22F capsular polysaccharide epitope of Streptococcus pneumoniae (22F CPS epitope)

The 22F capsular polysaccharide epitope of Streptococcus pneumoniae is a serotype-specific carbohydrate structure forming part of the bacterium’s outer capsule. This capsule contributes to virulence by protecting the bacterium against host immune clearance mechanisms, notably by inhibiting opsonophagocytosis. The epitope is a molecular site within the 22F capsule recognized by antibodies and thus serves as a critical antigenic determinant for both natural immune responses and for the effectiveness of polysaccharide and conjugate vaccines. Serotype 22F, along with other non-PCV13 serotypes, has increased in prevalence following the adoption of vaccines targeting only a subset of pneumococcal serotypes. The structure of the 22F capsule is based on a repeating oligosaccharide unit, which can be chemically characterized and is immunologically distinct from other serotypes, enabling specific detection and targeting. Its biological significance lies in both epidemiological tracking and as a direct target of vaccine-induced protective antibodies, making it a current focus for expanded pneumococcal vaccine formulations.

Other names

Serotype 22F capsular polysaccharideS. pneumoniae type 22F capsulePneumococcal serotype 22F capsule22F epitope

Vaccines: Induction of anti-22F capsular polysaccharide antibodies, leading to opsonophagocytic killing of S. pneumoniae expressing the 22F capsule