Diphtheria toxin cross-reacting material 197 (CRM197)

Diphtheria toxin cross-reacting material 197 (CRM197) is a non-toxic mutant of the diphtheria toxin produced by Corynebacterium diphtheriae, characterized by a single amino acid substitution (Gly52Glu) in its A subunit [1, 5]. This mutation eliminates the ADP-ribosyltransferase activity responsible for the toxin's lethality while preserving its structural integrity and its ability to bind to the heparin-binding EGF-like growth factor (HB-EGF) receptor [2, 5]. CRM197 is most widely recognized for its role as a highly effective carrier protein in conjugate vaccines, such as those targeting Streptococcus pneumoniae and Neisseria meningitidis, where it enhances the immunogenicity of polysaccharide antigens by eliciting a T-cell-dependent immune response [2, 4]. Beyond its use in vaccines, CRM197 is investigated as a therapeutic agent in oncology due to its ability to bind and sequester HB-EGF, which is frequently overexpressed in various cancers and promotes tumor cell proliferation and survival [3]. Its dual role as an immunological adjuvant and a targeted ligand makes it a versatile tool in both infectious disease prevention and cancer therapy research [4, 5].

Other names

CRM197CRM-197Cross-reacting material 197Diphtheria toxin G52E mutantDiphtheria toxin CRM197DT-CRM197

CRM197 functions primarily as a carrier protein in conjugate vaccines, where it provides T-cell epitopes that facilitate the conversion of T-independent polysaccharide antigens into T-dependent antigens, thereby inducing high-affinity antibodies and long-term immunological memory [2, 4]. In therapeutic research, CRM197 acts as a specific inhibitor of Heparin-binding EGF-like growth factor (HB-EGF); it binds to HB-EGF with high affinity, preventing its interaction with the Epidermal Growth Factor Receptor (EGFR/ErbB1) and HER4 (ErbB4), which effectively inhibits downstream signaling pathways that drive tumor cell proliferation and survival [3, 5].