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. 2025 Aug 4;19(8):e0013371.
doi: 10.1371/journal.pntd.0013371. eCollection 2025 Aug.

Preclinical evaluation of the neutralising efficacy of three antivenoms against the venoms of the recently taxonomically partitioned E. ocellatus and E. romani

Rebecca J Edge  1   2 , Amy E Marriott  1   2 , Molly Keen  1 , Tiffany Xie  3 , Edouard P Crittenden  1 , Charlotte A Dawson  1 , Mark C Wilkinson  1 , Wolfgang Wüster  4 , Nicholas R Casewell  1 , Stuart Ainsworth  1   2 , Stefanie K Menzies  1   5
Affiliations

Preclinical evaluation of the neutralising efficacy of three antivenoms against the venoms of the recently taxonomically partitioned E. ocellatus and E. romani

Rebecca J Edge et al. PLoS Negl Trop Dis. .

Abstract

Snakebite is a significant public health concern in Africa, with the viperid species Echis ocellatus being responsible for the majority of snakebite deaths in West Africa. Recently E. ocellatus underwent taxonomic revision and was split into two species, E. ocellatus sensu stricto and E. romani, leading to questions regarding differences in venom bioactivities and the efficacy of antivenoms indicated for treatment of 'E. ocellatus' envenoming against the two redefined species. Using a range of in vitro assays we compared the toxin activities of the two species and the venom-neutralising efficacy of three antivenoms (EchiTAbG, SAIMR Echis and Echiven) raised against 'E. ocellatus'. We then used murine preclinical assays to compare the in vivo efficacy of these antivenoms against E. romani and E. ocellatus s. str venoms. Mitochondrial barcoding of snake skins and venom revealed that E. romani, and not E. ocellatus, is used in the manufacture of several antivenoms raised against 'E. ocellatus'. There were also a number of differences in specific toxin activity between the venoms of the two species in the three in vitro assays utilised in this study.; E. ocellatus (Ghana) had the strongest phospholipase A2 (PLA2) activity, followed by weak PLA2 activity for E. romani (Cameroon) and insignificant activity by E. romani (Nigeria). E. ocellatus (Ghana) and E. romani (Nigeria) demonstrated comparable snake venom metalloproteinase activity, whilst E. romani (Cameroon) had reduced, albeit still significant, activity in comparison. However no differences were observed in a plasma clotting assay measuring coagulopathy between the venoms and localities. Venoms from E. ocellatus (Ghana) and E. romani (Cameroon and Nigeria) were all recognised comparably by the three antivenoms, and there were only modest differences between antivenoms in neutralising the various in vitro toxin effects. In murine preclinical assays, each antivenom could neutralise the lethal effects of E. romani (Nigeria), but differences were seen in their comparative potency when the same antivenom doses were tested against E. romani (Cameroon) and E. ocellatus (Ghana). In these comparative potency assays, all three antivenoms were unable to confer 100% survival when tested against E. romani (Cameroon), but SAIMR Echis provided the best protection with 80% survival. When tested against E. ocellatus (Ghana), the comparative doses of SAIMR Echis and Echiven provided 100% protection whereas EchiTAbG failed to prevent lethality beyond three hours. This represents the first detailed analysis of differences between E. ocellatus and E. romani venom bioactivities and the efficacy of existing antivenoms against these two species. Our findings demonstrate that EchiTAbG, SAIMR Echis and Echiven antivenoms are preclinically efficacious against the lethal effects of E. ocellatus and E. romani venom across a number of localities.

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Conflict of interest statement

I have read the journal's policy and the authors of this manuscript have the following competing interests: Stefanie Menzies and Nicholas Casewell communicated with the antivenom manufacturer VINS Bioproducts to obtain a sample of Echiven antivenom for testing. The antivenom manufacturer had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript. The Centre for Snakebite Research and Interventions (CSRI) at LSTM was historically involved in the development of EchiTAbG and EchiTAb-Plus-ICP antivenoms, though none of the authors from CSRI were directly involved in this work. Nicholas Casewell was previously employed by the manufacturer of EchiTAbG antivenom (MicroPharm, UK) between 2010 and 2012. Nicholas Casewell and Charlotte Dawson are currently collaborators of the EchiTAbG manufacturer MicroPharm, UK. MicroPharm had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript.

Figures

Fig 1
Fig 1. Maximum likelihood phylogeny of the Echis ocellatus group inferred from 1433 base pairs of mitochondrial CYTB and NADH4 sequence.
Node labels next to major nodes represent %bootstrap support.
Fig 2
Fig 2. PLA2 activity of E. ocellatus s. str. and E. romani venoms and their neutralisation by the three different antivenoms.
A: PLA2 activity of E. ocellatus (GHA = Ghana) and E. romani (CAM = Cameroon and NGA = Nigeria). Samples were subtracted for background and converted to activity in (U/mL)/μg by extrapolation from a bee venom standard curve. Data show the mean of three replicates and error bars represent standard deviation. Statistical differences in activity compared to ‘buffer only’ were determined by one-way ANOVA, with venom specific p values indicated above the bar (* indicates p < 0.05, *** indicates p < 0.001, ns = not significant, p > 0.05). B -C: Neutralisation of (B) E. ocellatus (Ghana), (C) E. romani (Cameroon) PLA2 activity by the three antivenoms EchiTAbG (ETG), SAIMR Echis (SE) and Echiven (EV) at different doses, expressed as a percentage of a no-antivenom control showing 100% activity. Data show the mean of three replicates and error bars represent standard deviation. Two-way ANOVA was performed to compare differences in PLA2 activity at the 0.78 μL dose of antivenoms. * indicates p < 0.05, ** indicates p < 0.01 *** indicates p < 0.001, ns = not significant (p > 0.05).
Fig 3
Fig 3. SVMP activity of E. ocellatus s. str. and E. romani venoms and their neutralisation by the three different antivenoms.
A: SVMP activity of E. ocellatus (GHA = Ghana) and E. romani (CAM = Cameroon and NGA = Nigeria). Data show the mean of four replicates and error bars represent standard deviation. Statistical differences in activity compared to PBS, and between venoms, were determined by one-way ANOVA, with p values against PBS indicated above the bar (**** indicates p < 0.0001), and # indicating significantly lower activity and ^ indicating significantly higher activity. B-D: Neutralisation of (B) E. ocellatus (Ghana), (C) E. romani (Cameroon) and (D) E. romani (Nigeria) SVMP activity by the three antivenoms EchiTAbG (ETG), SAIMR Echis (SE) and Echiven (EV) at different doses, expressed as a percentage of a no antivenom control showing 100% activity. Data show the mean of four replicates and error bars represent standard deviation. One-way ANOVA was performed to compare differences in SVMP activity at the 0.31 μL dose of antivenoms. ns = not significant (p > 0.05).
Fig 4
Fig 4. Plasma clotting activity of E. ocellatus s. str. and E. romani venoms and their neutralisation by the three different antivenoms.
A: Plasma clotting activity of E. ocellatus (GHA = Ghana) and E. romani (CAM = Cameroon and NGA = Nigeria). Data show the mean of four replicates and error bars represent standard deviation. Statistical differences in activity compared to PBS, and between venoms, were determined by one-way ANOVA, with p values against PBS indicated above the bar (**** indicates p < 0.0001). B-D: Neutralisation of (B) E. ocellatus (Ghana), (C) E. romani (Cameroon) and (D) E. romani (Nigeria) plasma clotting activity by the three antivenoms EchiTAbG (ETG), SAIMR Echis (SE) and Echiven (EV) at different doses, expressed as a percentage of a no antivenom control showing 100% activity. Data show the mean of four replicates and error bars represent standard deviation. One-way ANOVA was performed to compare differences in plasma clotting activity at the 0.31 μL dose of antivenoms. **** indicates p < 0.0001, *** indicates p < 0.001, ns = not significant (p > 0.05).
Fig 5
Fig 5. ED100 survival times.
A: E. ocellatus (Ghana) B: E. romani (Cameroon) C: Mean survival time of animals – bars indicate mean survival time and markers indicate individual survival times for each animal. Each experiment used five mice per dose group, challenged with a dose of 5 x venom LD50 and monitored for 6 hours. EchiTAbG shown in grey, SAIMR Echis shown in magenta, Echiven shown in teal.
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References

    1. Gutiérrez JM, Calvete JJ, Habib AG, Harrison RA, Williams DJ, Warrell DA. Snakebite envenoming. Nat Rev Dis Primers. 2017;3:17063. doi: 10.1038/nrdp.2017.63 - DOI - PubMed
    1. Warrell DA, Arnett C. The importance of bites by the saw-scaled or carpet viper (Echis carinatus): epidemiological studies in Nigeria and a review of the world literature. Acta Trop. 1976;33(4):307–41. - PubMed
    1. Pook CE, Joger U, Stümpel N, Wüster W. When continents collide: phylogeny, historical biogeography and systematics of the medically important viper genus Echis (Squamata: Serpentes: Viperidae). Mol Phylogenet Evol. 2009;53(3):792–807. doi: 10.1016/j.ympev.2009.08.002 - DOI - PubMed
    1. Hamza M, Idris MA, Maiyaki MB, Lamorde M, Chippaux J-P, Warrell DA, et al. Cost-Effectiveness of Antivenoms for Snakebite Envenoming in 16 Countries in West Africa. PLoS Negl Trop Dis. 2016;10(3):e0004568. doi: 10.1371/journal.pntd.0004568 - DOI - PMC - PubMed
    1. Abubakar IS, Abubakar SB, Habib AG, Nasidi A, Durfa N, Yusuf PO, et al. Randomised controlled double-blind non-inferiority trial of two antivenoms for saw-scaled or carpet viper (Echis ocellatus) envenoming in Nigeria. PLoS Negl Trop Dis. 2010;4(7):e767. doi: 10.1371/journal.pntd.0000767 - DOI - PMC - PubMed

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