Indian green pit vipers: A lesser-known snake group of north-east India

Green pit vipers are one of the most widely distributed group of venomous snakes in south-east Asia. In Indian, green pit vipers are found in the Northern and North-eastern states spreading across eastern and central India and one of the lesser studied venoms. High morphological similarity among them has been a long-established challenge for species identification, however, a total of six species of Indian green pit viper belonging to genus Trimeresurus, Popeia and Viridovipera has been reported from North-east India. Biochemical and biological studies have revealed that venom exhibits substantial variation in protein expression level along with functional variability. The symptoms of envenomation are painful swelling at bite site, bleeding, necrosis along with systemic toxicity such as prolonged coagulopathy. Clinical data of green pit viper envenomated patients from Demow community health centre, Assam advocated against the use of Indian polyvalent antivenom pressing the need for a suitable antivenom for the treatment of green pit viper envenomation. To design effective and specific antivenom for green pit vipers, unveiling the proteome profile of these snakes is needed. In this study, a comparative venomic of green pit vipers of Northern and North-eastern India, their clinical manifestation as well as treatment protocol has been reviewed.

An agonist of CXCR4 induces a rapid recovery from the neurotoxic effects of Vipera ammodytes and Vipera aspis venoms

People bitten by Alpine vipers are usually treated with antivenom antisera to prevent the noxious consequences caused by the injected venom. However, this treatment suffers from a number of drawbacks and additional therapies are necessary. The venoms of Vipera ammodytes and of Vipera aspis are neurotoxic and cause muscle paralysis by inducing neurodegeneration of motor axon terminals because they contain a presynaptic acting sPLA2 neurotoxin. We have recently found that any type of damage to motor axons is followed by the expression and activation of the intercellular signaling axis consisting of the CXCR4 receptor present on the membrane of the axon stump and of its ligand, the chemokine CXCL12 released by activated terminal Schwann cells. We show here that also V. ammodytes and V. aspis venoms cause the expression of the CXCL12-CXCR4 axis. We also show that a small molecule agonist of CXCR4, dubbed NUCC-390, induces a rapid regeneration of the motor axon terminal with functional recovery of the neuromuscular junction. These findings qualify NUCC-390 as a promising novel therapeutics capable of improving the recovery from the paralysis caused by the snakebite of the two neurotoxic Alpine vipers.

β-keto amyrin isolated from Cryptostegia grandiflora R. br. inhibits inflammation caused by Daboia russellii viper venom: Direct binding of β-keto amyrin to phospholipase A2

The search for mechanism-based anti-inflammatory therapies is of fundamental importance to avoid undesired off-target effects. Phospholipase A2 (PLA2) activity is a potential molecular target for anti-inflammatory drugs because it fuels arachidonic acid needed to synthesize inflammation mediators, such as prostaglandins. Herein, we aim to investigate the molecular mechanism by which β-keto amyrin isolated from a methanolic extract of Cryptostegia grandiflora R. Br. Leaves can inhibit inflammation caused by Daboia russellii viper (DR) venom that mainly contains PLA2. We found that β-keto amyrin neutralizes DR venom-induced paw-edema in a mouse model. Molecular docking of PLA2 with β-keto amyrin complex resulted in a higher binding energy score of -8.86 kcal/mol and an inhibition constant of 611.7 nM. Diclofenac had a binding energy of -7.04 kcal/mol and an IC50 value of 620 nM, which predicts a poorer binding interaction than β-keto amyrin. The higher conformational stability of β-keto amyrin interaction compared to diclofenac is confirmed by molecular dynamics simulation. β-keto amyrin isolated from C. grandiflora inhibits the PLA2 activity contained in Daboia russellii viper venom. The anti-inflammatory property of β-keto amyrin is due to its direct binding into the active site of PLA2, thus inhibiting its enzyme activity.

In vitro immunoreactivity and in vivo neutralization of Trimeresurus gracilis venom with antivenoms targeting four pit viper species

Snakebite envenomation is a significant global health issue that requires specific antivenom treatments. In Taiwan, available antivenoms target a variety of snakes, but none specifically target Trimeresurus gracilis, an endemic and protected species found in the high mountain areas of Taiwan. This study evaluated the effectiveness of existing antivenoms against T. gracilis venom, focusing on a bivalent antivenom developed for Trimeresurus stejnegeri and Protobothrops mucrosquamatus (TsPmAV), as well as monovalent antivenoms for Deinagkistrodon acutus (DaAV) and Gloydius brevicaudus (GbAV). Our research involved in vivo toxicity testing in mice and in vitro immunobinding experiments using (chaotropic) enzyme-linked immunosorbent assays, comparing venoms from four pit viper species (T. gracilis, T. stejnegeri, P. mucrosquamatus, and D. acutus) with three types of antivenoms. These findings indicate that TsPmAV partially neutralized T. gracilis venom, marginally surpassing the efficacy of DaAV. In vitro tests revealed that GbAV displayed higher binding capacities toward T. gracilis venom than TsPmAV or DaAV. Comparisons of electrophoretic profiles also reveal that T. gracilis venom has fewer snake venom C-type lectin like proteins than D. acutus, and has more P-I snake venom metalloproteases or fewer phospholipase A2 than G. brevicaudus, T. stejnegeri, or P. mucrosquamatus. This study highlights the need for antivenoms that specifically target T. gracilis, as current treatments using TsPmAV show limited effectiveness in neutralizing local effects in patients. These findings provide crucial insights into clinical treatment protocols and contribute to the understanding of the evolutionary adaptation of snake venom, aiding in the development of more effective antivenoms for human health.

Changes in attachment and metabolic activity of rat neonatal cardiomyocytes and nonmyocytes caused by Macrovipera lebetina obtusa venom

The Caucasian viper Macrovipera lebetina obtusa (MLO) is one of the most prevalent and venomous snakes in the Caucasus and the surrounding regions, yet the effects of MLO venom on cardiac function remain largely unknown. We examined the influence of MLO venom (crude and with inhibited metalloproteinases and phospholipase A2) on attachment and metabolic activity of rat neonatal cardiomyocytes (CM) and nonmyocytes (nCM), assessed at 1 and 24 h. After exposing both CM and nCM to varying concentrations of MLO venom, we observed immediate cytotoxic effects at a concentration of 100 μg/ml, causing detachment from the culture substrate. At lower MLO venom concentrations both cell types detached in a dose-dependent manner. Inhibition of MLO venom metalloproteinases significantly improved CM and nCM attachment after 1-hour exposure. At 24-hour exposure to metalloproteinases inhibited venom statistically significant enhancement was observed only in nCM attachment. However, metabolic activity of CM and nCM did not decrease upon exposure to the lower dose of the venom. Moreover, we demonstrated that metalloproteinases and phospholipases A2 are not the components of the MLO venom that change metabolic activity of both CM and nCM. These results provide a valuable platform to study the impact of MLO venom on prey cardiac function. They also call for further exploration of individual venom components for pharmaceutical purposes.

Differential effects of the venoms of Russell's viper and Indian cobra on human myoblasts

Local tissue damage following snakebite envenoming remains a poorly researched area. To develop better strategies to treat snakebites, it is critical to understand the mechanisms through which venom toxins induce envenomation effects including local tissue damage. Here, we demonstrate how the venoms of two medically important Indian snakes (Russell's viper and cobra) affect human skeletal muscle using a cultured human myoblast cell line. The data suggest that both venoms affect the viability of myoblasts. Russell's viper venom reduced the total number of cells, their migration, and the area of focal adhesions. It also suppressed myogenic differentiation and induced muscle atrophy. While cobra venom decreased the viability, it did not largely affect cell migration and focal adhesions. Cobra venom affected the formation of myotubes and induced atrophy. Cobra venom-induced atrophy could not be reversed by small molecule inhibitors such as varespladib (a phospholipase A2 inhibitor) and prinomastat (a metalloprotease inhibitor), and soluble activin type IIb receptor (a molecule used to promote regeneration of skeletal muscle), although the antivenom (raised against the Indian 'Big Four' snakes) has attenuated the effects. However, all these molecules rescued the myotubes from Russell's viper venom-induced atrophy. This study demonstrates key steps in the muscle regeneration process that are affected by both Indian Russell's viper and cobra venoms and offers insights into the potential causes of clinical features displayed in envenomed victims. Further research is required to investigate the molecular mechanisms of venom-induced myotoxicity under in vivo settings and develop better therapies for snakebite-induced muscle damage.

Immunoreactivity and neutralization efficacy of Pakistani Viper Antivenom (PVAV) against venoms of Saw-scaled Vipers (Echis carinatus subspp.) and Western Russell's Vipers (Daboia russelii) from the Indian subcontinent

Snakebite envenoming (SBE) is a priority Neglected Tropical Disease listed by the World Health Organization. South Asia is heavily affected, and virtually all countries in the region import polyvalent antivenom products from India for clinical use. The imported antivenoms, however, have suboptimal effectiveness due to geographical venom variation. Recently, a domestic bivalent product, named Pakistani Viper Antivenom (PVAV) has been developed specifically for Pakistani vipers, Echis carinatus sochureki and Daboia russelii. As a bivalent viperid antivenom, it is unknown yet if PVAV exhibits higher immunological binding and neutralization activities against viper venoms from distant locales compared with polyvalent antivenoms manufactured in India. This study thus examined the preclinical efficacy of PVAV against venoms of Western Russell's Vipers and Saw-scaled Viper subspecies from selected locales in the Indian subcontinent. PVAV generally outperformed the commonly used VINS polyvalent antivenom (VPAV, manufactured in India) in binding toward venoms, and showed superior or comparable neutralization efficacy against the venom procoagulant and hemorrhagic effects of Saw-scaled Vipers as well as Russell's Vipers from Pakistan and Sri Lanka. Based on normalized potency values, PVAV is far more potent than VPAV in neutralizing the lethality of all viper venoms, except that of the Indian Russell's Viper. The study shows conserved antigenicity of toxins responsible for major toxicity across these viperid venoms, and suggests the feasible production of a viper-specific antivenom with higher potency and broader geographical utility for the region.

Proteome analysis of Daboia russelii venom, a medically important snake from the Indian sub-continent

Daboia russelii is a category-I medically important snake throughout the Indian sub-continent contributing to majority of snakebite incidences in this part of the world. As such, extensive studies on its venom composition and search of efficient and appropriate interventions for its treatment become crucial. In this study, the proteome of Daboia russelii venom from Tanore, Rajshahi, Bangladesh was profiled using a combination of chromatographic and mass spectrometric techniques. A total of 37 different proteins belonging to 11 different snake venom protein families were detected. Proteomics analysis revealed the presence of major phospholipase A2 toxins. Daboiatoxin (both A and B subunits), the main lethal PLA2 toxin in the venom of Daboia siamensis (Myanmar viper) which is neurotoxic, myotoxic and cytotoxic was detected. Presence of Daboxin P, which is a major protein in the venom of Indian Daboia russelii with strong anticoagulant activity, was also observed. Inconsistent distribution of such lethal toxins in the venom of same species calls for more investigations of snake venoms from lesser explored regions and formulation of better alternatives to the current antivenom therapy for efficient treatment.

Structural, biochemical and immunochemical characterization of an acidic phospholipase A2 from Lachesis acrochorda (Viperidae: Crotalinae) venom

Viperids of the genus Lachesis, also known as bushmasters, are capable of injecting great amounts of venom that cause severe envenomation incidents. Since phospholipases type A2 are mainly involved in edema and myonecrosis within the snakebite sites, in this work, the isolation, amino acid sequence and biochemical characterization of the first phospholipase type A2 from the venom of Lachesis acrochorda, named Lacro_PLA2, is described. Lacro_PLA2 is an acidic aspartic 49 calcium-dependent phospholipase A2 with 93% similarity to the L. stenophrys phospholipase. Lacro_PLA2 has a molecular mass of 13,969.7 Da and an experimental isoelectric point around 5.3. A combination of N-terminal Edman degradation and MS/MS spectrometry analyses revealed that Lacro_PLA2 contains 122 residues including 14 cysteines that form 7 disulfide bridges. A predicted 3D model shows a high resemblance to other viperid phospholipases. Nevertheless, immunochemical and phospholipase neutralization tests revealed a notorious level of immunorecognition of the isolated protein by two polyclonal antibodies from viperids from different genus, which suggest that Lacro_PLA2 resembles more to bothropic phospholipases. Lacro_PLA2 also showed significantly high edema activity when was injected into mice; so, it could be an alternative antigen in the development of antibodies against toxins of this group of viperids, seeking to improve commercial polyclonal antivenoms.

Serum Cholesterol Concentration on Admission in 415 Dogs Envenomated by Daboia (Vipera) palaestinae as a Marker of Envenomation Severity and Outcome-A Retrospective Study

Daboia (Vipera) palaestinae (Dp), accounts for most envenomations in humans and dogs in Israel. In humans envenomed by Dp, serum cholesterol concentration (sChol) is inversely correlated with envenomation severity. This study examined the utility of sChol upon admission in dogs envenomed by Dp as an envenomation severity and outcome marker. Data upon admission, including sChol, were retrospectively collected from the medical records of dogs with proven Dp envenomation. The study included 415 dogs. The mortality rate was 11%. The heart rate upon admission was higher in non-survivors than in survivors. Signs of bleeding or hematoma and circulatory shock signs were more frequent among non-survivors compared to survivors. sChol, the platelet count, and serum albumin concentration (sAlb) were lower, while serum creatinine concentration was higher among non-survivors. sChol and sAlb were moderately, positively, and significantly correlated. sChol was significantly, negatively, albeit weakly, correlated with the length of hospitalization and the heart rate. sChol was lower in dogs admitted >12 h post-envenomation than in those admitted later. In dogs, sChol upon admission is a potential marker of severity and outcome of Dp envenomation. The platelet count, sAlb, and sCreat might also be potential markers.

Cold Finger: Raynaud Phenomenon Following Snakebite Envenoming by Nikolsky's Viper (Vipera berus nikolskii)

A field biologist was bitten by a female Nikolsky's viper (Vipera berus nikolskii) in Kharkiv Oblast, Ukraine. Two months later, the patient began to experience cold-induced vasospasm of the affected digit diagnosed as acquired Raynaud phenomenon. The patient had more than 30 occurrences during the single winter following the bite, but the signs and symptoms of Raynaud phenomenon disappeared with the end of winter. This report describes the case and puts it into context with the literature on the topic of toxin-induced peripheral vasospastic disorders and their potential importance in snakebite envenoming.

Severity of a Vipera palaestinae envenomation objective findings associated with a complicated hospitalization course following a Vipera palaestinae bite

The most common snake in Israel, responsible for most snakebites is Vipera palaestinae (VP). Envenomation signs and symptoms vary from local manifestations to systemic reactions that may end with death. Antivenom treatment, given to high-risk patients, reduces complications and mortality but carries risks. As of now, there is no standardized protocol for adults bitten by VP based on objective clinical and laboratory findings. We conducted A retrospective analysis of 159 patients admitted to two large tertiary care institutions in the center (Hadassah University Medical Center) and south (Soroka University Medical Center) of Israel with Vipera palaestinae bites during 1990-2017. Epidemiological and clinical data were extracted, and the patients were divided into two groups based on hospitalization time (over or under 48 h). 159 patients were included in this study. The average hospitalization time was 66.1 h, with 49.7% of patients admitted over 48 h. The main factors that statistically correlated with a longer hospitalization time were: Male gender, lower extremity bite, platelets lower than 150 K at presentation, leukocyte count of over 10 K at presentation and elevated D-Dimer levels. This study provides factors which are associated with a severe VP envenomation. These clinical or laboratory findings (along with accompanying clinical symptoms) are associated with a higher risk of a prolonged hospitalization with more complications and may require a more intensive treatment and monitoring.

Thromboelastography Use to Guide Resuscitation and Antivenom Administration after Gaboon Viper Bite

The Gaboon viper (Bitis gabonica) is an exotic snake native to sub-Saharan Africa. Gaboon viper venom is an extremely toxic hemotoxin, causing severe coagulopathy and local tissue necrosis. These are not aggressive snakes and therefore bites involving humans are rare and there is not a substantial amount of literature documenting how to manage these injuries and resultant coagulopathies. We report a 29-year-old male presenting 3 hours after a Gaboon viper envenomation resulting in coagulopathy requiring massive resuscitation and multiple doses of antivenom. The patient received various blood products based on thromboelastography (TEG) and also underwent early continuous renal replacement therapy (CRRT) to assist in correction of severe acidosis and acute renal failure. The combination of TEG to guide resuscitation, administration of antivenom, and early implementation of CRRT allowed our team to correct venom-induced consumptive coagulopathy and ultimately allow the patient to survive following this extremely deadly Gaboon viper envenomation.

Kounis syndrome following an anaphylactic reaction to antivenom in a patient with Russell's viper (Daboia russelii) bite: A case report

Kounis syndrome is the occurrence of acute coronary syndrome associated with mast cell and platelet activation in the setting of allergic or anaphylactic insults. Kounis syndrome has been previously reported following snake envenoming rarely, with or without antivenom therapy. We report a case of inferolateral ST elevation myocardial infarction 32 hours from a confirmed Russell's viper bite. He also had an anaphylactic reaction soon after antivenom. The absence of underlying atheromatous coronary artery disease during subsequent cardiac imaging was suggestive of a diagnosis of a type I variant of Kounis syndrome. Chest pain completely resolved by day 6 following initiation of standard treatment for acute coronary syndrome. Concurrence of allergic features and acute coronary syndrome in a snakebite patient following antivenom therapy should alert clinicians to the possibility of Kounis syndrome, which should be diagnosed with a high degree of clinical suspicion.

The Contribution of Phospholipase A2 and Metalloproteinases to the Synergistic Action of Viper Venom on the Bioenergetic Profile of Vero Cells

Increasing concern about the use of animal models has stimulated the development of in vitro cell culture models for analysis of the biological effects of snake venoms. However, the complexity of animal venoms and the extreme synergy of the venom components during envenomation calls for critical review and analysis. The epithelium is a primary target for injected viper venom's toxic substances, and therefore, is a focus in modern toxinology. We used the Vero epithelial cell line as a model to compare the actions of a crude Macrovipera lebetina obtusa (Levantine viper) venom with the actions of the same venom with two key enzymatic components inhibited (specifically, phospholipase A2 (PLA2) and metalloproteinases) in the bioenergetic cellular response, i.e., oxygen uptake and reactive oxygen species generation. In addition to the rate of free-radical oxidation and lipid peroxidation, we measured real-time mitochondrial respiration (based on the oxygen consumption rate) and glycolysis (based on the extracellular acidification rate) using a Seahorse analyzer. Our data show that viper venom drives an increase in both glycolysis and respiration in Vero cells, while the blockage of PLA2 or/and metalloproteinases affects only the rates of the oxidative phosphorylation. PLA2-blocking in venom also increases cytotoxic activity and the overproduction of reactive oxygen species. These data show that certain components of the venom may have a different effect within the venom cocktail other than the purified enzymes due to the synergy of the venom components.

Development of Wunderlich syndrome following a Russell's viper bite

Snakebite envenomation is a high priority neglected tropical disease that predominantly affects rural communities living in developing countries. Due to myriad of complications including coagulopathies, neurotoxicity, nephrotoxicity and local tissue destruction, treating snakebite victims is a major challenge for clinicians. Russell's viper (Daboia russelii) is one of the 'Big Four' venomous snakes in India, and it is responsible for the most snakebite-induced deaths and disabilities. Acute kidney injury occurs frequently following Russell's viper bites and it is a critical factor contributing to disabilities, deaths and excessive treatment costs. In addition to commonly observed envenomation effects, Russell's viper bites induce some rare complications such as priapism, sialolithiasis and splenic rupture. Here, we report a case of Wunderlich syndrome that developed in a 22-year-old male following a Russell's viper bite. The patient displayed severe coagulopathies, abdominal tenderness, and hypotension. Notably, a peri-nephric haematoma was identified through ultrasound and computerised tomographic imaging. The haemorrhage was successfully treated using angioembolisation, and the patient recovered without any difficulties. Although a clinical condition such as this is rare, it is important to create awareness among treating clinicians about its occurrence, diagnosis and clinical management.

Acute Myocardial Infarction After Russell's Viper (Daboia russelii) Bite

Russell's viper (Daboia russelii) is a deadly venomous snake that causes most snakebite deaths in Sri Lanka. It is widely distributed all over the country, and it commonly causes venom-induced consumption coagulopathy and neuroparalysis. Cardiotoxic manifestations after Russell's viper bites are rare. We report a 60-year-old man diagnosed with ST-elevation myocardial infarction after a proved Russell's viper bite.

Exploring the Utility of Recombinant Snake Venom Serine Protease Toxins as Immunogens for Generating Experimental Snakebite Antivenoms

Snakebite is a neglected tropical disease that causes high rates of global mortality and morbidity. Although snakebite can cause a variety of pathologies in victims, haemotoxic effects are particularly common and are typically characterised by haemorrhage and/or venom-induced consumption coagulopathy. Despite polyclonal antibody-based antivenoms being the mainstay life-saving therapy for snakebite, they are associated with limited cross-snake species efficacy, as there is often extensive toxin variation between snake venoms, including those used as immunogens for antivenom production. This restricts the therapeutic utility of any antivenom to certain geographical regions. In this study, we explored the feasibility of using recombinantly expressed toxins as immunogens to stimulate focused, pathology-specific, antibodies in order to broadly counteract specific toxins associated with snakebite envenoming. Three snake venom serine proteases (SVSP) toxins, sourced from geographically diverse and medically important viper snake venoms, were successfully expressed in HEK293F mammalian cells and used for murine immunisation. Analyses of the resulting antibody responses revealed that ancrod and RVV-V stimulated the strongest immune responses, and that experimental antivenoms directed against these recombinant SVSP toxins, and a mixture of the three different immunogens, extensively recognised and exhibited immunological binding towards a variety of native snake venoms. While the experimental antivenoms showed some reduction in abnormal clotting parameters stimulated by the toxin immunogens and crude venom, specifically reducing the depletion of fibrinogen levels and prolongation of prothrombin times, fibrinogen degradation experiments revealed that they broadly protected against venom- and toxin-induced fibrinogenolytic functional activities. Overall, our findings further strengthen the case for the use of recombinant venom toxins as supplemental immunogens to stimulate focused and desirable antibody responses capable of neutralising venom-induced pathological effects, and therefore potentially circumventing some of the limitations associated with current snakebite therapies.

Mild venom-induced consumption coagulopathy associated with thrombotic microangiopathy following a juvenile Russell's viper (Daboia russelii) envenoming: A case report

Russell's viper envenoming causes venom-induced consumption coagulopathy (VICC) within hours of a bite, which is associated with thrombotic microangiopathy (TMA) and acute kidney injury (AKI) in a proportion of cases. We report a juvenile Russell's viper bite in which a patient developed mild VICC after the usual 24-h observation period, which was subsequently associated with severe AKI due to TMA. This shows the clinical importance of detecting and treating mild VICC, which may be delayed or not detected with bedside clotting tests.

Isolated Ptosis Following a Vipera aspis Bite

In Spain, snakebites are uncommon medical emergencies that cause barely 100 hospitalizations annually. Most of the venomous bites are by snakes of the Viperidae family. Venom from Vipera snakes is reported to have cytotoxic and hematotoxic effects, and neurological effects have also been described. Ptosis (cranial nerve III palsy) is the most common sign, although any cranial nerve can be affected. We describe isolated ptosis, which was very likely after a Vipera aspis bite in the East Catalonian Pyrenees. No antivenom was administered. The ptosis resolved spontaneously within 10 h. Although neurologic findings are usually mild, they indicate a moderate or severe envenomation. Treating snakebites can be challenging for clinicians, especially when there are uncommon clinical manifestations. A toxicologist at a poison center should be consulted to help guide management. Development of local protocols may provide clinical support.

In Vitro Neutralization of the Myotoxicity of Australian Mulga Snake (Pseudechis australis) and Sri Lankan Russell's Viper (Daboia russelii) Venoms by Australian and Indian Polyvalent Antivenoms

We studied the neutralisation of Sri Lankan Russell's viper (Daboia russelii) and Australian mulga snake (Pseudechis australis) venom-induced myotoxicity by Indian (Vins and Bharat) and Australian (Seqirus) polyvalent antivenoms, using the in vitro chick biventer skeletal muscle preparation. Prior addition of Bharat or Vins antivenoms abolished D. russelii venom (30 µg/mL)-mediated inhibition of direct twitches, while Australian polyvalent antivenom was not protective. Bharat antivenom prevented, while Vins and Australian polyvalent antivenoms partially prevented, the inhibition of responses to exogenous KCl. Myotoxicity of Mulga venom (10 µg/mL) was fully neutralised by the prior addition of Australian polyvalent antivenom, partially neutralised by Vins antivenom but not by Bharat antivenom. Although the myotoxicity of both venoms was partially prevented by homologous antivenoms when added 5 min after the venom, with an increasing time delay between venom and antivenom, the reversal of myotoxicity gradually decreased. However, antivenoms partially prevented myotoxicity even 60 min after venom. The effect of antivenoms on already initiated myotoxicity was comparable to physical removal of the toxins by washing the bath at similar time points, indicating that the action of the antivenoms on myotoxicity is likely to be due to trapping the toxins or steric hindrance within the circulation, not allowing the toxins to reach target sites in muscles.

Circulating intestinal fatty acid binding protein and intestinal toxicity in Russell's viper envenomation

OBJECTIVE

Abdominal pain is known to be an early clinical predictor of severe systemic Russell's viper (RV) envenomation and is often associated with the later development of coagulopathy and neurotoxicity. The mechanism of abdominal pain is unknown, but we postulated it might be due to intestinal microvascular endothelial gut damage. Gut-toxicity can be detected using the novel biomarker Intestinal Fatty Acid Binding Protein (IFABP). We also wanted to explore the mechanisms and consequences of this toxicity by measuring procalcitonin as a specific marker of sepsis triggered by bacterial endotoxin, and serum cystatin-C (CysC) as a measure of acute kidney injury. We hypothesised that severe gut-injury might lead to gut-barrier failure, translocation of gastrointestinal microorganisms, associated sepsis and systemic inflammatory response syndrome (SIRS), with a possible exacerbation of snake-bite severity, including acute kidney injury that was previously attributed to direct venom effects.

METHODS

Serial plasma samples previously collected from 16 RV envenomations with abdominal pain, 15 RV envenomations without abdominal pain and 25 healthy controls were assayed for IFABP. A subgroup of these RV envenomations were assayed for procalcitonin (n = 24) and serum CysC (n = 11).

RESULTS

The median peak IFABP for RV envenomations was much higher than healthy controls [3703.0 pg/mL (IQR 2250.1-13702.0 pg/mL) vs. 270.1 pg/mL (IQR 153.5-558.0 pg/mL) (p < 0.001)]. There was no difference in those with and without abdominal pain [3801.4 pg/mL (IQR 2080.5-22446.3 pg/mL) vs. 3696.6 pg/mL (IQR 2280.3-4664.7 pg/mL) (p = 1.0)]. Peak procalcitonin levels were elevated in envenomed patients 30.1 ng/ml (IQR: 13.1-59.7 ng/ml) with a level >2ng/mL indicative of severe sepsis] and also correlated with peak IFABP (r = 0.55, p = 0.006, n = 24). Peak serum CysC was also elevated and also correlated with IFABP (r = 0.71, p = 0.037, n = 9).

CONCLUSION

IFABP is significantly elevated indicating enterocyte damage occurs in RV envenomation. IFABP correlated with markers of sepsis (procalcitonin) and acute kidney injury (serum CysC) suggesting that enterocyte damage resulting in translocation of microbial associated molecular patterns (MAMPs) contributes to RV envenomation associated SIRS and sepsis.

Rapid development of a salivary calculus in submandibular gland and its potential causes in a young victim following Russell's viper bite

Russell's viper bites are known to cause a range of haemotoxic, neurotoxic, myotoxic, cytotoxic and nephrotoxic complications. However, the impact of Russell's viper bites as well as bites from other venomous snakes on sialolithiasis has not been previously reported. Here, we present an interesting case where a Russell's viper bite induced the rapid development of a calculus in submandibular gland in a 10-year-old boy. Upon admission, the victim did not show any symptoms of swelling and/or pain around his oral cavity. He received antivenom treatment to normalise his coagulation parameters, however, on day three he developed swelling and extreme pain around his right mandibular region. An ultrasound investigation revealed the presence of a calculus in his submandibular gland, which was removed using a minor surgical procedure. The histopathological examination revealed this as a poorly calcified salivary calculus, which is composed of cell debris, mucopolysaccharides and lipids. The mechanisms behind its rapid development following a snakebite are unclear although this could be linked to excessive inflammation or modifications to the composition of saliva induced by venom toxins or other unknown factors. This report reveals an unusual complication induced by a Russell's viper bite and alerts clinicians who treat snakebites to be aware of such envenomation effects. Moreover, this will lead to novel research to explore the relationship between venom toxins and functions of salivary glands.

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.

A Genus-Wide Bioactivity Analysis of Daboia (Viperinae: Viperidae) Viper Venoms Reveals Widespread Variation in Haemotoxic Properties

The snake genus Daboia (Viperidae: Viperinae; Oppel, 1811) contains five species: D. deserti, D. mauritanica, and D. palaestinae, found in Afro-Arabia, and the Russell's vipers D. russelii and D. siamensis, found in Asia. Russell's vipers are responsible for a major proportion of the medically important snakebites that occur in the regions they inhabit, and their venoms are notorious for their coagulopathic effects. While widely documented, the extent of venom variation within the Russell's vipers is poorly characterised, as is the venom activity of other species within the genus. In this study we investigated variation in the haemotoxic activity of Daboia using twelve venoms from all five species, including multiple variants of D. russelii, D. siamensis, and D. palaestinae. We tested the venoms on human plasma using thromboelastography, dose-response coagulometry analyses, and calibrated automated thrombography, and on human fibrinogen by thromboelastography and fibrinogen gels. We assessed activation of blood factors X and prothrombin by the venoms using fluorometry. Variation in venom activity was evident in all experiments. The Asian species D. russelii and D. siamensis and the African species D. mauritanica possessed procoagulant venom, while D. deserti and D. palaestinae were net-anticoagulant. Of the Russell's vipers, the venom of D. siamensis from Myanmar was most toxic and D. russelli of Sri Lanka the least. Activation of both factor X and prothrombin was evident by all venoms, though at differential levels. Fibrinogenolytic activity varied extensively throughout the genus and followed no phylogenetic trends. This venom variability underpins one of the many challenges facing treatment of Daboia snakebite envenoming. Comprehensive analyses of available antivenoms in neutralising these variable venom activities are therefore of utmost importance.

Capillary leak syndrome induced by the venoms of Russell's Vipers (Daboia russelii and Daboia siamensis) from eight locales and neutralization of the differential toxicity by three snake antivenoms

Snakebite envenomation caused by the Western and Eastern Russell's Vipers (Daboia russelii and Daboia siamensis) may potentially induce capillary leak syndrome (CLS), while the use of antivenom in treating this has not been well examined. This study investigated the CLS-inducing toxicity of Russell's Viper venoms from various sources and examined the neutralization activity of regionally available antivenoms, using a newly devised mouse model. D. russelii venoms demonstrated a more consistent vascular leakage activity (76,000-86,000 CLS unit of vascular leak index, a function of the diameter and intensity of Evans Blue dye extravasation into dermis) than D. siamensis venoms (33,000-88,000 CLS unit). Both species venoms increased hematocrits markedly (53-67%), indicating hemoconcentration. Regional antivenoms (DsMAV-Thailand, DsMAV-Taiwan, VPAV-India) preincubated with the venoms effectively neutralized the CLS effect to different extents. When the antivenoms were administered intravenously post-envenomation (challenge-rescue model), the neutralization was less effective, implying that CLS has a rapid onset that preceded the neutralizing activity of antivenom, and/or the antivenom has limited biodistribution to the venom's inoculation site. In conclusion, Russell's Viper venoms of both species from various locales induced CLS in mice. Antivenoms generally had limited efficacy in neutralizing the CLS effect. Innovative treatment for venom-induced CLS is needed.

Viper venoms drive the macrophages and hepatocytes to sequester and clear platelets: novel mechanism and therapeutic strategy for venom-induced thrombocytopenia

Venomous snakebites cause clinical manifestations that range from local to systemic and are considered a significant global health challenge. Persistent or refractory thrombocytopenia has been frequently reported in snakebite patients, especially in cases caused by viperidae snakes. Viper envenomation-induced thrombocytopenia may persist in the absence of significant consumption coagulopathy even after the antivenom treatment, yet the mechanism remains largely unknown. Our study aims to investigate the mechanism and discover novel therapeutic targets for coagulopathy-independent thrombocytopenia caused by viper envenomation. Here we found that patients bitten by Protobothrops mucrosquamatus and Trimeresurus stejnegeri, rather than Naja. atra may develop antivenom-resistant and coagulopathy-independent thrombocytopenia. Crude venoms and the derived C-type lectin-like proteins from these vipers significantly increased platelet surface expression of neuraminidase and platelet desialylation, therefore led to platelet ingestion by both macrophages and hepatocytes in vitro, and drastically decreased peripheral platelet counts in vivo. Our study is the first to demonstrate that desialylation-mediated platelet clearance is a novel mechanism of viper envenomation-induced refractory thrombocytopenia and C-type lectin-like proteins derived from the viper venoms contribute to snake venom-induced thrombocytopenia. The results of this study suggest the inhibition of platelet desialylation as a novel therapeutic strategy against viper venom-induced refractory thrombocytopenia.

Hemodynamic Changes Provoked through Intravascular Injection of the Echis carinatus Venom in Rats

Echis carinatus (E. carinatus) is known for its hematological and nephrotoxic properties in the envenomed patients. Based on the limited data upon the cardiovascular changes associated with this dangerous venomous snake in Iran, the current study purposed to evaluate the venom-induced hemodynamic manifestations in rats. Venom (120 µg/kg) was administered intravenously within one minute through the left femoral vein, and the hemodynamic parameters were continuously recorded using a pressure transducer (MLT844, ADInstruments, Australia). The venom caused prominent hypotension leading to death a few minutes after a transient uprise in blood pressure. It also induced a decrease in heart and pulmonary rates, yet it had no arrhythmogenic properties. Additionally, pre-treatment with the pepsin-derived Iranian polyvalent antivenom (30 µl/Kg) completely neutralized the hemodynamic responses but had no effect when instilled two minutes after venom injection. Heparin (300 IU/kg) and epinephrine (1.5 µg/kg) prevented dramatic hypotension when used 10 minutes before venom instillation; however, atropine (1 mg/kg), dexamethasone (1 mg/kg), and ketorolac (10 mg/ml) had no effects. All treated rats were killed post-injection. Histologically, the lung was the most vulnerable organ with mononuclear infiltration, microcystic formation, and significant capillary congestion. Prominent renal pathological deterioration also occurred, including mesangial cell infiltration and diffuse bleeding, leading to acute tubular necrosis. Modest portal inflammation and vascular congestion were observed in the hepatic tissue of the envenomed rats. The crude venom of Iranian Echis carinatus caused hypotension leading to bradycardia, a decrease in pulmonary rate, and death without significant histological changes to the heart.

A Biochemical and Pharmacological Characterization of Phospholipase A2 and Metalloproteinase Fractions from Eastern Russell's Viper (Daboia siamensis) Venom: Two Major Components Associated with Acute Kidney Injury

Acute kidney injury (AKI) following Eastern Russell's viper (Daboia siamensis) envenoming is a significant symptom in systemically envenomed victims. A number of venom components have been identified as causing the nephrotoxicity which leads to AKI. However, the precise mechanism of nephrotoxicity caused by these toxins is still unclear. In the present study, we purified two proteins from D. siamensis venom, namely RvPLA2 and RvMP. Protein identification using LCMS/MS confirmed the identity of RvPLA2 to be snake venom phospholipase A2 (SVPLA2) from Thai D. siamensis venom, whereas RvMP exhibited the presence of a factor X activator with two subunits. In vitro and in vivo pharmacological studies demonstrated myotoxicity and histopathological changes of kidney, heart, and spleen. RvPLA2 (3-10 µg/mL) caused inhibition of direct twitches of the chick biventer cervicis muscle preparation. After administration of RvPLA2 or RvMP (300 µg/kg, i.p.) for 24 h, diffuse glomerular congestion and tubular injury with minor loss of brush border were detected in envenomed mice. RvPLA2 and RvMP (300 µg/kg; i.p.) also induced congestion and tissue inflammation of heart muscle as well as diffuse congestion of mouse spleen. This study showed the significant roles of PLA2 and SVMP in snake bite envenoming caused by Thai D. siamensis and their similarities with observed clinical manifestations in envenomed victims. This study also indicated that there is a need to reevaluate the current treatment strategies for Thai D. siamensis envenoming, given the potential for irreversible nephrotoxicity.

Snake Venom Proteomics, Immunoreactivity and Toxicity Neutralization Studies for the Asiatic Mountain Pit Vipers, Ovophis convictus, Ovophis tonkinensis, and Hime Habu, Ovophis okinavensis

Snakebite envenomation is a serious neglected tropical disease, and its management is often complicated by the diversity of snake venoms. In Asia, pit vipers of the Ovophis species complex are medically important venomous snakes whose venom properties have not been investigated in depth. This study characterized the venom proteomes of Ovophis convictus (West Malaysia), Ovophis tonkinensis (northern Vietnam, southern China), and Ovophis okinavensis (Okinawa, Japan) by applying liquid chromatography-tandem mass spectrometry, which detected a high abundance of snake venom serine proteases (SVSP, constituting 40–60% of total venom proteins), followed by phospholipases A₂, snake venom metalloproteinases of mainly P-III class, L-amino acid oxidases, and toxins from other protein families which were less abundant. The venoms exhibited different procoagulant activities in human plasma, with potency decreasing from O. tonkinensis > O. okinavensis > O. convictus. The procoagulant nature of venom confirms that consumptive coagulopathy underlies the pathophysiology of Ovophis pit viper envenomation. The hetero-specific antivenoms Gloydius brevicaudus monovalent antivenom (GbMAV) and Trimeresurus albolabris monovalent antivenom (TaMAV) were immunoreactive toward the venoms, and cross-neutralized their procoagulant activities, albeit at variably limited efficacy. In the absence of species-specific antivenom, these hetero-specific antivenoms may be useful in treating coagulotoxic envenomation caused by the different snakes in their respective regions.

Acute Exposure to European Viper Bite in Children: Advocating for a Pediatric Approach

Viper bite is an uncommon but serious cause of envenoming in Europe, especially in children. Our study aim is to better describe and analyze the clinical course and treatment of viper bite envenoming in a pediatric population. We retrospectively reviewed 24 cases of pediatric viper bites that were admitted to the Pediatric Emergency Department and the Pediatric Intensive Care Unit of the Bambino Gesù Children Hospital in Rome between 2000 and 2020. Epidemiological characteristics of the children, localization of the bite, clinical and laboratory findings, and treatment approaches were evaluated. The median age of the patients was 4.2 years, with male predominance. Most cases of viper bite occurred in the late summer. Most patients required admission to the ward for prolonged observation. The most common presenting signs were pain, local oedema, and swelling. Patients with a high severity score also had a significantly higher white blood cell count and an increase of INR, LDH, and CRP levels. No fatality was reported. Viper bite envenomation is a rare pediatric medical emergency in Italy but may sometimes be severe. A new pediatric severity score may be implemented in the screening of children with viper bites to favor a selective and prompt administration of antivenom.

A Comprehensive Study Monitoring the Venom Composition and the Effects of the Venom of the Rare Ethiopian Endemic Snake Species Bitis parviocula

The Ethiopian endemic snake of the species Bitis parviocula, recognized for its colorful patterns, might be more interesting as we look deeper into the venom activity. We assayed the effects of venoms from the most widespread venomous African Bitis arietens and closely related species Bitis parviocula using The Hen’s Egg Test—Chorioallantoic membrane test (HET-CAM) and Chicken embryotoxicity screening test (CHEST), acetylcholinesterase (AChE) analysis, cytotoxicity assay performed on cell lines and protein analysis of selected venoms. Our results indicated that B. parviocula venom contains vasoactive compounds that have a direct effect on blood vessels. The AChE analysis showed significant ability inhibiting AChE activity in embryonic tissue. Cytotoxicity observed on A549 ATCC^® CCL-185™ cells indicates the possible presence of cytotoxic agents in B. parviocula venom. We proved previously described differences in the composition of venom obtained from B. arietans and B. parviocula by using electrophoresis and total protein concentration. Based on similarities in vasoactive effects observed after administration of venoms onto a chicken chorioallantoic membrane, we suggest that venom from B. arietans and B. parviocula might share certain venom proteins responsible for haemotoxicity. The main active components of B. parviocula venom are unknown. Our results suggest that it might be worth performing proteomic analysis of B. parviocula venom as it might contain medically valuable compounds.

Echis carinatus snake venom metalloprotease-induced toxicities in mice: Therapeutic intervention by a repurposed drug, Tetraethyl thiuram disulfide (Disulfiram)

Echis carinatus (EC) is known as saw-scaled viper and it is endemic to the Indian subcontinent. Envenoming by EC represents a major cause of snakebite mortality and morbidity in the Indian subcontinent. Zinc (Zn++) dependent snake venom metalloproteases (SVMPs) present in Echis carinatus venom (ECV) is well known to cause systemic hemorrhage and coagulopathy in experimental animals. An earlier report has shown that ECV activates neutrophils and releases neutrophil extracellular traps (NETs) that blocks blood vessels leading to severe tissue necrosis. However, the direct involvement of SVMPs in the release of NETs is not clear. Here, we investigated the direct involvement of EC SVMPs in observed pathological symptoms in a preclinical setup using specific Zn++ metal chelator, Tetraethyl thiuram disulfide (TTD)/disulfiram. TTD potently antagonizes the activity of SVMPs-mediated ECM protein degradation in vitro and skin hemorrhage in mice. In addition, TTD protected mice from ECV-induced footpad tissue necrosis by reduced expression of citrullinated H3 (citH3) and myeloperoxidase (MPO) in footpad tissue. TTD also neutralized ECV-induced systemic hemorrhage and conferred protection against lethality in mice. Moreover, TTD inhibited ECV-induced NETosis in human neutrophils and decreased the expression of peptidyl arginine deiminase (PAD) 4, citH3, MPO, and p-ERK. Further, we demonstrated that ECV-induced NETosis and tissue necrosis are mediated via PAR-1-ERK axis. Overall, our results provide an insight into SVMPs-induced toxicities and the promising protective efficacy of TTD can be extrapolated to treat severe tissue necrosis complementing anti-snake venom (ASV).

Sensitivity and specificity of 20-minute whole blood clotting test, prothrombin time, activated partial thromboplastin time tests in diagnosis of defibrination following Malayan pit viper envenoming

Malayan pit vipers (Calloselasma rhodostoma) are major health hazard in Southern Thailand causing systemic bleeding by defibrination and thrombocytopenia. Twenty minute whole blood clotting test (20WBCT) is a useful and informative bedside test recommended by WHO for diagnosis of significant coagulopathy following snakebite envenoming since it to some extent predicts the need for anti-venom therapy. Prothrombin time (PT), international normalized ratio (INR) and activated partial thromboplastin time (APTT) are standard clotting assays that are widely used for diagnosis of coagulopathy. The purpose of this study is to compare 20WBCT with the standard clotting assays (PT, INR, APTT, fibrinogen) in management of Malayan pit viper bitten-patients. We studied 296 victims prospectively during a 3-year period. In total, 115 (38.9%) cases showed a positive 20WBCT (un-clot) suggesting systemic envenomation. Thrombocytopenia (platelet count less than 100,000/μL), prolonged PT, prolonged APTT, INR ≥ 1.2, and fibrinogen level <100 mg/dl were found in 12.2%, 47.6%, 18.9%, 34.8% and 40.9%, respectively. Significant predictors for thrombocytopenia by multivariate analysis included systemic bleeding (p < 0.001), higher INR (p < 0.001), 20WBCT showing unclotted blood (p = 0.049), and longer bite-to-hospital time (p = 0.031). When a fibrinogen level below 100 mg/dl was determined as hypofibrinogenemic condition, INR had the highest area under ROC curve followed by 20WBCT and APTT, respectively, to identify such as hypofibrinogenemic condition. The diagnostic accuracy of 20WBCT and INR at or more than 1.155 were better than APTT at any cut-off points. INR >1.155 had a sensitivity of 78.5% and specificity of 90.3% while 20WBCT had sensitivity of 81.0% and specificity of 90.3%. CONCLUSIONS: Both 20WBCT and INR are useful to assess coagulation abnormality in Malayan pit viper-bitten patients.

Myotoxicity induced by Cerastes cerastes venom: Beneficial effect of heparin in skeletal muscle tissue regeneration

Myonecrosis is a relevant tissue damage induced by snakes of Viperidae family often leading to permanent tissue and function loss and even amputation. The aim of this study was to evaluate the effect of heparin on skeletal muscle tissue regeneration after Cerastes cerastes envenomation. Mice received either the venom (1 LD₅₀) by i.m. route, or the venom followed, by heparin administration by i.v. route at 15 min and 4 h. Obtained results showed that Cerastes cerastes venom induced deep tissue structure alterations, characterized mainly by edema, hemorrhage, myonecrosis and inflammation. Myotoxicity was correlated with increased CK levels in sera, concomitant with their decrease in muscle tissue homogenates. Muscle wet weight was restored within 2 weeks after heparin treatment and 28 days in the envenomed group. Heparin treatment significantly decreased MPO activity, suggesting an anti-inflammatory effect. NO, HGF, VEGF and G-CSF levels were increased after heparin administration. These mitogenic factors constitute potent stimuli for satellite and endothelial cells improving, thus, muscle regeneration. This study showed that muscle tissue recovery was significantly enhanced after heparin treatment. Heparin use seems to be a promising therapeutic approach after viper envenomation.

Secretory PLA2 specific single domain antibody neutralizes Russell viper venom induced cellular and organismal toxicity

Despite continued destruction of human lives by snakebites, appreciable improvements in immunotherapies have not been made. We selected and characterized venom-specific single domain antibodies (sdAbs) from a constructed phage display library of camelid variable region of heavy chain of the heavy chain antibodies (VHHs). Secretory phospholipase A2-specific sdAbs neutralized venom-induced toxicity in vitro and in vivo. Such monoclonal sdAbs could serve as an alternative to help manage snakebites to save lives.

Evaluation of the geographical utility of Eastern Russell's viper (Daboia siamensis) antivenom from Thailand and an assessment of its protective effects against venom-induced nephrotoxicity

BACKGROUND

Daboia siamensis (Eastern Russell's viper) is a medically important snake species found widely distributed across Southeast Asia. Envenomings by this species can result in systemic coagulopathy, local tissue injury and/or renal failure. While administration of specific antivenom is an effective treatment for Russell's viper envenomings, the availability of, and access to, geographically-appropriate antivenom remains problematic in many rural areas. In this study, we determined the binding and neutralizing capability of antivenoms manufactured by the Thai Red Cross in Thailand against D. siamensis venoms from four geographical locales: Myanmar, Taiwan, China and Thailand.

METHODOLOGY/PRINCIPLE FINDINGS

The D. siamensis monovalent antivenom displayed extensive recognition and binding to proteins found in D. siamensis venom, irrespective of the geographical origin of those venoms. Similar immunological characteristics were observed with the Hemato Polyvalent antivenom, which also uses D. siamensis venom as an immunogen, but binding levels were dramatically reduced when using comparator monovalent antivenoms manufactured against different snake species. A similar pattern was observed when investigating neutralization of coagulopathy, with the procoagulant action of all four geographical venom variants neutralized by both the D. siamensis monovalent and the Hemato Polyvalent antivenoms, while the comparator monovalent antivenoms were ineffective. These in vitro findings translated into therapeutic efficacy in vivo, as the D. siamensis monovalent antivenom was found to effectively protect against the lethal effects of all four geographical venom variants preclinically. Assessments of in vivo nephrotoxicity revealed that D. siamensis venom (700 μg/kg) significantly increased plasma creatinine and blood urea nitrogen levels in anaesthetised rats. The intravenous administration of D. siamensis monovalent antivenom at three times higher than the recommended scaled therapeutic dose, prior to and 1 h after the injection of venom, resulted in reduced levels of markers of nephrotoxicity and prevented renal morphological changes, although lower doses had no therapeutic effect.

CONCLUSIONS/SIGNIFICANCE

This study highlights the potential broad geographical utility of the Thai D. siamensis monovalent antivenom for treating envenomings by the Eastern Russell's viper. However, only the early delivery of high antivenom doses appears to be capable of preventing venom-induced nephrotoxicity.

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

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

Evaluation of different Pakistani medicinal plants for inhibitory potential against Echis carinatus induced Phospholipase A2 toxicity

Medicinal plants of Pakistan are known for their curative properties against snake bite as rural people have been using natural herbs for such injuries for hundreds to thousands of years. People of rural areas of Pakistan are prone to snakebite, and on the whole death due to snakebite has been increasing worldwide. The objective of this study was to test the neutralizing potential of 17 Pakistani medicinal plant extracts against phospholipase A2 activity in Echis carinatus venom. Plant material was extracted by simple maceration and fractionation of active plant extracts. Venom was collected by manual massage of the venom glands. The PLA2 enzymatic assay was performed to map out the venomous activity of Echis carinatus envenomation. Snake venom released fatty acids at different concentrations (0.1-5 mg/ml) of venom in a dose-dependent manner. Reduction of pH by 01 correlated with 133 μmol of fatty acids released at 5mg/ml of venom. All plants extract inhibited PLA2 activity, however, Curcuma longa, Citrullus colocynthis and Rubia cordifolia inhibited maximum of PLA2 activity (⁓78%) comparable to the standard antidote (p>0.5). Medicinal plants possess secondary metabolites and many active compounds that may have neutralizing or inhibiting properties against the PLA2 activity of Echis venom. Further studies such as compound analysis could provide an alternative against snakebites injuries resulting from Echis carinatus venom.

Investigating the cytotoxic effects of the venom proteome of two species of the Viperidae family (Cerastes cerastes and Cryptelytrops purpureomaculatus) from various habitats

Animal secretions are of great interest in terms of drug development due to their complex protein and peptide composition. Especially, in the field of therapeutic medications such as anti-cancer drugs snake venoms receive attention. In this study, we address two Viperidae species from various habitats with a particular focus on the cytotoxic potential along with the decomplexation of the venom proteome: the horned desert viper (Cerastes cerastes), native to desert regions of North Africa and the mangrove pit viper (Cryptelytrops purpureomaculatus), found in coastal forests of Southeast Asia. Initial cytotoxic screenings of the crude venoms revealed diverse activity, with the highest effect against SHSY5Y human glioblastoma carcinoma cells compared to other cancerous and non-cancerous cell lines. In-depth cytotoxicity studies of SHSY5Y cells with purified venom fractions revealed heterodimeric disintegrins from C. cerastes venom, which exerted a high cytotoxic activity with IC₅₀ values from 0.11 to 0.58 μM and a disintegrin-like effect on SHSY5Y morphology was observed due to cell detachment. Furthermore, two polyproline BPP-related peptides, one PLA₂ and a peptide-rich fraction were determined for C. purpureomaculatus with moderate IC₅₀ values between 3 and 51 μM. Additionally, the decryption of the venom proteomes by snake venomic mass spectrometry and comparison of the same species from different habitats revealed slight differences in the composition.

Preclinical Assessment of a New Polyvalent Antivenom (Inoserp Europe) against Several Species of the Subfamily Viperinae

The European continent is inhabited by medically important venomous Viperinae snakes. Vipera ammodytes, Vipera berus, and Vipera aspis cause the greatest public health problems in Europe, but there are other equally significant snakes in specific regions of the continent. Immunotherapy is indicated for patients with systemic envenoming, of which there are approximately 4000 annual cases in Europe, and was suggested as an indication for young children and pregnant women, even if they do not have systemic symptoms. In the present study, the safety and venom-neutralizing efficacy of Inoserp Europe-a new F(ab')₂ polyvalent antivenom, designed to treat envenoming by snakes in the Eurasian region-were evaluated. In accordance with World Health Organization recommendations, several quality control parameters were applied to evaluate the safety of this antivenom. The venom-neutralizing efficacy of the antivenom was evaluated in mice and the results showed it had appropriate neutralizing potency against the venoms of several species of Vipera, Montivipera, and Macrovipera. Paraspecificity of the antivenom was demonstrated as well, since it neutralized venoms of species not included in the immunization schemes and contains satisfactory levels of total proteins and F(ab')₂ fragment concentration. Therefore, this new polyvalent antivenom could be effective in the treatment of snake envenoming in Europe, including Western Russia and Turkey.

Delayed hypopituitarism following Russell's viper envenomation: a case series and literature review

PURPOSE

Hypopituitarism (HP) is an uncommon consequence of Russell's viper envenomation (RVE). Delayed hypopituitarism (DHP) presents months to years after recovering from snake bites (SB). The clinical presentation, manifestations, and outcomes of DHP following RVE have not been systematically studied. Here, we present a case series of HP following RVE with delayed diagnosis and conduct a literature review.

METHODS

We retrospectively reviewed data of eight DHP cases and literature to outline the presentation, manifestations, hormonal profiles, and radiological features of DHP following RVE.

RESULTS

Three men and five women, with a mean age at diagnosis of 39.5 ± 11.6 years, were included. The mean duration between snake bite (SB) and HP diagnosis was 8.1 ± 3.6 years. Secondary hypothyroidism and hypogonadotropic hypogonadism were present in all patients. Growth hormone deficiency (GHD) and secondary hypocortisolism were present in 6 (75%) patients. Magnetic resonance imaging (MRI) revealed empty sella and partially empty sella in three patients each (75%). The literature review revealed additional 20 DHP cases (mean age at diagnosis 32.4 ± 10.8 years), with 65% of patients being men. Fatigue, reduced libido, and loss of weight were the commonest symptoms among men. Secondary amenorrhea, fatigue, and loss of appetite were common manifestations among women. Acute kidney injury, GHD, secondary hypothyroidism, hypogonadism, and adrenal insufficiency were reported in 75%, 79%, 95%, 100%, and 85% of patients, respectively.

CONCLUSIONS

DHP is an important complication of RVE, and a delay in its diagnosis is associated with significant morbidity. Patients with RVE should be followed up for a long term to identify DHP.

An unusual case of gross myoglobinuria in a child following Russell's viper (Daboia russelii) envenomation

Overt myoglobinuria associated with myotoxicity is a classic feature of sea snake envenomation. Russell's viper bites usually result in coagulopathy, neurotoxicity and nephrotoxicity but rarely myotoxicity has been reported, especially in the Sri Lankan variety (Daboia russelii). All those studies have demonstrated mild degree myotoxicity with microscopic level myoglobinuria. We report what is probably the first case of gross myoglobinuria in a child following a Russell's viper bite with biochemical evidence of significant myotoxicity well beyond the levels that have been previously reported.

Is coagulopathy a common consequence of a Vipera berus bite? A retrospective single centre study

INTRODUCTION

The Vipera berus (common viper) is the only species of venomous snake found in Poland. The aim of this study was to determine to what extent coagulopathy has occurred as a post-bite complication.

MATERIAL AND METHODS

The medical records of 138 adult patients in the Sucha Beskidzka hospital with the diagnosis of snake bite between 2001-2014 were retrospectively analyzed. Demographic, clinical and laboratory data were collected. Antivenom was given to all patients, except one, with snake bites, but laboratory test were taken prior to administration of antivenom. Obtained results were compared to those of the control group, composed of 176 adults hospitalized in the same period for an elective laparoscopic cholecystectomy.

RESULTS

The mean platelet count in the study group was 239.94×109/L (SD=56.56) and 248.77×109/L (SD=57.82) in the control group. In 98% of the study group and 100% of the control group the platelet value (PLT) fell within laboratory norms (130 to 420×109/L), 2 patients after snake bites had a PLT lower than normal, and thrombocytosis was not observed in either group. A reference range of 0.85-1.3 INR below normal was found in 2 patients in the study group and 15 from the control group, while values above the normal range were found in 8 patients (6.7%) from the snake bite group and no patients from the control group. In the study group, the INR ranged from 0.78-1.43 with a mean of 1.046 (SD=0.14), while in the control group the range was from 0.79-1.28, with a mean of 0.95 (SD=0.08). There was a significant difference in INR between the study and control groups (p<0.0001).

CONCLUSIONS

The bite from V. berus does not result in severe thrombocytopenia, with only a moderate increase in INR values observed in about 7% of patients.

Exploring circulatory shock and mortality in viper envenomation: a prospective observational study from India

BACKGROUND

Viper envenomation contributes to nearly 50% of snake-bite deaths in India, chiefly due to circulatory shock. The mechanisms leading to circulatory shock include bleeding, capillary leak syndrome (CLS) and myocardial depression. Pituitary-adrenal axis involvement in circulatory shock, though described, has not been fully elucidated.

AIM

To identify predictors of circulatory shock and mortality in viper envenomation and explore the role of pituitary-adrenal axis in circulatory shock.

DESIGN

Prospective hospital-based observational study.

METHODS

Once a syndromic diagnosis of viper envenomation was made, relevant clinical and laboratory data were collected. Serum cortisol was estimated in those with circulatory shock. Post-mortem examination of pituitary, kidneys and adrenals was performed. Adjusted odds-ratios were calculated for respective risk-factors for shock and mortality using multivariable logistic regression with backward elimination strategy.

RESULTS

Of 248 patients of viper envenomation treated at our hospital, circulatory shock was present in 19% and in-hospital mortality was 23%. CLS, circulatory shock, bleeding and requirement of > 20 vials of antivenom predicted mortality. Ischaemic and haemorrhagic necrosis of pituitary or adrenals was present in 51% of post-mortem specimens. Disseminated intravascular coagulation (DIC) and CLS were strong predictors of pituitary haemorrhage.

CONCLUSION

Predictors of mortality - bleeding, CLS and requirement of high antivenom doses are warning signs which can alert clinicians to patients who may have poor outcomes. Our study points to a definite role of pituitary-adrenal axis in circulatory shock supports the hypothesis that pituitary involvement in viper envenomation closely resembles Sheehan syndrome. The mechanism of pituitary involvement appears to be a result of increased susceptibility of the swollen gland secondary to CLS and micro thrombi deposition in DIC.

Systemic vascular leakage induced in mice by Russell's viper venom from Pakistan

Envenomings by some populations of the Russell's viper (Daboia russelii) are characterized by a systemic capillary leak syndrome (CLS) which causes hemoconcentration, and is associated with the severity of envenoming. We adapted a model of CLS in mice by assessing hemoconcentration. The venom of D. russelii from Pakistan, but not that of another viperid, Bothrops asper, induced hemoconcentration and an increment in vascular permeability, being devoid of hemorrhagic activity at the doses tested. These findings reveal a dichotomous pattern of vasculotoxicity in viperid snake venoms. This difference might depend on variations in venom composition, especially regarding metalloproteinases (SVMPs), which are low in Pakistani D. russelii and high in B. asper. Inhibition of SVMPs and phospholipases A2 in D. russelii venom did not abrogate hemoconcentration. An hemoconcentration-inducing fraction was obtained by chromatography, which contains vascular endothelial growth factor (VEGF), a known potent inducer of increment in vascular permeability. Exudates collected from tissue injected with venom also induced hemoconcentration, and the effect was inhibited by antivenom. However, the amount of venom in exudate required to induce the effect is low, as compared with venom dissolved in saline solution, hence suggesting that endogenous proteins present in the exudate, probably inflammatory mediators, potentiate the effect.

Determination of the sub-lethal nephrotoxic dose of Russell's viper (Daboia russelii) venom in Wistar rats

Wistar rats were administered increasing doses of Russell's viper venom (RVV; 0.025-0.4 mg/kg) intraperitoneally to investigate acute kidney injury (AKI) by measuring creatinine (1.5-fold increase in serum creatinine above baseline) and examining kidney histology. Approximately 50% of rats receiving 0.25-0.4 mg/kg venom died within 72 h. An increase in serum creatinine only occurred at a venom dose of 0.4 mg/kg, except in two rats. Acute tubular necrosis, glomerular necrosis, cortical necrosis and interstitial inflammation were observed at venom doses of ≥0.25 mg/kg in 12/36 rats. However, of those 12 rats only four survived to 48 h compared to the 24 rats not developing nephrotoxicity, in which 18 were alive at 48 h. There was poor correlation between histological nephrotoxicity and AKI based on creatinine measurement. The early death in rats with AKI makes this a poor model for studying RVV-induced AKI.

Does size matter? Venom proteomic and functional comparison between night adder species (Viperidae: Causus) with short and long venom glands

Night adders (Causus species within the Viperidae family) are amphibian specialists and a common source of snakebite in Africa. Some species are unique in that they have the longest venom glands of any viper, extending approximately 10% of the body length. Despite their potential medical importance and evolutionary novelty, their venom has received almost no research attention. In this study, venoms from a short-glanded species (C. lichtensteinii) and from a long-glanded species (C. rhombeatus) were compared using a series of proteomic and bioactivity testing techniques to investigate and compare the toxin composition and functioning of the venoms of these two species. Both C. rhombeatus and C. lichtensteinii were similar in overall venom composition and inhibition of blood coagulation through non-clotting proteolytic cleavage of fibrinogen. While the 1D gel profiles were very similar to each other in the toxin types present, 2D gel analyses revealed isoformic differences within each toxin classes. This variation was congruent with differential efficacy of South African Institute for Medical Research snake polyvalent antivenom, with C. lichtensteinii unaffected at the dose tested while C. rhombeatus was moderately but significantly neutralized. Despite the variation within toxin classes, the similarity in overall venom biochemistry suggests that the selection pressure for the evolution of long glands served to increase venom yield in order to subjugate proportionally large anurans as a unique form of niche partitioning, and is not linked to significant changes in venom function. These results not only contribute to the body of venom evolution knowledge but also highlight the limited clinical management outcomes for Causus envenomations.

Proteomic Analysis and Immuno-Profiling of Eastern India Russell's Viper ( Daboia russelii) Venom: Correlation between RVV Composition and Clinical Manifestations Post RV Bite

The proteomes of Russell's viper venom (RVV) from Burdwan (RVV B) and Nadia (RVV N), the two districts of West Bengal, eastern India (EI), were investigated by gel-filtration chromatography (GFC) followed by tandem mass spectrometry of tryptic fragments of the fractions. A total of 73 and 69 proteins belonging to 15 snake venom protein families were identified in RVV B and RVV N, respectively, by MS/MS search against Viperidae (taxid 8689) protein entries of the nonredundant NCBI database. The minor differences in venom composition of both the EI RV were established unequivocally by their biochemical and pharmacological properties and by SDS-PAGE, gel filtration chromatography, and LC-MS/MS analyses. The composition of EI RVVs was well correlated with published reports on the pathophysiology of RV-envenomed patients from this part of the country. Venom-antivenom cross-reactivity determined by ELISA, Western blotting, and antivenomics approaches demonstrated poor recognition of low molecular mass (<20 kDa) RVV proteins by commercial polyvalent antivenoms, which was substantiated by neutralization of RVV enzymes by antivenom.