Cytotoxic T-Lymphocyte-,and Helper T-Lymphocyte-Oriented DNA Vaccination

DNA vaccines have advantages over other types of vaccines in that they can induce strong cellular immune responses, namely cytotoxic T lymphocytes (CTL) and helper T lymphocytes (Th). DNA vaccines are therefore considered a promising alternative to attenuated live vaccines in the field of infectious diseases. So far, various DNA vaccines have been generated and tried to induce a particular cellular immune response by virtue of recombinant DNA technology. DNA vaccines have been designed for efficient transcription and translation of target genes by a variety of strategies. Also, various DNA vaccine strategies for induction of specific CTL and Th have been reported by taking into consideration antigen presentation pathways and the strategies have been shown to be effective to elicit particular T-cell responses. In this paper, we have reviewed these strategies, including our study on epitope-specific T-cell induction by DNA vaccination against Listeria monocytogenes infection. From this review, it has been surmised that, to induce strong immune responses by DNA vaccines, the immunization route and the immunization regimen, such as heterologous "prime-boost" regimen, should also be considered.