Antibodies to polysialic acid and its N-propyl derivative: binding properties and interaction with human embryonal brain glycopeptides.

There is no efficient vaccine against group B meningococcal meningitis because of tolerance induced by host tissue polysialic acid cross-reacting with the capsular polysaccharide. The specificities of polysialic acid-antibody interactions were studied using a ligand binding assay. Antibodies 735, 20-1, 2-1B, 2-2B, 5E1, and t5E1 and antibodies against N-propionylated group B meningococcal polysaccharide-tetanus toxoid conjugate (NP-4, 106-6) bound polysialylated human embryonal brain glycopeptides but not control glycopeptides or disialosyllactose, whereas antibodies 109-3 and I-627 were more specific for the N-propionylated polysaccharide. Antiganglioside antibodies (KM538, KM641) did not cross-react with polysialic acid. Human class-switched antibodies 5E1 (IgM) and t5E1 (IgG) reacted identically with all compounds tested and no temperature-dependent differences were observed. All anti-polysialosyl antibodies required a polysaccharide chain of 8-10 residues for binding independent of the immunizing antigen, animal species, or immunoglobulin class. The results suggest careful evaluation of polysialic acid cross-reactivity in vaccine development.