Biotechnological Trends in Spider and Scorpion Antivenom Development

Abstract

Spiders and scorpions are notorious for their fearful dispositions and their ability to inject venom into prey and predators, causing symptoms such as necrosis, paralysis, and excruciating pain. Information on venom composition and the toxins present in these species is growing due to an interest in using bioactive toxins from spiders and scorpions for drug discovery purposes and for solving crystal structures of membrane-embedded receptors. Additionally, the identification and isolation of a myriad of spider and scorpion toxins has allowed research within next generation antivenoms to progress at an increasingly faster pace. In this review, the current knowledge of spider and scorpion venoms is presented, followed by a discussion of all published biotechnological efforts within development of spider and scorpion antitoxins based on small molecules, antibodies and fragments thereof, and next generation immunization strategies. The increasing number of discovery and development efforts within this field may point towards an upcoming transition from serum-based antivenoms towards therapeutic solutions based on modern biotechnology.

Keywords: antibodies; antitoxin; antivenom; antivenom design; scorpion venom; spider venom; venom neutralization; venomics.

Figure 1

The ten protein families with the highest number of entries among the annotated (A) spider and (B) scorpion toxins in the UniProtKB database [42]. For spiders 543 toxins do not belong to any of the top ten protein families, while this number is 129 for scorpions. The bars are colored according to the taxonomic family affiliation of each toxin entry.

Figure 2

Number of toxins in each taxonomic family for which LD₅₀s and/or three three-dimensional structures have been reported in the UniProtKB database [42]. (A) Spider toxins; (B) Scorpion toxins.

Figure 3

Number of toxins in each protein family for which LD₅₀s and/or three three-dimensional structures have been reported in the UniProtKB database [42]. (A) Spider toxins; (B) Scorpion toxins.

Figure 4

Mechanism of inactivation of metalloproteases. The chelation agent EDTA chelates metal ions and scavenges these from active metalloproteases leaving behind the inactive metalloprotease apoprotein.

Figure 5

Schematic representation of the antibody formats mentioned in the text. (A) Whole mAb and mAb fragments obtained after enzymatic cleavage, usually derived from hybridoma cell lines; (B) Recombinant antibody molecules of human or murine origin, usually selected from synthetic libraries by phage display selection; (C) Camelid heavy chain antibody (HCAb) and derived formats.

Figure 6

Schematic representation of a directed evolution approach by phage display selection coupled to mutagenesis for discovery of high affinity antibody variants. (A) Representation of a phage particle encoding and displaying scFv molecules on its surface. (B) Phage particles displaying a library of antibody fragments are panned against the target toxin (1). Strongly binding phages remain bound to the target, while non-binding phages are washed away (2). Binding phages are eluted and (3) submitted to mutagenesis, usually by error prone PCR or chain shuffling, with the intention of obtaining phage particles with enhanced affinities towards the target (4). The obtained mutants are amplified in E. coli and submitted to new panning rounds (5). After a few iterative cycles, the most strongly binding phages are eluted, and their DNA is sequenced to reveal which antibody fragments bound most strongly to the target.

Figure 7

Schematic representation of the use of peptidic epitopes for immunization. A peptide containing the most reactive epitope sequence(s) from selected toxin(s) is constructed and used for immunization of mice. In a successful immunization, the antibodies raised will not only target the peptide, but also the parent toxin(s).