Ability of horse anti-Tityus discrepans F(ab')2 ELISA assay to recognize Tityus discrepans venom toxins

Venom composition of Tityus cerroazul (Scorpiones: Buthidae) reveals similarities with venoms of other scorpion species from northern South America

Several buthid scorpions from Costa Rica and Panama have been extensively characterized for their venom components. One exception is Tityus cerroazul, a peculiar species classified in the subgenus Tityus, separated from the rest of the members of the genus that inhabit this geographic region. Although it has been described as a species that prefers natural areas with low human impact, which could explain the few reported envenomation cases, pre-clinical studies indicate that its venom may be toxic to mammals. This analysis describes the venom composition and enzymatic activities of T. cerroazul specimens from Panama. Among the identified venom components, we report the presence of NaTxs TdNa5 and bactridin-1 from T. discrepans from Venezuela, as well as partial sequences corresponding to other putative Na+ and K+ toxins, antimicrobial peptides, protease inhibitors, and secreted proteins, mostly found in the venoms of the T. (Atreus) species. We also confirmed the presence of the four peptides (Tce1-Tce4) identified by previous molecular analyses. In conclusion, our study suggests that T. cerroazul does not align closely with the venom of species currently assigned to the subgenus Tityus. Instead, it shows a greater similarity to the venom of the Atreus subgenus, which includes most of the Tityus species that inhabit the region. This finding underscores the need to revise its taxonomic classification based on molecular phylogenetic characters.

Divergence in toxin antigenicity and venom enzymes in Tityus melici, a medically important scorpion, despite transcriptomic and phylogenetic affinities with problematic Brazilian species

The Brazilian scorpion Tityus melici, native to Minas Gerais and Bahia, is morphologically related to Tityus serrulatus, the most medically significant species in Brazil. Despite inhabiting scorpion-envenomation endemic regions, T. melici venom remains unexplored. This work evaluates T. melici venom composition and function using transcriptomics, enzymatic activities, and in vivo and in vitro immunological analyses. Next-Generation Sequencing unveiled 86 components putatively involved in venom toxicity: 39 toxins, 28 metalloproteases, seven disulfide isomerases, six hyaluronidases, three phospholipases and three amidating enzymes. T. serrulatus showed the highest number of toxin matches with 80-100 % sequence similarity. T. melici is of medical importance as it has a venom LD50 of 0.85 mg/kg in mice. We demonstrated venom phospholipase A2 activity, and elevated hyaluronidase and metalloprotease activities compared to T. serrulatus, paralleling our transcriptomic findings. Comparison of transcriptional levels for T. serrulatus and T. melici venom metalloenzymes suggests species-specific expression patterns in Tityus. Despite close phylogenetic association with T. serrulatus inferred from COI sequences and toxin similarities, partial neutralization of T. melici venom toxicity was achieved when using the anti-T. serrulatus antivenom, implying antigenic divergence among their toxins. We suggest that the Brazilian therapeutic scorpion antivenom could be improved to effectively neutralize T. melici venom.