Snake venomics and antivenomics of Protobothrops mucrosquamatus and Viridovipera stejnegeri from Taiwan: Keys to understand the variable immune response in horses

Proteomic and functional characterisation of Trimeresurus popeiorum (Pope's pit viper) venom proteins: Role of enzymatic and non-enzymatic venom toxins in envenomation pathophysiology

Snakebite remains a significant public health issue in tropical regions, with 4.5 to 5.4 million incidents annually. Trimeresurus popeiorum (Pope's Pit Viper), found in Southeast Asia and northeast India, poses a potential threat, yet its venom's protein composition and toxicity are poorly understood. In this study, we used label-free quantitative proteomics to analyze the venom of T. popeiorum, identifying 106 proteins across 12 venom protein families. Notably, 60 % of the venom consisted of proteolytic enzymes, correlating with its prominent metalloprotease, fibrin(ogen)lytic, procoagulant, and thrombin-like activities. The proteome composition also correlates with the clinical effects such as consumption coagulopathy and local effects, seen in victims of Pit Viper envenomation in northeast India. Our findings suggest that T. popeiorum venom is less toxic than other Viperinae species such as Daboia russelii and Echis carinatus, likely due to isoform-level variations in certain toxin classes, including metalloprotease and serine protease. The venom's lethal dose (LD50) in Swiss albino mice was 1 mg/kg, and it caused haemorrhage, tissue necrosis, edema, myotoxicity, and defibrinogenation. Histopathological examination of the TPV-treated mice showed notable toxic effects, including marked hepatic vacuolation in the liver, damage to cardiac muscle and vascular congestion in the heart, bronchial epithelial hyperplasia with cellular infiltration in the interstitial and peribronchiolar regions of the lungs, as well as tubular necrosis and haemorrhage in the kidneys. This research provides the first comprehensive analysis of T. popeiorum venom, highlighting its pharmacological effects and the need for greater medical attention to this lesser-known species.

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

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

Deciphering toxico-proteomics of Asiatic medically significant venomous snake species: A systematic review and interactive data dashboard

Snakebite envenomation (SBE) is a neglected tropical disease (NTD) with an approximate 1.8 million cases annually. The tremendous figure is concerning, and the currently available treatment for snakebite envenomation is antivenom. However, the current antivenom has limited cross-neutralisation activity due to the variations in snake venom composition across species and geographical locations. The proteomics of medically important venomous species is essential as they study the venom compositions within and among different species. The advancement of sophisticated proteomic approaches allows intensive investigation of snake venoms. Nevertheless, there is a need to consolidate the venom proteomics profiles and distribution analysis to examine their variability patterns. This review systematically analysed the proteomics and toxicity profiles of medically important venomous species from Asia across different geographical locations. An interactive dashboard - Asiatic Proteomics Interactive Datasets was curated to consolidate the distribution patterns of the venom compositions, serve as a comprehensive directory for large-scale comparative meta-analyses. The population proteomics demonstrate higher diversities in the predominant venom toxins. Besides, inter-regional differences were also observed in Bungarus sp., Naja sp., Calliophis sp., and Ophiophagus hannah venoms. The elapid venoms are predominated with three-finger toxins (3FTXs) and phospholipase A2 (PLA2). Intra-regional variation is only significantly observed in Naja naja venoms. Proteomics diversity is more prominent in viper venoms, with widespread dominance observed in snake venom metalloproteinase (SVMP) and snake venom serine protease (SVSP). Correlations exist between the proteomics profiles and the toxicity (LD50) of the medically important venomous species. Additionally, the predominant toxins, alongside their pathophysiological effects, were highlighted and discussed as well. The insights of interactive toxico-proteomics datasets provide comprehensive frameworks of venom dynamics and contribute to developing antivenoms for snakebite envenomation. This could reduce misdiagnosis of SBE and accelerate the researchers' data mining process.

Development of antibody-detection ELISA based on beta-bungarotoxin for evaluation of the neutralization potency of equine plasma against Bungarus multicinctus in Taiwan

Animal testing has been the primary approach to assess the neutralization potency of antivenom for decades. However, the necessity to sacrifice large numbers of experimental animals during this process has recently raised substantial welfare concerns. Furthermore, the laborious and expensive nature of animal testing highlights the critical need to develop alternative in vitro assays. Here, we developed an antibody-detection enzyme-linked immunosorbent assay (ELISA) technique as an alternative approach to evaluate the neutralization potency of hyperimmunized equine plasma against B. multicinctus, a medically important venomous snake in Taiwan. Firstly, five major protein components of B. multicinctus venom, specifically, α-BTX, β-BTX, γ-BTX, MTX, and NTL, were isolated. To rank their relative medical significance, a toxicity score system was utilized. Among the proteins tested, β-BTX presenting the highest score was regarded as the major toxic component. Subsequently, antibody-detection ELISA was established based on the five major proteins and used to evaluate 55 hyperimmunized equine plasma samples with known neutralization potency. ELISA based on β-BTX, the most lethal protein according to the toxicity score, exhibited the best sensitivity (75.6 %) and specificity (100 %) in discriminating between high-potency and low-potency plasma, supporting the hypothesis that highly toxic proteins offer better discriminatory power for potency evaluation. Additionally, a phospholipase A2 (PLA2) competition process was implemented to eliminate the antibodies targeting toxicologically irrelevant domains. This optimization greatly enhanced the performance of our assay, resulting in sensitivity of 97.6 % and specificity of 92.9 %. The newly developed antibody-detection ELISA presents a promising alternative to in vivo assays to determine the neutralization potency of antisera against B. multicinctus during the process of antivenom production.

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.

Viper Venom Phospholipase A2 Database: The Structural and Functional Anatomy of a Primary Toxin in Envenomation

Viper venom phospholipase A2 enzymes (vvPLA2s) and phospholipase A2-like (PLA2-like) proteins are two of the principal toxins in viper venom that are responsible for the severe myotoxic and neurotoxic effects caused by snakebite envenoming, among other pathologies. As snakebite envenoming is the deadliest neglected tropical disease, a complete understanding of these proteins' properties and their mechanisms of action is urgently needed. Therefore, we created a database comprising information on the holo-form, cofactor-bound 3D structure of 217 vvPLA2 and PLA2-like proteins in their physiologic environment, as well as 79 membrane-bound viper species from 24 genera, which we have made available to the scientific community to accelerate the development of new anti-snakebite drugs. In addition, the analysis of the sequenced, 3D structure of the database proteins reveals essential aspects of the anatomy of the proteins, their toxicity mechanisms, and the conserved binding site areas that may anchor universal interspecific inhibitors. Moreover, it pinpoints hypotheses for the molecular origin of the myotoxicity of the PLA2-like proteins. Altogether, this study provides an understanding of the diversity of these toxins and how they are conserved, and it indicates how to develop broad, interspecies, efficient small-molecule inhibitors to target the toxin's many mechanisms of action.

Venom Proteomics of Trimeresurus gracilis, a Taiwan-Endemic Pitviper, and Comparison of Its Venom Proteome and VEGF and CRISP Sequences with Those of the Most Related Species

Trimeresurus gracilis is an endemic alpine pitviper in Taiwan with controversial phylogeny, and its venom proteome remains unknown. In this study, we conducted a proteomic analysis of T. gracilis venom using high-performance liquid chromatography-tandem mass spectrometry and identified 155 toxin proteoforms that belong to 13 viperid venom toxin families. By searching the sequences of trypsin-digested peptides of the separated HPLC fractions against the NCBI database, T. gracilis venom was found to contain 40.3% metalloproteases (SVMPs), 15.3% serine proteases, 6.6% phospholipases A2, 5.0% L-amino acid oxidase, 4.6% Cys-rich secretory proteins (CRISPs), 3.2% disintegrins, 2.9% vascular endothelial growth factors (VEGFs), 1.9% C-type lectin-like proteins, and 20.2% of minor toxins, nontoxins, and unidentified peptides or compounds. Sixteen of these proteoforms matched the toxins whose full amino-acid sequences have been deduced from T. gracilis venom gland cDNA sequences. The hemorrhagic venom of T. gracilis appears to be especially rich in PI-class SVMPs and lacks basic phospholipase A2. We also cloned and sequenced the cDNAs encoding two CRISP and three VEGF variants from T. gracilis venom glands. Sequence alignments and comparison revealed that the PI-SVMP, kallikrein-like proteases, CRISPs, and VEGF-F of T. gracilis and Ovophis okinavensis are structurally most similar, consistent with their close phylogenetic relationship. However, the expression levels of some of their toxins were rather different, possibly due to their distinct ecological and prey conditions.

Phylogeny-Related Variations in Venomics: A Test in a Subset of Habu Snakes (Protobothrops)

We conducted a comparative analysis to unveil the divergence among venoms from a subset of Old World habu snakes (Protobothrops) in terms of venomic profiles and toxicological and enzymatic activities. A total of 14 protein families were identified in the venoms from these habu snakes, and 11 of them were shared among these venoms. The venoms of five adult habu snakes were overwhelmingly dominated by SVMP (32.56 ± 13.94%), PLA₂ (22.93 ± 9.26%), and SVSP (16.27 ± 4.79%), with a total abundance of over 65%, while the subadult P. mangshanensis had an extremely low abundance of PLA₂ (1.23%) but a high abundance of CTL (51.47%), followed by SVMP (22.06%) and SVSP (10.90%). Apparent interspecific variations in lethality and enzymatic activities were also explored in habu snake venoms, but no variations in myotoxicity were found. Except for SVSP, the resemblance of the relatives within Protobothrops in other venom traits was estimated to deviate from Brownian motion evolution based on phylogenetic signals. A comparative analysis further validated that the degree of covariation between phylogeny and venom variation is evolutionarily labile and varies among clades of closely related snakes. Our findings indicate a high level of interspecific variation in the venom proteomes of habu snakes, both in the presence or absence and the relative abundance of venom protein families, and that these venoms might have evolved under a combination of adaptive and neutral mechanisms.

Immunoprofiling of Equine Plasma against Deinagkistrodon acutus in Taiwan: Key to Understanding Differential Neutralization Potency in Immunized Horses

Snakebite envenoming is a public health issue linked to high mortality and morbidity rates worldwide. Although antivenom has been the mainstay treatment for envenomed victims receiving medical care, the diverse therapeutic efficacy of the produced antivenom is a major limitation. Deinagkistrodon acutus is a venomous snake that poses significant concern of risks to human life in Taiwan, and successful production of antivenom against D. acutus envenoming remains a considerable challenge. Among groups of horses subjected to immunization schedules, few or none subsequently meet the quality required for further scale-up harvesting. The determinants underlying the variable immune responses of horses to D. acutus venom are currently unknown. In this study, we assessed the immunoprofiles of high-potency and low-potency horse plasma against D. acutus venom and explored the conspicuous differences between these two groups. Based on the results of liquid chromatography with tandem mass spectrometry (LC-MS/MS), acutolysin A was identified as the major component of venom proteins that immunoreacted differentially with the two plasma samples. Our findings indicate underlying differences in antivenoms with variable neutralization efficacies, and may provide valuable insights for improvement of antivenom production in the future.

Proteome Decomplexation of Trimeresurus erythrurus Venom from Mizoram, India

Green pit vipers are the largest group of venomous vipers in tropical and subtropical Asia, which are responsible for most of the bite cases across this region. Among the green pit vipers of the Indian subcontinent, Trimeresurus erythrurus is the most prevalent; however, limited knowledge is available about its venomics. Proteome decomplexation of T. erythrurus venom using mass spectrometry revealed a blend of 53 different proteins/peptides belonging to 10 snake venom protein families. Phospholipase A₂ and snake venom serine proteases were found to be the major enzymatic families, and Snaclec was the major nonenzymatic family in this venom. These protein families might be responsible for consumptive coagulopathy in victims. Along with these, snake venom metalloproteases, l-amino acid oxidases, disintegrins, and cysteine-rich secretory proteins were also found, which might be responsible for inducing painful edema, tissue necrosis, blistering, and defibrination in patients. Protein belonging to C-type lectins, C-type natriuretic peptides, and glutaminyl-peptide cyclotransfreases were also observed as trace proteins. The crude venom shows platelet aggregation in the absence of any agonist, suggesting their role in alterations in platelet functions. This study is the first proteomic analysis of T. erythrurus venom, contributing an overview of different snake venom proteins/peptides responsible for various pathophysiological disorders obtained in patients. Data are available via ProteomeXchange with the identifier PXD038311.

Comparison of Protein Variation in Protobothrops mucrosquamatus Venom between Northern and Southeast Taiwan and Association with Human Envenoming Effects

Reports of bite from Protobothrops mucrosquamatus (Pmu) are frequent in Taiwan, and its wide-spread distribution and diverse habitats drove us to investigate its envenoming effects and relevant venom variations. We used reversed-phase high-performance liquid chromatography and mass spectrometry to analyze 163 Pmu venom samples collected from northern and southeastern Taiwan. Twenty-two major protein fractions were separated and analyzed, and their contents were determined semi-quantitatively. The results showed that despite the trivial differences in the protein family, there is an existing variation in acidic phospholipases A₂s, serine proteinases, metalloproteinases, C-type lectin-like proteins, and other less abundant components in the Pmu venoms. Moreover, clinical manifestations of 209 Pmu envenomed patients hospitalized in northern or southeastern Taiwan revealed significant differences in local symptoms, such as ecchymosis and blistering. The mechanism of these local effects and possibly relevant venom components were examined. Further analysis showed that certain venom components with inter-population variation might work alone or synergistically with others to aggravate the local effects. Therefore, our findings of the venom variation may help one to improve antivenom production and better understand and manage Pmu bites.

Uncommon defibrinogenation and coagulopathy caused by Trimeresurus stejnegeri stejnegeri envenomation in a patient with swelling above the ankle

In Taiwan, Trimeresurus stejnegeri stejnegeri (Stejneger's Bamboo pitviper) is responsible for more than half of all venomous snakebites annually. This species often causes local envenoming characterized by tissue swelling and pain, occasional local ecchymosis, bullae and blister formation, and lymphangitis and lymphadenitis. The pathophysiology and treatment of potentially life-threatening coagulopathy and defibrinogenation induced by T. s. stejnegeri systemic envenoming have not been specifically addressed. Here, we describe the case of a man who was bitten by T. s. stejnegeri on his right first toe, which later developed into swelling above the ankle. It was found that there was severe hypofibrinogenemia, prolonged prothrombin time, and reduced activities of factors V and XI, plasminogen, and α2-antiplasmin. Even though a favorable outcome was achieved after repeatedly administering specific antivenom, fresh frozen plasma, and cryoprecipitate, probably low effectiveness of antivenom against the coagulopathy and prodigious amounts of replacement products were observed. To control coagulopathy early and avoid the needless replacement of coagulation factor, which are associated with inherent adverse reactions, more frequent serial blood assessment (e.g., every 6 h) and higher initial antivenom doses may be helpful. Knowledge of the specific coagulation factor deficiencies may improve our understanding of the relationship between hemotoxins and the resulting envenoming syndromes in this snakebite.

Bibliometric Analysis of Literature in Snake Venom-Related Research Worldwide (1933-2022)

Snake envenomation is a severe economic and health concern affecting countries worldwide. Snake venom carries a wide variety of small peptides and proteins with various immunological and pharmacological properties. A few key research areas related to snake venom, including its applications in treating cancer and eradicating antibiotic-resistant bacteria, have been gaining significant attention in recent years. The goal of the current study was to analyze the global profile of literature in snake venom research. This study presents a bibliometric review of snake venom-related research documents indexed in the Scopus database between 1933 and 2022. The overall number of documents published on a global scale was 2999, with an average annual production of 34 documents. Brazil produced the highest number of documents (n = 729), followed by the United States (n = 548), Australia (n = 240), and Costa Rica (n = 235). Since 1963, the number of publications has been steadily increasing globally. At a worldwide level, antivenom, proteomics, and transcriptomics are growing hot issues for research in this field. The current research provides a unique overview of snake venom research at global level from 1933 through 2022, and it may be beneficial in guiding future research.

Sequence determination and bioinformatic comparison of ten venom serine proteases of Trimeresurus gracilis, a Taiwanese endemic pitviper with controversial taxonomy

Trimeresurus gracilis (Tgc) is endemic to Taiwan and shown to be closely related with Ovophis okinavensis by previous phylogenetic analyses, but their taxonomic status remain controversial. Here, we cloned and sequenced ten of its venom serine-proteases (designated as Tgc-vSPs). All the Tgc-vSPs conserve the catalytic triads, six appear to be kallikrein-like (KNs) and four are plasminogen-activator homologs (PAHs and PAs). They are studied under four structural categories: (1) highly similar Tgc-KN1, Tgc-KN2 and Tgc-KN3, with four predicted N-glycosylation sites; (2) Tgc-KN4, with a single N -glycosylation site; (3) Tgc-KN5 and Tgc-KN6, with two distinct N-glycosylation sites; (4) Tgc-PAH1/PAH2, TgcPA3, and Tgc-PA4, with two conserved N-glycosylation sites. Additionally, Tgc-KN1, Tgc-KN4 and Tgc-PAH1 were purified by reversed-phase HPLC and identified by peptide-mass-fingerprinting. Results of BLAST and sequence alignments reveal that Tgc-KN1∼3 and Tgc-KN6 are most like the vSPs of rattlesnakes, while the sequences of Tgc-KN4, KN5 and Tgc-PAH1/PAH2 match closely to the partial sequences of three O. okinavensis vSPs. Thus, our results reveal non-overlapping similarities of Tgc-vSPs to the O. okinavensis vSPs and vSPs of the New World pitvipers. In addition, molecular phylogenetic analyses of the plasminogen-activator like vSPs reveal separate evolution of two clusters of the enzymes with distinct functions.

Development of Antibody Detection ELISA Based on Immunoreactive Toxins and Toxin-Derived Peptides to Evaluate the Neutralization Potency of Equine Plasma against Naja atra in Taiwan

Naja atra, also known as Taiwanese cobra, is one of the most prevalent venomous snakes in Taiwan. Clinically, freeze-dried neurotoxic antivenom (FNAV) produced from horses by Taiwan Centers for Disease Control (CDC) has been the only approved treatment for N. atra envenoming for the last few decades. During antivenom production, large numbers of mice are used in the in vivo assay to determine whether the neutralization potency of hyperimmunized equines is satisfactory for large-scale harvesting. However, this in vivo assay is extremely laborious, expensive, and significantly impairs animal welfare. In the present study, we aimed to develop an in vitro ELISA-based system that could serve as an alternative assay to evaluate the neutralization potency of plasma from hyperimmunized equines. We initially obtained 51 plasma samples with known (high or low) neutralization potency assessed in vivo from 9 hyperimmunized equines and subsequently determined their antibody titers against the five major protein components of N. atra venom (neurotoxin (NTX), phospholipase A2 (PLA₂), cytotoxin (CTX), cysteine-rich secretory protein (CRISP), and snake venom metalloproteinase (SVMP)) via ELISA. The antibody titer against NTX was the most effective in discriminating between high and low potency plasma samples. To identify the specific epitope(s) of NTX recognized by neutralization potency-related antibodies, 17 consecutive NTX-derived pentadecapeptides were synthesized and used as antigens to probe the 51 equine plasma samples. Among the 17 peptides, immunoreactive signals for three consecutive peptides (NTX1-8, NTX1-9, and NTX1-10) were significantly higher in the high potency relative to low potency equine plasma groups (p < 0.0001). Our ELISA system based on NTX1-10 peptide (RWRDHRGYRTERGCG) encompassing residues 28–42 of NTX displayed optimal sensitivity (96.88%) and specificity (89.47%) for differentiating between high- and low-potency plasma samples (area under the receiver operating characteristic curve (AUC) = 0.95). The collective data clearly indicate that the antibody titer against NTX protein or derived peptides can be used to efficiently discriminate between high and low neutralization potency of plasma samples from venom-immunized horses. This newly developed antibody detection ELISA based on NTX or its peptide derivatives has good potential to complement or replace the in vivo rodent assay for determining whether the neutralization potency of equine plasma is satisfactory for large-scale harvesting in the antivenom production process against N. atra.

A Strategy for Efficient Preparation of Genus-Specific Diagnostic Antibodies for Snakebites

As said by former United Nations Secretary-General Kofi Annan, "Snakebite is the most important tropical disease you've never heard of." Listed as a priority neglected tropical disease by the World Health Organization, snakebite envenoming (SBE) kills in excess of 125,000 people per year. However, due to the complexity and overlap of snake venom compositions, few reliable venom diagnostic methods for genus-/species-specific identification, which is crucial for successful SBE therapy, are available. Here, we develop a strategy to select and prepare genus-specific snake venom antibodies, which allows rapid and efficient clinical diagnosis of snakebite. Multi-omics approaches are used to choose candidate antigens from snake venoms and identify genus-specific antigenic epitope peptide fragments (GSAEPs) with ideal immunogenicity, specificity, and spatial accessibility. Double-antibody sandwich ELISA kit was established by matching a polyclonal antibody against a natural antigen and a monoclonal antibody that was prepared by natural protein as antigen and can specifically target the GSAEPs. The kit shows the ability to accurately identify venoms from similar genera of Trimeresurus and Protobothrops with a detection limit of 6.25 ng/ml on the snake venoms and a little cross-reaction, thus proving high feasibility and applicability.

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.

Potential para-specific and geographical utility of Thai Green Pit Viper (Trimeresurus albolabris) Monovalent Antivenom: Neutralization of procoagulant and hemorrhagic activities of diverse Trimeresurus pit viper venoms

The Trimeresurus complex consists of diverse medically important venomous pit vipers that cause snakebite envenomation. Antivenoms, however, are in limited supply, and are specific to only two out of the many species across Asia. This study thus investigated the immunoreactivities of regional pit viper antivenoms toward selected Trimeresurus pit viper venoms, and examined the neutralization of their hemotoxic activities. Trimeresurus albolabris Monovalent Antivenom (TaMAV, Thailand) exhibited a higher immunoreactivity than Hemato Bivalent Antivenom (HBAV, raised against Trimeresurus stejnegeri and Protobothrops mucrosquamatus, Taiwan) and Gloydius brevicaudus Monovalent Antivenom (GbMAV, China), attributed to its monovalent nature and conserved antigens in the Trimeresurus pit viper venoms. The venoms showed moderate-to-strong in vitro procoagulant and in vivo hemorrhagic effects consistent with hemotoxic envenomation, except for the Sri Lankan Trimeresurus trigonocephalus venom which lacked hemorrhagic activity. TaMAV was able to differentially neutralize both in vitro and in vivo hemotoxic effects of the venoms, with the lowest efficacy shown against the procoagulant effect of T. trigonocephalus venom. The findings suggest that TaMAV is a potentially useful treatment for envenomation caused by hetero-specific Trimeresurus pit vipers, in particular those in Southeast Asia and East Asia. Clinical study is warranted to establish its spectrum of para-specific effectiveness, and dosages need be tailored to the different species in respective regions.

Snake venom proteomics and antivenomics of two Sundaic lance-headed pit vipers: Trimeresurus wiroti (Malaysia) and Trimeresurus puniceus (Indonesia)

Envenomation by two medically important Sundaic pit vipers, Trimeresurus wiroti (Malaysia) and Trimeresurus puniceus (Indonesia), causes hemotoxic syndrome with a potentially fatal outcome. Research on the compositions and antigenicity of these pit viper venoms is however lacking, limiting our understanding of the pathophysiology and treatment of envenomation. This study investigated the venom proteomes of both species through a protein decomplexation strategy, applying C₁₈ reverse-phase high-performance liquid chromatography followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and protein identification through nano-electrospray ionization liquid chromatography-tandem mass spectrometry (nano-ESI-LCMS/MS) of trypsin-digested peptides. The venom antigenicity was profiled against the Thai Green Pit Viper Antivenom (GPVAV, a hetero-specific antivenom), using indirect enzyme-linked immunosorbent assay (ELISA). The venom proteomes of T. wiroti and T. puniceus consisted of 10 and 12 toxin families, respectively. The major proteins were of diverse snake venom serine proteases (19-30% of total venom proteins), snake venom metalloproteinases (17-26%), disintegrins (9-16%), phospholipases A₂ (8-28%) and C-type lectins (~8%). These were putative snake toxins implicated in hemorrhage and coagulopathy, consistent with clinical hemotoxicity. GPVAV showed strong immunorecognition toward high and medium molecular weight proteins (e.g., SVMP and PLA₂) in both venoms, while a lower binding activity was observed toward small proteins such as disintegrins. Conserved antigenicity in the major hemotoxins supported toxicity cross-neutralization by GPVAV and indicated that the immunorecognition of low molecular weight toxins may be optimized for improved binding efficacy. Taken together, the study provides insights into the pathophysiology and antivenom treatment of envenomation caused by T. wiroti and T. puniceus in the region.

Effects of Sodium Silicate Complex against Hemorrhagic Activities Induced by Protobothrops mucrosquamatus Venom

Protobothrops mucrosquamatus poses a serious medical threat to humans in Southern and Southeastern Asia. Hemorrhage is one of the conspicuous toxicities related to the pathology of P. mucrosquamatus envenoming. Previous in vitro and in vivo studies showed that a silica-derived reagent, sodium silicate complex (SSC), was able to neutralize hemorrhagic and proteolytic activities induced by pit viper venoms, including Crotalus atrox, Agkistrodon contortrix contortrix and Agkistrodon piscivorus leucostoma. In this study, we validated that SSC could neutralize enzymatic and toxic effects caused by the venom of P. mucrosquamatus. We found that SSC inhibited the hemolytic and proteolytic activities induced by P. mucrosquamatus venom in vitro. In addition, we demonstrated that SSC could block intradermal hemorrhage caused by P. mucrosquamatus venom in a mouse model. Finally, SSC could neutralize lethal effects of P. mucrosquamatus venom in the mice. Therefore, SSC is a candidate for further development as a potential onsite first-aid treatment for P. mucrosquamatus envenoming.

Benefits of Early In-Hospital Antivenom Administration to Patients with Protobothrops mucrosquamatus Envenomation

Protobothrops mucrosquamatus is one of the common venomous snakes in Southeast Asia. This retrospective cohort study conducted in six medical institutions in Taiwan aimed to obtain information on the optimal management strategies for P. mucrosquamatus snakebite envenomation. Data were extracted from the Chang Gung Research Database from January 2006 to December 2016. The association between early antivenom administration and patient demographics, pain requiring treatment with analgesic injections, and hospital length of stay was analyzed. A total of 195 patients were enrolled; 130 were administered antivenom within 1 hour after emergency department arrival (early group), whereas 65 were treated later than 1 hour after arrival (late group). No in-hospital mortality was identified. The difference in surgical intervention rates between the early and late groups was statistically insignificant (P = 0.417). Compared with the early group, the late group showed a higher rate of antivenom skin test performance (46.9% versus 63.1%, respectively, P = 0.033), longer hospital stay (42 ± 62 hours versus 99 ± 70 hours, respectively, P = 0.016), and higher rate of incidences of pain requiring treatment with analgesic injections (29.2% versus 46.2%, respectively, P = 0.019). After adjusting for confounding factors, early antivenom administration was associated with decreased pain requiring treatment with analgesic injections (adjusted odds ratio: 0.51, 95% CI: 0.260-0.985). Antivenom administration within 1 hour of arrival was associated with a decreased likelihood of experiencing pain and hospital length of stay in patients with P. mucrosquamatus snakebites. Antivenom skin testing was associated with delays in antivenom administration.

Snake venom proteome of Protobothrops mucrosquamatus in Taiwan: Delaying venom-induced lethality in a rodent model by inhibition of phospholipase A2 activity with varespladib

Protobothrops mucrosquamatus, also known as the brown spotted pit viper or Taiwanese habu, is a medically significant venomous snake in Taiwan, especially in the northern area. To more fully understand the proteome profile of P. mucrosquamatus, we characterized its venom composition using a bottom-up proteomic approach. Whole venom components were fractionated by RP-HPLC and then analyzed by SDS-PAGE. Each protein band in gels was excised and subjected to protein identification by LC-MS/MS. A subsequent proteomic analysis revealed the presence of 61 distinct proteins belonging to 19 families in P. mucrosquamatus venom. Snake venom metalloproteinase (SVMP; 29.4%), C-type lectin (CLEC; 21.1%), snake venom serine protease (SVSP; 17.6%) and phospholipase A₂ (PLA₂; 15.9%) were the most abundant protein families, whereas several low-abundance proteins, categorized into eight protein families, were demonstrated in P. mucrosquamatus venom for the first time. Because PLA₂ is known to make a major contribution to venom lethality, we evaluated whether the known PLA₂ inhibitor, varespladib, was capable of preventing the toxic effects of P. mucrosquamatus venom. This small-molecule drug demonstrated the ability to inhibit PLA₂ activity in vitro (IC₅₀ = 101.3 nM). It also blunted lethality in vivo, prolonging survival following venom injection in a mouse model, but it showed limited potency against venom-induced local hemorrhage in this model. Our findings provide essential biological and pathophysiological insights into the composition of P. mucrosquamatus venom and suggest PLA₂ inhibition as an adjunctive or alternative therapeutic strategy in the clinical management of P. mucrosquamatus envenoming in emergency medicine. SIGNIFICANCE: P. mucrosquamatus envenomation is a significant medical concern in Taiwan, especially in the northern region. Although antivenom is commonly used for rescuing P. mucrosquamatus envenoming, severe clinical events still occur, with more than 20% of cases requiring surgical intervention. Small-molecule therapy offers several advantages as a potential adjunctive, or even alternative, to antivenom treatment, such as heat stability, low antigenicity and ease of administration, among others. A deeper understanding of the venom proteome of P. mucrosquamatus would aid in the discovery of small-molecule drugs that could be repurposed to target specific venom proteins. Here, we applied a bottom-up proteomic approach to characterize the protein profile of P. mucrosquamatus venom. Varespladib, a small-molecule drug used to treat inflammatory disease, was repurposed to inhibit the toxicity of P. mucrosquamatus venom, and was shown to reduce the lethal effects of P. mucrosquamatus envenomation in a rodent model. Varespladib might be used as a first-aid therapeutic against P. mucrosquamatus envenoming in the pre-referral period and/or as an adjunctive agent administered together with anti-P. mucrosquamatus antivenom.

Chicken antibodies against venom proteins of Trimeresurus stejnegeri in Taiwan

BACKGROUND

The venom of bamboo vipers (Trimeresurus stejnegeri - TS), commonly found in Taiwan, contains deadly hemotoxins that cause severe envenomation. Equine-derived antivenom is a specific treatment against snakebites, but its production costs are high and there are some inevitable side effects. The aim of the present work is to help in the development of an affordable and more endurable therapeutic strategy for snakebites.

METHODS

T. stejnegeri venom proteins were inactivated by glutaraldehyde in order to immunize hens for polyclonal immunoglobulin (IgY) antibodies production. After IgY binding assays, two antibody libraries were constructed expressing single-chain variable fragment (scFv) antibodies joined by the short or long linker for use in phage display antibody technology. Four rounds of biopanning were carried out. The selected scFv antibodies were then further tested for their binding activities and neutralization assays to TS proteins.

RESULTS

Purified IgY from egg yolk showed the specific binding ability to TS proteins. The dimensions of these two libraries contain 2.4 × 107 and 6.8 × 107 antibody clones, respectively. An increase in the titers of eluted phage indicated anti-TS clones remarkably enriched after 2nd panning. The analysis based on the nucleotide sequences of selected scFv clones indicated that seven groups of short linkers and four groups of long linkers were identified. The recombinant scFvs showed significant reactivity to TS venom proteins and a cross-reaction to Trimeresurus mucrosquamatus venom proteins. In in vivo studies, the data demonstrated that anti-TS IgY provided 100% protective effects while combined scFvs augmented partial survival time of mice injected with a lethal amount of TS proteins.

CONCLUSION

Chickens were excellent hosts for the production of neutralization antibodies at low cost. Phage display technology is available for generation of monoclonal antibodies against snake venom proteins. These antibodies could be applied in the development of diagnostic kits or as an alternative for snakebite envenomation treatment in the near future.

Envenomation by Trimeresurus stejnegeri stejnegeri: clinical manifestations, treatment and associated factors for wound necrosis

Background

Trimeresurus stejnegeri stejnegeri bite induces tissue swelling, pain, thrombocytopenia, rhabdomyolysis, and acute renal failure. However, the incidence of coagulopathy, factors associated with wound necrosis, and the appropriate management of this condition have not been well characterized yet.

Materials

This study included patients bitten by T. s. stejnegeri that were admitted to the study hospitals from 2001 to 2016. Patient characteristics, laboratory data, and management approaches were compared in victims with and without wound necrosis.

Results

A total of 185 patients were evaluated: three patients (1.6%) were asymptomatic; whereas tissue swelling and pain, local ecchymosis, wound necrosis, coagulopathy, thrombocytopenia, rhabdomyolysis, and renal impairment were present in 182, 53, 13, 15, 10, 1, and 3 patients, respectively. One patient died from coagulopathy and hemorrhagic shock. Antivenom was administered to all envenomed patients at a median time of 1.8 h after the bite. The median total dose of antivenom was five vials. Chi-square analysis showed that bitten fingers, using cold packs during first aid, presence of bullae or blisters, lymphangitis or lymphadenitis, local numbness and suspected infection to be significantly associated with wound necrosis. After adjustment using a multivariate logistic regression model, only cold packs as first aid, bulla or blister formation, and wound infection remained significant.

Conclusions

The main effects of T. s. stejnegeri envenomation are tissue swelling, pain, and local ecchymosis. We do not recommend the use of cold packs during first aid to reduce wound pain, as this may be a risk factor for wound necrosis. In addition, patients with bulla or blister formation should be carefully examined for subsequent wound necrosis. Antiplatelet use may worsen systemic bleeding. No severe rhabdomyolysis or renal failure was observed in this large case series, we therefore considered that they were not prominent effects of T. s. stejnegeri bite.

Clinical manifestations and treatments of Protobothrops mucrosquamatus bite and associated factors for wound necrosis and subsequent debridement and finger or toe amputation surgery

INTRODUCTION

Protobothrops mucrosquamatus bite induces wound necrosis, coagulopathy, thrombocytopenia, rhabdomyolysis, and acute renal failure. The severity of the hematological derangements and associated factors for wound necrosis and subsequent surgery and the appropriate management of these conditions have not been well characterized. Although severe renal failure requiring hemodialysis has been reported following P. mucrosquamatus bite, the culprit snake may be erroneously classified.

MATERIALS AND METHODS

A total of 186 patients with P. mucrosquamatus bites were retrospectively evaluated. They were categorized into group 1 (patients receiving debridement or finger/toe amputation) and group 2 (all other patients) to identify the associated factors for surgery. Characteristic data were compared between groups 1 and 2 and between definite and suspected cases.

RESULTS

No differences were observed between definite and suspected cases in terms of symptomatology and management. Of the 186 patients, 7 (3.8%) were asymptomatic, 179 (96.2%) experienced tissue swelling and pain, and 107 (57.5%) had local ecchymosis. Coagulopathy, thrombocytopenia, and renal impairment were found in 13 (7%), 19 (10.2%), and 7 (3.8%) patients, respectively. None of the patients required transfusion therapy or hemodialysis. Furthermore, no systemic bleeding or death occurred. Antivenom was administered to all 179 envenomed patients at a median of 1.5 h post-bite. The median total dose of the specific antivenom was 5.5 vials. In multivariate logistic regression analysis, finger as the bite site, bullae and blister formation, and wound infection were significantly associated with wound necrosis; whereas finger as the bite site and bullae and blister formation were related to debridement or finger/toe amputation.

DISCUSSION AND CONCLUSIONS

Protobothrops mucrosquamatus envenomation mainly exerts effects on local tissue. Systemic effects are uncommon and generally nonsevere and transient after the treatment with the specific antivenom. We speculated that severe renal failure requiring hemodialysis is not a typical finding of P. mucrosquamatus envenomation. Patients with finger as the bite site and bullae or blister formation should be carefully examined for wound necrosis, secondary infection, and subsequent surgery. Further evaluations of the efficacy of antivenom against local tissue effects and the effect of selective antibiotics in the management of bite wound infection are urgently required. Although the antivenom manufacturer suggested a skin test prior to use, we believed that it could be omitted because it does not accurately predict the allergic responses.

Risk factors associated with snake antivenom reaction and the role of skin test

Antivenom reactions are a common complication of snake antivenom. This study aimed to identify predicators of antivenom reaction and the involvement of antivenom skin test in antivenom reaction development. This retrospective cohort study was conducted in six medical institutions in Taiwan. Data were extracted from the Chang Gung Research Database (CGRD) from January 2006 to December 2016. The association between antivenom reaction and patient demographics, type and dose of antivenom, and skin test results was analyzed. The study enrolled 799 patients, including 219 who developed antivenom reactions. Compared to patients receiving both freeze-dried hemorrhagic (FH) and freeze-dried neurotoxic (FN) antivenom, those administered a single type had a lower antivenom reaction risk (adjusted odds ratios [aORs]: 0.5 and 0.4, 95% confidence interval [CI]: 0.35-0.74 and 0.24-0.69, FH and FN respectively). Patients administered a higher antivenom dose (≥ 5 vials) had higher antivenom reaction risk (aOR: 1.8, 95% CI: 1.23-2.76). A positive skin test result was also associated with antivenom reaction (aOR: 16.7, 95% CI: 5.42-51.22). The skin test showed high specificity (98.5%, 95% CI: 97.49%-99.83%) but low sensitivity (17.5%, 95% CI: 10.74%-24.18%). The antivenom skin test should be abolished because of the extremely low sensitivity and possible misinterpretation of results because of the limitation of this examination.

Functional recombinant single-chain variable fragment antibody against Agkistrodon acutus venom

Agkistrodon acutus bites are conventionally treated with animal-derived antivenom, the use of which is limited due to allergic reactions and serum sickness. Thus in the present study, the genes of humanized antibodies produced in response to A. acutus venom were extracted from lymphocytes from patients bitten by A. acutus. A single-chain variable fragment (scFv) library against venom was constructed using a T7 phage display system. ScFv genes that exhibited high affinity to venom were selected by library biopanning. An expression system was constructed for antivenom scFv fused with 6×His tag at its N- and C-terminus using pET-28a (+) vector. The scFv proteins could achieve functional and soluble expression in Escherichia coli via the auto-induction method. The purity and activity of the scFv genes and proteins were confirmed by SDS-PAGE, western blotting and ELISA. The results indicated that three soluble scFv proteins exhibited specific affinity to A. acutus venom and were harvested via the auto-induction method.

Evaluating the physicochemical properties and efficacy of recently expired and aged antivenom products from Thailand and Taiwan

Gel filtration chromatography and gel electrophoresis revealed minimal protein degradation in lyophilized antivenoms which were 2-year expired (Hemato Polyvalent, Neuro Polyvalent; Thailand) and 18-year expired (Hemato Bivalent, Neuro Bivalent; Taiwan). All expired antivenoms retained immunological binding activity, and were able to neutralize the hemotoxic or neurotoxic as well as lethal effects of the homologous snake venoms. The findings show that antivenoms under proper storage conditions may remain relatively stable beyond the indicated shelf life.

Venomics of Trimeresurus (Popeia) nebularis, the Cameron Highlands Pit Viper from Malaysia: Insights into Venom Proteome, Toxicity and Neutralization of Antivenom

Trimeresurus nebularis is a montane pit viper that causes bites and envenomation to various communities in the central highland region of Malaysia, in particular Cameron’s Highlands. To unravel the venom composition of this species, the venom proteins were digested by trypsin and subjected to nano-liquid chromatography-tandem mass spectrometry (LC-MS/MS) for proteomic profiling. Snake venom metalloproteinases (SVMP) dominated the venom proteome by 48.42% of total venom proteins, with a characteristic distribution of P-III: P-II classes in a ratio of 2:1, while P-I class was undetected. Snaclecs constituted the second most venomous protein family (19.43%), followed by snake venom serine proteases (SVSP, 14.27%), phospholipases A₂ (5.40%), disintegrins (5.26%) and minor proteins including cysteine-rich secretory proteins, L-amino acid oxidases, phosphodiesterases, 5′-nucleotidases. The venomic profile correlates with local (painful progressive edema) and systemic (hemorrhage, coagulopathy, thrombocytopenia) manifestation of T. nebularis envenoming. As specific antivenom is unavailable for T. nebularis, the hetero-specific Thai Green Pit viper Monovalent Antivenom (GPVAV) was examined for immunological cross-reactivity. GPVAV exhibited good immunoreactivity to T. nebularis venom and the antivenom effectively cross-neutralized the hemotoxic and lethal effects of T. nebularis (lethality neutralizing potency = 1.6 mg venom per mL antivenom). The findings supported GPVAV use in treating T. nebularis envenoming.

Snake venom proteome and immuno-profiling of the hundred-pace viper, Deinagkistrodon acutus, in Taiwan

Deinagkistrodon acutus, also known as the hundred-pace viper or Chinese moccasin, is a clinically significant venomous snake in Taiwan. To address the lack of knowledge on the venom proteome of D. acutus, the venom composition was studied by a bottom-up proteomic approach combining reverse phase high-performance liquid chromatography, SDS-PAGE, and LC-MS/MS analysis. The immunoreactivity and cross-reactivity of Taiwanese freeze-dried D. acutus antivenom (DA-AV) and hemorrhagic antivenom (FH-AV) were investigated, as well. The proteomic analysis revealed the presence of 29 distinct proteins from D. acutus venom belonging to 8 snake venom protein families. Snake venom metalloproteinase (SVMP, 46.86%), C-type lectin (CLEC, 37.59%), phospholipase A₂ (PLA₂, 7.33%) and snake venom serine protease (SVSP, 6.62%) were the most abundant proteins. In addition to DA-AV, FH-AV also showed a profile of broad immunorecognition toward the venom of D. acutus. Remarkably, both antivenoms specifically reacted with the HPLC fractions containing SVMPs, and the titer was 5-10 times higher than fractions of other components. This information helps us to deeply understand the pathophysiology of D. acutus envenomation and guide us to development of more effective antivenom for clinical treatment.

Antibody Cross-Reactivity in Antivenom Research

Antivenom cross-reactivity has been investigated for decades to determine which antivenoms can be used to treat snakebite envenomings from different snake species. Traditionally, the methods used for analyzing cross-reactivity have been immunodiffusion, immunoblotting, enzyme-linked immunosorbent assay (ELISA), enzymatic assays, and in vivo neutralization studies. In recent years, new methods for determination of cross-reactivity have emerged, including surface plasmon resonance, antivenomics, and high-density peptide microarray technology. Antivenomics involves a top-down assessment of the toxin-binding capacities of antivenoms, whereas high-density peptide microarray technology may be harnessed to provide in-depth knowledge on which toxin epitopes are recognized by antivenoms. This review provides an overview of both the classical and new methods used to investigate antivenom cross-reactivity, the advantages and disadvantages of each method, and examples of studies using the methods. A special focus is given to antivenomics and high-density peptide microarray technology as these high-throughput methods have recently been introduced in this field and may enable more detailed assessments of antivenom cross-reactivity.

Protobothrops mucrosquamatus Bites to the Head: Clinical Spectrum from Case Series

Protobothrops mucrosquamatus (Trimeresurus mucrosquamatus) is a medically important species of pit viper with a wide geographic distribution in Southeast Asia. Bites by P. mucrosquamatus mostly involve the extremities. Little is known about the toxic effects of P. mucrosquamatus envenoming to the head because of the infrequency of such occurrence. To better delineate the clinical manifestations of envenoming to the head, we report three patients who suffered from P. mucrosquamatus bites to the head and were treated successfully. All three patients developed progressive soft tissue swelling extending from head to neck, with two patients expanding further onto the anterior chest wall. Mild thrombocytopenia was noted in two patients. One patient had transient acute renal impairment and airway obstruction, necessitating emergent intubation. All three patients received high doses of species-specific antivenom with recovery within 1 week. No adverse reactions to antivenom were observed.

Differential heme-mediated modulation of Deinagkistrodon, Dispholidus, Protobothrops and Pseudonaja hemotoxic venom activity in human plasma

Envenomation by vipers with hemotoxic enzymes continues to be a worldwide source of morbidity and mortality. The present work examined the effects of exposure of venom enzymes to carbon monoxide and O-phenylhydroxylamine, agents that modulate the biometal heme, by forming carboxyheme and metheme, respectively. Four venoms obtained from medically important, diverse snake venom found in Africa, Asia and Australia were analyzed. The species that had venom tested in human plasma with thrombelastography and heme modulating agents were Deinagkistrodon acutus, Protobothrops mucrosquamatus, Dispholidus typus and Pseudonaja textilis. These venoms varied four hundred-fold in potency (ng-µg/ml) to exert procoagulant effects on human plasma; further, there was species specific variability in venom inhibition after exposure to carboxyheme or metheme agents. Lastly, using a wide range of carbon monoxide concentrations, it was determined that the factor V component of P. textilis venom was likely inhibited before the factor X component. Further investigation using this thrombelastograph-based, venom "kinetomic" methodology involving heme modulation will demonstrate in time its laboratory and clinical utility.

Comprehensive Snake Venomics of the Okinawa Habu Pit Viper, Protobothrops flavoviridis, by Complementary Mass Spectrometry-Guided Approaches

The Asian world is home to a multitude of venomous and dangerous snakes, which are used to induce various medical effects in the preparation of traditional snake tinctures and alcoholics, like the Japanese snake wine, named Habushu. The aim of this work was to perform the first quantitative proteomic analysis of the Protobothrops flavoviridis pit viper venom. Accordingly, the venom was analyzed by complimentary bottom-up and top-down mass spectrometry techniques. The mass spectrometry-based snake venomics approach revealed that more than half of the venom is composed of different phospholipases A2 (PLA₂). The combination of this approach and an intact mass profiling led to the identification of the three main Habu PLA₂s. Furthermore, nearly one-third of the total venom consists of snake venom metalloproteinases and disintegrins, and several minor represented toxin families were detected: C-type lectin-like proteins (CTL), cysteine-rich secretory proteins (CRISP), snake venom serine proteases (svSP), l-amino acid oxidases (LAAO), phosphodiesterase (PDE) and 5'-nucleotidase. Finally, the venom of P. flavoviridis contains certain bradykinin-potentiating peptides and related peptides, like the svMP inhibitors, pEKW, pEQW, pEEW and pENW. In preliminary MTT cytotoxicity assays, the highest cancerous-cytotoxicity of crude venom was measured against human neuroblastoma SH-SY5Y cells and shows disintegrin-like effects in some fractions.

Toxin-resolved antivenomics-guided assessment of the immunorecognition landscape of antivenoms

Snakebite envenoming represents a major issue in rural areas of tropical and subtropical regions across sub-Saharan Africa, South to Southeast Asia, Latin America and Oceania. Antivenoms constitute the only scientifically validated therapy for snakebite envenomings, provided they are safe, effective, affordable, accessible and administered appropriately. However, the lack of financial incentives in a technology that has remained relatively unchanged for more than a century, has contributed to some manufacturers leaving the market and others downscaling production or increasing the prices, leading to a decline in the availability and accessibility for these life-saving antidotes to millions of rural poor most at risk from snakebites in low income countries. The shortage of antivenoms can be significantly alleviated by optimizing the use of current antivenoms (through the assessment of their specific and paraspecific efficacy against the different medically relevant homologous and heterologous snake venoms) and by generating novel polyspecific antivenoms exhibiting broad clinical spectrum and wide geographic distribution range. Research on venoms has been continuously enhanced by advances in technology. Particularly, the last decade has witnessed the development of omics strategies for unravelling the toxin composition of venoms ("venomics") and to assess the immunorecognition profile of antivenoms ("antivenomics"). Here, we review recent developments and reflect on near future innovations that promise to revolutionize the mutually enlightening relationship between evolutionary and translational venomics.

Identification of Immunoreactive Peptides of Toxins to Simultaneously Assess the Neutralization Potency of Antivenoms against Neurotoxicity and Cytotoxicity of Naja atra Venom

Assessing the neutralization capability of nonlethal but medically relevant toxins in venom has been a challenging task. Nowadays, neutralization efficacy is evaluated based simply on the survival rates of animals injected with antivenom together with a predefined dose of venom, which can determine potency against neurotoxicity but not validate the capability to neutralize cytotoxin-induced complications. In this study, a high correlation with in-vivo and in-vitro neutralization assays was established using the immunoreactive peptides identified from short-chain neurotoxin and cytotoxin A3. These peptides contain conserved residues associated with toxin activities and a competition assay indicated that these peptides could specifically block the antibody binding to toxin and affect the neutralization potency of antivenom. Moreover, the titers of peptide-specific antibody in antivenoms or mouse antisera were determined by enzyme-linked immunosorbent assay (ELISA) simultaneously, and the results indicated that Taiwanese bivalent antivenom (BAV) and Vietnamese snake antivenom-Naja (SAV-Naja) exhibited superior neutralization potency against the lethal effect of short-chain neurotoxin (sNTX) and cytotoxicity of cardiotoxin/cytotoxin (CTX), respectively. Thus, the reported peptide ELISA shows not only its potential for antivenom prequalification use, but also its capability of justifying the cross-neutralization potency of antivenoms against Naja atra venom toxicity.

Comparative analyses of putative toxin gene homologs from an Old World viper, Daboia russelii

Availability of snake genome sequences has opened up exciting areas of research on comparative genomics and gene diversity. One of the challenges in studying snake genomes is the acquisition of biological material from live animals, especially from the venomous ones, making the process cumbersome and time-consuming. Here, we report comparative sequence analyses of putative toxin gene homologs from Russell’s viper (Daboia russelii) using whole-genome sequencing data obtained from shed skin. When compared with the major venom proteins in Russell’s viper studied previously, we found 45–100% sequence similarity between the venom proteins and their putative homologs in the skin. Additionally, comparative analyses of 20 putative toxin gene family homologs provided evidence of unique sequence motifs in nerve growth factor (NGF), platelet derived growth factor (PDGF), Kunitz/Bovine pancreatic trypsin inhibitor (Kunitz BPTI), cysteine-rich secretory proteins, antigen 5, andpathogenesis-related1 proteins (CAP) and cysteine-rich secretory protein (CRISP). In those derived proteins, we identified V11 and T35 in the NGF domain; F23 and A29 in the PDGF domain; N69, K2 and A5 in the CAP domain; and Q17 in the CRISP domain to be responsible for differences in the largest pockets across the protein domain structures in crotalines, viperines and elapids from the in silico structure-based analysis. Similarly, residues F10, Y11 and E20 appear to play an important role in the protein structures across the kunitz protein domain of viperids and elapids. Our study highlights the usefulness of shed skin in obtaining good quality high-molecular weight DNA for comparative genomic studies, and provides evidence towards the unique features and evolution of putative venom gene homologs in vipers.

Contributing Factors for Complications and Outcomes in Patients With Snakebite: Experience in a Medical Center in Southern Taiwan

OBJECTIVES

Snakebite usually results in various complications, such as significant soft tissue damage, infection, hematological, and neurological deficit. Surgical intervention, usually, is indicated in patients with tissue necrosis, infection, and compartment syndrome. To identify the contributing factors for complications and outcomes in different patients with snakebite so that outcomes can be evaluated and treatment of such patients can be initiated at the earliest.

METHODS

Information was collected regarding age, sex, underlying disease, species of snake, and the course of treatment of the victims of snakebite who visited the emergency department of a medical center in southern Taiwan between 2004 and 2014. The data obtained were analyzed using SPSS 20.0.

RESULTS

The bites from Taiwan cobra (Naja naja atra) significantly resulted in more complications than those from other snakes and required surgical intervention. The use of antivenin and antibiotics, immediate presentation to the hospital, and the location of the bite also were significant contributing factors.

CONCLUSIONS

Taiwan cobra significantly results in higher possibility of prolonged hospitalization, operation, tissue necrosis, infection, and necrotizing fasciitis. Location of the bite, immediate presentation to the hospital, and use of antivenin and antibiotics affect the outcome of snakebite. Knowledge of these factors will help in a better management of patients with snakebite.

A Review and Database of Snake Venom Proteomes

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

Preclinical Evaluation of the Efficacy of Antivenoms for Snakebite Envenoming: State-of-the-Art and Challenges Ahead

Animal-derived antivenoms constitute the mainstay in the therapy of snakebite envenoming. The efficacy of antivenoms to neutralize toxicity of medically-relevant snake venoms has to be demonstrated through meticulous preclinical testing before their introduction into the clinical setting. The gold standard in the preclinical assessment and quality control of antivenoms is the neutralization of venom-induced lethality. In addition, depending on the pathophysiological profile of snake venoms, the neutralization of other toxic activities has to be evaluated, such as hemorrhagic, myotoxic, edema-forming, dermonecrotic, in vitro coagulant, and defibrinogenating effects. There is a need to develop laboratory assays to evaluate neutralization of other relevant venom activities. The concept of the 3Rs (Replacement, Reduction, and Refinement) in Toxinology is of utmost importance, and some advances have been performed in their implementation. A significant leap forward in the study of the immunological reactivity of antivenoms against venoms has been the development of “antivenomics”, which brings the analytical power of mass spectrometry to the evaluation of antivenoms. International partnerships are required to assess the preclinical efficacy of antivenoms against snake venoms in different regions of the world in order to have a detailed knowledge on the neutralizing profile of these immunotherapeutics.

Strategies in 'snake venomics' aiming at an integrative view of compositional, functional, and immunological characteristics of venoms

This work offers a general overview on the evolving strategies for the proteomic analysis of snake venoms, and discusses how these may be combined through diverse experimental approaches with the goal of achieving a more comprehensive knowledge on the compositional, toxic, and immunological characteristics of venoms. Some recent developments in this field are summarized, highlighting how strategies have evolved from the mere cataloguing of venom components (proteomics/venomics), to a broader exploration of their immunological (antivenomics) and functional (toxicovenomics) characteristics. Altogether, the combination of these complementary strategies is helping to build a wider, more integrative view of the life-threatening protein cocktails produced by venomous snakes, responsible for thousands of deaths every year.

Envenoming by Viridovipera stejnegeri snake: a patient with liver cirrhosis presenting disruption of hemostatic balance

Background

In most cases of envenoming by the green habu Viridovipera stejnegeri in Taiwan coagulopathy is not observed.

Case presentation

Herein, we describe the case of a patient with liver cirrhosis who developed venom-induced consumptive coagulopathy after V. stejnegeri bite. Laboratory investigation revealed the following: prothrombin time > 100 s (international normalized ratio > 10), activated partial thromboplastin time > 100 s, fibrinogen < 50 mg/dL, and fibrin degradation product > 80 μg/mL. The patient recovered after administration of bivalent hemorrhagic antivenom, vitamin K, fresh frozen plasma and cryoprecipitate.

Conclusion

The liver, directly involved in the acute phase reaction, is the main responsible for neutralization of animal toxins. Any patient with history of liver cirrhosis bitten by a venomous snake, even those whose venoms present low risk of coagulopathy, should be very carefully monitored for venom-induced consumptive coagulopathy (VICC), since the hemostatic balance may be disrupted.