Ontogenetic changes in the venom of Metlapilcoatlus nummifer, the mexican jumping viper.

The viperid genus Metlapilcoatlus (previously Atropoides) is represented in Mexico by four species: M. olmec, M. mexicanus, M. occidus, and M. nummifer. To date, no studies on their venoms have been reported. Here, we comparatively characterized the venom from M. nummifer neonates (≤8 months of age), young adults (18 months) and adults (≥24 months). We performed biological and enzymatic activities, as well as electrophoretic and RP-HPLC profiling combined with proteomic assignment of major fractions. Venoms from neonates and adults differed in their electrophoretic and chromatographic profiles, indicating that an ontogenetic compositional shift occurs in this species. Protein family assignments showed that neonates produce a venom rich in Snake Venom Metalloproteinases (SVMPs) and Snake Venom Serine Proteases (SVSPs), but lacking Phospholipases A2 (PLA2s). In contrast, adults express abundant venom PLA2s, and lower molecular weight proteins, as evidenced by SDS-PAGE. Functionally, neonate venom did not display PLA2 or procoagulant activities, whereas adult venom did. Hemorrhagic activity was present in both neonate and adult venoms, with similar potencies. Finally, it is of considerable concern that the lethal activity of neither neonate nor adult venoms was neutralized by two therapeutic antivenoms produced in Mexico.

Biochemical and immunochemical characterization of venoms from snakes of the genus Agkistrodon.

In the present work, venoms from five species of the genus Agkistrodon were evaluated in terms of their enzymatic (Phospholipase A2 and caseinolytic) and biological (edema forming, hemorrhagic, procoagulant and lethal) effects. Horses were used to produce monovalent hyperimmune sera against each of three venoms (A. bilineatus, A. contortrix and A. piscivorus) and their neutralizing potency, expressed as Median Effective Dose (ED50), was determined against the venoms of all five species. In terms of PLA2 and caseinolytic activities, all venoms are extremely homogeneous. PLA2 activity is high, while caseinolytic activity is low when in contrast with that of the rattlesnake Crotalus simus. On the other hand, biological activities showed marked interspecific differences, particularly between the species from Mexico and those from the United States. Mexican species displayed higher edema-forming, hemorrhagic and lethal effects than US species, while none of the species studied presented procoagulant activity. All three monovalent hyperimmune sera showed good neutralizing potency against the analyzed venoms. Nonetheless, we observed relevant immunochemical differences among the venoms using ELISA and Western Blot assays. We conclude that the venoms of A. piscivorus (USA) and A. bilineatus would be ideal to use as immunogens for the production of a polyvalent antivenom with good neutralizing potency against the venoms of all the species of the genus.