Streptococcus pneumoniae capsular polysaccharide serotype 1 (CPS1)

The Streptococcus pneumoniae capsular polysaccharide serotype 1 (CPS1) is a high-molecular-weight surface polymer and dominant virulence factor that shields the bacterium from host opsonophagocytic clearance by immune cells, enabling nasopharyngeal colonization, biofilm formation, and invasive infections like pneumonia and sepsis. Synthesized via the Wzx/Wzy-dependent pathway, CPS1 assembly begins with sugar-1-phosphate transfer to undecaprenyl-phosphate lipid carriers in the cytoplasm, followed by glycosyltransferase addition of repeat units, flippase translocation, polymerization, and covalent 1,6-glycosidic linkage to cell wall peptidoglycan GlcNAc. This serotype is prevalent in global invasive pneumococcal disease outbreaks, particularly among children and the elderly. CPS1 serves as the primary target for pneumococcal vaccines, including PPV23 and conjugates like PCV13, which elicit serotype-specific antibodies for opsonophagocytosis. Vaccine efficacy is limited to included serotypes, driving ongoing surveillance for capsule diversity across 98+ types.

Other names

pneumococcal capsular polysaccharide serotype 1Streptococcus pneumoniae type 1 capsuleserotype 1 CPS

Induction of serotype-specific opsonophagocytic antibodies for bacterial clearance