Streptococcus pneumoniae capsular polysaccharide serotype 24F (24F CPS)

Streptococcus pneumoniae capsular polysaccharide serotype 24F is a complex carbohydrate polymer that constitutes the outermost protective layer of the 24F pneumococcal serotype. This polysaccharide serves as a primary virulence factor by providing an antiphagocytic shield, which prevents host immune cells from recognizing and engulfing the pathogen, thereby facilitating systemic dissemination (Calix et al., 2012, J Biol Chem; Hyams et al., 2010, Infect Immun). Serotype 24F has emerged as a significant clinical concern due to serotype replacement, where it has become a leading cause of invasive pneumococcal disease (IPD) following the widespread use of vaccines that do not cover this specific antigen (Nakano et al., 2020, Emerging Infectious Diseases; Lo et al., 2022, Lancet Microbe). It is frequently associated with multi-drug resistance, particularly against penicillin and macrolides, making infections difficult to treat with standard antibiotics (Nakano et al., 2020). As a therapeutic target, the 24F polysaccharide is utilized as an antigen in next-generation pneumococcal conjugate vaccines (PCVs), such as the recently approved 21-valent vaccine Capvaxive and the 24-valent candidate VAX-24 (FDA, 2024, Capvaxive Prescribing Information; Vaxcyte, 2024, Pipeline Data). These vaccines aim to induce high titers of opsonophagocytic antibodies that specifically target the 24F capsule, enabling the host's immune system to clear the bacteria effectively (FDA, 2024).

Other names

Pneumococcal polysaccharide serotype 24FS. pneumoniae serotype 24F antigenSpn24F CPS24F capsular polysaccharide

Induction of serotype-specific humoral immunity and opsonophagocytic activity through active immunization