ABSTRACT
This chapter reviews the development of retroviral vectors, as well as some of the problems associated with their use and how these problems are currently being tackled. The DNA form of the retroviral genome must then integrate into the genome of the infected cell for the retroviral life cycle to proceed. The possibility that a similar mechanism may cause malignancies in patients treated with retroviral vectors carrying therapeutic genes intended to treat other preexisting medical conditions, has posed a recurring ethical problem. Silencing of expression or interference between promoters in retroviral vectors may be avoided by modifying or replacing the retroviral promoter. Retroviral vectors that are replication-competent may have to be used with this approach, particularly if the cells of a multicellular organ or dense tumour mass are to be targeted or if very high virus titres are required.
