Specificity of the immune response to the group B polysaccharide of Neisseria meningitidis.

A panel of monoclonal antibodies (mAb) and polyclonal sera of murine, human and equine origin, of IgM isotype and with specificity for Neisseria meningitidis group B polysaccharide, an alpha(2----8)-linked homopolymer of sialic acid, were examined for their antigenic and biological specificities. The nature of the antigenic determinants on B polysaccharide was investigated using a series of N-acyl derivatives of B polysaccharide, two sialic acid polymers containing alpha(2----9)-linkages and a series of polynucleotides. The panel of antibodies recognized an array of unrelated antigenic determinants on the B polysaccharide, despite its structural simplicity, and all but one were highly effective in an in vitro bactericidal assay and/or in an in vivo murine passive protection model. There was no evidence that B polysaccharide induced antibody capable of blocking biological activity (blocking antibody).