Neisseria meningitidis group W-135 polysaccharide capsule (W-135 capsule)

The **Neisseria meningitidis group W-135 polysaccharide capsule** is a high-molecular-weight, surface-expressed polymer composed of partly O-acetylated alternating units of **sialic acid and D-galactose** linked via α-(2→6) and α-(1→4) glycosidic bonds[2][5]. It is the principal virulence factor of W-135 serogroup strains, enabling the bacterium to evade host immune defenses. This polysaccharide capsule forms the basis for defining the W-135 serogroup, serves as a key antigen in both natural immunity and current vaccine formulations, and is genetically encoded by a specific cluster of capsule biosynthesis and export genes (notably synX, synC, synF, and ctrA in the case of W-135)[1][3]. Targeting the W-135 capsule with vaccines prevents invasive disease by promoting opsonization and direct bactericidal activity via complement pathway activation. Capsule switching (genetic exchange leading to change of capsule type) presents a challenge for long-term vaccine efficacy[1].

Other names

W-135 polysaccharide capsuleGroup W-135 capsular polysaccharideNeisseria meningitidis W-135 capsuleCPS (capsular polysaccharide, context-specific)

Induction of protective antibody response (antibodies bind the W-135 capsule, leading to complement-mediated killing and enhanced opsonization)