Bioinformatics and multiepitope DNA immunization to design rational snake antivenom

ADDovenom: Thermostable Protein-Based ADDomer Nanoparticles as New Therapeutics for Snakebite Envenoming

Snakebite envenoming can be a life-threatening medical emergency that requires prompt medical intervention to neutralise the effects of venom toxins. Each year up to 138,000 people die from snakebites and threefold more victims suffer life-altering disabilities. The current treatment of snakebite relies solely on antivenom-polyclonal antibodies isolated from the plasma of hyperimmunised animals-which is associated with numerous deficiencies. The ADDovenom project seeks to deliver a novel snakebite therapy, through the use of an innovative protein-based scaffold as a next-generation antivenom. The ADDomer is a megadalton-sized, thermostable synthetic nanoparticle derived from the adenovirus penton base protein; it has 60 high-avidity binding sites to neutralise venom toxins. Here, we outline our experimental strategies to achieve this goal using state-of-the-art protein engineering, expression technology and mass spectrometry, as well as in vitro and in vivo venom neutralisation assays. We anticipate that the approaches described here will produce antivenom with unparalleled efficacy, safety and affordability.

A current perspective on snake venom composition and constituent protein families

Snake venoms are heterogeneous mixtures of proteins and peptides used for prey subjugation. With modern proteomics there has been a rapid expansion in our knowledge of snake venom composition, resulting in the venom proteomes of 30% of vipers and 17% of elapids being characterised. From the reasonably complete proteomic coverage of front-fanged snake venom composition (179 species-68 species of elapids and 111 species of vipers), the venoms of vipers and elapids contained 42 different protein families, although 18 were only reported in < 5% of snake species. Based on the mean abundance and occurrence of the 42 protein families, they can be classified into 4 dominant, 6 secondary, 14 minor, and 18 rare protein families. The dominant, secondary and minor categories account for 96% on average of a snake's venom composition. The four dominant protein families are: phospholipase A₂ (PLA₂), snake venom metalloprotease (SVMP), three-finger toxins (3FTx), and snake venom serine protease (SVSP). The six secondary protein families are: L-amino acid oxidase (LAAO), cysteine-rich secretory protein (CRiSP), C-type lectins (CTL), disintegrins (DIS), kunitz peptides (KUN), and natriuretic peptides (NP). Venom variation occurs at all taxonomic levels, including within populations. The reasons for venom variation are complex, as variation is not always associated with geographical variation in diet. The four dominant protein families appear to be the most important toxin families in human envenomation, being responsible for coagulopathy, neurotoxicity, myotoxicity and cytotoxicity. Proteomic techniques can be used to investigate the toxicological profile of a snake venom and hence identify key protein families for antivenom immunorecognition.

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.

Virus-like particles displaying conserved toxin epitopes stimulate polyspecific, murine antibody responses capable of snake venom recognition

Antivenom is currently the first-choice treatment for snakebite envenoming. However, only a low proportion of antivenom immunoglobulins are specific to venom toxins, resulting in poor dose efficacy and potency. We sought to investigate whether linear venom epitopes displayed on virus like particles can stimulate an antibody response capable of recognising venom toxins from diverse medically important species. Bioinformatically-designed epitopes, corresponding to predicted conserved regions of group I phospholipase A₂ and three finger toxins, were engineered for display on the surface of hepatitis B core antigen virus like particles and used to immunise female CD1 mice over a 14 weeks. Antibody responses to all venom epitope virus like particles were detectable by ELISA by the end of the immunisation period, although total antibody and epitope specific antibody titres were variable against the different epitope immunogens. Immunoblots using pooled sera demonstrated recognition of various venom components in a diverse panel of six elapid venoms, representing three continents and four genera. Insufficient antibody yields precluded a thorough assessment of the neutralising ability of the generated antibodies, however we were able to test polyclonal anti-PLA₂ IgG from three animals against the PLA₂ activity of Naja nigricollis venom, all of which showed no neutralising ability. This study demonstrates proof-of-principle that virus like particles engineered to display conserved toxin linear epitopes can elicit specific antibody responses in mice which are able to recognise a geographically broad range of elapid venoms.

Computer-Aided Analysis of West Sub-Saharan Africa Snakes Venom towards the Design of Epitope-Based Poly-Specific Antivenoms

Snakebite envenomation is a neglected tropical disease that causes over 100,000 deaths each year. The only effective treatment consists of antivenoms derived from animal sera, but these have been deemed with highly variable potency and are usually inaccessible and too costly for victims. The production of antivenoms by venom-independent techniques, such as the immunization with multi-epitope constructs, could circumvent those drawbacks. Herein, we present a knowledge-based pipeline to prioritize potential epitopes of therapeutic relevance from toxins of medically important snakes in West Sub-Saharan Africa. It is mainly based on sequence conservation and protein structural features. The ultimately selected 41 epitopes originate from 11 out of 16 snake species considered of highest medical importance in the region and 3 out of 10 of those considered as secondary medical importance. Echis ocellatus, responsible for the highest casualties in the area, would be covered by 12 different epitopes. Remarkably, this pipeline is versatile and customizable for the analysis of snake venom sequences from any other region of the world.

In Silico Design of a New Multi-Epitope Peptide-Based Vaccine Candidate Against Q Fever

Novel types of the vaccines with high immunogenicity and low risks, including epitope-based vaccines, are sought. Among zoonotic disease, Q fever caused by Coxiella burnetii is an important target due to numerous outbreaks and the pandemic potential. Here we present a synthetic multi-epitope vaccine against Coxiella burnetii. This vaccine was developed using immunoinformatics approach. Antigenic proteins were studied, and five T cell epitopes were selected. Antigenicity, allergenicity, and toxicity of the selected epitopes were evaluated using the VaxiJen 2.0, AllerTOP, and ToxinPred servers, respectively. Selected epitopes were joined in a peptide sequence, with the cholera toxin B subunit (CTXB) as an adjuvant. The affinity of the proposed vaccine to MHC I and II molecules was measured in a molecular docking study. Resultant vaccine has high antigenicity, stability, and a half-life compatible with utilization in vaccination programs. In conclusion, the validated epitope sequences may be used as a potential vaccine to ensure protection against Q fever agent.

Development of a Broad-Spectrum Antiserum against Cobra Venoms Using Recombinant Three-Finger Toxins

Three-finger toxins (3FTXs) are the most clinically relevant components in cobra (genus Naja) venoms. Administration of the antivenom is the recommended treatment for the snakebite envenomings, while the efficacy to cross-neutralize the different cobra species is typically limited, which is presumably due to intra-specific variation of the 3FTXs composition in cobra venoms. Targeting the clinically relevant venom components has been considered as an important factor for novel antivenom design. Here, we used the recombinant type of long-chain α-neurotoxins (P01391), short-chain α-neurotoxins (P60770), and cardiotoxin A3 (P60301) to generate a new immunogen formulation and investigated the potency of the resulting antiserum against the venom lethality of three medially important cobras in Asia, including the Thai monocled cobra (Naja kaouthia), the Taiwan cobra (Naja atra), and the Thai spitting cobra (Naja Siamensis) snake species. With the fusion of protein disulfide isomerase and the low-temperature settings, the correct disulfide bonds were built on these recombinant 3FTXs (r3FTXs), which were confirmed by the circular dichroism spectra and tandem mass spectrometry. Immunization with r3FTX was able to induce the specific antibody response to the native 3FTXs in cobra venoms. Furthermore, the horse and rabbit antiserum raised by the r3FTX mixture is able to neutralize the venom lethality of the selected three medically important cobras. Thus, the study demonstrated that the r3FTXs are potential immunogens in the development of novel antivenom with broad neutralization activity for the therapeutic treatment of victims involving cobra snakes in countries.

Diagnostic and Therapeutic Value of Aptamers in Envenomation Cases

It is now more than a century since Albert Calmette from the Institut Pasteur changed the world of envenomation by demonstrating that antibodies raised against animal venoms have the ability to treat human victims of previously fatal bites or stings. Moreover, the research initiated at that time effectively launched the discipline of toxicology, first leading to the search for toxic venom components, followed by the demonstration of venoms that also contained compounds of therapeutic value. Interest from pharmaceutical companies to treat envenomation is, however, declining, mainly for economic reasons, and hence, the World Health Organization has reclassified this public health issue to be a highest priority concern. While the production, storage, and safety of antivenom sera suffer from major inconveniences, alternative chemical and technological approaches to the problem of envenomation need to be considered that bypass the use of antibodies for toxin neutralization. Herein, we review an emerging strategy that relies on the use of aptamers and discuss how close—or otherwise—we are to finding a viable alternative to the use of antibodies for the therapy of human envenomation.

Abiotic Mimic of Endogenous Tissue Inhibitors of Metalloproteinases: Engineering Synthetic Polymer Nanoparticles for Use as a Broad-Spectrum Metalloproteinase Inhibitor

We describe a process for engineering a synthetic polymer nanoparticle (NP) that functions as an effective, broad-spectrum metalloproteinase inhibitor. Inhibition is achieved by incorporating three functional elements in the NP: a group that interacts with the catalytic zinc ion, functionality that enhances affinity to the substrate-binding pocket, and fine-tuning of the chemical composition of the polymer to strengthen NP affinity for the enzyme surface. The approach is validated by synthesis of a NP that sequesters and inhibits the proteolytic activity of snake venom metalloproteinases from five clinically relevant species of snakes. The mechanism of action of the NP mimics that of endogenous tissue inhibitors of metalloproteinases. The strategy provides a general design principle for synthesizing abiotic polymer inhibitors of enzymes.

Comprehensive Study of the Proteome and Transcriptome of the Venom of the Most Venomous European Viper: Discovery of a New Subclass of Ancestral Snake Venom Metalloproteinase Precursor-Derived Proteins

The nose-horned viper, its nominotypical subspecies Vipera ammodytes ammodytes (Vaa), in particular, is, medically, one of the most relevant snakes in Europe. The local and systemic clinical manifestations of poisoning by the venom of this snake are the result of the pathophysiological effects inflicted by enzymatic and nonenzymatic venom components acting, most prominently, on the blood, cardiovascular, and nerve systems. This venom is a very complex mixture of pharmacologically active proteins and peptides. To help improve the current antivenom therapy toward higher specificity and efficiency and to assist drug discovery, we have constructed, by combining transcriptomic and proteomic analyses, the most comprehensive library yet of the Vaa venom proteins and peptides. Sequence analysis of the venom gland cDNA library has revealed the presence of messages encoding 12 types of polypeptide precursors. The most abundant are those for metalloproteinase inhibitors (MPis), bradykinin-potentiating peptides (BPPs), and natriuretic peptides (NPs) (all three on a single precursor), snake C-type lectin-like proteins (snaclecs), serine proteases (SVSPs), P-II and P-III metalloproteinases (SVMPs), secreted phospholipases A₂ (sPLA₂s), and disintegrins (Dis). These constitute >88% of the venom transcriptome. At the protein level, 57 venom proteins belonging to 16 different protein families have been identified and, with SVSPs, sPLA₂s, snaclecs, and SVMPs, comprise ∼80% of all venom proteins. Peptides detected in the venom include NPs, BPPs, and inhibitors of SVSPs and SVMPs. Of particular interest, a transcript coding for a protein similar to P-III SVMPs but lacking the MP domain was also found at the protein level in the venom. The existence of such proteins, also supported by finding similar venom gland transcripts in related snake species, has been demonstrated for the first time, justifying the proposal of a new P-IIIe subclass of ancestral SVMP precursor-derived proteins.

Innovative Immunization Strategies for Antivenom Development

Snakes, scorpions, and spiders are venomous animals that pose a threat to human health, and severe envenomings from the bites or stings of these animals must be treated with antivenom. Current antivenoms are based on plasma-derived immunoglobulins or immunoglobulin fragments from hyper-immunized animals. Although these medicines have been life-saving for more than 120 years, opportunities to improve envenoming therapy exist. In the later decades, new biotechnological tools have been applied with the aim of improving the efficacy, safety, and affordability of antivenoms. Within the avenues explored, novel immunization strategies using synthetic peptide epitopes, recombinant toxins (or toxoids), or DNA strings as immunogens have demonstrated potential for generating antivenoms with high therapeutic antibody titers and broad neutralizing capacity. Furthermore, these approaches circumvent the need for venom in the production process of antivenoms, thereby limiting some of the complications associated with animal captivity and venom collection. Finally, an important benefit of innovative immunization approaches is that they are often compatible with existing antivenom manufacturing setups. In this review, we compile all reported studies examining venom-independent innovative immunization strategies for antivenom development. In addition, a brief description of toxin families of medical relevance found in snake, scorpion, and spider venoms is presented, as well as how biochemical, bioinformatic, and omics tools could aid the development of next-generation antivenoms.

The paraspecific neutralisation of snake venom induced coagulopathy by antivenoms

Snake envenoming causes several potentially lethal pathologies. The specific pathology is dictated by the toxin composition of venom, which varies by species, geography and ontogeny. This variation severely restricts the paraspecific efficacy of antivenoms used to treat snakebite victims. With a view to devising pathology-specific snakebite treatments, we assessed the procoagulant activity of 57 snake venoms and investigated the efficacy of various antivenoms. We find that procoagulant venoms act differentially on key steps of the coagulation cascade, and that certain monospecific antivenoms work in a previously unrecognised paraspecific manner to neutralise this activity, despite conventional assumptions of congener-restricted efficacy. Moreover, we demonstrate that the metal chelator EDTA is also capable of neutralising venom-induced lethality in vivo. This study illustrates the exciting potential of developing new, broad-spectrum, toxin-targeting antivenoms capable of treating key snakebite pathologies, and advocates a thorough re-examination of enzyme inhibiting compounds as alternative therapies for treating snakebite victims.

Identification of B cell recognized linear epitopes in a snake venom serine proteinase from the central American bushmaster Lachesis stenophrys

Snake venom serine proteinases are toxins that perturb hemostasis acting on proteins from the blood coagulation cascade, the fibrinolytic or the kallikrein-kinin system. Despite the relevance of these enzymes in envenomations by viper bites, the characterization of the antibody response to these toxins at the molecular level has not been previously addressed. In this work surface-located B cell recognized linear epitopes from a Lachesis stenophrys venom serine proteinase (UniProt accession number Q072L7) were predicted using an artificial neuronal network at the ABCpred server, the corresponding peptides were synthesized and their immunoreactivity was analyzed against a panel of experimental and therapeutic antivenoms. A molecular model of the L. stenophrys enzyme was built using as a template the structure of the D. acutus Dav-PA serine proteinase (Q9I8X1), which displays the highest degree of sequence similarity to the L. stenophrys enzyme among proteins of known 3D structure, and the surface-located epitopes were identified in the protein model using iCn3D. A total of 13 peptides corresponding to the surface exposed predicted epitopes from L. stenophrys serine proteinase were synthesized and, their reactivity with a rabbit antiserum against the recombinant enzyme and a panel of antivenoms was evaluated by a capture ELISA. Some of the epitopes recognized by monospecific and polyspecific antivenoms comprise sequences overlapping motifs conserved in viper venom serine proteinases. The identification and characterization of relevant epitopes recognized by B cells in snake venom toxins may provide valuable information for the preparation of immunogens that help in the production of improved therapeutic antivenoms.

Immune drug discovery from venoms

This review catalogues recent advances in knowledge on venoms as standalone therapeutic agents or as blueprints for drug design, with an emphasis on venom-derived compounds that affects the immune system. We discuss venoms and venom-derived compounds that affect total immune cell numbers, immune cell proliferation, immune cell migration, immune cell phenotype and cytokine secretion. Identifying novel compounds that 'tune' the system, up-regulating the immune response during infectious disease and cancer and down-regulating the immune response during autoimmunity, will greatly expand the tool kit of human immunotherapeutics. Targeting these pathways may also open therapeutic options that alleviate symptoms of envenomation. Finally, combining recent advances in venomics with progress in low cost, high-throughput screening platforms will no doubt yield hundreds of prototype immune modulating compounds in the coming years.

A Review and Database of Snake Venom Proteomes

Advances in the last decade combining transcriptomics with established proteomics methods have made possible rapid identification and quantification of protein families in snake venoms. Although over 100 studies have been published, the value of this information is increased when it is collated, allowing rapid assimilation and evaluation of evolutionary trends, geographical variation, and possible medical implications. This review brings together all compositional studies of snake venom proteomes published in the last decade. Compositional studies were identified for 132 snake species: 42 from 360 (12%) Elapidae (elapids), 20 from 101 (20%) Viperinae (true vipers), 65 from 239 (27%) Crotalinae (pit vipers), and five species of non-front-fanged snakes. Approximately 90% of their total venom composition consisted of eight protein families for elapids, 11 protein families for viperines and ten protein families for crotalines. There were four dominant protein families: phospholipase A₂s (the most common across all front-fanged snakes), metalloproteases, serine proteases and three-finger toxins. There were six secondary protein families: cysteine-rich secretory proteins, l-amino acid oxidases, kunitz peptides, C-type lectins/snaclecs, disintegrins and natriuretic peptides. Elapid venoms contained mostly three-finger toxins and phospholipase A₂s and viper venoms metalloproteases, phospholipase A₂s and serine proteases. Although 63 protein families were identified, more than half were present in <5% of snake species studied and always in low abundance. The importance of these minor component proteins remains unknown.

Snakebite envenoming

Snakebite envenoming is a neglected tropical disease that kills >100,000 people and maims >400,000 people every year. Impoverished populations living in the rural tropics are particularly vulnerable; snakebite envenoming perpetuates the cycle of poverty. Snake venoms are complex mixtures of proteins that exert a wide range of toxic actions. The high variability in snake venom composition is responsible for the various clinical manifestations in envenomings, ranging from local tissue damage to potentially life-threatening systemic effects. Intravenous administration of antivenom is the only specific treatment to counteract envenoming. Analgesics, ventilator support, fluid therapy, haemodialysis and antibiotic therapy are also used. Novel therapeutic alternatives based on recombinant antibody technologies and new toxin inhibitors are being explored. Confronting snakebite envenoming at a global level demands the implementation of an integrated intervention strategy involving the WHO, the research community, antivenom manufacturers, regulatory agencies, national and regional health authorities, professional health organizations, international funding agencies, advocacy groups and civil society institutions.

EC-PIII, a novel non-hemorrhagic procoagulant metalloproteinase: Purification and characterization from Indian Echis carinatus venom

Procoagulant snake venom toxins find extensive use as reagents in laboratory tests and diagnostic kits. In the present study we report a novel P-III class procoagulant SVMP, EC-PIII from Echis carinatus venom. EC-PIII was purified using a combination of gel-filtration and anion-exchange chromatography. It has a molecular mass of 110kDa and is a dimeric protein as determined by SDS-PAGE. DLS results show that the protein is homogenous and stable in solution. Peptide mass fingerprinting revealed that the peptides obtained show high homology to the other members of SVMP family. The enzymatic studies revealed that EC-PIII shows protease activity and is inhibited by metalloproteinase inhibitors such as EDTA. EC-PIII exhibits procoagulant effect under in-vitro conditions. Local toxicity studies revealed that EC-PIII is devoid of hemorrhagic as well as myotoxic activities. This is the first report of a non-hemorrhagic SVMP to be identified from Indian Echis carinatus venom. EC-PIII can find potential use in diagnostic and other therapeutic uses owing to its biochemical and pharmacological properties.

Pitfalls to avoid when using phage display for snake toxins

Antivenoms against bites and stings from snakes, spiders, and scorpions are associated with immunological side effects and high cost of production, since these therapies are still derived from the serum of hyper-immunized production animals. Biotechnological innovations within envenoming therapies are thus warranted, and phage display technology may be a promising avenue for bringing antivenoms into the modern era of biologics. Although phage display technology represents a robust and high-throughput approach for the discovery of antibody-based antitoxins, several pitfalls may present themselves when animal toxins are used as targets for phage display selection. Here, we report selected critical challenges from our own phage display experiments associated with biotinylation of antigens, clone picking, and the presence of amber codons within antibody fragment structures in some phage display libraries. These challenges may be detrimental to the outcome of phage display experiments, and we aim to help other researchers avoiding these pitfalls by presenting their solutions.

Snake Genome Sequencing: Results and Future Prospects

Snake genome sequencing is in its infancy—very much behind the progress made in sequencing the genomes of humans, model organisms and pathogens relevant to biomedical research, and agricultural species. We provide here an overview of some of the snake genome projects in progress, and discuss the biological findings, with special emphasis on toxinology, from the small number of draft snake genomes already published. We discuss the future of snake genomics, pointing out that new sequencing technologies will help overcome the problem of repetitive sequences in assembling snake genomes. Genome sequences are also likely to be valuable in examining the clustering of toxin genes on the chromosomes, in designing recombinant antivenoms and in studying the epigenetic regulation of toxin gene expression.

High-throughput immuno-profiling of mamba (Dendroaspis) venom toxin epitopes using high-density peptide microarrays

Snakebite envenoming is a serious condition requiring medical attention and administration of antivenom. Current antivenoms are antibody preparations obtained from the plasma of animals immunised with whole venom(s) and contain antibodies against snake venom toxins, but also against other antigens. In order to better understand the molecular interactions between antivenom antibodies and epitopes on snake venom toxins, a high-throughput immuno-profiling study on all manually curated toxins from Dendroaspis species and selected African Naja species was performed based on custom-made high-density peptide microarrays displaying linear toxin fragments. By detection of binding for three different antivenoms and performing an alanine scan, linear elements of epitopes and the positions important for binding were identified. A strong tendency of antivenom antibodies recognizing and binding to epitopes at the functional sites of toxins was observed. With these results, high-density peptide microarray technology is for the first time introduced in the field of toxinology and molecular details of the evolution of antibody-toxin interactions based on molecular recognition of distinctive toxic motifs are elucidated.

Screening, tandem expression and immune activity appraisal of Deinagkistrodon acutus (pit viper) venom mimotopes from a phage display 12-mer peptide library

OBJECTIVE

To design a specific polyclonal antibody against Deinagkistrodon acutus venom (DA-pAb) by immunizating New Zealand white rabbits.

RESULTS

The IgG fraction was purified by affinity chromatography, and specific antibodies were purified by immunoaffinity chromatography. Polyclonal antibodies were subjected to ELISA and western blotting to evaluate their immune reactivity. We identified the mimotopes by screening a phage display 12-mer peptide library against D. acutus venom. After three rounds of biopanning with DA-pAb, 30 positive clones were identified. Eighteen phage clones were sequenced, and their corresponding amino acid sequences were deduced. Additional immunoassays with the peptides and DA-pAb identified five sequences as possible epitopes. Recombinant antigens synthesized with the five epitopes were used for the immunization of BALB/c mice.

CONCLUSION

The antibodies induced by these peptides recognized the recombinant antigen and D. acutus venom and protected mice against the hemorrhagic effects of the venom.

Top-down venomics of the East African green mamba, Dendroaspis angusticeps, and the black mamba, Dendroaspis polylepis, highlight the complexity of their toxin arsenals

We report the characterization, by combination of high-resolution on-line molecular mass and disulfide bond profiling and top-down MS/MS analysis, of the venom proteomes of two congeneric African snake species of medical importance, Dendroaspis angusticeps (green mamba) and D. polylepis (black mamba). Each of these mamba venoms comprised more than two-hundred polypeptides belonging to just a few toxin families. Both venom proteomes are overwhelmingly composed of post-synaptically-acting short- and long-chain neurotoxins that potently inhibit muscle- and neuronal-type nicotinic acetylcholine receptors; muscarinic cardiotoxins; and dendrotoxins, that block some of the Kv1, n-class of K+ channels. However, the identity of the major proteins and their relative abundances exhibit marked interspecific variation. In addition, the greater resolution of the top-down venomic analytical approach revealed previously undetected protein species, isoforms and proteoforms, including the identification and precise location of modified lysine residues in a number of proteins in both venoms, but particularly in green mamba toxins. This comparative top-down venomic analysis unveiled the untapped complexity of Dendroaspis venoms and lays the foundations for rationalizing the notably different potency of green and black mamba lethal arsenals at locus resolution.

SIGNIFICANCE PARAGRAPH

We report the characterization, by combination of high-resolution on-line molecular mass and disulfide bond profiling and top-down MS/MS analysis, of the venom proteomes of two congeneric African snake species of medical importance, Dendroaspis angusticeps (green mamba) and D. polylepis (black mamba). Each of these mamba venoms comprised more than two-hundred polypeptides belonging to just a few toxin families. Both venom proteomes are overwhelmingly composed of post-synaptically-acting short- and long-chain neurotoxins that potently inhibit muscle- and neuronal-type nicotinic acetylcholine receptors; muscarinic cardiotoxins; and dendrotoxins, that block some of the Kv1, n-class of K+ channels. However, the identity of the major proteins and their relative abundances exhibit marked interspecific variation. In addition, the greater resolution of the top-down venomic analytical approach revealed previously undetected protein species, isoforms and proteoforms, including the identification and precise location of modified lysine residues in a number of proteins in both venoms, but particularly in green mamba toxins. This comparative top-down venomic analysis unveiled the untapped complexity of Dendroaspis venoms and lays the foundations for rationalizing the notably different potency of green and black mamba lethal arsenals at locus resolution.

Stabilising the Integrity of Snake Venom mRNA Stored under Tropical Field Conditions Expands Research Horizons

BACKGROUND

Snake venoms contain many proteinaceous toxins that can cause severe pathology and mortality in snakebite victims. Interestingly, mRNA encoding such toxins can be recovered directly from venom, although yields are low and quality is unknown. It also remains unclear whether such RNA contains information about toxin isoforms and whether it is representative of mRNA recovered from conventional sources, such as the venom gland. Answering these questions will address the feasibility of using venom-derived RNA for future research relevant to biomedical and antivenom applications.

METHODOLOGY/PRINCIPAL FINDINGS

Venom was extracted from several species of snake, including both members of the Viperidae and Elapidae, and either lyophilized or immediately added to TRIzol reagent. TRIzol-treated venom was incubated at a range of temperatures (4-37°C) for a range of durations (0-48 hours), followed by subsequent RNA isolation and assessments of RNA quantity and quality. Subsequently, full-length toxin transcripts were targeted for PCR amplification and Sanger sequencing. TRIzol-treated venom yielded total RNA of greater quantity and quality than lyophilized venom, and with quality comparable to venom gland-derived RNA. Full-length sequences from multiple Viperidae and Elapidae toxin families were successfully PCR amplified from TRIzol-treated venom RNA. We demonstrated that venom can be stored in TRIzol for 48 hours at 4-19°C, and 8 hours at 37°C, at minimal cost to RNA quality, and found that venom RNA encoded multiple toxin isoforms that seemed homologous (98-99% identity) to those found in the venom gland.

CONCLUSIONS/SIGNIFICANCE

The non-invasive experimental modifications we propose will facilitate the future investigation of venom composition by using venom as an alternative source to venom gland tissue for RNA-based studies, thus obviating the undesirable need to sacrifice snakes for such research purposes. In addition, they expand research horizons to rare, endangered or protected snake species and provide more flexibility to performing fieldwork on venomous snakes in tropical conditions.

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

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

A Heterologous Multiepitope DNA Prime/Recombinant Protein Boost Immunisation Strategy for the Development of an Antiserum against Micrurus corallinus (Coral Snake) Venom

Background

Envenoming by coral snakes (Elapidae: Micrurus), although not abundant, represent a serious health threat in the Americas, especially because antivenoms are scarce. The development of adequate amounts of antielapidic serum for the treatment of accidents caused by snakes like Micrurus corallinus is a challenging task due to characteristics such as low venom yield, fossorial habit, relatively small sizes and ophiophagous diet. These features make it difficult to capture and keep these snakes in captivity for venom collection. Furthermore, there are reports of antivenom scarcity in USA, leading to an increase in morbidity and mortality, with patients needing to be intubated and ventilated while the toxin wears off. The development of an alternative method for the production of an antielapidic serum, with no need for snake collection and maintenance in captivity, would be a plausible solution for the antielapidic serum shortage.

Methods and Findings

In this work we describe the mapping, by the SPOT-synthesis technique, of potential B-cell epitopes from five putative toxins from M. corallinus, which were used to design two multiepitope DNA strings for the genetic immunisation of female BALB/c mice. Results demonstrate that sera obtained from animals that were genetically immunised with these multiepitope constructs, followed by booster doses of recombinant proteins lead to a 60% survival in a lethal dose neutralisation assay.

Conclusion

Here we describe that the genetic immunisation with a synthetic multiepitope gene followed by booster doses with recombinant protein is a promising approach to develop an alternative antielapidic serum against M. corallinus venom without the need of collection and the very challenging maintenance of these snakes in captivity.

Coral snakes are a group of deadly venomous snakes that exhibit a characteristic red, yellow/white, and black coloured banding pattern. Accidents involving these snakes tend to be very severe or even lethal, causing peripheral nervous system depression with muscle paralysis and vasomotor instability. The only acceptable medical treatment for snakebite accidents is the administration of an antivenom, generally produced by immunising horses with the snake venom. Nonetheless, for what concerns the antielapidic serum production in Brazil, the total amount of venom available for horse immunisations is insufficient. This is mainly due to the small size of coral snake glands, their underground life style, combined with its very low survival rates in captivity. Moreover, cases of patients being intubated and ventilated as a consequence of antivenom shortage in USA have also been registered. In this work, we present an alternative method for the development of antielapidic serum, which does not rely upon snake capture. This serum was produced by a heterologous DNA prime—with a multiepitope DNA string coding for the most reactive epitopes from the most abundant toxins of M. corallinus, a coral snake which occupy highly populated areas in Brazil—followed by recombinant multiepitope protein boost immunisation of mice.

Discovery of toxin-encoding genes from the false viper Macropisthodon rudis, a rear-fanged snake, by transcriptome analysis of venom gland

Although rear-fanged snakes are often considered as non-threatening to humans, some species are lethal or medically hazardous. The toxin components and bioactivities of front-fanged snakes have been extensively studied; however, only limited research has explored the venoms of rear-fanged snakes. The false viper, Macropisthodon rudis, is widespread in southern China, but little is known about the toxins that this snake produces. Here, we analyzed the transcriptome of the venom gland of M. rudis using high-throughput sequencing with an illumina HiSeq 2000. The raw data were assembled and annotated using public databases. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways and gene ontology (GO) were analyzed. Using sequence comparisons, snake venom metalloproteinases (SVMPs) and a phosphodiesterase (PDE) were discovered in the venom gland of M. rudis.

Restriction and recruitment-gene duplication and the origin and evolution of snake venom toxins

Snake venom has been hypothesized to have originated and diversified through a process that involves duplication of genes encoding body proteins with subsequent recruitment of the copy to the venom gland, where natural selection acts to develop or increase toxicity. However, gene duplication is known to be a rare event in vertebrate genomes, and the recruitment of duplicated genes to a novel expression domain (neofunctionalization) is an even rarer process that requires the evolution of novel combinations of transcription factor binding sites in upstream regulatory regions. Therefore, although this hypothesis concerning the evolution of snake venom is very unlikely and should be regarded with caution, it is nonetheless often assumed to be established fact, hindering research into the true origins of snake venom toxins. To critically evaluate this hypothesis, we have generated transcriptomic data for body tissues and salivary and venom glands from five species of venomous and nonvenomous reptiles. Our comparative transcriptomic analysis of these data reveals that snake venom does not evolve through the hypothesized process of duplication and recruitment of genes encoding body proteins. Indeed, our results show that many proposed venom toxins are in fact expressed in a wide variety of body tissues, including the salivary gland of nonvenomous reptiles and that these genes have therefore been restricted to the venom gland following duplication, not recruited. Thus, snake venom evolves through the duplication and subfunctionalization of genes encoding existing salivary proteins. These results highlight the danger of the elegant and intuitive “just-so story” in evolutionary biology.

Testing the Toxicofera: comparative transcriptomics casts doubt on the single, early evolution of the reptile venom system

The identification of apparently conserved gene complements in the venom and salivary glands of a diverse set of reptiles led to the development of the Toxicofera hypothesis - the single, early evolution of the venom system in reptiles. However, this hypothesis is based largely on relatively small scale EST-based studies of only venom or salivary glands and toxic effects have been assigned to only some putative Toxicoferan toxins in some species. We set out to examine the distribution of these proposed venom toxin transcripts in order to investigate to what extent conservation of gene complements may reflect a bias in previous sampling efforts. Our quantitative transcriptomic analyses of venom and salivary glands and other body tissues in five species of reptile, together with the use of available RNA-Seq datasets for additional species, shows that the majority of genes used to support the establishment and expansion of the Toxicofera are in fact expressed in multiple body tissues and most likely represent general maintenance or "housekeeping" genes. The apparent conservation of gene complements across the Toxicofera therefore reflects an artefact of incomplete tissue sampling. We therefore conclude that venom has evolved multiple times in reptiles.

VTBuilder: a tool for the assembly of multi isoform transcriptomes

Background

Within many research areas, such as transcriptomics, the millions of short DNA fragments (reads) produced by current sequencing platforms need to be assembled into transcript sequences before they can be utilized. Despite recent advances in assembly software, creating such transcripts from read data harboring isoform variation remains challenging. This is because current approaches fail to identify all variants present or they create chimeric transcripts within which relationships between co-evolving sites and other evolutionary factors are disrupted. We present VTBuilder, a tool for constructing non-chimeric transcripts from read data that has been sequenced from sources containing isoform complexity.

Results

We validated VTBuilder using reads simulated from 54 Sanger sequenced transcripts (SSTs) expressed in the venom gland of the saw scaled viper, Echis ocellatus. The SSTs were selected to represent genes from major co-expressed toxin groups known to harbor isoform variants. From the simulated reads, VTBuilder constructed 55 transcripts, 50 of which had a greater than 99% sequence similarity to 48 of the SSTs. In contrast, using the popular assembler tool Trinity (r2013-02-25), only 14 transcripts were constructed with a similar level of sequence identity to just 11 SSTs. Furthermore VTBuilder produced transcripts with a similar length distribution to the SSTs while those produced by Trinity were considerably shorter. To demonstrate that our approach can be scaled to real world data we assembled the venom gland transcriptome of the African puff adder Bitis arietans using paired-end reads sequenced on Illumina’s MiSeq platform. VTBuilder constructed 1481 transcripts from 5 million reads and, following annotation, all major toxin genes were recovered demonstrating reconstruction of complex underlying sequence and isoform diversity.

Conclusion

Unlike other approaches, VTBuilder strives to maintain the relationships between co-evolving sites within the constructed transcripts, and thus increases transcript utility for a wide range of research areas ranging from transcriptomics to phylogenetics and including the monitoring of drug resistant parasite populations. Additionally, improving the quality of transcripts assembled from read data will have an impact on future studies that query these data. VTBuilder has been implemented in java and is available, under the GPL GPU V0.3 license, from http:// http://www.lstmed.ac.uk/vtbuilder.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-014-0389-8) contains supplementary material, which is available to authorized users.

A study of snake bite among children presenting to a paediatric ward in the main Teaching Hospital of North Central province of Sri Lanka

Background

Snake bite is a common problem in the North Central province of Sri Lanka. Common krait (Bungarus careuleus), Ceylon krait (Bungarus ceylonicus), Cobra (Naja naja), Russell’s viper (Daboia russelii), Saw-scaled viper (Echis carinatus) and Hump-nosed pit viper (Hypnale hypnale) are the six species of venomous land snakes in Sri Lanka. A significant number of adults and children are bitten by snakes every year. However, the majority of research studies done in Sri Lanka and other countries show adults bitten by snakes and studies describing children bitten by snakes are very sparse.

Methods

A descriptive cross sectional study was performed in the Teaching Hospital Anuradhapura in the North Central Province of Sri Lanka from May 2010 to 2011 May to describe the characteristics associated with cases of snake bite.

Results

There were 24 males and 20 females. The highest numbers of bites (48%) were in the range of ages 6-12 years. The majority of the bites occurred between 6 pm to 6 am (59%).The foot was the most common bitten site (48%). Out of all the venomous bites, the Hump-nosed pit viper (Hypnale hypnale) accounted for the highest number (44%) and Russell’s viper (Daboia ruselii) accounted for the second highest number (27%). A significant number of venomous bites occurred indoors while sleeping (22%). Antivenom serum was given to (39%) of venomous bites. Deaths occurred in (11%) of the venomous bites.

Conclusions

Hump-nosed pit viper (Hypnale hypnale) accounted for the highest number of venomous bites. Majority of the bites occurred between 6 pm and 6 am. Foot was the most common bitten site. A significant number of venomous bites occurred indoor while sleeping. Antivenom serum was given to a significant number of venomous bites. Educating the public on making their houses snake proof and using a torch when going out during night time will help in the prevention of getting bitten by snakes.

Prediction of an Epitope-based Computational Vaccine Strategy for Gaining Concurrent Immunization Against the Venom Proteins of Australian Box Jellyfish

Background:

Australian Box Jellyfish (C. fleckeri) has the most rapid acting venom known to in the arena of toxicological research and is capable enough of killing a person in less than 5 minutes inflicting painful, debilitating and potentially life-threatening stings in humans. It has been understood that C. fleckeri venom proteins CfTX-1, 2 and HSP70-1 contain cardiotoxic, neurotoxic and highly dermatonecrotic components that can cause itchy bumpy rash and cardiac arrest.

Subjects and Methods:

As there is no effective drug available, novel approaches regarding epitope prediction for vaccine development were performed in this study. Peptide fragments as nonamers of these antigenic venom proteins were analyzed by using computational tools that would elicit humoral and cell mediated immunity, were focused for attempting vaccine design. By ranking the peptides according to their proteasomal cleavage sites, TAP scores and IC50<250 nM, the predictions were scrutinized. Furthermore, the epitope sequences were examined by in silico docking simulation with different specific HLA receptors.

Results:

Interestingly, to our knowledge, this is the maiden hypothetical immunization that predicts the promiscuous epitopes with potential contributions to the tailored design of improved safe and effective vaccines against antigenic venom proteins of C. fleckeri which would be effective especially for the Australian population.

Conclusion:

Although the computational approaches executed here are based on concrete confidence which demands more validation and in vivo experiments to validate such in silico approach.

Generation and characterization of a recombinant chimeric protein (rCpLi) consisting of B-cell epitopes of a dermonecrotic protein from Loxosceles intermedia spider venom

A chimeric protein was constructed expressing three epitopes of LiD1, a dermonecrotic toxin from the venom of Loxosceles intermedia spider. This species is responsible for a large number of accidents involving spiders in Brazil. We demonstrated that the chimeric protein (rCpLi) generated is atoxic and that antibodies previously developed in rabbits against synthetic epitopes reactive with rCpLi in ELISA and immunoblot assays. The antibody response in rabbits against the rCpLi was evaluated by ELISA and we have detected an antibody response in all immunized animals. Overlapping peptides covering the amino acid sequence of the rCpLi were synthesized on a cellulose membrane, and their recognition by rabbit anti-rCpLi serum assessed. Three different antigenic regions were identified. The percentage of inhibition of the dermonecrotic, hemorrhagic and edematogenic activities caused by the recombinant protein LiD1r in naïve rabbits was assessed by pre-incubation with anti-rCpLi antibodies. Anti-rCpLi induced good dermonecrotic and hemorrhagic protection. The levels of protection were similar to the antiboides anti-LiD1r. In summary, we have developed a polyepitope recombinant chimeric protein capable of inducing multiple responses of neutralizing antibodies in a rabbit model. This engineered protein may be a promising candidate for therapeutic serum development or vaccination.

Complex cocktails: the evolutionary novelty of venoms

Venoms have evolved on numerous occasions throughout the animal kingdom. These 'biochemical weapon systems' typically function to facilitate, or protect the producing animal from, predation. Most venomous animals remain unstudied despite venoms providing model systems for investigating predator-prey interactions, molecular evolution, functional convergence, and novel targets for pharmaceutical discovery. Through advances in 'omic' technologies, venom composition data have recently become available for several venomous lineages, revealing considerable complexity in the processes responsible for generating the genetic and functional diversity observed in many venoms. Here, we review these recent advances and highlight the ecological and evolutionary novelty of venom systems.

Cross-neutralisation of the neurotoxic effects of Egyptian cobra venom with commercial tiger snake antivenom

Cross-neutralisation has been demonstrated for haemorrhagic venoms including Echis spp. and Cerastes spp. and for Australia elapid procoagulant toxins. A previous study showed that commercial tiger snake antivenom (TSAV) was able to neutralise the systemic effects of the Egyptian cobra, Naja haje, in vivo but it is unclear if this was true cross-neutralisation. The aim of the current study was to determine whether TSAV can neutralise the in vitro neurotoxic effects of N. haje venom. Both Notechis scutatus (10 μg/ml) and N. haje (10 μg/ml) venoms caused inhibition of indirect (supramaximal V, 0.1 Hz, 0.2 msec.) twitches of the chick biventer cervicis nerve-muscle preparation with t(90) values (i.e. the time to produce 90% inhibition of the original twitch height) of 26 ± 1 min. (n = 4) and 36 ± 4 min.; (n = 4). This effect at 10 μg/ml was significantly attenuated by the prior addition of TSAV (5 U/ml). A comparison of the reverse-phase HPLC profiles of both venoms showed some similarities with peak elution times, and SDS-PAGE analysis elucidated comparable bands across both venoms. Further analysis using Western immunoblotting indicated TSAV was able to detect N. haje venom, and enzyme immunoassay showed that in-house biotinylated polyclonal monovalent N. scutatus antibodies were able to detect N. haje venom. These findings demonstrate cross-neutralisation between different and geographically separated snakes supporting potential immunological similarities in snake toxin groups for a large range of snakes. This provides more evidence that antivenoms could be developed against specific toxin groups to cover a large range of snakes.

Identification of linear B-cell epitopes on myotoxin II, a Lys49 phospholipase A₂ homologue from Bothrops asper snake venom

Knowledge on toxin immunogenicity at the molecular level can provide valuable information for the improvement of antivenoms, as well as for understanding toxin structure-function relationships. The aims of this study are two-fold: first, to identify the linear B-cell epitopes of myotoxin II from Bothrops asper snake venom, a Lys49 phospholipase A₂ homologue; and second, to use antibodies specifically directed against an epitope having functional relevance in its toxicity, to probe the dimeric assembly mode of this protein in solution. Linear B-cell epitopes were identified using a library of overlapping synthetic peptides spanning its complete sequence. Epitopes recognized by a rabbit antiserum to purified myotoxin II, and by three batches of a polyvalent (Crotalidae) therapeutic antivenom (prepared in horses immunized with a mixture of B. asper, Crotalus simus, and Lachesis stenophrys venoms) were mapped using an enzyme-immunoassay based on the capture of biotinylated peptides by immobilized streptavidin. Some of the epitopes identified were shared between the two species, whereas others were unique. Differences in epitope recognition were observed not only between the two species, but also within the three batches of equine antivenom. Epitope V, located at the C-terminal region of this protein, is known to be relevant for toxicity and neutralization. Affinity-purified rabbit antibodies specific for this site were able to immunoprecipitate myotoxin II, suggesting that the two copies of epitope V are simultaneously available to antibody binding, which would be compatible with the mode of dimerization known as "conventional" dimer.

Research strategies to improve snakebite treatment: challenges and progress

Antivenom is an effective treatment of snakebite but, because of the complex interplay of fiscal, epidemiological, therapeutic efficacy and safety issues, the mortality of snakebite remains unacceptably high. Efficiently combating this high level of preventable death amongst the world's most disadvantaged communities requires the globally-coordinated action of multiple intervention programmes. This is the overall objective of the Global Snakebite Initiative. This paper describes the challenges facing the research community to develop snakebite treatments that are more efficacious, safe and affordable than current therapy.

Snake venomics and venom gland transcriptomic analysis of Brazilian coral snakes, Micrurus altirostris and M. corallinus

The venom proteomes of Micrurus altirostris and M. corallinus were analyzed by combining snake venomics and venom gland transcriptomic surveys. In both coral snake species, 3FTx and PLA(2) were the most abundant and diversified toxin families. 33 different 3FTxs and 13 PLA(2) proteins, accounting respectively for 79.5% and 13.7% of the total proteins, were identified in the venom of M. altirostris. The venom of M. corallinus comprised 10 3FTx (81.7% of the venom proteome) and 4 (11.9%) PLA(2) molecules. Transcriptomic data provided the full-length amino acid sequences of 18 (M. altirostris) and 10 (M. corallinus) 3FTxs, and 3 (M. altirostris) and 1 (M. corallinus) novel PLA(2) sequences. In addition, venom from each species contained single members of minor toxin families: 3 common (PIII-SVMP, C-type lectin-like, L-amino acid oxidase) and 4 species-specific (CRISP, Kunitz-type inhibitor, lysosomal acid lipase in M. altirostris; serine proteinase in M. corallinus) toxin classes. The finding of a lipase (LIPA) in the venom proteome and in the venom gland transcriptome of M. altirostris supports the view of a recruitment event predating the divergence of Elapidae and Viperidae more than 60 Mya. The toxin profile of both M. altirostris and M. corallinus venoms points to 3FTxs and PLA(2) molecules as the major players of the envenoming process. In M. altirostris venom, all major, and most minor, 3FTxs display highest similarity to type I α-neurotoxins, suggesting that these postsynaptically acting toxins may play the predominant role in the neurotoxic effect leading to peripheral paralysis, respiratory arrest, and death. M. corallinus venom posesses both, type I α-neurotoxins and a high-abundance (26% of the venom proteome) protein of subfamily XIX of 3FTxs, exhibiting similarity to bucandin from Malayan krait, Bungarus candidus, venom, which enhances acetylcholine release presynaptically. This finding may explain the presynaptic neurotoxicity of M. corallinus venom and the lack of this effect in M. altirostris venom. The anti-Micrurus (corallinus and frontalis) antivenom produced by Instituto Butantan quantitatively immunodepleted the minor toxins from M. altirostris and M. corallinus venoms but showed impaired crossreactivity towards their major 3FTx and PLA(2) molecules. The structural diversity of 3FTxs among Micrurus sp. may underlay the impaired cross-immunoreactivity of the Butantan antivenom towards M. altirostris and M. corallinus toxins, hampering the possibility to raise an antivenom against a simple venom mixture exhibiting paraspecific neutralization of other Micrurus venoms.