New insight into venom composition in Tityus melici and related medical important Tityus species

 

 Yan Kalapothakis and co-workers recently published a study of the venom composition of the medical important Brazilian scorpion Tityus melici Lourenço, 2003 (Buthidae). This species is morphologically related to Tityus serrulatus Lutz & Mello, 1922, which is the most medically significant species in Brazil.

Dr. Adolofo Borges, who is one of the authors, has kindly summed up the results of this study for me: "The article presents evidence indicating that venom from Tityus melici, a species belonging to the "Tityus stigmurus" complex, exhibits divergence in toxin antigenicity and enzyme content/activity with respect to Tityus serrulatus using transcriptomic and biochemical approaches. The antivenom prepared in Brazil against T. serrulatus (also within the "stigmurus" group) only partially neutralizes toxicity of this venom, suggesting toxin divergence among these closely related species."

This type of knowledge is very useful when it comes to how to handle and treat serious scorpionism involving these species in Brazil.

Abstract:
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.

Reference:
Kalapothakis Y, Miranda K, Aragão M, Larangote D, Braga-Pereira G, Noetzold M, et al. Divergence in toxin antigenicity and venom enzymes in Tityus melici, a medically important scorpion, despite transcriptomic and phylogenetic affinities with problematic Brazilian species. Int J Biol Macromol. 2024;263:130311. [Subscription required for full text]

Thanks to Dr. Borges for informing me about the new article and for summing up the results for me!