Streptococcus pneumoniae capsular polysaccharides (26 serotypes)

The target consists of the capsular polysaccharide epitopes from 26 distinct serotypes of Streptococcus pneumoniae, which are the primary virulence factors of the bacterium. These polysaccharides form a protective outer layer that helps the pathogen evade the host immune system by inhibiting phagocytosis (NIH, 2025). The 26-valent target includes serotypes found in existing vaccines (such as 1, 3, 4, 5, 6A, 6B, 7F, 8, 9V, 10A, 11A, 12F, 14, 15B, 18C, 19A, 19F, 22F, 23F, and 33F) along with six additional serotypes (15A, 16F, 23A, 23B, 24F, and 35B) to provide broader coverage against invasive pneumococcal disease (IPD) (ClinicalTrials.gov, 2025). Vaccines targeting these epitopes are typically conjugate vaccines, where the polysaccharides are chemically linked to a carrier protein to stimulate a T-cell dependent immune response (AdisInsight, 2026). This results in the production of high-affinity opsonophagocytic antibodies and long-term immunological memory, significantly reducing the incidence of pneumonia, meningitis, and sepsis caused by the covered serotypes (CDC, 2026). The inclusion of additional serotypes like 24F and 35B is particularly significant as these have emerged as major causes of disease following the widespread use of lower-valency vaccines (NIH, 2025). By expanding the antigenic profile, these vaccines aim to overcome the challenge of serotype replacement and provide more comprehensive global protection (ResearchGate, 2024).

Other names

Pneumococcal capsular polysaccharidesS. pneumoniae CPS26-valent pneumococcal antigensPneumococcal polysaccharide epitopes

Induction of serotype-specific opsonophagocytic antibodies (IgG) that facilitate phagocytosis and clearance of Streptococcus pneumoniae by the host immune system.