Snake venoms represent a danger to human health, but also a gold mine of bioactive proteins that can be harnessed for drug discovery purposes. The evolution of snakes and their venom has been studied for decades, particularly via traditional morphological and basic genetic methods alongside venom proteomics. However, while the field of genomics has matured rapidly over the past 2 decades, owing to the development of next-generation sequencing technologies, snake genomics remains in its infancy. Here, we provide an overview of the state of the art in snake genomics and discuss its potential implications for studying venom evolution and toxinology. On the basis of current knowledge, gene duplication and positive selection are key mechanisms in the neofunctionalization of snake venom proteins. This makes snake venoms important evolutionary drivers that explain the remarkable venom diversification and adaptive variation observed in these reptiles. Gene duplication and neofunctionalization have also generated a large number of repeat sequences in snake genomes that pose a significant challenge to DNA sequencing, resulting in the need for substantial computational resources and longer sequencing read length for high-quality genome assembly. Fortunately, owing to constantly improving sequencing technologies and computational tools, we are now able to explore the molecular mechanisms of snake venom evolution in unprecedented detail. Such novel insights have the potential to affect the design and development of antivenoms and possibly other drugs, as well as provide new fundamental knowledge on snake biology and evolution.

Venomous snakes are important parts of the ecosystem, and their behavior and evolution have been shaped by their surrounding environments over the eons. This is reflected in their venoms, which are typically highly adapted for their biological niche, including their diet and defense mechanisms for deterring predators. Sub-Saharan Africa is rich in venomous snake species, of which many are dangerous to humans due to the high toxicity of their venoms and their ability to effectively deliver large amounts of venom into their victims via their bite. In this study, the venoms of 26 of sub-Saharan Africa's medically most relevant elapid and viper species were subjected to parallelized toxicovenomics analysis. The analysis included venom proteomics and in vitro functional characterization of whole venom toxicities, enabling a robust comparison of venom profiles between species. The data presented here corroborate previous studies and provide biochemical details for the clinical manifestations observed in envenomings by the 26 snake species. Moreover, two new venom proteomes (Naja anchietae and Echis leucogaster) are presented here for the first time. Combined, the presented data can help shine light on snake venom evolutionary trends and possibly be used to further improve or develop novel antivenoms.

The Eastern Long-Nosed Viper (Vipera ammodytes meridionalis) is considered one of the most venomous snakes in Europe. However, it is unknown whether ontogenetic variation in venom effects occurs in this subspecies and how this may impact antivenom efficacy. In this study, we compared the procoagulant activities of V. a. meridionalis venom on human plasma between neonate and adult venom phenotypes. We also examined the efficacy of three antivenoms—Viperfav, ViperaTAb, and Inoserp Europe—across our neonate and adult venom samples. While both neonate and adult V. a. meridionalis venoms produced procoagulant effects, the effects produced by neonate venom were more potent. Consistent with this, neonate venom was a stronger activator of blood-clotting zymogens, converting them into their active forms, with a rank order of Factor X >> Factor VII > Factor XII. Conversely, the less potent adult venom had a rank order of FXII marginally more activated than Factor VII, and both much more so than Factor X. This adds to the growing body of evidence that activation of factors besides FII (prothrombin) and FX are significant variables in reptile venom-induced coagulopathy. Although all three examined antivenoms displayed effective neutralization of both neonate and adult V. a. meridionalis venoms, they generally showed higher efficacy on adult venom than on neonate venom. The ranking of antivenom efficacy against neonate venom, from the most effective to the least effective, were Viperfav, Inoserp Europe, ViperaTAb; for adult venom, the ranking was Inoserp Europe, Viperfav, ViperaTAb. Our data reveal ontogenetic variation in V. a meridionalis, but this difference may not be of clinical concern as antivenom was effective at neutralizing both adult and neonate venom phenotypes. Regardless, our results highlight a previously undocumented ontogenetic shift, likely driven by the documented difference in prey preference observed for this species across age classes

Echis species (saw-scaled vipers) are WHO Category 1 medically significant venomous snakes with potent procoagulant venoms, which cause lethal venom-induced consumptive coagulopathy in human victims. Despite clinical presentations of bites varying significantly between individuals within the same species, the contribution of age-related changes in the venom biochemistry has not been investigated. This study investigated the ontogenetic changes in Echis pyramidum pyramidum venom and its impact on therapeutic efficacy. The efficacy of various antivenoms (Echitab, Echitab+ ICP, Inosan MENA, Inosan Pan African, and SAVP-Echis) was tested against both venom phenotypes. While both neonate and adult venoms were procoagulant, there were differences in the underlying biochemistry. Neonate venom was found to potently pathophysiologically activate Factor VII and Factor X, and to a lesser degree Factor XII. In contrast, adult venom was a slower clotter, less potent in activating FVII, equipotent with neonate venom on FXII, and inactive on FX. This is the first documentation of FVII and FXII activation for any Echis venom. The significant ontogenetic toxicological variations in Echis species were shown to impact antivenom efficacy. Among the tested antivenoms, SAVP-Echis was the most effective against both venom phenotypes, with adult venom being better neutralized. These findings suggest the need for a reconsideration of venom mixture selection in antivenom production through the inclusion of neonate venom. Additionally, the results indicate differential ontogenetic predatory ecology, providing a foundation for future natural history investigations.

Tetrodotoxin (TTX) is a neurotoxic molecule used by many animals for defense and/or predation, as well as an important biomedical tool. Its ubiquity as a defensive agent has led to repeated independent evolution of tetrodotoxin resistance in animals. TTX binds to voltage-gated sodium channels (VGSC) consisting of α and β subunits. Virtually all studies investigating the mechanisms behind TTX resistance have focused on the α subunit of voltage-gated sodium channels, where tetrodotoxin binds. However, the possibility of β subunits also contributing to tetrodotoxin resistance was never explored, though these subunits act in concert. In this study, we present preliminary evidence suggesting a potential role of β subunits in the evolution of TTX resistance. We gathered mRNA sequences for all β subunit types found in vertebrates across 12 species (three TTX-resistant and nine TTX-sensitive) and tested for signatures of positive selection with a maximum likelihood approach. Our results revealed several sites experiencing positive selection in TTX-resistant taxa, though none were exclusive to those species in subunit β1, which forms a complex with the main physiological target of TTX (VGSC Na_v1.4). While experimental data validating these findings would be necessary, this work suggests that deeper investigation into β subunits as potential players in tetrodotoxin resistance may be worthwhile.