Enzymatic activity and brine shrimp lethality of venom from the large brown spitting cobra (Naja ashei) and its neutralization by antivenom

Development, Optimization and Evaluation of a Sensitive Enzyme-Linked Immunosorbent Assay (ELISA) Prototype for Detection of Chicken-Based IgY Polyclonal Antibodies against Toxins of D. polylepis Venom

Life-threatening medical issues can result from snakebite, and hence this is a public health concern. In many tropical and subtropical nations such as Kenya, where a wide variety of poisonous snakes are prevalent, diagnosis of snakebite in health facilities is imperative. Different antivenoms are needed to treat the venom of different snake species. Nonetheless, it might be difficult for medical professionals to identify the exact snake species that envenomated a patient due to the similarities of several snake envenomations' clinical symptoms. Therefore, the necessity for an assay or technique for identifying venomous species is critical. The current study sought to develop a sensitive ELISA prototype for the detection of D. polylepis venom in Kenya using generated chicken-based IgY polyclonal antibodies. Serum samples containing specific chicken-based IgY antibodies previously raised against D. polylepis venom toxins were used in the assay development. ELISA parameters were optimized, and the developed assay was assessed for applicability. The limit of detection (LoD) of the ELISA for neurotoxic venoms was determined to be 0.01 µg/mL. Successful discrimination between neurotoxic and cytotoxic venoms was achieved by the ensuing inhibition ELISA assay. The developed assay showed the capability of identifying venoms in blood samples (from spiked and venom-challenged blood samples) of BALB/c mice, providing compelling evidence of the strategy's usefulness. This assay could help physicians diagnose and manage victims of snakebites through the evaluation of clinical samples.

Assessment of the Artemia salina toxicity assay as a substitute of the mouse lethality assay in the determination of venom-induced toxicity and preclinical efficacy of antivenom

Mice are routinely used in snake venom research but are costly and subject to pain and suffering. The crustacean Artemia salina could be an alternative to mice, but data to support its adoption in snake venom research is limited. The aim of the present study was to evaluate the suitability of A. salina as a surrogate of mice in assessing the toxicity of venoms and the preclinical efficacy of antivenoms. The toxicity of venoms from 22 snakes of medical importance in sub-Saharan Africa was evaluated in mice (intraperitoneally; i.p. and intravenously; i.v.) and in A. salina. Subsequently, the capacity of a commercial antivenom to neutralize the toxicity of these venoms in mice and A. salina was investigated. There was a positive correlation between the i.v. median lethal doses (LD50s) and the i.p. LD50s in mice (r = 0.804; p < 0.0001), a moderate correlation between the i.v. LD50s in mice and the median lethal concentrations (LC50s) in A. salina (r = 0.606; p = 0.003), and a moderate correlation between the i.p. LD50s in mice and the LC50s in A. salina (r = 0.426; p = 0.048). Moreover, there was a strong correlation between the i.p. median effective doses (ED50s) and the i.v. ED50s in mice (r = 0.941, p < 0.0001), between the i.p. ED50s in mice and the ED50s in A. salina (r = 0.818, p < 0.0001), and between the i.v. ED50s in mice and the ED50s in A. salina (r = 0.972, p < 0.0001). These findings present A. salina as a promising candidate for reducing reliance on mice in snake venom research. Future investigations should build upon these findings, addressing potential limitations and expanding the scope of A. salina in venom research and antivenom development.

Exploring nature's antidote: unveiling the inhibitory potential of selected medicinal plants from Kisumu, Kenya against venom from some snakes of medical significance in sub-Saharan Africa

Background: The present study investigated the efficacy of Conyza bonariensis, Commiphora africana, Senna obtusifolia, Warburgia ugandensis, Vernonia glabra, and Zanthoxylum usambarense against Bitis arietans venom (BAV), Naja ashei venom (NAV), and Naja subfulva venom (NSV). Methods: 40 extracts and fractions were prepared using n-hexane, dichloromethane, ethyl acetate, and methanol. In vitro efficacy against snake venom phospholipase A2 (svPLA2) was determined in 96-well microtiter and agarose-egg yolk coagulation assays. in vivo efficacy against venom-induced cytotoxicity was determined using Artemia salina. Two commercial antivenoms were used for comparison. Results: The 96-well microtiter assay revealed poor svPLA2 inhibition of BAV by antivenom (range: 20.76% ± 13.29% to 51.29% ± 3.26%) but strong inhibition (>90%) by dichloromethane and hexane fractions of C. africana, hexane and ethyl acetate extracts and fraction of W. ugandensis, dichloromethane fraction of V. glabra, and the methanol extract of S. obtusifolia. The methanol extract and fraction of C. africana, and the hexane extract of Z. usambarense strongly inhibited (>90%) svPLA2 activity in NAV. The hexane and ethyl acetate fractions of V. glabra and the dichloromethane, ethyl acetate, and methanol extracts of C. africana strongly inhibited (>90%) svPLA2 in NSV. The agarose egg yolk coagulation assay showed significant inhibition of BAV by the dichloromethane fraction of C. africana (EC50 = 3.51 ± 2.58 μg/mL), significant inhibition of NAV by the methanol fraction of C. africana (EC50 = 7.35 ± 1.800 μg/mL), and significant inhibition of NSV by the hexane extract of V. glabra (EC50 = 7.94 ± 1.50 μg/mL). All antivenoms were non-cytotoxic in A. salina but the methanol extract of C. africana and the hexane extracts of V. glabra and Z. usambarense were cytotoxic. The dichloromethane fraction of C. africana significantly neutralized BAV-induced cytotoxicity, the methanol fraction and extract of C. africana neutralized NAV-induced cytotoxicity, while the ethyl acetate extract of V. glabra significantly neutralized NSV-induced cytotoxicity. Glycosides, flavonoids, phenolics, and tannins were identified in the non-cytotoxic extracts/fractions. Conclusion: These findings validate the local use of C. africana and V. glabra in snakebite but not C. bonariensis, S. obtusifolia, W. ugandensis, and Z. usambarense. Further work is needed to isolate pure compounds from the effective plants and identify their mechanisms of action.

Progress and promise of alternative animal and non-animal methods in biomedical research

Cell culture and invertebrate animal models reflect a significant evolution in scientific research by providing reliable evidence on the physiopathology of diseases, screening for new drugs, and toxicological tests while reducing the need for mammals. In this review, we discuss the progress and promise of alternative animal and non-animal methods in biomedical research, with a special focus on drug toxicity.

Evaluation of lethality and cytotoxic effects induced by Naja ashei (large brown spitting cobra) venom and the envenomation-neutralizing efficacy of selected commercial antivenoms in Kenya

Neutralization of lethality in mice model at the preclinical level has been established by the World Health Organization as the gold standard for the evaluation of antivenom efficacy. The assessment of the neutralization profiles of antivenoms helps to discern the efficacy or otherwise of these antivenoms at neutralizing the toxic effects induced by medically significant snake venoms. However, for many antivenoms, information on their preclinical efficacy remains limited. Therefore, to strengthen global efforts at reducing the impact of snakebite envenoming, the provision of information on the preclinical efficacy of antivenoms, especially in parts of the world where antivenom availability and accessibility is problematic, including sub-Saharan Africa is crucial. This study presents the lethal and toxic activities of N. ashei venom and the neutralizing capacity of two commonly used commercial antivenoms in Kenya; VINS™ and Inoserp™. Median lethal dose (LD50), minimum necrotizing dose (MND) and minimum edema-forming dose (MED) of N. ashei venom as well as the neutralization of these effects were evaluated in mice. The LD50 of N. ashei venom was found to be 4.67 (3.34-6.54) mg/kg while MND and MED were 11.00 μg and 0.80 μg respectively. Both VINS™ and Inoserp™ antivenoms demonstrated capacity to neutralize the lethal and toxic effects induced by Naja ashei venom albeit at varying efficacies. Our results thus confirm the toxic effects of N. ashei venom as previously observed with other Naja sp. venoms and also underscore the relevance of para-specific neutralizing capacity of antivenoms in the design of antivenoms.

Development and Characterization of Anti-Naja ashei Three-Finger Toxins (3FTxs)-Specific Monoclonal Antibodies and Evaluation of Their In Vitro Inhibition Activity

Antivenom immunotherapy is the mainstay of treatment for snakebite envenoming. Most parts of the world affected by snakebite envenoming depend on broad-spectrum polyspecific antivenoms that are known to contain a low content of case-specific efficacious immunoglobulins. Thus, advances in toxin-specific antibodies production hold much promise in future therapeutic strategies of snakebite envenoming. We report anti-3FTxs monoclonal antibodies developed against N. ashei venom in mice. All the three test mAbs (P4G6a, P6D9a, and P6D9b) were found to be IgG antibodies, isotyped as IgG1. SDS-PAGE analysis of the test mAbs showed two major bands at approximately 55 and 29 kDa, suggestive of immunoglobulin heavy and light chain composition, respectively. The immunoaffinity-purified test mAbs demonstrated higher binding efficacy to the target antigen compared to negative control. Similarly, a cocktail of the test mAbs was found to induce a significantly higher inhibition (p-value < 0.0001) compared to two leading commercial brands of antivenoms on the Kenyan market, implying a higher specificity for the target antigen. Both the test mAbs and 3FTxs polyclonal antibodies induced comparable inhibition (p-value = 0.9029). The inhibition induced by the 3FTxs polyclonal antibodies was significantly different from the two antivenoms (p-value < 0.0001). Our results demonstrate the prospects of developing toxin-specific monoclonal-based antivenoms for snakebite immunotherapy.

Development of an Inhibition Enzyme-Linked Immunosorbent Assay (ELISA) Prototype for Detecting Cytotoxic Three-Finger Toxins (3FTxs) in African Spitting Cobra Venoms

The administration of toxin-specific therapy in snake envenoming is predicated on improved diagnostic techniques capable of detecting specific venom toxins. Various serological tests have been used in detecting snakebite envenoming. Comparatively, enzyme-linked immunosorbent assay (ELISA) has been shown to offer a wider practical application. We report an inhibition ELISA for detecting three-finger toxin (3FTx) proteins in venoms of African spitting cobras. The optimized assay detected 3FTxs in N. ashei (including other Naja sp.) venoms, spiked samples, and venom-challenged mice samples. In venoms of Naja sp., the assay showed inhibition, implying the detection of 3FTxs, but showed little or no inhibition in non-Naja sp. In mice-spiked samples, one-way ANOVA results showed that the observed inhibition was not statistically significant between spiked samples and negative control (p-value = 0.164). Similarly, the observed differences in inhibition between venom-challenged and negative control samples were not statistically significant (p-value = 0.9109). At an LOD of 0.01 µg/mL, the assay was able to confirm the presence of 3FTxs in the samples. Our results show a proof of concept for the use of an inhibition ELISA model as a tool for detecting 3FTxs in the venoms of African spitting cobra snakes.

Artemia salina as an animal model for the preliminary evaluation of snake venom-induced toxicity

Lethality and cytotoxicity assays of snake venoms and their neutralization by antivenom require many mice for the experiments. Recent developments have prompted researchers to seek alternative strategies that minimize the use of mice in line with Russel and Burch's 3Rs philosophy (Replacement, Reduction, and Refinement). Artemia salina is an animal model widely used for toxicity screening. However, its use in snake venom toxinology is limited by a lack of data. The present study compared the toxicity of venoms from Bitis arietans, Naja ashei, and Naja subfulva using mice and Artemia salina. In the Artemia salina test at 24 h and the dermonecrotic test in mice, the toxicity of the venoms was in the order Naja ashei ~ Naja subfulva > Bitis arietans. In the lethality test in mice, the toxicity of the venoms was in the order Naja subfulva > Naja ashei > Bitis arietans. These findings suggest that the toxicity of the venoms in Artemia salina and the dermonecrotic bioassay in mice have a similar trend but differ from the lethality test in mice. Therefore, it may be relevant to further explore the Artemia salina bioassay as a potential surrogate test of dermonecrosis in mice. Studies with more venoms may be needed to establish the correlation between the Artemia salina bioassay and the dermonecrotic assay in mice.

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Bitis arietans, Naja ashei, and Naja subfulva snake venom-induced toxicities were compared in Artemia salina and in mice.

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Venom-induced toxicity in Artemia salina has a similar trend to necrosis in mice but not lethality.

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The Artemia salina bioassay may be further explored along the 3Rs (Reduction, Replacement, and Refinement) concept.

Phytochemical Analysis and Investigation of the Antimicrobial and Cytotoxic Activities of Croton dichogamus Pax Crude Root Extracts

Background

Increasing antimicrobial resistance has led to an arduous search for new potent drugs from nature. In this search, plants have proved to be rich reservoirs of efficacious medicinal components that manage ailments. The current study is designed to investigate the phytochemical composition, antimicrobial activity, and the cytotoxicity of the crude root extracts of Croton dichogamus, a shrub that is commonly used in the eastern Africa for the management of infectious diseases.

Methods

The roots of Croton dichogamus were obtained, dried, ground, and extracted using three solvents (acetone, distilled water, and 50% ethanol). The antimicrobial activity was tested using agar well diffusion and microbroth dilution techniques against five human pathogens. The brine shrimp lethality assay was used to assess the toxic effect.

Results

The phytochemical screening indicated the presence of terpenoids, flavonoids, tannins, phenols, polyuronides, saponins, and anthracenes. The brine shrimp lethality assay indicated that all the extracts were highly cytotoxic with LC₅₀ values below 100 μg/ml. Acetonic extract had an LC₅₀ value of 4.148 μg/ml, hydroethanolic extract had 76.09 μg/ml, and aqueous extract had 42.61 μg/ml. All extracts showed the antibacterial activity against Gram-positive bacteria (B. cereus and S. aureus) and a fungal organism, C. albicans. The extracts showed no antibacterial effect on the Gram-negative bacterial strains (P. aeruginosa and E. coli) at a concentration of 250 mg/ml. The highest antimicrobial activity was demonstrated by the acetonic extract on B. cereus which had an MIC of 10.42 mg/ml and a zone of inhibition of 17.33 ± 0.58 at a concentration of 250 mg/ml.

Conclusion

In this research work, we report that C. dichogamus had the antimicrobial activity confirming the folklore claim. The results made a strong case for isolation of novel anticancer lead compounds.

Effects of 3FTx Protein Fraction from Naja ashei Venom on the Model and Native Membranes: Recognition and Implications for the Mechanisms of Toxicity

Three-finger toxins are naturally occurring proteins in Elapidae snake venoms. Nowadays, they are gaining popularity because of their therapeutic potential. On the other hand, these proteins may cause undesirable reactions inside the body's cells. A full assessment of the safety of Naja ashei venom components for human cell application is still unknown. The aim of the study was to determine the effect of the exogenous application of three-finger toxins on the cells of monocytes (U-937) and promyelocytes (HL-60), with particular emphasis on the modification of their membranes under the influence of various doses of 3FTx protein fraction (0-120 ng/mL). The fraction exhibiting the highest proportion of 3FTx proteins after size exclusion chromatography (SEC) separation was used in the experiments. The structural response of cell membranes was described on the basis of single-component and multi-component Langmuir monolayers that mimicked the native membranes. The results show that the mechanism of protein-lipid interactions depends on both the presence of lipid polar parts (especially zwitterionic type of lipids) and the degree of membrane saturation (the greatest-for unsaturated lipids). The biochemical indicators reflecting the tested cells (MDA, LDH, cell survival, induction of inflammation, LD50) proved the results that were obtained for the model.