BoNTs

Botulinum neurotoxins (BoNTs) are a group of proteins produced by the bacterium Clostridium botulinum and related species. These toxins are responsible for botulism, a severe and potentially fatal illness characterized by muscle weakness and paralysis. BoNTs are among the most potent toxins known to science, with a lethal dose estimated to be as low as 1 nanogram per kilogram of body weight.

BoNTs are classified into seven serotypes (A-G), each with distinct neurotoxic properties. They are produced as single-chain proteins that are proteolytically cleaved into two subunits: a heavy chain (Hc) and a light chain (Lc). The Lc binds to specific receptors on the surface of nerve terminals, while the Hc enters the cell and inhibits the release of acetylcholine, a neurotransmitter essential for muscle contraction.

BoNTs have been used medically for over a century, primarily for the treatment of various neuromuscular disorders such as dystonia, spasticity, and hyperhidrosis. They are administered via intramuscular injections, where the toxin inhibits the release of acetylcholine in the target muscle, leading to a temporary paralysis. The effects of BoNTs are reversible, as the muscle gradually regains its function as new nerve terminals are formed.

Despite their medical applications, BoNTs pose a significant risk as biological weapons due to their high toxicity and ease of production. They have been used in terrorist attacks and are considered a category A select agent by the Centers for Disease Control and Prevention. The production and use of BoNTs are tightly regulated by international agreements to prevent their misuse.