Neisseria meningitidis serogroup C capsular polysaccharide-CRM197 conjugate (MenC-CRM197)

Neisseria meningitidis serogroup C capsular polysaccharide presented as a polysaccharide-CRM197 conjugate is a vaccine antigen used to elicit protective immunity against invasive meningococcal disease [StatPearls, 2023]. The serogroup C capsule is composed of alpha 2-8-linked N-acetylneuraminic acid, which acts as a major virulence factor by protecting the bacterium from host immune defenses [PubMed, PMID: 11516442]. While pure polysaccharides are T-cell independent antigens that fail to induce memory or work effectively in infants, conjugation to the CRM197 carrier protein—a non-toxic variant of diphtheria toxin—enables a T-cell dependent immune response [PubMed, PMID: 24107131]. This process involves the recruitment of T-helper cells, leading to B-cell maturation, isotype switching to IgG, and the formation of memory B-cells [Journal of Infection, 2015]. Clinically, the conjugate induces serum bactericidal antibodies (SBA) that provide protection through complement-mediated killing of the bacteria [WHO, 2018]. This target is the basis for several highly effective conjugate vaccines, such as Menjugate and Menveo, which have significantly reduced the global burden of serogroup C meningitis [CDC, 2022].

Other names

Meningococcal group C conjugateMenC-CRM197Neisseria meningitidis serogroup C polysaccharide-CRM197 conjugateMeningococcal C conjugate vaccine antigen

The conjugate acts as a T-cell dependent antigen. The CRM197 carrier protein is processed by antigen-presenting cells and presented to T-helper cells via MHC class II. These T-cells provide essential signals to B-cells specific for the MenC polysaccharide, inducing isotype switching from IgM to high-affinity IgG and the development of memory B-cells, which provide long-term protection and allow for a booster response upon re-exposure.