Neisseria meningitidis group X capsular polysaccharide antigen

The Neisseria meningitidis group X capsular polysaccharide antigen is a surface-expressed homopolysaccharide composed of (α1→4)-linked N-acetylglucosamine (GlcNAc) residues, produced by Neisseria meningitidis serogroup X[7]. It is the principal virulence determinant for serogroup X strains, enabling resistance to host immune responses. The MenX capsule forms the basis for vaccine development, as antibodies targeting the capsule can confer protection via classical complement-mediated killing of the bacterium[1][2]. The capsule is genetically encoded by serogroup-specific genes (notably csxA-csxC in the capsule biosynthesis locus)[2]. MenX-CPS does not cross-react immunologically with other serogroups, allowing for highly specific immune targeting. It is used as an antigen in conjugate vaccines, wherein polysaccharide oligomers (with a minimal epitope of five to six repeating units) are coupled to carrier proteins to elicit robust and long-lasting protective antibody responses[1]. MenX polysaccharide vaccines are particularly relevant for sub-Saharan Africa, where serogroup X outbreaks have occurred and no licensed monovalent or multivalent vaccines existed until very recently[1][2][4][7].

Other names

MenX capsular polysaccharideNeisseria meningitidis serogroup X capsuleMenX-CPS

Vaccines targeting this molecule work by eliciting antibodies against the MenX capsular polysaccharide, which mediate complement-dependent bactericidal activity leading to bacterial clearance and protection against invasive meningococcal disease[1].