Vaccine Trials for the Clinician: Prospects for Viral and Non-Viral Vectors.

Recent progress in tumor genetics, tumor biology, and tumor immunology has renewed interest in the development of tumor vaccines. Unlike the previous generation of vaccines that consisted of the patient's own tumor cells in some form, the new vaccines contain defined peptides or genes with a known function. In order to induce a potent and long-lasting cell-mediated antitumor response, viral as well as nonviral vectors have been explored as vehicles for gene delivery. Both types of vectors have shown encouraging results in animal models. However, because of the many possible vectors that have been designed, it may be too early to say which type of vector is most efficient in the human. Clearly viral vectors have a higher transduction efficiency than most nonviral delivery systems. A drawback is that viral vectors may be toxic or immunogenic. Current research focuses on enhancing the targeting and specificity of both viral and nonviral vectors and control of transgene expression levels. Clinical studies using a variety of both viral and nonviral vectors have begun, and the results are forthcoming.