The research performed in the Paterson laboratory was dedicated to harnessing the immune system to provide cures for, or protection against, neoplastic and infectious disease. There have been enormous advances made in the last few years in our understanding of the molecular and cellular machinery that renders proteins immunogenic. In our laboratory, we applied this knowledge to the development of strategies to enhance the immune response in the design of more effective vaccines against viral diseases, such as HIV, and against tumor cells. To do this we used a facultative intracellular bacterium, Listeria monocytogenes, which has the unusual ability to live and grow in the cytoplasm of the cell. Our laboratory was the first to show that this bacterium could be used to target antigens to the MHC class I pathway for antigen processing with the induction of cytotoxic T cells and has pioneered the application of this organism in vaccine development over the past 15 years. We have shown that recombinant forms of this organism which have been transformed to express viral antigens from influenza, HIV and SIV are excellent vectors for inducing cell mediated immune responses both parenterally and at mucosal surfaces. We have also applied this technology in the development of cancer vaccines that result in the induction of potent cell mediated immunity that can eliminate established macroscopic tumors even in the face of profound immune tolerance to the tumor-associated antigen. In other studies, we have discovered that fusing an antigen to some bacterial proteins enhances its immunogenicity. This finding opens up novel, and perhaps safer, avenues to cancer immunotherapy. Cancers to which we have directed our various technologies currently include cervical cancer, breast cancer, lung cancer, melanoma and lymphoma.