Neisseria meningitidis capsular polysaccharide, group A (NmA-CPS)

Neisseria meningitidis capsular polysaccharide, group A (NmA-CPS) is a homopolymer of O-acetylated (α1→6)-linked N-acetyl-D-mannosamine (ManNAc), forming a negatively charged capsule around *N. meningitidis* group A cells. The capsule is the primary immunogenic component targeted in group A meningococcal vaccines. Its O-acetylation (especially at C3 and C4 positions) is critical for inducing functional immune responses, and is required for the effectiveness of conjugate vaccines. Genetic loci encoding biosynthesis and transport (notably, region A of the cps locus) are highly conserved among NmA strains. Capsule modification, switching, and phase variation contribute to immune evasion and epidemiologic diversity. Detection and vaccine-mediated neutralization of NmA-CPS is central to the control of meningococcal disease in endemic regions.

Other names

Group A polysaccharide capsuleNmA capsuleMeningococcus group A capsuleNeisseria meningitidis serogroup A capsular polysaccharide

Conjugate vaccines elicit an adaptive immune response against the capsule, inducing protective antibodies that facilitate opsonization and complement-mediated killing of the bacterium. Direct targeting clears group A meningococcus and prevents colonization and invasive disease.