Toxicity evolution of Vipera aspis aspis venom: identification and molecular modeling of a novel phospholipase A(2) heterodimer neurotoxin

Envenomation by Vipera aspis in Piedmont (Italy): A report of three cases, including one case with neurological symptoms

This report describes three cases of human envenomation by the asp viper (Vipera aspis) in Piedmont, north-west Italy. A woman was bitten on the ankle while she was hiking and two herpetologists received bites on the hand while they were manipulating the animals. In the first case, the victim presented severe systemic symptoms (abdominal pain, vomiting, diarrhea) that required treatment with two vials of antivenom and hospitalization for one week. In the second case, the patient manifested neurological symptoms (blepharoptosis, ophtalmoplegia); he was treated with antivenom and discharged after five days. In the third case, the patient was bitten by a juvenile viper and showed only local symptoms (edema and bruising). All patients reported prolonged functional impairment after discharge from hospital. Although uncommon, envenomation by Vipera aspis can cause severe consequences that require immediate management and antivenom administration. These cases highlight the importance of obtaining better knowledge of the intraspecific variability of venoms and its clinical significance, as well as of the factors that determine the severity of snakebite injuries.

Diverse and Dynamic Alpha-Neurotoxicity Within Venoms from the Palearctic Viperid Snake Clade of Daboia, Macrovipera, Montivipera, and Vipera

The targeting of specific prey by snake venom toxins is a fascinating aspect of molecular and ecological evolution. Neurotoxic targeting by elapid snakes dominates the literature in this regard; however, recent studies have revealed viper toxins also induce neurotoxic effect. While this effect is thought to primarily be driven by prey selectivity, no study has quantified the taxonomically specific neurotoxicity of the viper clade consisting of Daboia, Macrovipera, Montivipera, and Vipera genera. Here, we tested venom toxin binding from 28 species of vipers from the four genera on the alpha 1 neuronal nicotinic acetylcholine receptors (nAChRs) orthosteric sites of amphibian, avian, lizard, rodent, and human mimotopes (synthetic peptides) using the Octet HTX biolayer interferometry platform. Daboia siamensis and D. russelii had broad binding affinity towards all mimotopes, while D. palestinae had selectivity toward lizard. Macrovipera species, on the other hand, were observed to have a higher affinity for amphibian mimotopes except for M. schweizeri, which inclined more toward lizard mimotopes. All Montivipera and most Vipera species also had higher affinity toward lizard mimotopes. Vipera a. montandoni, V. latastei, V. nikolski, and V. transcaucasina had the least binding to any of the mimotopes of the study. While a wide range of affinity binding towards various mimotopes were observed within the clade, the lowest affinity occurred towards the human target. Daboia siamensis and Macrovipera lebetina exhibited the greatest affinity toward the human mimotope, albeit still the least targeted of the mimotopes within those species. Overlaying this toxin-targeting trait over phylogeny of this clade revealed multiple cases of amplification of this trait and several cases of secondary loss. Overall, our results reveal dynamic variation, amplification, and some secondary loss of the prey targeting trait by alpha-neurotoxins within the venoms of this clade, indicating evolutionary selection pressure shaping the basic biochemistry of these venoms. Our work illustrates the successful use of this biophysical assay to further research snake venom neurotoxins and emphasizes the risk of generalizing venom effects observed on laboratory animals to have similar effects on humans.

Vipers of Major clinical relevance in Europe: Taxonomy, venom composition, toxicology and clinical management of human bites

Snakebites in Europe are mostly due to bites from Viperidae species of the genus Vipera. This represents a neglected public health hazard with poorly defined incidence, morbidity and mortality. In Europe, fourteen species of "true vipers" (subfamily Viperinae) are present, eleven of which belong to the genus Vipera. Amongst these, the main medically relevant species due to their greater diffusion across Europe and the highest number of registered snakebites are six, namely: Vipera ammodytes, V. aspis, V. berus, V. latastei, V. seoanei and V. ursinii. Generally speaking, viper venom composition is characterised by many different toxin families, like phospholipases A2, snake venom serine proteases, snake venom metalloproteases, cysteine-rich secretory proteins, C-type lectins, disintegrins, haemorrhagic factors and coagulation inhibitors. A suspected snakebite is often associated with severe pain, erythema, oedema and, subsequently, the onset of an ecchymotic area around one or two visible fang marks. In the field, the affected limb should be immobilised and mildly compressed with a bandage, which can then be removed once the patient is being treated in hospital. The clinician should advise the patient to remain calm to reduce blood circulation and, therefore, decrease the spread of the toxins. In the case of pain, an analgesic therapy can be administered, the affected area can be treated with hydrogen peroxide or clean water. However, anti-inflammatory drugs and disinfection with alcohol or alcoholic substances should be avoided. For each patient, clinical chemistry and ECG are always a pre-requisite as well as the evaluation of the tetanus immunisation status and for which immunisation may be provided if needed. The treatment of any clinical complication, due to the envenomation, does not differ from treatments of emergency nature. Antivenom is recommended when signs of systemic envenomation exist or in case of advanced local or systemic progressive symptoms. Recommendations for future work concludes. The aim of this review is to support clinicians for the clinical management of viper envenomation, through taxonomic keys for main species identification, description of venom composition and mode of action of known toxins and provide a standardised clinical protocol and antivenom administration.

Snake bites by European vipers in Mainland France in 2017-2018: comparison of two antivenoms Viperfav® and Viperatab®

Context: Today, immunotherapy with Fab or F(ab')₂ fragments is considered as a gold standard treatment for patients bitten by vipers. We compared the efficiency of two antivenoms, Viperfav^® and Viperatab^®, in mainland France in 2017-2018 with data provided by the French poison control centre (PCC).Methods: Patients with a moderate (2a and 2b) or severe (3) envenomation after a European viper bite and treated with immunotherapy were included and the markers chosen were the risk of post-antivenom treatment worsening, duration of hospital stay and persistent functional discomfort on day 15. Statistical studies were based on multivariate data analysis.Results: Two hundred and ninety-seven cases were recorded. One hundred and eighty-two (61.3%) patients received Viperfav^® and 115 (38.7%) received Viperatab^®. Compared to Viperfav^®, use of Viperatab^® significantly increased the risk of post-antivenom treatment worsening (OR* 12.05; 95%CI [3.11; 46.70]; p < .001). No significant difference between these antivenoms was recorded with respect to the duration of hospital stay and persistent functional discomfort on day 15. Viperfav^® and Viperatab^® have a similar tolerance (p > .21). Otherwise, duration of hospitalisation was significantly increased by a delay of immunotherapy infusion of more than 12 h (OR 2.70; 95%CI [1.45-5.06]; p = .002) or a preventive administration of LMWH (OR 6.55; 95%CI [1.58-27.13]; p=.02).Discussion: While Viperfav^® and Viperatab^® have a similar tolerance, our data show that Viperatab^® was associated with a higher risk of post-antivenom treatment worsening compared to Viperfav^®. Furthermore, this study confirms that the antivenom should be used as soon as possible. Indeed, patients receiving the immunotherapy infusion from the grade 2b presented significantly more frequent exacerbated symptoms (OR 3.99; 95%CI [1.16-13.73]; p=.028) after the antivenom infusion compared to grade 2a group.Conclusions: Whereas no significant difference between these antivenoms was recorded with respect to the duration of hospital stay and persistent functional discomfort on day 15, use of Viperatab^®, compared to Viperfav^®, significantly increased the risk of post-antivenom treatment worsening (OR* 12.05; 95%CI [3.11; 46.70]; p < .001). Taken together, these data show that Viperfav^® is the treatment of choice for the management of snake bites in France.

Venomics of the asp viper Vipera aspis aspis from France

The asp viper Vipera aspis aspis is a venomous snake found in France, and despite its medical importance, the complete toxin repertoire produced is unknown. Here, we used a venomics approach to decipher the composition of its venom. Transcriptomic analysis revealed 80 venom-annotated sequences grouped into 16 gene families. Among the most represented toxins were snake venom metalloproteases (23%), phospholipases A2 (15%), serine proteases (13%), snake venom metalloprotease inhibitors (13%) and C-type lectins (12%). LC-MS of venoms revealed similar profiles regardless of the method of extraction (milking vs defensive bite). Proteomic analysis validated 57 venom-annotated transcriptomic sequences (>70%), including one for each of the 16 families, but also identified 7 sequences not initially annotated as venom proteins, including a serine protease, a disintegrin, a glutaminyl-peptide cyclotransferase, a proactivator polypeptide-like and 3 aminopeptidases. Interestingly, phospholipases A2 were the dominant proteins in the venom, among which included an ammodytoxin B-like sequence, which may explain the reported neurotoxicity following some asp viper envenomations. In total, 87 sequences were retrieved from the Vipera aspis aspis transcriptome and proteome, constituting a valuable resource that will help in understanding the toxinological basis of clinical signs of envenoming and for the mining of useful pharmacological compounds. BIOLOGICAL SIGNIFICANCE: The asp viper (Vipera aspis aspis) causes several hundred envenomations annually in France, including unusual cases with neurological signs, resulting in one death per year on average. Here, we performed a proteotranscriptomic analysis of V. a. aspis venom in order to provide a better understanding of its venom composition. We found that, as in other Vipera species, phospholipase A2 dominates in the venom, and the presence of a sequence related to ammodytoxin B may explain the reported neurotoxicity following some asp viper envenomations. Thus, this study will help in informing the toxinological basis of clinical signs of envenoming.

Protein structure of the venom in nine species of snake: from bio-compounds to possible healing agents

Due to its various structures in bio-compounds, snake venom is the indisputable result of evolutionary stages of molecules with an increasingly complex structure, high specificity, and of great importance for medicine because of their potential. The present study proposed an underpinning examination of venom composition from nine species of venomous snakes using a useful and replicable methodology. The objective was the extension of the evaluation of protein fractions in the field up to 230 kDa to permit possible identification of some fractions that are insufficiently studied. The gel capillary electrophoresis method on the chip was performed using an Agilent 2100 bioassay with the 80 and 230-LabChip Protein kits. Interpretation of electrophoresis was performed using the Protein 2100 expert (Agilent) test software as follows: a) Protein 80 (peak size scale): 1.60, 3.5, 6.50, 15.00, 28.00, 46.00, 63.00, 95.00 kDa; b) Protein 230 (peak size scale): 4.50, 7.00, 15.00, 28.00, 46.00, 63.00, 95.00, 150.00, 240.00 kDa. The screening revealed the presence of compounds with a molecular weight greater than 80 kDa, in the case of Vipera aspis and Vipera xantina palestinae. For V. aspis, a 125 kDa molecular weight pro-coagulant protein was identified, known as being involved in the reduction of plasma clotting time without any direct activity in the fibrinogen coagulation process. The samples examined on the Protein 230-LabChip electrophoresis chip can be considered as a novelty with possible uses in medicine, requiring further approaches by advanced proteomics techniques to confirm the intimate structural features and biological properties of snake venoms.

European viper envenomation recorded by French poison control centers: A clinical assessment and management study

INTRODUCTION

Immunotherapy is the gold standard treatment for patients bitten by European vipers in France; it significantly decreases morbidity, frequency and severity of complications and length of stay. A national prospective study was performed by all Poison Control Centers (PCC) to validate the emergency protocol for viper envenomations.

METHODS

This prospective study included all cases of viper bites in France, treated or not with Viperfav(®) in 2013.

RESULTS

In 2013, 277 cases of viper bites were collected: ratio M/F 2.1; mean aged 43 years (<15 years 25% 15-65 63% > 65 12%). The final severity was divided into 68 grades 0, 58 grades I, 62 grades IIA, 71 grades IIB and 18 grades III. One death was reported. Five patients had neurological signs. For the 114 patients who received Viperfav(®), all systemic signs disappeared in 5 h and in 24 h for biological and neurological signs. No severe anaphylactic reaction with Viperfav(®) was reported. Late Viperfav(®) administration increased the risk of functional impairment 15 days after the bite (OR = 3.21 p = 0.043). The administration of Low Molecular Weight Heparin (LMWH) increased the frequency of functional impairment to 15 days after the bite (OR = 6.38 p = 0.064), although Viperfav(®) was given in the first 18 h.

DISCUSSION

This study confirms the efficiency, safety and recommendation of an early administration of a single dose of Viperfav(®), LMWH should not be used. It also shows the extension of neurotoxic venom of vipers in France.

Synergistically acting PLA₂: peptide hemorrhagic complex from Daboia russelii venom

Snake venoms are complex mixture of enzymatic and non-enzymatic proteins. Non-covalent protein-protein interaction leads to protein complexes, which bring about enhanced pharmacological injuries by their synergistic action. Here we report identification and characterization of a new Daboia russelii hemorrhagic complex I (DR-HC-I) containing phospholipase A₂ (PLA₂) and non-enzymatic peptide. DR-HC-I was isolated from the venom of D. russelii by CM-Shepadex-C25 and gel permeation chromatography. Individual components were purified and identified by RP-HPL chromatography, mass spectrometry and N-terminal amino acid sequencing. DR-HC-I complex was lethal to mice with the LD₅₀ dose of 0.7 mg/kg body weight with hemorrhagic and neurotoxic properties. DR-HC-I complex consists of non-hemorrhagic PLA₂ and neurotoxic non-enzymatic peptide. The non-enzymatic peptide quenched the intrinsic fluorescence of PLA₂ in a dose dependent manner, signifying the synergistic interaction between two proteins. PLA₂ and peptide toxin in a 5:2 M ratio induced skin hemorrhage in mice with MHD 20 μg. However, addition of ANS (1-Anilino-8-naphthalene sulfonate) to DR-HC-I complex inhibited skin hemorrhagic effect and also synergic interaction. But there was no impact on PLA₂ due to this synergistic interaction, and indirect hemolytic or plasma re-calcification activity. However, the synergistic interaction of PLA₂ and non-enzymatic peptide contributes to the enhanced venom-induced hemorrhage and toxicity of Daboia russellii venom.

Management of snakebites in France

Although not a major health problem in Europe, snakebite in the old continent was the focus of recent studies to evaluate their overall incidence and define management techniques. The purpose of this three-part report is to present the experience of the Marseille Poison Centre with snakebite in France. The first section deals with viper envenomation that now benefits from a validated therapeutic protocol using of purified antivenom of proven efficacy and tolerance in patients showing grade 2 and 3 symptoms. The second section describes the highly variable snakebite situation in French overseas territories that include areas where local species require specialized management, e.g. Martinique and French Guiana. The third section involves the emerging problems associated with the keeping of exotic snakes as pets with problems related to the use of antivenoms from foreign countries. The exotic-snake pets fashion was at the origin of the creation of a national antivenom bank by two French poison centers (Angers and Marseille) to ensure prompt delivery of antivenoms for exotic snake envenomation anywhere in mainland France.

Asp Viper (Vipera aspis) envenomation: experience of the Marseille Poison Centre from 1996 to 2008

A retrospective case review study of viper envenomations collected by the Marseille's Poison Centre between 1996 and 2008 was performed.

RESULTS

174 cases were studied (52 grade 1 = G1, 90 G2 and 32 G3). G1 patients received symptomatic treatments (average hospital stay 0.96 day). One hundred and six (106) of the G2/G3 patients were treated with the antivenom Viperfav* (2.1+/-0.9 days in hospital), while 15 of them received symptomatic treatments only (plus one immediate death) (8.1+/-4 days in hospital, 2 of them died). The hospital stay was significantly reduced in the antivenom treated group (p < 0.001), and none of the 106 antivenom treated patients had immediate (anaphylaxis) or delayed (serum sickness) allergic reactions.

CONCLUSION

Viperfav* antivenom was safe and effective for treating asp viper venom-induced toxicity.

Isolation and characterization of "Reprotoxin", a novel protein complex from Daboia russelii snake venom

In snake venoms, non-covalent protein-protein interaction leads to protein complexes with synergistic and, at times, distinct pharmacological activities. Here we describe a new protein complex containing phospholipaseA(2) (PLA(2)), protease, and a trypsin inhibitor. It is isolated from the venom of Daboia russelii by gel permeation chromatography, on a Sephadex G-75 column. This 44.6 kDa complex exhibits only phospholipase A(2) activity. In the presence of 8M urea it is well resolved into protease (29.1 kDa), PLA(2) (13 kDa), and trypsin inhibitor (6.5 kDa) peaks. The complex showed an LD(50) of 5.06 mg/kg body weight in mice. It inhibited the frequency of spontaneous release of neurotransmitter in hippocampal neurons. It also caused peritoneal bleeding, and edema in the mouse foot pads. Interestingly, the complex caused degeneration of both the germ cells and the mouse Leydig cells of mouse testis. A significant reduction in both the diameter of the seminiferous tubules and height of the seminiferous epithelia were observed following intraperitoneal injection of the sub-lethal dose (3 mg/kg body weight). This effect of the toxin is supported by the increase in the activities of acid and alkaline phosphatases and the nitric oxide content in the testes, and a decrease in the ATPase activity. Because of its potent organ atrophic effects on the reproductive organs, the toxin is named "Reprotoxin". This is the first report demonstrating toxicity to the reproductive system by a toxin isolated from snake venom.

Phospholipase A2 diversity and polymorphism in European viper venoms: Paradoxical molecular evolution in Viperinae

We report the diversity and polymorphism of phospholipase A(2) (PLA(2)) transcripts from snakes belonging to nine European viper subspecies. This diversity results in the expression of a combination of six PLA(2) species--ammodytin I1, ammodytin I2, ammodytin L, ammodytoxin, vaspin A and vaspin B--with 19 known isoforms of the first five of these species. Most of the European viper venoms studied contained either a myotoxin or a neurotoxin, and all contained ammodytin I1 and ammodytin I2. There is no evidence that a given pattern of PLA(2) species constitutes a taxonomic criterion, and isoform analysis would be required for such discrimination. Analysis of the phylogenetic relationships between PLA(2) species from European vipers and those of other members of the Viperinae revealed a strong correlation between the geographical source of the viper and the clustering seen for the different isoforms, for each PLA(2) species. The K(a)/K(s) values calculated for the mature protein-coding region of paralogous genes showed that ratios for pairs including vaspin B or one ammodytoxin isoform were greater than 1.09, whereas those for most of the remaining pairs were less than 1. Different patterns of mutation were observed in comparisons of the different PLA(2) isoforms. The mechanisms directing a mutation toward a precise exon remain unresolved.

Reappraisal of Vipera aspis venom neurotoxicity

Background

The variation of venom composition with geography is an important aspect of intraspecific variability in the Vipera genus, although causes of this variability remain unclear. The diversity of snake venom is important both for our understanding of venomous snake evolution and for the preparation of relevant antivenoms to treat envenomations. A geographic intraspecific variation in snake venom composition was recently reported for Vipera aspis aspis venom in France. Since 1992, cases of human envenomation after Vipera aspis aspis bites in south-east France involving unexpected neurological signs were regularly reported. The presence of genes encoding PLA₂ neurotoxins in the Vaa snake genome led us to investigate any neurological symptom associated with snake bites in other regions of France and in neighboring countries. In parallel, we used several approaches to characterize the venom PLA₂ composition of the snakes captured in the same areas.

Methodology/Principal Findings

We conducted an epidemiological survey of snake bites in various regions of France. In parallel, we carried out the analysis of the genes and the transcripts encoding venom PLA₂s. We used SELDI technology to study the diversity of PLA₂ in various venom samples. Neurological signs (mainly cranial nerve disturbances) were reported after snake bites in three regions of France: Languedoc-Roussillon, Midi-Pyrénées and Provence-Alpes-Côte d'Azur. Genomes of Vipera aspis snakes from south-east France were shown to contain ammodytoxin isoforms never described in the genome of Vipera aspis from other French regions. Surprisingly, transcripts encoding venom neurotoxic PLA₂s were found in snakes of Massif Central region. Accordingly, SELDI analysis of PLA₂ venom composition confirmed the existence of population of neurotoxic Vipera aspis snakes in the west part of the Massif Central mountains.

Conclusions/Significance

The association of epidemiological studies to genetic, biochemical and immunochemical analyses of snake venoms allowed a good evaluation of the potential neurotoxicity of snake bites. A correlation was found between the expression of neurological symptoms in humans and the intensity of the cross-reaction of venoms with anti-ammodytoxin antibodies, which is correlated with the level of neurotoxin (vaspin and/or ammodytoxin) expression in the venom. The origin of the two recently identified neurotoxic snake populations is discussed according to venom PLA₂ genome and transcriptome data.

Venom phospholipases of Russell's vipers from Myanmar and eastern India--cloning, characterization and phylogeographic analysis

Venoms of Russell's vipers (genus Daboia) are known for their deadly coagulopathic and other effects. We herein studied various isoforms of venom phospholipases A(2) (PLAs) from two Daboia species at their geographic boundary. From Myanmar Daboia siamensis venom (designated as DsM), four PLAs (designated DsM-aI, aI', aII' and bI') were purified, and the cDNAs encoding two acidic (DsM-aI and aII) and two basic PLAs (DsM-bI and S1) were also cloned from its venom-glands. DsM-S1 is identical to the major venom PLA of southern India Daboia russelii, but the protein is absent from the venom. Additionally, four PLAs (designated DrK-aI, aII, bI and bII) were cloned from cDNA obtained from venom glands of a Kolkata D. russelii, and the PLAs were purified from the pooled venom (designated as DrK). The acidic DrK-aI is the most neurotoxic and lethal among these PLAs; DsM-aI which differs from DrK-aI by only the Phe2 substitution shows greatly reduced enzymatic activity and lethality. Both acidic PLAs do not form dimeric complex with basic PLAs in the same venoms. DsM-bI' is neurotoxic and lethal but its orthologous DrK-bI (97% identical to DsM-bI') is a much weaker toxin. Given the fact that most of the orthologous PLAs of DrK and DsM share 97-100% sequence identity, Daboia vipers of Myanmar and Kolkata must be closely related. Molecular phylogenetic analyses on 30 venom PLAs of Eurasian vipers' revealed co-evolution of five subtypes of venom PLAs in both Daboia and Vipera genera. Our results shed light on the intra- and inter-species variations and structure-function relationships of viperid venom PLAs.

Venom phospholipases A2 of bamboo viper (Trimeresurus stejnegeri): molecular characterization, geographic variations and evidence of multiple ancestries

Phospholipases A2 (PLA2s) were purified from the Trimeresurus stejnegeri venom obtained from various localities in Taiwan and three provinces in China, by gel filtration followed by reversed-phase HPLC. The precise molecular mass and N-terminal sequence of each PLA2 were determined. In addition to the six previously documented PLA2 isoforms of this species, we identified ten novel isoforms. The venom gland cDNAs of individual specimens of the viper from four localities were used for PCR and subsequent cloning of the PLA2s. The molecular masses and partial sequences of most of the purified PLA2s matched with those deduced from a total of 13 distinct cDNA sequences of these clones. Besides the commonly known Asp49 or Lys-49 PLA2s of crotalid venoms, a novel type of PLA2 with Asn-49 substitution at the Ca2+-binding site was discovered. This type of PLA2 is non-catalytic, but may cause local oedema and appears to be a venom marker of many tree vipers. In particular, we showed that T. stejnegeri displayed high geographic variations of the PLA2s within and between their Taiwanese and Chinese populations, which can be explained by geological isolation and prey ecology. A phylogenetic tree of the acidic venom PLA2s of this species and other related Asian vipers reveals that T. stejnegeri contains venom genes related to those from several sympatric pit vipers, including the genera Tropedolaemus and Gloydius besides the Trimeresurus itself. Taken together, these findings may explain the exceptionally high variations in the venom as well as the evolutionary advantage of this species.

Crystallization and preliminary X-ray diffraction studies of a toxic phospholipase A2 from the venom of Vipera ammodytes meridionalis complexed to a synthetic inhibitor

A toxic phospholipase A(2) (PLA(2)) is isolated from the neurotoxic complex Vipoxin, the major lethal component of the venom of Vipera ammodytes meridionalis. The enzyme is complexed to the synthetic inhibitor elaidoylamide and crystallized. The crystals belong to the space group P2(1)2(1)2(1), with unit cell dimensions a=46.57 A, b=82.68 A, c=119.47 A and beta=90 degrees. Initial diffraction data to 3.3 A resolution are collected.

Sequences and structural organization of phospholipase A2 genes from Vipera aspis aspis, V. aspis zinnikeri and Vipera berus berus venom. Identification of the origin of a new viper population based on ammodytin I1 heterogeneity

We used a PCR-based method to determine the genomic DNA sequences encoding phospholipases A2 (PLA2s) from the venoms of Vipera aspis aspis (V. a. aspis), Vipera aspis zinnikeri (V. a. zinnikeri), Vipera berus berus (V. b. berus) and a neurotoxic V. a. aspis snake (neurotoxic V. a. aspis) from a population responsible for unusual neurotoxic envenomations in south-east France. We sequenced five groups of genes, each corresponding to a different PLA2. The genes encoding the A and B chains of vaspin from the neurotoxic V. a. aspis, PLA2-I from V. a. zinnikeri, and the anticoagulant PLA2 from V. b. berus are described here. Single nucleotide differences leading to amino-acid substitutions were observed both between genes encoding the same PLA2 and between genes encoding different PLA2s. These differences were clustered in exons 3 and 5, potentially altering the biological activities of PLA2. The distribution and characteristics of the PLA2 genes differed according to the species or subspecies. We characterized for the first time genes encoding neurotoxins from the V. a. aspis and V. b. berus snakes of central France. Genes encoding ammodytins I1 and I2, described previously in Vipera ammodytes ammodytes (V. am. ammodytes), were also present in V. a. aspis and V. b. berus. Three different ammodytin I1 gene sequences were characterized: one from V. b. berus, the second from V. a. aspis, V. a. zinnikeri and the neurotoxic V. a. aspis, and the third from the neurotoxic V. a. aspis. This third sequence was identical with the reported sequence of the V. am. ammodytes ammodytin I1 gene. Genes encoding monomeric neurotoxins of V. am. ammodytes venom, ammodytoxins A, B and C, and the Bov-B LINE retroposon, a phylogenetic marker found in V. am. ammodytes genome, were identified in the genome of the neurotoxic V. a. aspis. These results suggest that the population of neurotoxic V. a. aspis snakes from south-east France may have resulted from interbreeding between V. a. aspis and V. am. ammodytes.