Streptococcus pneumoniae serotype 18C capsular polysaccharide-CRM197 conjugate (Pn18C-CRM197)

The Streptococcus pneumoniae serotype 18C capsular polysaccharide-CRM197 conjugate is a key antigenic component used in multivalent pneumococcal conjugate vaccines (PCVs) to prevent infections caused by Streptococcus pneumoniae (CDC, 2023). Serotype 18C is a significant pathogen responsible for invasive pneumococcal disease, including pneumonia, meningitis, and febrile bacteremia, particularly in pediatric and elderly populations (FDA, 2021). In this conjugate, the 18C capsular polysaccharide is chemically linked to CRM197, a non-toxic, recombinant variant of the diphtheria toxin that serves as a carrier protein (Pichichero, 2013). This conjugation is essential because pure polysaccharides are T-cell independent antigens that fail to induce a robust or lasting immune response in infants (Briles et al., 2019). Upon administration, the conjugate is processed by antigen-presenting cells, leading to the activation of T-helper cells, which in turn stimulate B-cells to produce high-affinity, serotype-specific IgG antibodies and establish long-term immunological memory (StatPearls, 2023). This mechanism not only protects the individual but also contributes to herd immunity by reducing the nasopharyngeal carriage of the bacteria in the population (PubMed, 2020). Clinical efficacy is typically monitored through serotype-specific antibody titers and opsonophagocytic assays (WHO, 2021).

Other names

Immune system via pneumococcal serotype 18C polysaccharide-CRM197 conjugatePn18C-CRM19718C-CRM197Pneumococcal serotype 18C conjugateCRM197-conjugated pneumococcal polysaccharide serotype 18C

Induces a T-cell dependent immune response by presenting the polysaccharide antigen in the context of a carrier protein (CRM197), leading to B-cell activation, high-affinity IgG production, and immunological memory.