Bothrops atrox venom: Biochemical properties and cellular phenotypes of three highly toxic classes of toxins

Snake venoms have a complex mixture of compounds that are conserved across species and act synergistically, triggering severe local and systemic effects. Identification of the toxin classes that are most damaging to cell homeostasis would be a powerful approach to focus on the main activities that underpin envenomation. Here, we focus on the venom of Bothrops atrox, snake responsible for most of the accidents in Amazon region of South America. We identified the key cytotoxic toxin fractions from B. atrox venom and mapped their biochemical properties, protein composition and cell damage. Five fractions were obtained by mass exclusion chromatography and contained either a single class of enzymatic activity (i.e., L-amino acid oxidases or Hyaluronidases) or different activities co-distributed in two or more protein fractions (e.g., Metalloproteinases, Serine Proteases, or Phospholipases A2). Only three protein fractions reduced cell viability of primary human cells. Strikingly, such activity is accompanied by disruption of cell attachment to substratum and to neighbouring cells. Such strong perturbation of morphological cell features indicates likely defects in tissue integrity in vivo. Mass spectrometry identified the main classes of toxins that contribute to these phenotypes. We provide here a strategy for the selection of key cytotoxic proteins for targeted investigation of their mechanism of action and potential synergism during snakebite envenomation. Our data highlights putative toxins (or combinations of) that may be the focus of future therapeutic interference.

A Validation Study of the Limulus Amebocyte Lysate Test as an End-Product Endotoxin Test for Polyvalent Horse Snake Antivenom

The only definitive management of snake envenoming is the use of snake antivenom. Endotoxin contamination is a serious threat to the safe use of parenteral drugs. A greater understanding of the nature of limulus amebocyte lysate (LAL) test interference and use of permissible dilutions has minimized enhancement problems. Common interference issues include suboptimal pH, enzyme or protein modification, and nonspecific LAL activation. This study aimed at determining the interference factors associated with validating the antivenom sera preparations to avoid false-positive results when testing snake antivenom serum samples by the LAL method. Phase I (preliminary screening/interference assay) was performed to determine a compatible test dilution, which was then used in Phase II (inhibition-enhancement/validation study). The best approach to resolve interference issues was dilution by 1:80 (maximum valid dilution) plus a specific treatment as heat-activation at 70°C-80°C for 10 min with rehydration of LAL reagent with endotoxin-specific buffer solution.LAY ABSTRACT: Snake antivenom sera are produced by immunizing horses with repeated nonlethal doses of snake venom. Bacterial endotoxins constitute one of the major problems in the formulation of pharmaceutical products. One such method for detecting endotoxin levels is the bacterial endotoxin test (BET). However, some substances show strong interfering action with the BET that cannot be avoided by simply diluting the sample solution. In this work, the test for interfering factors was performed as two identical series of product dilutions-one spiked with 2λ and one left unspiked. The result of the interference test revealed the noninterfering dilution (NID) of the product, which was used for the actual validation. Our results showed that after treating the samples using different procedures, such as heat activation at 70-80°C for 10 min followed by centrifugation at 2000 rpm for 10 min and dilution of samples in BD100 (biodispersing agent), inhibition and enhancement up to 1:100 maximum valid dilution (MVD) were observed. Finally, to resolve this inhibition/enhancement problem, the activated sample was heated at 70-80°C for 10 min with rehydration of the Endosafe LAL reagent in an endotoxin-specific buffer solution (BG120) to block β-d-glucans and limulus amebocyte lysate (LAL) reactive material (LAL-RM).

Anti-scorpion venom activity of Thapsia garganica methanolic extract: Histopathological and biochemical evidences

ETHNOPHARMACOLOGICAL RELEVANCE

Thapsia garganica, is a herbal medicine traditionally used as diuretic, emetic and purgative. It is also used as anti-scorpion venom in Morocco; however, its protective effects against scorpion venom remain elusive.

AIM OF THE STUDY

The present study was undertaken to evaluate anti-venom activity of T. garganica in vivo through histological and biochemical studies.

MATERIALS AND METHODS

Methanolic leaves extract of T. garganica was evaluated for anti-venom activity against buthus. occitanus under in vivo conditions. Histopathological and biochemical changes in envenomed and treated mice were also examined. Phytochemical screening was conducted to estimate the major constituents whereas DPPH, β -Carotene-linoleic acid and reducing power assays were performed to evaluate the anti-oxidant activity of T. garganica extract.

RESULTS

Methanolic leaves extract of T. garganica (2g/kg) increased the survival time (> 18h) of mice injected with lethal doses of B. occitanus venom, with remarkable recovery of histology damage. Furthermore T. garganica induced a significant decreased of biochemical markers of kidney, liver and heart function. Phytochemistry screening revealed the presence of phenolic compounds, flavonoids, tannins and steroids/terpenoids, which might explain the bioactivity of the extract. It was also shown that the extract has an exceptionally high antioxidant activity compared to well-known antioxidants used as standards.

CONCLUSION

The present study provides strong evidence that support the use of T. garganica as anti-scorpion venom in traditional medicine in Morocco. However, additional studies are required to isolate and identify the metabolites responsible for the activity.

General characterization of Tityus fasciolatus scorpion venom. Molecular identification of toxins and localization of linear B-cell epitopes

This communication describes the general characteristics of the venom from the Brazilian scorpion Tityus fasciolatus, which is an endemic species found in the central Brazil (States of Goiás and Minas Gerais), being responsible for sting accidents in this area. The soluble venom obtained from this scorpion is toxic to mice being the LD50 is 2.984 mg/kg (subcutaneally). SDS-PAGE of the soluble venom resulted in 10 fractions ranged in size from 6 to 10-80 kDa. Sheep were employed for anti-T. fasciolatus venom serum production. Western blotting analysis showed that most of these venom proteins are immunogenic. T. fasciolatus anti-venom revealed consistent cross-reactivity with venom antigens from Tityus serrulatus. Using known primers for T. serrulatus toxins, we have identified three toxins sequences from T. fasciolatus venom. Linear epitopes of these toxins were localized and fifty-five overlapping pentadecapeptides covering complete amino acid sequence of the three toxins were synthesized in cellulose membrane (spot-synthesis technique). The epitopes were located on the 3D structures and some important residues for structure/function were identified.

Immunoreactivity and two-dimensional gel-electrophoresis characterization of Egyptian cobra venom proteome

The first and second (two) dimensional gel electrophoresis has a broad protein resolution power. It was used to separate and identify cobra venom proteome. The importance of characterizing venom proteins contents from the Egyptian elapidae, specifically neurotoxins, is based on the need to produce effective anti-venom. About 30-55distinct protein spots were identified on silver stained two-dimensional gels. Around two-thirds of the venom proteins displayed low a molecular weight and a migration into hydrophobic side. The venoms from Naja haja and Naja nigricollus showed 45-55 spots, while Walternnesia aegyptia had less (31-37) spots. The commercial prepared polyclonal antivenom had a strong signal for anionic and cationic venom protein spots with molecular weight 20-115 kDa. However, it showed weak or non immunoreactivity toward anionic low molecular weight spots (2.5-15 kDa). These results suggest the need to change the immunization schedule to include low molecular weight toxin-proteomes as separate dose or sequester injection.

Inhibitory effect of the plant Clusia fluminensis against biological activities of Bothrops jararaca snake venom

The ability of extracts of the plant Clusia fluminensis Planch & Triana (Clusiaceae Lindl.) to neutralize proteolysis, clotting, hemolysis, hemorrhagic and lethality activities of Bothrops jararaca snake venom was studied. Clusianone and lanosterol from the flower and fruit extracts, respectively, were also tested. The extracts of different organs of C. fluminensis inhibited proteolysis and hemolysis induced by B. jararaca venom, but with different potencies. Only the stems prevented blood clotting. Only the acetone extract of the fruit protected mice from hemorrhage while the acetone or methanol extracts prevented mice from death. Clusianone and lanosterol did not inhibit clotting or hemorrhage, but the former inhibited proteolysis and the latter hemolysis.

Development of passive haemagglutination (PHA) and haemagglutination inhibition (HAI) technique for potency estimation of Cobra Antisnake Venom Serum (ASVS)

Antibodies against snake venom or antivenom potency are assayed quantitatively by in-vivo neutralization test in mice, which requires large number of laboratory animals. In potency assays of biological substances such as antivenoms, it is highly desirable to avoid suffering and death of animals by substituting in-vivo method with in-vitro methods, provided such methods measure life-saving capability with precision similar to that of in-vivo method. The in-vitro tests determine the neutralizing power of antivenom by permitting the evaluation of a particular biological activity of the venom and its neutralization after mixing the venom with the antivenom [Theakston RDG, Reid HA. Development of simple standard assay procedures for the characterization of snake venom. Bull WHO 1983;61:949-956; Gutierrez JM, Rojas G, Lomonte B, Gene JA, Chaves F, Alvarado J, et al. Standardizing of assays for testing the neutralizing ability of antivenoms. Toxicon 1990;28:1127-1129; Theakston R.D.G. Comments on letter of Gutierrez et al. on standardization of assays for testing the neutralizing ability of antivenoms. Toxicon 1990;28:1131-1132; Harvey AL, Barfaraz A, Thomson E, Faiz A, Preston S, Harris JB. Screening of snake venom for neurotoxic and myotoxic effects using simple in-vitro preparation from rodents and chicks. Toxicon 1994;32:257-265; World Health Organization Progress in characterization of venom and standardization of anti-venoms. Geneva: WHO offset publication; 1981. p. 58.]. Hence, the ideal requirements for an assay in detecting venom and venom antibody include high level of sensitivity, specificity (ability to differentiate between venom and venom antibody produced by closely related species of snakes), reproducibility and simplicity. A new in-vitro procedure for quantitative analysis of potency of ASVS by passive haemagglutination (PHA) and haemagglutination inhibition (HAI) has been explored. The methods described are simple, rapid, economical, reproducible and useful in replacing the more expensive in-vivo neutralization assays. Moreover, it also eliminates the use of laboratory animals.

Enzyme immunoassays in brown snake (Pseudonaja spp.) envenoming: Detecting venom, antivenom and venom–antivenom complexes

Although a commercial snake venom detection kit (SVDK) is available to distinguish between the five major snake groups in Australia, there is no assay for quantifying venom or antivenom concentrations in envenomed patients. Serum samples were obtained from patients with brown snake (Pseudonaja spp.) envenoming before and after the administration of antivenom and patients with suspected brown snake bites but no evidence of envenoming. Enzyme immunoassays (EIAs) were developed for free venom, free antivenom and the venom-antivenom complex. Standard samples measured in duplicate had a coefficient of variation of less than 10%. The EIA for venom was able to detect brown snake venom down to concentrations of 3 ng/mL. A high baseline absorbance was measured in some patients that did not change with the addition of excess antivenom to the samples. In these patients, the baseline absorbance was subtracted from all measurements to calculate the true venom concentration. The EIA for brown snake antivenom had a limit of detection of 20 microg/mL, but 50 microg/mL was used as a cut-off based on assays in patients who had not received antivenom. The EIA for venom-antivenom complexes was unable to detect these at the low venom concentrations that occurred in patients. Quantification of venom and antivenom will help to determine the dose of antivenom required to bind venom and to establish appropriate end points for antivenom treatment.

Assessment of the viral safety of antivenoms fractionated from equine plasma

Antivenoms are preparations of intact or fragmented (F(ab′)₂ or Fab) immunoglobulin G (IgG) used in human medicine to treat the severe envenomings resulting from the bites and stings of various animals, such as snakes, spiders, scorpions, or marine animals, or from the contact with poisonous plants. They are obtained by fractionating plasma collected from immunized horses or, less frequently, sheep. Manufacturing processes usually include pepsin digestion at acid pH, papain digestion, ammonium sulphate precipitation, caprylic acid precipitation, heat coagulation and/or chromatography. Most production processes do not have deliberately introduced viral inactivation or removal treatments, but antivenoms have never been found to transmit viruses to humans. Nevertheless, the recent examples of zoonotic diseases highlight the need to perform a careful assessment of the viral safety of antivenoms.

This paper reviews the characteristics of equine viruses of antivenoms and discusses the potential of some manufacturing steps to avoid risks of viral contamination. Analysis of production parameters indicate that acid pH treatments and caprylic acid precipitations, which have been validated for the manufacture of some human IgG products, appear to provide the best potential for viral inactivation of antivenoms. As many manufacturers of antivenoms located in developing countries lack the resources to conduct formal viral validation studies, it is hoped that this review will help in the scientific understanding of the viral safety factors of antivenoms, in the controlled implementation of the manufacturing steps with expected impact on viral safety, and in the overall reinforcement of good manufacturing practices of these essential therapeutic products.

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.

Effect of heating on the toxic, immunogenic and immunosuppressive activities of Crotalus durissus terrificus venom

The venom of South American rattlesnake Crotalus durissus terrificus is very toxic but poorly immunogenic and it has an immunosuppressive ability. The heating of venom at 56, 70 or 100 degrees C for 30 min caused a diminution in the lethal, phospholipase A(2) and myotoxic activities. SDS-PAGE analysis of the heated venom showed that the proteins of higher molecular weights were the most affected by heating whereas proteins with lower molecular weights (20,000-14, 000) were the most resistant to heating. The immunosuppressive effect was studied in mice immunized with human serum albumin (HSA) 1 h after receiving either heated venom or heated crotoxin. The heating of venom at 70 or 100 degrees C reduced its immunosuppressive effect whereas crotoxin had its suppressive effect reduced only when heated at 100 degrees C. The heating of venom at 56, 70 or 100 degrees C did not change its immunogenicity. These results suggest that heat treatment may be a useful technique to help in the production of antiserum to crotalid venom.

Antibodies against Tityus discrepans venom do not abolish the effect of Tityus serrulatus venom on the rat sodium and potassium channels

Anti-(Tityus serrulatus + Tityus bahiensis) and anti-Tityus discrepans venom polyclonal antisera were used to investigate whether antigenic differences exist between the venoms of the Brazilian T. serrulatus and the Venezuelan T. discrepans scorpions. Both antisera recognised the toxin-containing electrophoretic fractions of their cognate venoms and also those from Tityus zulianus and Tityus trinitatis venoms on Western blots. The anti-T. discrepans antiserum reacted only weakly with T. serrulatus toxic polypeptides. The effect of T. serrulatus alpha- or beta-toxins on rat skeletal muscle Na+ channels expressed in Xenopus laevis oocytes was abolished by pre-incubating the venom with anti-(T. serrulatus + T. bahiensis) serum but not with anti-T. discrepans serum. Nor did the Brazilian or the Venezuelan sera prevent the reduction in K+ currents by T. serrulatus venom in X. laevis oocytes expressing the rat brain delayed rectifying Shaker K+ channel (Kv1.2). These results indicate that toxins from T. serrulatus and T. discrepans venoms, which primarily target mammalian Na+ channels, are antigenically distinct, although they probably share common epitopes. Our results also suggest that Na+ channel-active toxins are the immunodominant antigens of the T. serrulatus venom.

Treatment of snake bites by Bothrops species and Lachesis muta in Ecuador: laboratory screening of candidate antivenoms

Bothrops xanthogrammus/asper, B. atrox and Lachesis muta are probably responsible for most cases of severe envenoming in Ecuador. In recent years, the most widely used antivenom ('Myn' Ronti, imported from Mexico) has proved clinically ineffective. There is an urgent need to identify an effective alternative for clinical testing. Five antivenoms with activity against Bothrops venoms were compared using standard World Health Organization rodent and in vitro assays: (i) 'Myn', Ronti Mexico SA ('B. atrox', 'Crotalus terrificus'), (ii) Instituto Butantan (Bothrops polyvalent, Brazil), (iii) Instituto Nacional de Hygiene y Medicina Tropical (Bothrops polyvalent, Ecuador), (iv) Instituto Nacional de Salud (B. asper, C. durissus and Lachesis muta, Colombia), and (v) Laboratorios Probiol (Bothrops, Lachesis and Crotalus, Colombia). The venoms against which these antivenoms were tested were Ecuadorian B. atrox, B. asper and B. xanthogrammus. Brazilian antivenom proved to be the most effective, followed by the Ecudorian and Colombian antivenoms. Mexican antivenom was completely ineffective in neutralizing the lethal effects of Ecuadorian Bothrops venoms. Monospecific Brazilian L. muta antivenom (Instituto Butantan) proved effective against Ecuadorian L. muta venom, but the Colombian polyspecific antivenoms did not. Clinical trials of Brazilian and Ecuadorian antivenoms are planned in the Amazon region of Ecuador in the near future.

Detection and neutralization of B. jararaca venom in mice

1. Bothrops jararaca venom was detected by ELISA at different times in the skin, muscle, blood, liver, lung, heart, kidney and spleen of mice injected with venom i.m. or i.d. 2. The results showed that even 10 min after i.m. injection the venom is detected mostly in skin rather than in the muscle of the venom injection site. A small amount of venom was detected in the kidney up to 12 h after im venom injection, and none was detected in tissues of lung, heart, liver or spleen. 3. However, in mice injected i.d., the venom could be detected in the skin up to 24 h after injection. Local necrosis and haemorrhage could be neutralized by antivenom injected by the i.d. or i.v. routes only if the antivenom was given a short time after venom injection, even when antivenom is administered in high concentration. 4. In contrast, experiments performed in mice receiving venom i.d. and treated by i.d. or i.v. routes with antivenom injected at different times after envenoming showed that the effect of venom on blood coagulation could be counteracted by antivenom administered by either route up to 2 h after venom injection. 5. We suggest that a feasible amount of antivenom administered i.d. could be given as a first aid measure after a snake bite accident. However, further experimental studies using the i.d. route for antivenom administration are essential to confirm this possibility.

[The effect of Habu toxoid--from the view point of public health center]

In order to clarify the effect of Habu Toxoid, serum sampling was performed with from July 1990 to February 1991, on 503 vaccinated subjects living in Amami Islands by staff of Naze health center. Sera were analyzed by Enzyme Linked Immunosorbent Assay (ELISA) for levels of serum antitoxin to venom, both anti-Hemorrhagic Factor 1 (anti-HR1) and anti-Hemorrhagic Factor 2 (anti-HR2). Information on vaccinated subjects-age, sex, occupation, vaccination date, frequency, period and interval of vaccinations, years after final vaccination and past history of Habu bites-was obtained and analyzed with relation to serum antitoxin levels. The following results were obtained: 1) Serum antitoxin levels, both anti-HR1 and anti-HR2, of the Habu bitten group (N = 47) were significantly higher than that of the unbitten group (N = 456). This finding suggests that crude Habu venom injected by bites elevated the levels. Regardless of past history of Habu bites, levels of antibody to HR2 was significantly lower than that to HR1. 2) Among the unbitten group, detection of antitoxin was related to subjects' attributes. Production of antitoxin was related to being male, high frequency of vaccinations, long period of vaccinations and short period after final vaccination. 3) Among the unbitten group, anti-HR2 was found in high levels with the following factors: high frequency of vaccinations and short period after final vaccination. However among the well-vaccinated group (N = 153), differences in antitoxin levels by vaccination frequency were not recognized.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunization against Echis ocellatus (carpet viper) venom using liposomes incorporating immunostimulants: role of lipopolysaccharide in conferring protection in a mouse model

Varying doses of whole West African Echis ocellatus venom were incorporated, with or without immunostimulants, into membrane-stabilized reverse phase evaporation (REV) liposomes. Preparations were given either subcutaneously (s.c.) or intravenously (i.v.) to mice and the immune responses compared. Addition of lipopolysaccharide (LPS) significantly increased the venom antibody response. Lipid A produced a less pronounced and less sustained effect and the addition of muramyl dipeptide analogues made no significant contribution to the antibody response. The protective ability of circulating venom antibodies was assessed by challenging the immunized mice with a minimum lethal dose of whole venom after 175 days. A dose of 250 micrograms E. ocellatus venom + 300 micrograms LPS in REVs injected s.c. conferred the highest protection against lethal venom effects. Orally administered venom/liposomes incorporated with the mucosal adjuvant avridine primed the antibody response and produced a classic secondary response following a sublethal boost of whole venom. Single injections of venom or venom fraction/liposome preparations which produce a high and sustained immune response have potential in commercial antivenom production and in active immunization of man in areas of high snakebite incidence and mortality.

Species-specific detection of venom antigens from snakes of the Bothrops and Lachesis genera

Venom-insoluble adsorbents were employed to absorb out the cross-reacting antibodies from monovalent polyclonal antivenoms. The absorbed antivenoms were tested by enzyme-linked immunosorbent assay against homologous and heterologous venoms and showed species-specificity throughout a range of venom concentrations. The same absorbed antisera were used in immunoblots under non-reducing conditions as probes to reveal species-specific antigens. In all cases studied this was achieved. The range of mol. wts of specific antigens was between 20,000 and 120,000, approximately. Venoms added to human serum experimentally were specifically detected by their homologous absorbed antivenom antibodies. The work here described could be important in the development of diagnostic assays for envenomings involving snakes from the Bothrops and Lachesis genera.

The use of enzyme-linked immunosorbent assay for the quantitation of Calloselasma rhodostoma (Malayan pit viper) venom and venom antibodies

The specificity and sensitivity of an indirect and two (an 'ordinary' and a 'rapid') double sandwich enzyme-linked immunosorbent assay (ELISA) procedures for the quantitation of Calloselasma rhodostoma (Malayan pit viper) venom were examined. The three assays were equally sensitive and the accuracy of the assays was not substantially affected by individual variation in the venom composition. The specificity of the assays was examined against 26 venoms from snakes of the families Viperidae and Elapidae. While the double sandwich ELISA procedures were sufficiently specific to be used in the clinical immunodiagnosis of C. rhodostoma bite in Malaysia, the indirect ELISA procedure exhibited extensive cross-reactivity with other Malaysian pit viper venoms. Attempts were made to improve the specificity of the indirect ELISA procedure for the quantitation of C. rhodostoma venom. A 'low ELISA cross-reactivity' venom fraction (termed VF52) was isolated from C. rhodostoma venom by repeated Sephadex G-100 gel filtration chromatography. The indirect ELISA procedure using antibodies to VF52 as immunoreagent showed an improvement in specificity. The use of the indirect ELISA procedure for the detection of C. rhodostoma antibodies was also examined and the results show that the assay was sufficiently specific to be used for retrospective diagnosis of C. rhodostoma bite in Malaysia, in particular when VF52 was used as the coating antigen.

Comparison of the purity and efficacy of affinity purified avian antivenoms with commercial equine crotalid antivenoms

Antivenoms were raised in laying hens by repeated immunizations with detoxified crotalid snake venoms and purified from egg yolks by affinity chromatography. While the affinity purified avian antivenoms were essentially pure IgG, commercial equine (Wyeth) and W.H.O. international reference antivenoms (Trimeresurus flavoviridis) contained several non-immunoglobulin contaminants. In standard mouse protection assays, the purified avian Crotalus atrox and T. flavoviridis antivenoms were 6.3 and 2.0 times as potent, respectively, as these equine antivenoms in neutralizing venom lethality. The purity, efficacy, and ease of manufacture of avian antivenoms, and their inability to fix mammalian complement, make them an attractive alternative to equine and other mammalian antivenoms.

[Preparation and characterization of antibodies against Bungarus multicinctus venom by liposomes]

Bungarus multicinctus venom was incorporated into sphingomyelin-cholesterol liposomes which were stabilized with osmium tetroxide. The lethal toxicity of B. multicinctus venom in osmicated liposomes greatly decreased to 1.03% that of crude venom. Rabbits were divided into four groups for immunization. Group A was immunized with crude venom, group B and group C with osmicated liposomes, and group D with osmicated liposomes followed by the crude venom. Immunization was performed in the presence of Freund's adjuvant except for group B. The antibody levels during the course of immunization were measured by ELISA and the contents of precipitating antibody were determined by quantitative precipitin reactions, while that of non-precipitating antibody was determined by affinity chromatography. Although the immune response was not increased by incorporating lipopolysaccharide immunostimulant, the specific neutralizing capacity of purified antibody from the pooled antisera of group D was more potent than that of the others. The almost non-toxic osmicated liposomes of B. multicinctus venom may be useful immunogens for the production of antiserum for treatment of snake bites.

Purification and properties of an antivenom factor from the plasma of the South American rattlesnake (Crotalus durissus terrificus)

The lethal toxicity of Crotalus durissus terrificus (Crotalinae, Viperidae) can be attributed mainly to the presence of a neurotoxic protein, crotoxin, which also shows phospholipase A2 activity. It has been previously demonstrated that both lethal and phospholipase A2 activities of crotoxin can be neutralized by an alpha 1-globulin factor that is present in the homologous blood. Crotalus durissus terrificus plasma also renders some degree of protection to mice against the lethal toxicity of heterologous venoms from snakes of the genus Bothrops (Crotalinae, Viperidae), but not of the genus Micrurus (Elapinae, Elapidae). An anti-toxic factor was purified to homogeneity from C.d. terrificus plasma after three chromatographic steps (DEAE-Sephacel anion exchange, CM-Sepharose cation exchange and Pro-RPC reverse phase chromatography); it is named CNF for Crotalus neutralizing factor. The purification process was accompanied by polyacrylamide gel electrophoresis in the presence of SDS and by measurements of phospholipase A2 inhibition. After the first two purification steps, an 86-fold increase of the inhibitory activity of CNF was observed; however, the third step caused an apparent inactivation of the factor. The inactive CNF was shown to correspond to the previously active plasma material and to be homogeneous on electrophoresis, immunoelectrophoresis and partial amino-terminal sequence. The mol. wt of CNF was estimated as 23,600 by SDS-PAGE.

Venom constituents of Notechis scutatus scutatus (Australian tiger snake) from differing geographic regions

Column chromatography and polyacrylamide gel electrophoresis of Notechis scutatus scutatus venom showed that the venoms from different geographical locations had variations in their constituents. The venom collected from South Australia region contained both notexin and notechis II-5. The relative quantity of notechis II-5 was about three times that of notexin. On the other hand, the venom from Victoria region contained large amounts of notexin, but lacked notechis II-5. Instead, an unknown nontoxic protein, designated as notechis II-5b, exhibiting weak phospholipase A2 activity appeared in the position of notechis II-5 elution. This protein had an N-terminal sequence of N-L-I-Q-L-S-N-M-I-K-C-A-I-P-G-S-Q-P-L-F, sharing 45% homology with notexin and notechis II-5 and 60% homology with notechis II-1. The antibodies raised against Trp-modified notexin inhibited the enzymatic activities of notexin and notechis II-5 by 88 and 68%, respectively. However, the affinity of notexin for the antibodies was nine-fold greater than that of notechis II-5. This result is contrary to the previous finding (Mollier et al., FEBS Lett. 250, 479-482, 1989) in which notexin and notechis II-5 had similar binding affinities for antibodies raised against native notexin. This observation suggests that the antibodies prepared in this study could differentiate between isoforms of notexin.

Quantitation by enzyme-immunoassay of antibodies against Bothrops myotoxins in four commercially-available antivenoms

An enzyme-immunoassay (EIA) for the quantitation of antibodies against myotoxins present in the venoms of Bothrops asper (Costa Rica), B. atrox (Colombia) and B. moojeni (Brazil), was developed. This EIA was utilized for the evaluation of four antivenoms produced in Mexico (Laboratorios Myn; MYN), Costa Rica (Instituto Clodomiro Picado; ICP), Colombia (Instituto Nacional de Salud; INS) and Brazil (Instituto Butantan; IB). Antivenoms ICP, IB and INS showed a higher titer of antibodies against the three myotoxins tested, with only slight differences between them, depending on the antigen utilized. In contrast, MYN antivenom had very low levels of antibodies to the three myotoxins. Seventeen batches of ICP antivenom were analyzed by EIA, using B. asper myotoxin II as antigen. Although all batches had high anti-myotoxin titers, these varied significantly. Batches produced after 1988 had, in general, higher titers than older (1986-1987) ones. Antivenom stored for one year at 37 degrees C had a slight, but significant (P less than 0.002) decrease of anti-myotoxin activity, compared to antivenom stored at 4 degrees C or 23 degrees C. No correlation was found between anti-myotoxin concentration and lethality-neutralizing ability of the ICP antivenom.

Equine antibodies to Bothrops asper myotoxin II: isolation from polyvalent antivenom and neutralizing ability

Equine antibodies to B. asper myotoxin II were isolated from polyvalent antivenom by affinity chromatography. Purified antibodies were among the most acidic serum immunoglobulins, migrating between the beta- and alpha 2-globulin regions by zone electrophoresis. This might be related to the fact that myotoxin II is a very basic antigen. At an antibody/toxin molar ratio of two or higher, myotoxic effect of myotoxin II was neutralized completely. Antibodies also neutralized myotoxic activity of crude venom in mice, reducing the effect by about 75% when a proportion of 16 mg antibodies/mg venom was tested. Despite the lack of phospholipase A2 activity of myotoxin II, antibodies were able to neutralize this enzymatic activity of myotoxin I, a previously described isoform. This finding is in agreement with the notion that myotoxin II is a phospholipase A2-analog devoid of this enzyme activity.

Effect of storage temperature on the stability of the liquid polyvalent antivenom produced in Costa Rica

The effect of storage temperature on the stability of the liquid polyvalent (crotaline) antivenom produced at the Instituto Clodomiro Picado, Costa Rica, was studied during a twelve-month period. The following parameters were evaluated: neutralizing potency against lethal activity of Bothrops asper venom; protein and phenol concentrations; pH; turbidity; safety; and sterility. Analyses were performed each month on different samples of a batch, stored at 4, 23, 30 and 37 degrees C. No significant (P greater than 0.1) variations occurred in potency, protein and phenol concentrations, pH, sterility or safety, at any of the storage temperatures during the study period. However, visual inspection revealed a moderate increase in turbidity of the samples stored at 23, 30 and 37 degrees C, at nine, four and three months, respectively. Culture of samples excluded the possibility of microbial contamination of the product leading to turbidity. Chromatographic and electrophoretic analyses demonstrated that turbidity was caused by the formation of heterogeneous protein aggregates of high molecular weight. Present results support the conclusion that, although storage temperature (up to 37 degrees C for twelve months) does not alter antivenom potency, it significantly influences the formation of protein aggregates. This phenomenon can be prevented by recommending the storage of antivenom at refrigeration temperature.

Comparison of the immunogenicity and antigenic composition of several venoms of snakes in the family Crotalidae

Crude venoms from the prairie rattlesnake (Crotalus viridis viridis), the western diamondback rattlesnake (Crotalus atrox), the eastern diamondback rattlesnake (Crotalus adamanteus) and the timber rattlesnake (Crotalus horridus horridus) were used to prepare monovalent antivenoms in rabbits. Each of these four monovalent antivenoms was reacted against six different venoms using the technique of immunoblotting (Western blot) to determine the relative immunogenicity of the four venoms and to compare the antigenic composition of six venoms. In addition to the four venoms listed above, venoms from the South American rattlesnake (Crotalus durissus terrificus) and the fer-de-lance (Bothrops atrox) were tested. SDS-PAGE showed that C. v. viridis venom contains the greatest number of components with 20, and the greatest number (7) less than 15,000 in mol. wt. C. durissus terrificus venom contains the least number of components, having 11. Immunoblotting experiments showed that the greatest reaction between venom and antivenom is not always obtained with the homologous system although the two greatest reactions obtained in this study were for two homologous reactions: that between monovalent anti-C. v. viridis venom and C. v. viridis venom, and that between monovalent anti-C. atrox venom and C. atrox venom. For antivenoms made to C. h. horridus and C. adamanteus venoms, the greatest reaction was obtained with C. atrox venom. There appeared to be no difference in immunogenicity between high-medium mol. wt (greater than 15,000) components and low mol. wt (less than 15,000) components in all systems tested except for C. atrox venom where two low mol. wt components gave a stronger reaction with the antivenom than would have been predicted based on their relative content in the venom as indicated by SDS-PAGE. If the immunoblots are scanned with a densitometer, both the qualitative (number of bands) and the quantitative (density of bands) reactions between venom and antivenoms can be taken into consideration by using a Reactivity Index (number of bands x density of bands). By comparing Reactivity Indexes of the various reactions obtained, the most cross-reactive antivenom tested was the monovalent antivenom to C. v. viridis venom, followed by anti-C. adamanteus, anti-C. atrox and anti-C. h. horridus in order of decreasing reactivity. The Reactivity Index can also be used to estimate the reactivity of a single antivenom with different venoms. The major limitation of this approach is the difficulty in standardizing the detection procedure using silver enhanced Protein A gold.

Detection of IgG4 antibodies by immunoblotting in patients on vespid venom immunotherapy

A nitrocellulose immunoblotting procedure has been used to monitor patient specific IgG antibodies during Hymenoptera vespid venom therapy. By using monoclonal antibodies in the immunoblot assay the relative IgG4 antibody levels could be analysed semiquantitatively. Treatment with vespid venom over 2 years resulted in rises in venom-specific IgG4 antibodies mostly directed towards antigen 5, phospholipase A and hyaluronidase. The use of high quality monoclonal antibodies in immunoblotting assays offers an improvement in the in vitro evaluation of venom immunotherapy.

Rapid decline in blood antimyotoxin levels in the presence of myotoxin A from prairie rattlesnake (Crotalus viridis viridis) venom

The disappearance of antibodies to myotoxin a from the bloodstream in mice was measured with a specific ELISA over a ninety-six hour period in the presence and absence of myotoxin a. A gradual disappearance of antibodies to myotoxin in the absence of toxin was observed during the 96 hr sampling period, although antibodies were still detectable at 96 hrs. However, in the presence of myotoxin a very rapid decrease of antimyotoxin occurred. When antiserum injection was followed by myotoxin injection (5 min. later) the decline in antibodies was immediate and no antibodies could be detected 30 min. after the antiserum injection. When antiserum was injected either immediately or 30 min. after toxin, antibody levels declined sharply and were non-detectable 1 hr. after antiserum injection. These results have clinical significance since they indicate that antimyotoxin can still bind the toxin, even when administration of the antiserum is delayed for 30 min. after injection of the toxin. Multiple injections of antiserum may be required to maintain a neutralizing level of antiserum.

[Production of monoclonal antibodies. Scorpion antitoxins: characterization and molecular mechanisms of neutralization]

Two monoclonal antibodies specific for the potent toxin II of the scorpion Androctonus australis Hector have been produced. One of them shows both high affinity binding to the toxin (Kd = 0.8 nM) and in vivo and in vitro neutralizing properties. The mechanism by which the antibody neutralizes toxin binding to its receptor was shown to be of the competitive type, the epitope is overlapping or being close to the receptor binding region of the toxin. Several residues of the toxin clustered in the C-terminal region were shown likely to be part of the discontinuous epitope recognized by the antibody. The positive charge of the NH2-Lys58 seems to play a pivotal role in the binding of the toxin to both the monoclonal antibody and the sodium channel receptor.

ELISA confirmation of acute and past envenoming by the monocellate Thai cobra (Naja kaouthia)

The monocellate Thai cobra (Naja kaouthia) is a major cause of snake bite mortality and morbidity throughout Thailand, but neither the local nor the systemic effects of its venom are diagnostic. Species diagnosis is important because only monospecific antivenoms are available for treatment in Thailand. We tested the ability of the ELISA technique to detect venom antigen in the sera of 58 acute snake bite cases including 4 fatalities, and venom antibody in 51 patients bitten between 1 month and 19 years previously. N. kaouthia venom antigen was found in 8 of 33 patients with only local envenoming and in 14 of 20 with local plus systemic (neurotoxic) envenoming, but the mean venom concentration was 33 times greater in the latter group. The serum of 1 fatal case contained banded krait (Bungarus fasciatus) but no cobra venom antigen. N. kaouthia venom antibody was present in sera of patients bitten between 1 month and 7 years previously. Antibody was found in 6 of 8 patients who had had local envenoming alone but in only 19 of 41 who had had systemic envenoming treated by antivenom. The titer of antibody declined with an approximate half time of 2-3 years. One patient had a significant titer of B. fasciatus venom antibody. This study confirms the value of ELISA-immunodiagnosis and the predominance of N. kaouthia as a cause of neurotoxic envenoming in the Bang Phli area. However, the attribution of 1 fatal case to B. fasciatus bite suggests that patients with neurotoxic signs should be given B. fasciatus antivenom if they fail to respond to cobra antivenom.

A critical reappraisal of the use of enzyme-linked immunosorbent assays in the study of snake bite

The enzyme-linked immunosorbent assay (ELISA) has been the most widely used serological test in snake bite immunodiagnosis and epidemiology. The technique has been applied, however, without due consideration of the many factors which would affect an inherently sensitive test system, especially in tropical rural areas where large scale snake bite studies are usually carried out. This review discusses the effects of non-specific reactivity, cross reactivity and the quality of reagents on both the sensitivity and specificity of venom antigen and antibody detection assays. Simple laboratory modifications to optimize the assays are described. The importance of using the predictive value to assess the validity of applying the same test system in different circumstances is stressed. To fulfil its potential as the most versatile immunoassay technique in snake bite research, the test conditions of the ELISA will have to be much more stringently controlled in future.

The distribution among ophidian venoms of a toxin isolated from the venom of the Mojave rattlesnake (Crotalus scutulatus scutulatus)

A toxin analogous to Mojave toxin or protein K' was isolated from venom of the Mojave rattlesnake (Crotalus s. scutulatus) by anion exchange and gel permeation chromatography. This toxin has an apparent native molecular weight of 20,000-22,000, a subunit molecular weight of 14,000 and a pI of 4.9-5.0. The i.p. LD50 is 0.094 mg/kg for mice. A wide variety of ophidian venoms (crotaline, viperine, elapid, hydrophid and colubrid) were examined for the presence of this toxin using Ouchterlony, immunoelectrophoresis, ELISA and Western transfer. High concentrations were found in 4 of 6 C. scutulatus venom samples, 2 of 3 C. durissus samples and samples from C. viridis concolor and C. tigris. A moderate concentration was found in 1 of 3 C. durissus samples and low to trace concentrations in 1 C. durissus sample, 1 C. scutulatus sample, 2 of 12 C. atrox samples and a Trimeresurus flavoviridis sample, the latter being the only instance of detection of the toxin in a snake other than a rattlesnake. The toxin appears in at least two phylogenetic lines of rattlesnakes, and its geographic distribution in North American rattlesnake species resembles a mosaic.

Tick (Ixodes holocyclus) paralysis in the dog--induction of immunity by injection of toxin

Three beagle dogs were immunised against the paralysing effects of holocyclotoxin, using toxic extracts derived from salivary glands of the Australian paralysis tick, Ixodes holocyclus. Upon subsequent challenge with four ED50's of toxin the animals were completely immune, whereas during the early stages 2 of 3 dogs became paralysed after injection with 0.5 ED50. Three immunised beagles, on which 15 I. holocyclus ticks had fed, showed no symptoms but a control beagle became paralysed after 4 I. holocyclus females fed on it. Treatment was instituted immediately upon the onset of clinical signs and the dog recovered uneventfully.

The chemical nature of the funnel-web spider venom inhibitor found in rat plasma

Strong evidence has been obtained that the funnel-web spider venom inhibitor, previously found to occur naturally in the blood of rats, is at least partly immunoglobulin in composition. However, the results of chromatographic and immunological studies, including the use of specific antisera, indicate that this inhibitor is not a single chemical entity and apparently resides within more than one immunoglobulin class. In addition, it was observed that challenge of rats with Atrax venom substantially increased the venom-inhibiting powers of their blood and that these powers were located in the same plasma fractions as in unchallenged rats.

Dynamic changes of horse serum T-globulin immunization with snake venoms, tetanus and diphtheria toxoids

In course of immunizing horses with snake venoms, tetanus and diphtheria toxoids, a new serum component, T-globulin, was formed and migrated between the beta- and gamma-globulins. The T-globulin content was parallel with the antibody titre after the middle course of immunization. There were many components in snake antivenin and T-globulin was composed of most of those components. The components of diphtheria T-globulin were the same as those of crude antitoxin and tetanus T-globulin except one precipitin.

[Biological and immunological researches on snake venom. V. Application of the immunochemical technics to the titration of specific antibodies to the alpha toxin of Naja nigricollis venom (author's transl)]

In order to establish a simple method to titrate antitoxin antibodies in the antivenom sera, we suggest a new immunochemical technic. To a constant dose of a pure toxin extracted from a snake venom, increasing volumes of specific immune serum are added so as an excess of toxin remains free. This residual toxin is titrated by electroimmunodiffusion technic according to Laurell or by radial immunodiffusion method of Mancini. The experimental results in vitro are compared to those obtained in vivo. If a given volume of immune serum neutralize X microgram of toxin by the in vivo technic it will combine in vitro to 2 X or 1.2 X of the same toxin, respectively if we refer to electroimmunodiffusion or to radial immunodiffusion technic results.

Serum reactions. An analysis of commercial antivenoms and the possible role of anticomplementary activity in de-novo reactions to antivenoms and antitoxins

Infusion of concentrated heterologous serum proteins may precipitate severe reactions in humans. Some of these reactions are not due to a preexisting hypersensitivity to the foreign protein, but rather to the strongly anticomplementary activity (ACA) of the infused protein. The latter mechanism could account for the occasional anaphylactoid reaction seen in a patient who has had no known previous exposure to the foreign protein. Similarly, it could account for the patient who fails to react to a preliminary subcutaneous trial dose, but then collapses when he is infused later with the same preparation. Nine commercial antivenoms from nine countries were examined and most were found to have high levels of anticomplementary activity. Considerable variation was found in both the immunochemical properties and the anticomplementary activity of these antivenoms. Antitoxins of equine origin to the toxins of diphtheria, tetanus and gas gangrene were also found to have high anticomplementary activity. Because of this activity these preparations should always be diluted and infused slowly. Lack of reaction to a test dose will never guarantee an uneventful infusion, and thus all infusions of heterologous immunoglobulin should be undertaken with the greatest caution and vigilance.