Staphylococcus aureus capsular polysaccharide serotype 5 conjugated to CRM197 (CP5-CRM197)

Staphylococcus aureus capsular polysaccharide serotype 5 (CP5) conjugated to CRM197 is a glycoconjugate vaccine component designed to prevent invasive S. aureus infections (PMID: 32163061). CP5 is one of the two most prevalent capsular serotypes found in clinical isolates, helping the bacteria evade the host immune system by resisting opsonophagocytosis (PMID: 12117937). By conjugating the CP5 polysaccharide to CRM197—a non-toxic mutant of the diphtheria toxin—the immune system can mount a T-cell dependent response (PMID: 21939714). This conversion from a T-independent to a T-dependent antigen is necessary for long-term immunological memory and high-affinity antibody production. These specific IgG antibodies bind to the bacterial capsule, facilitating the destruction of the pathogen by neutrophils through opsonophagocytic killing. This conjugate was a key component of experimental vaccines like Pfizer's SA4Ag (PF-06290510), which aimed to reduce the incidence of post-operative S. aureus infections. Despite showing robust immunogenicity in early phases, vaccines incorporating this conjugate have faced challenges in demonstrating clinical efficacy in large-scale human trials (PMID: 32163061). The failure of these vaccines highlights the complexity of S. aureus pathogenesis and the potential insufficiency of targeting the capsule alone for protection.

Other names

Type 5 capsular polysaccharide-CRM197 conjugateS. aureus CP5-CRM197Staphylococcus aureus CP5-CRM197 glycoconjugateCP5-CRM197 vaccine component

Induction of capsular-specific IgG antibodies that promote opsonophagocytic killing of Staphylococcus aureus by host phagocytes.