Cross-reacting material 197 (CRM197) peptide-MHC class II complex (CRM197-pMHCII)

The CRM197 carrier protein peptide-MHC class II complex is a pivotal molecular assembly in the field of vaccinology, specifically for conjugate vaccines (Shinefield, 2010). CRM197 is a non-toxic, genetically detoxified version of the diphtheria toxin (containing a Gly52Glu mutation) that retains the ability to elicit a robust T-cell response (Bröker et al., 2011). When conjugated to polysaccharide antigens, CRM197 is internalized by antigen-presenting cells (APCs) and proteolytically processed into peptides within the endolysosomal compartment (Pichichero, 2013). These peptides are then loaded onto MHC class II molecules and presented on the APC surface to CD4+ T-helper cells, which recognize the complex via their T-cell receptors (Avci et al., 2011). This interaction triggers T-cell activation and the subsequent provision of help to B cells, facilitating isotype switching and the generation of long-lived memory B cells against the conjugated polysaccharide (Pichichero, 2013). This mechanism is fundamental to the success of vaccines against pathogens such as Streptococcus pneumoniae and Neisseria meningitidis (Shinefield, 2010).

Other names

CRM197-MHC II complexCRM197-derived epitope-MHC II complexCRM197-APC complexDiphtheria toxin CRM197 mutant peptide-MHC II complex

Induction of T-cell dependent immune response through MHC II presentation of carrier-derived peptides to CD4+ T-helper cells, which then provide essential signals for B-cell maturation and memory.