Biology subjects

Alsolaiss, J.

Publications and source records attributed to Alsolaiss, J..

6 recordsLinked to original sources

bioRxiv2022

Exploring the utility of ssDNA aptamers directed against snake venom toxins as new therapeutics for tropical snakebite envenoming

Snakebite is a neglected tropical disease that causes considerable death and disability in the tropical world. Although snakebite can cause a variety of pathologies in victims, haemotoxic effects are particularly common and are typically characterised by haemorrhage and/or venom-induced consumption coagulopathy. Antivenoms are the mainstay therapy for treating the toxic effects of snakebite, but despite saving thousands of lives annually, these therapies are associated with limited cross-snake species efficacy due to venom variation, which ultimately restricts their therapeutic utility to particular geographical regions. In this study, we sought to explore the potential of ssDNA aptamers as toxin-specific inhibitory alternatives to antibodies. As a proof of principle model, we selected snake venom serine protease toxins, which are responsible for contributing to venom-induced coagulopathy following snakebite envenoming, as our target. Using SELEX technology, we selected ssDNA aptamers against recombinantly expressed versions of the fibrinogenolytic SVSPs Ancrod from the venom of Calloselasma rhodostoma and Batroxobin from Bothrops atrox. From the resulting pool of specific ssDNA aptamers directed against each target, we identified candidates that exhibited low nanomolar binding affinities to their targets. Downstream ALISA, fibrinogenolysis, and coagulation profiling experiments demonstrated that the candidate aptamers were able to recognise native and recombinant SVSP toxins and inhibit toxin- and venom-induced prolongation of plasma clotting times and consumption of fibrinogen, with inhibitory potencies highly comparable to commercial polyvalent antivenoms. Our findings demonstrate that rationally selected toxin-specific aptamers can exhibit broad in vitro cross-reactivity against toxins found in different snake venoms and are capable of inhibiting toxins in pathologically relevant in vitro and ex vivo models of venom activity. These data highlight the potential utility of ssDNA aptamers as novel toxin-inhibiting therapeutics of value for tackling snakebite envenoming.

pharmacology and toxicology↗

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

Exploring the utility of recombinantly expressed snake venom serine protease toxins as immunogens for generating experimental snakebite antivenoms

Snakebite is a neglected tropical disease that causes high rates of global mortality and morbidity. Although snakebite can cause a variety of pathologies in victims, haemotoxic effects are particularly common and are typically characterised by haemorrhage and/or venom-induced consumption coagulopathy. Despite polyclonal antibody-based antivenoms being the mainstay life-saving therapy for snakebite, they are associated with limited cross-snake species efficacy, as there is often extensive toxin variation between snake venoms, including those used as immunogens for antivenom production. This restricts the therapeutic utility of any antivenom to certain geographical regions. In this study, we explored the feasibility of using recombinantly expressed toxins as immunogens to stimulate focused, pathology-specific, antibodies to broadly counteract specific toxins associated with snakebite envenoming. Three snake venom serine proteases (SVSP) toxins, sourced from geographically diverse and medically important viper snake venoms were successfully expressed in HEK293F mammalian cells and used for murine immunisation. Analyses of the resulting antibody responses revealed that ancrod and RVV-V stimulated the strongest immune responses, and that experimental antivenoms directed against these recombinant SVSP toxins, and a mixture of the three different immunogens, extensively recognised and exhibited immunological binding towards a variety of native snake venoms. While the experimental antivenoms showed some reduction in abnormal clotting parameters stimulated by the toxin immunogens and crude venom, specifically reducing the depletion of fibrinogen levels and prolongation of prothrombin times, fibrinogen degradation experiments revealed they broadly protected against venom- and toxin-induced fibrinogenolytic functional activities. Overall, our findings further strengthen the case for the use of recombinant venom toxins as supplemental immunogens to stimulate focused and desirable antibody responses capable of neutralising venom-induced pathological effects, and therefore potentially circumventing some of the limitations associated with current snakebite therapies.

immunology↗

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↗

bioRxiv2020

A combination of two small molecule toxin inhibitors provides pancontinental preclinical efficacy against viper snakebite

Snakebite is a medical emergency causing high mortality and morbidity in rural tropical communities that typically experience delayed access to unaffordable therapeutics. Viperid snakes are responsible for the majority of envenomings, but extensive interspecific variation in venom composition dictates that different antivenom treatments are used in different parts of the world, resulting in clinical and fiscal snakebite management challenges. Here, we show that a number of repurposed Phase 2-approved small molecules are capable of broadly neutralizing distinct viper venom bioactivities in vitro by inhibiting different enzymatic toxin families. Furthermore, using multiple in vivo models of envenoming, we demonstrate that a single dose of a rationally-selected dual inhibitor combination consisting of marimastat and varespladib prevents lethality caused by venom from the most medically-important vipers of Africa, South Asia and Central America. Our findings strongly support the translation of combinations of safe and affordable enzyme inhibitors as novel broad-spectrum therapeutics for snakebite.

pharmacology and toxicology↗

bioRxiv2019

Preclinical validation of a repurposed metal chelator as a community-based therapeutic for hemotoxic snakebite

Snakebite envenoming causes 138,000 deaths annually and ~400,000 victims are left with permanent disabilities. Envenoming by saw-scaled vipers (Viperidae: Echis) leads to systemic hemorrhage and coagulopathy, and represents a major cause of snakebite mortality and morbidity in Africa and Asia. The only specific treatment for snakebite, antivenom, has poor specificity, low affordability, and must be administered in clinical settings due to its intravenous delivery and high rates of adverse reactions. This requirement results in major treatment delays in resource-poor regions and impacts substantially on patient outcomes following envenoming. Here we investigated the value of metal chelators as novel community-based therapeutics for snakebite. Among the tested chelators, dimercaprol (British anti-Lewisite) and its derivative 2,3-dimercapto-1-propanesulfonic acid (DMPS), were found to potently antagonize the activity of Zn2+-dependent snake venom metalloproteinase toxins in vitro. Moreover, DMPS prolonged or conferred complete survival in murine preclinical models of envenoming against a variety of saw-scaled viper venoms. DMPS also significantly extended survival in a challenge and treat model, where drug administration was delayed post-venom injection, and the oral administration of this chelator provided partial protection against envenoming. Finally, the potential clinical scenario of early oral DMPS therapy combined with a later, delayed, intravenous dose of conventional antivenom provided prolonged protection against the lethal effects of envenoming in vivo. Our findings demonstrate that safe and affordable repurposed metal chelators effectively neutralize saw-scaled viper venoms in vitro and in vivo and highlight the great promise of DMPS as a novel, community-based, early therapeutic intervention for hemotoxic snakebite envenoming.

pharmacology and toxicology↗