Quantitative proteomic analysis of venom from Southern India common krait (Bungarus caeruleus) and identification of poorly immunogenic toxins by immune-profiling against commercial antivenom

Objectives: To study the venom proteome composition of Southern India (SI) Common Krait (Bungarus caeruleus) and immunological cross-reactivity between venom against commercial antivenom.

Methods: Proteomic analysis was done by nano LC-MS/MS and toxins were quantitated by label-free analysis. The immunological cross-reactivity of venom towards polyvalent antivenom (PAV) was assessed by ELISA, Immunoblotting, and immuno-chromatographic methods.

Results: A total of 57 enzymatic and non-enzymatic proteins belonging to 12 snake venom protein families were identified. The three finger toxins (3FTx) (48.3%) and phospholipase A₂ (PLA₂) (37.6%) represented the most abundant non-enzymatic and enzymatic proteins, respectively. β-bungarotoxin (12.9%), a presynaptic neurotoxin, was also identified. The venom proteome composition is well correlated with its enzymatic activities, reported pharmacological properties, and clinical manifestations of krait envenomation. Immuno-cross-reactivity studies demonstrated better recognition of high molecular weight proteins (>45 kDa) of this venom by PAVs compared to low molecular weight (<15 kDa) toxins such as PLA₂ and 3FTxs.

Conclusion: The poor recognition of <15 kDa mass SI B. caeruleus venom proteins is of grave concern for the successful treatment of krait envenomation. Therefore, emphasis should be given to improve the immunization protocols and/or supplement of antibodies raised specifically against the <15 kDa toxins of this venom.