Development of Equine IgG Antivenoms against Major Snake Groups in Mozambique

BACKGROUND

Snake envenoming is a significant public health problem in underdeveloped and developing countries. In sub-Saharan Africa, it is estimated that 90,000-400,000 envenomations occur each year, resulting in 3,500-32,000 deaths. Envenomings are caused by snakes from the Viperidae (Bitis spp. and Echis spp.) and Elapidae (Naja spp. and Dendroaspis spp.) families. The African continent has been suffering from a severe antivenom crisis and current antivenom production is only sufficient to treat 25% of snakebite cases. Our aim is to develop high-quality antivenoms against the main snake species found in Mozambique.

METHODS

Adult horses primed with the indicated venoms were divided into 5 groups (B. arietans; B. nasicornis + B. rhinoceros; N. melanoleuca; N. mossambica; N. annulifera + D. polylepis + D. angusticeps) and reimmunized two times for antivenom production. Blood was collected, and plasma was separated and subjected to antibody purification using caprylic acid. Plasmas and antivenoms were subject to titration, affinity determination, cross-recognition assays and in vivo venom lethality neutralization. A commercial anti-Crotalic antivenom was used for comparison.

RESULTS

The purified antivenoms exhibited high titers against B. arietans, B. nasicornis and B. rhinoceros (5.18 x 106, 3.60 x 106 and 3.50 x 106 U-E/mL, respectively) and N. melanoleuca, N. mossambica and N. annulifera (7.41 x 106, 3.07 x 106 and 2.60 x 106 U-E/mL, respectively), but lower titers against the D. angusticeps and D. polylepis (1.87 x 106 and 1.67 x 106 U-E/mL). All the groups, except anti-N. melanoleuca, showed significant differences from the anti-Crotalic antivenom (7.55 x 106 U-E/mL). The affinity index of all the groups was high, ranging from 31% to 45%. Cross-recognition assays showed the recognition of proteins with similar molecular weight in the venoms and may indicate the possibility of paraspecific neutralization. The three monospecific antivenoms were able to provide in vivo protection.

CONCLUSION

Our results indicate that the anti-Bitis and anti-Naja antivenoms developed would be useful for treating snakebite envenomations in Mozambique, although their effectiveness should to be increased. We propose instead the development of monospecific antivenoms, which would serve as the basis for two polyvalent antivenoms, the anti-Bitis and anti-Elapidae. Polyvalent antivenoms represent an increase in treatment quality, as they have a wider range of application and are easier to distribute and administer to snake envenoming victims.

Evaluation of the effects of various chemicals on discharge of and pain caused by jellyfish nematocysts

Jellyfish tentacles in contact with human skin can produce pain swelling and redness. The pain is due to discharge of jellyfish nematocysts and associated toxins and discharge can be caused by a variety of mechanical and chemical stimuli. A series of tests were carried out with chemicals traditionally used to treat jellyfish stings e.g. acetic acid ammonia meat tenderizer baking soda and urea to determine if these chemicals stimulated or inhibited nematocyst discharge and if they brought relief to testers who were exposed to jellyfish tentacles. Chrysaora quinquecirrha (sea nettle) Chiropsalmus quadrumanus (sea wasp) and Physalia physalis (Portuguese man-of-war) were used in the study. It was found that many of the chemicals traditionally used to treat jellyfish stings stimulated nematocyst discharge and did not relieve the pain. However there was immediate relief when a common anesthetic lidocaine was sprayed on the skin of testers in contact with jellyfish tentacles. Initial exposure of tentacle suspensions to lidocaine prevented the nematocyst discharge by subsequent exposure to acetic acid ethanol ammonia or bromelain. Thus lidocaine in addition to acting as an anesthetic on skin in contact with jellyfish tentacles inhibited nematocyst discharge possibly by blocking sodium and/or calcium channels of the nematocytes.

[Biological and immunological characteristics of the poison of Bothrops cotiara (Serpentes: Viperidae)]

Bothrops cotiara is a venomous snake sporadically found in the province of Misiones in Argentina, South of Brazil and Paraguay. Data on the clinics of the envenomation produced by its bite and on its venom are scarce. There is no information on the neutralizing capacity of the antivenoms available. In this study, the lethal potency, hemorrhagic, necrotizing, coagulant and thrombin-like, defibrinogenating, indirect hemolytic and fibrinolytic activities of the venom of B. cotiara specimens from the province of Misiones were determined. The toxic activities were within the range of those described for the other Bothrops species from Argentina, and the electrophoretic and chromatographic studies showed similarities with those described for the other bothropic venoms. The immunochemical reactivity of six South American anti Viper antivenoms (ELISA) have a strong reactivity with all the antivenoms studied. The neutralizing capacity of three of these therapeutic antivenoms against the lethal potency and hemorrhagic, necrotizing, coagulant, thrombin-like and hemolytic activities showed a very close neutralizing capacity. Our data strongly suggest that the antivenoms for therapeutic use available in this area of South America are useful to neutralize the toxic and enzymatic activities of the venom of this uncommon specie of Bothrops.

Enrichment of the antibodies against the C-terminus of Taiwan cobra cobrotoxin using dimeric glutaraldehyde-modified toxin as an immunogen

The repertoire of antibodies producing by immunizing rabbits with cobrotoxin and dimeric glutaraldehyde-modified cobrotoxin (dGA-cobrotoxin) was analyzed by studying the immunoreactivity of the two antibody preparations toward cobrotoxin, GA-cobrotoxin and recombinant cobrotoxin. The results of enzyme-linked immunoassay revealed that the two antibody preparations exhibited a higher reactivity against their cognate antigen. Moreover, different behavior was observed for the reactivity of the two antibody preparations against GA-cobrotoxin and recombinant cobrotoxin. Notably, distortion of disulfide linkages at the C-terminus resulted in a reduced decrease in the antigenic activity of recombinant cobrotoxin toward anti-cobrotoxin antibodies compared to anti-dGA-cobrotoxin antibodies. Affinity purification of the antibodies against the C-terminus of cobrotoxin revealed that its amount represented 77% and 35.5% of the total anti-dGA-cobrotoxin antibodies and the total anti-cobrotoxin antibodies, respectively. These findings suggest that the antibody preparation elicited by dGA-cobrotoxin enriches the content of antibodies recognizes the C-terminal region of native cobrotoxin.

[Acute management of patients bitten by poisonous snakes]

The management of poisonous snake bites includes first aid and clinical medical treatment. First aid consists of reassurement of the patient, immobilisation of the bitten limb and rapid transport to the nearest hospital to monitor the vital functions. In no case suction, incision or tight bandages should be applied. The degree of envenomation can be classified in three categories depending on the spread of the symptoms: no symptoms, only local non-progressive symptoms, and systemic or local rapidly progressive symptoms (severe envenomation). Antivenin therapy is indicated in severe envenomation. Because of the risk of anaphylactic reactions or serum sickness, antivenin should be given with great caution. Antibiotic therapy and tetanus prophylaxis are advised in all cases. Immediate consultation with the National Intoxication Centre of the Rijksinstitut voor Volksgezondheid en Milieu (RIVM) is always warranted; telephone: 030-2748888. In a national protocol, which is available at the RIVM, the Harbour Hospital Rotterdam, the Academic Medical Centre and Artis Zoo Amsterdam, the correct management of snake bites is described. An overview of all antivenins available in the Netherlands is also given in this protocol.

Evidence showing a different repertoire of antibodies against unfolded cobrotoxin in anticobrotoxin and anti-reduced and S-carboxymethylated cobrotoxin antisera

Antibodies which specifically reacted with reduced and S-carboxy-methylated(RCM) cobrotoxin were purified from anticobrotoxin antisera and anti-RCM-cobrotoxin antisera, respectively. Results using a competitive immunoassay revealed that the antibodies from anti-RCM-cobrotoxin antisera had a greater affinity for RCM-cobrotoxin than for cobrotoxin. Whereas the reactivity of the antibodies from the anticobrotoxin antisera toward cobrotoxin and RCM-cobrotoxin had a reversed order of binding. In contrast to observations made with S. aureus V8 protease-digest hydrolysates, the antigenic structures of RCM-cobrotoxin recognized by antibodies from anti-RCM-cobrotoxin antisera were notably affected following hydrolysis of RCM-cobrotoxin with chymotrypsin. Moreover, the chymotryptic hydrolysates showed a comparable reactivity as RCM-cobrotoxin toward the antibodies purified from anticobrotoxin antibodies, but a decrease in antigenicity with the V8 protease hydrolysates. These results reveal that the repertoire of antibodies against the unfolded cobrotoxin are not the same in anticobrotoxin and anti-RCM-cobrotoxin antisera. Moreover, it suggests that the repertoire of antibodies from the different sources against the same antigen can be differentiated by measurement of their reactivities with the proteolytic hydrolysates of the antigen.