Neutralizing human anti crotoxin scFv isolated from a nonimmunized phage library

Area of Science:

• Immunology
• Biochemistry
• Pharmacology

Background:

• Snakebite envenomation, particularly from Crotalus durissus terrificus, poses a significant health threat.
• Crotoxin, the primary toxin in C. durissus terrificus venom, is a neurotoxin that causes paralysis by blocking neuromuscular transmission.
• Current treatments for snakebite envenomation can have adverse effects, necessitating the development of novel therapeutic strategies.

Purpose of the Study:

• To isolate and characterize human single-chain variable fragment (scFv) antibodies specific for crotoxin using combinatorial phage display.
• To evaluate the in vivo neutralizing activity and biological effects of these human anticrotoxin scFvs.
• To explore the potential of these scFvs as a novel therapeutic approach for C. durissus terrificus envenomation.

Main Methods:

• Utilized a naive human scFv library exceeding 10^10 clones for phage display selection.
• Screened for scFvs that bind specifically to crotoxin, the main toxic component of C. durissus terrificus venom.
• Assessed the biological and immunological effects of isolated anticrotoxin scFvs, including neutralization of toxicity, myotoxicity, and enzymatic activity.

Main Results:

• Successfully isolated three human anticrotoxin scFvs (scFv 1, scFv 6, and scFv 8) with in vivo neutralizing activity.
• Demonstrated that scFv 8 reduces crotoxin-induced myotoxicity, while scFv 1 alters its in vitro enzymatic activity.
• All three scFvs recognize a common region on the crotoxin complex, and exhibit significant amino acid homology.

Conclusions:

• Human anticrotoxin scFvs derived from a naive library show promise for passive immunotherapy against C. durissus terrificus venom.
• The distinct biological activities of the isolated scFvs suggest a multifaceted therapeutic potential.
• These findings pave the way for developing a new, potentially less aggressive, passive immune therapy for crotoxin poisoning.