`NMB1870' is a known surface protein in expressedacross all serogroups. It has three distinct families. Serum raised againsta given family is bactericidal within the same family, but is not active againststrains which express one of the other two families intra-familybut not inter-family cross-protection. The inventors have found that NMB1870can be divided into domains, and that not all domains are required for antigenicity.Antigenic domains can be taken from each of the three NMB1870 families and expressedas a single polypeptide chain. The inventors have also found that NMB1870 exposessome of its epitopes in surface loops situated between alpha helices, and thatsubstitution of loop epitopes from one family into the loop position in anotherfamily allows chimeric NMB1870 to be produced with multi-family antigenicity.Thus chimeric NMB1870 proteins are provided that comprise portions of NMB1870from different families.
