Publication

Abstract : Snakebite envenomation remains a major public health challenge in India, where most fatalities are caused by the “Big Four” snakes and polyvalent antivenom (PAV) is produced only against their venoms. However, several regionally important species, including Trimeresurus erythrurus (red-tailed pit viper), are medically relevant in Northeast India but remain poorly studied. This study evaluated the cross-reactivity and neutralisation efficiency of Indian commercial PAVs against T. erythrurus venom (TEV). Immunological assays, including ELISA, spectrofluorometry, and Western blotting, demonstrated poor recognition of TEV by PAV, with weak binding affinity and reduced antibody titres compared to Echis carinatus venom (ECV). Sequence analysis of snake venom metalloproteinases revealed moderate similarity (30–75%) between TEV and ECV, explaining the limited cross-reactivity and suboptimal neutralisation. The neutralisation potency of PAV against TEV was low (∼0.25 mg/mL), and EC50 and Kd values further confirmed weak antigen–antibody interactions. In vivo studies using a mouse model showed that PAV treatment partially restored altered haematological and biochemical parameters but failed to prevent venom-induced tissue damage in vital organs. In rescue-type experiments, post-envenomation administration of PAV conferred protection only at a high TEV-to-PAV ratio (1:400). A comparative analysis with Trimeresurus popeiorum venom revealed similar in vitro antivenom binding but poorer in vivo neutralisation of TEV, highlighting TEV's greater lethality. Overall, this study demonstrates the limited paraspecific neutralisation efficacy of Indian PAV against TEV and underscores the urgent need for region-specific, species-targeted antivenoms to improve clinical outcomes of pit viper envenomation in Northeast India.