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An indirect haemolytic assay for assessing antivenoms
I H al-Abdulla1, A M Sidki, J Landon
1Department of Chemical Pathology, St. Bartholomew's Hospital, London, U.K.
Summary
A new ovine antivenom is over five times more effective at neutralizing South American rattlesnake venom than a standard equine antivenom. This venom neutralization assay shows promise for evaluating antivenom efficacy.
Area of Science:
- Toxicology
- Immunology
- Biochemistry
Background:
- Snakebite envenomation remains a significant global health issue, particularly in regions with limited access to effective antivenoms.
- The South American rattlesnake (Crotalus durissus terrificus) possesses potent venom that causes significant local and systemic effects, including hemolysis.
- Assessing the efficacy of antivenoms is crucial for guiding treatment and developing improved therapies.
Purpose of the Study:
- To develop and validate a spectrophotometric assay for quantifying venom-induced hemolysis.
- To compare the efficacy of a novel ovine antivenom against the venom of Crotalus durissus terrificus, in comparison to a commercially available equine antivenom.
- To evaluate the cross-neutralization capabilities of the ovine antivenom against other Crotalus and Bothrops species venoms.
Main Methods:
- A hemolysis assay was established using human erythrocytes, venom, and antivenom dilutions incubated at 37°C.
- Liberated hemoglobin was quantified spectrophotometrically to measure the degree of hemolysis.
- The assay was employed to assess an ovine antivenom and an equine Wyeth polyvalent antivenin against Crotalus durissus terrificus venom.
Main Results:
- The ovine antivenom demonstrated over five-fold greater efficacy in neutralizing Crotalus durissus terrificus venom compared to the equine antivenom.
- The ovine antivenom also exhibited neutralizing activity against the venoms of Crotalus atrox and Bothrops atrox.
- Antivenoms raised against other Crotalus and Bothrops species showed limited efficacy in neutralizing the hemolytic activity of C. d. terrificus venom.
Conclusions:
- The developed spectrophotometric assay is a sensitive and effective tool for evaluating antivenom potency against venom-induced hemolysis.
- The novel ovine antivenom represents a significant advancement in efficacy for treating envenomation by Crotalus durissus terrificus.
- Specificity of antivenom is critical, as cross-neutralization against related species' venoms was limited, highlighting the need for targeted antivenom development.