Capsular polysaccharide of Streptococcus pneumoniae serotype 5 (CPS5)

The capsular polysaccharide of Streptococcus pneumoniae serotype 5 is a complex carbohydrate polymer that forms the outermost layer of the bacterium (NIH, 2019). It serves as a critical virulence factor by protecting the pathogen from the host's immune system, primarily by inhibiting complement-mediated opsonization and subsequent phagocytosis by neutrophils (ASM, 2010). Serotype 5 is highly invasive and is a frequent cause of severe infections such as pneumonia, meningitis, and bacteremia, often associated with outbreaks in specific populations (CDC, 2024). Due to its high pathogenicity, this polysaccharide is included as a target antigen in several widely used pneumococcal vaccines, including conjugate vaccines like PCV13, PCV15, and PCV20, as well as the polysaccharide vaccine PPSV23 (Medscape, 2025). These vaccines stimulate the production of protective antibodies that recognize the serotype 5 capsule, enabling the immune system to effectively identify and eliminate the bacteria (NIH, 2025).

Other names

Serotype 5 capsular polysaccharidePneumococcal polysaccharide serotype 5S. pneumoniae serotype 5 CPSPneumococcal CPS5

Induction of serotype-specific opsonophagocytic antibodies (IgG) that facilitate bacterial clearance by host immune cells through active immunization.