Streptococcus pneumoniae capsular polysaccharide serotype 23A (23A CPS)

Streptococcus pneumoniae capsular polysaccharide serotype 23A (23A CPS) is a complex carbohydrate polymer that forms the outermost protective layer of the 23A serotype of the pneumococcus bacterium [6, 15]. This polysaccharide is a critical virulence factor that enables the pathogen to evade the host's immune system by inhibiting opsonophagocytosis, thereby facilitating colonization and invasive disease [11, 13]. The chemical structure of 23A CPS consists of a repeating oligosaccharide unit with a disaccharide backbone and specific side chains that distinguish it from other serogroup 23 members [16, 21]. Serotype 23A has emerged as a significant cause of invasive pneumococcal disease (IPD) and pneumonia, particularly following the widespread use of vaccines that do not cover this specific serotype [7, 16]. As a therapeutic target, 23A CPS is utilized as an antigen in next-generation pneumococcal conjugate vaccines, such as the 21-valent vaccine (Capvaxive), where it is conjugated to a carrier protein to induce a robust, T-cell-dependent immune response [1, 4]. Vaccination targeting 23A CPS aims to produce serotype-specific opsonophagocytic antibodies that mediate bacterial clearance and provide long-term protection against infections including meningitis, bacteremia, and community-acquired pneumonia [1, 23]. Clinical efficacy is monitored through biomarkers such as opsonophagocytic activity (OPA) titers and serotype-specific IgG levels [4, 23]. Therapeutic challenges include the potential for serotype replacement, where non-vaccine serotypes increase in prevalence following the suppression of targeted strains [6, 13].

Other names

Pneumococcal polysaccharide serotype 23A23A CPSStreptococcus pneumoniae serotype 23A capsular polysaccharideSpn23A CPS

Induction of opsonophagocytic antibodies that mediate bacterial clearance and activation of T-cell-dependent immune responses when conjugated to carrier proteins.