ABSTRACT
This chapter reviews the basic principles of retroviral vector design and production. Prospects and limits of retroviral vectors technology are also discussed and the main data obtained for gene transfer into bird embryos are briefly reported. The retroviral particle contains two positive-strand RNA genomes. There are two major origins of avian defective retroviral vectors. The first one is derived from the ALSV and the second from the Reticulo Endotheliosis Viruses. Packaging cells are designed to synthetize all retroviral proteins necessary for the production of infectious particles. Defective avian retroviral vector technology presents two main interests. The first concerns somatic or germinal gene transfers in early bird embryos. A second interest of avian retroviral vector system concerns their use as models to determine the safety of retroviral mediated gene transfer. The major problem associated with the use of retroviral vectors is the generation of infectious viruses that can be indefinitely transmitted.
