Methods and compositions for the treatment of microbial infection, and in particular meningococcal disease, comprise a commensal Neisseria or an extract of a commensal Neisseria. Further methods and compositions comprise conimensal Neisseria which express genes from virulent strains of Neisseria and/or heterologous gene products from non-Neisserial sources. Such compositions are used in vaccine preparations for the treatment of microbial infection.