Capsular polysaccharide of Neisseria meningitidis

The capsular polysaccharide of *Neisseria meningitidis* is a high-molecular-weight carbohydrate polymer that forms an external layer surrounding the bacterium. It is the principal virulence factor enabling *N. meningitidis* to evade host immune responses by inhibiting phagocytosis and resisting complement-mediated lysis. There are at least thirteen distinct types (“serogroups”) based on differences in their capsular polysaccharide structures; these include serogroups A, B, C, W, X, Y among others. The chemical composition varies between serogroups—for example, serogroup A’s capsule consists of O-acetylated N-acetyl-D-mannosamine phosphate repeats while B/C/Y/W capsules contain sialic acid polymers with different linkages[1][5]. Genes responsible for biosynthesis and export are clustered at the chromosomal cps locus. The presence or absence—and structural variation—of this capsule determines both pathogenic potential and immunological identity. Most effective vaccines against *N. meningitidis* target these capsular antigens directly or as part of conjugate formulations that enhance immunogenicity especially in young children[2]. Loss or alteration (“switching”) of the capsule can lead to immune escape but also affects bacterial colonization dynamics. In summary, this molecule is not a classical “receptor” but rather a critical bacterial surface antigen targeted by current therapeutics—primarily vaccines—to prevent life-threatening infections such as bacterial meningitis and sepsis caused by *Neisseria meningitidis*[1][2][5].

Other names

Meningococcal capsular polysaccharideNeisseria meningitidis capsuleMeningococcal capsulePolysaccharide capsule of Neisseria meningitidis

Induction of protective antibodies via vaccination targeting the capsular polysaccharides; these antibodies promote opsonization and complement-mediated killing of the bacteria[2]