Rabbit Anti-Tetanus Toxin (TeNT) Polyclonal Antibody

Tetanus toxin (TeNT) is an exotoxin produced by Clostridium tetani that invades the body through damaged skin epidermis or mucous membranes, causing Clostridium tetani to multiply in large numbers in an oxygen-deficient environment. Tetanus is a specific infectious disease that can cause local or systemic acute muscle spasms. The disease can infect humans or animals but is not contagious. Clostridium tetani is a Gram-positive anaerobic bacillus. It is the pathogen that causes tetanus and is mainly found in soil or feces. Clostridium tetani itself does not have the ability to invade and harm the human body. It cannot invade normal skin tissue and mucous membranes. It can only grow and multiply in local wound tissue, thereby producing clostridial neurotoxins.

Figure 1. The five steps of the molecular mechanism underlying the neuroparalytic action of tetanus neurotoxin (TeNT) and botulinum neurotoxins (BoNTs). (Sources: Pirazzini M, et al. 2022)

TeNT is a protein neurotoxin, which is the second most virulent biological toxin after botulinum toxin. About 100 ng can kill a person. The mortality rate of patients poisoned by tetanus toxin is very high. Even with active treatment, the mortality rate of tetanus patients is still as high as 20%~40%. TeNT is a neurotoxin produced by Clostridium tetani. It is composed of 1315 amino acids and is a protein with a relative molecular mass of 150kDa. Its structure is similar to that of botulinum toxin. Naturally formed TeNT is initially non-toxic and exists in the form of a single-chain polypeptide. Mature TeNT is toxic only when it is cleaved by bacterial proteases or in vitro proteases to form a double-chain form. The double-chain form of TeNT is composed of a light chain (Light chain, L) and a heavy chain (Heavy chain, H) connected by a pair of disulfide bonds. Among them, H is composed of two domains, namely the amino terminus of the heavy chain (N-terminal of Heavy chain, Hn) and the carboxyl terminus of the heavy chain (C-terminal of Heavy chain, Hc). L is the active part of the toxin, which has Zn²⁺-dependent endonuclease activity and has the function of cutting the substrate VAMP-2 protein; H can make the protein break through the blood-brain barrier and enter the central nervous system. Hc is a domain of about 50kDa composed of 4 a helices and 6 beta folds, which is also a ganglioside domain. This domain contains two polysialic acid ganglioside binding sites, which is responsible for recognizing and binding to receptors on the outer plasma membrane of motor neurons; Hn is a migration domain, which is composed of two a helices and has a relative molecular mass of about 50kDa. It is responsible for delivering the toxin light chain to the inside of the neuronal cell, so that the active part of the toxin interacts with the SNARE protein complex, inhibiting the continuous release of acetylcholine, and the motor neurons will be in a state of continuous excitement, which will eventually lead to continuous muscle contraction and tetanic contraction, which can cause death in severe cases.

In nature, tetanus toxin first exists in the form of a non-toxic precursor toxin. It needs to further mature and form a double-chain structure to be toxic, connected by disulfide bonds. Although tetanus toxin and botulinum toxin are equally deadly, their poisoning reactions and poisoning mechanisms are completely different. The heavy chain of botulinum toxin can bind to receptors on the surface of nerve cells, and the toxin protein enters the cell through receptor-mediated endocytosis. After the toxin protein enters the cell, the light and heavy chains can be separated. The heavy chain can mediate the formation of transmembrane holes on the inner membrane, allowing the active part of the toxin to enter the cytoplasm; the light chain contains a Zn²⁺-dependent specific proteolytic enzyme region, which can cut related proteins and prevent the release of acetylcholine, ultimately leading to severe neurological disorders and flaccid paralysis. The transport of tetanus toxin in the body is neurotropic. TeNT protein binds to peripheral motor neurons through receptors and enters cells through receptor-mediated endocytosis, so that vesicles carrying toxin proteins can be transported in reverse, along peripheral nerve cells to the spinal cord, and then released from the junction of motor neurons and inhibitory neurons. The toxin protein enters the vesicles of inhibitory neurons, and then the vesicles become acidified, causing the disulfide bonds to dissociate. The light and heavy chain molecules enter the cytoplasm. The light chain molecules contain Zn²⁺-dependent specific protease regions that can cut VAMP-2 proteins, thereby inhibiting the release of neurotransmitters such as aminoacetic acid and aminobutyric acid. Since the target cells are inhibitory neurons, the lack of neurotransmitters leads to the disappearance of the inhibitory effect on motor neurons, causing motor neurons to remain in an excited state, which is clinically manifested as muscle tonic contraction.

Tetanospasmin
TeNT
Clostridium tetani toxin
Tetanus neurotoxin