Serotype 6A capsular polysaccharide antigen of Streptococcus pneumoniae (Serotype 6A polysaccharide)

Serotype 6A polysaccharide antigen is a complex carbohydrate structure forming the capsule of Streptococcus pneumoniae serotype 6A. It consists of repeating units containing galactose, glucose, rhamnose, and ribitol linked via phosphate bridges, with the galactose-glucose-rhamnose-ribitol-phosphate motif distinguishing 6A among serogroup 6. The capsular polysaccharide is a critical virulence factor, protecting bacteria from immune detection and clearance, and is the primary antigenic determinant used for serotyping and vaccine development. Vaccines containing the 6A polysaccharide, conjugated to carrier proteins, elicit protective, serotype-specific immunity, significantly reducing disease burden from 6A strains. This antigen is included in leading pneumococcal conjugate vaccines and is a frequent subject in diagnostic serotyping and immunological studies. Its molecular structure is similar to other serogroup 6 polysaccharides but can be distinguished by chemical analysis and monoclonal antibody binding.

Other names

Serotype 6A CPSStreptococcus pneumoniae serotype 6A capsule6A capsular antigenPS 6A

Induction of serotype-specific immunity (via vaccine: conjugation of 6A polysaccharide to carrier protein stimulates adaptive immune response); Opsonization and enhanced phagocytosis (induced by antibodies against the 6A antigen)