Diphtheria toxin mutant CRM197 protein carrier (CRM197)

Diphtheria toxin mutant CRM197 protein carrier (CRM197) is a genetically detoxified, single-amino-acid mutant (Gly52Glu) of diphtheria toxin. This alteration eliminates its ADP-ribosyltransferase enzymatic activity, rendering it non-toxic, while preserving immunogenicity and structural similarity to the native toxin. CRM197 is widely used as a carrier protein in conjugate vaccines for encapsulated bacteria such as *Haemophilus influenzae*, *Streptococcus pneumoniae*, and *Neisseria meningitidis*, enhancing immune responses against weak antigens by enabling T-cell help. It is composed of a single polypeptide chain (535 amino acids, ~58 kDa) and retains full lysine amines for efficient conjugation. CRM197 may also act as a competitive inhibitor of HB-EGF binding to the HB-EGF receptor (the diphtheria toxin receptor). Carrier-induced suppression and anti-carrier immune responses are potential challenges in repeated vaccine use. CRM197 is distinguished from the original diphtheria toxin by its lack of toxicity but immunological equivalence[1][2][3][5][6].

Other names

CRM197Cross-Reacting Material 197non-toxic diphtheria toxin mutant

Acts as a carrier protein to elicit T-cell-dependent immune responses to weak antigens in conjugate vaccines Competitive inhibition of HB-EGF binding to its receptor in research contexts Lacks intrinsic toxicity due to loss of ADP-ribosyltransferase activity