NMB1870 is a protein in Neisseria meningitidis. Three families of NMB1870 are known. To increase the ability of a NMB1870 protein to elicit antibodies that are cross-reactive between the families, NMB1870 is engineered. Sequences can be substituted from one NMB1870 family into the corresponding position in another family. Proteins of NMB1870 sequences from different families can be joined to each other.