High affinity binding of long-chain polysialic acid to antibody, and modulation by divalent cations and polyamines

Abstract

Long-chain polysialic acid (PSA) is expressed on the vertebrate neural cell adhesion molecule (NCAM) during neuronal plasticity. Its structural similarity to the capsular PSAs of some pathogenic bacteria has hampered the development of polysaccharide vaccines against meningitis. The antibodies formed during immunization require a long epitope for binding, and cross-react with host tissue PSA. The nature of the epitope and possible external effectors involved are still unclear. We have evaluated the interaction of PSA with its antibody mAb735 by surface plasmon resonance. The influences of PSA chain length, pH, temperature, ionic environment, and polyamines were also determined.The antibody binding affinity was found to dramatically increase with PSA chain length. A sub-nanomolar dissociation constant (K D = 8.5 × 10 −10 M) was obtained for the binding of very long chain native MenB polysaccharides (∼200 Neu5Ac-residues). Colominic acid from Escherichia coli K1 (∼100 residues) and shorter polymers exhibited progressively weaker affinities. The antibody also bound tightly (K D ∼ 5 × 10 −9 M) to polysialylated glycopeptides from human embryonal brain. The effects of pH and ionic strength suggested that the interaction is largely electrostatic. Ca 2+ and Mn 2+ ions promoted the observed surface plasmon resonance response in a concentration dependent fashion. Spermine increased the response in a similar way. Our results suggest that divalent cations and polyamines may play significant role in the regulation of the PSA epitope presentation in vivo.

Inadequacy of Colominic Acid as an Absorbent Intended To Facilitate Use of Complement-Preserved Baby Rabbit Serum in theNeisseria meningitidisSerogroup B Serum Bactericidal Antibody Assay

“…Incubation at 4°C was previously demonstrated to increase binding of anticapsular antibody to MenB polysaccharide (1,30). However, we demonstrated that temperature did not affect inhibition with colominic acid (data not presented), in agreement with previous reports of Hayrinen and coworkers (11,12,13). Increased incubation periods and agitation conditions were also investigated but, again, showed no effect on inhibition or SBA titers (data not presented).…”

Proteolytic Release of the Intramolecular Chaperone Domain Confers Processivity to Endosialidase F

“…Microtiter plates were coated with polySia containing a lipid anchor (20) to allow efficient attachment of polySia to the solid phase (14). After endoNF digestion and removal of the enzyme, remaining substrate was detected with the polySia-specific monoclonal antibody 735, which binds to ␣2,8-linked polySia Ն8 residues (22,24,25).…”

Impact of the Polysialyltransferases ST8SiaII and ST8SiaIV on Polysialic Acid Synthesis during Postnatal Mouse Brain Development

“…3). Staining was performed either with mAb 735 (top panel) specific for ␣2,8-linked polySia with DP Ն 8 (39,44) or mAb H28 (middle and bottom panels) directed against a protein epitope common to all murine NCAM isoforms (38). Because each polySia chain provides multiple binding sites for an antipolySia antibody, much stronger signals were obtained with mAb 735.…”