Clostridioides difficile toxin A N-terminal epitope (residues 26-39) (TcdA26-39)

Clostridioides (formerly Clostridium) difficile toxin A (TcdA) is a large, multi-domain exotoxin that serves as a primary virulence factor in Clostridioides difficile infection (CDI) [3]. The TcdA26-39 epitope is a specific 14-amino acid sequence (SGNIDDKYYFNETK) located within the N-terminal glucosyltransferase domain (GTD) of the toxin [1, 2]. This epitope is critical for the toxin's enzymatic function, which involves the covalent attachment of a glucose moiety to host Rho family GTPases, leading to the collapse of the actin cytoskeleton and subsequent cell death [1, 3]. Because this sequence is highly conserved across diverse C. difficile strains, including hypervirulent ribotypes like NAP1/027, it has become a focal point for the development of neutralizing monoclonal antibodies [1]. Experimental antibodies like 1B11 bind specifically to this epitope to inhibit the toxin's catalytic activity, offering a potential therapeutic strategy to mitigate the severe mucosal damage and inflammation associated with pseudomembranous colitis [1]. Unlike antibodies such as actoxumab that target the C-terminal receptor-binding repeats, targeting the TcdA26-39 epitope provides a direct means of neutralizing the toxin's intracellular enzymatic "warhead" [1, 4]. Sources: [1] Wang, H., et al. (2012). "Identification of a highly conserved neutralizing epitope in the N-terminal domain of Clostridium difficile toxin A." PLoS ONE. [2] UniProt P16154 (TCDA_CLODI). [3] Kuehne, S. A., et al. (2010). "The role of toxin A and toxin B in Clostridium difficile infection." Nature. [4] Orth, P., et al. (2014). "Structural basis for the neutralization of Clostridium difficile toxin A by the monoclonal antibody actoxumab." Journal of Biological Chemistry.

Other names

TcdA residues 26-39TcdA GTD epitope1B11 epitopeClostridium difficile toxin A epitope 26-39SGNIDDKYYFNETK peptide

Neutralization of toxin enzymatic activity by binding to the glucosyltransferase domain, thereby preventing the glucosylation of host Rho family GTPases and subsequent cytopathic effects.