Diphtheria toxin (DT)

Diphtheria toxin is a potent exotoxin produced by Corynebacterium diphtheriae that serves as the primary virulence factor in diphtheria infections (Murphy, 1996). It is a single-chain polypeptide that is proteolytically cleaved into two subunits, A and B, linked by a disulfide bridge (UniProt, 2023). The B subunit facilitates binding to the heparin-binding EGF-like growth factor (HBEGF) receptor and mediates translocation into the host cell cytoplasm (Murphy, 1996). Once inside, the A subunit catalyzes the ADP-ribosylation of elongation factor 2 (EF-2), which permanently halts protein synthesis and results in cell death (StatPearls, 2023). Diphtheria toxoid is the chemically inactivated form of the toxin used in vaccines to stimulate the production of protective IgG antibodies (CDC, 2021). These antibodies neutralize the toxin by blocking its ability to bind to host receptors, thereby preventing the systemic complications of the disease (CDC, 2021). Additionally, modified versions of the toxin, such as CRM197, are used as carrier proteins in conjugate vaccines to enhance immune responses to other antigens (CDC, 2021).

Other names

Diphtheria toxoidDiphtheria toxin toxoidCRM197Corynebacterium diphtheriae toxinInactivated diphtheria toxin

Diphtheria toxin inhibits protein synthesis by catalyzing the ADP-ribosylation of host elongation factor 2 (EF-2) (Murphy, 1996). The toxoid form acts as an immunogen to induce neutralizing IgG antibodies that prevent the toxin from binding to the HBEGF receptor on host cells (CDC, 2021).