Capsular polysaccharide of Streptococcus pneumoniae serotype 15B (Pn15B)

The capsular polysaccharide of Streptococcus pneumoniae serotype 15B is a complex carbohydrate polymer that encapsulates the bacterium, serving as its primary virulence factor. This polysaccharide layer protects the pathogen from the host's immune system by inhibiting opsonization and subsequent phagocytosis by macrophages and neutrophils (CDC, 2022; NIH, 2015). Chemically, serotype 15B is distinguished by its specific arrangement of galactose, glucose, rhamnose, and N-acetylglucosamine residues, along with glycerol phosphate and characteristic O-acetylation (PubMed, 2012). It is a major target in the development of pneumococcal vaccines designed to prevent invasive diseases such as bacteremia, meningitis, and pneumonia (WHO, 2019). Serotype 15B is included as an antigen in several high-valent vaccines, including the 23-valent pneumococcal polysaccharide vaccine (PPSV23), the 20-valent pneumococcal conjugate vaccine (PCV20), and the 21-valent conjugate vaccine (V116) (FDA, 2021; Merck, 2024). Upon administration, these vaccines stimulate the production of serotype-specific antibodies that bind to the polysaccharide, facilitating bacterial clearance through the complement system and phagocytic cells (FDA, 2021). Monitoring the prevalence of this serotype is crucial due to the phenomenon of serotype replacement following the widespread use of lower-valent vaccines (CDC, 2022).

Other names

Pn15B CPSPneumococcal polysaccharide serotype 15BStreptococcus pneumoniae serotype 15B capsular polysaccharide15B capsular polysaccharide

Induction of active immunity through the production of serotype-specific IgG antibodies and opsonophagocytic activity