Pneumococcal polysaccharide capsule

The **pneumococcal polysaccharide capsule** is a thick, surface-exposed carbohydrate layer that surrounds the cell wall of *Streptococcus pneumoniae*. It is composed of repeating oligosaccharide units that vary among more than 90 serotypes, with each serotype expressing a structurally distinct capsule. The capsule is the primary virulence factor for *S. pneumoniae*, protecting the bacterium from opsonophagocytic killing by interfering with recognition and clearance by the host immune system. Its composition and structure define the immunological serotype, determining susceptibility to vaccine-induced antibodies. The capsule is the principal antigen targeted in current pneumococcal vaccines, which work by inducing serotype-specific antibodies that facilitate bacterial clearance. Serotype shifts and structural variations can reduce vaccine efficacy and complicate epidemiological surveillance[1][3][6].

Other names

Pneumococcal capsular polysaccharideStreptococcus pneumoniae capsuleS. pneumoniae capsuleCapsular polysaccharide (CPS)

Vaccines induce anti-capsular antibodies that promote opsonophagocytosis and clearance of Streptococcus pneumoniae[1][6] Vaccines block capsule-mediated immune evasion