The commercial polyvalent antivenom against the "Big Four" venomous snakes of India shows poor immune recognition and neutralization of lethality and toxicity of Trimeresurus popeiorum venom proteins in the mouse model

Abstract

In tropical areas, especially India, where the "Big Four" snakes cause most snakebite cases, envenomation is still a significant public health issue. Trimeresurus popeiorum (Pope's pit viper), a species prevalent in Northeast India, remains neglected despite its medical importance. This study examines the immunological cross-reactivity and efficacy of Indian commercial polyvalent antivenoms (PAVs) in neutralizing T. popeiorum venom (TPV). Commercial PAVs had inadequate recognition and neutralization of TPV enzymes such as metalloprotease, serine protease, and phospholipase A₂. The venom-antivenom interaction by spectrofluorometry analysis showed that commercial PAVs include low TPV-specific antibodies, and they failed to mitigate TPV's procoagulant and indirect hemolytic effects. Mice treated with 3LD₅₀ value of TPV pre-incubated with PAV (1:200, protein: protein) survived but had a higher ED₅₀ value (0.51 mg of venom per mL of PAV) and lower PAV potency (0.34 mg of venom neutralized per mL of PAV) than the "Big Four" snakes, indicating reduced effectiveness of current PAVs against TPV. The Indian PAV partially alleviated TPV-induced bleeding and vascular congestion in treated mice's hearts, livers, kidneys, lungs, and testes. This study highlights the limited effectiveness of Indian PAVs against TPV. To improve treatment outcomes for neglected snake envenomations, species-specific antivenom is needed.

Keywords: Big four snakes; Histopathology; Immuno cross-reactivity; Neutralization; Species-specific antivenom.