An enzyme linked immunosorbent assay (ELISA) that discriminates between Bothrops atrox and Lachesis muta muta venoms

Assessing the Efficacy of Monovalent and Commercialized Antivenoms for Neutralizing Moroccan Cobra Naja haje Venom: A Comparative Study

In Morocco, eight species of venomous snakes belonging to the Viperidae and Elapidae families are responsible for severe envenomation cases. The species from the Elapidae family is only represented by the medically relevant cobra Naja haje, which is widely distributed in North Africa. However, there is little information on the systemic effects of Moroccan cobra venom on vital organs due to regional variations. It has been demonstrated that the venom of Naja haje from Egypt causes hemorrhage, while the venom of the Moroccan cobra is neurotoxic and devoid of systemic bleeding. This variability is known to significantly influence treatment efficacy against Naja haje cobra bites in the Middle East. In this study, we examined the pathophysiological mechanisms responsible for the lethality induced by Naja haje venom, as well as the evaluation of the neutralizing capacity of two antivenoms; the monospecific antivenom made for Naja haje only and the antivenom marketed in the Middle East and North Africa. We first determined the toxicity of Naja haje venom by LD₅₀ test, then compared the neutralizing capacity of the two antivenoms studied by determining the ED₅₀. We also performed histological analysis on Swiss mice envenomed and treated with these antivenoms to observe signs of cobra venom envenomation and the degree of reduction of induced systemic alterations. The results showed significant differences between both antivenoms in terms of neutralization. The monospecific antivenom was four times more effective than the marketed antivenom. These results were confirmed by a histological study, which showed that monospecific antivenoms neutralized severe signs of mortality, such as congestion of blood vessels in the heart and kidneys, pulmonary and renal edema, cytoplasmic vacuolization of hepatocytes in the liver, and infiltration of inflammatory cells in the brain and spleen. However, the polyvalent antivenom failed to protect all severe lesions induced by Naja haje venom in mice. These findings highlight the negative impact of geographic variation on the effectiveness of conventional antivenom therapy and confirm the need for a specific Naja haje antivenom for the effective treatment of cobra envenomation in Morocco.

The Colombian bushmasters Lachesis acrochorda (García, 1896) and Lachesis muta (Linnaeus, 1766): Snake species, venoms, envenomation, and its management

In Colombia, there are two species of bushmaster snakes, Lachesis acrochorda, which is distributed mainly in the west of the country (in the Choco region), and Lachesis muta in the southeast (in the Amazon and Orinoquia region), whose presence has been reduced due to the destruction of their habitats. Captive maintenance is challenging, making it difficult to obtain their venom for study and antivenom manufacturing. They are the largest vipers in the world. The occurrence of human envenomation is quite rare, but when it occurs, it is associated with high mortality. Bushmaster venom is necrotizing, hemorrhagic, myotoxic, hemolytic, and cardiovascular depressant. Due to the presence of bradycardia, hypotension, emesis, and diarrhea in some patients (Lachesis syndrome), the possibility of a vagal or cholinergic effect is raised. The treatment of envenomation is hindered by the scarcity of antivenom and the need to use high doses. A review of the most relevant biological and medical aspects of bushmaster snakes is presented, mainly for those occurring in Colombia, to facilitate their recognition and raise awareness about the need for special attention to improve their conservation and advance scientific knowledge, in particular, about their venom.

Development of sandwich ELISA and lateral flow assay for the detection of Bungarus multicinctus venom

Snakebite envenoming adversely affects human health and life worldwide. Presently, no suitable diagnostic tools for snakebite envenoming are available in China. Therefore, we sought to develop reliable diagnostic tests for snakebite management. We conducted affinity purification experiments to prepare species-specific antivenom antibody (SSAb). In brief, affinity chromatography with an antibody purification column (Protein A) was conducted to purify immunoglobulin G from Bungarus multicinctus (BM) venom hyperimmunized rabbit serum. The cross-reactive antibodies were removed from commercial BM antivenin by immune adsorption on the affinity chromatography columns of the other three venoms, Bungarus Fasciatus (FS), Naja atra (NA), and O. hannah (OH), generating SSAb. The results of western blot analysis and enzyme-linked immunosorbent assay (ELISA) showed the high specificity of the prepared SSAb. The obtained antibodies were then applied to ELISA and lateral flow assay (LFA) to detect BM venom. The resulting ELISA and LFA could specifically and rapidly detect BM venom in various samples with the limits of quantification as 0.1 and 1 ng/ml, respectively. This method could effectively detect snake venom in experimentally envenomed rats (simulating human envenomation), which could distinguish positive and negative samples within 10-15 min. This method also showed promise in serving as a highly useful tool for a rapid clinical distinguishing of BM bites and rational use of antivenom in emergency centers. The study also revealed cross-reactivity between BM and heterogenous venoms, suggesting that they shared common epitopes, which is of great significance for developing detection methods for venoms of the snakes belonging to the same family.

Snakebite Envenoming Diagnosis and Diagnostics

Snakebite envenoming is predominantly an occupational disease of the rural tropics, causing death or permanent disability to hundreds of thousands of victims annually. The diagnosis of snakebite envenoming is commonly based on a combination of patient history and a syndromic approach. However, the availability of auxiliary diagnostic tests at the disposal of the clinicians vary from country to country, and the level of experience within snakebite diagnosis and intervention may be quite different for clinicians from different hospitals. As such, achieving timely diagnosis, and thus treatment, is a challenge faced by treating personnel around the globe. For years, much effort has gone into developing novel diagnostics to support diagnosis of snakebite victims, especially in rural areas of the tropics. Gaining access to affordable and rapid diagnostics could potentially facilitate more favorable patient outcomes due to early and appropriate treatment. This review aims to highlight regional differences in epidemiology and clinical snakebite management on a global scale, including an overview of the past and ongoing research efforts within snakebite diagnostics. Finally, the review is rounded off with a discussion on design considerations and potential benefits of novel snakebite diagnostics.

Can anti-bothropstoxin-I antibodies discriminate between Bothrops jararaca and Bothrops jararacussu venoms?

Background

Snakes of the genus Bothrops, popularly known as pit vipers, are responsible for most cases of snakebite in Brazil. Within this genus, Bothrops jararacussu and B. jararaca deserve special attention due to the severity of their bites and for inhabiting densely populated areas. Regarding the treatment of snakebites by Bothrops jararacussu, questions have been raised about the effectiveness of the specific bothropic antivenom in neutralizing myotoxic effects; however, there are no accurate data for humans. Thus, the development of a differential diagnostic kit for this species would be of great interest because it provides, for healthcare professionals, a tool that would allow us to determine whether the accident was caused by B. jararacussu or other species of the genus. It would also make it possible to evaluate the specificity of the treatment and to provide data for epidemiological studies.

Methods

First, we produced a species-specific polyclonal antibody – a potential biomarker of Bothrops jararacussu venom – against bothropstoxin-I (BthTx-I), which is also found in smaller quantities in the venoms of B. jararaca from southern Brazil.

Results

Polyclonal antibodies against bothropstoxin-I could be separated into several species-specific immunoglobulins. Then, aiming to develop a system of safe and standardized immunoassay, we produced monoclonal antibodies. Seven hybridomas were obtained. Five of them were specific to the venom of B. jararacussu and two recognized the venom of B. jararaca from the southeastern population. The use of monoclonal antibodies also made it possible to differentiate B. jararacussu from B. jararaca venom obtained from the southern population. Analyzing the reactivity of monoclonal antibodies against other bothropic venoms, we found mAb Bt-3 to be more specific than others for B. jararacussu venom.

Conclusions

These results show the potential of BthTx-I for producing monoclonal antibodies that differentiate between B. jararacussu and other Bothrops species venoms.

Detection and neutralization of cobra venom using rabbit antiserum in experimental envenomated mice

A sandwich enzyme-linked immunosorbent assay (ELISA) was developed to detect the venom of Indian cobra ( Naja naja naja) in various tissues (brain, heart, lungs, liver, spleen, blood, kidneys, and tissue at the site of injection) of mice after cobra venom injected at different time intervals (0, 2, 4, 6, 8, and 12 h intervals up to 24 h). Whole venom antiserum or individual venom protein antiserum (14, 29, 65, 72, and 99 kDa) could recognize N. n. naja venom by Western blotting and ELISA, and antibody titer was also assayed by ELISA. Antiserum raised against cobra venom in rabbit significantly neutralized the toxicity of venom-injected mice at different time intervals after treatment. The assay could detect N. n. naja venom levels up to 2.5 ng/ml of tissue homogenate, and the venom was detected up to 24 h after venom injection. Venom was detected in brain, heart, lungs, liver, spleen, kidneys, tissue at the bite area, and blood. As observed in mice, tissue at the site of bite area showed the highest concentration of venom and the brain showed the least. Moderate amounts of venoms were found in liver, spleen, kidneys, heart, and lungs. Development of a simple, rapid, and species-specific diagnostic kit based on this ELISA technique useful to clinicians is discussed.

Peptide fingerprinting of snake venoms by direct infusion nano-electrospray ionization mass spectrometry: potential use in venom identification and taxonomy

Fingerprinting by mass spectrometry has been increasingly used to study venom variations and for taxonomic analyses based on venom components. Most of these studies have concentrated on components heavier than 3 kDa, but Bothrops snake venoms contain many biologically active peptides, principally C-type natriuretic peptides and bradykinin-potentiating peptides (BPPs). In this work, we have examined the peptide profile of Bothrops venoms (B. alternatus, B. erythromelas, B. insularis, B. jararaca, B. jararacussu, B. leucurus and B. moojeni) using direct infusion nano-electrospray ionization mass spectrometry (nano-ESI-MS) subjecting the data further to principal components analysis (PCA) to assess whether the peptide distributions are reliable in distinguishing the venoms. ESI-MS of a low molar mass fraction obtained by ultrafiltration of each venom (5 kDa nominal cutoff filters) revealed that the venoms have a variety of peptides in common but that each venom also contains taxonomic marker peptides not shared with other venoms. One BPP peptide, QGGWPRPGPEIPP, was found to be common to the seven Bothrops species examined. This peptide may represent a specific marker for this genus since it was not found in the venom of the South American rattlesnake, Crotalus durissus terrificus. PCA on the ESI-MS data reveals a close relationship between B. jararaca, B. jararacussu and B. moojeni venoms, with B. leucurus and B. erythromelas being more distant from these three; B. alternatus and B. insularis were also located distant from these five species, as was C. d. terrificus. These results agree partially with established phylogenetic relationships among these species and suggest that ESI-MS peptide fingerprinting of snake venoms coupled with PCA is a useful tool for identifying venoms and for taxonomic analyses.

Cross-neutralization of the neurotoxicity of Crotalus durissus terrificus and Bothrops jararacussu venoms by antisera against crotoxin and phospholipase A2 from Crotalus durissus cascavella venom

We have previously demonstrated that rabbit antisera raised against crotoxin from Crotalus durissus cascavella venom (cdc-crotoxin) and its PLA2 (cdc-PLA2) neutralized the neurotoxicity of this venom and its crotoxin. In this study, we examined the ability of these antisera to neutralize the neurotoxicity of Crotalus durissus terrificus and Bothrops jararacussu venoms and their major toxins, cdt-crotoxin and bothropstoxin-I (BthTX-I), respectively, in mouse isolated phrenic nerve-diaphragm preparations. Immunoblotting showed that antiserum to cdc-crotoxin recognized cdt-crotoxin and BthTX-I, while antiserum to cdc-PLA2 recognized cdt-PLA2 and BthTX-I. ELISA corroborated this cross-reactivity. Antiserum to cdc-crotoxin prevented the neuromuscular blockade caused by C. d. terrificus venom and its crotoxin at a venom/crotoxin:antiserum ratio of 1:3. Antiserum to cdc-PLA2 also neutralized the neuromuscular blockade caused by C. d. terrificus venom or its crotoxin at venom or toxin:antiserum ratios of 1:3 and 1:1, respectively. The neuromuscular blockade caused by B. jararacussu venom and BthTX-I was also neutralized by the antisera to cdc-crotoxin and cdc-PLA2 at a venom/toxin:antiserum ratio of 1:10 for both. Commercial equine antivenom raised against C. d. terrificus venom was effective in preventing the neuromuscular blockade typical of B. jararacussu venom (venom:antivenom ratio of 1:2), whereas for BthTX-I the ratio was 1:10. These results show that antiserum produced against PLA2, the major toxin in C. durissus cascavella venom, efficiently neutralized the neurotoxicity of C. d. terrificus and B. jararacussu venoms and their PLA2 toxins.

Anti-sera raised in rabbits against crotoxin and phospholipase A2 from Crotalus durissus cascavella venom neutralize the neurotoxicity of the venom and crotoxin

Crotoxin, the principal neurotoxin in venom of the South American rattlesnakes Crotalus durissus terrificus and Crotalus durissus cascavella, contains a basic phospholipase A2 (PLA2) and an acidic protein, crotapotin. In this work, we examined the ability of rabbit anti-sera against crotoxin and its PLA2 subunit to neutralize the neurotoxicity of venom and crotoxin from C. d. cascavella in mouse phrenic nerve-diaphragm and chick biventer cervicis preparations. Immunoblotting showed that the anti-sera recognized C. d. cascavella crotoxin and PLA2. This was confirmed by ELISA, with both anti-sera having end-point dilutions of 3 x 10(-6). Anti-crotoxin serum neutralized the neuromuscular blockade in phrenic nerve-diaphragm muscle preparations at venom or crotoxin:anti-serum ratios of 1:2 and 1:3, respectively. Anti-PLA2 serum also neutralized this neuromuscular activity at a venom or crotoxin:anti-serum ratio of 1:1. In biventer cervicis preparations, the corresponding ratio for anti-crotoxin serum was 1:3 for venom and crotoxin, and 1:1 and 1:2 for anti-PLA2 serum. The neutralizing capacity of the sera in mouse preparations was comparable to that of commercial anti-serum raised against C. d. terrificus venom. These results show that anti-sera against crotoxin and PLA2 from C. d. cascavella venom neutralized the neuromuscular blockade induced by venom and crotoxin in both nerve-muscle preparations, with the anti-serum against crotoxin being slightly less potent than that against crotoxin.

Clinical trial of two antivenoms for the treatment of Bothrops and Lachesis bites in the north eastern Amazon region of Brazil

The efficacies of specific Bothrops atrox-Lachesis and standard Bothrops-Lachesis antivenoms were compared in the north eastern Amazon region of Brazil. The main aim was to investigate whether a specific antivenom raised against the venom of B. atrox, the most important Amazon snake species from a medical point of view, was necessary for the treatment of patients in this region. Seventy-four patients with local and systemic effects of envenoming by Bothrops or Lachesis snakes were randomly allocated to receive either specific (n = 38) or standard (n = 36) antivenoms. In 46 cases (24 in the standard antivenom group, 22 in the other) the snake was identified either by enzyme immunoassay or by examination of the dead snake, as B. atrox in 45, L. muta in one. Patients were similar in all clinical and epidemiological respects before treatment. Results indicated that both antivenoms were equally effective in reversing all signs of envenoming detected both clinically and in the laboratory. Venom-induced haemostatic abnormalities were resolved within 24 h after the start of antivenom therapy in most patients. The extent of local complications, such as local skin necrosis and secondary infection, was similar in both groups. There were no deaths. The incidence of early anaphylactic reactions was 18% and 19%, respectively for specific and standard antivenoms; none was life-threatening. Measurement of serum venom concentrations by enzyme immunoassay (EIA) confirmed that both antivenoms cleared venom antigenaemia effectively. EIA also revealed that one patient had been bitten by Lachesis muta, although the clinical features in this case were not distinctive.

Lachesis muta muta venom: immunological differences compared with Bothrops atrox venom and importance of specific antivenom therapy

Lachesis muta muta and Bothrops atrox snakes are responsible for most accidents occurring in the Amazon. The clinical features of the accidents are similar; however, there are still controversies about the efficacy of Bothrops antivenoms for treating L. m. muta accidents. In this work, we evaluated the antigenic cross-reactivity between these venoms using polyclonal and monoclonal antibodies and the efficacy of B. atrox and L. m. muta experimental antivenoms in cross-neutralizing the main toxic activities of each venom. Electrophoretic patterns differed consistently between the species. However, antigenic cross-reactivity was extensive except for a few bands. Several species-specific monoclonal antibodies were obtained by immunization of Balb/c mice with L. m. muta whole venom or B. atrox and L. m. muta specific antigens. The monoclonal antibodies specific to L. m. muta recognized different bands of this venom and the antibodies specific to B. atrox recognized a complex pattern on whole venom by Western blotting. These antibodies are important tools for developing an immunoassay able to discriminate patients bitten by these snakes. The experiments involving cross-neutralization of the main activities of the venoms showed that hemorrhage and blood incoagulability induced by B. atrox venom were similarly neutralized by both B. atrox and L. m. muta antivenoms. However, B. atrox antivenom partially neutralized the hemorrhage and completely failed in neutralizing coagulopathy induced by L. m. muta venom. Therefore, antigenic variation between B. atrox and L. m. muta venoms does occur and the use of specific antivenom is suggested for patients bitten by Lachesis snakes.

Aspectos epidemiológicos e clínicos dos acidentes ofídicos ocorridos nos municípios do Estado do Amazonas

No Amazonas, o acidente ofídico é um problema de saúde pública pouco conhecido. Por este motivo, foi realizado um estudo descritivo dos acidentes ofídicos atendidos nas Unidades de Saúde de 34 municípios, um distrito e dois pelotões de fronteira do Estado do Amazonas. As características mais comuns encontradas dentre os pacientes foram: agricultor (50,4%), do sexo masculino (81,3%), em idade produtiva (72,1%), picado no membro inferior (88,5%), por jararaca (48,6%) ou surucucu (46,8%), na zona rural de seu município (70,2%) e que só recebeu atendimento médico em tempo superior a seis horas, após acidente (57,3%). As manifestações locais mais freqüentes foram: edema (76,9%), dor (68,7%), eritema (10,2%) e hemorragia (9,3%). Hemorragia (18,8%) foi a manifestação sistêmica mais freqüente. O antiveneno foi administrado em apenas 65,9% dos pacientes. A via mais utilizada foi a endovenosa (52,3%), sendo relevante o uso de vias não mais recomendadas (47,7%). O antiveneno administrado, na maioria dos pacientes, foi o antibotrópico (66,7%). As complicações mais freqüentes foram abcesso (13,7%), necrose (12,3%), infecção secundária (8,3%), insuficiência renal (2,5%) e gangrena (2,5%). Os procedimentos médicos mais usados para o tratamento das complicações foram: drenagem (52,6%), debridamento (28,9%), amputação (10,5%), limpeza cirúrgica (5,3%) e diálise peritoneal (2,6%). A letalidade foi de 1%.

ELISA for the detection of venoms from four medically important snakes of India

A double antibody sandwich enzyme linked immunosorbent assay (ELISA) was developed to detect Echis carinatus venom in various organs (brain, heart, lungs, liver, spleen and kidneys) as well as tissue at the site of injection of mice, at various time intervals (1, 6, 12, 18, 24 h and 12 h intervals up to 72 h) after death. The assay could detect E. carinatus venom levels up to 2.5 ng/ml of tissue homogenate and the venom was detected up to 72 h after death. A highly sensitive and species-specific avidin-biotin microtitre ELISA was also developed to detect venoms of four medically important Indian snakes (Bungarus caeruleus, Naja naja, E. carinatus and Daboia russelli russelli) in autopsy specimens of human victims of snake bite. The assay could detect venom levels as low as 100 pg/ml of tissue homogenate. Venoms were detected in brain, heart, lungs, liver, spleen, kidneys, tissue at the bite area and postmortem blood. In all 12 human victim cadavers tested the culprit species were identified. As observed in mice, tissue at the site of bite area showed the highest concentration of venom and the brain showed the least. Moderate amounts of venoms were found in liver, spleen, kidneys, heart and lungs. Development of a simple, rapid and species-specific diagnostic kit based on this ELISA technique useful to clinicians is discussed.

Tests for detection of snake venoms, toxins and venom antibodies: review on recent trends (1987-1997)

Various methods developed for the detection of snake venoms, toxins and venom antibodies, during the last decade is reviewed. Radioimmunoassay, agglutination assay, enzyme-linked immunosorbent assay (ELISA), fluorescence immunoassay etc. have been used for detection of venoms and toxins. Important contributions have been made to improve the specificity, sensitivity, rapidity and simplicity of the ELISA method. Monoclonal antibodies and affinity-purified venom-specific antibodies were used to achieve species specificity of ELISA and the latter seems to be the ideal for venom detection. Incorporation of avidin-biotin system as well as the fluorogenic substrate in the enzyme immunoassay sufficiently increased the sensitivity of the assay to detect venom concentrations to picogram levels. The ability to use undiluted blood and other whole biological fluids reduce the assay time considerably. Although there have been several reports were on venom detection, so far only a few field kits have been developed. This implies that the experiments and design were only at the laboratory levels and still more work has to be carried out before it could be used in the field. Concerning the venom antibody detection, ELISA has been used extensively and the humoral response of patients envenomed by snake has been investigated in detail. Non-specific reactivity along with cross-reactivity still limits the use of ELISA for species identification in epidemiological studies. Overall, ELISA remains the suitable method for the detection of snake venoms, toxins and venom antibodies in body fluids. The possible use of a biosensor approach to solve some of the problems associated with the ELISA method are also discussed.

ELISA for the detection of venom antigens in experimental and clinical envenoming by Loxosceles intermedia spiders

Enzyme linked immunosorbent assays (ELISA) were developed to detect antigens from Loxosceles intermedia spider venom. Hyperimmune horse anti-Loxosceles intermedia IgGs were prepared by immunoaffinity chromatography and used to set up a sandwich-type ELISA. The specificity of the assay was demonstrated by its capacity to correctly discriminate the circulating antigens in mice that were experimentally inoculated with L. intermedia venom from those inoculated with L. gaucho, L. laeta, and Phoneutria nigriventer spider venoms, Tityus serrulatus scorpion venom and Bothrops jararaca, Crotalus durissus terrificus, Lachesis muta muta and Micrurus frontalis snake venoms. Measurable absorbance signals were obtained with 0.8 ng of venom per assay. The ELISA also detected antigens in the sera of patients envenomed by L. intermedia. Therefore, after standardization for clinical use this ELISA may be a valuable tool for clinicians and epidemiologists.

Venom variability among several Tityus serrulatus specimens

Individual differences in venom composition among several Tityus serrulatus specimens collected in the same area were examined by enzyme-linked immunosorbent assay (ELISA). Polyclonal antibodies raised against whole venom and against the alpha-type (toxin IV-5 or Ts IV) and the beta-type toxin (toxin gamma or Ts VII) were used to study specific variations in the venom. The ELISA results indicated clear differences among the scorpion venoms examined. The lethality (LD50) determined by subcutaneous injections of pooled venom with the same characteristics showed an interesting correlation between the expression level of each component studied and the lethal effect of the venom. Among the groups analysed, the group with the highest concentration of alpha-type toxin showed the highest toxicity. The groups with the lowest level of toxicity were those with a low concentration of alpha-type toxin. The results show that the lethality of the venom varies from specimen to specimen and suggest that alpha-type toxin must be the major lethal component in the whole venom.

An enzyme-linked immunosorbent assay (ELISA) that discriminates between the venoms of Brazilian Bothrops species and Crotalus durissus

Enzyme-linked immunosorbent assays (ELISAs) were developed to detect specific antigens from Bothrops sp. and Crotalus durissus snake venoms in Brazil. Cross-reactive immunoglobulins from hyperimmune horse anti-Bothrops and anti-Crotalus sera were removed by immunoaffinity chromatography. Specific IgGs for Bothrops sp. and C. durissus venom antigens were prepared and used to set up a sandwich-type ELISA. The specificity of the assay was demonstrated by its capacity to identify correctly the circulating antigens in mice experimentally inoculated with both venoms. Measurable absorbance signals were obtained with 5 ng of venom per assay. The ELISA was also used to identify circulating antigens in the sera of humans bitten by Bothrops sp. and C. durissus. These ELISAs could be valuable for clinicians and epidemiologists if they prove to have both the high sensitivity and specificity required for such tests.

Body distribution of Tityus serrulatus scorpion venom in mice and effects of scorpion antivenom

In the present study we report the distribution of Tityus serrulatus scorpion venom in serum and various tissues of CFI mice and the efficacy of antivenom in reducing venom concentration. The animals were injected s.c. with 10 micrograms of scorpion venom, divided into groups of four animals and killed at different times from 15 min to 24 hr. Blood samples and samples of different tissues (heart, lung, liver, kidney, spleen, brain and injection site) were collected. Maximum venom levels occurred at 15 min in the kidney and liver and at 30 min in serum, lung, heart and spleen. After 2 hr the venom decreased rapidly in serum and in all other organs until venom levels were no longer detectable after 8 hr. No venom was detected in the central nervous system. In another experiment, 10 microliters of scorpion antivenom was injected i.v. together with the venom, and a rapid reduction of venom concentration was observed in the blood and tissues. In the third experiment, anti-scorpion venom was injected i.v. 1 hr after venom administration, and partial reduction of venom concentration was detected in tissues (lung and kidney). These studies contribute to the elaboration of more objective treatment that may result in a more economic, efficient and controlled use of scorpion antivenom in stings involving humans.

Characterization of a hemorrhagic factor, LHF-I, isolated from the bushmaster snake (Lachesis muta muta) venom

Hemorrhagic factor I (LHF-I) was previously purified from the venom of the bushmaster snake (Lachesis muta muta). In terms of biochemical and immunological properties, LHF-I is a glycoprotein (mol. wt 100,000, pI 4.7) consisting of two subunits; it loses its activity following mercaptoethanol treatment. LHF-I contains 0.7 g-atom zinc and 1.2 g-atom calcium per mole protein. The hemorrhagic and the proteinase activities are inhibited by EDTA; subsequent addition of Ca2+ or Mg2+ does not reverse the EDTA-induced inhibition of the hemorrhagic activity. The metalloenzyme does not hyrolyze arginine esters and is devoid of phospholipase A2 activity. It hydrolyzes the A alpha- > B beta-chain of fibrinogen without clot formation and hydrolyzes selectively the alpha-chain of fibrin, leaving the B beta- and tau-chains unaffected. Antibodies to the hemorrhagic factor in bushmaster venom were produced by immunizing rabbits with the purified protein. The antibody was purified by protein-A affinity chromatography. This antibody was also used to screen other Crotalinae venom samples for immunologically similar epitopes by ELISA assay. The purified antibody reacted only with LHF-I and two samples of bushmaster venom from different geographical locations.

ELISA for the detection of toxic antigens in experimental and clinical envenoming by Tityus serrulatus scorpion venom

An ELISA was developed for identification of circulating toxic antigens from Tityus serrulatus scorpion venom. The toxic fraction from the scorpion venom was purified by Sephadex G-50 chromatography and immunoaffinity techniques were used for identifying antibodies that reacted with this fraction. These antibodies were used to develop a sandwich-type ELISA. The specificity of the assay was demonstrated by its capacity for identifying mice that were experimentally inoculated with T. serrulatus venom from those inoculated with Phoneutria nigriventer spider venom, Apis mellifera bee venom and Bothrops atrox, Crotalus durissus terrificus, Lachesis muta muta and Micrurus frontalis snake venoms. Measurable absorbance signals were obtained with 0.1 ng of venom per assay. The ELISA also detected antigens in the sera of patients systemically envenomed by T. serrulatus. Therefore, this ELISA could be a valuable tool for clinicians and epidemiologists, owing to its sensitivity and specificity.