Nonviral DNA vectors for immunization and therapy:: design and methods for their obtention

The use of plasmid DNA for vaccination therapy is a relatively novel technology, with and limitations as with other gene transfer techniques. The technology is based on DNA vectors designed administering genes coding for relevant proteins into given organism, fulfilling requirements of the agencies that once properly formulated and delivered desired vaccine/therapeutic effect can be achieved. Starting from conventional plasmid DNA vectors tested in clinical trials, improvement resulted in bacterial element-less vectors, increasing the complexity of developmental process. The present review focuses systems described for generating these nonviral vectors for immunization and therapy from bacterial hosts (conventional and conditionally replicating plasmids, nonreplicating minicircles, and linear expression cassettes) in vivo or in vitro. Additionally, nontherapeutic genetic sequences with a negative or positive effect according to the specific application are described, bringing a better comprehension of the technology's state of the art.