Diphtheria toxin mutant carrier protein CRM197 (CRM197)

Diphtheria toxin mutant carrier protein CRM197 is a genetically detoxified variant of diphtheria toxin characterized by a single amino acid replacement (G52E), which abolishes its ADP-ribosyltransferase activity and renders the protein non-toxic[1][3][5][6]. CRM197 is widely used as a carrier protein in conjugate vaccines to enhance the immunogenicity of poorly immunogenic polysaccharide antigens, supporting robust, T-cell dependent immune responses particularly in pediatric populations[1][9]. CRM197 maintains the overall structure of native diphtheria toxin but lacks toxicity due to increased flexibility in the active-site loop, resulting from its G52E mutation[3][6]. It is commonly found in licensed conjugate vaccines against pathogens such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type B[1][9]. It is considered safe for use in humans, although scientific discussion continues about possible cytotoxic effects in some experimental systems[1].

Other names

Cross-reactive material 197Mutant diphtheria toxin carrier proteinCRM-197

Provides T-cell dependent immune response against weak antigens when conjugated to polysaccharides or haptens by making them immunogenic[1][9].