Neisseria meningitidis group A polysaccharide capsule (NmA-CPS)

The Neisseria meningitidis group A polysaccharide capsule is a large, unbranched bacterial capsular polysaccharide composed of O-acetylated N-acetylmannosamine phosphate repeating units, linked by α-(1→6) phosphodiester bonds[5]. This capsule is a key virulence determinant enabling the bacterium to evade the human immune system and cause invasive diseases such as meningitis and sepsis[3][2]. The capsule is encoded by the cps locus, with the group A-specific biosynthetic genes (csaA-csaD) responsible for its unique structure[2][3]. O-acetylation at positions C3 and C4 of the N-acetylmannosamine units is essential for the induction of a functional immune response, and its presence is mandatory in all effective vaccine formulations targeting serogroup A[1]. The capsule serves as the principal antigenic component in group A meningococcal polysaccharide and conjugate vaccines, which function by eliciting protective antibodies and enabling immune clearance of the pathogen[1][5]. The capsule's structure and regulation are critical to the pathogenesis, immunodiagnostics, and successful control of meningococcal group A disease[2][3][6].

Other names

NmA capsuleGroup A capsuleMeningococcal group A capsular polysaccharideNmA-CPS

Induces immune response by acting as a T-cell independent antigen (native polysaccharide vaccine)[3]. Induces immune response via T-cell dependent mechanisms when conjugated to a carrier protein (conjugate vaccine)[5]. Promotes opsonization and complement-mediated killing after antibody development[1].