Streptococcus pneumoniae capsular polysaccharide serotype 22F (Pn22F)

Streptococcus pneumoniae capsular polysaccharide serotype 22F is a complex carbohydrate polymer that encapsulates the 22F serotype of the Gram-positive bacterium Streptococcus pneumoniae (CDC, 2022). This capsule serves as a primary virulence factor by shielding the pathogen from the host's innate immune system, specifically preventing opsonization and subsequent phagocytosis (PubMed, PMID: 31235530). Serotype 22F has gained clinical prominence as a leading cause of invasive pneumococcal disease (IPD), including pneumonia and meningitis, particularly in the era following the introduction of PCV7 and PCV13 (StatPearls, 2023). To address this, the 22F polysaccharide is incorporated as an antigen in modern multi-valent vaccines such as PCV15 (Vaxneuvance), PCV20 (Prevnar 20), and PPSV23 (Pneumovax 23) (FDA, 2021). Upon administration, these vaccines stimulate the production of specific antibodies that recognize the 22F structure, enabling the immune system to effectively target and eliminate the bacteria during an infection (PubMed, PMID: 34103154). The inclusion of this serotype in conjugate vaccines aims to provide broader protection against the shifting epidemiology of pneumococcal infections. Clinical efficacy is typically measured by the induction of functional antibodies capable of killing the bacteria in opsonophagocytic assays.

Other names

Pneumococcal polysaccharide serotype 22FSpn22F polysaccharide22F capsular polysaccharide22F CPS

Induction of serotype-specific humoral immune response and production of opsonophagocytic antibodies that facilitate bacterial clearance.