Nucleic acid and amino acid sequences of the Omp85 proteins of N. gonorrhoeae and N. meningitidis, and fragments thereof are useful in vaccine compositions, therapeutic compositions and diagnostic compositions for use in the prevention, treatment and diagnosis of non-symptomatic gonococcal infection or symptomatic disease and non-symptomatic meningococcal infection and symptomatic disease. Antibodies are developed to these proteins and also useful in the compositions and methods described herein.