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Diphtheria toxin is a single polypeptide chain of 535 amino acids consisting of two subunits linked by disulfide bridges, known as an A-B toxin.Binding to the cell surface of the B subunit (the less stable of the two subunits) allows the A subunit (the more stable part of the protein) to penetrate the host cell.
Diphtheria was a major public health scourge, killing entire families with acute airborne pulmonary disease, before diphtheria vaccine brought it under control. At the time Elek developed this test, control of the disease was not yet secured in all regions of the world. Today its control is threatened by vaccine hesitancy.
The diphtheria toxin precursor is a protein of molecular weight 60 kDa. Certain proteases, such as trypsin, selectively cleave DT to generate two peptide chains, amino-terminal fragment A (DT-A) and carboxyl-terminal fragment B (DT-B), which are held together by a disulfide bond . [ 23 ]
CRM197 is a genetically detoxified form of diphtheria toxin. A single mutation at position 52, substituting glutamic acid for glycine, causes the ADP-ribosyltransferase activity of the native toxin to be lost. The structural basis for the lack of CRM197 toxicity has recently been elucidated. [4]
The diphtheria toxin gene is encoded by the bacteriophage found in toxigenic strains, integrated into the bacterial chromosome. [13] The diphtheria toxin repressor is mainly controlled by iron. It serves as the essential cofactor for the activation of target DNA binding. A low concentration of iron is required in the medium for toxin production.
Diphtheria vaccine is a toxoid vaccine against diphtheria, an illness caused by Corynebacterium diphtheriae. [2] Its use has resulted in a more than 90% decrease in number of cases globally between 1980 and 2000. [ 3 ]
A corynebacteriophage (or just corynephage) is a DNA-containing bacteriophage specific for bacteria of genus Corynebacterium as its host. [1] Corynebacterium diphtheriae virus [2] strain Corynebacterium diphtheriae phage [2] (aka Corynephage β [3] or just β-phage [4] [5]) introduces toxigenicity into strains of Corynebacterium diphtheriae as it encodes diphtheria toxin, [6] [7] [8] [5] [4 ...
A small amount (0.1 ml) of diluted (1/50 MLD) diphtheria toxin is injected intradermally into one arm of the person and a heat inactivated toxin on the other as a control. If a person does not have enough antibodies to fight it off, the skin around the injection will become red and swollen, indicating a positive result.