Streptococcus pneumoniae capsular polysaccharides and proteins (S. pneumoniae antigens)

Streptococcus pneumoniae capsular polysaccharides and proteins are the primary antigenic targets for vaccines designed to prevent pneumococcal infections. The polysaccharide capsule is the most important virulence factor of S. pneumoniae, shielding the bacterium from the host's immune system by inhibiting opsonophagocytosis [CDC, 2022; WHO, 2021]. Because there are over 100 known serotypes based on capsule structure, current vaccines target the most prevalent and virulent ones. Polysaccharide-protein conjugate vaccines (PCVs) link these sugars to carrier proteins to induce a T-cell dependent immune response, which is effective in infants and provides long-term memory [Paton & Trappetti, 2019]. In addition to polysaccharides, highly conserved surface proteins such as Pneumococcal surface protein A (PspA) and the toxin Pneumolysin (Ply) are being investigated as vaccine candidates to provide broader, serotype-independent protection [Pichichero, 2017]. These targets are critical in the clinical management of pneumonia, meningitis, and bacteremia worldwide.

Other names

Pneumococcal capsular polysaccharidesPneumococcal surface proteinsCPSPspAPspCPneumolysinPhtD

Induction of humoral and cellular immune responses; polysaccharides stimulate B-cells to produce serotype-specific IgG antibodies that facilitate opsonophagocytosis, while conjugate vaccines recruit T-cell help to establish immunological memory.