Serotype 3 capsular polysaccharide antigen of Streptococcus pneumoniae

The **serotype 3 capsular polysaccharide antigen of Streptococcus pneumoniae** is a bacterial surface polysaccharide composed of a simple disaccharide repeat unit: alternating glucose and glucuronic acid residues. It is synthesized via a processive synthase-dependent pathway encoded by the cps3/cap3 locus, consisting of genes that direct polysaccharide assembly and export[1][5][9]. This capsule is the dominant virulence factor for serotype 3 strains, conferring protection against host immune responses, including opsonophagocytic killing and complement activation, and is directly responsible for the ability of these bacteria to cause severe invasive diseases like pneumonia, meningitis, and sepsis[6]. The serotype 3 capsular polysaccharide antigen is both a key target and a significant challenge for pneumococcal vaccine development. While current vaccines include this antigen, serotype 3 strains demonstrate significant resistance to antibody-mediated clearance, resulting in persistent disease burden and high mortality rates associated with serotype 3 infections[5][10].

Other names

Serotype 3 capsular polysaccharideStreptococcus pneumoniae serotype 3 capsuleType 3 pneumococcal capsuleSerotype 3 CPS

Induction of opsonophagocytic antibodies that target the capsule for phagocytosis[3][5] Activation of adaptive immune response against serotype 3 CPS[3][7]