Preparation and the immunogenicity of the conjugate made from group A capsular polysaccharide and group B outer membrane protein complex of Neisseria meningitidis
Objective To prepare the conjugate of ACPS and outer membrane protein complexes (OMPC) of Neisseria meningitidis ( Nm ) and to study its immunogenicity was OMPC purified from the strain 3407 or 542852. Methods OMPC was purified on Sephacryl S 300 HR after the cultural supernatants were precipitated by 70% ammonium sulfate. ACPS was conjugated to OMPC of serogroup B (BOMPC) by carbodiimide mediated condensation. Mice were respectively immunized by the conjugates, unconjugated ACPS, BOMPC and simple mixture of ACPS and BOMPC in the same procedure, then the immunogenicity of the conjugates was determined by ELISA, bactericidal test and Western blotting. Results The immunogenicity of the conjugates was enhanced by 21 to 320 times as large as the unconjugated ACPS or the simple mixture of ACPS and BOMPC. The effect of conjugation of ACPS to the strain 3407 OMPC was better than that to the strain 542852 OMPC. Antisera evoked by BOMPC ACPS conjugates not only possessed a stronger bactericidal activity to the serogroup A strains (29019) and the serogroup B strains (3407, 542852, 29021) but also showed broadly cross reactions to other eight serogroup B strains of different bacterial types. It was primarily found by Western blotting analysis that the sera elicited by the above conjugates obviously reacted with M ?r?42000, 39000 and 26000 proteins in OMPC. Among the reactive bands, the 42kD protein was classⅠOMP. Conclusion The above conjugates not only possessed strong immunogenicity of Nm serogroup A and serogroup B but also enhanced the immunogenicity of ACPS to mice.