Clostridioides difficile toxin B and related antigens (TcdB)

Clostridioides difficile toxin B (TcdB) and related antigens, such as Toxin A (TcdA), Binary Toxin (CDT), and Glutamate Dehydrogenase (GDH), are the primary virulence factors and diagnostic markers produced by the bacterium Clostridioides difficile [NIH, MDPI, ASM]. These toxins are responsible for the clinical manifestations of C. difficile infection (CDI), which range from mild diarrhea to life-threatening pseudomembranous colitis and toxic megacolon [NIH]. TcdB and TcdA function as glucosyltransferases that enter host colonic epithelial cells and inactivate Rho-family GTPases, leading to the collapse of the actin cytoskeleton, cell death, and a robust inflammatory response [NIH, MDPI]. TcdB is considered the more potent and clinically significant toxin in humans, as strains producing only TcdB remain highly virulent and capable of causing the full spectrum of disease [NIH, Nature Communications]. Therapeutic strategies targeting these antigens primarily involve monoclonal antibodies, such as bezlotoxumab, which neutralizes TcdB by preventing its binding to host receptors like CSPG4 and FZD2 [NIH, Drugs.com]. While standard antibiotics like vancomycin and fidaxomicin target the vegetative bacteria, antitoxin therapies provide a specialized approach to reducing the high rates of disease recurrence by protecting the intestinal lining from toxin-mediated damage [NIH, Drugs.com]. These antigens also serve as critical biomarkers for diagnosis, with tests identifying the presence of toxin genes or the toxins themselves in stool samples [NIH, ASM]. Despite the success of TcdB-targeted therapy, the emergence of hypervirulent strains and the role of related antigens like CDT continue to present challenges in the management of CDI [NIH].

Other names

Toxin BToxin ATcdBTcdABinary toxinCDTClostridioides difficile toxinsC. diff toxinsGlutamate dehydrogenaseGDH

Bezlotoxumab binds to the C-terminal combined repetitive oligopeptide (CROP) domain of TcdB, preventing the toxin from binding to host cell receptors such as chondroitin sulfate proteoglycan 4 (CSPG4) and frizzled class receptors (FZD2, FZD7), thereby blocking toxin internalization and subsequent cytopathic effects [NIH, Drugs.com, Nature Communications].