Physicochemical properties of Neisseria meningitidis group X polysaccharide antigen.

Neisseria meningitidis group X occurs in human carrier populations and is rarely implicated in serious disease. This organism possesses a capsular group antigen which is an acidic polysaccharide. It is composed of the amino sugars, glucosamine, glucosamine-6-phosphate, galactosamine, and the simple hexose, glucose. The group X capsular antigen has an S(20,w) (0) of 3.6, and the acidic nature of the polysaccharide is reflected in an isoelectric point of 3.65. The meningococcal A, B, C, and Y polysaccharide group antigens are also composed primarily of amino sugars. The chemical composition of the group X antigen most closely resembles the capsular antigen of N. meningitidis group Y, which is also predominately a carrier organism.