Capsular polysaccharide antigen of Neisseria meningitidis serogroup A (None commonly standardized; sometimes abbreviated as NmA-CPS, NmC-CPS, NmW-CPS, NmY-CPS, depending on serogroup, but this is not a unified abbreviation for all)

Capsular polysaccharide antigens of Neisseria meningitidis serogroups A, C, W, and Y are high-molecular-weight carbohydrate polymers expressed on the surface of the bacterium Neisseria meningitidis. They are the major virulence determinants, enabling the pathogen to evade the host immune system by inhibiting complement-mediated lysis and phagocytosis, and form the basis for both clinical serogroup classification and the development of effective polysaccharide and conjugate vaccines. Each serogroup expresses a chemically distinct polysaccharide: serogroups C, W, and Y capsules contain sialic acid, whereas serogroup A contains alternating N-acetylmannosamine and phosphate, with O-acetylation crucial for immunogenicity. The presence and specific structure of these capsular polysaccharides are essential for the bacterium's ability to cause invasive disease and for vaccine efficacy, but also render the bacterium susceptible to immune detection when properly targeted by vaccination. Capsule switching, whereby bacteria alter their capsular polysaccharide via genetic recombination, is a recognized mechanism of immune evasion and complicates disease surveillance and vaccine design.

Other names

Meningococcal capsular polysaccharide (serogroup A, C, W, Y)Neisseria meningitidis capsular polysaccharide antigen (serogroup A, C, W, Y)CPS (with serogroup indicated, e.g., NmA-CPS, NmC-CPS)Meningococcal capsule antigen

Induction of protective, serogroup-specific antibody response against the capsular polysaccharide to facilitate bacterial clearance by the host immune system Blocking of complement resistance by bacterial capsule Conjugation to carrier proteins to induce T-cell dependent immune response for long-term memory