Group C Polysaccharide from Neisseria meningitidis contains a terminal lipid tail which is known to generate high molecular weight polysaccharide by aggregation. Treatment of the polysaccharide with phospholipase A2removes the lipid tail. We were interested in understanding the role of the lipid tail in antigen -antibody interactions of Group C polysaccharide (GCPS) as well as its involvement in attachment to the membrane. When GCPS was chemically de-O-acetylated, it did not bind to Immulon 1 plates. Treatment of GCPS with Phospholipase A2 had the same effect on binding to Immulon 1 microtitre plates. Removal of the lipid tail also eliminates a high molecular weight fraction as seen on a molecular sizing column. When Phospholipase treated GCPS was used as an inhibitor in a competetive ELISA, it competed effectively with GCPS to bind to the antisera. The presence of the lipid tail may be important in association of the polysaccharide on the surface of the outer membrane, and is important for binding to the ELISA plate although it has no effect in binding to the antibody. Experiments are under way to study the role of the lipid tail in association of GCPS to outer membrane vesicles and the extent of association with and without phospholipase treatment.
