Streptococcus pneumoniae serotype 1 capsular polysaccharide (Spn1 CPS) (Spn1 CPS)

The capsular polysaccharide of Streptococcus pneumoniae serotype 1 is a complex carbohydrate structure that encapsulates the bacterium, serving as its primary virulence factor by inhibiting opsonophagocytosis (1). Serotype 1 is a major cause of invasive pneumococcal disease (IPD) globally, often associated with pneumonia, bacteremia, and meningitis (2). Unlike many other pneumococcal polysaccharides, the serotype 1 capsule is zwitterionic, containing both galacturonic acid and amino sugars, which enables it to stimulate T-cell-dependent immune responses when presented by MHC class II molecules (3, 4). This property is exploited in pneumococcal conjugate vaccines (PCVs), such as PCV13, PCV15, and PCV20, where the polysaccharide is chemically linked to a carrier protein like CRM197 to enhance immunogenicity and induce long-term memory (5, 6). These vaccines elicit serotype-specific antibodies that facilitate the clearance of the pathogen through opsonophagocytic killing (7). Therapeutic challenges include serotype replacement, where non-vaccine serotypes increase in prevalence following widespread vaccination, and the need for broad coverage across diverse geographic regions (8).

Other names

Pneumococcal polysaccharide serotype 1S. pneumoniae type 1 capsular antigenCPS1Type 1 pneumococcal polysaccharide

Induction of serotype-specific opsonophagocytic antibodies