Neisseria meningitidis capsular polysaccharide antigen (NmCPS)

The Neisseria meningitidis capsular polysaccharide antigen is a high molecular weight surface polysaccharide forming the capsule of Neisseria meningitidis, a major human pathogen causing meningococcal meningitis and sepsis. The capsule’s chemical composition defines the bacterium’s serogroup (A, B, C, W, X, Y, etc.), with group-specific repeating sugar units and modifications such as O-acetylation that critically affect its antigenicity and immunoprotection. The capsular antigen is the main virulence determinant, protecting bacteria from host immune responses—especially complement-mediated killing and phagocytosis—and is the key component of most effective vaccines. For group A, O-acetylation is mandatory for immunogenicity and vaccine efficacy. Vaccine-induced and natural anti-capsular antibodies promote bactericidal activity, making this polysaccharide a classical and successful bacterial therapeutic target. Capsule switching (by horizontal gene transfer) allows immune escape and is a significant challenge for vaccine longevity and effectiveness.

Other names

Neisseria meningitidis capsuleMeningococcal capsular polysaccharideMeningococcal capsuleNm polysaccharide antigenGroup A, B, C, W, Y, X capsular antigen (serogroup specific forms)MenA/B/C/W/Y/X capsule (serogroup specific, e.g., "MenA capsule")

Induction of protective antibody production (antibodies to the CPS mediate complement-dependent bactericidal activity, enabling rapid clearance of the bacteria by the immune system); Opsonization enhancement (facilitates phagocytosis by immune cells after antibody binding); Blocking of capsule biosynthesis/structure (experimental antimicrobials)