Embryonic Neural Cell Adhesion Molecule in Cerebrospinal Fluid of Younger Children: Age‐Dependent Decrease During the First Year

Abstract

Poly-.alpha.-2,8-N-acetylneuraminic acid (poly-.alpha.-2,8-NeuAc) is developmentally expressed in neural tissue of higher animals, where it is covalently attached to the neural cell adhesion molecule (NCAM), a large integral membrane glycoprotein mediating cell-cell adhesion during neuronal development. NCAM exists in several molecular forms, of which only embryonic NCAM carries lengthy chains (n > 5) of poly-.alpha.-2,8-NeuAc. Chemically identical poly-.alpha.-2,8-NeuAc of bacterial origin is an important virulence factor in infections caused by Neisseria meningitidis group B and Escherichia coli K1, the predominant pathogens of bacterial meningitis. A quantitative enzyme-linked immunoassay was developed using monoclonal antibody (MAb) 735, an MAb specifically recognizing poly-.alpha.-2,8-NeuAc, and applied to CSF specimens from younger children. Poly-.alpha.-2,8-NeuAc contents were within the range of 20-0.2 .mu.g/ml, decreasing from day 1 to day 300. Immunoprecipitation, immunoblot with a rabbit anti-mouse NCAM serum recognizing the protein part of human NCAM by cross-reactivity, affinity enrichment using immobilized MAb 735, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that poly-.alpha.-2,8-NeuAc in CSF is bound to human NCAM, probably NCAM-120.