An equine bivalent F(ab')2 antivenom developed against the venoms of two neglected pit viper species from Northeast India-Trimeresurus erythrurus and T. popeiorum-exhibits enhanced in vitro and preclinical neutralisation efficacy when compared to Indian commercial polyvalent antivenom.

In north-east India (NEI), Trimeresurus erythrurus and T. popeiorum cause numerous snakebite fatalities; however, Indian polyvalent antivenom (PAV) against the big four venomous snakes exhibits weak neutralising efficacy. To address this gap, a bivalent equine F(ab')2 antivenom (Bi-AV) for the first time was developed against the venoms of T. erythrurus and T. popeiorum from Mizoram, NEI. Bi-AV demonstrated markedly superior binding affinity towards both venoms, as indicated by significantly reduced EC50 and dissociation constant (Kd) values compared with PAV. Immunoblotting further revealed stronger immunorecognition of Trimeresurus venoms by Bi-AV, particularly low-molecular-mass venom toxins such as phospholipase A2 (PLA2). Moreover, Bi-AV exhibited more efficient neutralisation of key venom enzymatic activities, including snake venom metalloprotease, PLA2, L-amino acid oxidase, and fibrin(ogen)olytic activity, resulting in a significant reduction in venom-induced pharmacological effects and lethality in both in vitro and in vivo models. Subsequently, this resulted in improved survival and a significant reduction in venom-associated haematological, biochemical, and histopathological alterations in mice. In addition, Bi-AV also effectively neutralised T. popeiorum venom collected from Meghalaya, indicating appreciable cross-regional efficacy. Furthermore, Bi-AV conferred significant protection in rescue-type in vivo experiments that closely mimic real-world clinical envenomation scenarios.