Streptococcus pneumoniae serotype 11A capsular polysaccharide

The **Streptococcus pneumoniae serotype 11A capsular polysaccharide** is a complex carbohydrate structure forming the outermost layer of S. pneumoniae serotype 11A.[1][2][3][4][5] It is composed of a linear, tetrasaccharide backbone with a pendant phosphopolyalcohol and sites of O-acetylation that are serotype-defining.[1][3] The capsule is the bacterium’s main virulence determinant, essential for evading host immune defenses by shielding the organism from phagocytosis and complement-mediated killing.[1][5] The structure of the 11A capsule contains four O-acetylation sites, distinguished from closely related variants (11E, 11Av) by the acetylation patterns and function of the wcjE acetyltransferase gene.[2][3][5] Anti-capsular antibodies, elicited naturally or via vaccination, target this polysaccharide and enable immune clearance.[1][2] The capsule is the antigenic target of pneumococcal conjugate and polysaccharide vaccines; its structural features and variability can impact vaccine efficacy and lead to vaccine escape by novel variants.[3][5]

Other names

Pneumococcal serotype 11A capsuleStreptococcus pneumoniae 11A capsuleS. pneumoniae serotype 11A capsular polysaccharidePneumococcus serotype 11A capsular polysaccharide

Induction of antibody-mediated immune response