Avidity based discrimination of venoms from two Egyptian Echis species.

Species-specific antibodies (Abs) to venoms from two species of the genus Echis were prepared by adsorption of monovalent and affinity purified anti-Echis Abs to the heterologous venom matrices (VMs). The avidity of the Abs to the homologous and the heterologous venoms is constantly ranked in the order; monovalent Ab>cross-reactive Ab>species-specific Ab. The avidity of the species-specific Abs to the homologous venoms of Echis coloratus (Eco) and Echis carinatus pyramidum (Epy) were 1.20+/-0.26 and 1.10+/-0.29, respectively. The avidity of the species-specific Abs to the heterologous venoms was too low to be detected. These results demonstrate for the first time that the avidity can be used to discriminate the immunologically high cross-reactive venoms. The discrimination of (14/14) venom samples of the two species on avidity bases confirmed the reliability and the specificity of the assay.