Neisseria meningitidis serogroup A capsular polysaccharide–protein conjugate (MenA conjugate)

The Neisseria meningitidis serogroup A capsular polysaccharide–protein conjugate is a vaccine antigen designed to provide immunity against invasive meningococcal disease caused by serogroup A bacteria. The primary component is the capsular polysaccharide, a polymer of N-acetylmannosamine-1-phosphate, which is a critical virulence factor that protects the bacteria from host immune clearance (PubMed: 22136647). To overcome the limitations of pure polysaccharide vaccines—such as poor immunogenicity in infants and lack of immunological memory—the polysaccharide is covalently linked to a carrier protein like tetanus toxoid (WHO: Meningococcal vaccines). This conjugation converts the immune response from T-cell independent to T-cell dependent, allowing for the activation of T-helper cells and the subsequent production of high-affinity IgG antibodies and memory B-cells (StatPearls: Meningococcal Vaccine). These antibodies are measured via serum bactericidal assays, which correlate with clinical protection by facilitating complement-mediated killing of the pathogen (PubMed: 24144460). This target has been instrumental in nearly eliminating serogroup A meningitis in the African meningitis belt through mass vaccination campaigns (CDC: Meningococcal Disease).

Other names

Meningococcal group A conjugateMenA-TTMenA-CRM197Neisseria meningitidis serogroup A polysaccharideGroup A meningococcal conjugate

Induces a T-cell dependent immune response by presenting bacterial polysaccharide antigens to B-cells, which then process the conjugated carrier protein and present peptides to T-helper cells. This interaction leads to B-cell maturation, isotype switching to high-affinity IgG, and the development of long-term immunological memory.