Unity Makes Strength: Exploring Intraspecies and Interspecies Toxin Synergism between Phospholipases A2 and Cytotoxins

Specific Amino Acid Residues in the Three Loops of Snake Cytotoxins Determine Their Membrane Activity and Provide a Rationale for a New Classification of These Toxins

Cytotoxins (CTs) are three-finger membrane-active toxins present mainly in cobra venom. Our analysis of the available CT amino acid sequences, literature data on their membrane activity, and conformational equilibria in aqueous solution and detergent micelles allowed us to identify specific amino acid residues which interfere with CT incorporation into membranes. They include Pro9, Ser28, and Asn/Asp45 within the N-terminal, central, and C-terminal loops, respectively. There is a hierarchy in the effect of these residues on membrane activity: Pro9 > Ser28 > Asn/Asp45. Taking into account all the possible combinations of special residues, we propose to divide CTs into eight groups. Group 1 includes toxins containing all of the above residues. Their representatives demonstrated the lowest membrane activity. Group 8 combines CTs that lack these residues. For the toxins from this group, the greatest membrane activity was observed. We predict that when solely membrane activity determines the cytotoxic effects, the activity of CTs from a group with a higher number should exceed that of CTs from a group with a lower number. This classification is supported by the available data on the cytotoxicity and membranotropic properties of CTs. We hypothesize that the special amino acid residues within the loops of the CT molecule may indicate their involvement in the interaction with non-lipid targets.

Using organ-on-a-chip technology to study haemorrhagic activities of snake venoms on endothelial tubules

Snakebite envenomation is a major public health issue which causes severe morbidity and mortality, affecting millions of people annually. Of a diverse range of clinical manifestations, local and systemic haemorrhage are of particular relevance, as this may result in ischemia, organ failure and even cardiovascular shock. Thus far, in vitro studies have failed to recapitulate the haemorrhagic effects observed in vivo. Here, we present an organ-on-a-chip approach to investigate the effects of four different snake venoms on a perfused microfluidic blood vessel model. We assess the effect of the venoms of four snake species on epithelial barrier function, cell viability, and contraction/delamination. Our findings reveal two different mechanisms by which the microvasculature is being affected, either by disruption of the endothelial cell membrane or by delamination of the endothelial cell monolayer from its matrix. The use of our blood vessel model may shed light on the key mechanisms by which tissue-damaging venoms exert their effects on the capillary vessels, which could be helpful for the development of effective treatments against snakebites.

Development of a membrane-disruption assay using phospholipid vesicles as a proxy for the detection of cellular membrane degradation

Snakebite envenoming is a global health issue that affects millions of people worldwide, and that causes morbidity rates surpassing 450,000 individuals annually. Patients suffering from snakebite morbidities may experience permanent disabilities such as pain, blindness and amputations. The (local) tissue damage that causes these life-long morbidities is the result of cell- and tissue-damaging toxins present in the venoms. These compounds belong to a variety of toxin classes and may affect cells in various ways, for example, by affecting the cell membrane. In this study, we have developed a high-throughput in vitro assay that can be used to study membrane disruption caused by snake venoms using phospholipid vesicles from egg yolk as a substrate. Resuspended chicken egg yolk was used to form these vesicles, which were fluorescently stained to allow monitoring of the degradation of egg yolk vesicles on a plate reader. The assay proved to be suitable for studying phospholipid vesicle degradation of crude venoms and was also tested for its applicability for neutralisation studies of varespladib, which is a PLA2 inhibitor. We additionally made an effort to identify the responsible toxins using liquid chromatography, followed by post-column bioassaying and protein identification using high-throughput venomics. We successfully identified various toxins in the venoms of C. rhodostoma and N. mossambica, which are likely to be involved in the observed vesicle-degrading effect. This indicates that the assay can be used for screening the membrane degrading activity of both crude and fractionated venoms as well as for neutralisation studies.

De novo designed proteins neutralize lethal snake venom toxins

Snakebite envenoming remains a devastating and neglected tropical disease, claiming over 100,000 lives annually and causing severe complications and long-lasting disabilities for many more1,2. Three-finger toxins (3FTx) are highly toxic components of elapid snake venoms that can cause diverse pathologies, including severe tissue damage3 and inhibition of nicotinic acetylcholine receptors (nAChRs) resulting in life-threatening neurotoxicity4. Currently, the only available treatments for snakebite consist of polyclonal antibodies derived from the plasma of immunized animals, which have high cost and limited efficacy against 3FTxs5,6,7. Here, we use deep learning methods to de novo design proteins to bind short- and long-chain α-neurotoxins and cytotoxins from the 3FTx family. With limited experimental screening, we obtain protein designs with remarkable thermal stability, high binding affinity, and near-atomic level agreement with the computational models. The designed proteins effectively neutralize all three 3FTx sub-families in vitro and protect mice from a lethal neurotoxin challenge. Such potent, stable, and readily manufacturable toxin-neutralizing proteins could provide the basis for safer, cost-effective, and widely accessible next-generation antivenom therapeutics. Beyond snakebite, our computational design methodology should help democratize therapeutic discovery, particularly in resource-limited settings, by substantially reducing costs and resource requirements for development of therapies to neglected tropical diseases.

Tissue damaging toxins in snake venoms: mechanisms of action, pathophysiology and treatment strategies

Snakebite envenoming is an important public health issue responsible for mortality and severe morbidity. Where mortality is mainly caused by venom toxins that induce cardiovascular disturbances, neurotoxicity, and acute kidney injury, morbidity is caused by toxins that directly or indirectly destroy cells and degrade the extracellular matrix. These are referred to as 'tissue-damaging toxins' and have previously been classified in various ways, most of which are based on the tissues being affected (e.g., cardiotoxins, myotoxins). This categorisation, however, is primarily phenomenological and not mechanistic. In this review, we propose an alternative way of classifying cytotoxins based on their mechanistic effects rather than using a description that is organ- or tissue-based. The mechanisms of toxin-induced tissue damage and their clinical implications are discussed. This review contributes to our understanding of fundamental biological processes associated with snakebite envenoming, which may pave the way for a knowledge-based search for novel therapeutic options.

Repurposed drugs and their combinations prevent morbidity-inducing dermonecrosis caused by diverse cytotoxic snake venoms

Morbidity from snakebite envenoming affects approximately 400,000 people annually. Tissue damage at the bite-site often leaves victims with catastrophic life-long injuries and is largely untreatable by current antivenoms. Repurposed small molecule drugs that inhibit specific snake venom toxins show considerable promise for tackling this neglected tropical disease. Using human skin cell assays as an initial model for snakebite-induced dermonecrosis, we show that the drugs 2,3-dimercapto-1-propanesulfonic acid (DMPS), marimastat, and varespladib, alone or in combination, inhibit the cytotoxicity of a broad range of medically important snake venoms. Thereafter, using preclinical mouse models of dermonecrosis, we demonstrate that the dual therapeutic combinations of DMPS or marimastat with varespladib significantly inhibit the dermonecrotic activity of geographically distinct and medically important snake venoms, even when the drug combinations are delivered one hour after envenoming. These findings strongly support the future translation of repurposed drug combinations as broad-spectrum therapeutics for preventing morbidity caused by snakebite.

Pulmonary involvement from animal toxins: the cellular mechanisms

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

Application of honeybee venom loaded nanoparticles for the treatment of chronic toxoplasmosis: parasitological, histopathological, and immunohistochemical studies

Toxoplasma gondii is an opportunistic intracellular protozoon which may cause severe disease in the immunocompromised patients. Unfortunately, the majority of treatments on the market work against tachyzoites in the acute infection but can't affect tissue cysts in the chronic phase. So, this study aimed to evaluate the effect of bee venom (BV) loaded metal organic frameworks (MOFs) nanoparticles (NPs) for the treatment of chronic murine toxoplasmosis. Ninety laboratory Swiss Albino mice were divided into 9 groups (10 mice each); GI (negative control), GII (infected control), GIII-GXI (infected with Me49 strain of Toxoplasma and treated); GIII (MOFs-NPs), GIV and GV (BV alone and loaded on MOFs-NPs), GVI and GVII (spiramycin alone and loaded on MOFs-NPs), GVIII and GIX (ciprofloxacin alone and loaded on MOFs-NPs). Parasitological examination of brain cyst count, histopathological study of brain, retina, liver, and kidney tissue sections and immunohistochemical (IHC) evaluation of liver was performed. Counting of Toxoplasma brain cysts showed high statistically significant difference between the infected treated groups and GII. GV showed the least count of brain cysts; mean ± SD (281 ± 29.5). Histopathological examination revealed a marked ameliorative effect of BV administration when used alone or loaded MOFs-NPs. It significantly reduced tissue inflammation, degeneration, and fibrosis. IHC examination of liver sections revealed high density CD8+ infiltration in GII, low density CD8+ infiltration in GIII, GVI, GVII, GVIII, and GIX while GIV and GV showed intermediate density CD8+ infiltration. BV is a promising Apitherapy against chronic toxoplasmosis. This effect is markedly enhanced by MOFs-NPs.

Graphical abstract

Development of a high-throughput in vitro screening method for the assessment of cell-damaging activities of snake venoms

Snakebite envenoming is a globally important public health issue that has devastating consequences on human health and well-being, with annual mortality rates between 81,000 and 138,000. Snake venoms may cause different pathological effects by altering normal physiological processes such as nervous transfer and blood coagulation. In addition, snake venoms can cause severe (local) tissue damage that may result in life-long morbidities, with current estimates pointing towards an additional 450,000 individuals that suffer from permanent disabilities such as amputations, contractions and blindness. Despite such high morbidity rates, research to date has been mainly focusing on neurotoxic and haemotoxic effects of snake venoms and considerably less on venom-induced tissue damage. The molecular mechanisms underlaying this pathology include membrane disruption and extracellular matrix degradation. This research describes methods used to study the (molecular) mechanisms underlaying venom-induced cell- and tissue damage. A selection of cellular bioassays and fluorescent microscopy were used to study cell-damaging activities of snake venoms in multi-well plates, using both crude and fractionated venoms. A panel of 10 representative medically relevant snake species was used, which cover a large part of the geographical regions most heavily affected by snakebite. The study comprises both morphological data as well as quantitative data on cell metabolism and viability, which were measured over time. Based on this data, a distinction could be made in the ways by which viper and elapid venoms exert their effects on cells. We further made an effort to characterise the bioactive compounds causing these effects, using a combination of liquid chromatography methods followed by bioassaying and protein identification using proteomics. The outcomes of this study might prove valuable for better understanding venom-induced cell- and tissue-damaging pathologies and could be used in the process of developing and improving snakebite treatments.

A Fast Method for Detection of Fake Venoms and Investigation of Interspecies Variation Using Venoms of Androctonus, Buthus, and Leiurus (Scorpiones: Buthidae) Species

Background

Within the scorpion family Buthidae, some of the most dangerous venomous genera are Androctonus (A), Buthus (B), and Leiurus (L). This venom is valuable raw material for numerous therapeutic formulations because of its pharmacological potential; however, because of its high prices in the global market, fake "venom mixes" are being made to market illegally, and it is important that these unknown mixes be evaluated. A fast and accurate response to the request for this identification is necessary.

Method

This study was conducted in Turkey in 2022. Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) is a linear positive-ionization mode was used for identification of scorpion species. The mass spectra of the three scorpion venoms were examined in detail. The peptide and protein profiles in the venoms of congenerous three scorpion venoms and the proportional differences in these venoms were investigated. For interspecific variation, a principal component analysis of all venoms was conducted, and variance values and distance-proximity indices were determined.

Results

The top three peptide masses in the highest relative abundance for A. australis, B. mardochei, and L. quinquestriatus quinquestriatus, respectively, were 6901, 7431, and 7447; 4238, 5283, and 4055; and 3828, 7868, and 6799 Da. While the variance rate between A. australis and the other two venoms was 40%, this rate was 38% between B. mordochei and L. quinquestriatus quinquestriatus venoms.

Conclusion

A very simple protocol of species identification using scorpion venom samples was created using recent advances in MALDI-TOF MS.

The concept of Big Four: Road map from snakebite epidemiology to antivenom efficacy

Snake envenomation is a life-threatening disease caused by the injection of venom toxins from the venomous snake bite. Snakebite is often defined as the occupational or domestic hazard mostly affecting the rural population. India experiences a high number of envenoming cases and fatality due to the nation's diversity in inhabiting venomous snakes. The Indian Big Four snakes namely Russell's viper (Daboia russelii), spectacled cobra (Naja naja), common krait (Bungarus caeruleus), and saw-scaled viper (Echis carinatus) are responsible for majority of the snake envenoming cases and death. The demographic characteristics including occupation, stringent snake habitat management, poor healthcare facilities and ignorance of the rural victims are the primary influencers of high mortality. Biogeographic venom variation greatly influences the clinical pathologies of snake envenomation. The current antivenoms against the Big Four snakes are found to be less immunogenic against the venom toxins emphasizing the necessity of alternative approaches for antivenom generation. This review summarizes the burden of snake envenomation in India by the Big Four snakes including the geographic distribution of snake species and biogeographic venom variation. We have provided comprehensive information on snake venom proteomics that has aided the better understanding of venom induced pathological features, summarized the impact of current polyvalent antivenom therapy highlighting the need for potential antivenom treatment for the effective management of snakebites.

Harnessing the Power of Venomous Animal-Derived Toxins against COVID-19

Animal-derived venoms are complex mixtures of toxins triggering important biological effects during envenomings. Although venom-derived toxins are known for their potential of causing harm to victims, toxins can also act as pharmacological agents. During the COVID-19 pandemic, there was observed an increase in in-depth studies on antiviral agents, and since, to date, there has been no completely effective drug against the global disease. This review explores the crosstalk of animal toxins and COVID-19, aiming to map potential therapeutic agents derived from venoms (e.g., bees, snakes, scorpions, etc.) targeting COVID-19.

The secretory phenotypes of envenomed cells: Insights into venom cytotoxicity

Snake envenomation is listed as Category A Neglected Tropical Diseases (NTD) by World Health Organization, indicates a severe public health problem. The global figures for envenomation cases are estimated to be more than 1.8 million annually. Even if the affected victims survive the envenomation, they might suffer from permanent morbidity due to local envenomation. One of the most prominent local envenomation is dermonecrosis. Dermonecrosis is a pathophysiological outcome of envenomation that often causes disability in the victims due to surgical amputations, deformities, contracture, and chronic ulceration. The key venom toxins associated with this local symptom are mainly attributed to substantial levels of enzymatic and non-enzymatic toxins as well as their possible synergistic actions. Despite so, the severity of the local tissue damage is based on macroscopic observation of the bite areas. Furthermore, limited knowledge is known about the key biomarkers involved in the pathogenesis of dermonecrosis. The current immunotherapy with antivenom is also ineffective against dermonecrosis. These local effects eventually end up as sequelae. There is also a global shortage of toxins-targeted therapeutics attributed to inadequate knowledge of the actual molecular mechanisms of cytotoxicity. This chapter discusses the characterization of secretory phenotypes of dermonecrosis as an advanced tool to indicate its severity and pathogenesis in envenomation. Altogether, the secretory phenotypes of envenomed cells and tissues represent the precise characteristics of dermonecrosis caused by venom toxins.

High-throughput proteomics and in vitro functional characterization of the 26 medically most important elapids and vipers from sub-Saharan Africa

Venomous snakes are important parts of the ecosystem, and their behavior and evolution have been shaped by their surrounding environments over the eons. This is reflected in their venoms, which are typically highly adapted for their biological niche, including their diet and defense mechanisms for deterring predators. Sub-Saharan Africa is rich in venomous snake species, of which many are dangerous to humans due to the high toxicity of their venoms and their ability to effectively deliver large amounts of venom into their victims via their bite. In this study, the venoms of 26 of sub-Saharan Africa's medically most relevant elapid and viper species were subjected to parallelized toxicovenomics analysis. The analysis included venom proteomics and in vitro functional characterization of whole venom toxicities, enabling a robust comparison of venom profiles between species. The data presented here corroborate previous studies and provide biochemical details for the clinical manifestations observed in envenomings by the 26 snake species. Moreover, two new venom proteomes (Naja anchietae and Echis leucogaster) are presented here for the first time. Combined, the presented data can help shine light on snake venom evolutionary trends and possibly be used to further improve or develop novel antivenoms.

Current Insights in the Mechanisms of Cobra Venom Cytotoxins and Their Complexes in Inducing Toxicity: Implications in Antivenom Therapy

Cytotoxins (CTXs), an essential class of the non-enzymatic three-finger toxin family, are ubiquitously present in cobra venoms. These low-molecular-mass toxins, contributing to about 40 to 60% of the cobra venom proteome, play a significant role in cobra venom-induced toxicity, more prominently in dermonecrosis. Structurally, CTXs contain the conserved three-finger hydrophobic loops; however, they also exhibit a certain degree of structural diversity that dictates their biological activities. In their mechanism, CTXs mediate toxicity by affecting cell membrane structures and membrane-bound proteins and activating apoptotic and necrotic cell death pathways. Notably, some CTXs are also responsible for depolarizing neurons and heart muscle membranes, thereby contributing to the cardiac failure frequently observed in cobra-envenomed victims. Consequently, they are also known as cardiotoxins (CdTx). Studies have shown that cobra venom CTXs form cognate complexes with other components that potentiate the toxic effects of the venom's individual component. This review focuses on the pharmacological mechanism of cobra venom CTXs and their complexes, highlighting their significance in cobra venom-induced pathophysiology and toxicity. Furthermore, the potency of commercial antivenoms in reversing the adverse effects of cobra venom CTXs and their complexes in envenomed victims has also been discussed.

Bee Venom Induces Acute Inflammation through a H2O2-Mediated System That Utilizes Superoxide Dismutase

Venoms from venomous arthropods, including bees, typically induce an immediate local inflammatory response; however, how venoms acutely elicit inflammatory response and which components induce an inflammatory response remain unknown. Moreover, the presence of superoxide dismutase (SOD3) in venom and its functional link to the acute inflammatory response has not been determined to date. Here, we confirmed that SOD3 in bee venom (bvSOD3) acts as an inducer of H₂O₂ production to promote acute inflammatory responses. In mouse models, exogenous bvSOD3 rapidly induced H₂O₂ overproduction through superoxides that are endogenously produced by melittin and phospholipase A₂, which then upregulated caspase-1 activation and proinflammatory molecule secretion and promoted an acute inflammatory response. We also showed that the relatively severe noxious effect of bvSOD3 elevated a type 2 immune response and bvSOD3 immunization protected against venom-induced inflammation. Our findings provide a novel view of the mechanism underlying bee venom-induced acute inflammation and offer a new approach to therapeutic treatments for bee envenoming and bee venom preparations for venom therapy/immunotherapy.

Functional Recognition Theory and Type 2 Immunity: Insights and Uncertainties

Type 2 immunity plays an important role in host defense against helminths and toxins while driving allergic diseases. Despite progress in understanding the biology of type 2 immunity, the fundamental mechanisms regulating the type 2 immune module remain unclear. In contrast with structural recognition used by pattern recognition receptors, type 2 immunogens are sensed through their functional properties. Functional recognition theory has arisen as the paradigm for the initiation of type 2 immunity. However, the vast array of structurally unrelated type 2 immunogens makes it challenging to advance our understanding of type 2 immunity. In this article, we review functional recognition theory and organize type 2 immunogens into distinct classes based on how they fit into the concept of functional recognition. Lastly, we discuss areas of uncertainty in functional recognition theory with the goal of providing a framework to further define the logic of type 2 immunity in host protection and immunopathology.

Melittin Tryptophan Substitution with a Fluorescent Amino Acid Reveals the Structural Basis of Selective Antitumor Effect and Subcellular Localization in Tumor Cells

Melittin is a membrane-active peptide with strong anticancer activity against various cancers. Despite decades of research, the role of the singular Trp in the anticancer activity and selectivity of melittin remains poorly understood. Here, we propose a theranostic solution based on the substitution of Trp19 with a noncanonical fluorescent amino acid (DapAMCA). The introduction of DapAMCA residue in melittin stabilized the helical structure of the peptide, as evaluated by circular dichroism spectra and molecular dynamics simulations. In vitro hemolytic and anticancer activity assays revealed that introducing DapAMCA residue in melittin changed its mode of action with the cell membrane, resulting in reduced hemolytic toxicity and an improved the selectivity index (SI), with up to a five-fold increase compared to melittin. In vitro fluorescence imaging of DapAMCA-labeled melittin (MELFL) in cancer cells demonstrated high membrane-penetrating activity, with strong nuclear and nucleolar localization ability. These findings provide implications for novel anticancer therapies based on Trp-substituted designs and nuclear/nucleolar targeted therapy.

The myth of cobra venom cytotoxin: More than just direct cytolytic actions

Cobra venom cytotoxin (CTX) is a non-enzymatic three-finger toxin that constitutes 40-60% of cobra venom. Thus, it plays an important role in the pathophysiology of cobra envenomation, especially in local dermonecrosis. The three-finger hydrophobic loops of CTX determine the cytotoxicity. Nevertheless, the actual mechanisms of cytotoxicity are not fully elucidated as they involve not only cytolytic actions but also intracellular signalling-mediated cell death pathways. Furthermore, the possible transition cell death pattern remains to be explored. The actual molecular mechanisms require further studies to unveil the relationship between different CTXs from different cobra species and cell types which may result in differential cell death patterns. Here, we discuss the biophysical interaction of CTX with the cell membrane involving four binding modes: electrostatic interaction, hydrophobic partitioning, isotropic phase, and oligomerisation. Oligomerisation of CTX causes pore formation in the membrane lipid bilayer. Additionally, the CTX-induced apoptotic pathway can be executed via death receptor-mediated extrinsic pathways and mitochondrial-mediated intrinsic pathways. We also discuss lysosomal-mediated necrosis and the occurrence of necroptosis following CTX action. Collectively, we provided an insight into concentration-dependent transition of cell death pattern which involves different mechanistic actions. This contributes a new direction for further investigation of cytotoxic pathways activated by the CTXs for future development of biotherapeutics targeting pathological effects caused by CTX.

Single-molecule phospholipase A2 becomes processive on melittin-induced membrane deformations

While it is established that the topology of lipid membranes plays an important role in biochemical processes, few direct observations exist regarding how the membranes are actively restructured and its consequences on subsequent reactions. In this work, we investigated how the two major components of bee venom, melittin and phospholipase A₂ (PLA₂), achieve activation by such membrane remodeling. Their membrane-disrupting functions have been reported to increase when both are present, but the mechanism of this synergism had not been established. Using membrane reconstitution, we found that melittin can form large-scale membrane deformities upon which PLA₂ activity is 25-fold higher. Tracking of single-molecule PLA₂ revealed that its processive behavior on these deformities underlies the enhanced activity. These results show how melittin and PLA₂ work synergistically to enhance the lytic effects of the bee venom. More broadly, they also demonstrate how the membrane topology may be actively altered to modulate cellular membrane-bound reactions.

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.

Terrestrial venomous animals, the envenomings they cause, and treatment perspectives in the Middle East and North Africa

The Middle East and Northern Africa, collectively known as the MENA region, are inhabited by a plethora of venomous animals that cause up to 420,000 bites and stings each year. To understand the resultant health burden and the key variables affecting it, this review describes the epidemiology of snake, scorpion, and spider envenomings primarily based on heterogenous hospital data in the MENA region and the pathologies associated with their venoms. In addition, we discuss the venom composition and the key medically relevant toxins of these venomous animals, and, finally, the antivenoms that are currently in use to counteract them. Unlike Asia and sub-Saharan Africa, scorpion stings are significantly more common (approximately 350,000 cases/year) than snakebites (approximately 70,000 cases/year) and present the most significant contributor to the overall health burden of envenomings, with spider bites being negligible. However, this review also indicates that there is a substantial lack of high-quality envenoming data available for the MENA region, rendering many of these estimates speculative. Our understanding of the venoms and the toxins they contain is also incomplete, but already presents clear trends. For instance, the majority of snake venoms contain snake venom metalloproteinases, while sodium channel-binding toxins and potassium channel-binding toxins are the scorpion toxins that cause most health-related challenges. There also currently exist a plethora of antivenoms, yet only few are clinically validated, and their high cost and limited availability present a substantial health challenge. Yet, some of the insights presented in this review might help direct future research and policy efforts toward the appropriate prioritization of efforts and aid the development of future therapeutic solutions, such as next-generation antivenoms.

Bee Venom: From Venom to Drug

Insects of the order Hymenoptera have a defensive substance that contains many biologically active compounds. Specifically, venom from honeybees (Apis mellifera) contains many enzymes and peptides that are effective against various diseases. Different research papers stated the possibility of using bee venom (a direct bee sting or in an injectable form) in treating several complications; either in vivo or in vitro. Other reports used the active fractions of bee venom clinically or at labratory scale. Many reports and publications have stated that bee venom and its constituents have multiple biological activities including anti-microbial, anti-protozoan, anti-cancer, anti-inflammatory, and anti-arthritic properties. The present review aims to refer to the use of bee venom itself or its fractions in treating several diseases and counteracting drug toxicities as an alternative protocol of therapy. The updated molecular mechanisms of actions of bee venom and its components are discussed in light of the previous updated publications. The review also summarizes the potential of venom loaded on nanoparticles as a drug delivery vehicle and its molecular mechanisms. Finally, the products of bee venom available in markets are also demonstrated.

Pentalinonsterol, a Phytosterol from Pentalinon andrieuxii, is Immunomodulatory through Phospholipase A2 in Macrophages toward its Antileishmanial Action

Our earlier in vitro and in vivo studies have revealed that the phytosterol, pentalinonsterol (cholest-4,20,24-trien-3-one) (PEN), isolated from the roots of Pentalinon andrieuxii, possesss immunomodulatory properties in macrophages and dendritic cells. Leishmaniasis, caused by the infection of Leishmania spp. (a protozoan parasite), is emerging as the second-leading cause of mortality among the tropical diseases and there is an unmet need for a pharmacological intervention of leishmaniasis. Given the beneficial immunomodulatory actions and lipophilic properties of PEN, the objective of this study was to elucidate the mechanism(s) of action of the immunomodulatory action(s) of PEN in macrophages through the modulation of phospholipase A₂ (PLA₂) activity that might be crucial in the antileishmanial action of PEN. Therefore, in this study, we investigated whether PEN would modulate the activity of PLA₂ in RAW 264.7 macrophages and mouse bone marrow-derived primary macrophages (BMDMs) in vitro and further determined how the upstream PLA₂ activation would regulate the downstream cytokine release in the macrophages. Our current results demonstrated that (i) PEN induced PLA₂ activation (arachidonic acid release) in a dose- and time-dependent manner that was regulated upstream by the mitogen-activated protein kinases (MAPKs); (ii) the PEN-induced activation of PLA₂ was attenuated by the cPLA₂-specific pharmacological inhibitors; and (iii) the cPLA₂-specific pharmacological inhibitors attenuated the release of inflammatory cytokines from the macrophages. For the first time, our current study demonstrated that PEN exhibited its immunomodulatory actions through the activation of cPLA₂ in the macrophages, which potentially could be used in the development of a pharmacological intervention against leishmaniasis.

Synergism of in vitro plasmodicidal activity of phospholipase A2 isoforms isolated from panamanian Bothrops asper venom

Bothrops asper is one of the most important snake species in Central America, mainly because of its medical importance in countries like Ecuador, Panama and Costa Rica, where this species causes a high number of snakebite accidents. Several basic phospholipases A₂ (PLA₂s) have been previously characterized from B. asper venom, but few studies have been carried out with its acidic isoforms. In addition, since snake venom is a rich source of bioactive substances, it is necessary to investigate the biotechnological potential of its components. In this context, this study aimed to carry out the biochemical characterization of PLA₂ isoforms isolated from B. asper venom and to evaluate the antiparasitic potential of these toxins. The venom and key fractions were subjected to different chromatographic steps, obtaining nine PLA₂s, four acidic ones (BaspAc-I, BaspAc-II, BaspAc-III and BaspAc-IV) and five basic ones (BaspB-I, BaspB-II, BaspB-III, BaspB-IV and BaspB-V). The isoelectric points of the acidic PLA₂s were also determined, which presented values ranging between 4.5 and 5. The findings indicated the isolation of five unpublished isoforms, four Asp49-PLA, corresponding to the group of acidic isoforms, and one Lys49-PLA₂-like. Acidic PLA₂s catalyzed the degradation of all substrates evaluated; however, for the basic PLA₂s, there was a preference for phosphatidylglycerol and phosphatidic acid. The antiparasitic potential of the toxins was evaluated, and the acidic PLA₂s demonstrated action against the epimastigote forms of T. cruzi and promastigote forms of L. infantum, while the basic PLA₂s BaspB-II and BaspB-IV showed activity against P. falciparum. The results indicated an increase of up to 10 times in antiplasmodial activity, when the Asp49-PLA₂ and Lys49-PLA₂ were associated with one another, denoting synergistic action between these PLA₂ isoforms. These findings correspond to the first report of synergistic antiplasmodial action for svPLA₂s, demonstrating that these molecules may be important targets in the search for new antiparasitic agents.

Crotalus Durissus Ruruima: Current Knowledge on Natural History, Medical Importance, and Clinical Toxinology

Crotalus durissus ruruima is a rattlesnake subspecies mainly found in Roraima, the northernmost state of Brazil. Envenomings caused by this subspecies lead to severe clinical manifestations (e.g. respiratory muscle paralysis, rhabdomyolysis, and acute renal failure) that can lead to the victim’s death. In this review, we comprehensively describe C. d. ruruima biology and the challenges this subspecies poses for human health, including morphology, distribution, epidemiology, venom cocktail, clinical envenoming, and the current and future specific treatment of envenomings by this snake. Moreover, this review presents maps of the distribution of the snake subspecies and evidence that this species is responsible for some of the most severe envenomings in the country and causes the highest lethality rates. Finally, we also discuss the efficacy of the Brazilian horse-derived antivenoms to treat C. d. ruruima envenomings in Roraima state.

In vivo neutralization of bee venom lethality by IgY antibodies

Bee venom is a complex mixture of molecules, among which melittin and phospholipase A₂ (PLA₂) are the toxic components involved in envenoming accidents with multiple honeybee stings. Traditionally, the treatment of envenomings has been based on the administration of specific antibodies to neutralize the deleterious effects of toxins. An alternative to mammalian polyclonal antibodies is the use of egg yolk immunoglobulins (IgY) due to their advantages regarding animal welfare and lower costs of production as compared to the conventional production methods. In this work, a novel composition containing specific IgY antibodies was developed. After four immunizations, IgY extracted from the egg yolks was able to recognize several components of the bee venom, including melittin and PLA₂. The performance of IgY to neutralize the lethal activity was evaluated in a mouse model by using one median lethal dose (LD₅₀) of the bee venom. The effective dose of the IgY extract was determined as 30.66 μg/mg. These results demonstrate the feasibility to produce IgY-based antivenoms to treat envenomings by multiple bee stings.

Unraveling the structure and function of CdcPDE: A novel phosphodiesterase from Crotalus durissus collilineatus snake venom

This study reports the isolation, structural, biochemical, and functional characterization of a novel phosphodiesterase from Crotalus durissus collilineatus venom (CdcPDE). CdcPDE was successfully isolated from whole venom using three chromatographic steps and represented 0.7% of total protein content. CdcPDE was inhibited by EDTA and reducing agents, demonstrating that metal ions and disulfide bonds are necessary for its enzymatic activity. The highest enzymatic activity was observed at pH 8-8.5 and 37 °C. Kinetic parameters indicated a higher affinity for the substrate bis(p-nitrophenyl) phosphate compared to others snake venom PDEs. Its structural characterization was done by the determination of the protein primary sequence by Edman degradation and mass spectrometry, and completed by the building of molecular and docking-based models. Functional in vitro assays showed that CdcPDE is capable of inhibiting platelet aggregation induced by adenosine diphosphate in a dose-dependent manner and demonstrated that CdcPDE is cytotoxic to human keratinocytes. CdcPDE was recognized by the crotalid antivenom produced by the Instituto Butantan. These findings demonstrate that the study of snake venom toxins can reveal new molecules that may be relevant in cases of snakebite envenoming, and that can be used as molecular tools to study pathophysiological processes due to their specific biological activities.

Biogeographical venom variation in the Indian spectacled cobra (Naja naja) underscores the pressing need for pan-India efficacious snakebite therapy

Background

Snake venom composition is dictated by various ecological and environmental factors, and can exhibit dramatic variation across geographically disparate populations of the same species. This molecular diversity can undermine the efficacy of snakebite treatments, as antivenoms produced against venom from one population may fail to neutralise others. India is the world’s snakebite hotspot, with 58,000 fatalities and 140,000 morbidities occurring annually. Spectacled cobra (Naja naja) and Russell’s viper (Daboia russelii) are known to cause the majority of these envenomations, in part due to their near country-wide distributions. However, the impact of differing ecologies and environment on their venom compositions has not been comprehensively studied.

Methods

Here, we used a multi-disciplinary approach consisting of venom proteomics, biochemical and pharmacological analyses, and in vivo research to comparatively analyse N. naja venoms across a broad region (>6000 km; seven populations) covering India’s six distinct biogeographical zones.

Findings

By generating the most comprehensive pan-Indian proteomic and toxicity profiles to date, we unveil considerable differences in the composition, pharmacological effects and potencies of geographically-distinct venoms from this species and, through the use of immunological assays and preclinical experiments, demonstrate alarming repercussions on antivenom therapy. We find that commercially-available antivenom fails to effectively neutralise envenomations by the pan-Indian populations of N. naja, including a complete lack of neutralisation against the desert Naja population.

Conclusion

Our findings highlight the significant influence of ecology and environment on snake venom composition and potency, and stress the pressing need to innovate pan-India effective antivenoms to safeguard the lives, limbs and livelihoods of the country’s 200,000 annual snakebite victims.

Annually, India is burdened by the highest number of snake envenomations across the globe, with over 58,000 fatalities and three times the number of morbidities, predominantly affecting the rural agrarian communities. The spectacled cobra (Naja naja) and Russell’s viper (Daboia russelii) are responsible for the vast majority of envenomations in the country, in part, due to their near country-wide distributions. In this study, we unveil the astounding differences in venom composition of N. naja from six different biogeographical zones across the country (>6000 km). We provide a comprehensive account of their disparate venom proteomic profiles, biochemical and pharmacological effects, and the associated potencies. Our study uncovers alarming differences in the efficacy of the marketed polyvalent antivenoms in neutralising these venoms, thereby, emphasising the pressing need to develop dose-efficacious and pan-India effective antivenoms for the treatment of snakebites in the country. This study also highlights the significant influence of ecology and diverse environments on the venom variability, insinuating the necessity for innovating cost-effective and pan-India efficacious solutions to safeguard the lives, limbs and livelihoods of India’s two hundred thousand annual snakebite victims.

Potent virucidal activity of honeybee "Apis mellifera" venom against Hepatitis C Virus

Hepatitis C virus (HCV) is a global viral widespread without an available vaccine to prevent infection. HCV infection can cause serious liver diseases such as hepatocellular carcinoma (HCC). Current treatment of HCV infection depends on the FDA approved direct-acting antivirals (DAAs) which have side effects and expensive. Thus, development of a novel, more efficient, along with affordable pricing anti-HCV agents is still required. The purpose of the present study is to evaluate the antiviral effects of bee venom (BV) from the honeybee Apis mellifera on the HCV replication life cycle. The crude venom and its components were examined for their anti-HCV activities using Huh7it-1 cultured cells and the JFH1 strain of HCV genotype 2a. Results revealed that BV inhibited HCV infection with 50% inhibitory concentration (IC₅₀) of 0.05 ng/ml, while the 50% cytotoxic concentration (CC₅₀) being 20,000 ng/ml. The venom directly blocked HCV/cell entry by acting on virus particles in a dose dependent manner, whereas no interference on the host cells. Furthermore, venom showed no inhibitory effect on HCV replication and release. Interestingly, none of the main BV components including the mast cell degranulating peptide (MCD), mpamin, or the small peptides melittin (MLT) showed anti-HCV activity up to 5 μg/ml. In conclusion, these results suggest that BV has a direct virucidal activity against HCV and may exert its antiviral effect through a non-common peptide(s) or toxin complex within the crude venom. Therefore, the crude BV can be considered as a promising candidate for characterization and development of new and natural anti-HCV therapeutic agents.

Enzymatic activity and brine shrimp lethality of venom from the large brown spitting cobra (Naja ashei) and its neutralization by antivenom

Objective

Naja ashei is a snake of medical importance in Kenya, Ethiopia, Somalia, Uganda, and Tanzania. Little is known about the enzymatic (snake venom phospholipases A₂; svPLA₂’s) and toxic (lethal) activities of N. ashei venom and crucially, the safety and capacity of available antivenom to neutralize these effects. This study aimed to determine the enzymatic and toxic activities of N. ashei venom and the capacity of Indian and Mexican manufactured antivenoms to neutralize these effects. The protein content of the venom and the test antivenoms were also evaluated. A 12-point log concentration–response curve (0.5–22.5 µg/mL) was generated on an agarose-egg yolk model to predict the svPLA₂ activity of the venom. The toxicity profiles of the venom and antivenoms were evaluated in the brine shrimp lethality assay. Lowry’s method was used for protein estimation.

Results

Low and intermediate concentrations of the venom exhibited similar svPLA₂ activities. The same was true for concentrations > 15 µg/mL. Intermediate and high doses of the venom exhibited similar mortalities in brine shrimp and test antivenoms were generally non-toxic but poorly neutralized svPLA₂ activity. Mexican manufactured antivenom had lower protein content but neutralized venom-induced brine shrimp lethality much more effectively than Indian manufactured antivenom.

An in vitro methodology for discovering broadly-neutralizing monoclonal antibodies

Broadly-neutralizing monoclonal antibodies are of high therapeutic utility against infectious diseases caused by bacteria and viruses, as well as different types of intoxications. Snakebite envenoming is one such debilitating pathology, which is currently treated with polyclonal antibodies derived from immunized animals. For the development of novel envenoming therapies based on monoclonal antibodies with improved therapeutic benefits, new discovery approaches for broadly-neutralizing antibodies are needed. Here, we present a methodology based on phage display technology and a cross-panning strategy that enables the selection of cross-reactive monoclonal antibodies that can broadly neutralize toxins from different snake species. This simple in vitro methodology is immediately useful for the development of broadly-neutralizing (polyvalent) recombinant antivenoms with broad species coverage, but may also find application in the development of broadly-neutralizing antibodies against bacterial, viral, and parasitic agents that are known for evading therapy via resistance mechanisms and antigen variation.