Pharmacological characterization and neutralization of the venoms used in the production of Bothropic antivenom in Brazil

Effect of Seaweed-Derived Fucoidans from Undaria pinnatifida and Fucus vesiculosus on Coagulant, Proteolytic, and Phospholipase A2 Activities of Snake Bothrops jararaca, B. jararacussu, and B. neuwiedi Venom

BACKGROUND

Snakebite envenomation (SBE) causes diverse toxic effects in humans, including disability and death. Current antivenom therapies effectively prevent death but fail to block local tissue damage, leading to an increase in the severity of envenomation; thus, seeking alternative treatments is crucial.

METHODS

This study analyzed the potential of two fucoidan sulfated polysaccharides extracted from brown seaweeds Fucus vesiculosus (FVF) and Undaria pinnatifida (UPF) against the fibrinogen or plasma coagulation, proteolytic, and phospholipase A2 (PLA2) activities of Bothrops jararaca, B. jararacussu, and B. neuwiedi venom. The toxicity of FVF and UPF was assessed by the hemocompatibility test.

RESULTS

FVF and UPF did not lyse human red blood cells. FVF and UPF inhibited the proteolytic activity of Bothrops jararaca, B. jararacussu, and B. neuwiedi venom by approximately 25%, 50%, and 75%, respectively, while all venoms led to a 20% inhibition of PLA2 activity. UPF and FVF delayed plasma coagulation caused by the venoms of B. jararaca and B. neuwiedi but did not affect the activity of B. jararacussu venom. FVF and UPF blocked the coagulation of fibrinogen induced by all these Bothropic venoms.

CONCLUSION

FVF and UPF may be of importance as adjuvants for SBE caused by species of Bothrops, which are the most medically relevant snakebite incidents in South America, especially Brazil.

Evaluation of the properties of Bungarus caeruleus venom and checking the efficacy of antivenom used in Bangladesh for its bite treatment

As a disaster-prone country with unique geographical features, snake biting is a major public health concern in Bangladesh. The primary reasons of mortality from snakebite include late presentation to the hospital, low efficacy of antivenom, and a lack of adequate management facilities. Because snake venom characteristics vary depending on geographical location, antivenom should be manufactured from snakes native to the region in which it would be administered. Bungarus caeruleus is a highly venomous snake contributing to the major snakebite issue in Bangladesh. Therefore, the neutralization efficacy of the antivenom against B. caeruleus venom was evaluated in the current study along with the characterization of venom. For biological characterization of venom, RP-HPLC and SDS-PAGE profiling, hemolytic activity, hemorrhagic activity, phospholipases A₂ (PLA₂) activity, edema inducing activity and histopathological observations were carried out following standard protocol. LD₅₀ of the venom was calculated along with neutralization potency of Incepta antivenom through probit analysis. Results showed that venom possesses phospholipase A₂ activity, hemolytic activity and edema inducing activity while hemorrhagic activity was absent in the skin of envenomed mice. Histopathological alterations including necrosis, congestion and infiltrations were observed in envenomed mice organs after hematoxylin and eosin staining. Neutralization study showed that Incepta polyvalent antivenom could neutralize (potency 0.53 mg/ml) the lethal effect in in vitro study on mice. Further investigation on snakebite epidemiology and clinical observations of the envenomed patients will help in combating the snakebite problem more efficiently.

Production of a murine mAb against Bothrops alternatus and B. neuwiedi snake venoms and its use to isolate a thrombin-like serine protease fraction

Accidents with snakes from the genus Bothrops represent ~90 % of all snakebites in Brazil. Monoclonal antibodies (mAbs) targeting venom components can be important assets for treating envenoming syndromes, for developing diagnostic tests and for research purposes. Therefore, in this study, we aimed to generate murine mAbs against the antigenic mixture of Bothropic venoms traditionally used as immunogen to produce Bothropic antivenoms in Brazil. ELISA showed that one of the produced mAbs recognizes B. alternatus and B. neuwiedi venoms (mAb anti-Ba/Bn) specifically and Western Blot revealed that this mAb binds to a single protein band of molecular mass of ≈50 kDa. MAb anti-Ba/Bn inhibited the coagulant activity but was unable to neutralize hemorrhagic and phospholipase A2 activities caused by the B. neuwiedi venom. MAb anti-Ba/Bn was immobilized to Sepharose beads and used for immunoaffinity chromatography of B. neuwiedi venom. Proteolytic activity assays indicated that the immunoaffinity-purified fraction (BnF-Bothrops neuwiedi fraction) has a serine protease thrombin-like profile, which was supported by coagulability assays in mice. Bottom-up proteomic analysis confirmed the prevalence of serine proteases in BnF using label-free quantification. In conclusion, this work characterized a mAb with neutralizing properties against B. neuwiedi coagulant activity and demonstrates that immunoaffinity chromatography using mAbs can be a useful technique for purification of bioactive toxic proteins from Bothrops spp. snake venoms.

findMySequence: a neural-network-based approach for identification of unknown proteins in X-ray crystallography and cryo-EM

Although experimental protein-structure determination usually targets known proteins, chains of unknown sequence are often encountered. They can be purified from natural sources, appear as an unexpected fragment of a well characterized protein or appear as a contaminant. Regardless of the source of the problem, the unknown protein always requires characterization. Here, an automated pipeline is presented for the identification of protein sequences from cryo-EM reconstructions and crystallographic data. The method's application to characterize the crystal structure of an unknown protein purified from a snake venom is presented. It is also shown that the approach can be successfully applied to the identification of protein sequences and validation of sequence assignments in cryo-EM protein structures.

Sexual and ontogenetic variation of Bothrops leucurus venom

Various factors, such as geographical origin, climate, sex, age and diet can influence the composition and pathophysiological activities of snake venoms. In this study, we examined the sexual and ontogenetic variations in the venom of Bothrops leucurus, a pitviper responsible for more than 80% of the snakebites in the state of Bahia, northeastern Brazilian. The venoms of 31 snakes were pooled according to sex and age (young, adult and old) and screened by SDS-PAGE (in reducing and non-reducing conditions), reverse-phase high performance liquid chromatography (RP-HPLC), gelatin zymography, and immunoblotting with therapeutic bothropic antivenom (BAV) from the Instituto Butantan. The electrophoretic and chromatographic profiles showed intraspecific ontogenetic variation, whereas sexual variations were less evident. All venoms showed gelatinolytic activity associated with 50-75 kDa protein bands. In addition, all venoms, regardless of the snakes' sex and age, cross-reacted to similar extents with BAV. Our findings show that B. leucurus venom changes during ontogenetic development and demonstrate sexual differences in its composition, indicating differences in biological activity.

Photobiomodulation reduces cell death and cytokine production in C2C12 cells exposed to Bothrops venoms

Snakebites caused by the genus Bothrops are often associated with severe and complex local manifestations such as edema, pain, hemorrhage, and myonecrosis. Conventional treatment minimizes the systemic effects of venom; however, their local action is not neutralized. The purpose of this study was to evaluate the effect of photobiomodulation (PBM) on C2C12 muscle cells exposed to B. jararaca, B. jararacussu, and B. moojeni venoms on events involved in cell death and the release of inflammatory mediators. Cells were exposed to venoms and immediately irradiated with low-level laser (LLL) application in continuous wave at the wavelength of 660 nm, energy density of 4.4 J/cm², power of 10 mW, area of 0.045 cm², and time of 20 s. Cell integrity was analyzed by phase contrast microscope and cell death was performed by flow cytometry. In addition, interleukin IL1-β, IL-6, and IL-10 levels were measured in the supernatant. Our results showed that the application of PBM increases cell viability and decreases cell death by apoptosis and necrosis. Moreover, the release of pro-inflammatory interleukins was also reduced. The data reported here indicate that PBM resulted in cytoprotection on myoblast C2C12 cells after venom exposure. This protection involves the modulation of cell death mechanism and decreased pro-inflammatory cytokine release.

Development of a cell-based in vitro assay as a possible alternative for determining bothropic antivenom potency

Accidents with venomous snakes are a major health hazard in tropical countries. Bothrops genus is responsible for almost 80% of snakebites in Brazil. Immunotherapy is the only approved specific treatment against snake toxins and the production of therapeutic antivenoms requires quality control tests to determine their neutralizing potency. Currently, these controls are performed by in vivo lethality neutralization, however, the inhibition of particular events produced by bothropic venoms such as coagulopathy, hemorrhage, edema or cytotoxic effects are also required. The aim of this work is to develop an in vitro alternative assay for antivenom pre-clinical evaluation. In this sense, we designed a cell viability assay using different amounts (0.2-10 μL/well) of low and high potency anti-bothropic sera, previously classified by the traditional in vivo test, for assessing the antivenom capacity to protect the cells against B. jararaca venom cytotoxicity (5xEC₅₀ = 58.95 μg/mL). We found that high potency sera are more effective in neutralizing B. jararaca venom cytotoxicity when compared to low potency sera, which is in accordance to their pre-determined in vivo potency. Considering sera in vitro inhibitory concentration able to prevent 50% cell death (IC₅₀) and their known in vivo potency, a cut-off point was determined to discriminate low and high potency sera. Our data provide insights for the development of an in vitro method which can determine the anti-bothropic antivenom potency during its production.

An overview of Bothrops erythromelas venom

This review discusses studies on the venom of Bothrops erythromelas published over the past 36 years. During this period, many contributions have been made to understand the venomous snake, its venom, and its experimental and clinical effects better. The following chronological overview is based on 29 articles that were published between 1979 and 2015, with emphasis on diverse areas. The complexity of this task demands an integration of multidisciplinary research tools to study toxinology. This science is in need of renewed conceptual and experimental platforms aimed at obtaining a profound understanding of the highly complex pathophysiology of snakebite envenoming and toxins isolated from snakes.

Experimental Bothrops atrox envenomation: Efficacy of antivenom therapy and the combination of Bothrops antivenom with dexamethasone

Bothrops atrox snakes are the leading cause of snake bites in Northern Brazil. The venom of this snake is not included in the antigen pool used to obtain the Bothrops antivenom. There are discrepancies in reports on the effectiveness of this antivenom to treat victims bitten by B. atrox snakes. However, these studies were performed using a pre-incubation of the venom with the antivenom and, thus, did not simulate a true case of envenomation treatment. In addition, the local lesions induced by Bothrops venoms are not well resolved by antivenom therapy. Here, we investigated the efficacy of the Bothrops antivenom in treating the signs and symptoms caused by B. atrox venom in mice and evaluated whether the combination of dexamethasone and antivenom therapy enhanced the healing of local lesions induced by this envenomation. In animals that were administered the antivenom 10 minutes after the envenomation, we observed an important reduction of edema, dermonecrosis, and myonecrosis. When the antivenom was given 45 minutes after the envenomation, the edema and myonecrosis were reduced, and the fibrinogen levels and platelet counts were restored. The groups treated with the combination of antivenom and dexamethasone had an enhanced decrease in edema and a faster recovery of the damaged skeletal muscle. Our results show that Bothrops antivenom effectively treats the envenomation caused by Bothrops atrox and that the use of dexamethasone as an adjunct to the antivenom therapy could be useful to improve the treatment of local symptoms observed in envenomation caused by Bothrops snakes.

Bothrops atrox is the dominant species responsible for accidental human snake bites in Northern Brazil. The efficacy of antivenom therapy to correct the systemic disturbances, including hemostatic disorders, caused by Brazilian Bothrops is well known. However, two fundamental issues need to be addressed in this region. (1) There are concerns regarding the effectiveness of the antivenom to treat Bothrops snake bites in this region since Bothrops atrox venom is not used as an antigen to obtain the Bothrops antivenom in Brazil, and (2) the efficacy of the antivenom therapy in reversing local injuries induced by Bothrops venoms is low. Thus, our study aimed to assess the effectiveness of antivenom therapy alone or in combination with dexamethasone to treat experimental envenomation induced by Bothrops atrox venom in mice. Our results showed that the Brazilian Bothrops antivenom effectively reversed the systemic disturbances caused by this envenomation and combining the antivenom therapy with dexamethasone accelerated the regression of inflammatory edema and the regeneration of skeletal muscle that was damaged by the venom.

Bothrops fonsecai snake venom activities and cross-reactivity with commercial bothropic venom

In this work, we examined some biochemical and biological activities of Bothrops fonsecai venom, a pitviper endemic to southeastern Brazil, and assessed their neutralization by commercial bothropic antivenom (CAv). Cross-reactivity of venom with CAv was also assessed by immunoblotting and size-exclusion high performance chromatography (SE-HPLC). Bothrops fonsecai venom had PLA₂, proteolytic and esterase activities that were neutralized to varying extents by venom:antivenom ratios of 5:1 and 5:2 (PLA₂ and esterase activities) or not significantly by either venom:antivenom ratio (proteolytic activity). The minimum hemorrhagic dose (69.2μg) was totally neutralized by both ratios. Clotting time in rat citrated plasma was 33±10.5s (mean±SD; n=5) and was completely neutralized by a 5:2 ratio. Edema formation was dose-dependent (1-30μg/site) and significantly inhibited by both ratios. Venom (10-300μg/mL) caused neuromuscular blockade in extensor digitorum longus preparations; this blockade was inhibited best by a 5:2 ratio. Venom caused myonecrosis and creatine kinase release in vivo (gastrocnemius muscle) and in vitro (extensor digitorum longus) that was effectively neutralized by both venom:antivenom ratios. Immunoblotting showed that venom components of ~25-100kDa interacted with CAv. SE-HPLC profiles for venom incubated with CAv or specific anti-B. fonsecai antivenom raised in rabbits (SAv) indicated that CAv had a higher binding capacity than SAv, whereas SAv had higher affinity than CAv. These findings indicate that B. fonsecai venom contains various activities that are neutralized to different extents by CAv and suggest that CAv could be used to treat envenoming by B. fonsecai.

Neutralization of toxicological activities of medically-relevant Bothrops snake venoms and relevant toxins by two polyvalent bothropic antivenoms produced in Peru and Brazil

Snakebite envenoming is a neglected public pathology, affecting especially rural communities or isolated areas of tropical and subtropical Latin American countries. The parenteral administration of antivenom is the mainstay and the only validated treatment of snake bite envenoming. Here, we assess the efficacy of polyspecific anti-Bothrops serum (α-BS) produced in the Instituto Nacional de Salud (INS, Peru) and at the Fundação Ezequiel Dias (FUNED, Brazil), to neutralize the main toxic activities induced by five medically-relevant venoms of: Bothrops atrox, B. barnetti, and B. pictus from Peru, and the Brazilian B. jararaca and B. leucurus, all of them inhabiting different geographical locations. Protein electrophoretic patterns of these venoms showed significant differences in composition, number and intensity of bands. Another goal was to evaluate the efficacy and safety of lyophilized α-BS developed at INS to neutralize the detrimental effects of these venoms using in vivo and in vitro assays. The availability of lyophilized α-BS has relevant significance in its distribution to distant rural communities where the access to antivenom in health facilities is more difficult. Despite the fact that different antigen mixtures were used for immunization during antivenom production, our data showed high toxin-neutralizing activity of α-BS raised against Bothrops venoms. Moreover, the antivenom cross-reacted even against venoms not included in the immunization mixture. Furthermore, we have evaluated the efficacy of both α-BS to neutralize key toxic compounds belonging to the predominant protein families of Bothrops snakes. Most significantly, both α-BS cross-specifically neutralized the main toxicological activities e.g. lethality and hemorrhage induced by these venoms. Thus, our data indicate that both α-BS are equally effective to treat snake bite victims inflicted by Bothrops snakes particularly B. atrox, responsible for the largest numbers of human envenomations in the Amazon regions of some South American countries including Peru and Brazil.

The red seaweed Plocamium brasiliense shows anti-snake venom toxic effects

BACKGROUND

Snakebite is considered a neglected tropical disease by the World Health Organization. In Brazil, about 70% of the envenomation cases are caused by Bothrops snakes. Its venom may provoke hemorrhage, pain, necrosis, hemolysis, renal or cardiac failure and even death in victims. Since commercial antivenom does not efficiently neutralize the local toxic effects of venoms, natural products have been tested in order to provide alternative or complementary treatment to serum therapy. Therefore, the present study aimed to evaluate the ability of the seaweed Plocamium brasiliense and its active derivatives to neutralize hemorrhagic, edematogenic, hemolytic, coagulant and proteolytic activities of B. jararaca venom.

METHODS

Specimens of P. brasiliense were collected in Rio de Janeiro state, Brazil, dried and submitted to oil extraction using four solvents of increasing polarities, n-hexane (HEX), dichloromethane (DCM), ethyl acetate (ETA) and hydroalcoholic solution (HYD). The solvents were evaporated, yielding HEX, DCM, ETA and HYD extracts. Further, all extracts were dissolved in dimethylsulfoxide. In addition, two monoterpenes (8-bromo-3,4,7-trichloro-3,7-dimethyl-1E, 5E-octadiene and 1,8-dibromo-3,4,7-trichloro-3,7-dimethyl-1E, 5E-octadiene) and a cholesterol fraction were isolated from the extract of P. brasiliense prepared in hexane. Algal samples were incubated for 30 minutes with B. jararaca venom, and then tested for lethality; hemorrhagic, edematogenic, hemolytic, coagulant and proteolytic effects.

RESULTS

Most of the algal extracts inhibited the toxic effects with different potencies. The DCM extract was the most effective, since it inhibited all types of toxic activity. On the other hand, the HYD extract failed to inhibit any effect. Moreover, the isolated products inhibited proteolysis and protected mice from hemorrhage in 30% of the cases, whereas 8-bromo-3,4,7-trichloro-3,7-dimethyl-1E, 5E-octadiene inhibited 100% and 20% of the hemorrhagic and proteolytic activities, respectively. None of the algal products were toxic to mice.

CONCLUSION

Seaweeds may be a promising source of inhibitors against toxic effects caused by B. jararaca envenomation, which may contribute to antivenom treatment.

Protein content of antivenoms and relationship with their immunochemical reactivity and neutralization assays

CONTEXT

Therapy for snakebites relies on the application of antivenoms, which may be produced with different immunogenic mixtures of venom and possess different pharmaceutical characteristics. For these reasons, immunological cross-reactivity and heterologous neutralization were analyzed relative to the protein content of three antivenoms used in the Americas.

METHODS

The antivenoms studied were composed of equine F(ab')2 fragments from animals immunized with Crotalinae venoms. The antivenoms were tested against venoms of seven pit viper species from Argentina, seven from Mexico, one from Costa Rica, and one from Colombia.

RESULTS

Immunoblotting showed high cross-reactivity of all major protein bands with all the antivenoms tested. ELISA results also showed high cross-reactivity among the different venoms and antivenoms, and a high heterologous neutralization was observed. The results can be interpreted in different ways depending on whether the reactivity is considered in terms of the volume of antivenom used or by the amount of protein contained in this volume of antivenom. The antivenoms with high immunochemical reactivity and neutralizing capacity were those with higher protein content per vial; but when doses were adjusted by protein content, antivenoms of apparently lower neutralizing capacity and immunochemical reactivity showed at least similar potency and reactivity although volumetrically at higher doses.

CONCLUSION

Protein content relative to neutralization potency of different products must be taken into account when antivenoms are compared, in addition to the volume required for therapeutic effect. These results show the importance of obtaining high-affinity and high-avidity antibodies to achieve good neutralization using low protein concentration and low-volume antivenoms.

Use of a synthetic biosensor for neutralizing activity-biased selection of monoclonal antibodies against atroxlysin-I, an hemorrhagic metalloproteinase from Bothrops atrox snake venom

Background

The snake Bothrops atrox is responsible for the majority of envenomings in the northern region of South America. Severe local effects, including hemorrhage, which are mainly caused by snake venom metalloproteinases (SVMPs), are not fully neutralized by conventional serum therapy. Little is known about the immunochemistry of the P-I SVMPs since few monoclonal antibodies (mAbs) against these molecules have been obtained. In addition, producing toxin-neutralizing mAbs remains very challenging.

Methodology/Principal Findings

Here, we report on the set-up of a functional screening based on a synthetic peptide used as a biosensor to select neutralizing mAbs against SVMPs and the successful production of neutralizing mAbs against Atroxlysin-I (Atr-I), a P-I SVMP from B. atrox. Hybridomas producing supernatants with inhibitory effect against the proteolytic activity of Atr-I towards the FRET peptide Abz-LVEALYQ-EDDnp were selected. Six IgG1 Mabs were obtained (named mAbatr1 to mAbatr6) and also two IgM. mAbatrs1, 2, 3 and 6 were purified. All showed a high specific reactivity, recognizing only Atr-I and B. atrox venom in ELISA and a high affinity, showing equilibrium constants in the nM range for Atr-I. These mAbatrs were not able to bind to Atr-I overlapping peptides, suggesting that they recognize conformational epitopes.

Conclusions/Significance

For the first time a functional screening based on a synthetic biosensor was successfully used for the selection of neutralizing mAbs against SVMPs.

In this work, we propose a new screening strategy to produce monoclonal antibodies against Atr-I, a P-I class SVMP from Bothrops atrox, which is the snake responsible for the majority of the accidents in South America. SVMPs are the main toxic factors in Bothrops venom causing systemic and local hemorrhage, which may evolve to inflammation and/or necrosis. Since the toxic effects of SVMPs are related to their proteolytic activity, we have produced a peptide which was used as a biosensor for Atr-I hydrolysis. Hydrolysis of this substrate was monitored and the clones possessing inhibitory activity against the proteolytic activity of Atr-I upon the peptide were selected. Using our new approach, we have obtained four monoclonal antibodies highly specific and with neutralizing capacity against the hemorrhagic activity of either Atr-I alone or Bothrops atrox whole venom. To the best of the authors' knowledge, this is the first time where a functional screening is used for the selection of neutralizing mAbs against SVMPs. It is also the first description of mAbs anti-Atr-I, with inhibitory potential against its toxic activities which may be useful for diagnosis and treatment in the future.

Comparison of phylogeny, venom composition and neutralization by antivenom in diverse species of bothrops complex

In Latin America, Bothrops snakes account for most snake bites in humans, and the recommended treatment is administration of multispecific Bothrops antivenom (SAB – soro antibotrópico). However, Bothrops snakes are very diverse with regard to their venom composition, which raises the issue of which venoms should be used as immunizing antigens for the production of pan-specific Bothrops antivenoms. In this study, we simultaneously compared the composition and reactivity with SAB of venoms collected from six species of snakes, distributed in pairs from three distinct phylogenetic clades: Bothrops, Bothropoides and Rhinocerophis. We also evaluated the neutralization of Bothrops atrox venom, which is the species responsible for most snake bites in the Amazon region, but not included in the immunization antigen mixture used to produce SAB. Using mass spectrometric and chromatographic approaches, we observed a lack of similarity in protein composition between the venoms from closely related snakes and a high similarity between the venoms of phylogenetically more distant snakes, suggesting little connection between taxonomic position and venom composition. P-III snake venom metalloproteinases (SVMPs) are the most antigenic toxins in the venoms of snakes from the Bothrops complex, whereas class P-I SVMPs, snake venom serine proteinases and phospholipases A₂ reacted with antibodies in lower levels. Low molecular size toxins, such as disintegrins and bradykinin-potentiating peptides, were poorly antigenic. Toxins from the same protein family showed antigenic cross-reactivity among venoms from different species; SAB was efficient in neutralizing the B. atrox venom major toxins. Thus, we suggest that it is possible to obtain pan-specific effective antivenoms for Bothrops envenomations through immunization with venoms from only a few species of snakes, if these venoms contain protein classes that are representative of all species to which the antivenom is targeted.

Snakebite envenomation is a serious health issue in Latin America, particularly in the Amazon, where antivenom administration may be delayed due to logistic constraints. Bothrops snakes are involved in most of the snakebite-related accidents in Brazil. This work reports a comparative study of the toxin composition and antigenicity of the Bothrops venoms used to prepare the commercial antivenom and its effectiveness against the venom from Bothrops atrox, a prevalent Amazon species that is not included in the pool. Our data show a lack of connection between Bothrops taxonomic identity and venom composition. We also show that different toxins display distinct reactivity with the tested antivenom. However, the antivenom reacted similarly with each class of toxin present in the venoms of the different snakes studied. Important evidence was the neutralization of the major toxic effects of B. atrox venom, not included in the mixture of antigens used to produce the antivenom. Based on the observed antigenicity of the distinct protein classes of toxins, we suggest that it is possible to obtain pan-specific and efficient Bothrops antivenoms via immunization with venoms from a few species of snakes that are representative of the protein composition of a large number of targeted species.

Exploring the proteomes of the venoms of the Peruvian pit vipers Bothrops atrox, B. barnetti and B. pictus

We report the comparative proteomic characterization of the venoms of Bothrops atrox, B. barnetti and B. pictus. The venoms were subjected to RP-HPLC and the resulting fractions analyzed by SDS-PAGE. The proteins were cut from the gels, digested with trypsin and identified via peptide mass fingerprint and manual sequencing of selected peptides by MALDI-TOF/TOF mass spectrometry. Around 20-25 proteins were identified belonging to only 6-7 protein families. Metalloproteinases of the classes P-I and P-III were the most abundant proteins in all venoms (58-74% based on peak area A214 nm), followed by phospholipases-A(2) (6.4-14%), disintegrins (3.2-9%) and serine proteinases (7-11%), and some of these proteins occurred in several isoforms. In contrast cysteine-rich secretory proteins and L-amino acid oxidases appeared only as single isoforms and were found only in B. atrox and B. barnetti. C-type lectins were also detected in all venoms but at low levels (~ 5%). Furthermore, the venoms contain variable numbers of peptides (<3 kDa) and non-protein compounds which were not considered in this work. The protein composition of the investigated Bothrops species is in agreement with their pharmacological and pathological effects.

Studies on pharmacological effects of Russell's viper and Saw-scaled viper venom and its neutralization by chicken egg yolk antibodies

Antivenom antibodies were raised in 24-week-old white leghorn chickens against hemotoxic venoms of Russell's viper and Saw-scaled viper snakes. Booster injections of increasing concentrations of venom were given at 14days of time interval to raise the antivenom level in egg yolk. Antibodies were extracted from immunized chicken egg yolk by Polson et al. (Polson A., Von Wechmar M.B., Van Regenmortel M.H.V. Isolation of viral IgY antibodies from yolks of immunized hens. Immunological Communications 1980; 9:475-493.) and further purified by DEAE cellulose ion exchange column chromatography, which gave pure (180-200kDa) specific antibodies against venom. High titre of more than 1:10,000 antibodies were detected by ELISA at the 135th day of observation. The lethal toxicity and various pharmacological activities like hemorrhagic activity, phospholipase activity, edema and procoagulant activities of venom were carried out by both in vivo and in vitro methods. The effectiveness of antivenom in neutralizing these effects was carried out involving pre-incubation type experiments. The median effective dose (ED50) for Russell's viper venom was 0.96mg/2LD50/18g mice and for Saw-scaled viper venom it was 1.28mg/2LD50/18g mice. One millilitre of specific antivenom was effective in neutralizing 0.110mg of Russell's viper and 0.137mg of Saw-scaled viper venoms respectively (PD50). Antivenom was effective in neutralization assays in a dose dependent manner. The results indicate that antibodies raised in chicken could effectively neutralize the pharmacological effects induced by venoms and chickens therefore present an alternative and cheaper source of specific antibody generation.

Structural and functional characterization of a P-III metalloproteinase, leucurolysin-B, from Bothrops leucurus venom

Leucurolysin-B (leuc-B) is an hemorrhagic metalloproteinase found in the venom of Bothrops leucurus (white-tailed-jararaca) snake. By means of liquid chromatography consisting of gel filtration on Sephracryl S-200, S-300 and ion-exchange on DEAE Sepharose, leuc-B was purified to homogeneity. The proteinase has an apparent molecular mass of 55kDa as revealed by the reduced SDS-PAGE, and represents approximately 1.2% of the total protein in B. leucurus venom. The partial amino acid sequence of leuc-B was determined by automated Edman sequencing of peptides derived from digests of the S-reduced and alkylated protein with trypsin. Leuc-B exhibits the characteristic motif of metalloproteinases, HEXXHXXGXXH and a methionine-containing turn of similar conformation ("Met-turn"), which forms a hydrophobic basis for the zinc ions and the three histidine residues involved as ligands. Leuc-B has been characterized as a P-III metalloproteinase and possesses a multidomain structure including a metalloproteinase, a disintegrin-like (ECD sequence instead of the typical RGD motif) and a cysteine-rich C-terminal domain. Leuc-B contains three potential sites of N-glycosylation. The enzyme only cleaves the Ala14-Leu15 peptide bond of the oxidized insulin B-chain and preferentially hydrolyzes the Aalpha-chain of fibrinogen and the alpha-chain of fibrin. Its proteolytic activity was completely inhibited by metal chelating agents but not by other typical proteinase inhibitors. In addition, its enzymatic activity was stimulated by the divalent cations Ca2+ and Mg2+ but inhibited by Zn2+ and Cu2+. The catalytic activity of leuc-B on extracellular matrix proteins could readily lead to loss of capillary integrity resulting in hemorrhage occurring at those sites (MHD=30ng in rabbit), with alterations in platelet function. In summary, here we report the isolation and the structure-function relationship of a P-III snake venom metalloproteinase.

Evaluation of three Brazilian antivenom ability to antagonize myonecrosis and hemorrhage induced by Bothrops snake venoms in a mouse model

Despite preventing death after snakebites, there is little evidence that polyvalent antivenoms (PAVs) protect against myotoxicity and local damages. We evaluated antibothropic Brazilian PAVs from three manufacturers against the myotoxicity and hemorrhagic activity of Bothrops jararacussu and B. jararaca venoms, respectively, by using two protocols: preincubation of PAVs with venom, and i.v. pretreatment with PAVs, prior to the venom inoculation. In this investigation, we used doses of PAVs ranging from 0.4 to 4.0mL/mg of venom equivalent up to 10 times the amount recommended by the producers for the clinical practice in Brazil. In our preincubation protocol in vivo, PAVs antagonized myotoxicity of B. jararacussu venom by 40-95%, while our pretreatment protocol antagonized myotoxic activity by 0-60%. Preincubation of antivenoms with B. jararaca venom antagonized its hemorrhagic activity by 70-95%, while pretreatment antagonized hemorrhagic activity by 10-50%. Although all PAVs demonstrated partial antagonism against both venoms, the magnitude of these effects varied greatly among the manufactures. The results suggest that the current clinical doses of these PAVs may have negligible antimyotoxic effect.

Cytotoxic, thrombolytic and edematogenic activities of leucurolysin-a, a metalloproteinase from Bothrops leucurus snake venom

Leucurolysin-a (leuc-a), a 23 kDa non-hemorrhagic metalloproteinase, is found in venom of the viper Bothrops leucurus. Here, we examine the biological consequences of leuc-a, including thrombolytic activity, direct effects on endothelial cells in culture and edematogenic activity in vivo. We demonstrate fibrinolytic activity of leuc-a, in which the protease specifically degrades alpha, beta, and gamma-gamma chains. While not causing hemorrhaging, leuc-a does cause thrombolytic activities in whole blood clots. Endothelial cells are highly resistant to leuc-a in culture. Cell viability suffered only when cells were exposed to large quantities of the protease. Nevertheless, leuc-a induces changes in cell morphology. The impact of leuc-a on cell adhesion was confirmed by an adhesion assay, in which cell adhesion to fibronectin decreased due to leuc-a. This mild cellular impact is unlike that of crude venom, where lower concentrations triggered cell death and a greater reduction in cell adhesion. Also, leuc-a increased microvessel permeability with marked edema in mice peritoneum and foot pads. These effects are similar to those of other P-I class SVPMs. These in vivo effects were weaker when crude venom was tested. In conclusion, albeit not showing significant hemorrhagic activity, leuc-a can induce a prominent edema which appears to be significant in the local effects observed after B. leucurus venom accidents.

Perfil clínico e imunológico de bovinos experimentalmente inoculados com veneno bruto e iodado de Bothrops alternatus

Dez novilhas mestiças, distribuídas em dois grupos experimentais (n=5) receberam na altura média da face cranial do membro anterior direito, entre as articulações umerorradioulnar e do carpo, por via intramuscular superficial, 0,15mg/kg de veneno de Bothrops alternatus bruto ou iodado. Todos os animais foram avaliados clinicamente antes - tempo zero - e às 6 e 10h, no 2º, 3º, 4º, 5º, 8º, 11º, 18º e 25º dias após a inoculação dos venenos. Dois animais do grupo que recebeu veneno bruto foram a óbito às 53h e 78h e os sobreviventes apresentaram apatia, letargia, anorexia, postura indicativa de dor, melena, petéquias e sufusões nas mucosas, aumento do tempo de preenchimento capilar, enfartamento ganglionar regional, aumento das freqüências respiratória e cardíaca, redução da freqüência de pulsação arterial periférica, elevação da temperatura retal e diminuição da movimentação ruminal. No local da inoculação do veneno bruto houve sangramento e ulceração dérmica, além de aumento significativo na circunferência e dobra da pele do membro inoculado, revelando formação de edema. Todos os animais também foram avaliados imunologicamente no 17º, 24º, 31º, 45º, 60º e 180º dia. Somente os que receberam veneno bruto produziram anticorpos, detectados até o 45º dia. Os que receberam veneno botrópico iodado apresentaram alterações gerais e locais de menor intensidade, porém sem produção de IgG nos tempos pesquisados, demonstrando que a iodação alterou a composição bioquímica do veneno, diminuindo sua toxicidade e imunogenicidade.

Purification and partial characterization of two phospholipases A2 from Bothrops leucurus (white-tailed-jararaca) snake venom

Two proteins with phospholipase A(2) (PLA(2)) activity were purified to homogeneity from Bothrops leucurus (white-tailed-jararaca) snake venom through three chromatographic steps: Conventional gel filtration on Sephacryl S-200, ion-exchange on Q-Sepharose and reverse phase on Vydac C4 HPLC column. The molecular mass for both enzymes was estimated to be approximately 14 kDa by SDS-PAGE. The N-terminal sequences (48 residues) show that one enzyme presents lysine at position 48 and the other an aspartic acid in this position, and therefore they were designated blK-PLA(2) and blD-PLA(2) respectively. blK-PLA(2) presented negligible levels of PLA(2) activity as compared to that of blD-PLA(2). The PLA(2) activity of both enzymes is Ca(2+)-dependent. blD-PLA(2) did not have any effect upon platelet aggregation induced by arachidonic acid, ADP or collagen, but strongly inhibits coagulation and is able to stimulate Ehrlich tumor growth but not angiogenesis.

Purification and properties of a coagulant thrombin-like enzyme from the venom of Bothrops leucurus

A thrombin-like enzyme from Bothrops leucurus venom, named leucurobin (leuc), was purified by gel filtration, affinity and ion exchange chromatographies. Physicochemical studies indicated that the purified enzyme is a 35 kDa monomeric glycoprotein on SDS-PAGE under reducing conditions, which decreased to 29 kDa after deglycosylation with N-glycosidase F (PNGase F). The amino acid sequence of leuc was determined by automated sequencing of the intact native protein and peptides produced by digestion of the S-pyridyl-ethylated protein with trypsin. The protein sequence exhibits significant similarities with other serine proteases reported from snake venoms, and contains two potential sites of N-linked glycosylation. The proteinase split off fibrinopeptide A (FPA) rapidly from human fibrinogen; however, only negligible traces of fibrinopeptide B (FPB) were observed. In addition, the enzyme released the N-terminal peptide (Mr=4572) containing the first 42 residues from the Bbeta-chain. Leuc could neither activate factor XIII nor release kinins from heat-treated bovine plasma. Its specific clotting activity was equivalent to 198 NIH thrombin U/mg on human fibrinogen. Kinetic properties of leuc were determined using representative chromogenic substrates. The enzyme evoked the gyroxin syndrome when injected into the tail veins of mice at levels of 0.143 microg/g mouse. The inhibitory effects of PMSF and benzamidine on the amidolytic activity suggest that leuc is a serine proteinase, and inhibition by beta-mercaptoethanol revealed the important role of the disulfide bonds in the stabilization of the native structure. Antibothropic serum, SBTI and EDTA had little or no effect on its amidolytic activity. However, the clotting effect of the enzyme was strongly inhibited by antibothropic serum. A Dixon plot showed that the hydrolysis of Bz-L-Arg-pNA by leuc was competitively inhibited by benzamidine (Ki=1.61+/-0.25 mM).

Isolation and biochemical characterization of a fibrinolytic proteinase from Bothrops leucurus (white-tailed jararaca) snake venom

In investigations aimed at characterizing snake venom clot-dissolving enzymes, we have purified a fibrinolytic proteinase from the venom of Bothrops leucurus (white-tailed jararaca). The proteinase was purified to homogeneity by a combination of molecular sieve chromatography on Sephacryl S-200 and ion-exchange chromatography on CM Sepharose. The enzyme called leucurolysin-a (leuc-a), is a 23 kDa metalloendopeptidase since it is inhibited by EDTA. PMSF, a specific serine proteinase inhibitor had no effect on leuc-a activity. The amino acid sequence was established by Edman degradation of overlapping peptides generated by a variety of selective cleavage procedures. Leuc-a is related in amino acid sequence to reprolysins. The protein is composed of 200 amino acid residues in a single polypeptide chain, possessing a blocked NH2-terminus and containing no carbohydrate. The proteinase showed proteolytic activity on dimethylcasein and on fibrin (specific activity=21.6 units/mg and 17.5 units/microg, respectively; crude venom=8.0 units/mg and 9.5 units/microg). Leuc-a degrades fibrin and fibrinogen by hydrolysis of the alpha chains. Moreover, the enzyme was capable of cleaving plasma fibronectin but not the basement membrane protein laminin. Leuc-a cleaved the Ala14-Leu15 and Tyr16-Leu17 bonds in oxidized insulin B chain. The pH optimum of the proteolysis of dimethylcasein by leuc-a was about pH 7.0. Antibody raised in rabbit against the purified enzyme reacted with leuc-a and with the crude venom of B. leucurus. In vitro studies revealed that leuc-a dissolves clots made either from purified fibrinogen or from whole blood, and unlike some other venom fibrinolytic metallopeptidases, leuc-a is devoid of hemorrhagic activity when injected (up to 100 microg) subcutaneously into mice.

Duvernoy's gland secretion of Philodryas olfersii and Philodryas patagoniensis (Colubridae): Neutralization of local and systemic effects by commercial bothropic antivenom (Bothrops genus)

Colubrids involved in human envenomation in Brazil are mainly from the genera Helicops, Oxyrhopus, Thamnodynastes and Philodryas. There is a relatively large number of clinical descriptions involving the Xenodontinae snakes, Philodryas olfersii and Philodryas patagoniensis, in human accidents. The most common manifestations of envenomation are local pain, swelling, erythema and ecchymosis and regional lymphadenopathy with normal coagulation. The aims of this study were to characterize the biochemical and biological properties of P. olfersii and P. patagoniensis venoms, and to investigate their immunological cross-reactivities by using both specific antisera and anti-Bothrops sp serum used for human serum therapy in Brazil, in neutralizing the lethal and hemorrhagic effects of these venoms. We show here that P. olfersii e P. patagoniensis venoms present proteolytic and haemorrhagic activities but are devoid of phospholipase A2 activity. Haemorrhage and lethality induced by P. olfersii and P. patagoniensis are associated with metal-dependent proteinases, since EDTA could block these toxic activities. P. olfersii and P. patagoniensis venoms were immunogenic and the antisera produced were able to recognize several bands in P. olfersii, P. patagoniensis venoms in Bothrops jararaca venom.

Biological and immunological properties of the venom of Bothrops alcatraz, an endemic species of pitviper from Brazil

Bothrops alcatraz is a new pitviper species derived from the Bothrops jararaca group, whose natural habitat is situated in Alcatrazes Archipelago, a group of marine islands near São Paulo State coast in Brazil. Herein, the biological and biochemical properties of venoms of four adult specimens of B. alcatraz were examined comparatively to a reference pool of Bothrops jararaca venom. Both venoms showed similar activities and electrophoretic patterns, but B. alcatraz venom showed three protein bands of molecular masses of 97, 80 and 38 kDa that were not present in B. jararaca reference venom. The i.p. median lethal dose of B. alcatraz venom ranged from 5.1 to 6.6 mg/kg, while it was 1.5 mg/kg for B. jararaca venom. The minimum hemorrhagic dose of B. jararaca venom was 0.63, whereas 2.28 mug/mouse for B. alcatraz venom. In contrast, B. alcatraz venom was more potent in regard to procoagulant and proteolytic activities. These differences were supported by western blotting and neutralization tests, employing commercial bothropic antivenom, which showed that hemorrhagic and lethal activities of B. alcatraz venom were less effectively inhibited than B. jararaca venom. Such results evidence that B. alcatraz shows quantitative and qualitative differences in venom composition in comparison with its B. jararaca relatives, which might represent an optimization of venom towards a specialized diet.

The variability of Vipera ammodytes ammodytes venoms from Croatia--biochemical properties and biological activity

Vipera ammodytes ammodytes venom has been used for many years in Croatia for immunization of horses and production of specific therapeutic anti-venoms. The neutralizing effectiveness of anti-venoms is directly dependent on the properties of the snake venom used for immunization. Therefore, appropriate characterization of the whole venom is necessary prior to use in the immunization procedure. In the course of such analyses, the variability in biochemical properties and biological activity was observed in venoms collected from snakes originating from different parts of Croatia. The venom pools also differed with respect to time of snake collection (1992-2003). Analyses of three samples of whole venom pools were carried out revealing differences in lethal activity (LD50), minimum haemorrhagic dose (MHD), minimum necrotizing dose (MND), phospholipase A2 activity and in anticomplementary activity. SDS-PAGE electrophoretic patterns were similar, but not identical, for all tested venom pools with respect to the number of protein bands detected, but intensity of particular components differed. Preliminary immunogenicity testing in terms of determination of specific antibodies revealed similar immunogenicity and high cross-reactivity for three samples tested.

Comparison of the neurotoxic and myotoxic effects of Brazilian Bothrops venoms and their neutralization by commercial antivenom

The venoms of some Bothrops species produce neuromuscular blockade in avian and mammalian nerve-muscle preparations in vitro. In this study, we compared the neuromuscular activities (myotoxicity and neurotoxicity) of venoms from several Brazilian species of Bothrops (B. jararaca, B. jararacussu, B. moojeni, B. erythromelas and B. neuwiedi) in chick isolated biventer cervicis muscle preparations and examined their neutralization by commercial antivenom. All of the venoms (50-200 microg/ml, n = 3 - 7 each) induced long-lasting, concentration-dependent muscle contracture and twitch-tension blockade, and also inhibited the muscle responses to acetylcholine and KCl. Preincubation of the venoms (200 microg/ml) with bothropic antivenom (0.2 ml) for 30 min at 37 degrees C prevented the twitch-tension blockade to different extents, with the protection varying from 0.5% (B. neuwiedi) to 88% (B. moojeni). Complete protection against the neuromuscular action of B. neuwiedi venom was observed only with a mixture of bothropic and crotalic antivenoms. The venoms caused either high (B. jararacussu, B. neuwiedi and B. moojeni) or low (B. jararaca and B. erythromelas) creatine kinase release. Morphologically, myonecrosis was greatest with B. jararacussu venom (98-100% of fibers damaged) and least with B. jararaca venom (74% damage). The extent of neutralization by bothropic antivenom was B. jararaca (93%)>B. erythromelas (65.8%)>B. moojeni (30.7%)>B. neuwiedi (20%)>B. jararacussu (no neutralization). Despite this variation in neutralization, enzyme-linked immunosorbent assays indicated similar immunoreactivities for the venoms, although immunoblots revealed quantitative variations in the bands detected. These results show that Bothrops venoms produce varying degrees of neuromuscular blockade in chick nerve-muscle preparations. The variable protection by antivenom against neuromuscular activity indicates that the components responsible for the neuromuscular action may differ among the venoms.

Most cited papers in Toxicon

Citation of a published work is one of the parameters considered in the analysis of relevance and importance of scientific contributions. In 2002, for the first time the Impact Factor of Toxicon has risen above 2.0, placing it at the 17th position among 76 journals in the 'toxicology' field. The aim of this article was to identify the most cited articles in Toxicon, that have contributed to the steady increase of its Impact Factor. The number of citations, complete reference and type of all documents appearing in Toxicon in the period 1963-2003 were retrieved from the ISI Web-of-Science homepage. The documents retrieved were sorted by the number of citations received. A 'citation index', defined as the number of citations divided by the number of years since publication, was calculated for each document. It was clearly seen that reviews in Toxicon received 4.4-fold more citations than articles. Unexpectedly, it was found that recent papers were proportionally more cited than old ones. A decrease in the proportion of papers dealing on 'snake*' through out the period and the broadened range of subjects of the most cited papers recently published in Toxicon reflects an increased 'visibility' in other fields of toxinology. Research on plant toxins gained its own space in Toxicon with newer publications showing high citation indexes. It can be postulated that these facts helped to increase Toxicon's Impact Factor from 1.248 in 1999 to 2.003 in 2002. With the increased number of issues in Toxicon as well as publications of subject-dedicated volumes containing mostly reviews, the Impact Factor of Toxicon is expected to keep rising in the near future.

Pulmonary mechanics and lung histology in acute lung injury induced by Bothrops jararaca venom

Pulmonary mechanics [static (Est) and dynamic (Edyn) elastances, resistive (DeltaP1) and viscoelastic pressures (DeltaP2)], histology, and bronchoalveolar lavage fluid (BALF) from BALB/c mice were analysed 1, 24, 48 and 72 h after intravenous injection of saline or Bothrops jararaca crude venom [0.3 (V0.3) or 1 (V1) microg.g(-1)]. Est, Edyn, and DeltaP2 increased at 1 h in both V groups, being significantly higher in V1 than in V0.3, decreasing progressively, reaching control values at 48 h in V0.3, but remaining altered in V1 at 72 h. DeltaP1 augmented in V1 at 1 h, returning to normal at 72 h. Histological changes in V0.3 group included interstitial oedema, alveolar collapse, and increased cellularity, which returned to normal at 48 h. These changes were more intense in V1 group, with alveolar oedema and haemorrhage. BALF showed time-dependent neutrophil influx in V0.3. In conclusion, venom led to time- and dose-dependent pulmonary mechanical changes, together with moderate inflammation in V0.3 and acute lung injury in V1.

Pharmacological characterization of mouse hind paw oedema induced by Bothrops insularis (jararaca ilhoa) snake venom

Bothrops snake venoms produce marked local effects, including oedema, haemorrhage and necrosis. The ability of Bothrops insularis venom to induce oedema in mice was investigated. Venom was injected into hind paws and the change in volume over time was measured by plethysmometry. B. insularis venom (0.01-2.5 microg/paw) induced paw oedema which, at high doses (>/=0.5 microg/paw), was accompanied by haemorrhage. The peak oedematogenic response occurred 3 h after venom injection with all doses and decreased gradually thereafter, but was still elevated with high doses after 24 h. Pretreating the mice with cyproheptadine (histamine H(1) and serotonin 5-HT(2) receptor antagonist), mepyramine (histamine H(1) receptor antagonist), L-NAME (inhibitor of nitric oxide synthase), indomethacin and rofecoxib (inhibitors of cyclooxygenases), and dexamethasone (indirect inhibitor of PLA(2)) significantly attenuated venom-induced oedema, whereas methysergide, a serotonin 5-HT(1)/5-HT(2) receptor antagonist, had no effect. The administration of antivenom 30 min before or immediately after venom injection also significantly inhibited venom-induced oedema. These results show that B. insularis venom causes oedema in the mouse hind paw and that this response is mediated by histamine, nitric oxide, and arachidonic acid metabolites formed by cyclooxygenases 1 and 2. The neutralization by commercial antivenom indicates that the venom components responsible for oedema are recognized by the antivenom and share immunological identity with their counterparts in the venoms of mainland Bothrops species.