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The Russell's viper (Daboia siamensis) is a medically important venomous snake in Myanmar. Next-generation sequencing (NGS) shows potential to investigate the venom complexity, giving deeper insights into snakebite pathogenesis and possible drug discoveries. mRNA from venom gland tissue was extracted and sequenced on the Illumina HiSeq platform and de novo assembled by Trinity. The candidate toxin genes were identified via the Venomix pipeline. Protein sequences of identified toxin candidates were compared with the previously described venom proteins using Clustal Omega to assess the positional homology among candidates. Candidate venom transcripts were classified into 23 toxin gene families including 53 unique full-length transcripts. C-type lectins (CTLs) were the most highly expressed, followed by Kunitz-type serine protease inhibitors, disintegrins and Bradykinin potentiating peptide/C-type natriuretic peptide (BPP-CNP) precursors. Phospholipase A2, snake venom serine proteases, metalloproteinases, vascular endothelial growth factors, L-amino acid oxidases and cysteine-rich secretory proteins were under-represented within the transcriptomes. Several isoforms of transcripts which had not been previously reported in this species were discovered and described. Myanmar Russell's viper venom glands displayed unique sex-specific transcriptome profiles which were correlated with clinical manifestation of envenoming. Our results show that NGS is a useful tool to comprehensively examine understudied venomous snakes. [ABSTRACT FROM AUTHOR]

The venom of the Russell's viper (Daboia siamensis) contains neurotoxic and myotoxic phospholipase A2 toxins which can cause irreversible damage to motor nerve terminals. Due to the time delay between envenoming and antivenom administration, antivenoms may have limited efficacy against some of these venom components. Hence, there is a need for adjunct treatments to circumvent these limitations. In this study, we examined the efficacy of Chinese D. siamensis antivenom alone, and in combination with a PLA2 inhibitor, Varespladib, in reversing the in vitro neuromuscular blockade in the chick biventer cervicis nerve-muscle preparation. Pre-synaptic neurotoxicity and myotoxicity were not reversed by the addition of Chinese D. siamensis antivenom 30 or 60 min after venom (10 µg/mL). The prior addition of Varespladib prevented the neurotoxic and myotoxic activity of venom (10 µg/mL) and was also able to prevent further reductions in neuromuscular block and muscle twitches when added 60 min after venom. The addition of the combination of Varespladib and antivenom 60 min after venom failed to produce further improvements than Varespladib alone. This demonstrates that the window of time in which antivenom remains effective is relatively short compared to Varespladib and small-molecule inhibitors may be effective in abrogating some activities of Chinese D. siamensis venom. [ABSTRACT FROM AUTHOR]

Daboia siamensis (Russell's viper) is a highly venomous and medically important snake in China, as well as much of Asia. There is minimal information on the pharmacological activity of the venom of the Chinese species, and currently no commercially available specific antivenom in China. This has led to the use of non-specific antivenoms to treat D. siamensis envenomation. In this study, the in vitro neurotoxicity and myotoxicity of D. siamensis venom was examined and the efficacy of four antivenoms was investigated, including the recently developed Chinese D. siamensis monovalent antivenom (C-DsMAV) and three commercially available antivenoms (Thai D. siamensis (Thai-DsMAV) monovalent antivenom, Deinagkistrodon acutus monovalent antivenom (DaAV), and Gloydius brevicaudus monovalent antivenom (GbAV). D. siamensis venom (10–30 µg/mL) caused the concentration-dependent inhibition of indirect twitches in the chick biventer cervicis nerve muscle preparation, without abolishing contractile responses to exogenous agonists ACh or CCh, indicating pre-synaptic neurotoxicity. Myotoxicity was also evident at these concentrations with inhibition of direct twitches, an increase in baseline tension, and the partial inhibition of ACh, CCh, and KCl responses. The prior addition of C-DsMAV or Thai-DsMAV prevented the neurotoxic and myotoxic activity of D. siamensis venom (10 µg/mL). The addition of non-specific antivenoms (GbAV and DaAV) partially prevented the neurotoxic activity of venom (10 µg/mL) but failed to neutralize the myotoxic effects. We have shown that D. siamensis venom exhibits in vitro weak presynaptic neurotoxicity and myotoxicity, which can be prevented by the pre-addition of the Chinese and Thai Russell's viper antivenoms. Non-specific antivenoms were poorly efficacious. There should be further development of a monospecific antivenom against D. siamensis envenomation in China. [ABSTRACT FROM AUTHOR]

Abstract Background: Eastern Russell’s viper (Daboia siamensis) is one of the most medically significant snakes responsible for the development of acute renal failure. However, variation of the clinical picture and renal pathophysiology following bites by young and adult D. siamensis have not been elucidated. Methods: In this study, we analyzed the venomic profiles of D. siamensis at different maturation stages of juvenile, subadult and adult groups. The same pooled venom from each group was subjected to enzymatic, electrophoretic and proteomic analysis, including sublethal toxicity (0.1 mg/kg iv.) examined on bodily functions by comparing the venom compositional and functional profiles among venom specimens from juvenile, subadult and adult D. siamensis by correlating them with the renal pathophysiology in experimental rabbits. Results: The comparative studies revealed that juvenile venom possessed higher phospholipase A2, metalloproteinase and serine proteinase levels, while subadult and adult venoms contained more L-amino acid oxidase, phosphodiesterase, the Kunitz-type serine protease inhibitor, disintegrin families and endothelial growth factor. An in vivo study revealed that the adult and subadult venoms caused persistent hypotension and bradycardia, while thrombocytopenia was a more characteristic effect of juvenile venom. All venom age groups showed significant reductions in renal hemodynamics and electrolyte excretions. The juvenile venom caused a higher tubulonephrosis lesion score than adult and subadult venoms. Conclusions: The D. siamensis venom shows an ontogenetic shift in its compositions and activities. Renal function alterations after envenomation depend on either the synergistic actions of different venom components or the disproportionate expression between the concentrations of enzymatic and non-enzymatic proteins in each age venom group. The high proportion of enzymatic toxin proteins in the juvenile venom results in greater nephrotoxicity.

Abstract Background There are 6 species of venomous snakes in Taiwan. Two of them, Deinagkistrodon acutus (D. acutus) and Daboia siamensis (D. siamensis), can cause significant coagulopathy. However, a significant proportion of patients with snakebites cannot identify the correct snake species after envenomation, which hampers the application of antivenom. Hence, the differential diagnosis between the two snakebites by clinical presentations is important. This study aims to compare their clinical and laboratory features for the purpose of differential diagnosis between the two snakebites. Methods We retrospectively reviewed the medical records of patients who arrived at the emergency department due to D. acutus or D. siamensis envenomation, between 2003 and 2016, in one medical center in eastern Taiwan. Since these snakebites are rare, we also included 3 cases reported from another hospital in central Taiwan. Results In total, 15 patients bitten by D. acutus and 12 patients by D. siamensis were analyzed. Hemorrhagic bulla formation and the need for surgical intervention only presented for D. acutus envenomation cases (Both 53.3% vs. 0.0%, P = 0.003). As to laboratory features, lower platelet counts (20.0 × 103/μL [interquartile range, 14–66 × 103/μL] vs. 149.0 × 103/μL [102.3–274.3 × 103/μL], P = 0.001), lower D-dimer level (1423.4 μg/L [713.4–4212.3 μg/L] vs. 12,500.0 μg/L [2351.4–200,000 μg/L], P = 0.008), higher proportion of patients with moderate-to-severe thrombocytopenia (platelet count 5000 ng/mL) (16.7% vs. 66.7%, adjusted OR = 0.1 (95% CI, 0.01–0.69; P = 0.036) were found among cases of D. acutus envenomation compared to D. siamensis envenomation. The combination of hemorrhagic bulla, thrombocytopenia, and a lack of extremely high D-dimer had good discriminatory power (area under the curve (AUC) = 0.965; 95% CI, 0.904–1.00) for distinguishing D. acutus from D. siamensis envenomation. Conclusions The presentation of moderate to severe thrombocytopenia (platelet count

Snakebite envenoming is a serious problem in Myanmar. The great majority of snakebite in this country is due to Russell's Viper ( Daboia siamensis ). For many years, the Burma Pharmaceutical Industry has produced a monovalent antivenom to Russell's Viper in horses. At present, the only way of determining the level of antibody against D. siamensis venom in hyperimmune horse serum is to perform venom neutralisation tests in mice. In this study, we describe the development of an in vitro ELISA assay to estimate neutralising capacity of horse serum. We found a strong correlation between the ELISA assay and the venom neutralisation test in mice (r = 0.982). The assay is robust and has sufficient sensitivity (92%) and specificity (96%) to replace the venom neutralisation test in mice during the immunisation phase in horses. [ABSTRACT FROM AUTHOR]

Daboia siamensis monovalent antivenom (DSMAV, Thailand) exhibited comparable immunoreactivity toward the venoms of eastern Russell's vipers from Thailand and Indonesia. It also effectively neutralized the procoagulant and lethal effects of both venoms, showing high potency. The Indonesian heterologous trivalent antivenom SABU (Serum Anti Bisa Ular), however, has very weak immunoreactivity and it failed to neutralize the Russell's viper venoms. DSMAV appears to be the appropriate choice of antivenom to treat Russell's viper envenoming. Image 1 • Daboia siamensis monovalent antivenom (DSMAV, Thailand) was examined. • DSMAV is immunoreactive toward Russell's viper venom from Indonesia. • It effectively neutralized the procoagulant and lethal effects of the venom. • The Indonesian heterologous trivalent antivenom SABU is not effective. • DSMAV may be the appropriate treatment in the Indonesian scenario. [ABSTRACT FROM AUTHOR]

The venom proteome of Siamese Russell’s viper from Taiwan, alongside complementary in vivo lethality neutralization assay and in vitro third-generation antivenomics assessment of the preclinical efficacy of the homologous antivenom manufactured in Taiwan CDC’s Vaccine Center, are here reported. Taiwanese Russell’s viper venom proteome comprised 25 distinct gene products, with the heterodimeric PLA2 viperotoxin-F representing the most abundant toxin (47.5% of total venom proteome). Coagulation FV-activating serine proteinase (RVV-V, 14%), the PIV-SVMP activator of FX (RVV-FX, 8.5%), and less abundant toxins from nine protein families, make up its venom proteome. Venom composition-pathology correlations of D. siamensis envenomings in Taiwan are discussed. The lethal effect of Taiwanese D. siamensis venom was 0.47 mg/g mouse. Antivenomics-guided assessment of the toxin recognition landscape of the Taiwanese Russell’s viper antivenom, in conjunction with complementary in vivo neutralization analysis, informed the antivenom’s maximal toxin immunorecognition ability (14 mg total venom proteins/vial), neutralization capacity (6.5 mg venom/vial), and relative content of lethality neutralizing antibodies (46.5% of the toxin-binding F(ab’)2 antibodies). The antigenomic analysis also revealed suboptimal aspects of the CDC-Taiwan antivenom. Strategies to improve them are suggested.

Summary: Our environment hosts a vast diversity of venomous and poisonous animals and plants. Clinical toxinology is devoted to understanding, preventing and treating their effects in humans and domestic animals. In Sri Lanka, yellow oleander (Thevetia peruviana, Sinhala ‘kaneru’), a widespread and accessible ornamental shrub, is a popular means of self-harm. Its toxic glycosides resemble those of foxglove, against which therapeutic antibodies have been raised. A randomised placebo-controlled trial proved that this treatment effectively reversed kaneru cardiotoxicity. There are strong scientific grounds for the use of activated charcoal, but encouraging results with multiple-dose activated charcoal were not confirmed by a recent more powerful study. Venom of Russell''s viper (Daboia siamensis) in Burma (Myanmar) produces lethal effects in human victims. The case of a 17-year-old rice farmer is described with pathophysiological interpretations. During the first 9 days of hospital admission he suffered episodes of shock, coagulopathy, bleeding, acute renal failure, local tissue necrosis, generally increased capillary permeability and acute symptomatic hypoglycaemia with evidence of acute pituitary/adrenal insufficiency. Antivenom rapidly restored haemostatic function but failed to correct other effects of venom toxins incurred during the 3h before he could be treated. [Copyright &y& Elsevier]

Abstract: Two homologous P-III hemorrhagic metalloproteinases were purified from Russell''s viper venoms from Myanmar and Kolkata (eastern India), and designated as daborhagin-M and daborhagin-K, respectively. They induced severe dermal hemorrhage in mice at a minimum hemorrhagic dose of 0.8–0.9μg. Daborhagin-M specifically hydrolyzed an Aα-chain of fibrinogen, fibronectin, and type IV collagen in vitro. Analyses of its cleavage sites on insulin chain B and kinetic specificities toward oligopeptides suggested that daborhagin-M prefers hydrophobic residues at the P1, P1′, and P2′ positions on the substrates. Of the eight Daboia geographic venom samples analyzed by Western blotting, only those from Myanmar and eastern India showed a strong positive band at 65kDa, which correlated with the high risk of systemic hemorrhagic symptoms elicited by Daboia envenoming in both regions. The full sequence of daborhagin-K was determined by cDNA cloning and sequencing, and then confirmed by peptide mass fingerprinting. Furthermore, molecular phylogenetic analyses based on 27 P-IIIs revealed the co-evolution of two major P-III classes with distinct hemorrhagic potencies, and daborhagin-K belongs to the most hemorrhagic subclass. By comparing the absolute complexity profiles between these two classes, we identified four structural motifs probably responsible for the phylogenetic subtyping and hemorrhagic potencies of P-III SVMPs. [Copyright &y& Elsevier]

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