Streptococcus pneumoniae Capsule (Type-Specific)

The capsule of *Streptococcus pneumoniae* is a polysaccharide layer that forms the dominant surface structure of the bacterium. It is essential for virulence, primarily by protecting the organism from host immune responses, especially opsonophagocytic clearance mechanisms. The capsule is highly variable, with over 98 recognized serotypes (and new types still being discovered), each defined by its unique polysaccharide composition and structure. The capsule serves as a target for serotyping assays, vaccine development and therapeutic interventions. Vaccines targeting capsular polysaccharides (such as PCV13 or PPV23) induce type-specific antibodies that promote opsonization and killing of encapsulated bacteria but only cover selected prevalent or invasive serotypes.

Other names

Pneumococcal capsuleStreptococcus pneumoniae capsular polysaccharideCapsular polysaccharide (CPS)Pneumococcal capsular polysaccharideType-specific capsule

Induction of type-specific antibodies leading to complement activation, opsonization, and killing of bacteria; Capsule degradation