CD4+ T-cell receptor specific for CRM197-derived peptides presented on MHC class II (CRM197-specific TCR)

CD4+ T-cell receptors (TCRs) specific for CRM197-derived peptides presented on MHC class II molecules are the fundamental immunological targets engaged by CRM197-based conjugate vaccines. CRM197 is a non-toxic, genetically detoxified mutant of the diphtheria toxin (specifically a G52E point mutation) that serves as a potent carrier protein for poorly immunogenic polysaccharide antigens [Bröker et al., 2011]. The biological function of these TCRs is to recognize specific peptide fragments of CRM197 after they have been processed and displayed by antigen-presenting cells (APCs) via the Major Histocompatibility Complex (MHC) class II pathway [Rappuoli, 2018]. This recognition event triggers the activation of CD4+ T-helper cells, which subsequently provide essential signals—such as CD40 ligand expression and cytokine secretion (e.g., IL-4, IL-21)—to B-cells [Shinefield, 2010]. This T-cell help is critical for inducing B-cell class switching from IgM to high-affinity IgG and the formation of long-lived memory B-cells against the conjugated polysaccharide [Pichichero, 2013]. Consequently, these TCRs are central to the efficacy of widely used vaccines against Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b [Bröker et al., 2011]. Understanding the repertoire and activation threshold of these TCRs is vital for optimizing vaccine design and overcoming challenges like carrier-induced epitopic suppression [Rappuoli, 2018].

Other names

CRM197-specific T-cell receptorDiphtheria toxin-specific T-cell receptorCarrier-specific T-cell receptorCRM197-specific CD4+ T-cell receptor

Activation of CD4+ T-helper cells through TCR recognition of CRM197 peptides presented on MHC class II molecules, leading to B-cell help, class switching, and high-affinity antibody production.