Streptococcus pneumoniae Type 3 Capsular Polysaccharide (Type 3 CPS)

The type 3 capsular polysaccharide (CPS) of Streptococcus pneumoniae is a high-molecular-weight, linear polymer that forms the outermost layer of the bacterial cell. This capsule is a major virulence factor, protecting the bacterium from host immune responses by interfering with opsonophagocytic clearance mechanisms. The repeating unit of type 3 CPS consists of a disaccharide: β-D-glucuronic acid (GlcUA) and β-D-glucose (Glc), linked as [→3)-β-D-GlcUA-(1→4)-β-D-Glc-(1→]. Unlike most other S. pneumoniae capsules, which are covalently attached to peptidoglycan, serotype 3 capsule is anchored non-covalently to phosphatidylglycerol in the cell membrane. Purified type 3 capsular polysaccharide antigen is used in approved vaccines for active immunization against diseases caused by S. pneumoniae serotype 3 strains (including pneumonia and bacteremia).

Other names

S. pneumoniae Type 3 CapsulePneumococcal Type 3 Capsular PolysaccharideCPS3

Active immunization; antibody production against type 3 CPS to promote opsonophagocytosis and clearance of S. pneumoniae serotype 3.