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Snake envenomation results in a range of clinical sequelae, and widely used animal-based conventional antivenoms exhibit several limitations including the adverse immunological effects in human snake bite victims. Therefore, human monoclonal anti-snake venom antibodies or fragments can be an alternate therapy for overcoming the existing limitations. We developed venom-neutralizing humanized scFv antibodies and analyzed biochemical mechanisms associated with the inhibition of toxicity. Tomlinson I and J human scFv antibody libraries were screened against Naja naja and Echis carinatus venoms, and seven unique scFv antibodies were obtained. Further, specific toxins of snake venom interacting with each of these scFvs were identified, and phospholipase A2 (PLA2) was found to be prominently captured by the phage-anchored scFv antibodies. Our study indicated PLA2 to be one of the abundant toxins in Naja naja and Echis carinatus venom samples. The scFvs binding to PLA2 were used to perform in vivo survival assay using the mouse model and in vitro toxin inhibition assays. scFv N194, which binds to acidic PLA2, protected 50% of mice treated with Naja naja venom. Significant prolongation of survival time and 16% survival were observed in Echis carinatus venom-challenged mice treated with scFv E113 and scFv E10, respectively. However, a combination comprised of an equal amount of two scFvs, E113 and E10, both interacting with basic PLA2, exhibited synergistically enhanced survival of 33% in Echis carinatus venom-challenged mice. No such synergistically enhanced survival was observed in the case of combinatorial treatment with anti- Naja naja scFvs, N194, and N248. These scFvs demonstrated partial inhibition of venom-induced myotoxicity, and E113 also inhibited hemolysis by 50%, which corroborates the enhanced survival during combinatorial treatment in Echis carinatus venom-challenged mice. • Conventional antivenoms exhibit adverse effects in snakebite victims. • Seven human scFvs antibody fragments against two prominent Indian snake venoms were isolated. • Majority of antibodies were specific to phospholipase A2, which is an abundant toxin in both venoms. • These antibodies partially inhibited venom-induced myotoxicity, and one of them also exhibited partial hemolysis inhibition. • Antibodies developed against PLA2 exhibited partial in vivo venom neutralization. [ABSTRACT FROM AUTHOR]

African cobras (Naja species) represent one of the most encountered medically important snakes in Africa. They are classified as African spitting (Afronaja subgenus) and non-spitting cobras (Uraeus and Boulengerina subgenera) with similar and different characteristics. Snake venom toxins including three-finger toxin (3FTx), phospholipase A2 (PLA 2), and snake venom metalloproteinase (SVMP) cause snakebite envenomation leading to morbidity and mortality. The profile of the proteome of African cobra venoms will help to develop safer and more effective antivenoms. The approval of Captopril by the US Food and Drug Administration (FDA) for the treatment of cardiovascular diseases, has led to intensified research towards possible use of venom toxins as therapeutics. In this review, we compare the venom proteome profile of 3 African Naja subgenera. In both Afronaja and Boulengerina subgenera, 3FTx (Afronaja –69.79%; Boulengerina –60.56%) followed by PLA 2 (Afronaja –21.15%; Boulengerina –20.21%) dominated the venoms compared to the Uraeus subgenus dominated by 3FTx (84.55%) with little to no PLA 2 abundance (0.8%). The venom of subgenus Uraeus was distinct from the other two subgenera by the almost total absence of PLA 2 , thus indicating little or no contribution of PLA 2 in the envenomation caused by Uraeus compared to Afronaja and Boulengerina. Furthermore, we report studies on the experimental testing of African cobra venoms and toxins against diseases including anti-cancer properties. [Display omitted] • African spitting and non-spitting cobra venoms cause severe envenomation. • 3FTxs are the most dominant toxin of spitting and non-spitting cobras venoms. • African non-spiting cobra venom of the Uraeus genus constitutes little or no PLA 2. • African cobras have potential therapeutic applications against diseases including cancer. [ABSTRACT FROM AUTHOR]

Catuneragam nilotica has been used in ethnomedicine to treat snakebite, inflammation, and diarrhea among others. The aim of this research is to isolate, and characterize potential potential phospholipase A 2 (PLA 2) inhibitors from the roots of C. nilotica. The plant material was collected, authenticated, and sequentially extracted using solvents of increasing polarity starting from n-hexane, ethyl acetate, and methanol. The extracts as reported in our previous work, were screened in vitro for their inhibitory activity against PLA 2 enzyme from N. nigricollis venom using acidimetric assay. In line with the bio-activity guided isolation, methanol extract (being the most active) was subjected to chromatographic separation using silica gel and sephadex LH-20 which resulted in the isolation and characterization of scopoletin, and scopolin; the compounds were able to inhibit the hydrolytic actions of PLA2 enzyme with percentage inhibition ranging from 67.82 to 100.00 % and 65.76–93.15 %, respectively while the standard Antisnake Venom (ASV) had 74.96–85.04 % after 10 min incubation at 37 °C. The molecular docking of the compounds against PLA 2 enzyme was performed using Auto Dock Vina while ADME-Tox analysis was evaluated using swissADME and ProTox-II online servers; The findings indicated that both compounds were able to bind to the active site of PLA 2 enzyme with high affinity (−6.5 to −6.2 kcal/mol) and they exhibited favorable drug-likeness and pharmacokinetic properties, and according to toxicity predictions, scopolin was found to be non-toxic (LD 50 of 5000 mg/kg) while scopoletin has a slight chance of being toxic (LD 50 of 3800 mg/kg). In conclusion, the findings of the research revealed that the roots of C. nilotica contains phytoconstituents with anti-PLA 2 enzyme activity and thus, validates the ethnomedicinal claim of the use of the plant as herbal therapy against N. nigricollis envenomation. [Display omitted] • Scopoletin and Scopolin were identified from the roots of Catuneragam nilotica. • Both compounds were able to inhibit the hydrolytic actions of PLA 2 enzyme from Naja nigricollis venom. • The compounds interacted with key amino acid residues such as HIS47 and ASP48 at the active site of PLA 2 with high affinity. • Scopoletin and Scopolin also exhibited favorable drug-like and pharmacokinetics properties. • The roots of C. nilotica contain active phytoconstituents with proven antisnake properties. [ABSTRACT FROM AUTHOR]