Biology subjects

Westhorpe, A.

Publications and source records attributed to Westhorpe, A..

7 recordsLinked to original sources

bioRxiv2026

Establishment of snake venom gland organoids from a novel family, Colubridae

Non-front-fanged snakes are abundant, diverse and represent approximately 70% of extant snakes. However, there is limited knowledge about most species and their venoms, in part due to the technical and welfare challenges associated with venom extraction, low venom yields, and the lack of cellular models available. Organoids represent an excellent opportunity to overcome these challenges. Here, we establish, for the first time, venom gland organoids from snakes of the Colubridae family and demonstrate the in vitro production of toxins.

bioengineering↗

bioRxiv2026

Repurposed small molecule toxin inhibitors neutralise a diversity of venoms from the Neotropical viperid snake genus Bothrops

Snakebite globally claims more than 100,000 lives per year and results in morbidity for 400,000 survivors. Current treatment uses antibody-based antivenoms which are constrained by their efficacy, safety and cost. In this study we evaluated the efficacy of previously described repurposed drugs against viperid snakes of the medically important Bothrops genus. Despite variable toxin representation and bioactivity across this central and south American genus, we found that the lead inhibitors targeting metalloproteinases (marimastat and DMPS) and phospholipases (varespladib), demonstrated pan-species neutralisation in enzymatic assays, whilst nafamostat (serine protease inhibitor) had variable activity. The metalloproteinase inhibitors protected against the procoagulant and haemorrhagic effects of several venoms in phenotypic assays. Collectively these findings demonstrate that repurposed drugs may be of great value as early interventions for the treatment of bothropic envenoming in the Neotropics and thus provides a strong rationale for their progression into future preclinical and clinical evaluation for snakebite indication.

molecular biology↗

bioRxiv2025

A drug combinational therapy consisting of toxin phospholipase A2 and metalloproteinase inhibitors provides preclinical protection against North American Crotalid snakebite envenoming

BackgroundAcross North America an estimated 3,800-6,500 snakebite envenomings occur annually, resulting in 7-15 deaths and an unknown number of disfigurements and disabilities. Most bites are caused by Crotalid snake species. The variable diversity and toxin complexity of crotalid venoms presents a considerable challenge to developing broadly effective small molecule therapeutics to better treat snakebite in this region. MethodsWe evaluated the ability of three small molecule, toxin inhibiting, repurposed drugs to inhibit the venom activities of six medically important crotalid snake species (Agkistrodon contortrix, Crotalus atrox, C. adamanteus, C. horridus, C. scutulatus and Sistrurus miliarius). These drugs target two pathologically relevant venom toxin families, the snake venom metalloproteinases (SVMPs; marimastat and DMPS) and phospholipases A2 (PLA2s; varespladib), and venom inhibition was measured using in vitro enzymatic and phenotypic plasma coagulation assays. Thereafter we evaluated the efficacy of individual drugs and dual drug combinations in in vivo preclinical models of snakebite envenoming, using both preincubation and rescue model formats. ResultsIn vitro bioassays demonstrated that the selected small molecules showed potent inhibition of the enzymatic activity of different toxin families to the nanomolar (varespladib vs PLA2 and marimastat vs SVMP) or micromolar (DMPS vs SVMP) level. Three of the venoms had anticoagulant activity, which varespladib restored to normal coagulation profiles, suggesting this activity is mostly driven by PLA2 toxins. Preclinical experiments revealed that pre-incubation of representative venoms with single drugs was insufficient to completely protect against lethality, except for varespladib against C. scutulatus. Superior efficacy was observed when drugs were used in a combination approach, with the combination of marimastat and varespladib providing greatest protection against lethality in both pre-incubation and rescue models. ConclusionsVenom variation among snake species makes the development of generic snakebite therapeutics challenging. In this study we showed that while SVMP and PLA2 inhibiting drugs show inhibitory potency against diverse North American snake venoms, drug combinations consisting of an SVMP inhibitor together with a PLA2 inhibitor are required to confer broad in vivo protection against lethality caused by envenoming. This study highlights the potential long-term value of drug combinations as next-generation therapeutics for snakebite envenoming.

molecular biology↗

bioRxiv2024

Snake venom metalloproteinases are predominantly responsible for the cytotoxic effects of certain African viper venoms

AbstractSnakebite envenoming is a neglected tropical disease that causes substantial mortality and morbidity globally. The puff adder (Bitis arietans) and saw-scaled viper (Echis romani) have cytotoxic venoms that cause permanent injury via tissue-destructive dermonecrosis around the bite site. Identification of cytotoxic toxins within these venoms will allow development of targeted treatments, such as small molecule inhibitors or monoclonal antibodies to prevent snakebite morbidity. Venoms from both species were fractionated using gel filtration chromatography, and a combination of cell-based cytotoxicity approaches, SDS-PAGE gel electrophoresis, and enzymatic assays were applied to identify venom cytotoxins in the resulting fractions. Our results indicated that snake venom metalloproteinase (SVMP) toxins are predominately responsible for causing cytotoxic effects across both venoms, but that the PII subclass of SVMPs are likely the main driver of cytotoxicity following envenoming by B. arietans, whilst the structurally distinct PIII subclass of SVMPs are responsible for conveying this effect in E. romani venom. Identification of distinct SVMPs as the primary cytotoxicity-causing toxins in these two African viper venoms will facilitate the future design and development of novel therapeutics targeting these medically important venoms, which in turn could help to mitigate the severe life and limb threatening consequences of tropical snakebite. Key ContributionSVMP toxins were identified as the primary cytotoxicity-causing toxins in the venoms of the puff adder (Bitis arietans) and saw-scaled viper (Echis romani); PII and PIII SVMPs, respectively. This cytotoxicity can be prevented using the metalloproteinase-inhibiting chelator EDTA, suggesting targeted drugs/antibodies may be a viable option for future treatment.

pharmacology and toxicology↗

bioRxiv2024

Intraspecific venom variation in the medically important puff adder (Bitis arietans): comparative venom gland transcriptomics, in vitro venom activity and immunological recognition by antivenom

BackgroundVariation in snake venoms is well documented, both between and within species, with intraspecific venom variation often correlated with geographically distinct populations. The puff adder, Bitis arietans, is found widely distributed across sub-Saharan Africa and into the Arabian Peninsula where it is considered a leading cause of the [~]310,000 annual snakebites across the region, with its venom capable of causing substantial morbidity and mortality. Despite its medical importance and wide geographic distribution, there is little known about venom variation between different B. arietans populations and the potential implications of this variation on antivenom efficacy. MethodologyWe applied a range of analyses, including venom gland transcriptomics, in vitro enzymatic assays and reverse phase chromatography to comparatively analyse B. arietans venoms originating from Nigeria, Tanzania, and South Africa. Immunological assays and in vitro enzymatic neutralisation assays were then applied to investigate the impact of venom variation on the potential efficacy of three antivenom products; SAIMR Polyvalent, EchiTAb-Plus and Fav-Afrique. FindingsThrough the first comparison of venom gland transcriptomes of B. arietans from three geographically distinct regions (Nigeria, Tanzania, and South Africa), we identified substantial variation in toxin expression. Findings of venom variation were further supported by chromatographic venom profiling, and the application of enzymatic assays to quantify the activity of three pathologically relevant toxin families. However, the use of western blotting, ELISA, and in vitro enzymatic inhibition assays revealed that variation within B. arietans venom does not appear to substantially impact upon the efficacy of three African polyvalent antivenoms. ConclusionsThe large distribution and medical importance of B. arietans makes this species ideal for understanding venom variation and the impact this has on therapeutic efficacy. The findings in this study highlight the likelihood for considerable venom toxin variation across the range of B. arietans, but that this may not dramatically impact upon the utility of treatment available in the region. Author SummaryThe puff adder (Bitis arietans) is found across sub-Saharan Africa and the Arabian Peninsula and is capable of causing life threatening pathology due to its potent venom. The extensive range of B. arietans exposes populations to different ecological pressures which may impact upon the composition of venom toxins. In this study, we examined the venom composition of B. arietans from three countries separated by large geographic distance: Nigeria, Tanzanian and South Africa. By integrating venom gland transcriptomes, venom chromatography, and in vitro functional assays to profile B. arietans venom composition, we uncovered extensive variation between the three locales. Given that venom variation can have a significant impact on the efficacy of antivenom treatment, we also investigated the ability of three African antivenoms to recognise and inhibit in vitro venom activity. Through these analyses, we were able to determine that venom variation did not have a substantial impact on the neutralising effect of selected antivenoms. This study has highlighted the potentially extensive venom variation found across the range of B. arietans and initiated valuable investigations into the efficacy of African antivenoms to protect human populations vulnerable to snakebite envenoming.

molecular biology↗

bioRxiv2022

Two snakebite antivenoms have potential to reduce Eswatini's dependency upon a single, increasingly unavailable product: results of preclinical efficacy testing

BackgroundSnakebite is a major public health concern in Eswatini, where treatment relies upon one antivenom - SAIMR Polyvalent. Although effective in treating snakebite, SAIMR Polyvalent is difficult to source outside its manufacturing country (South Africa) and is dauntingly expensive. We compared the preclinical venom-neutralising efficacy of two alternative antivenoms and SAIMR Polyvalent against the lethal and tissue-destructive effects of venoms from five species of medically important snakes using in vivo murine assays. The test antivenoms were Panafrican manufactured by Instituto Clodomiro Picado and PANAF manufactured by Premium Serums & Vaccines. Principal FindingsIn vivo murine preclinical studies identified both test antivenoms were equally or more effective than SAIMR Polyvalent at neutralising lethal and tissue-destructive effects of Naja mossambica venom. Both test antivenoms were less effective than SAIMR Polyvalent at neutralising the lethal effects of Bitis arietans, Dendroaspis polylepis, Hemachatus haemachatus and Naja annulifera venoms, but similarly effective at neutralising tissue damage induced by B. arietans and H. haemachatus venoms. In vitro immunological assays identified that IgG titres and toxin-specificities of the test antivenoms were comparable to SAIMR Polyvalent. Plasma clotting disturbances by H. haemachatus and N. mossambica were effectively neutralised by the test antivenoms, whereas SAIMR Polyvalent failed to neutralise this bioactivity of N. mossambica venom. The SVMP activity of B. arietans venom was equally reduced by all three antivenoms. The PLA2 activities of H. haemachatus and N. mossambica were effectively neutralised by all three antivenoms. ConclusionsPanafrican outperformed PANAF, though both were less poly-specifically effective than SAIMR Polyvalent. The efficacy of these antivenoms against the lethal and tissue-destructive effects of N. mossambica venom, the most common biting species in Eswatini, identify that Panafrican and PANAF antivenoms offer effective alternatives to SAIMR for the treatment of snakebite in Eswatini, and potentially for neighbouring countries. Author SummaryTreatment of snakebite in Eswatini is reliant upon a single antivenom (SAIMR Polyvalent) manufactured in South Africa. This highly effective product is increasingly difficult to source and is expensive - alternative/additional antivenoms are urgently required to improve patient outcomes following snake envenoming. Using murine preclinical venom toxicity and antivenom efficacy assays, we identified two alternative antivenoms whose venom-neutralising characteristics, while less poly-specifically effective than SAIMR Polyvalent, were as effective against the lethal and tissue-destructive effects of the most common biting snake in Eswatini - Naja mossambica. This murine data, already shared with the Eswatini Ministry of Health, supports and justifies human testing of these two antivenoms in Eswatini because increasing the availability of effective and affordable treatments could resolve the current medical dependency of Eswatini snakebite patients upon a single, rarely available and expensive product.

pharmacology and toxicology↗

bioRxiv2022

In vitro and in vivo venom-inhibition assays identify metalloproteinase-inhibiting drugs as potential treatments for snakebite envenoming by Dispholidus typus

Snakebite envenoming affects more than 250,000 people annually in sub-Saharan Africa. Envenoming by Dispholidus typus (boomslang) results in venom induced consumption coagulopathy, whereby highly abundant prothrombin-activating snake venom metalloproteinases (SVMPs) consume clotting factors and deplete fibrinogen. The only available treatment for D. typus envenoming is the monovalent SAIMR Boomslang antivenom. Treatment options are urgently required because this antivenom is often difficult to source and, at $6,000/vial, typically unaffordable for most snakebite patients. We therefore investigated the in vitro and in vivo preclinical efficacy of four SVMP inhibitors to neutralise the effects of D. typus venom; the matrix metalloproteinase inhibitors marimastat and prinomastat, and the metal chelators dimercaprol and DMPS. The venom of D. typus exhibited an SVMP-driven procoagulant phenotype in vitro. Marimastat and prinomastat demonstrated equipotent inhibition of the SVMP-mediated procoagulant activity of the venom in vitro, whereas dimercaprol and DMPS showed considerably lower potency. However, when tested in preclinical murine models of envenomation, DMPS and marimastat demonstrated partial protection against venom lethality, demonstrated by prolonged survival times of experimental animals, whereas dimercaprol and prinomastat failed to confer any protection at the doses tested. The results presented here demonstrate that DMPS and marimastat show potential as novel small molecule-based therapeutics for D. typus snakebite envenomation. These two drugs have been previously shown to be effective against Echis ocellatus venom induced consumption coagulopathy (VICC) in preclinical models, and thus we conclude that marimastat and DMPS may be valuable early intervention therapeutics to broadly treat VICC following snakebite envenoming in sub-Saharan Africa.

pharmacology and toxicology↗