Streptococcus pneumoniae capsular polysaccharide type 11a (CPS 11A)

Streptococcus pneumoniae capsular polysaccharide type 11a (CPS 11A) is a complex carbohydrate polymer that encapsulates the serotype 11A pneumococcus, serving as a primary virulence factor by shielding the bacterium from the host's immune system [2, 4]. It functions primarily as an anti-phagocytic barrier, inhibiting the deposition of complement components and preventing recognition by phagocytic cells [2, 11]. Structurally, CPS 11A consists of a tetrasaccharide repeat unit with a unique acetylglycerol-phosphate moiety, where O-acetylation plays a critical role in its antigenic identity and interaction with the immune system [5, 8]. This polysaccharide is a key therapeutic target for preventing invasive pneumococcal diseases, including pneumonia, meningitis, and bacteremia [1, 10]. It is incorporated as an antigen in several widely used vaccines, such as the 23-valent polysaccharide vaccine (PPSV23) and the 20-valent and 21-valent conjugate vaccines (PCV20 and PCV21) [12, 15]. Upon vaccination, CPS 11A stimulates the production of serotype-specific IgG antibodies that opsonize the bacteria, thereby enabling effective clearance through opsonophagocytosis [11, 17].

Other names

Serotype 11A capsular polysaccharidePneumococcal polysaccharide serotype 11ACPS 11A11A antigenS. pneumoniae serotype 11A capsule

Stimulates active immunity through the production of serotype-specific antibodies that facilitate opsonophagocytosis and clearance of the pathogen.