Preclinical assessment of the ability of polyvalent (Crotalinae) and anticoral (Elapidae) antivenoms produced in Costa Rica to neutralize the venoms of North American snakes.

Polyvalent (Crotalinae) and anticoral (Elapidae) antivenoms produced by Instituto Clodomiro Picado, Costa Rica, were assessed for their ability to neutralize various toxic activities of the venoms of North American snakes of the genera Crotalus, Agkistrodon and Micrurus, in assays involving preincubation of venom and antivenom. When the intraperitoneal route of injection was utilized, polyvalent (Crotalinae) antivenom was effective in the neutralization of the venoms of Crotalus atrox, Crotalus adamanteus, Crotalus viridis viridis, Crotalus horridus atricaudatus, Agkistrodon contortrix contortrix and Agkistrodon piscivorus piscivorus, whereas the venom of Crotalus scutulatus was not neutralized. When the intravenous route was used, results differed depending on the "challenge dose" of venom employed. Polyvalent antivenom neutralized all venoms when mice were challenged with 2 LD(50)s of venom. When 5 LD(50)s were used, antivenom neutralized the venoms of C. atrox, C. adamanteus, C. v. viridis and C. h. atricaudatus, being ineffective in the neutralization of C. scutulatus, A. c. contortrix and A. p. piscivorus. Polyvalent antivenom was effective in the neutralization of hemorrhagic and myotoxic activities of all venoms studied. It also neutralized coagulant activity of C. adamanteus venom, whereas most of the venoms were devoid of clotting activity on plasma in vitro. Moreover, it neutralized defibrinating activity of the only three venoms that induced this effect (i.e. C. adamanteus, A. c. contortrix and A. p. piscivorus). Anticoral (Elapidae) antivenom neutralized lethality induced by the venom of Micrurus fulvius, using either the intravenous or the intraperitoneal routes of injection. Moreover, it neutralized myotoxic effect of this venom as well. It is concluded that polyvalent antivenom neutralizes lethality and other activities of most of the crotaline venoms tested. However, since it is ineffective in neutralizing the lethal effect of C. scutulatus venom, it is suggested that a venom containing presynaptically-active neurotoxic phospholipases A(2) related to "mojave toxin" needs to be introduced in the immunizing mixture in order to increase the neutralizing scope of this product in North America. Anticoral antivenom is highly effective in the neutralization of the venom of M. fulvius.     

Evaluation of four different immunogens for the production of snake antivenoms.

Four different immunogens were used to produce polyvalent antivenom in rabbits to the venoms of Bothrops atrox, Crotalus atrox, Crotalus adamanteus and Crotalus durissus terrificus. The immunogens were: (1) unfractionated mixture of the four crude venoms, and three fractions of the mixture as follows, (2) HPLC gel filtration high (> 50,000) mol. wt fraction, (3) HPLC gel filtration medium (14,000-50,000) mol. wt fraction, and (4) HPLC gel filtration low (< 14,000) mol. wt fraction. The resultant immune sera were compared with commercial antivenom (Wyeth, polyvalent Crotalidae) for total IgG content, ELISA reactivities, patterns of Western blots and ability to neutralize lethal and local hemorrhagic activities of the four venoms. The results indicate that the rabbit antivenoms had significantly higher ELISA reactivity and blotting signals than Wyeth antivenom. However, neither ELISA nor Western blotting signals correlated with the ability of the antivenoms to neutralize the lethal or hemorrhagic activities of the venoms. The protective ability of the antivenoms varied considerably. In general, antivenoms generated by using fractionated venoms as immunogens exhibited greater protective ability than antivenom produced by using the mixture of four venoms as immunogen. Some of the antivenoms provided greater or comparable protective ability for certain venoms when compared to Wyeth antivenom. It appears that the use of certain venom fractions as immunogens is a promising alternative for production of effective antivenoms.     

Enzyme-linked immunosorbant assay (ELISA) of size-selected crotalid venom antigens by Wyeth's polyvalent antivenom

The binding of Antivenom (Crotalidae) Polyvalent to fractions from crude venoms of eight crotalid and one viperid snake, obtained by high performance size-exclusion chromatography, was determined with an indirect enzyme-linked immunosorbent assay (ELISA). Most of the large (greater than 30,000 mol. wt) molecular mass crotalid venom fractions were associated with high (greater than 0.7 absorbance units) ELISA values. Similarly, the medium (13,000-30,000 mol. wt) and small (less than 14,000 mol. wt) molecular mass crotalid venom fractions were coincident with moderate (0.3-0.7 absorbance units) and low (less than 0.3 absorbance units) ELISA levels. Some variability in this pattern was seen with individual venom fractions. A distinctly different pattern of ELISA values were observed with two rattlesnake venoms: the South American (Crotalus durissus terrificus) and Mojave desert (Crotalus scutulatus scutulatus) rattlesnakes. The elution profile from these venoms showed a progression of low to moderate ELISA values within the large molecular mass fractions. This pattern was followed by a decline to low ELISA values throughout the remainder of the elution profile. When saw scaled viper (Echis carinatus leucogaster) venom fractions were tested, only background ELISA values were detected with antivenom. Similarly, background ELISA values were associated with the small molecular mass fractions of all venoms tested. In addition, the elution position for the basic peptides of southern Pacific (Crotalus viridis helleri) and timber (Crotalus h. horridus) rattlesnake venoms showed minimal ELISA values. These data support the view that except for the venom of C. durissus terrificus and C. s. scutulatus, most antivenom antibodies bind large (greater than 30,000 mol. wt) venom fractions. Thus, antivenom contains minimal levels of antibodies to the basic peptides in these venoms.     

Cross reactivity of three antivenoms against North American snake venoms.

The antivenom in the United States today is in short supply, expensive and may not even be the most effective in neutralizing venoms from snakes in certain geographical locations. The ED(50) is considered to be the best indicator of antivenom efficacy, however, other tests are needed. In this study, three antivenoms (Antivipmyn (Fab(2)H), Crotalidae Polyvalent Immune Fab (Ovine) (FabO) and UCV (FabV) were used to test the effectiveness of neutralization of eight venoms (Agkistrodon piscivorus piscivorus, Bothrops asper, Crotalus adamanteus, C. durissus durissus, C. horridus atricaudatus, C. h. horridus, C. atrox, and C. molossus molossus). Four different assays were used to study the efficacy of the antivenoms: the antihemorrhagic, antigelatinase, antifibrinolytic and antihide powder azure. Fab(2)H antivenom was more effective in neutralizing the enzymatic activities of these eight venoms than FabO and FabV antivenoms.     

Comparison of the effect of Crotalus simus and Crotalus durissus ruruima venoms on the equine antibody response towards Bothrops asper venom: Implications for the production of polyspecific snake antivenoms

Antivenoms are preparations of immunoglobulins purified from the plasma of animals immunized with snake venoms. Depending on the number of venoms used during the immunization, antivenoms can be monospecific (if venom from a single species is used) or polyspecific (if venoms from several species are used). In turn, polyspecific antivenoms can be prepared by purifying antibodies from the plasma of animals immunized with a mixture of venoms, or by mixing antibodies purified from the plasma of animals immunized separately with single venom. The suitability of these strategies to produce polyspecific antibothropic-crotalic antivenoms was assessed using as models the venoms of Bothrops asper, Crotalus simus and Crotalus durissus ruruima. It was demonstrated that, when used as co-immunogen, C. simus and C. durissus ruruima venoms exert a deleterious effect on the antibody response towards different components of B. asper venom and in the neutralization of hemorrhagic and coagulant effect of this venom when compared with a monospecific B. asper antivenom. Polyspecific antivenoms produced by purifying immunoglobulins from the plasma of animals immunized with venom mixtures showed higher antibody titers and neutralizing capacity than those produced by mixing antibodies purified from the plasma of animals immunized separately with single venom. Thus, despite the deleterious effect of Crotalus sp venoms on the immune response against B. asper venom, the use of venom mixtures is more effective than the immunization with separate venoms for the preparation of polyspecific bothropic-crotalic antivenoms.     

Horse IgG isotypes and cross-neutralization of two snake antivenoms produced in Brazil and Costa Rica.

Horse IgG isotypes and cross-neutralization of two snake antivenoms produced in Brazil and Costa Rica. Toxicon 000-000. This work compared the specificity, ELISA titers and IgG subclass content of the polyvalent antivenom (anti-Bothrops asper, Crotalus durissus durissus and Lachesis muta stenophrys) of Instituto Clodomiro Picado (Costa Rica) and the bothropic antivenom (anti-Bothrops jararaca, B. jararacussu, B. moojeni, B. neuwiedi and B. alternatus) of Instituto Butantan (Brazil). The role of IgG(T) and IgGa subclasses in neutralization of some venom toxic activities and the cross neutralization of the antivenoms against B. jararaca and B. asper venoms were also evaluated. Both antivenoms were able to recognize B. asper and B. jararaca venoms by immunoblotting and presented similar antibody titers when assayed by ELISA. IgG(T) was highest, followed by IgGa, IgGb and IgGc. IgGa and IgG(T) isotypes isolated from both antivenoms by affinity chromatography were tested for neutralization of lethal, hemorrhagic, coagulant and phospholipase A2 activities of the homologous venoms. In both antivenoms, IgG(T) was the major isotype responsible for neutralization of all the tested activities, followed by IgGa. These results suggest that Instituto Butantan and Instituto Clodomiro Picado antivenoms have the same IgG profile and their neutralizing ability is due mostly to the IgG(T) isotype. Also, they neutralize lethality in mice induced by homologous and heterologous venoms, the bothropic antivenom of Instituto Butantan being more effective.     

Analysis of camelid antibodies for antivenom development: Neutralisation of venom-induced pathology

Camelid IgG has been reported to be less immunogenic, less able to activate the complement cascade and more thermostable than IgG from other mammals, and has the ability to bind antigens that are unreactive with other mammalian IgGs. We are investigating whether these attributes of camelid IgG translate into antivenom with immunological and venom-neutralising efficacy advantages over conventional equine and ovine antivenoms. The objective of this study was to determine the preclinical venom-neutralising effectiveness of IgG from camels immunised with venoms, individually or in combination, of the saw-scaled viper, Echis ocellatus, the puff adder, Bitis arietans and the spitting cobra, Naja nigricollis - the most medically-important snake species in West Africa. Neutralisation of the pathological effects of venoms from E. ocellatus, B. arietans and N. nigricollis by IgG from the venom-immunised camels, or commercial antivenom, was compared using assays of venom lethality (ED₅₀), haemorrhage (MHD) and coagulopathy (MCD). The E. ocellatus venom ED₅₀, MHD and MCD results of the E. ocellatus monospecific camel IgG antivenom were broadly equivalent to comparable ovine (EchiTAbG^®, MicroPharm Ltd, Wales) and equine (SAIMR Echis, South African Vaccine Producer, South Africa) antivenoms, although the equine antivenom required half the amount of IgG. The B. arietans monospecific camel IgG neutralised the lethal effects of B. arietans venom at one fourth the concentration of the SAIMR polyspecific antivenom (a monospecific B. arietans antivenom is not available). The N. nigricollis camel IgG antivenom was ineffective (at the maximum permitted dose, 100 μl) against the lethal effects of N. nigricollis venom. All the equine polyspecific antivenoms required more than 100 μl to be effective against this venom. The polyspecific camel IgG antivenom, prepared from five camels, was effective against the venom-induced effects of E. ocellatus but not against that of B. arietans and N. nigricollis venoms. No direct correlation was evident between either camel IgG relative avidity or titre and the effectiveness of venom neutralisation in preclinical assays.     

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.     

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.     

Neutralization of kinin-releasing enzymes from viperid venoms by antivenom IgG fragments

The activities of kinin-releasing enzymes in the venoms of Vipera xanthina xanthina, V. lebetina obtusa, V. aspis aspis, V. lebetina schweizeri, V. ammodytes ammodytes and V. berus berus were determined using a specific radioimmunoassay for kinin. The kinin-releasing activities of all the viperid venoms measured in vitro were neutralized, to varying extents, by two commercially available monospecific antivenoms in the form of F(ab′)₂ (Zagreb) and Fab (TAb) immunoglobin fragments, indicating a high degree of cross-neutralization of those enzymes.     

Snake venom hemorrhagins: neutralization by commercial antivenoms

One monovalent (habu-antivenom) and five polyvalent antivenoms (Crotalidae; Orient, North, Central and South Africa) were tested for their ability to neutralize the hemorrhagic activity of 12 snake venoms (Agkistrodon, Bothrops, Crotalus, Sistrurus, Trimeresurus, Bitis, Echis spp.) when mixed prior to injection into the hind leg of mice. Considerable cross-neutralization was observed: antivenoms prepared against African snake venoms were equally or more potent in neutralizing the hemorrhagic activity of Crotalidae venoms. The same applies to Crotalidae antivenom which neutralized the activity of African snake venoms. Anti-hemorrhagic antibodies were isolated from a polyvalent antivenom by affinity chromatography using purified hemorrhagins from Bitis arietans and Crotalus adamanteus venom as ligands. These antibodies neutralized the activity of both hemorrhagins indicating common antigenic determinants in these molecules.     

A new Pan African polyspecific antivenom developed in response to the antivenom crisis in Africa.

Currently there is a crisis in the supply of antivenom for treatment of snake bite in sub-Saharan Africa. Commercial pressures have resulted in the reduction or even cessation of production of antivenom by European manufacturers while continued production of antivenom in Africa has been threatened by the privatisation of the only remaining company based in Africa. As a consequence, there has been an increase in snake bite morbidity and mortality in many African countries. Two Latin American antivenom manufacturers have agreed to produce antivenom suitable for Africa, using venoms from the species which are of the greatest medical importance in sub-Saharan Africa. Preclinical in vivo assays of neutralising potency demonstrated that a new Pan African antivenom produced in Colombia compared favourably with the existing commercial monospecific and polyspecific antivenoms. This new antivenom, and a similar product being manufactured in Costa Rica, are now candidates for clinical testing at an appropriate site in Africa.     

Neutralization of Bothrops mattogrossensis snake venom from Bolivia: Experimental evaluation of llama and donkey antivenoms produced by caprylic acid precipitation

Polyspecific bothropic/crotalic and bothropic/lachesic antivenoms were produced in Bolivia by immunizing two donkeys with the venoms of Bothrops mattogrossensis and Crotalus durissus terrificus and one llama with the venoms of B. mattogrossensis and Lachesis muta. These antivenoms are currently being used for snakebite envenomation in Bolivia. The rationale for using these animals is that donkeys and llamas are better adapted than horses to the high altitudes in South America and constitute good alternatives for antivenom production in these regions. Plasma was fractionated by caprylic acid precipitation of non-immunoglobulin plasma proteins, to obtain whole IgG preparations. Donkey-derived antivenom showed one band of 150 kDa when analyzed by SDS–PAGE, whereas llama antivenom presented two immunoglobulin bands, of 170 kDa and 120 kDa, the latter corresponding to the heavy-chain antibodies present in camelid sera. The effectiveness of these antivenoms to neutralize lethal, hemorrhagic, myotoxic, edema-forming, and defibrinogenating activities of the venom of B. mattogrossensis from Bolivia, a species formerly known as Bothrops neuwiedii, was assessed at the experimental level. Although llama antivenom has a total protein concentration four times lower than donkey antivenom, both preparations have similar neutralizing capacity against all toxic activities assessed. Llama and donkey IgG-based antivenoms are effective in the neutralization of B. mattogrossensis venom and represent valuable alternatives for antivenom manufacture in highland regions of South America.     

An indirect haemolytic assay for assessing antivenoms

Dilutions of antivenom, venom, human erythrocytes and a phosphatidylcholine suspension, were incubated for 30 min at 37 degrees C. After centrifugation, the liberated haemoglobin was measured spectrophotometrically. The assay was used to assess an ovine antivenom against the venom from the South American rattlesnake, Crotalus durissus terrificus, and an equine Wyeth antivenin (Crotalidae, polyvalent). The ovine antivenom was more than five times as effective as the equine product. It also neutralized venoms from the Western diamondback rattlesnake, Crotalus atrox, and the fer-de-lance, Bothrops atrox. However, antivenoms raised against venoms from other Crotalus and Bothrops species provided little protection against the haemolytic activity of C. d. terrificus venom.     

Comparison of the potency of three Brazilian Bothrops antivenoms using in vivo rodent and in vitro assays. BIASG (Butantan Institute Antivenom Study Group).

Three Brazilian polyspecific Bothrops antivenoms were compared using standard W.H.O. rodent in vivo and in vitro assays of their ability to neutralize the principal venom activities of pooled whole Bothrops jararaca venom. On a volume basis, the antivenoms were equally effective in neutralizing lethal activity in mice, and there were only minor differences in their ability to neutralize venom-induced haemorrhage, necrosis and procoagulant activity. Antivenom efficacy in neutralizing defibrinogenation varied. However, when equal amounts of antivenom IgG were compared, it was found that the FUNED antivenom best neutralized lethality, haemorrhage, necrosis and fibrinogen clotting activity. Vital Brazil and FUNED antivenoms were equally effective in neutralizing plasma coagulant activity but Vital Brazil antivenom was the more effective in neutralizing defibrinogenation.     

Enzymatic and immunochemical characterization of Bothrops insularis venom and its neutralization by polyspecific Bothrops antivenom.

Herein we compared the biological activities of Bothrops insularis and Bothrops jararaca venoms as well as their neutralization by polyspecific Bothrops antivenom (PBA). On account of that, we investigated their antigenic cross-reactivity and the neutralization of lethal, myotoxic and defibrinating activities by polyspecific and species-specific antivenoms. Silver-stained SDS-PAGE gels evidenced many common bands particularly above 47 kDa between B. jararaca and B. insularis venoms. However, some protein bands between 46 and 28 kDa were observed exclusively in B. jararaca venom. Both venoms presented gelatinolytic, caseinolytic, fibrinogenolytic and phospholipase A(2) activities. No hyaluronidase activity was detected in both venoms by zymography. Polyspecific and species-specific antivenoms showed similar titers to B. jararaca and B. insularis venoms by ELISA, and recognized similar components by immunoblotting. The PBA was effective in neutralizing the lethal, myotoxic and defibrinating activities of both venoms as well as to abrogate microcirculatory disturbances induced by B. insularis venom. No statistically significant difference was observed for minimal hemorrhagic doses between both venoms. Antigenic cross-reactivity was evident between both venoms. Since toxic and enzymatic activities were similar, we speculate that B. insularis venoms can induce a local damage in humans comparable to that observed in other Bothrops venoms. Besides, the PBA was effective in neutralizing the toxic activities of B. insularis venom.     

Preparation of a crotoxin neutralizing monoclonal antibody

Crotoxin is a heterodimeric protein composed of an acidic and basic subunit from the venom of Crotalus durissus terrificus and is representative of a number of presynaptically acting neurotoxins found in the venom of rattlesnakes. Four different monoclonal antibodies, typed as IgG1 subclass, were raised against the basic subunit of this toxin. One was a potent neutralizing antibody of intact crotoxin, which could neutralize approximately 1.6 moles of purified crotoxin per mole of antibody. The monoclonal antibody enhanced the neutralizing ability of commercial polyvalent crotalid antivenom against the lethality of crude C. d. terrificus venom four-fold. Paradoxically, this monoclonal antibody by itself was ineffective against the lethality of crude C. d. terrificus venom. Using an enzyme-linked immunosorbent assay, we tested various proteins for competitive inhibition of binding of biotinylated-crotoxin to plates coated with the four individual monoclonal antibodies. Concolor toxin, vegrandis toxin, intact crotoxin, Mojave toxin, and the basic subunit of crotoxin showed increasing effectiveness as displacers of crotoxin from the neutralizing monoclonal antibody. None of the monoclonal antibodies reacted with purified phospholipase A2 enzymes from Crotalus atrox or Crotalus adamanteus, nor any of the components present in the crude venoms from four different elapids known to contain presynaptically acting neurotoxins, which show some sequence identity to crotoxin.     

Antigenic relationship between the venom of the night adder Causus maculatus and venoms of other viperids.

Monovalent antivenoms were raised in mice against the venoms of Causus maculatus, Vipera ammodytes, Echis carinatus, Cerastes cerastes, Bitis arietans, Agkistrodon rhodostoma and Bothrops atrox. These antivenoms as well as four commercially available antivenoms were tested against the venoms of 15 viperid species by means of immunoelectrophoresis and/or ELISA. Cross-reactive protein bands were determined by immunoblot. ELISA cross-reactions of C. maculatus antivenom were low with all heterologous venoms. When investigating the other viperine antivenoms in ELISA stronger cross-reactions were observed with several heterologous venoms. In immunoblot, two heterologous antivenoms cross-reacted with one or two protein bands of C. maculatus venom whereas there were at least four heterologous antivenoms cross-reacting with each of the other venoms. The findings indicate that there is little antigenic affinity between C. maculatus venom and the other venoms investigated. Broad in vitro cross-reactions between viperine antivenoms and Causus venom which were reported in literature seem to be attributable to the use of antivenoms of commercial grade. Specificity of commercially produced, mono- or polyvalent antivenoms may not be strictly limited to those venoms, against which potency is claimed on the label of the product.     

Cross-neutralization of thrombin-like enzymes in snake venoms by polyvalent antivenoms

and . Cross-neutralization of thrombin-like enzymes in snake venoms by polyvalent antivenoms. Toxicon 27, 1397–1399, 1989.—Five polyvalent antivenoms (Crotalidae; Orient, North, Central and South Africa) were tested for their ability to neutralize the thrombin-like activity of snake venoms (Bitis gabonica, Agkistrodon acutus, Bothrops asper, B. atrox, Crotalus adamanteus). Considerable cross-neutralization was observed. Anti-coagulase antibodies were isolated from an antivenom by affinity chromatography using a purified enzyme from Bitis gabonica venom. These antibodies neutralized the activity of most snake venom coagulant enzymes.     

Differences between the venoms of two sub-species of Russell's viper: Vipera russelli pulchella and Vipera russelli siamensis

Ion exchange chromatography was carried out using venoms obtained from two sub-species of Russell's viper; V. russelli siamensis from Burma and V. russelli pulchella from Sri Lanka. Differences were observed in the elution position of venom components having haemolytic and procoagulant activity but not those causing fibrinolysis. Only the V. russelli siamensis venom exhibited any platelet aggregating activity. The Indian (Haffkine) polyspecific and the Burmese (Burma Pharmaceutical Industries) monospecific antivenoms, when used in cross immunoelectrophoresis against the two venoms, revealed differences in the number and/or intensity of the precipitin bands present. An important functional consequence of this was that the Burmese antivenom did not neutralize the haemolytic activity of the V. russelli pulchella venom in vitro and would thus probably not be effective in treating this consequence of envenoming by Russell's viper in Sri Lanka. Differences in the composition and the clinical effects of the two venoms emphasizes the importance of using venom from the local snake for antivenom production if optimal clinical efficacy is to be achieved.