Binding diversity of monoclonal antibodies to α(2 → 8) polysialic acid conjugated to outer membrane vesicle via adipic acid dihydrazide

Abstract

Murine monoclonal antibodies (mAbs) were generated using group B Neisseria meningitidis and Escherichia coli K1 polysaccharides (PSs) conjugated to outer membrane vesicle (OMV) via adipic acid dihydrazide, and were used to identify the immunodeterminants expressed on these capsular PSs. Ten mAbs representative of IgM and all subclasses of IgG were obtained which recognized diverse immunodeterminants on α(2 → 8) polysialic acid (PSA). The specificity of mAbs to different antigenic determinants was assessed by their differential binding to PSA attached to a solid phase by different methods and confirmed by absorption studies. Two mAbs from the E. coli K1 fusion were directed to the O-acetyl epitope and the rest reacted with both the PSs only when attached to a solid phase by certain means. The methods by which PSA was coated on the solid phase had an impact on the epitope expression and binding pattern. At the concentrations used, the O-acetyl-specific mAbs, IgG1 and IgG3 mAbs were not bactericidal against group B N. meningitidis, whereas other mAbs were. The conjugates B and K1 PSs present to the murine immune system different antigenic determinants, some of which elicit bactericidal antibodies.