Serogroup A capsular polysaccharide of Neisseria meningitidis (MenA CPS)

The Serogroup A capsular polysaccharide is a critical virulence factor of Neisseria meningitidis, a Gram-negative bacterium responsible for devastating epidemics of meningitis, particularly in sub-Saharan Africa (Stephens et al., 2007). Chemically, it is a unique homopolymer consisting of α-(1→6)-linked N-acetyl-D-mannosamine-1-phosphate (Gudlavalleti et al., 2004). This polysaccharide forms the outermost layer of the pathogen, providing a physical barrier that protects the bacteria from host immune mechanisms such as complement-mediated lysis and opsonophagocytosis (StatPearls, 2023). As a major surface antigen, it is the primary component used in the development of vaccines to prevent meningococcal disease (WHO, 2023). While early vaccines used the pure polysaccharide, modern conjugate vaccines like MenAfriVac link the polysaccharide to a carrier protein to induce a T-cell dependent immune response, providing longer-lasting protection and reducing nasopharyngeal carriage (CDC, 2022).

Other names

Neisseria meningitidis serogroup A polysaccharideMenA polysaccharideα-(1→6)-linked N-acetyl-D-mannosamine-1-phosphateMeningococcal group A capsular polysaccharide

The polysaccharide acts as an antigen that, when introduced via vaccination, stimulates B-cells to produce serogroup-specific antibodies. These antibodies bind to the bacterial capsule, facilitating complement-mediated lysis and opsonophagocytosis (Pollard et al., 2009). In conjugate vaccines, the polysaccharide is linked to a protein carrier, which allows for T-cell involvement, leading to high-affinity antibody production and the establishment of immunological memory (CDC, 2022).