Pneumococcal capsular polysaccharide antigen

Pneumococcal capsular polysaccharide antigens are carbohydrate-based structures forming the outer capsule of *Streptococcus pneumoniae.* More than 90 serotypes exist, each defined by a unique polysaccharide capsule structure. These antigens are the principal virulence factor allowing pneumococci to evade immune clearance. They are the main component and immune target of pneumococcal vaccines such as PPSV23 (polysaccharide vaccine) and PCV13/PCV15/PCV20 (conjugate vaccines), which stimulate production of protective serotype-specific antibodies[2][3][4][5]. In conjugate vaccines, the polysaccharides are linked to a carrier protein to elicit T cell-dependent responses, improving immunogenicity, especially in young children. Measurement of serotype-specific antibody responses is used as a biomarker of protection and to assess immune competence[4][6]. Reduced vaccine efficacy in the very young, elderly, and immunocompromised individuals is a major therapeutic challenge.

Other names

Pneumococcal polysaccharide antigenPneumococcal capsule antigenPneumococcal capsular polysaccharidePneumococcus polysaccharide antigen

Induction of serotype-specific anti-capsular antibodies, conferring immunity by promoting opsonization and phagocytosis of pneumococci[2][3][5]