Antigenicity of meningococcal group B oligo- and polysaccharides of defined chain length

Meningococcal group B oligosaccharides of (2→8)α-linked sialic acid with chain lengths up to 28 residues were poorly antigenic in comparison with the native purified B polysaccharide when tested either with a new and sensitive group B monoclonal latex agglutination (LA) reagent or by a solid-phase radioimmune inhibition assay. Loss of antigenicity of the B polysaccharide by the LA test also occurred upon removal of N-acetyl groups (i.e. NHCO.CH3 →NH2) or by replacement of N-acetyl with N-propionyl groups (i.e. NHCO.CH3 → NHCO.CH2CH3). The B polysaccharide, however, retains antigenicity upon removal of the fatty acid esters of the phospholipid moiety, which occur at the reducing end of the polymer chain and are implicated in aggregation of chains by micellar formation.