Streptococcus pneumoniae capsular polysaccharide conjugated to cross-reacting material 197 protein (None standard, often referred to as “pneumococcal polysaccharide-CRM197 conjugate”; CRM197 is sometimes used as an abbreviation for the carrier protein, but no universal abbreviation for the conjugate exists)

Streptococcus pneumoniae capsular polysaccharide conjugated to CRM197 is a glycoconjugate antigen employed in pneumococcal conjugate vaccines (PCVs) to prevent invasive pneumococcal disease. The conjugate comprises purified capsular polysaccharides (antigens from S. pneumoniae, specific for one or more serotypes), covalently linked to CRM197, a non-toxic mutant of diphtheria toxin. This linkage converts the normally T-independent polysaccharide antigen into a T-dependent form, enabling robust immunological memory and higher-affinity antibody responses, especially important in infants and immunosuppressed patients. Multiple serotype-specific conjugates are formulated together to provide broad protection, and the technology is integral to current and next-generation PCVs.

Other names

Pneumococcal conjugate vaccine antigen (varies by serotype)Streptococcus pneumoniae polysaccharide-CRM197 conjugateS. pneumoniae CP-CRM197 conjugate (“CP” stands for capsular polysaccharide)CRM197 conjugate (context-dependent)Prevenar/Prevnar antigen (in the context of commercial vaccines)

Induces humoral immune response through the formation of T-dependent epitopes (CRM197 is a non-toxic mutant of diphtheria toxin). Elicits opsonizing antibodies against S. pneumoniae capsular polysaccharides, facilitating pathogen clearance. Provides immunity and immunological memory for included serotypes.