Streptococcus pneumoniae type 23F capsular polysaccharide and CRM197 carrier protein

Streptococcus pneumoniae type 23F capsular polysaccharide is a serotype-specific surface carbohydrate that forms the main component of the pneumococcal capsule, a critical virulence factor protecting the bacterium from host immune recognition and clearance[1][4][7][10]. In conjugate vaccines, this polysaccharide is covalently linked to CRM197, a genetically detoxified, non-toxic mutant of diphtheria toxin that serves as a protein carrier to enhance the T-cell–dependent immunogenicity of the polysaccharide, particularly in infants and young children who do not mount effective antibody responses to polysaccharide antigens alone[2][3][5][8]. The 23F-CRM197 conjugate is widely used in pneumococcal conjugate vaccines, which are effective in preventing invasive pneumococcal disease caused by serotype 23F and other covered serotypes. CRM197 differs from native diphtheria toxin by a single amino acid substitution (Gly52Glu), which abolishes its enzymatic toxicity while retaining structural integrity necessary for immunological function[2][8].

Other names

S. pneumoniae 23F polysaccharide-CRM197 conjugatePneumococcal 23F-CRM197 conjugateType 23F capsule-CRM197

Induces a T-cell–dependent immune response through presentation of capsular polysaccharide antigen to immune system via CRM197 carrier-mediated processing, resulting in production of high-affinity, opsonizing, and protective antibodies[2][3][7][8]. Enables immunological memory and effective response in infants and young children, who respond poorly to unconjugated polysaccharides.