Streptococcus pneumoniae Type 22F Capsular Polysaccharide (CPS 22F)

The Streptococcus pneumoniae type 22F capsular polysaccharide (CPS) is a serotype-specific carbohydrate polymer that forms the outermost layer of the bacterial cell. This capsule is a critical virulence factor, protecting the bacterium from host immune responses, particularly by inhibiting opsonophagocytic clearance mechanisms. The type 22F CPS is one of over 98 recognized pneumococcal serotypes, each defined by unique structural features in their capsular polysaccharides. The capsule shields *S. pneumoniae* from complement-mediated killing and phagocytosis by immune cells, making it essential for survival and pathogenicity in the host. It serves as a major antigenic determinant; immunity to one serotype does not confer protection against others due to significant structural diversity among CPS types. Type 22F has become increasingly relevant due to shifts in serotype prevalence following widespread vaccine use targeting other common serotypes. It is included in current multivalent pneumococcal vaccines such as PPSV23 because it elicits protective antibody responses without known cross-reactivity with other common pneumococcal PS types. *S. pneumoniae* remains a leading cause of invasive diseases such as pneumonia, meningitis, bacteremia, otitis media, and sinusitis worldwide; its capsular polysaccharides are central targets for both diagnostics and vaccine development efforts aimed at reducing disease burden caused by covered serotypes like type 22F.

Other names

Pneumococcal Capsular Polysaccharide Type 22FS. pneumoniae 22F CPSType 22F CPS

Antibody-mediated opsonization and phagocytosis