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Snake venoms comprise a highly complex mixture of proteins, and there is also a high interspecific and intraspecific variability in their composition, even in the same region. Our aim was to compare the composition of the venoms of Bothrocophias myersi, Crotalus durissus and Bothrops asper, snakes from the Andean region in Colombia by Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC). The venoms were given to the research group under an agreement with the Fundación Zoológica de Cali. The venoms pool was obtained by manual extraction, lyophilized and refrigerated. The protein found in the venoms was quantified by spectrophotometry using the Bradford and Lowry methods and direct measurement by Nanodrop®. The protein composition was stablished by RP-HPLC, using a Lichosper 100 RP, C18 column (250X4 mm) with a pore size of 5µm, as well as by Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE). The highest quantity of protein was found in the venom of B. myersi (108,6 mg/mL) followed by C. durissus (78,1 mg/mL) and B. asper (74.1 mg/mL). All venoms showed bands of 15 and 50 KDa by SDS-PAGE; The most important finding is the abundance of PLA2 and svMP in the venom of B. myersi. Chromatographic analyses revealed a very similar venom composition profile, but also certain differences in toxins abundance. We conclude that the process of separating the venom proteins by RP-HPLC and SDS-PAGE are very important as a first step to know the venoms profiles, which in turn could allow medical staff to elucidate the clinical syndrome produced by snakebites.

HighlightsSnakebites are a major public health concern, impacting millions of lives in rural areas globally. Obtaining animal-derived antivenom treatment immediately after sustaining a snakebite is challenging due to various practical difficulties in rural areas. We developed mRNA-lipid nanoparticles (LNPs) to express and deliver single-chain variable fragments (scFvs) of antibodies against a venom myotoxin and tested their efficacy in preventing myotoxin and venom-induced muscle damage in vitro and in vivo. Delivery of the mRNA-LNPs led to expression of scFvs after a time delay, which protected against myotoxin and venom-induced muscle damage in mice.

Improved therapies are needed against snakebite envenoming, which kills and permanently disables thousands of people each year. Recently developed neutralizing monoclonal antibodies against several snake toxins have shown promise in preclinical rodent models. Here, we use phage display technology to discover a human monoclonal antibody and show that this antibody causes antibody-dependent enhancement of toxicity (ADET) of myotoxin II from the venomous pit viper, Bothrops asper , in a mouse model of envenoming that mimics a snakebite. While clinical ADET related to snake venom has not yet been reported in humans, this report of ADET of a toxin from the animal kingdom highlights the necessity of assessing even well-known antibody formats in representative preclinical models to evaluate their therapeutic utility against toxins or venoms. This is essential to avoid potential deleterious effects as exemplified in the present study. The recent emergence of monoclonal antibodies able to neutralize snake toxins have revolutionized the approach of developing novel therapies to treat snakebite envenoming, at least in animal models. Here, the authors show antibody-dependent enhancement of toxicity (ADET) for a toxin derived from snake venom and highlight the importance of this phenomenon when testing therapeutic antibodies against snake venoms in animal models.

Lance-headed snakes are found in Central and South America, and they account for most snakebites in Brazil. The phylogeny of South American pitvipers has been reviewed, and the presence of natural and non-natural hybrids between different species of Bothrops snakes demonstrates that reproductive isolation of several species is still incomplete. The present study aimed to analyze the biological features, particularly the thrombin-like activity, of venoms from hybrids born in captivity, from the mating of a female Bothrops erythromelas and a male Bothrops neuwiedi, two species whose venoms are known to display ontogenetic variation. Proteolytic activity on azocoll and amidolytic activity on N-benzoyl-DL-arginine-p-nitroanilide hydrochloride (BAPNA) were lowest when hybrids were 3 months old, and increased over body growth, reaching values similar to those of the father when hybrids were 12 months old. The clotting activity on plasma diminished as hybrids grew; venoms from 3- and 6-months old hybrids showed low clotting activity on fibrinogen (i.e., thrombin-like activity), like the mother venom, and such activity was detected only when hybrids were older than 1 year of age. Altogether, these results point out that venom features in hybrid snakes are genetically controlled during the ontogenetic development. Despite the presence of the thrombin-like enzyme gene(s) in hybrid snakes, they are silenced during the first six months of life.

The uplift and final connection of the Central American land bridge is considered the major event that allowed biotic exchange between vertebrate lineages of northern and southern origin in the New World. However, given the complex tectonics that shaped Middle America, there is still substantial controversy over details of this geographical reconnection, and its role in determining biogeographic patterns in the region. Here, we examine the phylogeography of Bothrops asper, a widely distributed pitviper in Middle America and northwestern South America, in an attempt to evaluate how the final Isthmian uplift and other biogeographical boundaries in the region influenced genealogical lineage divergence in this species. We examined sequence data from two mitochondrial genes (MT-CYB and MT-ND4) from 111 specimens of B. asper, representing 70 localities throughout the species' distribution. We reconstructed phylogeographic patterns using maximum likelihood and Bayesian methods and estimated divergence time using the Bayesian relaxed clock method. Within the nominal species, an early split led to two divergent lineages of B. asper: one includes five phylogroups distributed in Caribbean Middle America and southwestern Ecuador, and the other comprises five other groups scattered in the Pacific slope of Isthmian Central America and northwestern South America. Our results provide evidence of a complex transition that involves at least two dispersal events into Middle America during the final closure of the Isthmus.

Snakebite is a neglected tropical disease that causes extensive mortality and morbidity in rural communities. Antivenim sera are the currently approved therapy for snake bites; however, they have some therapeutic limitations that have been extensively documented. Recently, small molecule toxin inhibitors have received significant attention as potential alternatives or co-adjuvant to immunoglobulin-based snakebite therapies. Thus, in this study, we evaluated the inhibitory effects of the phospholipase A2 inhibitor varespladib and the metalloproteinase inhibitor CP471474 and their synergistic effects on the lethal, edema-forming, hemorrhagic, and myotoxic activities of Bothrops asper and Crotalus durissus cumanensis venoms from Colombia. Except for the preincubation assay of the lethal activity with B. asper venom, the mixture showed the best inhibitory activity. Nevertheless, the mix did not display statistically significant differences to varespladib and CP471474 used separately in all assays. In preincubation assays, varespladib showed the best inhibitory activity against the lethal effect induced by B. asper venom. However, in independent injection assays, the mix of the compounds partially inhibited the lethal activity of both venoms (50%). In addition, in the assays to test the inhibition of edema-forming activity, the mixture exhibited the best inhibitory activity, followed by Varespladib, but without statistically significant differences (p > 0.05). The combination also decreased the myotoxic activity of evaluated venoms. In these assays, the mix showed statistical differences regarding CP471474 (p < 0.05). The mixture also abolished the hemorrhagic activity of B. asper venom in preincubation assays, with no statistical differences to CP471474. Finally, the mixture showed inhibition in studies with independent administration in a time-dependent manner. To propose a mode of action of varespladib and CP471474, molecular docking was performed. PLA2s and SVMPs from tested venoms were used as targets. In all cases, our molecular modeling results suggested that inhibitors may occupy the substrate-binding cleft of the enzymes, which was supported by specific interaction with amino acids from the active site, such as His48 for PLA2s and Glu143 for the metalloproteinase. In addition, varespladib and CP471474 also showed interaction with residues from the hydrophobic channel in PLA2s and substrate binding subsites in the SVMP. Our results suggest a synergistic action of the mixed inhibitors and show the potential of varespladib, CP471474, and their mixture to generate new treatments for snakebite envenoming with application in the field or as antivenom co-adjuvants.

Two subtypes of phospholipases A2 (PLA2s) with the ability to induce myonecrosis, 'Asp49' and 'Lys49' myotoxins, often coexist in viperid snake venoms. Since the latter lack catalytic activity, two different mechanisms are involved in their myotoxicity. A synergism between Asp49 and Lys49 myotoxins from Bothrops asper was previously observed in vitro, enhancing Ca2+ entry and cell death when acting together upon C2C12 myotubes. These observations are extended for the first time in vivo, by demonstrating a clear enhancement of myonecrosis by the combined action of these two toxins in mice. In addition, novel aspects of their synergism were revealed using myotubes. Proportions of Asp49 myotoxin as low as 0.1% of the Lys49 myotoxin are sufficient to enhance cytotoxicity of the latter, but not the opposite. Sublytic amounts of Asp49 myotoxin also enhanced cytotoxicity of a synthetic peptide encompassing the toxic region of Lys49 myotoxin. Asp49 myotoxin rendered myotubes more susceptible to osmotic lysis, whereas Lys49 myotoxin did not. In contrast to myotoxic Asp49 PLA2, an acidic non-toxic PLA2 from the same venom did not markedly synergize with Lys49 myotoxin, revealing a functional difference between basic and acidic PLA2 enzymes. It is suggested that Asp49 myotoxins synergize with Lys49 myotoxins by virtue of their PLA2 activity. In addition to the membrane-destabilizing effect of this activity, Asp49 myotoxins may generate anionic patches of hydrolytic reaction products, facilitating electrostatic interactions with Lys49 myotoxins. These data provide new evidence for the evolutionary adaptive value of the two subtypes of PLA2 myotoxins acting synergistically in viperid venoms.

The protein profile of Bothrops rhombeatus venom was compared to Bothrops asper and Bothrops atrox, and the effectiveness of antivenoms from the National Institute of Health of Colombia (INS) and Antivipmyn-Tri (AVP-T) of Mexico were analyzed. Protein profiles were studied with sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and reverse-phase high-performance liquid chromatography (RP-HPLC). The neutralizing potency and the level of immunochemical recognition of the antivenoms to the venoms were determined using Western blot, affinity chromatography, and enzyme-linked immunosorbent assay (ELISA). Bands of phospholipase A2 (PLA2), metalloproteinases (svMPs) I, II, and III as well as serine proteinases (SPs) in the venom of B. rhombeatus were recognized by SDS-PAGE. With Western blot, both antivenoms showed immunochemical recognition towards PLA2 and svMP. INS showed 94% binding to B. rhombeatus venom and 92% to B. asper while AVP-T showed 90.4% binding to B. rhombeatus venom and 96.6% to B. asper. Both antivenoms showed binding to PLA2 and svMP, with greater specificity of AVP-T towards B. rhombeatus. Antivenom neutralizing capacity was calculated by species and mL of antivenom, finding the following for INS: B. asper 6.6 mgV/mL, B. atrox 5.5 mgV/mL, and B. rhombeatus 1.3 mgV/mL. Meanwhile, for AVP-T, the following neutralizing capacities were found: B. asper 2.7 mgV/mL, B. atrox 2.1 mgV/mL, and B. rhombeatus 1.4 mgV/mL. These results show that both antivenoms presented similarity between calculated neutralizing capacities in our trial, reported in a product summary for the public for the B. asper species; however, this does not apply to the other species tested in this trial.

Myonecrosis is a frequent clinical manifestation of envenomings by Viperidae snakes, mainly caused by the toxic actions of secreted phospholipase A2 (sPLA2) enzymes and sPLA2-like homologs on skeletal muscle fibers. A hallmark of the necrotic process induced by these myotoxins is the rapid appearance of hypercontracted muscle fibers, attributed to the massive influx of Ca2+ resulting from cell membrane damage. However, the possibility of myotoxins having, in addition, a direct effect on the contractile machinery of skeletal muscle fibers when internalized has not been investigated. This question is here addressed by using an ex vivo model of single-skinned muscle fibers, which lack membranes but retain an intact contractile apparatus. Rabbit psoas skinned fibers were exposed to two types of myotoxins of Bothrops asper venom: Mt-I, a catalytically active Asp49 sPLA2 enzyme, and Mt-II, a Lys49 sPLA2-like protein devoid of phospholipolytic activity. Neither of these myotoxins affected the main parameters of force development in striated muscle sarcomeres of the skinned fibers. Moreover, no microscopical alterations were evidenced after their exposure to Mt-I or Mt-II. In contrast to the lack of effects on skinned muscle fibers, both myotoxins induced a strong hypercontraction in myotubes differentiated from murine C2C12 myoblasts, with drastic morphological alterations that reproduce those described in myonecrotic tissue in vivo. As neither Mt-I nor Mt-II showed direct effects upon the contractile apparatus of skinned fibers, it is concluded that the mechanism of hypercontraction triggered by both myotoxins in patients involves indirect effects, i.e., the large cytosolic Ca2+ increase after sarcolemma permeabilization.

Previous proteomic studies of viperid venom revealed that it is mainly composed of metalloproteinases (SVMPs), serine proteinases (SVSPs), phospholipase A2 (PLA2), and C-type lectins (CTLs). However, other proteins appear in minor amounts that affect prey and need to be identified. This study aimed to identify novel toxic proteins in the venom gland transcriptome of Bothrops asper and Bothrops jararaca, using data from NCBI. Bioinformatics tools were used to assemble, identify, and compare potentially novel proteins in both species, and we performed functional annotation with BLASTX against the NR database. While previous assemblies have been performed for B. jararaca, this is the first assembly of the B. asper venom gland transcriptome. Proteins with potentially novel functions were identified, including arylsulfatase and dihydroorotate dehydrogenase, among others, that could have implications for venom toxicity. These results suggest that the identified proteins may contribute to venom toxic variation and provide new opportunities for antivenom research. The study improves the understanding of the protein composition of Bothrops venom and suggests new possibilities for the development of treatments and antivenoms.