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Bezlotoxumab https://en.wikipedia.org/wiki/Bezlotoxumab    Stub

Clostridium difficile Toxin B https://en.wikipedia.org/wiki/Clostridium_difficile_toxin_B    Start

Mechanism of TcdB Neutralizing Bezlotoxumab
By x-ray crystallized structure of N-terminal of TcdB, the toxin is identified to consist of three domains: a GTD, a cysteine protease and a combined repetitive oligopeptides, CROP domain. Separate the entire CROP domain into four different peptide units, including the entire CROP domain as B1 (residues 1834-2366), as well as fragments of the CROP domain being B2 (residues 1834-2101), B3 (residues 1949-2275), and B4 (residues 2102-2366). Western Blot analysis of these peptides reinforce that antibody bezlotoxumab does indeed recognize a specific epitope on toxin TcdB and will have high affinity for that region. There lack of interaction between the GTD domain and bezlotoxumab, as well as the apparent interaction in B1, which is representative of the entire CROP domain. Bezlotoxumab specifically inhibits the CROP domain of TcdB. B2 andB3 have an interaction between bezlotoxumab and those individual peptide regions, or possibly the overlapping residues region between the two. B4 fragment does not interact with the specific portion of the CROP domain. The kinetics of bezlotxumab binding to TcdB and its various fragments were determine by surface plasmon resonance. By HDX-MS analysis a method that relies on the measurement and comparison of the degree of deuterium incorporation by an antigen following incubation in D2O in absence and presence of antibody. Characterization of peptide B1 as full CROP domain of TcdB by HDX-MS reveal that fragment corresponding to residues 1902-1914, 2021-2025, 2033-2038 and 2091-2096 appear to have a strong interaction with bezlotoxumab, as denoted by the minimal levels of deuteration. Indeed all of these region are present within the B2. It suggests that the antibody specifically react with the B2 region of the CROP domain. furthermore, leading to the conclusion that TcdB epitope lies within the N-terminus of the CROP domain.