Causes and Consequences of Snake Venom Variation

Venom variation and ontogenetic changes in the Crotalus molossus complex: Insights into composition, activities, and antivenom neutralization

The Crotalus molossus complex consists of five to seven phylogenetically related lineages of black-tailed rattlesnakes widely distributed in Mexico. While previous studies have noted venom variation within specific lineages of the Crotalus molossus complex, a comprehensive characterization of interspecific and ontogenetic venom variations, their functional implications, and the neutralizing ability of the Mexican antivenom against these variants remains largely unexamined. Herein, using two proteomic approaches for five lineages (C. basiliscus, C. m. molossus, C. m. nigrescens, C. m. oaxacus, and C. ornatus) of the C. molossus complex we characterized the number of toxins and their relative abundance in the venom of individuals of varying sizes. All five lineages undergo ontogenetic venom composition shifts associated with snake length. However, the pattern of ontogenetic shifts varied among lineages. In some lineages, these shifts led to significant differences in proteolytic, phospholipase A2, and fibrinogenolytic activities. Venom in smaller C. basiliscus, C. m. nigrescens, and C. m. oaxacus individuals had lower LD50 values (more lethal) in mice. Whereas the venom lethality of C. m. nigrescens (both juvenile and adult) and C. m. oaxacus (adult) was several times higher in a mammalian (mouse) model than in a reptilian (iguana) model. Antivipmyn® showed different neutralizing potencies toward venom pools. Overall, our results indicated that even among closely related rattlesnake lineages, venom phenotypes may vary greatly, impacting their function and the efficacy of antivenom neutralization.

Beyond sexual maturity: Importance of dietary changes in venom variation in Vipera ammodytes

Identifying individual age and size is crucial in venom research to understand potential phenotypic changes. When studying venom ontogeny, juveniles and adults are often determined by size at sexual maturity. However, in gape-limited predators such as snakes, venom shifts may occur earlier, coinciding with an increase in jaw size that allows the intake of larger prey. This study explored venom variation in Vipera ammodytes along the snout-vent length (SVL), linking these changes to dietary shifts and reproductive status. A total of 57 venom samples from two populations were analysed using chip electrophoresis (CE) and MALDI-TOF mass spectrometry. Individuals were categorised into three groups: immature individuals feeding on lizards (<300 mm SVL), immature individuals feeding on lizards but start including mammals in their diet (between 300 and 440 mm), and mature individuals feeding on mammals and lizards (>440 mm). Significant venom composition changes around 300 mm SVL were observed, aligning with a dietary shift marked by increased mammalian prey intake and preceding sexual maturity. This finding highlights the need to use SVL as a metric for accurate venom analysis along ontogeny. Our results indicate that when pooling venom samples is necessary, allocating individuals to age categories should be based on dietary shifts rather than sexual maturity. Additionally, CE and MALDI-TOF MS proved effective in detecting ontogenetic venom changes, offering a fast and affordable approach to venom profiling. This study emphasises the importance of integrating natural history data in venom studies to better understand the ecological and evolutionary drivers of venom adaptation.

Epidemiology, molecular characterization, and risk factors of Acanthamoeba spp., Blastocystis spp., and Cyclospora spp. infections in snakes in China

Snakes are widely farmed in China for medicinal purposes and as pets worldwide. Acanthamoeba spp., Blastocystis spp., and Cyclospora spp. are significant zoonotic pathogens frequently discovered in various animals, causing diseases with global public health implications. However, their prevalence and zoonotic potential in snakes remain poorly understood. In this study, 812 snake faecal samples were collected across 28 China provinces. The partial small subunit (SSU) rRNA gene was amplified using polymerase chain reaction (PCR) to assess evolutionary relationships and genetic characterization. Detection rates for Acanthamoeba spp., Blastocystis spp., and Cyclospora spp. were 6.40 %, 3.33 %, and 2.71 %, respectively. Sequencing and phylogenetic analysis revealed that Cyclospora isolates were closely related to those found in humans and cattle. Subtyping for Blastocystis species identified two zoonotic subtypes (ST4, ST6) and four host-specific subtypes (ST10, ST15, ST21, ST42). Multiple Acanthamoeba genotypes were detected, including T4, T11, and T13. Furthermore, species, age, and living conditions are key risk factors. This study provides valuable insights into these infections in snakes and underscores the need for proper hygiene and One Health measures to reduce zoonotic transmission and environmental contamination.

Emerging Trends in Snake Venom-Loaded Nanobiosystems for Advanced Medical Applications: A Comprehensive Overview

Advances in medical nanobiotechnology have notably enhanced the application of snake venom toxins, facilitating the development of new therapies with animal-derived toxins. The vast diversity of snake species and their venom complexities underline the need for ongoing research. This review is dedicated to exploring the integration of snake venom with nanoparticles to enable their use in human therapies aiming to develop treatments. The complex mixture of snake venom not only inflicts significant pathological effects but also offers valuable insights for the creation of innovative therapies, particularly in the realm of nanobiotechnology. Nanoscale encapsulation not only mitigates the inherent toxicity of snake venom but also amplifies their antitumoral, antimicrobial, and immunomodulatory properties. The synergy between venom-derived macromolecules and nanotechnology offers a novel pathway for augmenting the efficacy and safety of conventional antivenom therapies, extending their applicability beyond treating bites to potentially addressing a myriad of health issues. In conclusion, nanotechnology presents a compelling therapeutic frontier that promises to improve current treatment modalities and ameliorate the adverse effects associated with venomous snakebites.

A genus-wide study on venom proteome variation and phospholipase A2 inhibition in Asian lance-headed pit vipers (genus: Trimeresurus)

High molecular weight proteins are present abundantly in viperid venoms. The amino acid sequence can be highly variable, contributing to the structure and function diversity of snake venom protein. However, this variability remains poorly understood in many species. The study investigated the venom protein variability in a distinct clade of Asian pit vipers (Trimeresurus species complex) through comparative proteomics, applying gel electrophoresis (SDS-PAGE), liquid chromatography-tandem mass spectrometry (LCMS/MS), and bioinformatic approaches. The proteomes revealed a number of conserved protein families, within each are variably expressed protein paralogs that are unrelated to the snake phylogeny and geographic origin. The expression levels of two major enzymes, i.e., snake venom serine proteinase and metalloproteinase, correlate weakly with procoagulant and hemorrhagic activities, implying co-expression of other functionally versatile toxins in the venom. The phospholipase A2 (PLA2) abundance correlates strongly with its enzymatic activity, and a unique phenotype was discovered in two species expressing extremely little PLA2. The commercial mono-specific antivenom effectively neutralized the venoms' procoagulant and hemorrhagic effects but failed to inhibit the PLA2 activities. Instead, the PLA2 activities of all venoms were effectively inhibited by the small molecule inhibitor varespladib, suggesting its potential to be repurposed as a highly potent adjuvant therapeutic in snakebite envenoming.

Ontogeny, not prey availability, underlies allopatric venom variability in insular and mainland populations of Vipera ammodytes

Allopatric populations living under distinct ecological conditions are excellent systems to infer factors underlying intraspecific venom variation. The venom composition of two populations of Vipera ammodytes, insular with a diet based on ectotherms and mainland with a diet based on ectotherms and endotherms, was compared considering the sex and age of individuals. Ten toxin families, dominated by PLA2, svMP, svSP, and DI, were identified through a bottom-up approach. The venom profiles of adult females and males were similar. Results from 58 individual SDS-PAGE profiles and venom pool analysis revealed significant differences between juveniles compared to subadults and adults. Two venom phenotypes were identified: a juvenile svMP-dominated and KUN-lacking phenotype and an adult PLA2/svMP-balanced and KUN-containing phenotype. Despite differences in prey availability (and, therefore, diet) between populations, no significant differences in venom composition were found. As the populations are geographically isolated, the lack of venom diversification could be explained by insufficient time for natural selection and/or genetic drift to act on the venom composition of island vipers. However, substantial differences in proteomes were observed when compared to venoms from geographically distant populations inhabiting different conditions. These findings highlight the need to consider ecological and evolutionary processes when studying venom variability. SIGNIFICANCE: This study provides the first comprehensive analysis of the venom composition of two allopatric populations of Vipera ammodytes, living under similar abiotic (climate) but distinct biotic (prey availability) conditions. The ontogenetic changes in venom composition, coupled with the lack of differences between sex and between populations, shed light on the main determinants of venom evolution in this medically important snake. Seven new proteomes may facilitate future comparative studies of snake venom evolution. This study highlights the importance of considering ecological and evolutionary factors to understand snake venom variation.

Genetic variability in snake venom and its implications for antivenom development in sub-Saharan Africa

Snake venom, a complex mixture of proteins, has attracted human attention for centuries due to its associated mortality, morbidity and other therapeutic properties. In sub-Saharan Africa (SSA), where snakebites pose a significant health risk, understanding the genetic variability of snake venoms is crucial for developing effective antivenoms. The wide geographic distribution of venomous snake species in SSA countries demonstrates the need to develop specific and broad antivenoms. However, the development of broad antivenoms has been hindered by different factors, such as antivenom cross-reactivity and polygenic paratopes. While specific antivenoms have been hindered by the numerous snake species across the SSA region, current antivenoms, such as SAIMR polyvalent and Premium Serums & Vaccines, exhibit varying degrees of cross-reactivity. Such ability to cross-react enables the antivenoms to target multiple components from the different snake species. The advent of biotechnological innovations, including recombinant antibodies, small-molecule drugs, monoclonal antibodies and synthetic antivenoms, presents options for eliminating limitations associated with traditional plasma-derived antivenoms. However, challenges still persist, especially in SSA, in addressing genetic variability, as evidenced by inadequate testing capacity and limited genomic research facilities. This comprehensive review explores the genetic variability of snake venoms in SSA, emphasizing the venom composition of various snake species and their interactions. This information is critical in developing multiple strategies during antivenom development. Finally, it offers information concerning the need for extensive collaborative engagements, technological advancements and comprehensive genomic evaluations to produce targeted and effective antivenoms.

Characteristics of snakebite patients due to Naja samarensis in the Philippines: a prospective hospital-based study

BACKGROUND

Little is known about snakebites by Naja samarensis, a species unique to the Philippines. The aim here is to describe the clinical and epidemiological characteristics of patients bitten by this medically important cobra in the Eastern Visayas.

METHODS

A hospital-based prospective study analysed the features of snakebite patients attending Eastern Visayas Medical Center between June 2022 and May 2023. Logistic regression analysis identified the factors associated with severity.

RESULTS

A total of 175 snakebite patients with five fatalities were included. Naja samarensis was most commonly implicated (n=49, 28.0%), although it could be definitively identified, by examining photographs of the snake responsible, in only four cases. The N. samarensis bites occurred in grass or rice fields, in daytime, and during farming activities, but the people bitten were most frequently students (34.7%) who were bitten at home (36.7%). Patients bitten by N. samarensis often presented with cytotoxic (63.3%) and neurotoxic signs (46.9%). Traditional remedies were common, resulting in delayed presentation to the hospital. Bites by N. samarensis, and older age (>44 y) were independently associated with severity (adjusted OR of 10.33 and 7.89, respectively).

CONCLUSION

Naja samarensis is a major cause of severe snakebites in this region. Pre-hospital treatment frequently involves wasted time and unproven traditional methods. Enhancement of public awareness is urgently needed. Development of a diagnostic test for species identification is warranted to improve future surveys and management.

Fibrinogenolytic potential of venoms of medically important Brazilian snakes

One of the main clinical manifestations presented by victims of snake bite envenoming are coagulation disorders. Considering that fibrinogen is a key molecule for crosslinked fibrin clot formation, the objective of this work was the quantitative analysis of the fibrinogenolytic activity of snakes of medical importance in Brazil and neutralization by specific antivenom. For this, pools of three genera of medical importance (Bothrops, Crotalus and Lachesis) that are used for the production of antivenom were used, and three pools of species of the genus Bothrops that are not part of the pool for the production of antivenom. The Lachesis pool had the highest fibrinogenolytic activity, even demonstrating partial cleavage (42.9 % consumption) of the fibrinogen gamma chain. The Bothrops genus venom pools have shown subtle variations between them. The Crotalus pool, despite not showing total cleavage of any fibrinogen chain, began cleavage of fibrinogen by the beta chain. The specific antivenoms used were able to delay the cleavage of fibrinogen in all the venoms used, which could be the first step towards implementing previous in vitro tests to analyze the quality of the batches of antivenoms produced, thus potentially reducing the use of animals used in this process.

Developing and applying a training needs analysis tool for healthcare workers managing snakebite envenoming: A cross-sectional study in Eswatini

A considerable number of patients present to hospitals in Eswatini each year following bites by venomous snakes. Effectively diagnosing and treating patients with snakebite envenoming requires healthcare workers to have a variety of generic and snakebite-specific medical skills. In several countries, however, healthcare workers have been found to have limited skills in managing snakebite patients. We used the Delphi method to adapt the Hennessy-Hicks training needs analysis questionnaire to the context of snakebite envenoming and subsequently used the adapted questionnaire to assess the self-perceived training needs of 90 healthcare workers from ten hospitals in Eswatini. Two-thirds (63%) of participants were nursing staff and one third (34%) medical doctors. Overall, 74% of healthcare workers had previously received training on snakebite. Although a training need was reported for all skills included in the survey, the extent of the training need varied between different skills and groups of healthcare workers. The highest average training need was registered in the domains 'research and audit' and 'clinical tasks' with the latter accounting for nine of the ten skills with the highest training need. Nurses reported a higher training need than doctors, especially for clinical tasks. Receiving snakebite training before as well as after obtaining the primary qualification was associated with the lowest average training need, particularly in clinical skills. Ninety-three percent of interviewed healthcare workers would welcome more frequent training opportunities on the clinical management of snakebite patients. This newly developed snakebite training needs analysis tool can aid in adapting training initiatives to a dynamic and evolving healthcare workforce and it is designed to be transferrable to snakebite endemic settings worldwide.

Geographic variation in stonefish (Synanceia spp.) venom

Stonefish (Synanceia spp.) possess a medically significant venom and are widely distributed throughout the Indo-Pacific. Yet, little is known about how the ecology of these animals may influence their venom. The aim of this study was to explore the effect of species and geographic location on stonefish venom composition. We collected the venom of Synanceia horrida (Estuarine Stonefish) and Synanceia verrucosa (Reef Stonefish) from various locations across Australia (Cairns, Brisbane, Caloundra, and Onslow), and Southeast Asia (Kota Kinabalu, and Cebu) and analysed these samples using SDS-PAGE, FPLC, and HPLC. Stonefish have a complex venom comprised of numerous components. Stonefish venom exhibited both similarities and variations in composition within species between geographically isolated populations, as well as between species in a single location. We speculate that the observed geographic and interspecific trends may be driven by similarities and differences in the selective pressures faced by these animals, particularly those associated with predator dynamics. The findings of this study have furthered our understanding of the ecology of stonefish and their toxins.

Snake venom weakens neurovascular integrity and promotes vulnerability to neuroinflammation

Snake envenomation poses significant medical challenges, particularly in subtropical and tropical regions, with long-term impacts on neurovascular integrity and neuroinflammation remaining underexplored. This study investigates the effects of venom from four species of venomous snakes in southern China-Zhoushan Cobra (Naja atra, NA), Many-banded Krait (Bungarus multicinctus, BM), Five-paced Pit Viper (Deinagkistrodon acutus, DA), and Chinese Moccasin (Protobothrops mucrosquamatus, PM) - on the blood-brain barrier (BBB) and chronic neuroinflammation. Using mass spectrometry, we analyzed venom protein compositions, while cytotoxic effects on mouse brain endothelial cells (bEND.3) were evaluated to determine IC50 values. In vitro BBB models and in vivo experiments in C57BL/6J mice revealed that NA venom, in particular, significantly compromised BBB integrity without inducing large-scale apoptosis, leading to persistent BBB disruption characterized by increased permeability and selective degradation of extracellular matrix and tight junction proteins. Moreover, to simulate secondary infections that often occur following snakebites, we combined venom exposure with lipopolysaccharide (LPS) treatment, which exacerbated neuroinflammatory responses by intensifying microglial activation and promoting a pro-inflammatory phenotype. These findings highlight the role of snake venom in compromising neurovascular integrity and promoting vulnerability to chronic neuroinflammation, emphasizing the need for further research into venom-induced neuroinflammatory pathways and their potential as therapeutic targets.

Mapping evidence on the regulations affecting accessibility, availability and management of snake antivenom globally: a scoping review protocol

INTRODUCTION

Snakebite envenomation has been declared a neglected tropical disease by the WHO since 2017. The disease is endemic in affected areas due to the lack of availability and access to antivenom, despite it being the standard treatment for snakebites. This challenge is perpetuated by the shortcomings of the regulatory systems and policies governing the management of antivenoms. This study aims to map the evidence about regulations of snake antivenom globally and identify gaps in the literature. This protocol provides an overview of the methodology and analysis which will be used to conduct the scoping review.

METHOD AND ANALYSIS

The scoping review follows the guidelines from the Arksey and O'Malley framework for scoping reviews and will be reported using Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. A search strategy was developed with assistance from a health sciences librarian, and the search was done using six relevant databases. The databases used are PubMed, SCOPUS, ProQuest Central, Africa Wide Web, Academic Search Output and Web of Science. Articles in the English language and between 2009 and 2023 were included. The search results were collated, duplicates were removed and results were exported to Rayyan (https://www.rayyan.ai/) for screening. The initial screening for titles and abstracts is currently in progress, and thereafter the second round of screening will be done for full texts. Data extraction will be done using Google Forms. The results of the review will be synthesised using quantitative and qualitative tools.

ETHICS AND DISSEMINATION

This review will provide guidance for studies investigating regulatory gaps globally and inform future policies governing antivenom management. Ethics approval for the complete postgraduate project was obtained from the University of Pretoria Research Ethics Committee. The review will be published in a scientific journal, and findings will also be disseminated using conference presentations.

TRIAL REGISTRATION

This review has been registered on Open Science Framework (OSF): https://osf.io/54zja.

Age Is Just a Number: Ontogenetic Conservation in Activation of Blood Clotting Factors VII, X, and XII by Caucasus Blunt-Nosed Viper (Macrovipera lebetina obtusa) Venoms

This study examined the pathophysiological effects of venoms from neonate and adult specimens of the viperid snake Macrovipera lebetina obtusa, focusing on their ability to activate various blood clotting factors in human plasma. All venoms exhibited strong procoagulant properties. In concentration-response tests, the clotting potency of the neonate venoms fell within the range of their parents' maximum clotting velocities and areas under the curve. Intriguingly, females were more potent than males within each age group, but this requires a larger sample size to confirm. Antivenom neutralization efficacy was equipotent across age groups. The venoms potently activated Factor X (FX) robustly, consistent with previous knowledge of this genus. For the first time, the ability to activate Factors VII (FVII) and XII (FXII) was identified in this genus, with FXII exhibiting particularly strong activation. The study found no significant ontogenetic variation in procoagulant venom potency on human plasma, convergent with the Daboia genus, the other large-bodied lineage within the Palearctic viperid clade. However, the activation of FXII and FVII reveals previously undocumented pathways in the procoagulant activity of these venoms, contributing to the broader understanding of venom evolution and its clinical impacts. These findings have implications for venom biodiscovery and the development of antivenoms, highlighting the complexity of clotting factor activation beyond traditional investigations that have myopically focused upon FX and prothrombin pathways, thereby underscoring the importance of exploring additional clotting factors.

Venom variation among the three subspecies of the North African mountain viper Vipera monticola Saint Girons 1953

The North African mountain viper (Vipera monticola) is a medically relevant venomous snake distributed in Morocco, Algeria, and Tunisia. Three subspecies of V. monticola, exhibiting differences in morphotypes and dietary regimes, are currently recognised: V. m. monticola, V. m. atlantica, and V. m. saintgironsi. Through the application of snake venomics, we analysed the venoms of specimens of Moroccan origin belonging to each of the three subspecies. Snake venom metalloproteinases (svMP), snake venom serine proteases (svSP), C-type lectin and C-type lectin-related proteins (CTL), and phospholipases A2 (PLA2) were predominant, with PLA2 being the most abundant toxin family overall. Disintegrins (DI) and cysteine-rich secretory proteins (CRISP) were exclusive to V. m. monticola and V. m. atlantica, while l-amino-acid oxidases (LAAO) were only found in V. m. saintgironsi. The differences detected in the venom profiles, as well as in presence/absence and relative abundances of toxin families, indicate the occurrence of intraspecific venom variation within V. monticola. The identified patterns of venom similarity between subspecies seem to align more with their phylogenetic relationships than with the reported differences in their feeding habits.

Snakebite-induced reversible cerebral vasoconstriction syndrome: Report of three cases

Envenomings from Russell's viper typically result in local tissue damage and bleeding complications, but the bites from common krait and cobra primarily cause neurotoxic effects. While most symptoms can be treated with appropriate antivenom, additional support is necessary for several snakebite victims to tackle a broad range of unusual complications that they develop following bites. Reversible vasoconstriction syndrome (RCVS), characterised by the constriction of cerebral arteries, is a rare but serious issue, presenting with severe headaches and, in extreme cases, haemorrhagic/ischaemic stroke. This report presents three cases of RCVS in snakebite victims following Russell's viper, krait and cobra bites. The patients were admitted to the hospital with neurological and/or haematological complications, and they were treated with polyvalent antivenom. After two days of antivenom treatment, all the patients developed intense headaches that lasted for several hours and failed to respond to commonly used analgesics. While the physical, laboratory and computed tomography examinations were normal, the RCVS was diagnosed with multimodal magnetic resonance angiography. All patients were successfully treated with oral nimodipine, and during their follow-ups, physical and laboratory examinations were unremarkable, and the magnetic resonance imaging confirmed the reversal of RCVS. To achieve positive outcomes in patients, clinicians must swiftly identify such rare complications and make accurate diagnoses to provide prompt treatments. Overall, this report presents an unusual complication of RCVS in snakebite patients and appropriate diagnosis and treatment approaches to tackle this condition.

The Venom of Vipera ammodytes ammodytes: Proteomics, Neurotoxic Effect and Neutralization by Antivenom

Deep proteomic analyses identified, in total, 159 master proteins (with 1% FDR and 2 unique peptides) from 26 protein families in the venom of Vipera ammodytes ammodytes (Vaa). Data are available via ProteomeXchange with the identifier PXD056495. The relative abundance of PLA2s is 11.60% of the crude venom, of which 4.35% are neurotoxic Ammodytoxins (Atxs). The neurotoxicity of the venom of Vaa and the neutralizing effect of the antivenom were tested on the neuromuscular preparation of the diaphragm (NPD) of rats. The activity of PLA2 in the venom of Vaa and its neutralization by the antivenom were determined under in vitro conditions. The Vaa venom leads to a progressive decrease in NPD contractions. We administered pre-incubated venom/antivenom mixtures at various ratios of 1:2, 1:10 and 1:20 (w/w) and observed the effects of these mixtures on NPD contractions. The results show that the mean effective time (ET50) for NPD contractions with the 1:20 mixture is highly significantly different (p < 0.001) from the ET50 for the venom and the ET50 for the 1:2 and 1:10 mixture ratios. We also found a highly significant (p < 0.001) reduction in Na+/K+-ATPase activity in the NPD under the influence of the venom. The reduction in the activity of this enzyme was reversible by the antivenom. Under in vitro conditions, we have achieved the complete neutralization of PLA2 by the antivenom. In conclusion, the antivenom abolished the venom-induced progressive decrease in NPD contractions in a concentration-dependent manner. Antivenom with approximately the same mass proportion almost completely restores Na+/K+-ATPase activity in the NPD and completely neutralizes the PLA2 activity of the venom in vitro.

Elusive elapids: biogeographic venom variation in Indian kraits and its repercussion on snakebite therapy

Snakebite is a major public health concern in many parts of the world, including India, where over 58,000 deaths occur annually due to snake envenoming. The common krait (Bungarus caeruleus) is responsible for the second-highest number of snakebite-related mortalities in the country. However, despite its notoriety, little is known about its venom ecology, functions and compositional variation across bioclimatic zones, partly because these nocturnal snakes are highly elusive, making it difficult to find them in the wild. We aim to address this knowledge gap by characterising the venom composition and toxicity profiles of the pan-Indian populations (n = 8) of B. caeruleus using a combination of proteomics, receptor-toxin interaction assays, biochemical experiments, pharmacological tests and preclinical evaluations. We reveal considerable variation in venom composition, functions, and pharmacological activities among the geographically distinct populations of B. caeruleus. Furthermore, toxin-receptor interaction assays provide insights into their feeding ecology and prey-predator interactions. Finally, in vitro and in vivo experiments revealed the poor neutralising potencies of Indian antivenoms towards most populations of the common krait. Our findings highlight the alarming need to develop efficacious snakebite therapy in India to treat bites from this medically most important elapid snake.

V-ToCs (Venom Toxin Clustering): A tool for the investigation of sequence and structure similarities in snake venom toxins

Recently, there has been a major push toward the development of next-generation treatments against snakebite envenoming. However, unlike current antivenoms that rely on animal-derived polyclonal antibodies, most of these novel approaches are reliant on an in-depth understanding of the over 2000 known snake venom toxins. Indeed, by identifying similarities (i.e., conserved epitopes) across these different toxins, it is possible to design cross-reactive treatments, such as broadly-neutralising antibodies, that target these similarities. Therefore, in this project, we built an automated pipeline that generates sequence and structural distance matrices and homology trees across all available snake venom toxin sequences and structures. To facilitate analysis, we also developed a user-friendly and high-throughput visualisation tool, coined "Venom TOxin CluStering" (V-ToCs). This tool allows researchers to easily investigate sequence and structure patterns in snake venom toxins for a wide array of purposes, such as elucidating toxin evolution, and will also hopefully help guide the discovery and development of increasingly broadly-neutralising antivenoms in the near future.

Distribution mapping of deadly scorpions in Iran

Scorpion sting is a problem all over the world and becomes an acute problem when it is associated with death. Iran is known as a region with a large number of scorpions and, of course, with many cases of scorpion stings per year. So far, 11 scorpion species in Iran have been identified as dangerous, of which there are only three species for which deaths have been reported. Due to the importance of these three species, we prepared a distribution map of these three types of scorpions and discuss the implications of these findings in the larger context of dangerous scorpion stings in Iran.

A review of bites by non-front-fanged snakes (NFFS) of Europe

Non-front-fanged snakes (NFFS) have long been overlooked by snake venom research, likely due to most of them being considered non-medically relevant for humans. The paucity of information about composition and activities of NFFS venoms and oral secretions makes it difficult to assess whether a given species can inflict medically significant bites. Here, we provide a review of the information currently available about the symptoms/signs elicited by bites from European NFFS, aiming to offer a foundation for understanding the threat they pose in terms of snakebite. Despite an overall limited amount of available data for most of the considered taxa, the genus Malpolon is notable for its capacity to cause local and systemic envenoming, including neurotoxic symptoms. Bites by other genera like, Hemorrhois, Hierophis, Natrix, Platyceps, Telescopus, and Zamenis are mainly associated with local symptoms, but the extent of their medical significance remains unclear. Our findings suggest that, although bites from European NFFS generally cause only mild effects, the potential occurrence of systemic effects from some species cannot be ruled out. Considering the above, any bite by European NFFS should receive professional medical evaluation in order to ensure patient safety and appropriate management, as well as detailed documentation facilitating construction of an accurate medical risk profile for the species.

Obscure properties of a traditional herb Pittosporum neelgherrense used to treat snakebite envenoming against Daboia russelli venoms

In tropical nations, snakebite envenomation is a significant public health issue with negative human and social effects. This is due to three factors: 1) more species of the most hazardous snakes are present; 2) emergency medical assistance is not readily available; and 3) inadequate health care. The problems caused by snakebite envenomation have been partially resolved by immunotherapy. An extensive collection of medicinal herbs is recognized to have antivenomous properties in traditional medicine. However, very few species have undergone scientific investigation, and even fewer have had their active components separated and structurally and functionally defined. In this work, the anti-venom potential of hot and cold aqueous extracts from Pittosporum neelgherrense is evaluated using an in-vitro model. The experimental results showed that 4H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl-(11.20), 1-Undecanol (16.38), Lauryl acetate (18.25), and Cyclotridecane (19.14) were phytochemical substances whose chemical structures were recognized by GCMS. The Direct and Indirect hemorrhagic activity was found to be completely neutralized by P. neelgherrense extract (44.61% hot plant extract & 55.38% cold plant extract) and the zone (2.4 mm), respectively. The neutralization of venoms was indicated by the zone (0.5-0.9 cm) of hydrolysis production of proteolytic activity. Additionally, the results of the gelatine liquefaction study demonstrated that clot formation was not triggered by venom at low concentrations (50:50) but was instead brought on by higher concentrations. The present study suggested that the neutralization of venom by hot water extracts of P. neelgherrense is a potentially therapeutic application.

VenomCap: An exon-capture probe set for the targeted sequencing of snake venom genes

Snake venoms are complex mixtures of toxic proteins that hold significant medical, pharmacological and evolutionary interest. To better understand the genetic diversity underlying snake venoms, we developed VenomCap, a novel exon-capture probe set targeting toxin-coding genes from a wide range of elapid snakes, with a particular focus on the ecologically diverse and medically important subfamily Hydrophiinae. We tested the capture success of VenomCap across 24 species, representing all major elapid lineages. We included snake phylogenomic probes in the VenomCap capture set, allowing us to compare capture performance between venom and phylogenomic loci and to infer elapid phylogenetic relationships. We demonstrated VenomCap's ability to recover exons from ~1500 target markers, representing a total of 24 known venom gene families, which includes the dominant gene families found in elapid venoms. We find that VenomCap's capture results are robust across all elapids sampled, and especially among hydrophiines, with respect to measures of target capture success (target loci matched, sensitivity, specificity and missing data). As a cost-effective and efficient alternative to full genome sequencing, VenomCap can dramatically accelerate the sequencing and analysis of venom gene families. Overall, our tool offers a model for genomic studies on snake venom gene diversity and evolution that can be expanded for comprehensive comparisons across the other families of venomous snakes.

Current Technologies in Snake Venom Analysis and Applications

This comprehensive review explores the cutting-edge advancements in snake venom research, focusing on the integration of proteomics, genomics, transcriptomics, and bioinformatics. Highlighting the transformative impact of these technologies, the review delves into the genetic and ecological factors driving venom evolution, the complex molecular composition of venoms, and the regulatory mechanisms underlying toxin production. The application of synthetic biology and multi-omics approaches, collectively known as venomics, has revolutionized the field, providing deeper insights into venom function and its therapeutic potential. Despite significant progress, challenges such as the functional characterization of toxins and the development of cost-effective antivenoms remain. This review also discusses the future directions of venom research, emphasizing the need for interdisciplinary collaborations and new technologies (mRNAs, cryo-electron microscopy for structural determinations of toxin complexes, synthetic biology, and other technologies) to fully harness the biomedical potential of venoms and toxins from snakes and other animals.

The Toxin Diversity, Cytotoxicity, and Enzymatic Activity of Cape Cobra (Naja nivea) Venom

"True" cobras (genus Naja) are among the venomous snakes most frequently involved in snakebite accidents in Africa and Asia. The Cape cobra (Naja nivea) is one of the African cobras of highest medical importance, but much remains to be learned about its venom. Here, we used a shotgun proteomics approach to better understand the qualitative composition of N. nivea venom and tested its cytotoxicity and protease activity as well as its effect on intracellular Ca2+ release and NO synthesis. We identified 156 venom components representing 17 protein families, with the dominant ones being three-finger toxins, mostly of the short-chain type. Two-thirds of the three-finger toxin entries identified were assigned as cytotoxins, while the remainder were categorized as neurotoxins, including short-chain, long-chain, and ancestral three-finger toxins. We also identified snake venom metalloproteinases and members of CRISP, l-amino acid oxidase, and other families. Protease activity and its effect on intracellular Ca2+ release and NO synthesis were low. Phospholipase A2 activity was surprisingly high, despite this toxin family being marginally recovered in the analyzed venom. Cytotoxicity was relevant only at higher venom concentrations, with macrophage and neuroblastoma cell lines showing the lowest viability. These results are in line with the predominantly neurotoxic envenomation symptoms caused by Cape cobra bites. The present overview of the qualitatively complex and functionally intriguing venom of N. nivea may provide insights into the pathobiochemistry of this species' venom.

Comparative functional characterization and in vitro immunological cross-reactivity studies on Daboia russelii and Craspedocephalus malabaricus venom

BACKGROUND

Snake venom is a complex mixture of organic and inorganic constituents, including proteins and peptides. Several studies showed that antivenom efficacy differs due to intra- and inter-species venom variation.

METHODS

In the current study, comparative functional characterization of major enzymatic proteins present in Craspedocephalus malabaricus and Daboia russelii venom was investigated through various in vitro and immunological cross-reactivity assays.

RESULTS

The enzymatic assays revealed that hyaluronidase and phospholipase A2 activities were markedly higher in D. russelii. By contrast, fibrinogenolytic, fibrin clotting and L-amino acid oxidase activities were higher in C. malabaricus venom. ELISA results suggested that all the antivenoms had lower binding potential towards C. malabaricus venom. For D. russelii venom, the endpoint titration value was observed at 1:72 900 for all the antivenoms. In the case of C. malabaricus venom, the endpoint titration value was 1:2700, except for Biological E (1:8100). All these results, along with the avidity assays, indicate the strength of venom-antivenom interactions. Similarly, the western blot results suggest that all the antivenoms showed varied efficacies in binding and detecting the venom antigenic epitopes in both species.

CONCLUSIONS

The results highlight the need for species-specific antivenom to better manage snakebite victims.

Intraspecific venom variation in the medically important puff adder (Bitis arietans): Comparative venom gland transcriptomics, in vitro venom activity and immunological recognition by antivenom

BACKGROUND

Variation in snake venoms is well documented, both between and within species, with intraspecific venom variation often correlated with geographically distinct populations. The puff adder, Bitis arietans, is widely distributed across sub-Saharan Africa and into the Arabian Peninsula where it is considered a leading cause of the ~310,000 annual snakebites across the region, with its venom capable of causing substantial morbidity and mortality. Despite its medical importance and wide geographic distribution, there is little known about venom variation between different B. arietans populations and the potential implications of this variation on antivenom efficacy.

METHODOLOGY

We applied a range of analyses, including venom gland transcriptomics, in vitro enzymatic assays and reverse phase chromatography to comparatively analyse B. arietans venoms originating from Nigeria, Tanzania, and South Africa. Immunological assays and in vitro enzymatic neutralisation assays were then applied to investigate the impact of venom variation on the potential efficacy of three antivenom products; SAIMR Polyvalent, EchiTAb-Plus and Fav-Afrique.

FINDINGS

Through the first comparison of venom gland transcriptomes of B. arietans from three geographically distinct regions (Nigeria, Tanzania, and South Africa), we identified substantial variation in toxin expression. Findings of venom variation were further supported by chromatographic venom profiling, and the application of enzymatic assays to quantify the activity of three pathologically relevant toxin families. However, the use of western blotting, ELISA, and in vitro enzymatic inhibition assays revealed that variation within B. arietans venom does not appear to substantially impact upon the efficacy of three African polyvalent antivenoms.

CONCLUSIONS

The large distribution and medical importance of B. arietans makes this species ideal for understanding venom variation and the impact this has on therapeutic efficacy. The findings in this study highlight the likelihood for considerable venom toxin variation across the range of B. arietans, but that this may not dramatically impact upon the utility of treatment available in the region.

Proteogenomics-guided functional venomics resolves the toxin arsenal and activity of Deinagkistrodon acutus venom

Snakebite primarily impacts rural communities of Africa, Asia, and Latin America. The sharp-nosed viper (Deinagkistrodon acutus) is among the snakes of highest medical importance in Asia. Despite various studies on its venom using modern venomics techniques, a comprehensive understanding of composition and function of this species' venom remains lacking. We combined proteogenomics with extensive bioactivity profiling to present the first genome-level catalogue of D. acutus venom proteins and their exochemistry. Our analysis identified an unusually simple venom containing 45 components from 20 distinct protein families. Relative toxin abundances indicate that C-type lectin and C-type lectin-related protein (CTL), snake venom metalloproteinase (svMP), snake venom serine protease (svSP), and phospholipase A2 (PLA2) constitute 90 % of the venom. Bioassays targeting key aspects of viperid envenomation showed considerable concentration-dependent cytotoxicity, particularly in kidney and lung cells, and potent protease and PLA2 activity. Factor Xa and thrombin activities were minor, and no plasmin activity was observed. Effects on haemolysis, intracellular calcium (Ca2+) release, and nitric oxide (NO) synthesis were negligible. Our analysis provides the first holistic genome-based overview of the toxin arsenal of D. acutus, predicting the molecular and functional basis of its life-threatening effects, and opens novel avenues for treating envenomation by this highly dangerous snake.

An in-depth exploration of snake venom-derived molecules for drug discovery in advancing antiviral therapeutics

Snake venom is a cocktail and rich source of various bioactive compounds that have been extensively studied for their potential as pharmaceutical agents due to their diverse chemical structures and wide range of biological activities. In light of the emergency and the re-emergence of viral infectious diseases that threaten human health and economic systems, exploring new fertile and rich fields such as snake venom is an attractive path for anti-viral drug discovery, especially in the lack of effective vaccines. Although 85 % of reported antiviral molecules belong to the phospholipase A2 (PLA2) family, other protein families including L-amino acid oxidases (LAAO), disintegrins, metalloproteases (SVMPs), and cathelicidins have also shown antiviral activity. Thus, in this review, we have highlighted the antiviral properties of compounds derived from snake venom and their mechanisms of action against virus classes like HIV, Coronaviridae, Flaviviridae, and Paramyxoviridae. Although the initial research emphasis has been on Retroviridae (HIV) and Flaviviridae viruses, it is crucial to extend the exploration of the potential of these compounds to other viruses. The utilization of snake venom-derived compounds as antivirals shows significant promise for the development of novel therapeutics to address viral infections. However, a more in-depth investigation is necessary to fully assess the potential of these compounds against other viruses and unveil the mechanisms underlying their action.

Isolation and Pharmacological Characterisation of Pre-Synaptic Neurotoxins from Thai and Javanese Russell's Viper (Daboia siamensis) Venoms

The widespread geographical distribution of Russell's vipers (Daboia spp.) is associated with marked variations in the clinical outcomes of envenoming by species from different countries. This is likely to be due to differences in the quantity and potency of key toxins and, potentially, the presence or absence of some toxins in venoms across the geographical spectrum. In this study, we aimed to isolate and pharmacologically characterise the major neurotoxic components of D. siamensis venoms from Thailand and Java (Indonesia) and explore the efficacy of antivenom and a PLA2 inhibitor, Varespladib, against the neuromuscular activity. These data will provide insights into the link between venom components and likely clinical outcomes, as well as potential treatment strategies. Venoms were fractionated using RP-HPLC and the in vitro activity of isolated toxins assessed using the chick biventer cervicis nerve-muscle preparation. Two major PLA2 fractions (i.e., fractions 8 and 10) were isolated from each venom. Fraction 8 from both venoms produced pre-synaptic neurotoxicity and myotoxicity, whereas fraction 10 from both venoms was weakly neurotoxic. The removal of the two fractions from each venom abolished the in vitro neurotoxicity, and partially abolished myotoxicity, of the whole venom. A combination of the two fractions from each venom produced neurotoxic activity that was equivalent to the respective whole venom (10 µg/mL), but the myotoxic effects were not additive. The in vitro neurotoxicity of fraction 8 (100 nM) from each venom was prevented by the pre-administration of Thai Russell's viper monovalent antivenom (2× recommended concentration) or preincubation with Varespladib (100 nM). Additionally, the neurotoxicity produced by a combination of the two fractions was partially reversed by the addition of Varespladib (100-300 nM) 60 min after the fractions. The present study demonstrates that the in vitro skeletal muscle effects of Thai and Javanese D. siamensis venoms are primarily due to key PLA2 toxins in each venom.

Identification of antigenic proteins from the venom of Malaysian snakes using immunoprecipitation assay and tandem mass spectrometry (LC-MS/MS)

Snake envenomation poses a significant risk to Malaysians and country visitors. Malaysia witnesses an estimated 650 snake bites per 100,000 population annually. The primary treatment for snake envenomation involves administering antivenom derived from horses, despite its drawbacks, such as anaphylactic reactions and serum sickness. Identifying the venom proteome is crucial for understanding and predicting the clinical implications of envenomation and developing effective treatments targeting specific venom proteins. In this study, we employ an immunoprecipitation assay followed by LC-MS/MS to identify antigenic proteins in five common venomous snakes in Malaysia compassing of two families which are pit vipers, (Calloselasma rhodostoma and Cryptelytrops purpureomaculatus) and cobras (Ophiophagus hannah, Naja kaouthia, and Naja sumatrana). The immunoprecipitation assay utilises a 2 % agarose gel, allowing antigenic proteins to diffuse and bind with antibodies in the antivenom. The antivenom utilised in this research was procured from the Queen Saovabha Memorial Institute (QSMI), Thailand, including king cobra antivenom (KCAV), cobra antivenom (CAV), Malayan pit viper antivenom (MPAV), Russell's viper antivenom (RPAV), hematopolyvalent antivenom (HPAV), neuropolyvalent antivenom (NPAV), banded krait antivenom (BKAV), and Malayan krait antivenom (MKAV). The protein identified through these interactions which are exclusive to the cobras are three-finger toxins (3FTXs) while snake C-type lectins (Snaclecs) are unique to the pit vipers. Common protein that are present in both families are L-amino acid oxidase (LAAO), Phospholipase A2 (PLA2), and snake venom metalloproteinase (SVMP). Identifying these proteins is vital for formulating a broad-spectrum antivenom applicable across multiple species.

Tiny but Mighty: Vipera ammodytes meridionalis (Eastern Long-Nosed Viper) Ontogenetic Venom Variations in Procoagulant Potency and the Impact on Antivenom Efficacies

The Eastern Long-Nosed Viper (Vipera ammodytes meridionalis) is considered one of the most venomous snakes in Europe. However, it is unknown whether ontogenetic variation in venom effects occurs in this subspecies and how this may impact antivenom efficacy. In this study, we compared the procoagulant activities of V. a. meridionalis venom on human plasma between neonate and adult venom phenotypes. We also examined the efficacy of three antivenoms-Viperfav, ViperaTAb, and Inoserp Europe-across our neonate and adult venom samples. While both neonate and adult V. a. meridionalis venoms produced procoagulant effects, the effects produced by neonate venom were more potent. Consistent with this, neonate venom was a stronger activator of blood-clotting zymogens, converting them into their active forms, with a rank order of Factor X >> Factor VII > Factor XII. Conversely, the less potent adult venom had a rank order of FXII marginally more activated than Factor VII, and both much more so than Factor X. This adds to the growing body of evidence that activation of factors besides FII (prothrombin) and FX are significant variables in reptile venom-induced coagulopathy. Although all three examined antivenoms displayed effective neutralization of both neonate and adult V. a. meridionalis venoms, they generally showed higher efficacy on adult venom than on neonate venom. The ranking of antivenom efficacy against neonate venom, from the most effective to the least effective, were Viperfav, Inoserp Europe, ViperaTAb; for adult venom, the ranking was Inoserp Europe, Viperfav, ViperaTAb. Our data reveal ontogenetic variation in V. a meridionalis, but this difference may not be of clinical concern as antivenom was effective at neutralizing both adult and neonate venom phenotypes. Regardless, our results highlight a previously undocumented ontogenetic shift, likely driven by the documented difference in prey preference observed for this species across age classes.

Where the "ruber" Meets the Road: Using the Genome of the Red Diamond Rattlesnake to Unravel the Evolutionary Processes Driving Venom Evolution

Understanding the proximate and ultimate causes of phenotypic variation is fundamental in evolutionary research, as such variation provides the substrate for selection to act upon. Although trait variation can arise due to selection, the importance of neutral processes is sometimes understudied. We presented the first reference-quality genome of the Red Diamond Rattlesnake (Crotalus ruber) and used range-wide 'omic data to estimate the degree to which neutral and adaptive evolutionary processes shaped venom evolution. We characterized population structure and found substantial genetic differentiation across two populations, each with distinct demographic histories. We identified significant differentiation in venom expression across age classes with substantially reduced but discernible differentiation across populations. We then used conditional redundancy analysis to test whether venom expression variation was best predicted by neutral divergence patterns or geographically variable (a)biotic factors. Snake size was the most significant predictor of venom variation, with environment, prey availability, and neutral sequence variation also identified as significant factors, though to a lesser degree. By directly including neutrality in the model, our results confidently highlight the predominant, yet not singular, role of life history in shaping venom evolution.

Snakebite Management: The Need of Reassessment, International Relations, and Effective Economic Measures to Reduce the Considerable SBE Burden

The sole treatment for snakebite envenomation (SBE), the anti-snake venom (ASV), suffers from considerable drawbacks, including side effects and limited species specificity. Additionally, despite its existence for more than a century, uniform availability of good quality ASV does not yet exist. The present review describes the journey of a SBE victim and highlights the global crisis of SBE management. A detailed analysis of the current ASV market has also been presented along with the worldwide snake distribution. The current production of country specific licensed ASV throughout the globe along with their manufacturers has been examined at the snake species level. Furthermore, a detailed analysis of on-ground situation of SBE management in antivenom manufacturing countries has been done using the most recent literature. Additionally, the export and import of different ASVs have been discussed in terms of procurement policies of individual countries, their shortcomings, along with the possible solution at the species level. It is interesting to note that in most countries, the existence of ASV is really either neglected or overstated, implying that it is there but unsuitable for use, or that it is not present but can be obtained from other countries. This highlights the urgent need of significant reassessment and international collaborations not just for development and production, but also for procurement, distribution, availability, and awareness. A PROMISE (Practical ROutes for Managing Indigenous Snakebite Envenoming) approach has also been introduced, offering simple, economical, and easy to adopt steps to efficiently alleviate the worldwide SBE burden.

Plug and play virus-like particles for the generation of anti-toxin antibodies

Snakebite is a major global health concern, for which antivenom remains the only approved treatment to neutralise the harmful effects of the toxins. However, some medically important toxins are poorly immunogenic, resulting in reduced efficacy of the final product. Boosting the immunogenicity of these toxins in the commercial antivenom immunising mixtures could be an effective strategy to improve the final dose efficacy, and displaying snake antigens on Virus-like particles (VLPs) is one method for this. However, despite some applications in the field of snakebite, VLPs have yet to be explored in methods that could be practical at an antivenom manufacturing scale. Here we describe the utilisation of a "plug and play" VLP system to display immunogenic linear peptide epitopes from three finger toxins (3FTxs) and generate anti-toxin antibodies. Rabbits were immunised with VLPs displaying individual consensus linear epitopes and their antibody responses were characterised by immunoassay. Of the three experimental consensus sequences, two produced antibodies capable of recognising the consensus peptides, whilst only one of these could also recognise native whole toxins. Further characterisation of antibodies raised against this peptide demonstrated a sub-class specific response, and that these were able to elicit partially neutralising antibody responses, resulting in increased survival times in a murine snakebite envenoming model.

The need for a refined scorpion antivenom for Iran

Scorpion sting is a medical burden globally but especially frequent hotspots of scorpion biodiversity. In Iran, one of those hotspot countries, many fatalities occur in the South as well as the Southwest and are thought to be caused by Hemiscorpius lepturus. Accordingly, those are used for antivenom production. However, recent surveys revealed that indeed a different species Hemiscorpius acanthocercus is responsible for most accidents in the South, while H. lepturus is primarily causing the fatalities in the Southwest and thus Iranian scorpion antivenom needs to be refined in that respect. Such a refined antivenom would need to cover both species of Hemiscorpius. In response, the Iranian Ministry of Health requested the adjustment of the production line from local antivenom suppliers but until today no action has been taken.

Comparative venom analysis between melanistic and normally coloured phenotypes of the common adder (Vipera berus)

Snake venom is an ecologically relevant functional trait directly linked with a snake's fitness and survival, facilitating predation and defence. Snake venom variation occurs at all taxonomic levels, but the study at the intraspecific level is still in its early stages. The common adder (Vipera berus) exhibits considerable variation in colour phenotypes across its distribution range. Melanistic (fully black) individuals are the subject of myths and fairytales, and in German folklore such 'hell adders' are considered more toxic than their normally coloured conspecifics despite any formal investigation. Here, we provide the first comparative analysis of venoms from melanistic and normally coloured common adders. Specifically, we compared the venom profiles by sodium dodecylsulfate polyacrylamide gel electrophoresis and reversed-phase high-performance liquid chromatography and tested the venoms' protease, phospholipase A2 and cytotoxic activities. Phospholipase A2 activity was similar in both phenotypes, whereas general protease activity was higher in the melanistic venom, which was also more cytotoxic at two concentrations (6.25 and 12.5 µg ml-1). These minor differences between the venoms of melanistic and normally coloured adders are unlikely to be of clinical relevance in the context of human envenomation. In light of our results, the claim that melanistic adders produce more toxic venom than their normally coloured conspecifics appears rooted entirely in folklore.

Experimental production and efficacy testing of mono-specific antibodies against the venom of carpet viper (Echis ocellatus) from savannah Nigeria

Echis ocellatus is one of the commonest snakes responsible for envenomation in Nigeria. Antivenom is the only effective treatment, but the country suffers from a limited supply of effective antivenom. This study therefore aimed to explore the feasibility of effective, mono-specific antibodies production through immunization in rabbits using the venom of Echis ocellatus from Nigeria. The World Health Organization guide on antivenom production was employed in the immunization and the resultant antibodies were purified using protein A agarose column chromatography. Antibody titer reached a high plateau by 2-month immunization, and SDS PAGE of the sera suggests the presence of intact immunoglobulins accompanied with the heavy (50 kDa) and light (25 kDa) chains. The venom has an intravenous LD50 of 0.35 mg/kg in mice, and the venom lethality at a challenge dose of 2 LD50 was effectively neutralized by the antibodies with a potency value of 0.83 mg venom per g antibodies. The antibodies also neutralized the procoagulant activity of the venom with an effective dose (ED) of 13 ± 0.66 μl, supporting its use for hemotoxic envenomation. The study establishes the feasibility of developing effective, mono-specific antibodies against the Nigerian Carpet viper.

Venomics and Peptidomics of Palearctic Vipers: A Clade-Wide Analysis of Seven Taxa of the Genera Vipera, Montivipera, Macrovipera, and Daboia across Türkiye

Snake venom variations are a crucial factor to understand the consequences of snakebite envenoming worldwide, and therefore it is important to know about toxin composition alterations between taxa. Palearctic vipers of the genera Vipera, Montivipera, Macrovipera, and Daboia have high medical impacts across the Old World. One hotspot for their occurrence and diversity is Türkiye, located on the border between continents, but many of their venoms remain still understudied. Here, we present the venom compositions of seven Turkish viper taxa. By complementary mass spectrometry-based bottom-up and top-down workflows, the venom profiles were investigated on proteomics and peptidomics level. This study includes the first venom descriptions of Vipera berus barani, Vipera darevskii, Montivipera bulgardaghica albizona, and Montivipera xanthina, as well as the first snake venomics profiles of Turkish Macrovipera lebetinus obtusa, and Daboia palaestinae, including an in-depth reanalysis of M. bulgardaghica bulgardaghica venom. Additionally, we identified the modular consensus sequence pEXW(PZ)1-2P(EI)/(KV)PPLE for bradykinin-potentiating peptides in viper venoms. For better insights into variations and potential impacts of medical significance, the venoms were compared against other Palearctic viper proteomes, including the first genus-wide Montivipera venom comparison. This will help the risk assessment of snakebite envenoming by these vipers and aid in predicting the venoms' pathophysiology and clinical treatments.

Novel phylogenomic inference and 'Out of Asia' biogeography of cobras, coral snakes and their allies

Estimation of evolutionary relationships among lineages that rapidly diversified can be challenging, and, in such instances, inaccurate or unresolved phylogenetic estimates can lead to erroneous conclusions regarding historical geographical ranges of lineages. One example underscoring this issue has been the historical challenge posed by untangling the biogeographic origin of elapoid snakes, which includes numerous dangerously venomous species as well as species not known to be dangerous to humans. The worldwide distribution of this lineage makes it an ideal group for testing hypotheses related to historical faunal exchanges among the many continents and other landmasses occupied by contemporary elapoid species. We developed a novel suite of genomic resources, included worldwide sampling, and inferred a robust estimate of evolutionary relationships, which we leveraged to quantitatively estimate geographical range evolution through the deep-time history of this remarkable radiation. Our phylogenetic and biogeographical estimates of historical ranges definitively reject a lingering former 'Out of Africa' hypothesis and support an 'Out of Asia' scenario involving multiple faunal exchanges between Asia, Africa, Australasia, the Americas and Europe.

From birth to bite: the evolutionary ecology of India's medically most important snake venoms

BACKGROUND

Snake venoms can exhibit remarkable inter- and intraspecific variation. While diverse ecological and environmental factors are theorised to explain this variation, only a handful of studies have attempted to unravel their precise roles. This knowledge gap not only impedes our understanding of venom evolution but may also have dire consequences on snakebite treatment. To address this shortcoming, we investigated the evolutionary ecology of venoms of Russell's viper (Daboia russelii) and spectacled cobra (Naja naja), India's two clinically most important snakes responsible for an alarming number of human deaths and disabilities.

METHODOLOGY

Several individuals (n = 226) of D. russelii and N. naja belonging to multiple clutches (n = 9) and their mothers were maintained in captivity to source ontogenetic stage-specific venoms. Using various in vitro and in vivo assays, we assessed the significance of prey, ontogeny and sex in driving venom composition, function, and potency.

RESULTS

Considerable ontogenetic shifts in venom profiles were observed in D. russelii, with the venoms of newborns being many times as potent as juveniles and adults against mammalian (2.3-2.5 ×) and reptilian (2-10 ×) prey. This is the first documentation of the ontogenetic shift in viperine snakes. In stark contrast, N. naja, which shares a biogeographic distribution similar to D. russelii, deployed identical biochemical cocktails across development. Furthermore, the binding kinetics of cobra venom toxins against synthetic target receptors from various prey and predators shed light on the evolutionary arms race.

CONCLUSIONS

Our findings, therefore, provide fascinating insights into the roles of ecology and life history traits in shaping snake venoms.

Selection Across the Three-Dimensional Structure of Venom Proteins from North American Scolopendromorph Centipedes

Gene duplication followed by nucleotide differentiation is one of the simplest mechanisms to develop new functions for genes. However, the evolutionary processes underlying the divergence of multigene families remain controversial. We used multigene families found within the diversity of toxic proteins in centipede venom to test two hypotheses related to venom evolution: the two-speed mode of venom evolution and the rapid accumulation of variation in exposed residues (RAVER) model. The two-speed mode of venom evolution proposes that different types of selection impact ancient and younger venomous lineages with negative selection being the predominant form in ancient lineages and positive selection being the dominant form in younger lineages. The RAVER hypothesis proposes that, instead of different types of selection acting on different ages of venomous lineages, the different types of selection will selectively contribute to amino acid variation based on whether the residue is exposed to the solvent where it can potentially interact directly with toxin targets. This hypothesis parallels the longstanding understanding of protein evolution that suggests that residues found within the structural or active regions of the protein will be under negative or purifying selection, and residues that do not form part of these areas will be more prone to positive selection. To test these two hypotheses, we compared the venom of 26 centipedes from the order Scolopendromorpha from six currently recognized species from across North America using both transcriptomics and proteomics. We first estimated their phylogenetic relationships and uncovered paraphyly among the genus Scolopendra and evidence for cryptic diversity among currently recognized species. Using our phylogeny, we then characterized the diverse venom components from across the identified clades using a combination of transcriptomics and proteomics. We conducted selection-based analyses in the context of predicted three-dimensional properties of the venom proteins and found support for both hypotheses. Consistent with the two-speed hypothesis, we found a prevalence of negative selection across all proteins. Consistent with the RAVER hypothesis, we found evidence of positive selection on solvent-exposed residues, with structural and less-exposed residues showing stronger signal for negative selection. Through the use of phylogenetics, transcriptomics, proteomics, and selection-based analyses, we were able to describe the evolution of venom from an ancient venomous lineage and support principles of protein evolution that directly relate to multigene family evolution.

Molecular dissection of cobra venom highlights heparinoids as an antidote for spitting cobra envenoming

Snakebites affect about 1.8 million people annually. The current standard of care involves antibody-based antivenoms, which can be difficult to access and are generally not effective against local tissue injury, the primary cause of morbidity. Here, we used a pooled whole-genome CRISPR knockout screen to define human genes that, when targeted, modify cell responses to spitting cobra venoms. A large portion of modifying genes that conferred resistance to venom cytotoxicity was found to control proteoglycan biosynthesis, including EXT1, B4GALT7, EXT2, EXTL3, XYLT2, NDST1, and SLC35B2, which we validated independently. This finding suggested heparinoids as possible inhibitors. Heparinoids prevented venom cytotoxicity through binding to three-finger cytotoxins, and the US Food and Drug Administration-approved heparinoid tinzaparin was found to reduce tissue damage in mice when given via a medically relevant route and dose. Overall, our systematic molecular dissection of cobra venom cytotoxicity provides insight into how we can better treat cobra snakebite envenoming.

Diverse Gene Regulatory Mechanisms Alter Rattlesnake Venom Gene Expression at Fine Evolutionary Scales

Understanding and predicting the relationships between genotype and phenotype is often challenging, largely due to the complex nature of eukaryotic gene regulation. A step towards this goal is to map how phenotypic diversity evolves through genomic changes that modify gene regulatory interactions. Using the Prairie Rattlesnake (Crotalus viridis) and related species, we integrate mRNA-seq, proteomic, ATAC-seq and whole-genome resequencing data to understand how specific evolutionary modifications to gene regulatory network components produce differences in venom gene expression. Through comparisons within and between species, we find a remarkably high degree of gene expression and regulatory network variation across even a shallow level of evolutionary divergence. We use these data to test hypotheses about the roles of specific trans-factors and cis-regulatory elements, how these roles may vary across venom genes and gene families, and how variation in regulatory systems drive diversity in venom phenotypes. Our results illustrate that differences in chromatin and genotype at regulatory elements play major roles in modulating expression. However, we also find that enhancer deletions, differences in transcription factor expression, and variation in activity of the insulator protein CTCF also likely impact venom phenotypes. Our findings provide insight into the diversity and gene-specificity of gene regulatory features and highlight the value of comparative studies to link gene regulatory network variation to phenotypic variation.

Qualitative Profiling of Venom Toxins in the Venoms of Several Bothrops Species Using High-Throughput Venomics and Coagulation Bioassaying

Envenoming resulting from snakebites is recognized as a priority neglected tropical disease by The World Health Organization. The Bothrops genus, consisting of different pitviper species, is considered the most medically significant taxa in Central and South America. Further research into Bothrops venom composition is important to aid in the development of safer and more effective snakebite treatments. In addition, the discovery of Bothrops toxins that could potentially be used for medical or diagnostic purposes is of interest to the pharmaceutical industry. This study aimed to employ high-throughput (HT) venomics to qualitatively analyze venom composition while utilizing coagulation bioassays for identifying coagulopathic toxins and characterizing coagulopathic activity in various Bothrops venoms. Using the recently demonstrated HT venomics workflow in combination with post-column coagulopathic bioassaying, focus was placed at anticoagulant toxins. Well-known procoagulant toxins were also investigated, taking into account that using the HT venomics workflow, procoagulant toxins are especially prone to denaturation during the reversed-phase chromatographic separations performed in the workflow. The findings revealed that the venoms of B. atrox and B. jararaca harbored procoagulant toxins, whereas those of B. alternatus and B. neuwiedi contained both procoagulant and anticoagulant toxins. In general, anticoagulation was associated with phospholipases A2s, while procoagulation was associated with snake venom metalloproteinases and snake venom serine proteases. These results showed the identification of coagulopathic venom toxins in the Bothrops venoms analyzed using multiple analytical methods that complement each other. Additionally, each venom underwent qualitative characterization of its composition.

A comparison of the venom proteomes and potential therapeutics of 3 African naja subgenera

African cobras (Naja species) represent one of the most encountered medically important snakes in Africa. They are classified as African spitting (Afronaja subgenus) and non-spitting cobras (Uraeus and Boulengerina subgenera) with similar and different characteristics. Snake venom toxins including three-finger toxin (3FTx), phospholipase A2 (PLA2), and snake venom metalloproteinase (SVMP) cause snakebite envenomation leading to morbidity and mortality. The profile of the proteome of African cobra venoms will help to develop safer and more effective antivenoms. The approval of Captopril by the US Food and Drug Administration (FDA) for the treatment of cardiovascular diseases, has led to intensified research towards possible use of venom toxins as therapeutics. In this review, we compare the venom proteome profile of 3 African Naja subgenera. In both Afronaja and Boulengerina subgenera, 3FTx (Afronaja-69.79%; Boulengerina-60.56%) followed by PLA2 (Afronaja-21.15%; Boulengerina-20.21%) dominated the venoms compared to the Uraeus subgenus dominated by 3FTx (84.55%) with little to no PLA2 abundance (0.8%). The venom of subgenus Uraeus was distinct from the other two subgenera by the almost total absence of PLA2, thus indicating little or no contribution of PLA2 in the envenomation caused by Uraeus compared to Afronaja and Boulengerina. Furthermore, we report studies on the experimental testing of African cobra venoms and toxins against diseases including anti-cancer properties.

Investigating Snake-Venom-Induced Dermonecrosis and Inflammation Using an Ex Vivo Human Skin Model

Snakebite envenoming is a neglected tropical disease that causes >100,000 deaths and >400,000 cases of morbidity annually. Despite the use of mouse models, severe local envenoming, defined by morbidity-causing local tissue necrosis, remains poorly understood, and human-tissue responses are ill-defined. Here, for the first time, an ex vivo, non-perfused human skin model was used to investigate temporal histopathological and immunological changes following subcutaneous injections of venoms from medically important African vipers (Echis ocellatus and Bitis arietans) and cobras (Naja nigricollis and N. haje). Histological analysis of venom-injected ex vivo human skin biopsies revealed morphological changes in the epidermis (ballooning degeneration, erosion, and ulceration) comparable to clinical signs of local envenoming. Immunostaining of these biopsies confirmed cell apoptosis consistent with the onset of necrosis. RNA sequencing, multiplex bead arrays, and ELISAs demonstrated that venom-injected human skin biopsies exhibited higher rates of transcription and expression of chemokines (CXCL5, MIP1-ALPHA, RANTES, MCP-1, and MIG), cytokines (IL-1β, IL-1RA, G-CSF/CSF-3, and GM-CSF), and growth factors (VEGF-A, FGF, and HGF) in comparison to non-injected biopsies. To investigate the efficacy of antivenom, SAIMR Echis monovalent or SAIMR polyvalent antivenom was injected one hour following E. ocellatus or N. nigricollis venom treatment, respectively, and although antivenom did not prevent venom-induced dermal tissue damage, it did reduce all pro-inflammatory chemokines, cytokines, and growth factors to normal levels after 48 h. This ex vivo skin model could be useful for studies evaluating the progression of local envenoming and the efficacy of snakebite treatments.

The venom and telopodal defence systems of the centipede Lithobius forficatus are functionally convergent serial homologues

BACKGROUND

Evolution of novelty is a central theme in evolutionary biology, yet studying the origins of traits with an apparently discontinuous origin remains a major challenge. Venom systems are a well-suited model for the study of this phenomenon because they capture several aspects of novelty across multiple levels of biological complexity. However, while there is some knowledge on the evolution of individual toxins, not much is known about the evolution of venom systems as a whole. One way of shedding light on the evolution of new traits is to investigate less specialised serial homologues, i.e. repeated traits in an organism that share a developmental origin. This approach can be particularly informative in animals with repetitive body segments, such as centipedes.

RESULTS

Here, we investigate morphological and biochemical aspects of the defensive telopodal glandular organs borne on the posterior legs of venomous stone centipedes (Lithobiomorpha), using a multimethod approach, including behavioural observations, comparative morphology, proteomics, comparative transcriptomics and molecular phylogenetics. We show that the anterior venom system and posterior telopodal defence system are functionally convergent serial homologues, where one (telopodal defence) represents a model for the putative early evolutionary state of the other (venom). Venom glands and telopodal glandular organs appear to have evolved from the same type of epidermal gland (four-cell recto-canal type) and while the telopodal defensive secretion shares a great degree of compositional overlap with centipede venoms in general, these similarities arose predominantly through convergent recruitment of distantly related toxin-like components. Both systems are composed of elements predisposed to functional innovation across levels of biological complexity that range from proteins to glands, demonstrating clear parallels between molecular and morphological traits in the properties that facilitate the evolution of novelty.

CONCLUSIONS

The evolution of the lithobiomorph telopodal defence system provides indirect empirical support for the plausibility of the hypothesised evolutionary origin of the centipede venom system, which occurred through functional innovation and gradual specialisation of existing epidermal glands. Our results thus exemplify how continuous transformation and functional innovation can drive the apparent discontinuous emergence of novelties on higher levels of biological complexity.

Analysis of intra-specific variations in the venom of individual snakes based on Raman spectroscopy

The knowledge of variations in the composition of venoms from different snakes is important from both theoretical and practical points of view, in particular, at developing and selecting an antivenom. Many studies on this topic are conducted with pooled venoms, while the existence and significance of variations in the composition of venoms between individual snakes of the same species are emphasized by many authors. It is important to study both inter- and intra-specific, including intra-population, venom variations, because intra-specific variations in the venom composition may affect the effectiveness of antivenoms as strongly as inter-specific. In this work, based on venom Raman spectroscopy with principal component analysis, we assessed the variations in venoms of individual snakes of the Vipera nikolskii species from two populations and compared these intra-specific variations with inter-specific variations (with regard to the other related species). We demonstrated intra-specific (inter- and intra-population) differences in venom compositions which are smaller than inter-specific variations. We also assessed the compositions of V. nikolskii venoms from two populations to explain inter-population differences. The method used is rapid and requires virtually no preparation of samples, used in extremely small quantities, allowing the venoms of individual snakes to be analyzed. In addition, the method is informative and capable of detecting fairly subtle differences in the composition of venoms.

A review on snake venom extracellular vesicles: Past to present

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