Naja Nigricollis Venom Research Articles

Exploring the Antisnake Venom Potential of Zingiber officinale and its Bioactive Compounds Against Naja nigricollis Venom Through Computational Approaches and Experimental Validation.

Snakebite envenomation remains a significant medical challenge, particularly in tropical and subtropical regions. The present study investigates the inhibitory potential of Zingiber officinale (ginger) and its bioactive compounds against Naja nigricollis venom using in silico approaches and animal models. No protection was observed in the in vivo studies but the extract of the plant was able to prolong the time of death with mean survival time ranging from 2.01-2.83 hours. In terms of the in vitro studies, the extract was able to significantly (p<0.05) detoxify the N. nigricollis venom by 80 % at the graded doses; standard antisnake venom (ASV) offered 100 % protection to mice. Molecular docking analysis revealed strong binding affinities between the bioactive compounds and the PLA2 enzyme, indicating potential inhibitory effects. The stability and dynamics of the protein-ligand complexes were further validated through molecular dynamics (MD) simulations, which confirmed the persistence of these interactions over time. In conclusion, the findings suggest that the bioactive compounds from Z. officinale could serve as promising inhibitors of PLA2, providing a foundation for the development of novel snakebite envenomation therapies.

Comparison of the intrageneric neutralization scope of monospecific, bispecific/monogeneric and polyspecific/monogeneric antisera raised in horses immunized with sub-Saharan African snake venoms.

Snakebite envenomation inflicts a high burden of mortality and morbidity in sub-Saharan Africa. Antivenoms are the mainstay in the therapy of envenomation, and there is an urgent need to develop antivenoms of broad neutralizing efficacy for this region. The venoms used as immunogens to manufacture snake antivenoms are normally selected considering their medical importance and availability. Additionally, their ability to induce antibody responses with high neutralizing capability should be considered, an issue that involves the immunization scheme and the animal species being immunized. Using the lethality neutralization assay in mice, we compared the intrageneric neutralization scope of antisera generated by immunization of horses with monospecific, bispecific/monogeneric, and polyspecific/monogeneric immunogens formulated with venoms of Bitis spp., Echis spp., Dendroaspis spp., spitting Naja spp. or non-spitting Naja spp. It was found that the antisera raised by all the immunogens were able to neutralize the homologous venoms and, with a single exception, the heterologous congeneric venoms (considering spitting and non-spitting Naja separately). In general, the polyspecific antisera of Bitis spp, Echis spp, and Dendroaspis spp gave the best neutralization profile against venoms of these genera. For spitting Naja venoms, there were no significant differences in the neutralizing ability between monospecific, bispecific and polyspecific antisera. A similar result was obtained in the case of non-spitting Naja venoms, except that polyspecific antiserum was more effective against the venoms of N. melanoleuca and N. nivea as compared to the monospecific antiserum. The use of polyspecific immunogens is the best alternative to produce monogeneric antivenoms with wide neutralizing coverage against venoms of sub-Saharan African snakes of the Bitis, Echis, Naja (non-spitting) and Dendroaspis genera. On the other hand, a monospecific immunogen composed of venom of Naja nigricollis is suitable to produce a monogeneric antivenom with wide neutralizing coverage against venoms of spitting Naja spp. These findings can be used in the design of antivenoms of wide neutralizing scope for sub-Saharan Africa.

Kaempferol alleviates neurodegenerative disorders induced by Naja nigricollis venom via mechanisms of antioxidants, anti-inflammatory, dopaminergic and neuronal functions

Naja nigricollis venom (NnV) contains neurotoxins that influence neurological functions. Kaempferol is a bioactive compound present in edible plants with numerous pharmacological activities. This study investigated the ameliorative potential of kaempferol against NnV-induced neurotoxicity in rats. Fifty male Wistar rats were randomized into five groups (n = 10). Group 1 rats were the control while 1.0 mg/kg−1 (LD50) of NnV was injected intraperitoneally into rats in groups 2–5 to observed neurotoxicity. Group 2 was untreated post envenomation, while groups 3–5 were treated with polyvalent antivenom, 4 and 8 mg/kg of kaempferol, respectively. The biochemical analysis, neurotoxicity, and pathomorphological defects were assessed in the brain of the envenomed treated rats. Envenomation with NnV elevated oxidative and inflammatory biomarkers, and induced neurotoxicity accompanied with neurobehavioral deficits, and severe pathohistological defects were seen in the brain of untreated envenomed rats. However, treatment with kaempferol significantly (p < 0.05) decreased malondialdehyde (MDA) levels and upregulated levels of reduce glutathione (GSH) antioxidant including superoxide dismutase (SOD) and glutathione peroxidase (GPX) antioxidant enzymes, while inflammatory biomarkers; nitric oxide (NO) levels and myeloperoxidase (MPO) activity significantly decreased in envenomed treated groups. Kaempferol upregulated dopamine concentration with significant suppression of acetylcholinesterase (AchE) activity, and restored neurobehavioral and locomotor activities in envenomed treated rats. Also, severe pathomorphological alterations observed in the cortex of the brain were attenuated after kaempferol treatment. The underlaying ameliorative mechanisms of kaempferol are linked to its antioxidant activity, lipid peroxidation inhibition, anti-inflammatory activity, acetylcholinesterase suppression, and alleviation of dopamine system and neurobehavioral abilities.

Dermonecrosis caused by a spitting cobra snakebite results from toxin potentiation and is prevented by the repurposed drug varespladib

Snakebite envenoming is a neglected tropical disease that causes substantial mortality and morbidity globally. The venom of African spitting cobras often causes permanent injury via tissue-destructive dermonecrosis at the bite site, which is ineffectively treated by current antivenoms. To address this therapeutic gap, we identified the etiological venom toxins in Naja nigricollis venom responsible for causing local dermonecrosis. While cytotoxic three-finger toxins were primarily responsible for causing spitting cobra cytotoxicity in cultured keratinocytes, their potentiation by phospholipases A2 toxins was essential to cause dermonecrosis in vivo. This evidence of probable toxin synergism suggests that a single toxin-family inhibiting drug could prevent local envenoming. We show that local injection with the repurposed phospholipase A2-inhibiting drug varespladib significantly prevents local tissue damage caused by several spitting cobra venoms in murine models of envenoming. Our findings therefore provide a therapeutic strategy that may effectively prevent life-changing morbidity caused by snakebite in rural Africa.

Kaempferol mitigates reproductive dysfunctions induced by Naja nigricollis venom through antioxidant system and anti-inflammatory response in male rats

Naja nigricollis Venom (NnV) contains complex toxins that affects various vital systems functions after envenoming. The venom toxins have been reported to induce male reproductive disorders in envenomed rats. This present study explored the ameliorative potential of kaempferol on NnV-induced male reproductive toxicity. Fifty male wistar rats were sorted randomly into five groups (n = 10) for this study. Group 1 were noted as the control, while rats in groups 2 to 5 were injected with LD50 of NnV (1.0 mg/kg bw; i.p.). Group 2 was left untreated post envenomation while group 3 was treated with 0.2 ml of polyvalent antivenom. Groups 4 and 5 were treated with 4 and 8 mg/kg of kaempferol, respectively. NnV caused substantial reduction in concentrations of follicle stimulating hormone, testosterone and luteinizing hormone, while sperm motility, volume and counts significantly (p < 0.05) decreased in envenomed untreated rats. The venom enhanced malondialdehyde levels and substantially decreased glutathione levels, superoxide dismutase and glutathione peroxidase activities in the testes and epididymis of envenomed untreated rats. Additionally, epididymal and testicular myeloperoxidase activity and nitric oxide levels were elevated which substantiated severe morphological defects noticed in the reproductive organs. However, treatment of envenomed rats with kaempferol normalized the reproductive hormones with significant improvement on sperm functional parameters. Elevated inflammatory and oxidative stress biomarkers in testis and epididymis were suppressed post kaempferol treatment. Severe histopathological lesions in the epididymal and testicular tissues were ameliorated in the envenomed treated groups. Results highlights the significance of kaempferol in mitigating reproductive toxicity induced after snakebite envenoming.

Exploring the ex vivo effects of Naja mossambica venom on the ultrastructure and viscoelastic properties of human blood

BackgroundVenomous snake bites have been listed as a neglected tropical disease by the World Health Organization. The Mozambique spitting cobra (Naja mossambica) is found in Sub-Saharan African countries, and its venom has been identified to predominantly result in cytotoxic effects. However, there is limited evidence on the possible hemotoxic effects of this venom on human blood. ObjectivesIn this cross-sectional study, we investigated how Mozambique spitting cobra venom affects blood clot formation. MethodsCell morphology and clot architecture were studied by using microscopy techniques. We also studied the effects of the venom on platelets by measuring platelet activity with the global thrombosis test, followed by analyzing the viscoelasticity with thromboelastography using a 0.025 ng/μL venom concentration. ResultsThe most prominent findings indicated that the viscoelastic profile in the venom-treated blood samples formed an unstable and elastic clot. The clot architecture seen with the scanning electron microscopy analysis showed an altered fibrin network and red blood cells, confirmed by the increased axial ratios, and aggregated platelets with spreading. ConclusionThese findings may offer insights into the species-specific effects of snake venom on human blood and add value to the clinical workup in confirming envenomation. Further research is needed to correlate the 20 minute whole blood clotting test with measurable values from the thromboelastography within the context of snake envenomation. This may offer a bridge between cost, early diagnosis, and treatment of snake envenomation in resource-constrained countries.

Physicochemical and immunological effects of adjuvant formulations with snake venom antigens for immunization of horses for antivenom production

Enhancement of antivenom immune responses in horses through adjuvant technology improves antivenom production efficiency, but substantial local reactogenicity associated with some traditional veterinary adjuvants limits their usability. To explore modern adjuvant systems suitable for generating antivenom responses in horses, we first assessed their physicochemical compatibility with Bothrops asper snake venom. Liposome and nanoparticle aluminum adjuvants exhibited changes in particle size and phospholipid content after mixing with venom, whereas squalene emulsion-based adjuvants remained stable. Next, we evaluated serum antibody response magnitude and neutralization capacity in horses immunized with adjuvant-containing Echis ocellatus, Bitis arietans, Naja nigricollis, and Dendroaspis polylepis venom preparations. Whereas all tested adjuvants elicited significant neutralization capacity against the viperid venoms, the greatest antibody responses were generated by a squalene-in-water emulsion, thus representing a promising novel alternative for antivenom production.

Inhibition of phospholipase A2 from Naja haje and Naja nigricollis venoms by active fraction of Moringa oleifera leaves: in vitro and in silico methods

Phospholipases are one of the principal toxic enzymes in snake venoms inducing a wide variety of pharmacological effects after envenomation. Natural inhibitors from plants are known to inhibit the toxic enzyme activities of snake venoms. In this study, ethanol crude extract of M. oleifera leaves was partitioned using n-hexane and ethyl acetate after which fractionation was done using column and thin layer chromatography. Subsequently, the inhibitory activities of the crude extract and sub-fractions of M. oleifera were investigated against phospholipases A2 isolated from Naja haje and Naja nigricollis venoms using in vitro and in-silico approaches while EchiTab-PLUS polyvalent antivenom was used as the standard drug. The molecular weight of isolated N. haje phospholipase A2 (NH-PL) and N. nigricollis phospholipase A2 (NN-PL) were 24.11 and 35.22 kDa respectively. NH-PL enzyme had a specific activity of 2.70 μM/min/mg substrate while NN-PL activity was 2.10 μM/min/mg substrate. The Km of NH-PL was 0.330 μM with Vmax of 0.085 μM/mL min while NN-PL had Vmax of 0.198 μM/mL.min and Km of 0.670 μM. M. oleifera n-hexane sub-fraction 5 (MOLH5) exhibited a total inhibition of NN-PL and NH-PL enzyme activities at all concentrations used. Molecular docking of the phytoconstituents of MOLH5 against the catalytic site of phospholipase A2 revealed 2-Hydrazino-8-hydroxy-4-phenylquinoline as the lead compound and a potential drug candidate with a docking score of −6.789 kcal/mol. Findings indicated that MOLH5 possesses phospholipase A2 natural inhibitors that could be explored as a therapy for snake envenoming.

Anti-Snake Venom Activity of Indigofera Hirsuta Extracts Against Naja Nigricollis Venom

&#x0D; Indogofera hirsuta has reportedly been used in traditional medicine to treat snake envenomation. The study is aimed at exploring the potential of the plant for antivenom activity using standard methods. Preliminary phytochemical screening on the extracts revealed the presence of secondary metabolites such as alkaloids, flavonoids, tannins, steroids/terpenes, cardiac glycosides and saponins. Acute toxicity studies conducted on mice (ip) for different extract (Methanol, Butanol and Chloroform) using Lorkes method gave an LD50 of 1131.3mg/kg each, suggesting the plant to be less toxic. The antivenin effect of the extracts was tested against Naja nigricollis venom using mice. Maximum protection was observed in ex vivo model at an administered dose of (LD99 +260) with 100% survival for all mice used the extracts and a moderate survival rate (50%) at a dose of (LD99 + 80). Appreciable protection was observed in-vivo model at an administered dose of (LD99 + 500) with 83.3% survival for methanolic extract, moderate survival rate (50%) at a dose of (LD99 + 250) and relatively lower survival rate (33.3%) at a dose of (LD99 + 125) for all mice used the extracts. The results confirmed that extracts of Indigofera hirsuta contains bioactive constituents with significant antivenin activity (P&lt;0.05) under both ex vivo and in vivo conditions and thus providing scientific evidence to support the traditional claims for use in the treatment of snake bite.

Screening of Mucuna pruriens (L.) DC. and Pongamia pinnata (L.) Pierre (Fabaceae) Minerals on Biochemical Parameters of Oryctolagus cuniculus as Antivenom

Aims: The objective of this study was to evaluate the antivenom action of minerals from two plants on the biochemical parameters of rabbits.&#x0D; Methodology: For its realization, thirty-six (36) rabbits including nineteen (19) males and seventeen (17) females were divided into three portions (E1, E2 and E3). In each portion, there are different batches with three rabbits per batch. So, for E1, each rabbit of the control lot and those of the experimental lot were collected separately in the red tubes (dry tubes). However, those from the experimental batch were injected 20-30 minutes after the injection of Naja nigricollis venom. For E2, each rabbit in a given experimental batch was first scarified with a specific potion initially prepared and then separately harvested the following day. Then, each animal was separately envenomed and then separately sampled. In E3, the same procedure of E2 was observed with the only difference that this time, each animal of a given experimental lot was first separately envenomed and then scarified with a precise potion previously prepared and subsequently collected three days later. All the blood samples taken in the various red tubes were transported in a cooler for the determination of biochemical parameters.&#x0D; Results: The venom has a dose-dependent action on the red blood cells in vitro, whereas the in vivo tests highlighted in a general way, the stabilizing and preventive action of the minerals from the potion P2 (Mucuna pruriens), P3 (Pongamia pinnata), P4, P5 and P6, and the curative action of P1 and P3 (Pongamia pinnata) on some biochemical parameters. Indeed, their action was manifested by the survival of some envenomed animals with a greater activity for P3.&#x0D; Conclusion: For the development of an antivenom, it would be advisable to use more Pongamia pinnata because of its effectiveness both preventively and curatively.

INHIBITORY ACTIVITY OF LUPEOL FROM Cryptolepis oblongifolia (MEINS) SCHLTR ON PARTIALLY PURIFIED PHOSPHOLIAPASE A2 VENOM OF Naja nigricollis (ELAPIDAE)

The research is design to provide scientific evidence for the use of Cryptolepis oblongifolia in traditional treatment of inflammation and also to examine whether it have some snake venom phospholipase A2 inhibition potential. A triterpene was isolated from C. oblongifolia using column chromatography and identified via spectroscopic means. The inhibitory activity of the isolate on phospholipase A2 (PLA2) of Naja nigricollis venom was evaluated. The proton nuclear magnetic resonance (1H NMR) of the isolated compound showed the presence of olefinic protons while the carbon nuclear magnetic resonance (13C NMR) showed the presence of exomethylene carbon atoms. By comparison with the reported literature the compound was found to be lupeol, the inhibitory activity of the isolate on PLA2 of Naja nigricollis venom showed that, the isolate inhibits the PLA2 at dose dependent manner with inhibition binding constant (ki) of 0.015 mg/ml. The activity of the compound isolated supports the local usage of C. oblongifolia in traditional treatment of inflammation.

In-vitro and In-vivo Neutralization Activity of Methanol Extract of Adansonia digitata Fruit Pulp against Naja nigricollis Venom

Background: Adansonia digitata has been used as a traditional medicine to treat various diseases including snakebite envenomation. Objective: In this study, the protective and ameliorative potentials of crude methanol extract of Adansonia digitata fruit pulp against crude venom of Naja nigricollis in-vitro and in-vivo were investigated. Method: The dose-dependent inhibitory studies, pharmacological, histopathological and in vivo studies were conducted using standard methods. Result: The mean lethal dose of the crude methanolic extract of Adansonia digitata fruit pulp in Wistar rats was &gt; 5,000 mg/kg, while Naja nigricollis venom was 0.89 mg/kg. The anti-lethality effective concentration of the fruit pulp on Naja nigricollis venom was 92.52 mg/ml. Treatment significantly (&lt; 0.05) inhibited the activities of Naja nigricollis phospholipase A2 and dose-dependently reduced Naja nigricollis venom-induced paw oedema at 1-4 hours post-envenomation. In-vivo, treatment with 250 and 500 mg/kg of Adansonia digitata fruit pulp was protective against the clinical signs and mortality. Serum acetylcholinesterase activities were maintained in the group treated with normal saline and the ameliorative groups but decreased significantly (p &lt; 0.05) in other groups. Brain acetylcholinesterase was high in all the groups by day 1 but was reduced with increasing dose by day 2 in the ameliorative groups only. Adansonia digitata fruit pulp also preserved the histoarchitecture of the brain, heart, liver and spleen from venom-induced pathologies. Conclusion: Crude methanolic extract of Adansonia digitata fruit pulp possesses good protective and ameliorative neutralization effects on Naja nigricollis venom and could be promising in the management of snakebite envenomation.

Proteomics and histological assessment of an organotypic model of human skin following exposure to Naja nigricollis venom

Snakebite envenoming was reintroduced as a Category A Neglected Tropical Disease by the World Health Organization in 2017. Since then, increased attention has been directed towards this affliction and towards the development of a deeper understanding of how snake venoms exert their toxic effects and how antivenoms can counter them. However, most of our in vivo generated knowledge stems from the use of animal models which do not always accurately reflect how the pathogenic effects of snake venoms manifest in humans. Moreover, animal experiments are associated with pain, distress, and eventually animal sacrifice due to the toxic nature of snake venoms. Related to this, the implementation of the 3Rs principle (Replacement, Reduction, and Refinement) in the use of experimental animals in snakebite envenoming research is recommended by the World Health Organization. Therefore, more humane experimental designs and new in vitro/ex vivo alternatives for experimental animals are sought after. Here, we report the use of an organotypic model of human skin to further elucidate the pathophysiology of the dermonecrotic effects caused by the venom of the black-necked spitting cobra, Naja nigricollis, in humans. The goal of this study is to expand the repertoire of available models that can be used to study the local tissue damages induced by cytotoxic venoms.

A bioactive chalcone from the aerial parts of Indigofera conferta Gillet

Ethnobotanical information indicates that Indigofera conferta is used in northern Nigeria for the management of poisonous snakebites and the methanol extract was previously reported to have antivenin activity. In this study, we report the isolation of an oxyprenylated bioactive secondary metabolite; 2',4'- dihydroxy-4-prenyloxychalcone from the chloroform fraction of the aerial parts of the plant’s methanol extract and the in vivo evaluation of the compound against Naja nigricollis venom. The compound has demonstrated significant (p < 0.05) and dose-dependent antivenin activity against LD99 Naja nigricollis venom. At a dose of 10 mg/kg, the compound protected 60% of the animals tested from death. The observed activity lends credence to the traditional use of the plant in the management of snake bites in northern Nigeria. The compound, 2',4'- dihydroxy-4-prenyloxychalcone, could also serve as a lead in the development of novel antisnake venom agents.

Virus-like particles displaying conserved toxin epitopes stimulate polyspecific, murine antibody responses capable of snake venom recognition

Antivenom is currently the first-choice treatment for snakebite envenoming. However, only a low proportion of antivenom immunoglobulins are specific to venom toxins, resulting in poor dose efficacy and potency. We sought to investigate whether linear venom epitopes displayed on virus like particles can stimulate an antibody response capable of recognising venom toxins from diverse medically important species. Bioinformatically-designed epitopes, corresponding to predicted conserved regions of group I phospholipase A2 and three finger toxins, were engineered for display on the surface of hepatitis B core antigen virus like particles and used to immunise female CD1 mice over a 14 weeks. Antibody responses to all venom epitope virus like particles were detectable by ELISA by the end of the immunisation period, although total antibody and epitope specific antibody titres were variable against the different epitope immunogens. Immunoblots using pooled sera demonstrated recognition of various venom components in a diverse panel of six elapid venoms, representing three continents and four genera. Insufficient antibody yields precluded a thorough assessment of the neutralising ability of the generated antibodies, however we were able to test polyclonal anti-PLA2 IgG from three animals against the PLA2 activity of Naja nigricollis venom, all of which showed no neutralising ability. This study demonstrates proof-of-principle that virus like particles engineered to display conserved toxin linear epitopes can elicit specific antibody responses in mice which are able to recognise a geographically broad range of elapid venoms.

Characterization and Evaluation of the Effects of Indigofera pulchra, Aristolochia albida and Andrographis paniculata Leaves Extract Phenolics against the Activity of Naja nigricollis and Echis ocellatus Snake Venoms

With the increased incidence of snake envenomation, high cost of venom antiserum; its adverse side effects and lack of storage facilities for antiserum especially in rural areas, the use of plants as alternatives for treatment of poisonous snakebites is important, especially in remote areas. This research was aimed at characterization and evaluation of the effects of Indigofera pulchra, Aristolochia albida and Andrographis paniculata leaves extract phenolics against the activity of Naja nigricollis and Echis ocellatus snake venoms. The plants samples were extracted using chloroform, after which a qualitative and quantitative phytochemical analysis was done, followed by characterization analyses (GC-MS and FTIR). Preperatory and analytical tin layer chromatography analyses was carried out on all the extracts, flavonoids and tannins fractions were isolated, using garlic and tannic acids as standards. In-vitro inhibition analyses of the partially purified phenolics was done to ascertain the effects to the isolated phenolic fractions against the two selected crude snake venoms. The plant extracts characterization done revealed that all the three extracts contain phenolics and specifically important compounds like, Benzaldehyde-2-hydro-4-methoxy, rutin and gallocatechin, all which has been reported to have anti-snake venom capability. The inhibition studies carried out revealed that the flavonoid fractions of the extracts has a higher inhibitory effect against the snake venoms than the tannin fractions of all the extracts. Characterization and evaluation studies, done in this research has revealed that these plants’ phenolic fractions have effects on the two snake venoms and can help in the management and treatment of snake bite.

Naja nigricollis venom altered reproductive and neurological functions via modulation of pro-inflammatory cytokines and oxidative damage in male rats

Reproductive and neurological anomalies are often characterized by malfunctioning of reproductive and nervous organs sometimes attributed to systemic toxins. However, limited information is available on the impact of snake venom toxins on male reproductive and nervous system. This study investigated the toxicological effects of Naja nigricollis venom on male reproductive and neural functions in rat model. Twenty male Wistar rats weighing between 195 and 230 g were divided randomly into two groups of ten rats each. Group 1 served as normal control while rats in group 2 were envenomed with a single intraperitoneal injection of 0.25 mg/kg−1 (LD12.5) of N. nigricollis venom on first and twenty fifth day within the period of fifty days experiment. The venom significantly decreased sperm counts, motile cells and volume combined with increased sperm abnormalities. The venom induced hormonal imbalances in the envenomed group as levels of testosterone, luteinizing and follicle stimulating hormones depreciated compared to the control. Oxidative stress biomarkers: malondialdehyde significantly increased parallels with depletion of glutathione level and catalase activities in testis, epididymis and brain of envenomed rats. Furthermore, N. nigricollis venom up-regulated tumor necrosis factor-alpha (TNF-α) and interleukin1-beta (IL-1β) production in testis, epididymis and brain of envenomed rats compared to the control. Also, various histological alterations were noticed in tissues of testis, epididymis and brain of envenomed rats. Findings indicated that N. nigricollis venom is capable of inducing reproductive and neurological dysfunction in envenomed victims.

Black-necked spitting cobra (Naja nigricollis) phospholipases A2 may cause Trypanosoma brucei death by blocking endocytosis through the flagellar pocket

African trypanosomes, such as Trypanosoma brucei, are flagellated protozoa which proliferate in mammals and cause a variety of diseases in people and animals. In a mammalian host, the external face of the African trypanosome plasma membrane is covered by a densely packed coat formed of variant surface glycoprotein (VSG), which counteracts the host's adaptive immune response by antigenic variation. The VSG is attached to the external face of the plasma membrane by covalent attachment of the C-terminus to glycosylphosphatidylinositol. As the trypanosome grows, newly synthesised VSG is added to the plasma membrane by vesicle fusion to the flagellar pocket, the sole location of exo- and endocytosis. Snake venoms contain dozens of components, including proteases and phospholipases A2. Here, we investigated the effect of Naja nigricollis venom on T. brucei with the aim of describing the response of the trypanosome to hydrolytic attack on the VSG. We found no evidence for VSG hydrolysis, however, N. nigricollis venom caused: (i) an enlargement of the flagellar pocket, (ii) the Rab11 positive endosomal compartments to adopt an abnormal dispersed localisation, and (iii) cell cycle arrest prior to cytokinesis. Our results indicate that a single protein family, the phospholipases A2 present in N. nigricollis venom, may be necessary and sufficient for the effects. This study provides new molecular insight into T. brucei biology and possibly describes mechanisms that could be exploited for T. brucei targeting.

Non-compartmental toxicokinetic studies of the Nigerian Naja nigricollis venom.

Snakebite envenoming (SBE) is a neglected public health problem, especially in Asia, Latin America and Africa. There is inadequate knowledge of venom toxicokinetics especially from African snakes. To mimic a likely scenario of a snakebite envenoming, we used an enzyme-linked immunosorbent assay (ELISA) approach to study the toxicokinetic parameters in rabbits, following a single intramuscular (IM) administration of Northern Nigeria Naja nigricollis venom. We used a developed and validated non-compartmental approach in the R package PK to determine the toxicokinetic parameters of the venom and subsequently used pharmacometrics modelling to predict the movement of the toxin within biological systems. We found that N. nigricollis venom contained sixteen venom protein families following a mass spectrometric analysis of the whole venom. Most of these proteins belong to the three-finger toxins family (3FTx) and venom phospholipase A2 (PLA2) with molecular weight ranging from 3 to 16 kDa. Other venom protein families were in small proportions with higher molecular weights. The N. nigricollis venom was rapidly absorbed at 0.5 h, increased after 1 h and continued to decrease until the 16th hour (Tmax), where maximum concentration (Cmax) was observed. This was followed by a decrease in concentration at the 32nd hour. The venom of N. nigricollis was found to have high volume of distribution (1250 ± 245 mL) and low clearance (29.0 ± 2.5 mL/h) with an elimination half-life of 29 h. The area under the curve (AUC) showed that the venom remaining in the plasma over 32 h was 0.0392 ± 0.0025 mg h.L−1, and the mean residence time was 43.17 ± 8.04 h. The pharmacometrics simulation suggests that the venom toxins were instantly and rapidly absorbed into the extravascular compartment and slowly moved into the central compartment. Our study demonstrates that Nigerian N. nigricollis venom contains low molecular weight toxins that are well absorbed into the blood and deep tissues. The venom could be detected in rabbit blood 48 h after intramuscular envenoming.

Preclinical efficacy evaluation of two commercially available anti-snake venom against naja nigricollis induced envenomation

Background: The biochemical and immunological variations of snake venom components lead to many challenges in manufacturing appropriate anti snake venom (ASV). These variations have negatively impacted clinical outcomes due to the availability of ineffffective ASVs in countries where the manufacturing venom does not originate. There are reports of ineffffective ASVs exported to some African countries with public health and economic consequences on the already debilitating crisis. Recently, there have been calls and publications to draw the attention of policymakers and regional regulators on the need for preclinical and clinical data related to ASV, especially when manufactured from other regions. We therefore, screened the two most commercially available antisnake venom in Northern Nigeria against the most medically important cobra venom (N. nigricollis). Methods: N. nigricollis venom was manually milked from fifive N. nigricollis captured from the wild and the LD50 of venom was determined using probit analysis. The effiffifficacy evaluation was conducted using the classical world health organization's preclinical mixing of venom/ASV methods on the lethal, hemorrhagic, hemolytic and necrotic effffect of the venom in mice and rabbit blood. Result: The median lethal dose (LD50) of Naja nigricollis venom was estimated to be 1.0 mg/kg as calculated using Probit analysis. The two ASVs used for this study; EchiTab Plus-ICP and Premium Antivenom (PAV), provided protection (100%) against venom-induced lethality in mice except at the dose of 100l/mouse, where the PAV provided only 33% protection. All the administered doses of both EchiTab-Plus-ICP and PAV showed statistically signifificant reduction (p&lt;0.001) in the mean hemorrhagic diameter when compared with the control group (19.12±1.95 mm). There was also signifificant reduction (p&lt;0.001) in the mean necrotic diameter in all the groups compared to the control group (8.58±1.33 ml). Two dilutions of EchiTab-Plus-ICP (100 and 200 l) were able to signifificantly reduce (&gt;50%) venom-induced hemolysis by 58 and 62% respectively, compared with the venom control group. On the other hand, such reduction was not observed with PAV. Conclusion: The two most commercially available ASV in Northern Nigeria, EchiTab Plus-ICP and Premium Antivenom, were signifificantly (P &gt; 0.01) effffective against lethality and venom-induced pathological parameters from Naja nigricollis envenoming, including; hemolysis, hemorrhagic and necrotic lesions, with EchiTab Plus-ICPshowing better activity.