. Scyphozoan stings may lead to local and systemic reactions via toxic and immunological mechanisms; some of these reactions may represent a medical emergency. However, the adoption of safe and efficacious first aid measures for jellyfish stings is hampered by the diffusion of folk remedies, anecdotal reports, and lack of consensus in the scientific literature. Species-specific differences may hinder the identification of treatments that work for all stings. However, rinsing the sting site with vinegar (5% acetic acid) and the application of heat (hot pack/immersion in hot water) or lidocaine appear to be substantiated by evidence. Controlled clinical trials or reliable models of envenomation are warranted to confirm the efficacy and safety of these approaches and identify possible species-specific exceptions. Knowledge of the precise composition of Scyphozoa venom may open the way to molecule-oriented therapies in the future.

Dramatic and concerted conformational changes enable rhodocetin to block α2β1 integrin selectively

The collagen binding integrin α2β1 plays a crucial role in hemostasis, fibrosis, and cancer progression amongst others. It is specifically inhibited by rhodocetin (RC), a C-type lectin-related protein (CLRP) found in Malayan pit viper (Calloselasma rhodostoma) venom. The structure of RC alone reveals a heterotetramer arranged as an αβ and γδ subunit in a cruciform shape. RC specifically binds to the collagen binding A-domain of the integrin α2 subunit, thereby blocking collagen-induced platelet aggregation. However, until now, the molecular basis for this interaction has remained unclear. Here, we present the molecular structure of the RCγδ-α2A complex solved to 3.0 Å resolution. Our findings show that RC undergoes a dramatic structural reorganization upon binding to α2β1 integrin. Besides the release of the nonbinding RCαβ tandem, the RCγ subunit interacts with loop 2 of the α2A domain as result of a dramatic conformational change. The RCδ subunit contacts the integrin α2A domain in the “closed” conformation through its helix C. Combined with epitope-mapped antibodies, conformationally locked α2A domain mutants, point mutations within the α2A loop 2, and chemical modifications of the purified toxin protein, this molecular structure of RCγδ-α2A complex explains the inhibitory mechanism and specificity of RC for α2β1 integrin.

In animals, collagen-mediated platelet aggregation is an essential component of the blood’s clotting response following vascular injury. A small group of snake venom toxins belonging to the C-type lectin protein family exert their harmful effects by directly targeting this pathway. Rhodocetin (RC) is a heterotetrameric protein found in the venom of the Malayan pit viper (C. rhodostoma). RC specifically binds α2β1 integrin, the key protein required for collagen-mediated platelet aggregation. In this study, we describe the interaction between RC and α2β1 integrin at atomic resolution. This study reveals that RC undergoes a massive structural reorganization upon α2β1 integrin binding, such that RC’s αβ subunit is released from its γδ subunit and a γδ-α2β1 integrin complex is formed. The inhibitory nature of this complex can be readily explained as RC binding along the top surface of the α2β1 integrin and directly above the collagen binding site. As a result, access of collagen to its binding site is blocked, thereby preventing collagen-mediated platelet aggregation.

Comparative venom gland transcriptomics of Naja kaouthia (monocled cobra) from Malaysia and Thailand: elucidating geographical venom variation and insights into sequence novelty

Background

The monocled cobra (Naja kaouthia) is a medically important venomous snake in Southeast Asia. Its venom has been shown to vary geographically in relation to venom composition and neurotoxic activity, indicating vast diversity of the toxin genes within the species. To investigate the polygenic trait of the venom and its locale-specific variation, we profiled and compared the venom gland transcriptomes of N. kaouthia from Malaysia (NK-M) and Thailand (NK-T) applying next-generation sequencing (NGS) technology.

Methods

The transcriptomes were sequenced on the Illumina HiSeq platform, assembled and followed by transcript clustering and annotations for gene expression and function. Pairwise or multiple sequence alignments were conducted on the toxin genes expressed. Substitution rates were studied for the major toxins co-expressed in NK-M and NK-T.

Results and discussion

The toxin transcripts showed high redundancy (41–82% of the total mRNA expression) and comprised 23 gene families expressed in NK-M and NK-T, respectively (22 gene families were co-expressed). Among the venom genes, three-finger toxins (3FTxs) predominated in the expression, with multiple sequences noted. Comparative analysis and selection study revealed that 3FTxs are genetically conserved between the geographical specimens whilst demonstrating distinct differential expression patterns, implying gene up-regulation for selected principal toxins, or alternatively, enhanced transcript degradation or lack of transcription of certain traits. One of the striking features that elucidates the inter-geographical venom variation is the up-regulation of α-neurotoxins (constitutes ∼80.0% of toxin’s fragments per kilobase of exon model per million mapped reads (FPKM)), particularly the long-chain α-elapitoxin-Nk2a (48.3%) in NK-T but only 1.7% was noted in NK-M. Instead, short neurotoxin isoforms were up-regulated in NK-M (46.4%). Another distinct transcriptional pattern observed is the exclusively and abundantly expressed cytotoxin CTX-3 in NK-T. The findings suggested correlation with the geographical variation in proteome and toxicity of the venom, and support the call for optimising antivenom production and use in the region. Besides, the current study uncovered full and partial sequences of numerous toxin genes from N. kaouthia which have not been reported hitherto; these include N. kaouthia-specific l-amino acid oxidase (LAAO), snake venom serine protease (SVSP), cystatin, acetylcholinesterase (AChE), hyaluronidase (HYA), waprin, phospholipase B (PLB), aminopeptidase (AP), neprilysin, etc. Taken together, the findings further enrich the snake toxin database and provide deeper insights into the genetic diversity of cobra venom toxins.

The Molecular Basis of Toxins' Interactions with Intracellular Signaling via Discrete Portals

An understanding of the molecular mechanisms by which microbial, plant or animal-secreted toxins exert their action provides the most important element for assessment of human health risks and opens new insights into therapies addressing a plethora of pathologies, ranging from neurological disorders to cancer, using toxinomimetic agents. Recently, molecular and cellular biology dissecting tools have provided a wealth of information on the action of these diverse toxins, yet, an integrated framework to explain their selective toxicity is still lacking. In this review, specific examples of different toxins are emphasized to illustrate the fundamental mechanisms of toxicity at different biochemical, molecular and cellular- levels with particular consideration for the nervous system. The target of primary action has been highlighted and operationally classified into 13 sub-categories. Selected examples of toxins were assigned to each target category, denominated as portal, and the modulation of the different portal’s signaling was featured. The first portal encompasses the plasma membrane lipid domains, which give rise to pores when challenged for example with pardaxin, a fish toxin, or is subject to degradation when enzymes of lipid metabolism such as phospholipases A₂ (PLA₂) or phospholipase C (PLC) act upon it. Several major portals consist of ion channels, pumps, transporters and ligand gated ionotropic receptors which many toxins act on, disturbing the intracellular ion homeostasis. Another group of portals consists of G-protein-coupled and tyrosine kinase receptors that, upon interaction with discrete toxins, alter second messengers towards pathological levels. Lastly, subcellular organelles such as mitochondria, nucleus, protein- and RNA-synthesis machineries, cytoskeletal networks and exocytic vesicles are also portals targeted and deregulated by other diverse group of toxins. A fundamental concept can be drawn from these seemingly different toxins with respect to the site of action and the secondary messengers and signaling cascades they trigger in the host. While the interaction with the initial portal is largely determined by the chemical nature of the toxin, once inside the cell, several ubiquitous second messengers and protein kinases/ phosphatases pathways are impaired, to attain toxicity. Therefore, toxins represent one of the most promising natural molecules for developing novel therapeutics that selectively target the major cellular portals involved in human physiology and diseases.

Proteomic Characterization and Comparison of Malaysian Tropidolaemus wagleri and Cryptelytrops purpureomaculatus Venom Using Shotgun-Proteomics

Tropidolaemus wagleri and Cryptelytrops purpureomaculatus are venomous pit viper species commonly found in Malaysia. Tandem mass spectrometry analysis of the crude venoms has detected different proteins in T. wagleri and C. purpureomaculatus. They were classified into 13 venom protein families consisting of enzymatic and nonenzymatic proteins. Enzymatic families detected in T. wagleri and C. purpureomaculatus venom were snake venom metalloproteinase, phospholipase A₂, l-amino acid oxidase, serine proteases, 5′-nucleotidase, phosphodiesterase, and phospholipase B. In addition, glutaminyl cyclotransferase was detected in C. purpureomaculatus. C-type lectin-like proteins were common nonenzymatic components in both species. Waglerin was present and unique to T. wagleri—it was not in C. purpureomaculatus venom. In contrast, cysteine-rich secretory protein, bradykinin-potentiating peptide, and C-type natriuretic peptide were present in C. purpureomaculatus venom. Composition of the venom proteome of T. wagleri and C. purpureomaculatus provides useful information to guide production of effective antivenom and identification of proteins with potential therapeutic applications.