The present invention concerns the use of methods and compositions to prophylactically or therapeutically vaccinate a subject against a pathogen or disease. Embodiments of the invention include the production of an attenuated bacterium from the family Enterobacteriaceae with a non-functional lipoprotein for use as a vaccine or as a vaccine vector for delivering antigens to a subject to be vaccinated. In certain embodiments, a bacterium of the Enterobacteriaceae family lacking a wild type LP, for example Salmonella typhimurium lacking a wild type LP, may be produced and used as a vaccine or vaccine vector.