The DNA of the invention are characterised in that they concern the whole or part of genes, with their reading frame, to be found in Neisseria meningitidis, but not in Neisseria gonorrhoeae, or in Neisseria lactamica except the genes involved in the biosynthesis of the polysaccharide capsule, frp A, frp C, opc, por A, rotamase the sequence IC1106, IgA protease, pilline, pilC, transferrin binding proteins and opacity proteins. The invention also concerns the polypeptides corresponding to these DNA and the antibodies directed against these polypeptides. It is applicable in the prevention and the detection of meningococcus induced infections and meningitis.