Streptococcus pneumoniae polysaccharide serotype 22F (PPS22F)

Streptococcus pneumoniae polysaccharide serotype 22F is the capsular polysaccharide (CPS) that forms the outermost protective layer of the serotype 22F strain of pneumococcus [1, 8]. This polysaccharide acts as a critical virulence factor by forming a physical barrier that prevents opsonophagocytic clearance by the host's immune system, specifically resisting uptake by neutrophils [8, 14, 15]. Serotype 22F has emerged as a significant cause of invasive pneumococcal disease (IPD) in the post-PCV13 era, as it was not included in earlier conjugate vaccine formulations [11, 14, 16]. It is currently a key therapeutic target in newer multivalent vaccines, including PCV15, PCV20, and PCV21, as well as the 23-valent polysaccharide vaccine (PPSV23) [4, 5, 6]. In conjugate vaccines, the 22F polysaccharide is chemically linked to a carrier protein, such as CRM197, to stimulate a T-cell-dependent immune response that provides long-term protection through memory B-cells [1, 9, 17]. Therapeutic efficacy is monitored through the measurement of serotype-specific IgG antibodies and functional opsonophagocytic activity (OPA) [4, 9, 10].

Other names

Pneumococcal polysaccharide serotype 22FS. pneumoniae serotype 22F capsuleSerotype 22F capsular polysaccharidePPS22F

Induction of active immunity through the production of serotype-specific opsonophagocytic antibodies