Preclinical assessment of VPEAV, a new trivalent antivenom for elapid snakebite envenoming in the Philippines: Proteomics, immunoreactivity and toxicity neutralization

Snakebite envenoming is an important neglected tropical disease. Antivenom supply, however, remains limited in many parts of the world. This study aimed to examine the protein composition, immunoreactivity and neutralization efficacy of a new antivenom product (VINS Philippine Elapid Antivenoms, VPEAV) developed for the treatment of snakebite envenoming caused by the Philippine Cobra (Naja philippinensis), Samar Cobra (Naja samarensis) and King Cobra (Ophiophagus hannah). Size-exclusion chromatography, sodium-dodecyl sulfate-polyacrylamide gel electrophoresis and tandem mass spectrometry showed that VPEAV consisted of F(ab)'2 (∼90% of total antivenom proteins) with minimal protein impurities. Indirect ELISA showed varying immunoreactivity of VPEAV toward the different venoms (EC50 = 4-16 μg/ml), indicating distinct venom antigenicity between the species. In mice, the neutralization potency of VPEAV against the King Cobra venom was moderate (potency, P = 2.6 mg/ml, defined as the amount of venom completely neutralized per unit volume of antivenom). The potency was significantly lower against the N. philippinensis and N. samarensis venoms (P = 0.18-0.30 mg/ml), implying a higher dose may be needed for effective neutralization of the Naja venoms. Together, the findings suggest the potential and limitation of VPEAV in neutralizing the venom toxicity of the three Philippine elapid snakes.