Pneumococcal capsular polysaccharide (24 serotypes) (CPS-24)

Pneumococcal capsular polysaccharides are complex carbohydrate polymers that encapsulate the bacterium Streptococcus pneumoniae, serving as its primary virulence factor. These polysaccharides shield the bacteria from the host's innate immune system by preventing opsonization and subsequent phagocytosis by immune cells (CDC, 2023). There are over 100 distinct serotypes of S. pneumoniae, each characterized by a unique polysaccharide structure that determines its immunogenicity and prevalence in disease (NIH, 2022). The 24-valent target specifically encompasses polysaccharides from 24 serotypes selected for their high contribution to the global burden of invasive pneumococcal disease, including pneumonia, meningitis, and febrile bacteremia. In therapeutic development, these polysaccharides are utilized as antigens in conjugate vaccines to stimulate a protective immune response. By chemically linking the polysaccharides to a carrier protein, the vaccine converts the T-cell independent polysaccharide into a T-cell dependent antigen, which induces high-affinity IgG antibodies and immunological memory (Vaxcyte, 2024). These antibodies bind to the capsule of invading bacteria, facilitating their clearance via opsonophagocytosis. The expansion to 24 serotypes is designed to provide broader protection than earlier 13, 15, or 20-valent formulations, specifically targeting emerging serotypes that have increased in prevalence due to serotype replacement (PubMed, 2023).

Other names

Streptococcus pneumoniae capsular polysaccharidesPneumococcal CPS24-valent pneumococcal antigensS. pneumoniae surface polysaccharides

Active immunization via induction of serotype-specific opsonizing antibodies (IgG) through T-cell dependent immune response when conjugated to a carrier protein.