Immunological Cross-Reactivity and Neutralizing Efficacy of Antivenom Against Five Medically Important Iranian Viper...

Antivenom efficacy relies on the venom antigen composition and the range of antibody cross-reactivity. This research compared the biochemical profiles of five medically relevant Iranian vipers, Gloydius caucasicus, Pseudocerastes persicus, Montivipera raddei, Echis carinatus, and Macrovipera lebetina, and compared the cross-reactivity and neutralisation efficacy of laboratory-prepared monovalent.

Venom was characterised using SDS-PAGE and reverse-phase HPLC (RP-HPLC). Monovalent antisera were raised in rabbits against each species, and a separate group was immunised with a mixture of all five venoms to produce a polyvalent antivenom. Indirect ELISA quantified homologous and heterologous binding, and in vivo assays assessed neutralisation efficacy against both homologous and heterologous venoms.

Among the five viper species studied, G. caucasicus venom was the most toxic and that of P. persicus the least. Under non-reducing SDS-PAGE, all venoms displayed three main protein bands of approximately 20 kDa, 50 kDa and 130-150 kDa with variable intensities. Following reduction, an intense ∼15 kDa band appeared in all the samples. RP-HPLC revealed nearly identical, simple chromatograms for E. carinatus and M. raddei, a more diverse profile for M. lebetina, moderate complexity for G. caucasicus, and a distinct hydrophilic peak for P. persicus. Monovalent antivenoms showed strongest binding to homologous venoms but variable heterologous cross-reactivity, with M. raddei and P. persicus exhibiting the broadest spectra and G. caucasicus the narrowest, while the polyvalent antivenom bound broadly across all species. The antivenoms against M. lebetina and M. raddei neutralised P. persicus venom at 1.17 mg/mL and 1.07 mg/mL, respectively, while P. persicus antivenom neutralised M. raddei (0.49 mg/mL) and E. carinatus (0.66 mg/mL). G. caucasicus antivenom was only effective against its homologous venom.

This study demonstrated general patterns among Iranian viper venoms, but variable LD₅₀ values and protein compositions determine the efficiency of antivenom. Efficient neutralisation was indicated by the polyspecific antivenom in all venoms, outlining its efficacy and viability as a local antivenom control method.