Neisseria meningitidis Serogroup A Capsular Polysaccharide Antigen (NmSA CPS)

The *Neisseria meningitidis* serogroup A capsular polysaccharide (CPS) antigen is a surface-expressed carbohydrate polymer that serves as the primary virulence factor and immunological target for this bacterial pathogen. It is the basis for serogroup classification, epidemiological tracking, and vaccine development against serogroup A meningococcal disease. The CPS protects bacteria from host immune responses by inhibiting phagocytosis and complement-mediated killing; it is essential for systemic invasive disease. The presence and pattern of O-acetyl groups are crucial for immunogenicity. *N. meningitidis* can undergo "capsule switching," exchanging genetic material to alter its capsule type—potentially evading immunity induced by vaccines targeting specific capsular types.

Other names

Serogroup A CPSN. meningitidis serogroup A capsular polysaccharideMenA CPSGroup A meningococcal polysaccharide

Conjugate vaccines elicit antibody production against the polysaccharide, promoting opsonization and complement-mediated killing of the bacteria. Antibodies block adherence and invasion.