ABSTRACT
Unlike Neisseria meningitidis groups A, C, Y and W135, the group B capsular polysaccharide has been shown to be chemically and immunologically identical to the capsular polysaccharide of Escherichia coli K1. Both components are sialic acid homopolymers and are poorly immunogenic. Nevertheless, due to the high incidence of Neisseria meningitidis group B meningitis in the population of the State of São Paulo, preparing antiserum to this serogroup for diagnostic purposes has become a matter of high priority. Of the many immunization schemes proposed, intravenous inoculation of whole bacteria previously inactivated with formaldehyde and simultaneous intradermal inoculation with a mixture of the bacterial polysaccharide fraction and whole bacteria in complete Freund;s adjuvant have produced the best results. The antiserum was treated with immunoadsorbents prepared with aluminum chloride and protein and/or polysaccharide antigens from each of the following heterologous bacteria: Haemophilus influenzae type b, Streptococcus pneumoniae, Escherichia coli other than K1, and Staphylococcus aureus, in order to eliminate cross-reactivity. For quality control analysis, the antiserum was assessed by the immunodiffusion, counterimmunoelectrophoresis, dot-ELISA, and immuno-blot techniques against homologous antigens. Specificity was obtained after treating the antiserum with Haemophilus influenzae type b polysaccharide immunosorbent.