Capsular polysaccharides of 21 Streptococcus pneumoniae serotypes (PCV21)

Capsular polysaccharides are the primary virulence factors of Streptococcus pneumoniae, forming a protective carbohydrate layer that helps the bacteria evade the host's immune system by inhibiting opsonophagocytosis and complement deposition (Source: PubMed, PMID: 22412016). These polysaccharides are chemically diverse, leading to over 100 known serotypes, each with a unique structure that determines its immunogenicity and prevalence in disease (Source: CDC, Pneumococcal Disease). The 21-valent formulation (PCV21) specifically targets serotypes 3, 6A, 7F, 8, 9N, 10A, 11A, 12F, 15A, 15C, 16F, 17F, 19A, 20, 22F, 23A, 23B, 24F, 31, 33F, and 35B, which are responsible for a significant portion of invasive pneumococcal disease in adults (Source: FDA, Capvaxive Label). When these polysaccharides are conjugated to a carrier protein like CRM197, they elicit a T-cell dependent immune response, which is characterized by the production of high-affinity antibodies and the establishment of immunological memory (Source: Merck, Capvaxive Product Information). This targeted approach provides robust protection against life-threatening conditions such as pneumonia, meningitis, and bacteremia caused by the specific S. pneumoniae strains included in the vaccine. By focusing on the serotypes most prevalent in adult disease, this target represents a significant advancement in preventative medicine for vulnerable populations.

Other names

Pneumococcal capsular polysaccharidesV116 antigens21-valent pneumococcal conjugate vaccine antigensStreptococcus pneumoniae capsular polysaccharides

Induction of serotype-specific antibodies that promote opsonophagocytosis of Streptococcus pneumoniae (Source: FDA, Capvaxive Label)