CRM197-derived peptide-MHC class II complex (CRM197-pMHCII)

CRM197-derived peptide epitopes bound to MHC class II represent the functional immunological unit responsible for the carrier effect in conjugate vaccines (Source: PubMed PMID 24055317). CRM197 is a non-toxic mutant of the diphtheria toxin, specifically featuring a glycine-to-glutamic acid substitution at position 52 (G52E), which eliminates its ADP-ribosyltransferase activity (Source: UniProt P00588). In the context of vaccination, antigen-presenting cells (APCs) such as dendritic cells internalize CRM197-polysaccharide conjugates and proteolytically process the CRM197 protein into various peptide epitopes (Source: PubMed PMID 11544333). These peptides are subsequently loaded onto Major Histocompatibility Complex (MHC) class II molecules for presentation on the cell surface. This peptide-MHC II complex is the primary target for T-cell receptors (TCRs) on CD4+ T-helper cells. Recognition of these specific CRM197 epitopes triggers T-cell activation and the secretion of cytokines, which are essential for driving B-cell differentiation into plasma cells and memory cells, thereby ensuring a high-affinity IgG response against the linked polysaccharide (Source: PubMed PMID 21148615). The use of CRM197 as a carrier is a cornerstone of modern vaccinology, enabling protection against encapsulated bacteria in infants and the elderly.

Other names

CRM197 epitopesCross-reacting material 197 peptide-MHC II complexDiphtheria toxin CRM197 mutant epitopesCRM197-MHCII

The complex acts as a ligand for T-cell receptors (TCRs) on CD4+ T-helper cells, triggering T-cell activation and subsequent B-cell help for high-affinity antibody production against conjugated polysaccharides.